Unit 1 Cooked - Blood, Tissues, and Organ Systems (PDF)

**6.1 Blood: An Overview (COOKED 6)** - The heart pumps 75 ml of blood with each contraction - On average, the heart beats 70 times/minute - 5250 ml per minute - The entire blood supply is circulated each minute **Functions of blood** - Transport - Defense - Regulation **C...

**6.1 Blood: An Overview (COOKED 6)** - The heart pumps 75 ml of blood with each contraction - On average, the heart beats 70 times/minute - 5250 ml per minute - The entire blood supply is circulated each minute **Functions of blood** - Transport - Defense - Regulation **Composition of Blood** - Formed Elements are produced in the red bone marrow - Red blood cells/erythrocytes - White blood cells/leukocytes - Platelets/thrombocytes **Plasma** - Consists of 91% water and 9% salt and organic molecules - Solutes help maintain osmotic pressure of blood - Salt acts as buffers - Solutes: nutrients, waste, hormones - Plasma proteins are the most abundant organic molecules - Most are created by the liver - Create osmotic pressure in the blood **Three major types of plasma proteins** ***Albumins*** - Most abundant of the plasma proteins - Contribute to osmotic pressure more than others - Transport molecules in the blood ***Globulins*** - Some transport substances in the blood - Others, gamma globulins, fight pathogens **6.2 Red Blood Cells and Transport of Gases** **Red Blood Cells (erythrocytes)** - Biconcave shape increases surface area - An unusual cell type in the body due to hemoglobin and unique internal structure - Specialized for oxygen transport **Contains the protein hemoglobin** - A pigment that binds oxygen - The heme portion of Hb binds up to 4 oxygens - Also binds carbon monoxide - When bound to oxygen, hb is called oxyhemoglobin - When oxygen leaves Hb in the tissues, it is called deoxyhemoglobin **Carbon Dioxide Transport** - 7% of cfrbc - is transported dissolved in plasma - 23% binds to the globin portion of hemoglobin - Hemoglobin bound to co2 is called carbaminohemoglobin - 70% is transported in plasma as bicarbonate ion **Red Blood Cells are produced in the Bone Marrow** ***The Production of Red Blood Cells*** - Occurs in the red bone marrow - Lose their nucleus and most organelles ***Erythropoietin*** - Hormone produced by the kidneys when o2 levels of the blood are low - Stimulates the bone marrow to produce more red blood cells **Disorders Involving RBCS** - Jaundice- accumulations of heme in the blood if the liver can't excrete it (skin and whites of the eyes turn yellow (alcohol) - k- too few RBCs or too little hemoglobin - Iron-deficiency anemia- most common form, inadequate intake of dietary iron, so can't make Hb - Pernicious anemia-lack of k b12, which is needed to make RBCS - Folic-acid-deficiency anemia- need folic acid to make RBCS - Hemolytic anemia- too much hemolysis (rupturing the rbcs) - Sickle-cell disease- genetic disease that cause rbcs to become sickle-shaped and prone to rupture (defective hemoglobin structure) **6.3 White Blood Cells and Defense Against Disease** **White blood cells (leukocytes)** - Large cells; nucleus - Translucent unless stained - Less numerous than rbcs - Produced in red bone barrow; production **is regulated by colony stimulating factor** - Fight infection (immune system) - Some live for days some for months/years **Granular Leukocytes** ***Neutrophils*** - Most abundant wbc (50-70%) - Multilobed nucleus - First responders to infection - Engulf pathogens by phagocytosis ***Eosinophils*** - Bilobed nucleus - Many large granules - Function in parasitic infections and play a role in allergies ***Basophils*** - Rarest/blood thinner - Ushaped nucleus - Turns into [mast cells], release histamine during allergic reactions - Histamine dilates blood vessels but constricts breathing passageways **Agranular Leukocytes** ***Lymphocytes*** - 25-35% of wbcs - B and T cells - B cells produce antibodies, which mark a pathogen for destruction - Some cytotoxic t cells directly destroy pathogens ***Monocytes*** - Largest of the wbcs - In tissues, they develop into even larger [macrophages], which engulf pathogens, old cells, and debris **Disorders Involving WBCS** - Severe Combined Immunodeficiency Disease- inherited disease in which lymphocytes don't develop (SCID) (enzyme adeniose deaminase doesn't