Medical Terminology and Anatomical Language Notes PDF

UNIT 2 Medical Terminology and Anatomical Language Medical terms are typically formed from one or more words, including roots or stems that provide the core meaning, combining vowels that join the roots, and prefixes or suffixes that modify the core meaning 06:11. Roots or stems provide the core meaning of a word, such as "cardi" meaning heart, and combining vowels are often used to join roots, making the word easier to pronounce 06:13. Prefixes can modify the core meaning of a word, such as "epi" meaning above, "hypo" meaning below, and "endo" meaning within, providing clues to the location of a structure in the body 06:55. Suffixes can also modify the core meaning of a word, such as the difference between "microscope" and "microscopic" 07:42. Accurate spelling is crucial in anatomy, as small differences in spelling can result in referring to completely different parts of the body 08:01. Examples of words with different meanings due to spelling differences include "ileum" (part of the small intestine) and "ilium" (part of the pelvis) 08:26. Familiarizing oneself with prefixes, suffixes, and root words is essential, as they have meaning and organization, and are not just complicated words; examples include "uni" meaning one, "try" meaning three, and "Brady" meaning long and slow 09:36. Understanding directional terms is crucial, as they provide standardization in anatomical language, allowing healthcare professionals to communicate effectively and accurately about patient care, regardless of the patient's position or movement 10:37. Anatomical language is important for standardization, enabling healthcare professionals to understand each other's reports and communicate effectively about patient care, tests, locations of injuries, and surgical procedures 10:49. Practicing and becoming familiar with anatomical terms is necessary, as anatomy is not difficult in terms of content, but rather in terms of volume and detail, with layers of information building on top of each other 11:42. Mastering anatomical terms is essential for understanding how body parts move and function, and for identifying structures, which requires recall and frequent review of bite-sized chunks of information 12:52. Anatomical position is the starting point for describing locations, movements, and relationships in the body, with the person standing upright, feet slightly spread apart, palms facing forward (anterior), and eyes at eye level 13:10. When describing the location of structures in the body, it's essential to use proper terms that make sense regardless of the person's position, such as anterior, posterior, superior, inferior, medial, and lateral, to avoid confusion 14:08. The anatomical position is used as a reference point, where the person is standing upright with feet flat on the floor and facing forward 14:53. When describing the trunk or thorax, superior and inferior are used to describe structures, with superior being closer to the top and inferior being closer to the bottom 15:16. Medial and lateral are used to describe structures in relation to the midline of the body, with medial being closer to the middle and lateral being further away 15:39. These terms can also be applied to the appendages, such as the arms and legs, to describe their orientation 16:42. When describing the upper and lower limbs, proximal and distal are used instead of superior and inferior, with proximal being closer to the attachment to the trunk and distal being further away 16:58. Understanding these terms is crucial for accurately describing the location of structures in the body and for interpreting medical images such as MRIs and CT scans 18:18. Planes, such as anterior, posterior, sagittal, and cross-sectional, are also important for understanding the orientation of medical images and for comparing normal and abnormal structures 18:00. Sagittal planes are vertical lines that divide the body into right and left halves, with a mid-sagittal plane cutting the person evenly into right and left, while a parasagittal plane divides the body unevenly 19:06. A frontal or coronal plane divides the body into front (anterior) and back (posterior) portions 19:37. Transversal or horizontal planes cut across the body, dividing it into upper (superior) and lower (inferior) portions 19:59. When analyzing a view, it's essential to take a pause and determine the level, slicing direction, and nearby organs, often using the spine as a landmark to orient oneself 20:50. Familiarity with directional terms, such as anterior, posterior, superior, and inferior, is crucial, and a chart in the textbook can be used for reference 21:23. Ventral and dorsal terms are less commonly used in this course, as they are more relevant to four-legged creatures, but it's essential to know that anterior is consistent with ventral and dorsal is consistent with posterior 21:35. Other directional terms include cephalic (towards the head or superior part), caudal (towards the inferior part), ipsilateral (on the same side of the body), and contralateral (on the opposite side of the body) 22:08. Superficial and deep terms are also relevant, with the skin being superficial to muscles and bones being deep to muscles 22:44. Practicing the use of these directional terms with friends, colleagues, or family can help reinforce understanding and improve description of body parts 23:25. Practicing with someone, even a pet, can be helpful, and if not, practice quizzes can be used as an alternative 23:42. Body Regions and Cavities The body can be divided into regions, including anterior and posterior views, with the axial region consisting of the head, neck (cervical), and trunk 23:57. The trunk is further divided into the thorax (chest portion) and abdominal region, with the diaphragm being a major landmark that separates these two regions 24:13. The diaphragm is a D-shaped muscle that travels posteriorly to the spine and is functionally important 24:39. The appendicular skeleton includes the upper and lower limbs, with the shoulder girdle (clavicle and scapula) connecting the arms to the trunk, and the hip girdle (pelvis) connecting the lower limb bones 25:12. The abdominal area can be divided into quadrants to help with diagnostic possibilities, with the right lower quadrant being a common location for the appendix 26:04. The upper limbs include the brachial (arm), carpal (wrist), and forearm regions, while the lower limbs include the femoral (thigh), leg, and tarsal (ankle) regions 27:07. The nine regions of the body are more commonly used in anatomy, especially in dissections and advanced studies 28:12. The internal anatomy of the body can be divided into different cavities and classifications, which are important to understand for both dissection and clinical purposes 28:27. The body has numerous cavities that are lined with membranes and contain internal organs, also known as viscera 28:56. The thoracic cavity is divided by a mediastinum and contains the heart, major vessels, and the thymus gland 29:09. The cranial cavity is formed by the skull and contains the brain, while the vertebral canal contains the spinal cord 29:30. The thoracic cavity is located between the first rib and the diaphragm, with the sternum as its anterior border and the vertebral column as its posterior border 29:42. The mediastinum is a smaller cavity within the thoracic cavity that contains the heart and major vessels 29:59. The abdominal pelvic cavity is divided into the superior abdominal cavity, which contains digestive organs, and the inferior pelvic cavity, which contains the bladder, rectum, and reproductive organs 30:36. The diaphragm separates the thoracic cavity from the abdominal pelvic cavity and is a key landmark 31:05. Each membrane is lined with a thin, two-layered serous membrane that secretes a lubricating film of moisture 31:13. The lungs are surrounded by pleural membranes, with a visceral pleura covering the lung itself and a parietal pleura covering the rib cage 31:24. The pleural fluid is a lubricating fluid that helps reduce friction between the lungs and the rib cage 32:08. The abdominal pelvic cavity is also lined with a two-layered serous membrane, known as the peritoneum, which suspends and covers the organs in the area 32:20. The visceral peritoneum covers the organs directly, while the parietal peritoneum covers the inner cavity wall 32:36. Histology: Tissues and Their Functions Histology is the study of tissues and how they are arranged into organs, with the word "histology" making sense as "histo" means tissue 33:15. The study of tissues will cover epithelial cells, connective tissue, and then nervous and muscular tissue, with the underlying pattern being that the structure or design of anything in the body makes sense towards its function 33:30. Different cells in the body are specialized and differentiated for different purposes, with characteristics based on their function, such as shape, organelles, and size 34:12. Four main categories of tissues exist: epithelial tissue, connective tissue, nervous tissue, and muscle tissue, each with distinct organization and specialization for certain tasks 34:44. Nervous tissue is specialized to send signals, with a design that makes sense for its function, such as being organized in a straight line to efficiently send information from point A to point B 34:51. The design of tissues and cells makes sense when considering their function, such as a red blood cell being designed to carry oxygen with features like a flat, concave disc shape that increases surface area for gas exchange 37:01. The body is designed efficiently, with organs and tissues often located close together or connected by vessels or ducts when they work together or share a purpose 35:49. Understanding the features and organization of tissues and cells provides clues about their function in the body 36:19. Red blood cells are specialized to carry oxygen and do not have organelles or a nucleus, which allows them to have more room to carry oxygen 37:56. The diameter of a red blood cell is microscopic but still fits through the tiniest vessels in the body, which are the capillaries 38:20. Red blood cells can travel through all the vessels in the body, including the capillaries, which are the exchange vessels 38:30. It is essential to think critically and analyze information when studying, rather than just memorizing it, to gain a deeper understanding of the subject 38:42. Tissues are groups of similar cells that work together to perform a specific role in an organ, and they can differ in the types and functions of their cells but have an overall purpose to work closely together 39:17. There are four primary tissue types, including epithelial tissue, which is characterized by closely packed cells arranged in an orderly fashion 39:43. Epithelial tissue has various functions, including protection, secretion, and absorption, and it can be found covering organ surfaces, forming glands, and acting as a barrier 40:16. Connective tissue is one of the most abundant and widely spread tissues in the body, and it comes in different forms, including supporting tissues that bind things together and protect organs 41:12. Connective tissue has widely spaced cells and a visible cell matrix behind it, which is made of fibrous proteins and a clear gel called ground substance 41:19. Connective tissue can be in various forms, including liquid, semisolid, gel, rubbery, firm, and rigid, with examples being blood, cartilage, and bone, and its characteristic is dictated by the ground substance 42:10. Nervous tissue and muscle tissue are excitable, meaning they can be stimulated by action potentials to send nerve impulses and create a response 42:44. Nervous tissue has excitable cells specialized to transmit information to other cells, found in the brain, spinal cord, and nerves 43:10. Muscle tissue is also excitable, consisting of elongated muscle cells called muscle fibers that are specialized to contract, with this contractile