| Term | Definition |
|---|
| arteries | the efferent vessels of the cardiovascular system (carry blood away from the heart). aka resistance vessels of the cardiovascular system because they have a relatively strong tissue structure that resists a high blood pressure. more muscular than veins, retain their circular shape. they are divided into three categories by size |
| veins | afferent vessels (carry blood back to the heart). relatively thin walled and flaccid. since they are distant from the ventricles of the heart, they are subjected to relatively low blood pressure, they have a steady flow of blood and collapse when empty. |
| capillaries | aka. exchange vessels of the cardiovascular system, microscopic, thin-walled vessels that connect the smallert arteries to the smallest veins. composed of an endothelium and basement membrane. They are scarce in tendons and ligaments and are absent from epithelia, the cornea/lens of the eye, and most cartilages. |
| conducting arteries | aka elastic or large. they are the biggest. The aorta, common carotid and subclavian ateries are prime examples. There is a very thin layer of elastic fibers called the internal elastic lamina at the border between the intima and media. The tunica media consists of 40-70 layers of elastic sheets, perforated by alternating sheets of smooth muscle, collagen, and elastic fibers. A thin external elastic lamina at the border between the media and the externa. The tunica externa is thick and well supplied with vasa vasorum. These arteries expand during ventricular systole to receive blood and reduce systolic stress subjected to smaller blood vessels, and recoil during diastole to prevent blood pressure from dropping too low. |
| distributing arteries | aka muscular or medium arteries, examples include the brachial, femoral, renal, and splenic arteries. up to 40 layers of Smooth muscle consists of about 3/4 of the wall thickness, and the internal and external elastic laminae are often thick. |
| Resistance arteries | aka small, and too variable in numbers and location to be named.consists of about 25 layers of smooth muscle and relatively little elastic tissue. tunica media is thiker in proportion to the lumen than to that of larger arteries |
| arterioles | the smallest of the resistance arteries. they consist of one to three layers of smooth muscle, they have very little tunica externa. They act as the most significant point of control over peripheral resistance and blood flow because 1) are located on proximal sides of the capillary beds, 2) greatly outnumber any other class of arteriees and provide many control points, 3) and the are more muscular in proportion to their diameters than any other class of blood vessels...these provide them with a high capability of vasomotion |
| metarterioles | short vessels that link arterioles and capillaries, they contain precapillary sphincters |
| precapillary sphincters | individual muscle cells spaced a short distance from each other in metarterioles, as opposed to having a continuous tunica media, each of these encircle the entrance to one capillary. Constriction of these reduces or shuts off the blood flow through their respective capillaries and diverts blood to other tissues or organs |
| carotid sinuses | pressure sensors that respond to changes in blood pressure around the area of the internal carotid artery just above the branch point. They have a relatively thin tunica media and an abundance of glossopharyngeal nerve fibersin the tunica externa. A rise in blood pressure stretches the thin media and stimulates these nerves. THe glossopharyngeal nerve then transmits signals to the vasomotor and cardiac centers of the brainstem. THe brainstem responds by lowering the heart rate and dilating the blood vessels |
| carotid bodies | they are located near the branch of the common carotid arteries, innervated by the sensory fibers of the vagus and glossopharyngeal nerves, act as chemoreceptors that monitor changes in the blood composition. transmit signals to the brainstem respiratory centers, which adjust breathing to stabalize the blood pH and its CO2 and 02 levels |
| aortic bodies | one to three chemoreceptors located in the aortic arch near the arteries, structurally and functionally similar to carotid bodies |
| continuous capillaries | one of the three types of capillaries which occurs in most tissues. Their endothelial cells are held together by tight junctions, which forms an uninterrupted tube. It contains a thin basal lamina, some have intercellular clefts (the brain lacks intracellular clefts), and some have pericytes |
| basal lamina | thin-protein carbohydrate layer, surrounds the endothelium and separates it from the adjacent connective tissue |
| intercellular clefts | narow divisions of the endothelial cells, small solutes such as glucose can pass through, but most elements are held back |
| pericytes | cells found in some of the continuous capillaries that lie external to the endothelium. they have elongated tendrils that wrap around the capillary. THey contain some contractile proteins that are able to regulate blood flow through the proteins. They can also differentiate into endothelial and smooth muscle cells and thus contribute to vessel growth and repair. |
| filtration pores | wholes in the endothelial cells of some continuous capillaries. They allow for the rapid passage of ,p;ecules through the capillary wall, but they still retain blood cells and platelets in the blood strea, |
| fenestrated capillaries | on of the three types of capillaries which is riddled with holes. They are important in organs that engage in rapid absorbtion and filtration-- the kidneys, endocrine glands, small inestine, and the choroid plexuses of the brain |
| sinusoids | aka discontinuos capillaries, these are irregular blood-filled spaces in the liver, bone marrow, spleen, and some other organs. they are twisted tortuous passageways that conform to the shape of the surrounding tissue. The endothelial cells are separated by wide gaps with no basal lamina, often the cells have large fenestrations which allows blood cells and proteins to pass through |
| capillary beds | organized networks of capillaries. THere are anywhere from 10-100 capillaries supplied by a single metarteriole |
| thoroughfare channel | beyond the origins of the capillaries, the metarteriole continues leading directly to the venule |