develop) - Leukemia- group of cancers in which wbcs proliferate without control - Infectious mononucleosis- Epstein Barr virus infects lymphocytes, resulting in fatigue, sore throat, and swollen lymph nodes **6.4 Platelets and Blood Clotting** **Platelets (thrombocytes)** - Result from fragmentation of large cells called megakaryocytes in the red bone marrow - Are not true cells - About 200 billion platelets are made per day - Function in blood clotting (coagulation) - Plasma proteins prothrombin and fibrinogen are also involved in blood clotting - vitmain k is necessary for the formation of prothrombin Blood clotting - Is important so that plasma and formed elements don't leak out of broken vessels - 13 different clotting factors, calcium ions, and enzymes participate in clot formation 1. Blood vessel is punctured 2. Platelets congregate and form a plug 3. Platelets and damaged tissue cells release prothrombin activator, which initiates a cascade of enzymatic reactions 4. Fibrin thread form and trap red blood cells **Disorders related to blood clotting** ***Thrombocytopenia-*** too few platelets; due to not enough being made in the bone marrow or the increased breakdown outside the marrow. Can be caused by leukemia or drugs. Symptoms: excess bleeding. ***Thromboembolism***- when a thrombus (stationary clot) forms, travels (it's then called an embolism), and plugs another vessel. ***Hemophilia A, Hemophilia B*** (Christmas disease), and Von Willebrand disease- genetic deficiencies of a clotting factor. Unable to form clots. Can be partially treated with injections of the missing proteins. **6.5 Human Blood Types** **Blood types** - Determined by proteins on the surface of rbcs **Blood transfusion** - Transfer of blood from one person to another - Need to make sure blood types of compatible to prevent agglutination, or clumping of red blood cells **ABO Blood Groups** ***Antigen*** - Foreign substance, often a glycoprotein, that stimulates an immune response - Blood types are determined by the presence and/or absence of two antigens, type a and type b Type a- rbcs have type a surface antigens, plasma has anti-b antibodies Type B- rbcs have type b surface antigens, plasma has anti-a antibodies Type ab- rbcs have type a and b surface antigens, no antibodies Type o blood- shi got nothing chat ***Blood compatibility*** If antibodies in the recipient's plasma bind to antigens on the surface of donated rbcs, agglutination can occur Crossmatches are to be sure (mix small amounts of blood to test for agglutination O is universal donor because it lacks antigens (only once) ***Rh blood groups*** - Rh is another blood type antigen; if it is present, the blood is rh +, if not its negative - Anti-Rh antibodies only develop after they are exposed to the rh factor Hemolytic disease of the newborn Rh- woman makes baby that is rh+, first time is fine (mixing of fetal and paternal blood, antibodies) Pregnant the second time rh+, antibodies cross placenta and attack the fetus's red blood cells RhoGAM shot prevents this (anti-rh antibodies) **6.6 Homeostasis** The organ systems of the body interact with the cardiovascular system to maintain homeostasis. Interactions include: [The cardiovascular and lymphatic systems] - Interstitial fluid originates from blood plasma, is absorbed by lymphatic capillaries, becoming lymph. - The lymph courses through lymphatic vessels, eventually returning to the cardiovascular system. [The cardiovascular and respiratory systems.] - Delivers oxygen from the lungs to the rest of the body. [The cardiovascular and digestive systems.] - Delivers nutrients from the digestive system to the interstitial fluid. - Removes metabolic waste, delivering waste to excretory organs. [The cardiovascular and muscular systems.] - Contribute to blood movement. - Cardiac muscle contractions circulate blood throughout the body. - Smooth muscle contraction or relaxation in the blood vessel walls changes vessel diameter, helping maintain the correct blood pressure. - Skeletal muscle contraction compresses cardiovascular and lymphatic vessels. - Lymph returns to cardiovascular veins. - Blood in the cardiovascular veins drains back to the heart. [The cardiovascular and skeletal systems.] - Red bone marrow produces blood cells - Bones contribute calcium ions to the process of blood clotting [The cardiovascular