feature unique to muscle tissue 43:24. When a muscle is "fired," it shortens, generating force, and ultimately causing movement, with skeletal muscles attached to bones 43:52. There are three types of muscle in the body: skeletal muscles, which are voluntarily controlled and attached to bones; cardiac muscle, which makes up the bulk of the heart; and smooth muscle, which is found in blood vessels and hollow organs and is under involuntary control 44:14. Smooth muscle is found in blood vessels, hollow tubes, and hollow organs, and is controlled by the nervous system, allowing for involuntary actions such as dilation of blood vessels 44:47. Epithelial Tissue Epithelial tissue is tightly packed with cells and has a basement membrane that acts as an anchor, strengthening the attachment point, and also acts as a barrier to pathogens and other cells 45:25. The basement membrane is also important for immunity, helping to block entry of pathogens and other cells, and is found in epithelial tissue throughout the body 46:14. Tissue sections are prepared using a fixative to hold the sample together, sectioning the tissue, and sometimes adding stain to make certain features more visible 46:41. When taking a section, the method of sectioning is indicated, such as longitudinal, cross or transverse, or oblique sections, to provide orientation 47:21. Epithelial tissue is a protective layer that covers body surfaces, lines body cavities, and forms the linings of glands, with features that help protect the skin 48:24. Epithelial tissue is closely packed, covers body surfaces, and is the top layer, even if it's not always on the outside of the body 48:48. This tissue has various functions, including sensation, absorption, filtration, secretion, and protection, forming a physical barrier to prevent entry into the body 49:19. Epithelial tissue is avascular, meaning it has no blood supply, but it always has a piggyback arrangement with a layer that is nourished by blood, such as the dermis in skin 49:51. The basement membrane is a unique feature of epithelial tissue, and skin has a capacity for mitosis, allowing it to regenerate, unlike some other types of tissue 50:31. Epithelial cells are arranged in layers, with the deepest layer having the capacity for mitosis, allowing the tissue to regenerate 51:34. The skin has a unique protective feature where epithelial cells actively divide and push out from deep down to the surface, replacing lost cells due to friction, abrasion, or exposure to chemicals 51:47. Skin can be classified in two ways: by the layers present and by the cell types present, and the names of the tissues make sense when understood in an organized way 52:23. The layers of skin can be simple, pseudostratified, or stratified, with simple epithelia being a single layer, stratified having multiple layers, and pseudostratified appearing to have multiple layers but actually being a single layer 53:02. Simple epithelia are not designed for protection and abrasion, but rather for rapid diffusion, absorption, and secretion, and are found in areas such as the lungs, heart, and blood vessels 54:05. Squamous cells are flat and thin, and simple squamous epithelium is found in areas where rapid diffusion and transport of substances occur, such as the lungs and lining of the heart and blood vessels 54:44. Cuboidal cells are square-shaped and found in areas where absorption and secretion occur, such as the stomach and gut, and may have microvilli or a brush border to increase surface area 55:45. Microvilli are tiny hair-like projections that increase the surface area of a space and are typically found in areas where absorption occurs, such as the gut 56:04. Simple cuboidal epithelium is found in the liver, salivary glands, bronchials of the lungs, and kidney tubules, and is characterized by cube-shaped cells that provide more surface area for absorption 56:37. Simple columnar epithelium is found in the GI tract, kidney, and uterine tubes, and is characterized by tall, narrow cells that are sometimes ciliated or have microvilli, and often have goblet cells that secrete mucus 56:47. Ciliated pseudostratified columnar epithelium is a type of epithelium that appears to be multilayered but is actually a single layer of columnar cells with cilia that move particles along their surface 57:41. Cilia are hair-like projections that move particles along their surface, and are found in the respiratory tract, uterine tubes, and other areas of the body 58:08. Smoking can paralyze cilia, making it harder for the body to remove unwanted particles, and can lead to a chronic cough 58:50. Goblet cells secrete mucus, which helps to protect the body from acid and other irritants, and are found in the respiratory tract, stomach, gut, gallbladder, uterus, and male urethra 59:14. Keratinized tissue is found on the skin's surface and provides protection against the environment, and is characterized by the presence of keratin, a tough fibrous protein 59:49. Keratin is a protective protein that is filled with lamellar granules, which have a water-repellent glycolipid, and is found in the outer layers of the skin 01:01:08. The outer layers of the skin are made up of dead cells that are filled with keratin and are gradually replaced by new cells from the basal layer 01:00:57. The epidermis contains a protein called keratin that resists abrasion and helps prevent water loss through the skin, with an extra layer of cells in areas such as the soles of the feet and palms 01:01:34. Keratinized cells are essentially dead cells filled with granules, making them more resistant to stress, while non-keratinized cells still resist abrasion and block the entry of pathogens due to tightly packed cells 01:02:03. Stratified squamous epithelium is the most common type of epithelium in the body, consisting of multi-layered thin squamous cells that can be either keratinized or non-keratinized 01:02:35. Stratified cuboidal epithelium is a rare type of epithelium, consisting of two or more layers of cuboidal cells, found in areas where two other epithelial types meet, such as the anal canal and male urethra 01:03:02. Stratified cuboidal epithelium contributes to sweat secretion, ovarian hormone release, and sperm production, particularly in the seminiferous tubules of the testes 01:03:21. Connective Tissue Connective tissue is the most abundant and widely distributed type of tissue in the body, characterized by a matrix with less cells and variable cell types 01:04:03. Connective tissue connects, protects, and binds organs together, with varying levels of vascularity, such as loose connective tissue with a lot of blood supply and cartilage with little to no blood supply 01:04:30. Tendons and ligaments are types of connective tissue, with collagen fibers arranged in parallel bundles, and it's essential to know the difference between them, as ligaments connect bones to each other, while tendons connect muscles to bones 01:05:17. The correct terminology for a partial tear in a ligament is a sprain, while a partial tear in a muscle or tendon is called a strain 01:06:00. A full tear of a tendon or ligament is a serious injury that requires surgery, as tendons connect muscles to bones and need to be reattached 01:06:23. Tendons are stronger than muscles and can withstand more force without tearing off the bone, which is why we have them instead of just muscle and bone 01:06:43. Connective tissue supports the body and provides physical protection, such as the skull protecting the brain, ribs and sternum protecting the heart and lungs, and the pelvis shielding the urinary bladder and reproductive organs 01:07:02. Connective tissue also plays an immune role, with white blood cells like macrophages performing phagocytosis to engulf and degrade foreign particles 01:07:37. Macrophages are a type of white blood cell that can be fixed in tissue or circulate through the body, performing surveillance and attacking foreign invaders 01:08:05. Connective tissue acts in movement, storage, and transport, with fat in connective tissue serving as an energy reserve and storing calcium and phosphorus in bones 01:08:16. Connective tissue is the most widely distributed and variable tissue in the body, with diverse types such as fibrous tissue, adipose tissue, cartilage, and bone 01:08:41. Mature connective tissue falls into one of four groups: fibrous connective tissue, adipose tissue, cartilage, and bone, which are either supportive or fluid connective tissue 01:09:25. Connective tissue can be classified as loose or dense, depending on the arrangement of the cells and ground substance, with loose connective tissue having a gel-like ground substance and dense connective tissue having fibers that occupy more space than the cells or ground substance 01:09:49. Adipose tissue is an example of connective tissue, with adipocytes as the dominant cell type, and is the body's primary energy reserve, providing thermal insulation 01:10:28. There are different types of fat in the body, including white fat, which cushions organs, and brown fat, a heat-generating tissue found in infants and children, with the color coming from blood vessels and mitochondria 01:11:01. Cartilage is a relatively stiff but flexible, rubbery matrix, with different types found in the body, including hyaline, elastic, and fibrocartilage 01:11:20. Cartilage is formed from chondroblasts, immature cartilage-forming cells that secrete a matrix and become surrounded by it, eventually becoming mature chondrocytes with no blood vessels, resulting in slow healing 01:11:57. Hyaline cartilage is clear or glassy in appearance, easing joint movement and reducing friction, typically found in the ends of bones in articulations 01:12:21. Elastic cartilage contains elastic fibers that can distend significantly but recoil to their original size without damage, found in the outer ear and epiglottis 01:13:01. Fibrocartilage has larger, coarser fibers that bind things together, allowing little to no movement, found in the meniscus of the knee, intervertebral discs, and pubic symphysis 01:13:51. Fibrocartilage in the pubic symphysis allows for some movement, which is important for pregnancy, as pregnancy hormones cause the fibrocartilage disc to allow even more movement and laxity at the joint 01:14:27. Fibrocartilage is also found in the attachment of the ribs to the sternum, allowing for movement and expansion of the lungs during breathing 01:15:10. Bone is a hard, calcified connective tissue, with the bones of the skeleton being organs made of bone tissue 01:15:43. The human body contains various tissue types, including bone tissue, cartilage, bone marrow, and others, with two main types of bone tissue: compact bone and spongy bone 01:15:53. Compact bone, also known as cortical bone, makes up 85% of the skeleton and is strong and solid, but also heavy, which would compromise movement if all bones were made of it 01:16:13. Spongy bone, also known as cancellous bone, makes up 15% of the skeleton and is found inside long bones, making them lighter and allowing for movement 01:17:01. In babies, spongy bone is filled with red bone marrow, which is significant for producing new blood cells through the process of hematopoiesis 01:17:23. In adults, some bones lose the capacity to produce red bone marrow and are filled with yellow marrow, which is more fat and serves as an energy reserve, but some red bone marrow is retained in the ends of long bones and behind certain flat bones 01:17:39. The arrangement of spongy bone is made up of delicate struts called trabeculae, which are layers that make up the cancellous bone 01:18:13. The compact bone on the outside protects the delicate spongy bone inside, which is a common design pattern in the body to protect vital tissues 01:18:42. Compact bone is dense and calcified with no visible spaces, and its cells surround vertically oriented blood vessels in a circular arrangement 01:19:22. The blood vessels and nerves travel through the central canal, and the bone matrix is deposited in