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A&P 2: Chapter 21

Anatomy & Physiology 2 Lamar University Lecture-Armacost
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Circulatory System (components)
fluid (blood), pump (heart), and tubes (blood vessels)
Arteries/Arterioles
these carry blood away from the heart, towards the body, and they differ in size and function
Elastic Arteries
arteries/arterioles: have a large diameter
Muscular Arteries
arteries/arterioles: have a medium diameter
Arterioles
arteries/arterioles: have a small diameter
Tunica Interna
arterial wall: inner lining of epithelium and elastic fibers
Tunica Media
arterial wall: elastic fibers and smooth muscle fibers, and thicker layer of smooth muscle fibers than in veins
Tunica Externa
arterial wall: outer lining of elastic and collagen fibers
Elastic Arteries
large diameter, located near the heart, has many elastic fibers in tunica media, and functions as pressure reservoir
Pressure Reservoir
when ventricle of heart contracts, wall of elastic artery expands to accommodate influx of blood, when ventricle relaxes, vessel wall rebounds, thus providing a more continuous flow of blood
Muscular Arteries
medium diameter, located further from the heart, and has many smooth muscle fibers in tunica media
Arterioles
small diameter, resistance vessels, and regulates blood flow by regulating resistance
Resistance
is an opposition to blood fow, mainly due to friction between blood and vessel wall; contraction of relaxation of smooth muscles in arterioles effects diameter of vessel, thus friction, thus this
Veins/Venules
these return blood to heart from body tissures (deoxygenated blood), and they differ in size and function
Venules
returns blood to heart from body tissues, has a small diameter
Veins
returns blood to heart from body tissues, has a large diameter; tunica intera and tunica media thinner than in arteries
Venous Valves
many veins have valves in prevent the back-flow of blood
Capillaries
small diameter, capillary wall consists of single layer of endothelial cells and a basement membrane, and function as exchange vessels; gases and small molecles move btwn blood and interstitial fluid of body tissues
Continuous Capillary
plasma membranes of endothelial cells are continuous, only gases and small molecules can pass across capillary wall, and is found in skeletal muscle, smooth muscle, connective tissue, and lungs
Fenestrated Capillary
plasma membranes of endothelial cells have small pores, large molecules can pass across capillary wall, and is found in kidneys, villi of sm. intestine, choroid plexuses of ventricles in brain, and some endocrine glands
Sinusoidal Capillary
plasma membranes of endothelial cells have large pores, large molecules and some cells can pass across capillary wall, and is found in bone marrow, liver, lymph, and some endocrine tissue
Capillary Exchange
exchange of gases and other substances btwn blood and interstitial fluid, across capillary walls
Diffusion
passive movement of individual molecules from an area of high concentration to an area of low concentration, until equilibrium is reached; driven by a concentration gradient
Transcytosis
active movement of molecules across endothelial cells of capillary wall via pinocytosis and exocytosis; active, driven by cellular energy
Bulk Flow
passive movement of large numbers of molecules from an area of high pressure to an area of low pressure; passive, driven by pressure gradient
Filteration
movement of fluid and associated molecules from blood to interstitial fluid; occurs at arterial end of capillary where blood pressure is higher than osmotic pressure of interstitial fluid; blood hydrostatic pressure (BHP) pushes molecules from blood
Reabsorption
movement of fluid and associated molecules from interstitial fluid to blood; occurs at venous end of capillary where osmotic pressure of interstitial fluid if higher than blood pressure; blood colloid osmotic pressure (BCOP) pulls fluids into capillaries
Hemodynamics
are the forces involved in blood flow
Blood Flow
volume of blood passing through a tissue per unit time (mL/min)
Blood Flow (factors)
this through a particular tissue depends on 2 factors: differences in blood pressure throughout the body, and differences in vascular resistance throughout the body
Blood Pressure
hydrostatic pressure exerted by blood on walls of vessels, generated by contraction of ventricles, and drops with increasing distance from heart
Vascular Resistance
is an opposition to blood flow due to friction between blood and vessel wall
Viscosity of Blood
vascular resistance factor: resistance increases as friction increases, is relatively constant, and has a minor effect
Length of Blood Vessel
vascular resistance factor: resistance increases as length increases, is relatively constant, and has a minor effect
Diameter of Blood Vessel
vascular resistance factor: resistance increases as diameter decreases, is not constant (contraction and relaxation of smooth muscles in vessel walls), and has a major effect
Venous Return
includes 3 mechanisms that return blood to the heart
Pressure Generated
a venous return: by contraction of left ventricle; but venous pressure is so low that it can barely overcome gravity
Skeletal Muscle Pump
a venous return: contraction of skeletal muscles in limbs generates pressure on veins, and valves in veins play an important role in preventing back-flow of blood
Respiratory Pump
a venous return: inhalation decreases pressure in thoracic cavity but increases pressure in abdominal cavity and on abdominal veins