and endocrine systems.] - Hormones regulate blood cell production and bone calcium release. [The cardiovascular and urinary systems.] - The kidneys help regulate the acid-base and water-salt balances of the blood and interstitial fluid. - Erythropoietin, a hormone produced by the kidneys, stimulates red blood cell production. Quiz extras: coagulation contributes to homeostasis by keeping blood in the vessels A person who cannot produce the enzyme adenosine deaminase may develop: **6.1 Blood: An Overview (COOKED 6)** - The heart pumps 75 ml of blood with each contraction - On average, the heart beats 70 times/minute - 5250 ml per minute - The entire blood supply is circulated each minute **Functions of blood** - Transport - Defense - Regulation **Composition of Blood** - Formed Elements are produced in the red bone marrow - Red blood cells/erythrocytes - White blood cells/leukocytes - Platelets/thrombocytes **Plasma** - Consists of 91% water and 9% salt and organic molecules - Solutes help maintain osmotic pressure of blood - Salt acts as buffers - Solutes: nutrients, waste, hormones - Plasma proteins are the most abundant organic molecules - Most are created by the liver - Create osmotic pressure in the blood **Three major types of plasma proteins** ***Albumins*** - Most abundant of the plasma proteins - Contribute to osmotic pressure more than others - Transport molecules in the blood ***Globulins*** - Some transport substances in the blood - Others, gamma globulins, fight pathogens **6.2 Red Blood Cells and Transport of Gases** **Red Blood Cells (erythrocytes)** - Biconcave shape increases surface area - An unusual cell type in the body due to hemoglobin and unique internal structure - Specialized for oxygen transport **Contains the protein hemoglobin** - A pigment that binds oxygen - The heme portion of Hb binds up to 4 oxygens - Also binds carbon monoxide - When bound to oxygen, hb is called oxyhemoglobin - When oxygen leaves Hb in the tissues, it is called deoxyhemoglobin **Carbon Dioxide Transport** - 7% of cfrbc - is transported dissolved in plasma - 23% binds to the globin portion of hemoglobin - Hemoglobin bound to co2 is called carbaminohemoglobin - 70% is transported in plasma as bicarbonate ion **Red Blood Cells are produced in the Bone Marrow** ***The Production of Red Blood Cells*** - Occurs in the red bone marrow - Lose their nucleus and most organelles ***Erythropoietin*** - Hormone produced by the kidneys when o2 levels of the blood are low - Stimulates the bone marrow to produce more red blood cells **Disorders Involving RBCS** - Jaundice- accumulations of heme in the blood if the liver can't excrete it (skin and whites of the eyes turn yellow (alcohol) - k- too few RBCs or too little hemoglobin - Iron-deficiency anemia- most common form, inadequate intake of dietary iron, so can't make Hb - Pernicious anemia-lack of k b12, which is needed to make RBCS - Folic-acid-deficiency anemia- need folic acid to make RBCS - Hemolytic anemia- too much hemolysis (rupturing the rbcs) - Sickle-cell disease- genetic disease that cause rbcs to become sickle-shaped and prone to rupture (defective hemoglobin structure) **6.3 White Blood Cells and Defense Against Disease** **White blood cells (leukocytes)** - Large cells; nucleus - Translucent unless stained - Less numerous than rbcs - Produced in red bone barrow; production **is regulated by colony stimulating factor** - Fight infection (immune system) - Some live for days some for months/years **Granular Leukocytes** ***Neutrophils*** - Most abundant wbc (50-70%) - Multilobed nucleus - First responders to infection - Engulf pathogens by phagocytosis ***Eosinophils*** - Bilobed nucleus - Many large granules - Function in parasitic infections and play a role in allergies ***Basophils*** - Rarest/blood thinner - Ushaped nucleus - Turns into [mast cells], release histamine during allergic reactions - Histamine dilates blood vessels but constricts breathing passageways **Agranular Leukocytes** ***Lymphocytes*** - 25-35% of wbcs - B and T cells - B cells produce antibodies, which mark a pathogen for destruction - Some cytotoxic t cells directly destroy pathogens ***Monocytes*** - Largest of the wbcs - In tissues, they develop into even larger [macrophages], which engulf pathogens, old cells, and debris **Disorders Involving