concentric lamellae, resembling the rings of a tree trunk 01:19:51. Compact bone is found anywhere physical support is needed, protecting organs and viscera, and serving as a reserve for calcium and phosphorus 01:20:13. Blood and Nervous/Muscular Tissue Normal blood volume is composed of 50-60% plasma, which is mainly water with dissolved proteins, clotting factors, hormones, and carbon dioxide, 45-55% red blood cells, and 1% white blood cells and thrombocytes 01:20:33. When blood is spun in a centrifuge, it separates into three distinct layers: plasma, white blood cells and thrombocytes, and red blood cells 01:20:38. Nervous and muscular tissue are both excitable, meaning they have a membrane potential that allows electrical charges to spread across the tissue due to a stimulus, resulting in a response 01:21:35. Nervous tissue is specialized for communication using electrical and chemical signals, and its main cell types are neurons and neuroglia 01:22:20. Neurons are nerve cells that respond and transmit information to other cells, while neuroglia are support cells that do not transmit information 01:22:33. Muscle tissue is arranged with elongated cells that are specialized to contract when stimulated, allowing for movement, digestion, elimination of waste, breathing, speech, blood circulation, and body heat generation 01:23:32. There are three types of muscle tissue: skeletal, cardiac, and visceral, each with distinct characteristics, such as striation, branching, and the presence of intercalated discs 01:24:10. Skeletal muscle is voluntary, attaches to bones, and has a striated appearance under a microscope 01:24:14. Cardiac muscle is involuntary, found only in the heart, and has branched, shorter fibers with intercalated discs Visceral muscle is involuntary, found in the hollow walls of organs, and has a smooth appearance without striations UNIT 3 Circulatory System and Blood The fundamental purpose of the circulatory system is to transport materials, including lipids, throughout the body, with blood serving as the liquid medium 02:07. Blood is a liquid form of connective tissue, with its consistency determined by the ground substance 02:25. Hematology is the study of blood, and the functions of the circulatory system include transporting substances such as oxygen, waste, and nutrients, as well as hormones and heat 03:07. The circulatory system plays a crucial role in maintaining homeostasis by regulating and controlling various systems and processes in the body 04:07. The body's systems, including the circulatory system and blood, work together to regulate several life processes, such as maintaining pH and body temperature, to ensure survival within strict parameters 04:18. Homeostasis is a dynamic condition that involves constantly challenging and regulating processes, such as fluid volume inside cells and ion composition, to maintain balance 04:54. The circulatory system helps protect the body through blood clotting, fighting toxins and microbes, and white blood cells, such as phagocytic cells that engulf foreign particles 05:33. Blood has physical characteristics, including being more viscous than water, having a slightly alkaline pH of 7.35-7.45, and an average volume that is slightly higher in males than females 07:06. Blood Composition and Characteristics Whole blood is composed of plasma, which is the fluid portion that dissolves solutes and formed elements, and formed elements, which include blood cells and cell fragments 07:37. Plasma contains a mixture of water, proteins, nutrients, electrolytes, nitrogenous wastes, hormones, and gases, including dissolved carbon dioxide, oxygen, and nitrogen 08:28. Nitrogenous compounds in plasma come from free amino acids broken down from dietary protein, and other components include glucose, vitamins, fats, cholesterol, phospholipids, and minerals 08:41. Electrolytes, particularly sodium, contribute to the positively charged ions in plasma 09:02. Serum is similar to plasma but with the solids, including fibrinogen, removed, resulting in an absence of fibrinogen in serum 09:21. Plasma proteins, such as albumin, play a role in defense, clotting, and transport, and their functions will be discussed further in subsequent courses 09:42. Shock and Blood Counts When a person goes into shock, they are not getting enough oxygen and nutrients to meet the metabolic demands of their tissues and cells, often due to inadequate blood flow to the body tissues 10:32. Inadequate blood flow can cause cells to switch to anaerobic production, impairing cell function, and if not reversed, can lead to cell and organ damage, and even be fatal 11:01. Hematocrit is the ratio of red blood cells to the total volume of blood, used as an indicator to determine what's happening with a patient 11:39. A normal complete blood count can use the RBC count and concentration of hemoglobin as lab values to determine the amount of oxygen that the blood can carry 11:54. Red blood cells make up 99% of the cells in the blood, while white blood cells make up less than 1%, and platelets are made from cell fragments 12:36. There are different types of white blood cells, including neutrophils, lymphocytes, monocytes, basophils, and eosinophils 12:49. Red Blood Cells The structure or design of a cell is always efficient and related to its function or role in the body 13:29. Red blood cells have a specific shape and structure that is efficient for their function, and understanding this can help in understanding their role in the body 13:41. Epithelial tissue provides protection by forming a barrier, and its structure is crucial for its function, such as the epithelial layer of the skin, which would be inefficient in protection if the cells were widely spaced 14:02. Red blood cells and platelets lack certain formed elements, such as a nucleus, mitochondria, and DNA, which allows them to carry more oxygen 14:57. The shape of red blood cells, a biconcave disk, enhances their surface area for gas exchange, allowing them to perform more gas exchange 15:31. Red blood cells have a high surface area to volume ratio, which enables them to carry more oxygen, and they are specialized for their particular role 16:09. Red blood cells cannot undergo mitosis or extensive metabolic activities and last in the bloodstream for 120 days before being replaced through apoptosis 16:24. Red blood cells get their red color from hemoglobin, which carries oxygen and consists of four protein chains called globins, each conjugated with a heme group that binds oxygen to an iron atom 16:53. Each hemoglobin molecule can transport up to four oxygen molecules, as each heme can carry one molecule of oxygen 17:27. Polycythemia and Anemia An imbalance between the rates of red blood cell formation and destruction can lead to an excess or deficiency in red blood cells, resulting in conditions such as polycythemia 17:56. Polycythemia is characterized by an excess of red blood cells, leading to increased blood volume, blood pressure, and blood viscosity 18:20. In primary polycythemia, blood volume can double, overwhelming the circulatory system, and increasing the risk of clotting or stasis, with blood viscosity being two or three times the normal value, leading to poor circulation and clogged capillaries 18:47. Long-term risks of primary polycythemia include the formation of a thrombus, or clot, which can lead to an embolism if it detaches and travels through the bloodstream 19:04. Anemia is a condition characterized by a deficiency in red blood cells or hemoglobin, with different types of anemia caused by various factors, such as the body not producing enough red blood cells, or prolonged bleeding 19:25. Patients with kidney failure are at risk of anemia due to the kidneys' role in secreting erythropoietin, which stimulates red blood cell production 19:40. Untreated anemia can lead to tissues not receiving enough oxygen, causing symptoms such as paleness, lethargy, and dizziness, and is common during the third trimester of pregnancy due to increased fetal blood demands 20:13. Anemia can also cause reduced blood osmolarity, leading to swelling, or edema, and decreased blood viscosity, resulting in lower blood pressure and a faster heart rate 20:41. Hemopoiesis and White Blood Cells Hemopoiesis is the formation of blood cells from hemopoietic stem cells, controlled by hormones and occurring in the red bone marrow 21:07. Hemopoietic stem cells give rise to two types of stem cells: myeloid and lymphoid, which differentiate into various types of blood cells, including red blood cells, platelets, and white blood cells 21:19. Myeloid stem cells differentiate into precursor cells called blasts, which develop into red blood cells, platelets, granulocytes, and monocytes 21:54. Lymphoid stem cells differentiate into lymphoblasts, which become B lymphocytes or T lymphocytes, with some completing development in lymphatic tissue 22:21. White blood cells, or leukocytes, are the least abundant formed elements, making up only 1% of blood cells, but are easily recognizable due to their conspicuous nuclei and retained organelles 22:51. White blood cells, also known as leukocytes, have a short lifespan in the bloodstream, typically only a few hours, which is reflected in their low numbers 23:25. There are two main types of white blood cells: granulocytes and agranulocytes, with granulocytes being further divided into three types: neutrophils, eosinophils, and basophils 23:35. Agranulocytes lack specific granules and include monocytes and lymphocytes, with lymphocytes being the most numerous 24:18. Monocytes begin as monocytes and then differentiate into macrophages, which perform phagocytosis, or cell eating 24:41. White Blood Cell Counts and Disorders The information about white blood cells is relevant because it can provide insights into disorders and diseases, such as infections, inflammation, and cancer 25:41. A low white blood cell count is known as leukopenia, which can be caused by metal poisonings, radiation sickness, and certain infectious diseases 26:04. A high white blood cell count indicates that the body is fighting something off, but it is not specific enough to determine if it is an infection or inflammation 26:25. A differential white blood cell count provides more detailed information about the different types of white blood cells and their counts, which can help in diagnosing specific conditions 27:52. A low white blood cell count can make a person more immunocompromised, and it is essential to determine the underlying cause of the low count 27:08. Leukocytosis is a high white blood cell count, which can be caused by allergies, infections, or other conditions that trigger an immune response 27:35. Complete Blood Count (CBC) A complete blood count (CBC) is a routine test that provides a profile on multiple blood values, including the number of red blood cells, white blood cells, platelets, and the relative numbers of white blood cells, as well as the hematocrit, size, and morphology of red blood cells 28:21. A CBC can detect a magnitude of infections, rule out various diseases and injuries, and determine if a person is healthy, providing clues for further diagnostic imaging or blood labs 29:41. Leukemia can be detected through a CBC, which would show abnormally high numbers of circulating white blood cells 29:14. Platelets and Hemostasis Platelets are small fragments of bone marrow cells, also known as megakaryocytes, which are important for hemostasis, the cessation of bleeding 30:36. Platelets play a crucial role in stopping blood loss and damage to vessels by forming a platelet plug and releasing chemicals that promote blood clotting 31:29. Platelets have a short lifespan of 5 to 9 days and are removed by macrophages in the spleen and liver 31:38. The relative percentages of red blood cells, white blood cells, plasma, and formed elements are important to know, but not the exact counts 32:08. Platelets stop potentially fatal leaks by inducing a vascular spasm, which is the first step in the three-step process