Anatomy & Physiology Prelim L1 PDF

ANATOMY & PHYSIOLOGY PRELIME: L1 Lesson 1: INTRODUCTION TO HUMAN BODY 1.1. ANATOMY & PHYSIOLOGY ANATOMY - is the scientific discipline that investigates the body’s structures—for example, the shape and size of bones. The wo...

ANATOMY & PHYSIOLOGY PRELIME: L1 Lesson 1: INTRODUCTION TO HUMAN BODY 1.1. ANATOMY & PHYSIOLOGY ANATOMY - is the scientific discipline that investigates the body’s structures—for example, the shape and size of bones. The word anatomy means to dissect or cut apart and separate the parts of the body for study. In addition, anatomy examines the relationship between the structure of a body part and its function. - (a-NAT-oˉ-meˉ; ana- = up; -tomy =process of cutting) is the science of body structures and the relationships among them - It was first studied by dissection (dis-SEK-shun; dis- = apart; -section = act of cutting), the careful cutting apart of body structures to study their relationships - DIFFERENT LEVELS: A. EMBRYOLOGY - subspecialty of developmental anatomy, considers changes from conception to the end of the eighth week of development. B. DEVELOPMENTAL ANATOMY - studies the structural changes that occur between conception and adulthood. C. CELL BIOLOGY - examines the structural features of cell D. HISTOLOGY - examines tissues, which are composed of cells and the materials surrounding them. E. GROSS ANATOMY - the study of structures that can be examined without the aid of a microscope, can be approached either systemically or regionally. F. SYSTEMIC ANATOMY G. REGIONAL ANATOMY H. SURFACE ANATOMY - involves looking at the exterior of the body to visualize structures deeper inside the body. For example, the sternum (breastbone) and parts of the ribs can be seen and palpated (felt) on the front of the chest. Health professionals use these structures as anatomical landmarks to identify regions of the heart and points on the chest where certain heart sounds can best be heard. I. IMAGING ANATOMY - uses radiographs (x-rays), ultrasound, magnetic resonance imaging (MRI), and other technologies to create pictures of internal structures. Anatomical imaging allows medical personnel to look inside the body with amazing accuracy and without the trauma and risk of exploratory surgery. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 J. PATHOLOGICAL ANATOMY PHYSIOLOGY - (fiz’-eˉ-OL-oˉ-jeˉ; physio- = nature; -logy = study of) is the science of body functions—how the body parts work. - is the scientific investigation of the processes or functions of living things. The major goals when studying human physiology are to understand and predict the body’s responses to stimuli and to EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 understand how the body maintains conditions within a narrow range of values in a constantly changing environment. - Physiology often examines systems rather than regions because a particular function can involve portions of a system in more than one region. - DIFFERENT LEVELS: A. CELL PHYSIOLOGY - examines the processes occurring in cells such as energy production from food. B. SYSTEMIC PHYSIOLOGY- considers the functions of organ systems. ▪ CARDIOBASCULAR PHYSIOLOGY - which focuses on the heart and blood vessels ▪ NUEROPHYSIOLOGY- which focuses on the function of the nervous system PATHOLOGY - (pa-thol′ō-jē) is the medical science dealing with all aspects of disease, with an emphasis on the cause and development of abnormal conditions, as well as the structural and functional changes resulting from disease. 1.2. STRUCTURAL AND FUNCTIONAL ORGANIZATION OF THE HUMAN BODY I. CHEMICAL - The structural and functional characteristics of all organisms are determined by their chemical makeup. The chemical level of organization involves how atoms (smallest units of matter), such as hydrogen and carbon, interact and combine into molecules (2 or more atoms joined together). This is important because a molecule’s structure determines its function. For example, collagen molecules are strong ropelike protein fibers that give skin structural strength and flexibility. a. Certain atoms, such as carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), calcium (Ca), and sulfur (S), are essential for maintaining life. Two familiar molecules found in the body are deoxyribonucleic acid (DNA), the genetic material passed from one generation to the next, and glucose, commonly known as blood sugar II. CELL - Cells are the basic structural and functional units of all living organisms. Cells contain smaller structures inside called organelles (or′gă-nelz; little organs). Organelles carry out particular functions, such as digestion and movement, for the cell. III. TISSUE - A tissue is composed of a group of similar cells and the materials surrounding them. The characteristics of the cells and surrounding materials determine the functions of the tissue. The body is made up of four basic tissue types: (1) epithelial, (2) connective, (3) muscle, and (4) nervous. a. Epithelial tissue covers body surfaces, lines hollow organs and cavities, and forms glands. b. Connective tissue connects, supports, and protects body organs while distributing blood vessels to other tissues. c. Muscular tissue contracts to make body parts move and generates heat. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 d. Nervous tissue carries information from one part of the body to another through nerve impulses. IV. ORGAN - An organ is composed of two or more tissue types that perform one or more common functions and usually have recognizable shapes. V. SYSTEM - An organ system is a group of organs that together perform a common function or set of functions and are therefore viewed as a unit. 11 major organ systems: a. (1) Integumentary -Provides protection, regulates temperature, prevents water loss, and helps produce vitamin D. Consists of skin, hair, nails, sweat glands, and oil glands i. Functions: Protects body; helps regulate body temperature; eliminates some wastes; helps make vitamin D; detects sensations such as touch, pain, warmth, and cold; stores fat and provides insulation. b. (2) Skeletal - Provides protection and support, allows body movements, produces blood cells, and stores minerals and adipose. Consists of bones, associated cartilages, ligaments, and joints. i. Functions: Supports and protects body; provides surface area for muscle attachments; aids body movements; houses cells that produce blood cells; stores minerals and lipids (fats). c. (3) Muscular - Produces body movements, maintains posture, and produces body heat. Consists of muscles attached to the skeleton by tendons. i. Functions: Participates in body movements, such as walking; maintains posture; produces heat. d. (4) Nervous - A major regulatory system that detects sensations and controls movements, physiological processes, and intellectual functions. Consists of the brain, spinal cord, nerves, and sensory receptors ( such as eyes and ears) i. Functions: Generates action potentials (nerve impulses) to regulate body activities; detects changes in body’s internal and external environments, interprets changes, and responds by causing muscular contractions or glandular secretion. e. (5) Endocrine - A major regulatory system that influences metabolism, growth, reproduction, and many other functions. Consists of glands, such as the pituitary, that secrete hormones i. Hormone-producing glands (pineal gland, hypothalamus, pituitary gland, thymus, thyroid gland, parathyroid glands, adrenal glands, pancreas, ovaries, and testes) and hormone-producing cells in several other organs. ii. Functions: Regulates body activities by releasing hormones (chemical messengers transported in blood from endocrine gland or tissue to target organ). f. (6) Cardiovascular - Transports nutrients, waste products, gases, and hormones throughout the body; plays a role in the immune response and the regulation of body temperature. Consists of the heart, blood vessels, and blood. i. Functions: Heart pumps blood through blood vessels; blood carries oxygen and nutrients to cells and carbon dioxide and wastes away from cells and helps regulate acid–base balance, temperature, and water content of body fluids; blood components help defend against disease and repair damaged blood vessels. g. (7) Lymphatic - Removes foreign substances from the blood and lymph, combats disease, maintains tissue fluid balance, and absorbs dietary fats from the digestive tract. Consists of the lymphatic vessels, lymph nodes, and other lymphatic organs i. Components: Lymphatic fluid and vessels; spleen, thymus, lymph nodes, and tonsils; cells that carry out immune responses (B cells, T cells, and others). ii. Functions: Returns proteins and fluid to blood; carries lipids from gastrointestinal tract to blood; contains sites of maturation and proliferation of B cells and T cells that protect against disease-causing microbes. h. (8) Respiratory - Exchanges oxygen and carbon dioxide between the blood and air and regulates blood pH. Consists of the lungs and respiratory passages i. Components: Lungs and air passageways such as the pharynx (throat), larynx (voice box), trachea (windpipe), and bronchial tubes leading into and out of lungs. ii. Functions: Transfers oxygen from inhaled air to blood and carbon dioxide from blood to exhaled air; helps regulate acid–base balance of body fluids; air flowing out of lungs through vocal cords produces sounds EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 i. (9) Digestive - Performs the mechanical and chemical processes of digestion, absorption of nutrients, and elimination of wastes. Consists of the mouth, esophagus, stomach, intestines, and accessory organs. i. Components: Organs of gastrointestinal tract, a long tube that includes