WBCS** - Severe Combined Immunodeficiency Disease- inherited disease in which lymphocytes don't develop (SCID) (enzyme adeniose deaminase doesn't develop) - Leukemia- group of cancers in which wbcs proliferate without control - Infectious mononucleosis- Epstein Barr virus infects lymphocytes, resulting in fatigue, sore throat, and swollen lymph nodes **6.4 Platelets and Blood Clotting** **Platelets (thrombocytes)** - Result from fragmentation of large cells called megakaryocytes in the red bone marrow - Are not true cells - About 200 billion platelets are made per day - Function in blood clotting (coagulation) - Plasma proteins prothrombin and fibrinogen are also involved in blood clotting - vitmain k is necessary for the formation of prothrombin Blood clotting - Is important so that plasma and formed elements don't leak out of broken vessels - 13 different clotting factors, calcium ions, and enzymes participate in clot formation 5. Blood vessel is punctured 6. Platelets congregate and form a plug 7. Platelets and damaged tissue cells release prothrombin activator, which initiates a cascade of enzymatic reactions 8. Fibrin thread form and trap red blood cells **Disorders related to blood clotting** ***Thrombocytopenia-*** too few platelets; due to not enough being made in the bone marrow or the increased breakdown outside the marrow. Can be caused by leukemia or drugs. Symptoms: excess bleeding. ***Thromboembolism***- when a thrombus (stationary clot) forms, travels (it's then called an embolism), and plugs another vessel. ***Hemophilia A, Hemophilia B*** (Christmas disease), and Von Willebrand disease- genetic deficiencies of a clotting factor. Unable to form clots. Can be partially treated with injections of the missing proteins. **6.5 Human Blood Types** **Blood types** - Determined by proteins on the surface of rbcs **Blood transfusion** - Transfer of blood from one person to another - Need to make sure blood types of compatible to prevent agglutination, or clumping of red blood cells **ABO Blood Groups** ***Antigen*** - Foreign substance, often a glycoprotein, that stimulates an immune response - Blood types are determined by the presence and/or absence of two antigens, type a and type b Type a- rbcs have type a surface antigens, plasma has anti-b antibodies Type B- rbcs have type b surface antigens, plasma has anti-a antibodies Type ab- rbcs have type a and b surface antigens, no antibodies Type o blood- shi got nothing chat ***Blood compatibility*** If antibodies in the recipient's plasma bind to antigens on the surface of donated rbcs, agglutination can occur Crossmatches are to be sure (mix small amounts of blood to test for agglutination O is universal donor because it lacks antigens (only once) ***Rh blood groups*** - Rh is another blood type antigen; if it is present, the blood is rh +, if not its negative - Anti-Rh antibodies only develop after they are exposed to the rh factor Hemolytic disease of the newborn Rh- woman makes baby that is rh+, first time is fine (mixing of fetal and paternal blood, antibodies) Pregnant the second time rh+, antibodies cross placenta and attack the fetus's red blood cells RhoGAM shot prevents this (anti-rh antibodies) **6.6 Homeostasis** The organ systems of the body interact with the cardiovascular system to maintain homeostasis. Interactions include: [The cardiovascular and lymphatic systems] - Interstitial fluid originates from blood plasma, is absorbed by lymphatic capillaries, becoming lymph. - The lymph courses through lymphatic vessels, eventually returning to the cardiovascular system. [The cardiovascular and respiratory systems.] - Delivers oxygen from the lungs to the rest of the body. [The cardiovascular and digestive systems.] - Delivers nutrients from the digestive system to the interstitial fluid. - Removes metabolic waste, delivering waste to excretory organs. [The cardiovascular and muscular systems.] - Contribute to blood movement. - Cardiac muscle contractions circulate blood throughout the body. - Smooth muscle contraction or relaxation in the blood vessel walls changes vessel diameter, helping maintain the correct blood pressure. - Skeletal muscle contraction compresses cardiovascular and lymphatic vessels. - Lymph returns to cardiovascular veins. - Blood in the cardiovascular veins drains back to the heart. [The