of hemostasis 32:28. Vascular spasm is caused by the contraction of smooth muscle in blood vessels, which responds involuntarily to hormones and the nervous system 32:45. When a blood vessel is injured, smooth muscle spasms to constrict the vessel, narrowing its diameter and limiting bleeding, and a platelet plug forms to temporarily seal the break in the vessel 33:03. Platelets secrete constrictors to reduce blood loss, aggregate to form platelet plugs, secrete pro-coagulants or clotting factors, initiate formation of clot-dissolving enzymes, and chemically attract other blood cells to sites of inflammation 33:37. Platelets also fagocytose and destroy bacteria, and secrete growth factors that stimulate mitosis to repair blood vessels 34:13. Blood Production and Hematocrit The production of all formed elements of blood is called hemopoiesis, and the percentage of blood volume made up of red blood cells versus total volume is called hematocrit or packed cell volume 34:39. The overall sensation of bleeding, which involves several mechanisms, is called hemostasis, and an excessively high red blood cell count is called polycythemia, while a low red blood cell count is called anemia 35:03. The Heart: Location and Structure The heart is roughly the size of a person's fist, and it lies in a thick cavity called the mediastinum, located between the lungs, with its broad base at the superior end and its apex at the inferior end 35:58. The heart is tilted towards the left from the base to the apex, with more than half of it located to the left of the body's median plane or midline 36:57. The pericardium is a double-walled sac that encloses the heart, with two layers and fluid between them, and it has a fibrous layer and a serous layer 37:11. The outer layers of the heart tend to be more fibrous and tougher, while the inner layers are more delicate, with the serous layer turning inward at the base of the heart to form the visceral pericardium, which covers the heart itself 37:54. The paracardial cavity is the space inside the paracardial sac, filled with paracardial fluid that reduces friction and provides shock absorption, allowing the heart to beat and move without excessive contact with outer tissues 38:29. The paricardium isolates the heart from other thoracic organs, giving it room to expand while preventing excessive expansion 38:58. The epicardium, also known as the visceral pericardium, is the outer lining of the heart, covering the coronary blood vessels that travel through this layer 39:10. The endocardium is the inner lining of the heart, smooth and continuous with the valve surfaces and the endothelium of the blood vessels 39:29. The myocardium is the intermediate layer, the bulk of the heart muscle, with its thickness related to the amount of work each chamber does 39:41. The heart has four chambers: the right and left atria (upper chambers) and the right and left ventricles (lower chambers), with the interatrial septum separating the atria and the interventricular septum separating the ventricles 40:17. The atria have thin and flaccid walls, as their job is to take blood and deliver it to the ventricles below, which is not much work in terms of pumping and distance 40:48. The ventricles have thicker walls, with the right ventricle pumping blood to the lungs to pick up oxygen, and the left ventricle pumping oxygenated blood to the body tissues, requiring more force and pressure due to the greater distance 41:23. The left ventricle has the thickest walls, as it pumps blood to the entire body, requiring a greater force of contraction compared to the right ventricle 42:20. The left ventricle has a significantly thicker wall than the right ventricle, being two to four times as thick, which reflects its greater workload in pumping blood throughout the entire body 42:32. Pulmonary and Systemic Circuits The heart can be thought of as a double pump with two separate circuits: the pulmonary circuit, which takes blood to the lungs to pick up oxygen, and the systemic circuit, which pumps oxygenated blood to the cells and tissues in the body 43:16. The pulmonary circuit is located on the right side of the heart, while the systemic circuit is on the left side 43:24. The product of the pulmonary circuit is blood with oxygen and nutrients, which feeds the systemic circuit 43:57. Blood Flow Through the Heart The easiest way to learn the blood flow through the heart is by mapping it out, with the heart having four chambers: the right atrium, right ventricle, left atrium, and left ventricle 44:16. The atria are entry chambers where blood comes in and is delivered to the ventricles below, while the ventricles pump the blood 45:02. Blood only travels in one direction, from the right ventricle to the lungs and then to the left ventricle, and finally to the body 45:21. The right atrium is the starting point for the blood flow cycle, with three vessels coming into it: the inferior vena, superior vena, and coronary sinus 45:41. The superior vena cava drains blood from the head and above the heart, the inferior vena cava drains blood from below the heart, and the coronary sinus drains blood from the walls of the heart 46:02. The blood flow cycle goes from the right atrium to the right ventricle, then to the lungs, and finally to the left side of the heart 46:49. The left ventricle is the thickest chamber in the heart because it has to pump blood to the entire body, which requires the most work and has the biggest workload 47:04. Heart Valves The heart valves ensure one-way flow of blood through the heart, preventing backflow and mixing of oxygenated and deoxygenated blood 47:37. The valves open and close based on pressure changes caused by the contraction and relaxation of the heart muscle 47:57. There are two main types of valves in the heart: AV valves (between the atrium and ventricle) and semi-lunar valves (between the ventricle and the pulmonary trunk or aorta) 48:11. The AV valves include the tricuspid valve (between the right atrium and ventricle) and the mitral valve or bicuspid valve (between the left atrium and ventricle) 48:16. The tricuspid valve has three cusps or flaps, while the mitral valve has two cusps or flaps 48:30. The AV valves are connected to papillary muscles by chordae tendineae, which are ropey tendonous cords that control the opening and closing of the valves 48:57. The semi-lunar valves include the pulmonary valve (between the right ventricle and the pulmonary trunk) and the aortic valve (between the left ventricle and the aorta) 49:32. The semi-lunar valves have three cusps that are moon-shaped, and their opening and closing are dictated by pressure changes 50:18. Circulation Path and Oxygenation Blood flows through the chambers of the heart in the following order: right atrium, right AV valve (tricuspid valve), right ventricle, pulmonary valve, pulmonary trunk, lungs, left atrium, left AV valve (mitral valve), left ventricle, aortic valve, and aorta 50:50. The blood from the right and left pulmonary arteries goes to the lungs to unload carbon dioxide and pick up oxygen, then returns to the left side of the heart through the pulmonary veins 51:25. The blood enters the left atrium through the pulmonary veins, then passes through the left AV valve (also known as the mitral valve) into the left ventricle 51:49. From the left ventricle, the blood flows through the aortic valve into the ascending aorta, where it is distributed to every organ in the body to unload oxygen and pick up carbon dioxide 52:10. The cycle continues as the blood returns to the right atrium, and the process repeats 52:28. To effectively learn about the heart and blood circulation, it is recommended to use a diagram or model, as the process involves complex pathways and structures 52:40. The right atrium receives deoxygenated blood from the inferior vena cava, superior vena cava, and coronary sinus, but not from the pulmonary veins 53:14. The pulmonary veins, of which there are four, empty into the left atrium, bringing oxygenated blood from the lungs 53:35. Cardiac Muscle and Electrical System Cardiac muscle cells, or myocytes, are relatively short and thick, with branches that connect to several other cells, forming a network throughout the heart chambers 54:15. These cells have large mitochondria, indicating a high metabolic demand and need for energy and power 54:36. The heart is myogenic, meaning that the signal for contraction originates within the heart itself, and it has its own pacemaker and electrical system that allows the rhythm to spread through the heart 55:20. While the heart has its own autorhythmic system, its rate and blood pressure are tightly regulated by homeostasis to stay within certain parameters 55:51. The brain and nervous system have surveillance over the heart's auto-rhythmicity, ensuring it stays within normal parameters, and can respond by dilating or constricting vessels or releasing hormones to lower blood pressure or heart rate if necessary 55:58. The heart can establish its own heartbeat and spread it through the system, with features such as branches and interconnected cells reflecting this ability 56:41. Cardiac myocytes are joined end-to-end by intercalated discs, which have folds that interlock adjoining cells and increase the surface area 56:56. The heart also has mechanical junctions, including desmosomes and adherent junctions, which provide a mechanical linkage that strengthens the attachment between cardiac myocytes and prevents them from ripping apart when the heart beats 57:11. Gap Junctions are another type of connection that allows communication between cells by providing a tiny channel that connects the cytoplasm of one cell with the cytoplasm of the cell beside it 57:52. Gap Junctions allow for efficient communication and coordination between cardiac myocytes, enabling them to contract in unison and effectively pump blood 58:39. Cardiac Conduction System The cardiac conduction system has an inter Pacemaker and a nerve-like conduction pathway that allows the electrical signal to spread in a specific way, coordinating the heartbeat 59:20. The SA node is the pacemaker that initiates the heartbeat and determines the heart rate, and the signal spreads through the Atria, AV node, AV bundle, bundle branches, and Purkinje fibers to deliver the electrical signal to the heart 59:30. The cardiac conduction system includes all of the following except tendonous cords, which have nothing to do with the conduction system 01:01:00. The circulatory route from the aorta to the inferior and superior vena cava is part of the systemic circulation 01:01:17. Electrical signals pass quickly from one muscle cell to another through Gap Junctions in the intercalated disc 01:01:32. Blood in the heart chambers is separated from the myocardium by a thin membrane called the endocardium 01:01:46. Coronary Circulation The heart at any time doesn't hold most of the circulation, with only 5% of the entire blood volume being pumped through the heart itself 01:02:01. The myocardium has its own blood supply, with its own supply of arteries and capillaries that deliver blood to every muscle cell, known as the coronary circulation 01:02:23. The heart wall has its own supply, with the boundaries of the four chambers marked by three grooves largely filled with fat and the coronary blood vessels 01:02:46. The coronary sulcus, also known as the AV sulcus, is the groove that separates the atria and ventricles, while the interventricular sulci extend obliquely down the heart from the coronary sulcus towards the apex 01:03:01. The anterior interventricular sulcus is located on the front of the heart, and the posterior interventricular sulcus is located on the back, both overlaying the interventricular septum 01:03:31. The coronary circulation is supplied by the left side, with the left coronary artery dividing into two branches: the anterior interventricular branch and the circumflex branch 01:04:00. The anterior interventricular branch supplies both ventricles and the anterior two-thirds of the