the mouth, pharynx (throat), esophagus (food tube), stomach, small and large intestines, and anus; also includes accessory organs that assist in digestive processes, such as salivary glands, liver, gallbladder, and pancreas. ii. Functions: Achieves physical and chemical breakdown of food; absorbs nutrients; eliminates solid wastes. j. (10) Urinary - Removes waste products from the blood and regulates blood pH, ion balance, and water balance. Consists of the kidneys, urinary bladder, and ducts that carry urine. i. Components: Kidneys, ureters, urinary bladder, and urethra. ii. Functions: Produces, stores, and eliminates urine; eliminates wastes and regulates volume and chemical composition of blood; helps maintain the acid– base balance of body fluids; maintains body’s mineral balance; helps regulate production of red blood cells. k. (11) Reproductive i. Components: Gonads (testes in males and ovaries in females) and associated organs (uterine tubes or fallopian tubes, uterus, vagina, and mammary glands in females and epididymis, ductus or vas deferens, seminal vesicles, prostate, and penis in males). ii. Functions: Gonads produce gametes (sperm or oocytes) that unite to form a new organism; gonads also release hormones that regulate reproduction and other body processes; associated organs transport and store gametes; mammary glands produce milk VI. ORGANISM - An organism is any living thing considered as a whole—whether composed of one cell, such as a bacterium, or of trillions of cells, such as a human. The human organism is a network of organ systems, all mutually dependent on one another. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 1.3. CHARACTERISTICS OF LIFE I. Organization - refers to the specific interrelationships among the parts of an organism and how those parts interact to perform specific functions. Living things are highly organized. All organisms are composed of one or more cells. In turn, cellular function depends on the precise organization of large molecules. Disruption of this organized state can result in loss of functions, or even death. II. Metabolism - is the ability to use energy and to perform vital functions. Metabolism refers to all the chemical reactions taking place in the cells and internal environment of an organism. Metabolism is necessary for other vital functions, such as responsiveness, growth, development, and reproduction. a. Catabolism - (ka-TAB-oˉ-lizm; catabol-  throwing down; -ism = a condition), the breakdown of complex chemical substances into simpler components b. Anabolism - (a-NAB-oˉ-lizm; anabol- = a raising up), the building up of complex chemical substances from smaller, simpler components. III. Responsiveness - is an organism’s ability to sense changes in its external or internal environment and adjust to those changes. Responses include actions such as moving toward food or water and moving away from danger or poor environmental conditions. Organisms can also make adjustments that maintain their internal environment. For example, if the external environment causes the body temperature to rise, sweat glands produce sweat, which can lower body temperature down to the normal range. a. Different cells in the body respond to environmental changes in characteristic ways. Nerve cells respond by generating electrical signals known as nerve impulses (action potentials). Muscle cells respond by contracting, which generates force to move body parts. IV. Movement - includes motion of the whole body, individual organs, single cells, and even tiny structures inside cells. example, the coordinated action of leg muscles moves your whole body from one place to another when you walk or run. After you eat a meal that contains fats, your gallbladder contracts and releases bile into the gastrointestinal tract to help digest them. a. When a body tissue is damaged or infected, certain white blood cells move from the bloodstream into the affected tissue to help clean up and repair the area. Inside the cell, various parts, such as secretory vesicles V. Growth - refers to an increase in the size or number of cells, which produces an overall enlargement of all or part of an organism. For example, a muscle enlarged by exercise is composed of larger muscle cells than those of an untrained muscle, and the skin of an adult has more cells than the skin of an infant. An increase in the materials surrounding cells can also contribute to growth. For instance, bone grows because of an increase in cell number and the deposition of mineralized materials around the cells. VI. Development - includes the changes an organism undergoes through time, beginning with fertilization and ending at death. The greatest developmental changes occur before birth, but many changes continue after birth, and some go on throughout life. Development usually involves growth, but it also involves differentiation