cardiovascular and skeletal systems.] - Red bone marrow produces blood cells - Bones contribute calcium ions to the process of blood clotting [The cardiovascular and endocrine systems.] - Hormones regulate blood cell production and bone calcium release. [The cardiovascular and urinary systems.] - The kidneys help regulate the acid-base and water-salt balances of the blood and interstitial fluid. - Erythropoietin, a hormone produced by the kidneys, stimulates red blood cell production. Quiz extras: coagulation contributes to homeostasis by keeping blood in the vessels A person who cannot produce the enzyme adenosine deaminase may develop: **4.1 Types of Tissues (COOKED 4)** - Connective tissue- binds and supports body parts - Muscular tissue- moves the body and its parts - Nervous tissue-conducts nerve impulses - Epithelial tissue- covers body surfaces; lines body cavities **4.2 Connective Tissue Connects and Supports** ***Connective Tissue Components*** - Specialized cells, ground substances, and protein fibers - Ground substance- noncellular material between the cells - Varies in consistency from solid (bone) to fluid (blood) Three types of protein fibers - Collagen fibers- flexible and strong - Reticular fibers- thin, highly branched collagen fibers - Elastic fibers- contain elastin, a protein that stretches and recoils **Fibrous Connective Tissue** - Comes in two main forms: loose and dense - Both contain fibroblasts separated by matrix (ground substance and fibers ***Loose fibrous connective tissue*** - includes areolar connective tissue, reticular connective tissue, and adipose tissue (supports epithelium and many internal organs) ***Dense fibrous connective tissue*** - found in tendons (connect muscles to bones) and ligaments (connect bones to bones) - Contains densely packed collagen fibers ***Adipose tissue (loose)*** - Very little extracellular matrix - Adipocytes- cells filled with liquid fat - Function in energy storage, insulation, and cushioning - Found primarily under the skin and around some organs **Supportive Connective Tissue** - Two major types- cartilage and bone - Functions in structure, shape, protection, and leverage for movement - Cartilage is more flexible than bone because it lacks mineralization of the matrix **Cartilage** - Chondrocytes and chondroblasts- cells that lie in small chambers called lacunae - Matrix is solid but flexible - Lacks a direct blood supply, so heals slowly Three types, distinguished by the type of fiber found in the matrix - Hyaline cartilage- fine collagen fibers (found in the tip of the nose, ends of long bones and the fetal skeleton) - Elastic cartilage- lots of elastic fibers. (found in the outer ear) - Fibrocartilage- strong collagen fibers. (Found in the disks between vertebrae) **Bone** The most rigid connective tissue - Matrix is made of collage and calcium salts - Salts surround protein fibers, which provide elasticity and strength (steel rods in reinforced concrete) - Compact and spongy are types of bone tissue. - Cells called osteoblasts and osteoclasts form the matrix in bone tissue Compact bones make up the shafts of long bones. - Consists of cylindrical structural units called osteons - The central canal contains blood vessels and nerves - Bone cells are in lacunae Spongy bone is inside the end of long bones - Lighter than compact bone, but strong **Fluid Connective Tissue 1** - Two types of fluid connect tissue: blood and lymph ***Blood and lymph*** Cooked 6 covers this Though lymph contains wbcs **4.3 Muscular Tissue Moves the Body** **Muscular Tissue** - Specialized to contract - Cells are called muscle fibers - Skeletal, smooth, and cardiac **Skeletal Muscle** - Attached to the skeleton by tendonds - Contraction moves the skeleton - Voluntarily controlled - Muscle fibers are very long; can run the entire length of the muscle - Have multiple nuclei - Straited, or striped, in appearance **Smooth Muscle** - No striations - Spindle-shaped cells with one nucleus - Involuntarily controlled - Found in the walls of viscera **Cardiac Muscle** - Found only in the walls of the heart - Striated - Involuntarily controlled - Single nucleus - Cells are connected by intercalated disks **4.4 Nervous Tissue Communicates** **Nervous Tissue** - Consists of neurons and neuroglia - Sensory input, integration, and motor