interventricular septum, while the circumflex branch supplies the left atrium and the posterior left ventricle 01:04:26. If the circumflex branch of the left coronary artery has a clot, the posterior wall of the left ventricle will be deprived of blood, become necrotic, and the heart's ability to pump blood to tissues will be impaired, resulting in less blood and oxygen being delivered to tissues, leading to impaired function 01:05:26. The circumflex branch also gives off a left marginal branch and ends at the back of the heart 01:06:02. The right coronary artery supplies the right atrium, the SA node, and gives off two branches: the right marginal branch, which supplies the lateral aspect of the right atrium and ventricle, and the posterior interventricular branch, which supplies the posterior walls of the ventricle 01:06:15. The coronary blood drains into the heart chambers, with 5 to 10% draining directly into the heart chambers, typically the right ventricle, and most coronary blood going back to the right atrium via the coronary sinus 01:06:55. The coronary sinus drains the walls of the heart and is the primary way it gets back to the right atrium, with three main inputs: the great cardiac vein, the middle cardiac vein, and the left marginal vein 01:07:34. The highlighted blood vessel in the images is the left coronary artery, which branches off the aorta and can be found between the pulmonary trunk and the left auricle 01:08:19. The arrow in the images points to the aortic semilunar valve, which is between the left ventricle and the aorta 01:08:38. Another image shows the tricuspid valve, which is between the right atrium and the right ventricle 01:09:04. The intercalated disc is a structure between cardiac muscle cells that contains mechanical and electrical junctions, including gap junctions and desmosomes 01:09:20. UNIT 4 Introduction to Blood Vessels To effectively study the content, it is essential to be organized and divide the material into smaller areas of the body, learning them in more manageable chunks 00:11. The blood vessels are categorized into three principal types: arteries, veins, and capillaries, each with distinct functions and characteristics 00:43. Arteries carry blood away from the heart and are known as resistance vessels due to their structure, while veins carry blood back to the heart and are capacitance vessels 00:48. Capillaries connect the smallest arteries to the smallest veins and are referred to as exchange vessels, playing a crucial role in the body 01:12. Structure of Blood Vessels The design of the body is efficient, and understanding the features of different vessels can help identify their locations and functions 01:31. The vessel wall consists of three layers, known as tunics: the internal tunic (tunica interna), the middle tunic (tunica media), and the external tunic 02:17. The tunica interna lines the blood vessel, is exposed to the blood, and is composed of simple squamous epithelium, which makes sense due to the lack of friction and physical stress 02:37. The tunica interna acts as a selective permeable barrier to materials entering or leaving the bloodstream and secretes chemicals that stimulate dilation or constriction of the vessel 03:16. The tunica media is usually the thickest layer, containing smooth muscle fibers and elastic tissue, allowing for the regulation of the vessel diameter through involuntary contraction 03:59. Vessels can either dilate or constrict due to sympathetic nervous system signals, and the middle layer of the vessel wall strengthens the vessels and regulates their diameter to prevent blood pressure from collapsing or rupturing them 04:25. The walls of veins have the same three layers as arteries but with less smooth muscle and connective tissue, making them thinner, which is acceptable due to lower pressure 05:00. Arteries have more elastic tissue than veins to handle high blood pressure, while veins do not need this due to lower pressure 05:28. Types of Arteries Arteries can be classified based on size, with large arteries called conducting arteries, medium-sized arteries called distributing arteries, and small arteries called resistance arteries 05:40. Conducting arteries are the largest and closest to the heart, with highly elastic walls to accommodate a big surge of blood, and are known as compliance vessels 05:48. Distributing arteries are medium-sized, more muscular, and distribute blood to specific organs, with lots of smooth muscle in the middle layer to allow for vasoconstriction and vasodilation 06:27. Resistance arteries are the smallest and deliver blood to capillaries, serving as a major point of control over blood flow to organs or tissues 07:02. Anastomoses and Collateral Circulation Anastomoses are backup routes for blood flow, forming an alternate route of blood flow to a body part through collateral circulation, and can be found in certain areas such as the gut and the Circle of Willis in the brain 07:37. The Circle of Willis is an arrangement of arteries in the brain that provides redundancies, allowing for more than one vessel to supply a certain area and ensuring that the brain is not without blood supply if one part of the circle becomes blocked 07:53. Capillaries and Capillary Beds Arteries supplying an area can constrict or narrow to maintain blood flow and function, and capillaries are unique exchange vessels that allow for the exchange of gases, nutrients, waste, and hormones between the blood and the fluid surrounding tissues 08:57. Capillaries have thin walls to facilitate easy diffusion of substances across them, and they are the primary site for exchange between the blood and tissues, with the other site being the venules 09:02. Capillaries connect the outflow from the heart, traveling through arterials, to the venules that return the blood to the heart, and they are part of a network called a capillary bed 09:54. A capillary bed is a network of 10 to 100 capillaries that allows for a lot of exchange to happen, and it is found in areas such as the lungs, gut, and other tissues that require rapid exchange of substances 10:19. Capillary beds give tissues the ability to auto-regulate, which is an important process in the body that allows for the automatic adjustment of blood flow to match metabolic demands 11:14. There are three types of capillaries: continuous, fenestrated, and discontinuous, which are distinguished from one another based on their permeability 11:24. Continuous capillaries are found in most tissues and have tight junctions that form a continuous tube, allowing small solutes to pass but limiting large molecules 11:34. Fenestrated capillaries have openings or windows that allow for rapid absorption or filtration and are found in organs such as the kidneys, endocrine glands, and small intestines 12:28. Sinusoids There are three types of blood vessels that can be differentiated based on their permeability, with sinusoids being the most permeable, allowing proteins and blood cells to pass through their large gaps 13:24. Sinusoids are found in organs such as the liver, bone marrow, and spleen, and play a crucial role in the exchange of substances between the bloodstream and these organs 14:03. Veins and Venules Veins are capacitance vessels with relatively thin walls that can expand easily to accommodate increased blood volume, and have a greater capacity for blood containment than arteries 14:10. Veins have thinner inner layers, including the tunica intima and tunica media, compared to arteries 14:30. At rest, 64% of the body's blood volume is found in systemic veins and venules, which act as a blood reservoir and can quickly divert blood to areas of increased activity or need 14:59. The distribution of blood volume in the body is as follows: 7% in the heart, 9% in the pulmonary circuit, 15% in arteries, 5% in capillaries, and 64% in the venous system 16:00. Small veins merge to form larger ones as they approach the heart, with the smaller ones referred to as tributaries 16:09. Post-capillary venules are the smallest veins and are more porous than capillaries, exchanging fluid with tissues and allowing white blood cells to immigrate through their walls 16:39. Muscular venules are slightly larger and receive blood from post-capillary venules, with smooth muscle in their middle layer 17:03. Medium veins have a thinner tunica media and externa, and most veins with individual names in the body fall into this category 17:25. Large veins have smooth muscle in all three layers, with examples including the inferior vena cava 17:45. The superior and inferior vena cava drain deoxygenated blood from the body into the right atrium, which then sends it to the lungs to pick up oxygen 17:47. Veins have valves that prevent backflow, but they are not true valves like those in the heart; instead, they are formed from the tunica interna and are flap-like cusps 18:16. Varicose veins occur when blood pools in the lower limbs due to gravity, causing the veins to stretch and the valves to become less effective, leading to backflow and swelling 18:41. Varicose veins are more prominent in superficial veins, which lack supportive tissue, and are also more common in people who stand for long periods, are obese, or are pregnant 18:57. The body uses two mechanisms to return blood to the heart: the skeletal muscle pump, which compresses veins and pushes blood through valves, and the respiratory pump, which creates pressure changes that cause blood to flow through veins towards the right atrium 20:17. Comparison of Arteries and Veins Blood vessels that can withstand high blood pressure, such as arteries, have an elastic tunic media and are adapted to handle high pressure, whereas veins are not 21:21. Arteries have thick walls with multiple layers, including an elastic tunic media, which allows them to withstand high blood pressure, whereas veins have thinner walls and are more prone to stretching and backflow 21:52. A muscular artery has a thick medial layer, whereas a medium vein is larger with less smooth muscle in the Tunica Media and a thicker Tunica Externa 22:17. Pulmonary Circuit The pulmonary circuit in the heart involves blood flowing through the pulmonary trunk to the pulmonary arteries, then into the lobar branches of each lobe, and finally returning to the heart through venules, veins, and the pulmonary veins 22:37. The right lung has three lobes, while the left lung has two lobes due to the space occupied by the heart, resulting in asymmetrical lungs 22:50. The superior, middle, and inferior lobar arteries supply the top, middle, and bottom of the lung, respectively, and have their own extensive blood supply 23:31. The purpose of the pulmonary circuit is to exchange carbon dioxide for oxygen, which occurs in the capillary beds surrounding the alveoli 24:05. A good practice is to trace the flow of a red blood cell from the right ventricle to the left atrium, naming all the vessels along the way 24:41. Systemic Vessels and Naming Conventions Systemic vessel names often describe their location, such as the axillary artery being located near the armpit and shoulder, or the brachial veins running along the arm 25:05. Some vessel names are derived from the organs they supply or drain, such as the hepatic artery and renal vein, while others are named after adjacent bones, like the temporal artery 25:25. Deep veins typically run parallel to arteries, and often, arteries run near nerves 26:00. Superficial veins tend to have more anastomoses and connections 26:17. When studying systemic vessels of the axial region, it is helpful to remember that the names often make sense and can be used to aid in understanding their locations and functions 26:37. To understand the blood supply to different parts of the body, it's helpful to visualize the structures nearby and identify each vessel, rather than just memorizing information 26:50. The Aorta and its Branches All systemic arteries arise from the aorta, which has three main areas: the ascending aorta, the arch of the aorta, and the descending