and morphogenesis. a. Differentiation involves changes in a cell’s structure and function from an immature, generalized state to a mature, specialized state. i. Such precursor cells, which can divide and give rise to cells that undergo differentiation, are known as stem cells. ii. For example, following fertilization, immature cells differentiate to become specific cell types, such as skin, bone, muscle, or nerve cells. These differentiated cells form tissues and organs. b. Morphogenesis (mōr-fō-jen′ĕ-sis) is the change in shape of tissues, organs, and the entire organism. VII. Reproduction - is the formation of new cells (cell division) or new organisms (fertilization; formation of zygote). Reproduction of cells allows for growth and development. All living organisms pass on their genes to their offspring. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 1.4. HOMESTASIS * Homeostasis is the existence and maintenance of a relatively constant environment within the body* * (hoˉ-me¯-oˉ-STAˉ-sis; homeo- = sameness; -stasis = standing still) is the condition of equilibrium (balance) in the body’s internal environment due to the constant interaction of the body’s many regulatory processes. * - Homeostasis is a dynamic condition - To achieve homeostasis, the body must actively regulate conditions that are constantly changing. - consistently influenced by different variables (ex., body temperature) - maintaining the body near an ideal normal value, or set point (however, not precisely at set point but slightly increase or decrease around the set point to produce a normal range values) HOMEOSTASIS & BODY FLUIDS - An important aspect of homeostasis is maintaining the volume and composition of body fluids, dilute, watery solutions containing dissolved chemicals that are found inside cells as well as surrounding them. A. ICF (Intracellular Fluid) – fluid within the cell B. ECF (Extracellular fluid) – fluid outside the cell ▪ ECF within the blood vessels = blood plasma ▪ ECF within lymphatic vessels = lymph ▪ ECF around the brain and spinal cord = cerebrospinal fluid ▪ ECF in joints = synovial fluid ▪ ECF of the eyes = aqueous humor & vitreous body C. Interstitial fluid – ECF that fills the narrow spaces between the cells of tissues. - The proper functioning of body cells depends on precise regulation of the composition of the interstitial fluid surrounding them. Because of this, interstitial fluid is often called the body’s internal environment. The composition of interstitial fluid changes as substances move back and forth between it and blood plasma. Such exchange of materials occurs across the thin walls of the smallest blood vessels in the body, the blood capillaries. This movement in both directions across capillary walls provides needed materials, such as glucose, oxygen, ions, and so on, to tissue cells. It also removes wastes, such as carbon dioxide, from interstitial. CONTROL OF HOMEOSTASIS - Most often, the nervous system and the endocrine system, working together or independently, provide the needed corrective measures. The nervous system regulates homeostasis by sending electrical signals known as nerve impulses (action potentials) to organs that can counteract changes from the balanced state. The endocrine system includes many glands that secrete messenger molecules called hormones into the blood. Nerve impulses typically cause rapid changes, but hormones usually work more slowly. Both means of regulation, however, work toward the same end, usually through negative feedback systems. - A feedback system or feedback loop is a cycle of events in which the status of a body condition is monitored, evaluated, changed, remonitored, reevaluated, and so on. - Each monitored variable, such as body temperature, blood pressure, or blood glucose level, is termed a controlled condition. Any disruption that changes a controlled condition is called a stimulus. A feedback system includes three basic components: a receptor, a control center, and an effector A. Receptor –monitors the value of a variable by detecting stimuli. ▪ This pathway is called an afferent pathway (AF-er-ent; af- = toward; -ferrent = carried), since the information flows toward the control center. ▪ Typically, the input is in the form of nerve impulses or chemical signals. ▪ For example, certain nerve endings in the skin sense temperature and can detect changes, such as a dramatic drop in temperature. B. Control Center- part of the brain that determines the set point for variable, , evaluates the input it receives from receptors, and generates output commands when they are needed ▪ Output from the control center typically occurs as nerve impulses, or hormones or other chemical signals. This pathway is called an efferent pathway (EF-er-ent; ef-= away from), since the information flows away from the control center. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 C. Effector – can adjust the value of the variable when directed by the control center (usually back towards the set point). ▪ is a body structure that receives output from the control center and produces a response or effect that changes the controlled condition. ▪ Nearly every organ or tissue in the body can behave as an effector. ▪ When your body temperature drops sharply, your brain (control center) sends nerve impulses (output) to your skeletal muscles (effectors). The result is shivering, which generates heat and raises your body temperature. NEGATIVE FEEDBACK MECHANISM - Most systems of the body are regulated by negative-feedback mechanisms, which maintain homeostasis. - In everyday terms, the word negative is used to mean “bad” or “undesirable.” - In this context, negative means “to decrease.” - Negative feedback is when any deviation from the set point is made smaller or is resisted; therefore, in a negative-feedback mechanism, the response to the original stimulus results in deviation from the set point, becoming smaller. - Reverses a change in a controlled condition * Often, there is more than one effector, and the control center must integrate them* *Although homeostasis is the maintenance of a normal range of values, this does not mean that all variables remain within the same narrow range of values at all times. Sometimes a deviation from the usual range of values can be beneficial* > For example, during exercise the normal range for blood pressure increases above the resting range. The increase in blood pressure helps to supply muscle cells with the greater amount of oxygen. POSITIVE FEEDBACK MECHANISM - mechanisms occur when a response to the original stimulus results in the deviation from the set point becoming even greater. - In other words, positive means “increase.” - Tends to strengthen or reinforce a change in one of the body’s controlled mechanism - At times, this type of response is required to return to homeostasis. A. For example, during blood loss, a chemical responsible for blood clot formation, called thrombin, stimulates production of even more thrombin. B. Birth is another example of a normally occurring positivefeedback mechanism. Near the end of pregnancy, the baby’s larger size stretches the uterus. This stretching, especially around EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 the opening of the uterus, stimulates contractions of the uterine muscles. The uterine contractions push the baby against the opening of the uterus and stretch it further. This stimulates additional contractions, which result in additional stretching. The sequence ends only when the baby is delivered from the uterus and the stretching stimulus is eliminated. * Two basic principles about homeostatic mechanisms to remember (1) many disease states result from the failure of negative-feedback mechanisms to maintain homeostasis and; (2) some positive-feedback mechanisms can be detrimental instead of helpful. > One example of a detrimental positive-feedback mechanism is inadequate delivery of blood to cardiac (heart) muscle. Contraction of cardiac muscle generates blood pressure and the heart pumps blood to itself through a system of blood vessels on the outside of the heart. Just as with other tissues, blood pressure must be maintained to ensure adequate delivery of blood to the cardiac muscle. Following extreme blood loss, blood pressure decreases to the point that the delivery of blood to cardiac muscle is inadequate. As a result, cardiac muscle does not function normally. The heart pumps less blood, which causes the blood pressure to drop even further—a deviation further from the set point. The additional decrease in blood pressure further reduces blood delivery to cardiac muscle, and the heart pumps even less blood, which again decreases the blood pressure. The process self- propagates until the blood pressure is too low to sustain the cardiac muscle, the heart stops beating, and death results. In this example, we see the deviation from the heart rate set point becoming larger and larger—this is a positive-feedback mechanism. HOMEOSTATIC IMBALANCES - The body’s ability to maintain homeostasis gives it tremendous healing power and a remarkable resistance to abuse. The physiological processes responsible for maintaining homeostasis are in large part also responsible for your good health. - For most people, lifelong good health is not something that happens effortlessly. The many factors in this balance called health include the following: A. Environment and behavior B. Genetic makeup C. The air you breathe, food you eat, and thoughts you think. - Many diseases are the result of years of poor health behavior that interferes with the body’s natural drive to maintain homeostasis. - Developing a lifestyle that works with, rather than against, your body’s homeostatic processes helps you maximize