output. **Neurons** - Dendrites, a cell body, and an axon - Dendrites carry the information toward the cell body - The cell body contains the nucleus and other organelles - Axon conducts nerve impulses away from the cell body - Some axons are covered in myelin, a fatty substance Nerves- bundles of axons traveling to and from the brain and spinal cord **Neuroglia** - Outnumber neurons 9 to 1 - Take up more than half the volume of the brain - Main function is to support and nourish neurons **4.5 Epithelial Tissue Protects** - Made of tightly packed cells - Lines body cavities, covers body surfaces, and is found in glands - Anchored by a basement membrane on one side and is free on the other side - Named for the number of cell layers and the shape of the cells - Simple vs stratified; squamous, columnar, or cuboidal **Simple epithelia** ***Simple squamous epithelium*** - Single layer of flattened cells - That is, found in the lungs, where it functions in gas exchange ***Simple cuboidal epithelium*** - Single layer of cube-shaped cells ***Simple columnar epithelium*** - Single layer of column-shaped cells ***Pseudostratified columnar epithelium*** - Because of the location of the nuclei, it appears stratified but every cell touches the basement membrane - Often has cilia, which moves mucus across its surface ***Gland*** - One or more cells that make and secrete a product - Two types: exocrine and endocrine - Exocrine glands secrete into ducts - Endocrine glands secrete into blood stream; have no ducts **Stratified Epithelia** - Several layers of cells ***Stratified Squamous epithelia*** - Forms the outer layer of the skin and lines the mouth, esophagus ***Transitional epithelia*** - Cells change shape in response to tension (cuboidal to squamous) - Found lining in the urinary bladder **4.6 Organ Systems, Body Cavities, and Body Membranes** Organs and cavities are lined with membranes, many of which secrete fluid **Anatomical Terms** - Ventral or anterior refers to the front - Dorsal or posterior means toward the back - Superior means toward the head - Inferior means toward the feet Some are relative to other body parts - Something that is medial is closer to the midline of the body - Lateral, away from the midline When referring to an appendage like an arm or a leg - Proximal means closer to the trunk of the body - Distal means away from the trunk **Organ Systems** - Some organs are involved in the function of more than one organ system - For example, the pancreas plays a role in the endocrine and digestive systems - Other structures and glands also contribute to the operation of organ systems **Body Cavities** - Two main cavities: dorsal and ventral ***Ventral cavity (coelom in early development)*** - Contains the thoracic, abdominal, and pelvic cavities - The diaphragm separates the thoracic and abdominal cavities - The thoracic cavity contains the lungs and the heart - The abdominal cavity contains the stomach, liver, spleen, pancreas, gallbladder, and most of the small and large intestines - The pelvic cavity contains the rectum, the urinary bladder, the internal reproductive organs, and the rest of the small and large intestines - Males have an external extension of the abdominal wall called the scrotum, which contains the testes ***Dorsal cavity*** - Contains the cranial cavity and vertebral canal **Body Membranes** - Line cavities and the internal spaces of organs and tubes that open to the outside - Four types: mucous, serous, and synovial membranes and the meninges ***Mucous membranes*** - Line the tubes of the digestive, respiratory, urinary, and reproductive systems - Composed of epithelium overlying loose fibrous connective tissue - Contains goblet cells that secrete mucus ***Serous membranes*** - Line closed cavities (not open to the environment) and cover the surface of the organs contained within - That is, pleurae line the thoracic cavity and cover the lungs - That is, pericardium forms the pericardial sac and covers the heart - That is, double layer of peritoneum, called mesentery, lines the abdominal cavity and covers its organs ***Synovial Membranes*** - Composed only of loose connective tissue - Line freely moveable joints - Secrete synovial fluid for lubrication ***Meninges*** - Composed only of connective tissue - In the dorsal cavity (protects the brain and spinal