aorta 27:24. The ascending aorta gives rise to the right and left coronary arteries, which supply blood to the heart 27:58. The arch of the aorta has three major arteries: the brachiocephalic trunk, the left common carotid artery, and the left subclavian artery 28:28. The right subclavian artery and the left subclavian artery supply blood to the shoulders and upper limbs 28:48. The right common carotid artery supplies blood to the right side of the head, and the left common carotid artery supplies blood to the left side of the head 29:00. The descending aorta turns into the thoracic aorta in the chest area and then becomes the abdominal aorta after passing through the diaphragm 29:16. Blood Supply to the Head and Neck The head and neck receive blood supply from four pairs of major arteries, including the common carotid arteries 29:49. The common carotid arteries pass up the front and side of the neck and are the main blood supply to the head and neck 30:25. The vertebral arteries arise from the right and left subclavian arteries and travel up the neck through the transverse foramina in the cervical spine 30:37. The vertebral arteries travel through a hole in the C6 to C1 vertebrae, providing blood to the brain and spine, and are accompanied by thyrocervical trunks, which are tiny arteries from the subclavian arteries that supply the thyroid gland and some scapular muscles 31:03. Costocervical trunks, which come from the subclavian arteries, supply the deep neck muscles and some of the intercostal muscles of the superior part of the rib cage 31:28. The common carotid arteries have the most extensive distribution in the head and neck arteries, branching into the external carotid artery and internal carotid artery near the laryngeal prominence 32:31. The external carotid artery supplies most of the external head structures, including the thyroid gland, tongue, skin and muscles of the face, back of the scalp, teeth, maxilla, oral cavity, external ear, and scalp 32:54. The internal carotid artery supplies important structures inside the skull, which will be discussed later 33:59. The Vertebral and Basilar Arteries The vertebral arteries converge and meet to form the basilar artery, which runs along the anterior portion of the brain stem and supplies major areas of the brain, including the cerebellum, pons, and inner ear 34:40. The basilar artery is part of the Circle of Willis, also known as the cerebral arterial circle, which is an example of an anastomosis 35:24. The Circle of Willis The Circle of Willis is an arterial anastomosis located at the base of the brain, receiving blood from the basilar and internal carotid arteries and serving the cerebrum, which is responsible for higher brain functions 35:35. The Circle of Willis surrounds the optic chiasm, providing blood supply to the eye, and the pituitary gland, making blood supply to the brain critical 35:49. Understanding the distribution and origin of these arteries from the Circle of Willis helps in understanding the effects of blood clots, aneurysms, or strokes on brain function 36:07. The anterior, posterior cerebral arteries, and the middle cerebral artery provide the most significant blood supply to the cerebrum 36:22. The two posterior cerebral arteries supply the inferior and medial portions of the temporal and occipital lobes, as well as the midbrain and pons 36:34. The internal carotid artery supplies the orbits and about 80% of the cerebrum, making it a crucial point to emphasize 36:54. Compression of the internal carotid artery near the mandible can cause loss of consciousness due to deprivation of 80% of the cerebrum's blood supply 37:05. Each internal carotid artery gives off branches, including the ophthalmic artery, anterior cerebral artery, and middle cerebral artery 37:18. The basilar artery is formed by the union of the two vertebral arteries, which can be used as a landmark to locate it 37:47. The Circle of Willis is a critical structure that supplies major areas of the brain, including the cerebral arterial circle 38:07. The internal carotid artery supplies important structures inside the skull, including major areas of the brain 38:17. Venous Drainage of the Head and Neck The arterial supply is emphasized more than the venous supply, but the venous system is also important 38:25. The head and neck are drained mainly by three pairs of veins: the internal jugular vein, external jugular vein, and vertebral veins 38:55. The large, thin-walled dural sinuses are spaces that form between the layers of dura mater, collecting blood from the veins and draining it into the internal jugular veins 39:24. Blood flows down the neck mainly through three veins on each side, all ending up in the subclavian vein 39:50. The internal jugular vein gets most of the blood from the brain, while the external jugular vein drains more of the external structures 39:58. The vertebral vein drains the cervical vertebrae, spinal cord, and some of the deep muscles of the neck, emptying into the subclavian vein 40:05. The brain receives blood from all vessels except the internal jugular, which is not an artery 40:45. Blood Supply to the Thorax The thorax is supplied by several arteries arising directly from the aorta and from the subclavian and axillary arteries 41:00. The thoracic aorta begins distal to the aortic arch and continues until the diaphragm, supplying the organs or viscera of the thoracic cavity 41:07. Bronchial arteries supply the bronchi of the lungs, esophageal arteries supply the esophagus, and mediastinal arteries supply the posterior mediastinal structures 41:33. Posterior intercostal arteries supply the muscles, bones, and skin of the posterior chest wall, including the intercostal muscles, pectoralis muscles, and some abdominal muscles 42:04. The superior phrenic arteries supply the superior and posterior parts of the diaphragm 42:43. Thoracic Veins The thoracic veins include the axillary veins, subclavian veins, internal jugular veins, and superior vena cava 43:08. The Abdominal Aorta and its Branches The aorta descends through the abdominal cavity below the diaphragm and splits into a left and right common iliac artery at the level of L4 43:23. The abdominal aorta gives off branches in a specific order, including the inferior phrenic artery, celiac trunk, superior mesenteric artery, renal arteries, gonadal arteries, and inferior mesenteric artery 43:34. The celiac trunk supplies the upper abdominal viscera, the superior mesenteric artery supplies most of the intestines, and the renal arteries supply the kidneys 43:53. The gonadal arteries supply the ovaries in females and the testicles in males, and the inferior mesenteric artery supplies the distal part of the large intestine 44:06. The lumbar arteries supply the posterior abdominal wall and spinal cord, and the medial sacral artery supplies the sacrum and coccyx 44:22. The common iliac arteries arise around the level of the lumbar four vertebrae, just above the belt line, and split into the right and left common iliac arteries 44:31. The Celiac Trunk and its Branches The Celiac trunk is a complex root in the abdominal aorta, with three main branches: the common hepatic artery, the left gastric artery, and the splenic artery 44:57. The common hepatic artery supplies the liver, gallbladder, pancreas, and duodenum, while the left gastric artery supplies the stomach, and the splenic artery supplies the spleen, pancreas, and stomach 45:17. The Mesentery and its Blood Supply The mesentery is a translucent sheet that suspends the intestines and other abdominal organs from the posterior body wall, with numerous arteries, veins, and lymphatic vessels that drain and supply the intestines 45:40. The arterial supply for the mesentery comes from the superior and inferior mesenteric arteries, with lots of anastomosis and collateral circulation to ensure the intestines are well-supplied with blood 46:04. The superior mesenteric artery supplies almost all of the small intestine and the proximal part of the large intestine, while the inferior mesenteric artery supplies the distal part of the large intestine 46:25. The Inferior Vena Cava The inferior vena cava is the body's largest blood vessel, forming when the right and left common iliac veins meet at around L5, and drains many of the abdominal viscera, including the lumbar veins, gonadal veins, renal veins, and hepatic veins 46:43. The inferior vena cava penetrates the diaphragm and enters the right atrium of the heart as part of the pulmonary circuit 47:25. The Hepatic Portal System Portal systems allow blood to pass from one capillary bed to another, with the hepatic portal system draining nutrient-rich blood from the stomach, spleen, and intestines to the liver for regulation of blood sugar levels 47:40. The hepatic portal system maintains blood sugar levels as a priority, as the brain's main blood supply is glucose, and red blood cells also rely on glucose for fuel 49:00. The liver plays a crucial role in cleansing the blood of bacteria and toxins, and the main veins contributing to the hepatic portal system include the inferior and superior mesenteric veins, the splenic vein, the hepatic portal vein, and the gastric veins 49:13. The hepatic portal system is responsible for draining nutrient-rich blood from the intestines to the liver, where it is detoxified before being sent to the right side of the heart 49:46. Blood Vessels of the Appendicular Region In the appendicular region, which includes the arms and legs, the systemic vessels follow a pattern where the veins run parallel to the arteries and often have similar names 50:07. The femoral artery runs parallel to the femoral vein, and the veins in the thigh can be found in both deep and superficial groups, with more anastomosis in the superficial groups 50:20. Arteries of the Upper Limb The arteries of the upper limb are well supplied by a prominent artery that changes its name as it passes through different regions, including the common carotid artery, brachiocephalic trunk, and subclavian artery 50:51. The subclavian artery branches into the axillary artery, which then becomes the brachial artery as it travels down the length of the humerus 51:23. The brachial artery is the most common site for measuring blood pressure and forks into the radial and ulnar arteries just distal to the elbow 52:09. The radial artery runs along the radius and is the most common place to take a pulse, while the ulnar artery runs more medially along the ulna 52:32. The blood supply to the hands and feet is extremely detailed and well supplied, with both superficial and deep veins draining the upper limb and ultimately leading to the axillary and subclavian veins 53:05. Arteries of the Lower Limb The lower limb follows a similar pattern of blood supply, with the abdominal aorta splitting into the common iliac arteries at the lumbar fourth vertebrae, which then become the internal and external iliac arteries, with the external iliac artery continuing to supply the lower limb 53:43. The external iliac artery passes behind the inguinal ligament in the groin region and becomes the femoral artery, descending to the knee, and running along the femur and popliteal area, specifically the popliteal fossa 54:15. In the leg, there are three significant arteries: the anterior tibial artery, posterior tibial artery, and fibular artery, which provide blood supply to the lower leg and foot 54:37. The anterior tibial artery supplies the anterior compartment of the leg, giving rise to dorsal arteries that supply the top of the foot, while the posterior tibial artery is a continuation of the popliteal artery, supplying the flexor muscles and giving rise to medial and lateral plantar arteries 54:39. The fibular artery travels on the lateral part of the compartment, supplying the lateral muscles of the leg 55:28. Veins of the Lower Limb The drainage of the lower limb from the toes to the inferior vena cava is accomplished by the superficial and deep veins, with the superficial veins including the dorsal venous