your personal potential for optimal health and well-being. - As long as all of the body’s controlled conditions remain within certain narrow limits, body cells function efficiently, homeostasis is maintained, and the body stays healthy. - A disorder is any abnormality of structure or function. - Disease is a more specific term for an illness characterized by a recognizable set of signs and symptoms. A. Local = affects one part or a limited region of the body B. Systemic = affects either the entire body or several parts of it. C. Symptoms ▪ Subjective = not apparent to the observer (ex., headache, nausea, anxiety) ▪ Objectives = changes that clinician can observe and measure (often termed as signs). Examples are swelling, rash, fever, high BP, and paralysis. - 1.5. TERMINOLOGY & BODY PLAN - Etymology or derivation - Most anatomical term are derived from Greek or Latin - Prefixes and suffixes can be added to words to expand their meaning (ex., “-itis” = inflammation) - It is very helpful to learn these new words, so that your message is clear and correct when you speak to colleagues or write reports. Additionally, you will find many of the roots of words appearing over and over again. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 BODY POSITIONS - Anatomical position refers to a person standing erect with the face directed forward, the upper limbs hanging to the sides, and the palms of the hands facing forward. A. SUPINE = Lying face upward B. PRONE = Lying face downward - In anatomical position, the head is above the feet would still be the prefered position of the head as being, because the point of reference for anatomical structures is the body, not the position of the body structure compared to the earth. DIRECTIONAL TERMS - Right and left are used as directional terms in anatomical terminology. - For human anatomy, the term superior is used interchangeably with the term cephalic (se-fal′ik; head), and the term inferior is used interchangeably with caudal (kaw′dăl; tail). - In animals that do not walk upright, such as a cat, the terms cephalic and caudal can be used to describe the relative position of anatomical structures on the trunk, but not on the limbs. - In addition, anterior is synonymous with ventral (belly) and posterior is synonymous with dorsal (back) EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 BODY PARTS & REGIONS - The central region of the body consists of the head, neck, and trunk. - The trunk can be further divided into three regions: (1) the thorax (2) the abdomen, and (3) the pelvis. - The thorax is the chest cavity where the heart and lungs are located. - The abdomen contains organs such as (1) the liver, (2) the stomach, and (3) the intestines. - The pelvis contains the bladder and reproductive organs. The upper limb is divided into (1) the arm, (2) the forearm, (3) the wrist, and (4) the hand. - The arm extends from the shoulder to the elbow, and the forearm extends from the elbow to the wrist. The lower limb is divided into (1) the thigh, (2) the leg, (3) the ankle, and (4) the foot. - The thigh extends from the hip to the knee, and the leg extends from the knee to the ankle. Note that, contrary to popular usage, the terms arm and leg refer to only a part of the limb. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 - The abdomen is often subdivided superficially into quadrants by two imaginary lines—one horizontal and one vertical—that intersect at the navel. - In addition to these quadrants, the abdomen is sometimes subdivided into regions by four imaginary lines: two horizontal and two vertical. These four lines create a “virtual” tic-tac-toe grid on the abdomen, resulting in nine regions: - PLANES - At times, it is useful to describe the body as having imaginary flat surfaces, called planes, passing through it. - A plane divides, or sections, the body, making it possible to “look inside” and observe the body’s structures. A. A sagittal (saj′i-tăl) plane separates the body or a structure into right and left halves. The word sagittal means “the flight of an arrow” and refers to the way the body would be split by an arrow passing anteriorly to posteriorly. B. A median plane is a sagittal plane that passes through the midline of the body, dividing it into equal right and left halves. C. Parasagittal plane divides the body or an organ into unequal left and right sides D. A transverse (horizontal) plane/cross-sectional runs parallel to the ground, dividing the body into superior and inferior portions. E. A frontal (coronal) (kōr′ŏ-năl, kō-rō′năl; crown) plane divides the body into front (anterior) and back (posterior) halves. For example, the coronal suture on the skull is located across the top, where a person might wear a crown. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 - Organs are often sectioned to reveal their internal structure. ▪ A cut through the length of the organ is a longitudinal section. ▪ A cut at a right angle to the length of an organ is a transverse (cross) section. ▪ If a cut is made across the the length of an organ at other than a right angle, it is called an oblique section. BODY CAVITIES - DORSAL BODY CAVITY ▪ The dorsal body encloses the organs of the nervous system, the brain and spinal cord. 1. The two subdivisions of the dorsal body cavity are (1) the cranial cavity, which houses the brain, and 2. (2) the vertebral canal, which houses the spinal cord. ▪ Both the brain and spinal cord are covered by membranes called meninges - VENTRAL BODY CAVITY ▪ The ventral body cavity houses the vast majority of our internal organs, collectively referred to as the viscera (vis′er-ah; internal organs). ▪ The ventral body cavity also has two major subdivisions: 1. THORACIC CAVITY – more superior to the abdominopelvic cavity and houses primarily the heart and lungs, among other organs. o Pleural (lungs) ▪ The diaphragm (DI¯-a-fram = partition or wall) is a dome- shaped muscle that separates the thoracic cavity from the abdominopelvic cavity. o Mediastinum (heart & its major blood vessels; thymus, trachea, and esophagus) 2. ABDOMINOPELVIC CAVITY - enclosed by abdominal muscles. The organs of the abdominopelvic cavity are housed within the peritoneal (per′i-tō-nē′ăl; to stretch over) cavity. o more superior abdominal cavity (The abdominal cavity contains the majority of the digestive organs, such as the stomach, the intestines, and the liver, in addition to the spleen.) o more inferior pelvic cavity (continues below the pelvis and contains the urinary bladder, urethra, rectum of the large intestine, and reproductive organs.) EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 ▪ SEROUS MEMBRANES OF THE VENTRAL BODY CAVITY: o The walls of the body cavities and the surface of internal organs are in contact with membranes called serous membranes. o A membrane is a thin, pliable tissue that covers, lines, partitions, or connects structures. o These membranes are double layered. ▪ The layer (thin epithelium) that lines the walls of the cavities is called the parietal (pă-rī′ĕ-tăl; wall) serous membrane. ▪ The layer (thin epithelium) covering the internal organs (the viscera) is the visceral serous membrane. o In the body, the parietal serous membrane is in close contact with the body cavity wall. Furthermore, in the body, there is no air between the visceral and parietal serous membranes. the two membranes are separated by a thin film of serous fluid produced by the membranes. As organs move around in the cavities, the combination of serous fluid and smooth serous membranes reduces friction. o The serous membranes are named for the specific cavity and organs they are in contact with: EMSL, RMT ANATOMY & PHYSIOLOGY PRELIME: L1 ▪ PERICARDIAL CAVITY - The pericardial cavity (peri = around; cardi = heart), containing the heart, is housed in the mediastinum. Parietal pericardium Visceral pericardium Pericardial fluid ▪ PLEURAL CAVITY - Each of the two pleural cavities (pleuron = side of body, rib) houses a lung. Parietal pleura Visceral pleura Pleural fluid ▪ PERITONEAL CAVITY - The peritoneal cavity (peri = around; - tonos = stretched; stretched around) houses many internal organs, such as the liver, the digestive organs, and the reproductive organs. ▪ The peritoneum (per-i-to¯-NE¯-um) is the serous membrane of the abdominal cavity. In addition to covering organs, a double-folded sheet of visceral peritoneum attaches the digestive organs at certain points to the posterior abdominopelvic cavity wall. These regions of double- folded visceral peritoneum are called mesenteries. The mesenteries also provide a pathway for nerves and blood vessels to reach the digestive organs. The most notable mesenteric structure is an enormous pouch containing adipose tissue that is suspended from the inferior border of the stomach. In some people, this pouch contributes to their “big belly”. Some abdominal organs are tightly adhered to the posterior body wall and are covered by peritoneum only on their peritoneal cavity side. These organs have a retroperitoneal (re′trō-per′i-tō-nē′ăl; behind the peritoneum) location and include the kidneys, ureters, adrenal glands, a large portion of the pancreas, parts of the large intestine, and the urinary bladder. o m. Some are not surrounded by the peritoneum; instead they are posterior to it [to limit repetition of peritoneum]. o The kidneys, adrenal glands, pancreas, duodenum of the small intestine, ascending and descending colons of the large intestine, and portions of the abdominal aorta and inferior vena cava are retroperitoneal. EMSL, RMT  ANATOMY & PHYSIOLOGY PRELIME: L1 REFERENCE(s) G. Tortora & B. Derrickson (2014) Principles of ANATOMY & PHYSIOLOGY 14th Edition C. VanPutte et al. (2020) Seeley’s ANATOMY & PHYSIOLOGY 12th Edition EMSL, RMT