cord) - Meningitis- inflammation of the meninges **4.7 Integumentary System** - Includes skin and accessory organs such as hair, nails, and glands Functions: - Protects underlying tissue from trauma, pathogen invasion, and water loss - Helps regulate body temp - Contains sensory receptors, such as touch and temp receptors - Makes us aware of our surroundings Contains all 4 tissue types - Skin has two main regions: the epidermis and the dermis - Under the skin there is a subcutaneous layer (hypodermis) - The subcutaneous layer is between the skin and underlying structures, such as muscle or bone **Epidermis** - Thin, outermost layer of the skin - Stratified squamous epithelium - Stem cells that produce new epidermal cells are in the deepest layer - If an injury destroys the stem cells, skin needs to be replaced - Autograft- from another area of the body - Allograft- from another person ***Cells of the Epidermis*** Keratinocytes- in the upper layers of epidermis - Dead and filled with keratin - Forms a waterproof barrier Langerhans cells - A type of white blood cell Melanocytes - Product melanin - Produces skin color and protects from UV light - People have the same number of melanocytes, but the amount of melanin produced varies Other contributors to skin color: carotene and hemoglobin - Epidermal cells produce vitamin D when exposed to UV rays - Vitamin D is important in the regulation of calcium and phosphorus levels in the body **Skin cancer** - Caused by ultraviolet rays from the sun ***Basal cell carcinoma*** - Cancer of epidermal stem cells - Most common type of skin cancer; easily curable ***Melanoma*** - Cancer of melanocytes - Extremely serious **The Dermis** - Thick, inner layer of the skin - Made of dense fibrous connective tissue - Contains collagen and elastic fibers for strength and elasticity - Contains blood vessels, sensory receptors, and glands - Sensory receptors are specialized for touch, pressure, pain, heat, and cold **The Subcutaneous Layer** - Technically not part of the skin - Composed of loose connective tissue and adipose tissue - Stores energy, insulates, and protects **Accessory Organs of the Skin** ***Nails*** - Nails offer a protective covering of the digits (fingers and toes) - Nails grow from the nail root to cover the nail bed - The cuticle covers the nail root - Lunula- white half moon shape at the base ***Hair*** - Hair follicles- epidermal structures that surround the hair itself - Hair shaft- the portion of hair protruding from the skin - The color of hair comes from melanin; as melanocytes age, they produce less pigment and hair turns gray - Arrector pili muscles- attached to the hair follicle - Can contract, which creates goosebumps ***Oil Glands (sebaceous glands)*** - Produce sebum, which softens the hair and skin - Also retards bacterial growth - Acne-inflammation of the sebaceous glands ***Sweat glands (sudoriferous glands)*** - In the dermis, their ducts open onto the skin surface - Help to regulate body temperature **4.8 Homeostasis** - Relatively constant internal environment - Blood glucose, ph, body temp - If conditions vary too much, illness results **The Internal Environment** - Blood and interstitial fluid - Blood delivers oxygen and nutrients to the tissues and carries away co2 and waste - Interstitial fluid surrounds body cells: substances are exchanged through it - Body systems work together to keep these substances within the range or normalcy **Body Systems and Homeostasis** The nervous and endocrine systems coordinate the other organ systems - The nervous system is faster, but the effects of the endocrine system last longer - The Endocrine system secretes hormones-chemical messengers that travel in blood **Negative Feedback** - The primary mechanism used in the body - Two components: a sensor and control center - The output of the system turns down, or off, the production - That is, how a furnace works - Temperature regulation **Positive Feedback** - Brings about a change in the same direction as the original stimulus - Childbirth: the fetus's head pushes against the cervix, which stimulates signals that are sent to the brain - The brain then secretes the hormone oxytocin, which causes stronger contractions - This causes more oxytocin to be released - Childbirth stops the positive feedback - Can be harmful in some situations (fever)