arch, short saphenous vein, and great saphenous vein 55:42. The great saphenous vein is the longest vein in the body, traveling up the leg and thigh to the groin region, and emptying into the femoral vein, making it commonly used for clinical purposes 55:58. The deep veins in the area include the deep plantar venous arch, posterior tibial veins, fibular veins, and popliteal veins, which drain into the femoral vein, external iliac vein, internal iliac vein, and common iliac vein, eventually reaching the inferior vena cava 56:42. Conclusion The significance of various topics would be great questions to explore 58:17. UNIT 5 BIOL1050 Unit 5 video lecture Main image Respiratory System Unit 5 covers the respiratory system and the urinary system, specifically chapters 22 and 23 from the textbook 00:01. The respiratory system is a system of tubes that delivers air, allowing oxygen to diffuse into the blood and carbon dioxide to diffuse out 00:15. The need to breathe is driven by the body's requirement for oxygen to produce ATP and the need to eliminate carbon dioxide, a byproduct of metabolism 00:41. Carbon dioxide accumulation in tissues can cause acidity and pH drops, which can be detrimental to bodily functions 01:06. The respiratory system plays a role in removing acid from the body, working closely with the urinary system to regulate acid-base balance 01:31. The respiratory system works closely with the cardiovascular system to deliver oxygen and transport carbon dioxide 01:39. The proximity of the respiratory and cardiovascular systems in the thoracic cavity is due to their close functional relationship 02:05. Diseases or disorders of the lungs can affect the heart, and vice versa 02:27. The respiratory system can regulate acid-base balance by increasing the rate of exhalation to expel more carbon dioxide 02:52. The urinary system can excrete urine that is a thousand times more acidic than blood, but it does not kick in as quickly as the respiratory system 03:22. The focus of the unit is on the structures and anatomy of the respiratory and urinary systems, but understanding their function is also important 03:43. The respiratory system plays a role in ventilation, gas exchange, communication, acid-base balance, and regulating blood pressure 04:01. The system also helps regulate blood flow and lymph flow by creating pressure gradients when breathing in and out 04:35. The respiratory system plays a crucial role in contracting respiratory muscles, filtering blood, and expelling abdominal contents during urination, defecation, and childbirth 04:44. The principal organs of the respiratory system include the nose, lungs, trachea, bronchi, and lungs, with the right and left lung within the lungs 05:02. The air pathway in the lungs is considered a dead-end pathway, consisting of the bronchi, bronchioles, and alveoli, where gas exchange occurs with the bloodstream through the alveolar wall 05:17. The alveoli are millions of tiny, microscopic, thin-walled air sacs designed to facilitate gas exchange 05:36. The respiratory system can be divided into a conducting zone and a respiratory division, with the conducting zone consisting of passages for airflow and the respiratory division consisting of the alveoli and other gas exchange regions 06:00. The conducting zone includes the nostrils, major bronchioles, and trachea, with thicker walls that prevent diffusion of gases into the blood 06:12. The respiratory division includes the alveoli and other gas exchange regions located in the distal airway, designed for gas exchange 06:42. Air enters the nose, travels through the larynx, trachea, bronchi, bronchioles, and alveoli, with the lungs resembling a bronchial tree 06:50. The nose has several functions, including warming, cleansing, and humidifying inhaled air, detecting odors, and serving as a resonating chamber for amplifying the voice 07:48. The nose extends from the nostrils to the posterior nasal apertures, with the nasal cavity divided into right and left halves by the nasal septum 08:04. The nasal septum is a vertical plate of bone and cartilage that divides the right and left nasal fossa, with the vomer, ethmoid, and sphenoid bones contributing to the septum and the roof of the nasal cavity 08:31. The hard palate forms the floor of the nasal cavity, separating it from the oral cavity, and the nasal cavity also contains stiff guard hairs that block insects and debris from entering the nose 09:02. The body has various systems with openings that can be entry points for infections, but these areas often have protective designs, such as macrophages or white blood cells, to prevent foreign substances from entering the body 09:35. The urinary tract has acidic urine that helps flush out foreign substances, while the respiratory tract has mucosa that traps particles and cilia that move them along to be expelled from the body 10:04. The nasal cavity is filled with three folds of tissue, the superior, middle, and inferior nasal conchae, which create narrow air passages called meatuses that force air to contact the mucus membrane, allowing the nose to clean, warm, and humidify the air 10:32. The nasal cavity also contains sensory cells that detect odors, and cilia that help bind odor molecules, but these cilia are immobile and do not remove particles 11:13. The pharynx is a muscular funnel that extends to the larynx and has three regions: the nasopharynx, oropharynx, and laryngopharynx 11:40. The nasopharynx receives auditory tubes from the middle ears and houses the palatine tonsils, and when air is inhaled, it turns downward and passes through the nasopharynx, causing large particles to collide with the wall and stick to the mucosa 11:49. The oropharynx is a space between the soft palate and epiglottis, and the laryngopharynx lies posterior to the larynx and extends to the top of the epiglottis 12:41. The key distinction between the pharynx regions is that the nasopharynx only passes air, while the oropharynx and laryngopharynx pass air, food, and liquids 13:00. The larynx, also called the voice box, is a cartilaginous chamber that keeps food and drink out of the airway and plays a role in sound production 13:20. The epiglottis is a flap of tissue that guards the superior opening of the larynx and closes the airway when swallowing, directing food to the esophagus 13:38. The larynx framework consists of the epiglottic cartilage, which is spoon-shaped and supports the epiglottis, thyroid cartilage, and cricoid cartilage that connects the larynx to the trachea 14:16. The thyroid cartilage is the largest cartilage and is located at the laryngeal prominence, also known as the Adam's apple, typically between cervical vertebrae C4 and C5 14:30. The lower respiratory tract includes the trachea, a more rigid tube that sits anterior to the esophagus and is supported by 16 to 20 C-shaped cartilage rings made of hyaline cartilage 15:03. The trachea is lined with ciliated pseudostratified columnar epithelium, which contains mucus-secreting goblet cells to help trap particles, and cilia to move the mucus up and out of the lungs 15:35. The trachea splits into the right and left bronchi at the carina, located at the inferior margin of the trachea, which directs airflow into the right and left lungs 16:29. The bronchi split into smaller and smaller airways, including lower bronchi and segmental bronchi, which eventually lead to the terminal bronchioles 16:46. The lungs are not symmetrical, with the base being a broad concave portion that rests on the diaphragm and the apex projecting above the clavicle 17:06. The right lung is shorter due to the liver sitting higher on the right, and has a superior, middle, and inferior lobe separated by fissures, while the left lung is more tall and narrow due to the heart tilting to the left 18:05. The lungs are crowded by surrounding organs and do not entirely fill the rib cage, leaving room for expansion 17:55. The bronchial tree is a branching system of air tubes in each lung, with the main bronchus terminating and becoming 65,000 terminal bronchioles 18:56. The epithelium in the respiratory system changes from ciliated pseudostratified columnar to thinner layers as it progresses, with the primary function changing from conducting air to gas exchange 19:10. The laminar propria layer has an abundance of mucous glands and lymphocytes that help intercept inhaled pathogens, and the divisions of the bronchial tree have a large amount of elastic connective tissue 19:35. The mucosa has a well-developed layer of smooth muscle that contracts or relaxes to regulate airflow, and goblet cells secrete mucus that is propelled by cilia to be coughed or expelled 20:03. The main bronchi have C-shaped cartilage rings, with the right main bronchus being wider and more vertical than the left, while the secondary bronchi have crescent-shaped cartilage plates 20:24. The bronchi branch into smaller segmental or tertiary bronchi, which have crescent-shaped cartilage plates and are less than a millimeter in diameter, made of ciliated cuboidal epithelium 20:52. The bronchioles divide into terminal bronchioles, which are the final branches of the conducting zone, and each terminal bronchiole gives rise to two or more smaller respiratory bronchioles 21:30. The respiratory bronchioles have alveoli budding from their walls, increasing the surface area for gas exchange, and mark the beginning of the respiratory division 21:41. The respiratory bronchioles divide into alveolar ducts and end in alveolar sacs, which are clusters of alveoli around a central space called an atrium 22:09. Asthma is an inflammatory disease characterized by reversible airway obstruction, caused by the airway becoming hyperresponsive and the smooth muscle contracting, leading to excessive narrowing of the airways 22:19. The alveoli are highly efficient for gas exchange, with 150 million alveoli per lung, providing a 70 square meter surface area, and are well-supplied with blood 23:11. Each alveola is surrounded by a basket of capillaries supplied by the pulmonary artery, which are thin-walled exchange vessels designed for gas exchange across their surface 23:36. The respiratory membrane is a thin barrier between the alveolar air and the blood, consisting of type one squamous alveolar cells and endothelial cells of the blood capillary that share a basement membrane 24:09. Type one squamous alveolar cells are thin and flat, allowing for rapid gas diffusion and covering about 95% of the alveolar surface area 24:29. Type two cells are round to cuboidal, covering about 5% of the alveolar surface area, and are responsible for repairing the epithelium, secreting surfactant, and preventing alveolar collapse 24:35. Surfactant is crucial for preventing alveolar collapse, especially in premature babies, as it reduces surface tension and allows the lungs to expand and contract properly 24:52. Premature babies typically begin secreting surfactant at 26 weeks of fetal development, with adequate amounts secreted by 32 weeks and normal amounts by 35 weeks 25:33. Alveolar macrophages, also known as dust cells, are the most numerous cells in the lungs and act as phagocytes to ingest and remove dust particles and debris 26:08. The pleural coverings of the lungs consist of visceral pleura, which covers the lungs, and parietal pleura, which adheres to the cavity wall, with a space between them filled with pleural fluid that reduces friction and prevents infection 26:30. The pleural fluid creates a pressure gradient that helps the lungs expand and recoil properly 26:56. Urinary System The renal glarus is a network or bed of capillaries and is one of the key parts of the kidney 28:15. The urinary system consists of six main organs: the right and left kidney, two ureters, the urinary bladder, and the urethra 28:37. The ureters are the tubes that come from the right or left kidney to the urinary bladder, while the urethra is the tube that goes from the urinary bladder to the external environment 29:00. The kidneys form a filtrate, which is called