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Chapter 18
Arteries, Veins, and Capillaries
| Term | Definition |
|---|---|
| Capillaries | exchange system, smallest blood vessels |
| Lumen | central space of blood vessels (tunica intima, tunica media, tunica externa |
| Arteries | much thicker tunica media, no valves |
| Elastic Artery | conducting arteries, largest in diameter, does not change in diameter in response to vasomotor nerves |
| Muscular Artery | distributing arteries, intermediate diameter, well developed tunica intima with many layers of smooth muscle, changes in diameter in response to vasomotor nerves |
| Arterioles | small arteries |
| Vasomotor Nerves | control constriction and dilation of blood vessels, vasoconstriction and vasodilation, impact blood flow |
| Metarterioles | smallest of arterioles, feed capillary beds most tissues |
| Precapillary Sphincters | tiny rings of smooth muscle at the entrance of capillaries, regulate flow into capillary beds, impact blood flow |
| Atherosclerosis | buildup of plaques within tunica intima, forms in areas where blood flow changed direction, plaque to blood = clots forming and blocks blood flow to an area |
| Artery functions | blood flow, monitoring blood pressure, monitoring chemical concentrations of blood |
| Baroreceptors | pressure receptors (aorta and carotid artery) |
| Chemoreceptors | chemical receptors (detect oxygen, carbon dioxide, and hydrogen ion concentrations of blood) |
| Veins | thinner walls, fewer elastic fibers, less smooth muscle, larger lumens than arteries, has valves |
| Venules | smallest veins, drains blood from capillary beds |
| Postcapillary Venules | endothelium and connective tissue (tunica intima) |
| Venous Valves | present in many veins, extensions of tunica intima, overlap to prevent backflow of blood, found in legs, where gravity opposes blood returning to heart |
| Arterial Anastomoses | found in organs like the heart, brain, and around joints, oxygen deprived tissues release chemical agents |
| Angiogenesis | forms new blood vessels |
| Venous Anastomoses | most common type of anastomoses in body, connects neighboring veins and creating web-like patterns under skin |
| Arteriovenous Anastomoses | enable artery to empty directly into vein without capillary bed, found in skin and fetal circulation |
| Hemodynamics | physiology of blood flow |
| Blood Pressure | outward force that the blood exerts on the walls of blood vessels, highest in systemic arteries, lowest in systemic veins |
| Pressure Gradient | more pressure = more blood flow |
| Resistance | more resistance = less blood flow, anything that hinders blood flow through vasculature, most resistance away from heart |
| Velocity | flow determined by cross-sectional area of vessel, fast flow in large arteries, slow flow in capillaries |
| Cardiac Output | CO + peripheral resistance determine pressure gradient that drives circulation, directly proportional |
| Increase Cardiac Output | sympathetic nervous system, caffeine intake |
| Decrease Cardiac Output | parasympathetic nervous system, drugs that block sympathetic nervous system |
| Blood Volume | related to amount of water in blood, directly proportional relationship, offset by vessel compliance, decrease compliance = increase in blood pressure |
| Vessel Compliance | vessel ability to stretch |
| MAP | mean arterial pressure, average pressure in systemic arteries during an entire cardiac cycle, |
| MAP Equation | (diastolic pressure + 1/3 pulse pressure) (pulse pressure = systolic - diastolic pressure) |
| Systolic and Diastolic Pressure | represent pulsations of blood pressure caused by heart contraction and relaxation, decrease due to reduction of blood volume in capillaries |
| Venus Return | pressure decline continues in capillary beds, pressure drops in veins, low pressure = little driving force to propel back to heart |
| Skeletal Muscle Pumps | assist venous return to heart, muscle surrounds deeper veins of limbs, muscle squeeze limbs and push blood toward heart |
| Respiratory pump | helps move blood through veins of thoracic and abdominopelvic cavities, driven pressure changes in thoracic cavity during respiration |
| Varicose Veins | dilated, bulging, hardened veins (hemorrhoids) |
| Baroreceptor Reflex | specialized mechanoreceptors in aortic sinus and ceratoid sinus, protection from sudden changes in blood pressure, negative feedback loop |
| Valsalva Maneuver | raises blood pressure in thoracic cavity and reduces venous return to heart, |
| Circulatory Shock | circulatory system fails to provide enough blood flow to tissues and organs |
| Vasodilation | widening of blood vessels, increases blood flow and lowers blood pressure |
| Vasoconstriction | narrowing of blood vessels |
| Anaphylactic Shock | severe allergic reaction |
| Septic Shock | bacterial infection of blood |
| Tissue Perfusion | blood flow to tissues though capillary beds surrounded by pericytes |
| Pericytes | cells that wrap around capillaries and venules, contractile filaments that regulate blood flow |
| Capillary Exchange | movement of gases, nutrients, ions, and wastes between capillaries and tissues |
| Capillary Beds Mechanisms | diffusion and osmosis through gaps and fenestrations, diffusion through endothelial cell membranes, transcytosis |
| Transcytosis | endocytosis (going in) and exocytosis (going out) |
| Continuous Capillaries | majority, endothelial cells joined by tight junctions (most selective), movement occurs via diffusion and transcytosis, blood-brain barrier composed of modified continuous capillaries |
| Fenestrated Capillaries | epithelial cells contain fenestrations, slightly less selective, allow for more rapid diffusion to take place, found in places where substances need to quickly enter/exit the capillary (endocrine glands, kidneys, small intestines) |
| Sinusoidal Capillaries | sinusoids, least selective, irregular basal lamina, contain very large pores in the endothelial cells, movement of large substances (liver, spleen, lymphoid, organs, and bone marrow |
| Microcirculation | flow of blood that takes place within capillary beds (true capillaries and central vessels) |
| Autoregulation | tissue perfusion largely driven by arterial blood pressure, tissues adjust their own blood flow |
| Myogenic Mechanism | functions to maintain local tissue perfusion at constant level |
| Metabolic Controls | Respond to chemical levels in interstitial fluid around capillaries |
| Filtration | movement of fluid by force such as pressure or gravity, this is the main driver in capillary pressure |
| Hydrostatic Pressure | drives water out of capillary, force a fluid exerts on the walls of its containers, higher pressure in arterioles than venules |
| Osmotic Pressure | draws water into capillary, created by large proteins in blood that can't leave capillary |
| Colloid Osmotic Pressure COP | difference in capillary OP and interstitial OP (attracts water) |
| Net Filtration Pressure | difference between HP and COP, if Hp is higher than COP = water forced out (filtration), if COP is higher than HP = water drawn in (absorption) |
| Cerebrovascular Accident (CVA) | stroke, damage to brain due to blood flow disruption, clot blocking on to main arteries to brain, |
| Vein Grafting | vein removed and grafted to an artery to bypass blockage; part of a vein is removed and is used to detour around a blockage in another blood vessel, great saphenous vein is used because it is superficial and easily accessible (largest vein in leg) |
| Hepatic Portal System | direct blood flow to liver, where chemicals are broken down and removed |
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