urine at a later stage, and this urine travels from each kidney to the urinary bladder using the ureters 29:15. The kidneys are located along the posterior abdominal wall at the level of the thoracic 12 lowest vertebrae to the third lumbar, with the right kidney sitting slightly lower 29:52. The kidneys are retroperitoneal in location, meaning they are very posterior, and can cause flank or back pain if inflamed 30:06. The kidneys play a huge role in homeostasis by filtering blood plasma, excreting waste, regulating blood volume and blood pressure, and maintaining the osmolarity of the blood 30:44. The kidneys also regulate electrolytes, acid-base balance, and pH, and secrete erythropoietin to stimulate the production of red blood cells 31:06. Additionally, the kidneys help regulate calcium levels by synthesizing calcitriol, clear hormones from the blood, detoxify free radicals, and synthesize glucose from amino acids during starvation 31:41. Nitrogenous waste, including urea, uric acid, and creatinine, can be harmful if it stays in the body, and the kidneys play a crucial role in removing this waste 32:33. The gross anatomy of the kidney is relative in size and shape to a bar of soap 32:58. The kidney has a slit or opening that receives the renal nerves, blood vessels, lymphatics, and ureter, with the ureter bringing urine to the bladder 33:16. The renal parenchyma is glandular tissue that forms urine, encircling the renal sinus, a cavity containing blood, lymphatic vessels, urine-containing structures, and nerves 33:37. The gross anatomy of the kidney includes a tough fibrous capsule, an outer renal cortex, and an inner renal medulla, with renal columns extending from the cortex into the medulla 33:56. The renal pyramids have a broad base facing the cortex and a renal papilla facing the sinus, with each lobe of the kidney having one pyramid and the cortex above it 34:19. The minor calyx is a cup-shaped structure that collects urine from the papilla of each pyramid, while the major calyx is formed by the combination of two or three minor calyces 34:39. The renal pelvis is formed by the combination of two to three major calyces and drains urine into the ureter, which then drains into the bladder 35:02. The kidneys receive 21% of the cardiac output, making them extremely well-perfused with blood, with more blood flowing through the kidneys than the heart 35:25. Blood flow in the kidneys involves the glomerulus, a ball of capillaries, with blood draining into the efferent arterioles and then into peritubular capillaries or the vasa recta 35:49. The peritubular capillaries supply the glomerulus and the proximal and distal convoluted tubules, while the vasa recta supplies the nephron loop in the medulla 37:00. Nephrons are the functional units of the kidneys, with each kidney having 1.2 million nephrons, and are responsible for forming urine 37:50. The nephrons are the functional units of the kidney, responsible for concentrating urine and regulating pH, and they allow the kidneys to compensate for dehydration by producing concentrated urine 37:59. When the body is dehydrated, the kidneys produce urine with small amounts and a yellow color, as the body hangs on to as much water as it can, and when excess water is consumed, the kidneys produce more dilute urine 38:33. The nephron consists of a renal corpuscle, which filters the plasma of the blood, and a renal tubule, which converts the filtrate to urine 39:04. The renal corpuscle is composed of a glomerulus, a ball of capillaries, and a Bowman's capsule, a c-shaped structure that surrounds the glomerulus 39:41. The Bowman's capsule has an outer layer of simple squamous epithelium and an inner layer with podocytes that wrap around the capillaries, and the capsular space separates the two layers 40:00. The filtrate from the glomerulus collects in the capsular space and then flows into the proximal convoluted tubule 40:14. The proximal convoluted tubule is the longest and most coiled region of the nephron, with simple cuboidal epithelium and prominent microvilli that increase the surface area for absorption 41:59. The nephron also includes the loop of Henle, with descending and ascending loops, and the distal convoluted tubule, which ends in a collecting duct and then a papillary duct that leads to the ureter 40:56. The tubule is surrounded by capillaries and blood supply, allowing for the absorption of necessary substances and the excretion of waste products 41:25. The nephron's structure allows for the regulation of the amount of water in the body and the excretion of waste products, such as nitrogenous waste and acids 41:42. The body stores excess glucose in the form of glycogen in the liver and skeletal muscle, which can be broken down and made available as glucose when needed, such as during times of fasting or stress 42:35. In the proximal convoluted tubule, essential nutrients like glucose and water are absorbed, with most of the water being reabsorbed in this part of the tubule 43:26. The nephron loop is a U-shaped portion of the nephron, consisting of thick and thin segments, where salts are actively transported and water is reabsorbed 43:39. The thick segment of the nephron loop has cuboidal epithelium with many mitochondria, while the thin segment has simple squamous epithelium that is permeable to water 43:47. In the distal convoluted tubule, small adjustments are made to electrolyte levels, but most reabsorption occurs earlier in the tubular system 44:20. The collecting ducts receive fluid from multiple nephrons and converge to form the papillary duct, which then leads to the ureter 44:39. Anti-diuretic hormone (ADH) can modify the permeability of the distal convoluted tubule and collecting duct, allowing for increased water reabsorption in times of dehydration 45:15. ADH allows for the insertion of aquaporin channels, increasing the permeability to water and enabling the reabsorption of more water in the distal convoluted tubule and collecting duct 45:42. Most absorption and reabsorption occurs in the proximal convoluted tubule, including amino acids, glucose, 70% of water, and some electrolytes 46:27. Each kidney contains approximately 1.2 million nephrons, with superficial cortical nephrons making up 85% of all nephrons, extending partially into the medulla from the cortex 46:55. Midcortical nephrons have short or long loops, and juxamedullary nephrons are special nephrons that lie close to the border of the medulla and extend deep into it, allowing for a special concentrating ability 47:14. The longer the loop of a nephron, the more able it is to concentrate, creating a bigger concentrating gradient 47:41. The kidneys can secrete renin, which has a huge effect on blood pressure, as part of the RAA cascade (renin, aldosterone, angiotensin) 47:58. The juxtaglomerular apparatus allows for control of renal blood flow, tightly regulating blood pressure and ensuring homeostasis 48:15. Local control in the juxtaglomerular apparatus ensures that blood flow and blood pressure are tightly regulated, with macula densa cells sensing the concentration of sodium and chloride 48:57. The kidneys can secrete renin as needed to correct changes in blood pressure 49:29. The ureters are retroperitoneal, muscular tubes that pass posterior to the urinary bladder and enter it from below, with a flap of mucosa at the entrance of each ureter acting as a valve 49:41. The urinary bladder is a muscular sac with three layers: parietal peritoneum, fibrous adventitia, and a muscular layer with three layers of smooth muscle, as well as a mucosa layer with transitional epithelium 50:12. The transitional epithelium of the bladder allows it to distend when full of urine and relax back to normal, with umbrella cells on the surface protecting it from acidic urine 50:34. The capacity of the bladder is 500 milliliters at moderate fullness and up to 800 milliliters at maximal capacity, with the ability to expand superiorly as it fills 51:19. The urethra in males travels through the shaft of the penis, with different sections named based on the structures it passes through, such as the prostatic urethra 51:34. The urethra is divided into three parts: the prostatic portion, which passes through the prostate gland, the membranous portion, which passes through the muscular floor of the pelvic cavity, and the spongy or penile urethra, which passes through the penis 51:47. The detrusor muscle, which has smooth muscles, contracts involuntarily during urination, and there are two urethral sphincters: the internal urethral sphincter, which is a thickening of the detrusor muscle and has involuntary control, and the external urethral sphincter, which is located inferiorly and has skeletal muscle, allowing for voluntary control of urination 52:17. The external urethral sphincter's voluntary control is important, as it allows individuals to override the reflex of urination, especially in children as they develop 52:44. The process of filtrate becoming urine involves traveling through various structures, including the glomerulus, capsular space, proximal convoluted tubule, loop of Henle, collecting duct, renal papilla, minor calyx, major calyx, and renal pelvis 53:11. The point at which filtrate becomes urine and is no longer modified is near the end of the collecting duct 53:40. To study the structures of the urinary system, it is recommended to use diagrams and identify the different parts, starting with the largest structures and working down to the smallest 54:12. The test questions will focus on the structures of the urinary system, as well as their general functions, with supplementary information not being testable 54:39. Unit 6 BIOL1050 S6 video lecture Main image The Endocrine System The endocrine system is an important area to understand as it regulates and controls many processes in the body, and hormones are often discussed even outside of the endocrine unit 00:03. Hormones are one way cells communicate with each other, and they are chemical messengers that travel through the bloodstream to reach other tissues and organs 00:42. There are different ways cells communicate, including gap junctions, which are tiny channels that connect the cytoplasm of adjacent cells, and neurotransmitters, which are released from neurons and diffuse across the synoptic cleft 00:50. Hormones have far-reaching effects and can exert an influence anywhere the blood travels, whereas neurotransmitters have more local signals 02:31. Endocrine glands release hormones into the blood, whereas exocrine glands have ducts that carry their secretions to an epithelial surface or the mucosa of the digestive tract 02:42. Hormones can stimulate responses in cells of another tissue or organ, but they only affect cells that have receptors for that particular hormone, which is why some hormones have specific effects on certain systems or organs 02:56. Exocrine glands are secretions that are not hormones, and they typically have extracellular effects outside the cell, whereas endocrine glands have internal secretions with intracellular effects 03:52. Exocrine secretions, such as sweat, ear wax, and milk from mammary glands, are toxic if released into the blood, which is why they are secreted externally 04:40. The nervous system and endocrine system function closely together in communication, but they serve slightly different purposes 05:06. The nervous system uses electrical impulses or neurotransmitters, has local and specific effects, reacts quickly, and stops quickly, whereas the endocrine system uses hormones, has general and widespread effects, reacts slowly, and takes longer to end its effect 05:25. Hormones are used when the body needs to send a signal to affect something further away, whereas the nervous system is used for quick signals 05:51. The nervous system typically innervates only one organ or a limited number of cells, making its effect specific, whereas hormones circulate throughout the body and have widespread effects 06:37.

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