| postcapillary venules | the smallest of the veins. they receive blood from the capillaries or from the distal ends of the thoroughfare channels. their tunica interna have only a few fibroblasts around it, often are surrounded by pericytes, are often even more porous than capillaries. Most leukocytes leave the blood stream by way of the venules. |
| muscular venules | receive blood from the postcapillary venules. they have a tunica meia of one or two layers of smooth muscle, and a thin tunica externa |
| medium veins | these types of veins include many of the veins with individual names. have a tunica externa with an endothelium, basement membrane, loose connectiove tissue, and sometimes a thin internal elastic lamina. The tunica media is much smaller than the medium arteries, it exhibits bundles of smooth muscles, but not a continuous muscular layer. The muscle is interrupted by regions of collagenous, reticular, and elastic tissue. The tunica externa is relatively thick. many contain venous valves directed toward the heart |
| venous valves | infoldings of the tunica interna that meet in the middle of the lumen which prevent gravity from preventing blood to return to the heart |
| skeletal muscle pump | the mechanism which the muscles surrounding a vein contacts and forces the blood through the valves |
| venous sinuses | veins with especially thin walls, large lumens, no smooth muscle, and not capable of vasomotion. includes the dural sinus and the coronary sinus |
| large veins | diameters greater than 10 mm, have a relatively thin tunica me media with only a moderate amount of smooth muscle, the tunica externa is the thickest layer and contains longitudinal buncles of smooth muscle. some smooth muscle is found in all three layers of these veins |
| flow | the amount of blod flowing through an organ, tissue, or blood vessel in a given time (ex. mL/min). one of the ways to express blood supply to a tissue |
| perfusion | the flow per given volume or mass of tissue (ex. mL/min/g |
| hemodynamics | the physical principles of blood flow, based primarily on pressure and resistance. The greater the pressure difference between two points, the greater the flow; the greater the resistance, the less the flow |
| blood pressure | force that blood exerts against a vessel wall |
| systolic pressure | the peak arterial BP attained during ventricular contraction (generally about 120 mmHg) |
| diastolic pressure | the minimum arterial BP occuring during the ventricular relaxation between heartbeats (generally about 75) |
| pulse pressure | the difference between systolic and diastolic pressure. an important measure of the stress exerted on the small arteries by the pressure surges generated by the heart |
| mean arterial pressure | a measure of stress on the blood vessels. the mean pressure you would obtain at several random intervals. the best estimate of this value is to add 1/3 of the pulse pressure to the diastolic pressure. this value will vary with the influence of gravity |
| hypertension | a chronic resting blood pressure higher than 140/90. This, among other things, can weaken the small arteries and cause aneurysms, promotes the development of atherosclerosis. |
| hypotension | a chronic low resting BP. this may be a result of blood loss, dehydration, anemia...or factors experienced by people approaching death |
| pulsatile | a description of the blood flow in the arteries. blood rushes out of the aorta, slows down the farther away from the heart it gets, flows with pulsation |
| peripheral resistance | the opposition to flow that the blood encounters in vessels away from the heart |
| vasoconstriction | the narowing of a vessel, one of the significant ways of controlling the peripheral resistance |
| vasodilation | the widening of the a vessle, one of the significant ways of controlling the peripheral resistance |
| laminar flow | the term for blood flow in the vessel. it flows in "layers"; faster near the center where it encounters less friction, and slower near the walls where it drags against the vessel |
| vasomotion | a quick and powerful way to alter blood pressure and flow. Three methods of control: local, neural, and hormonal mechanisms |
| autoregulation | the ability of tissues to regulate their own blood supply. According to the metabolic theory pertaining to this, if a tissue is inadequately perfised, it becomes hypotoxic and its metabolites accumulate. The waste products (CO2, lactic acid...) accumulate and stimulate vasodilation. |
| vasoactive chemicals | substances that stimulate vasomotion (histamine, bradykinin...). They are produced in trauma, inflammation, and excercise. |
| reactive hyperemia | an increase above the normal level of blood flow. |
| angiogensis | the growth of new blood vessels. a method uses by hypoxic tissue to increase its own profusion. Evident in the regrowth of the uterine lining, development of a higher density of blood capillaries in the muscles of well-conditioned athletes, and the regrowth of arterial bypasses around obstructions in the coronary circulation. |
| vasomotor center | found in the medulla oblongata. It exerts sympathetic control over blood vessels throughour the body by the remote control of the autonomic nervous system. |
| baroreflex | an autonomic negative feedback respinse to changes in blood pressure. Changes are detected by the carotid sinuses and messages are received at the brain stem by the glossopharyngeal nerve fibers. When BP rises, the signaling rate rises which inhibits the sympathetic cardiac and vasomotor neurons and reduces sympathetic tone, and it excites the vagal fibers to the heart...which reduces the heart rate and cardiac output, dilates the arteries and veins, and reduces the blood pressure. The opposite results occur in order for a low pressure in attempt to raise BP back to normal. This process is very important for short-term regulation. |
| chemoreflex | an autonomic response to changes in blood chemistry, especially in pH and concentrations of O2 and CO2. Initiated by the aortic bodies and carotid bodies. the primary role is to adjust respiration to changes in blood chemistry, and a secondary role to stimulating vasomotion. Hypoxemia, hypercapnia, and acidosis (low BP) stimulate the receptors and induce widespread vasoconstriction. This increases BP, thus increasing the perfusion of the lungs and the rate of gas exchange...simultaneously they stimulate breathing as well |
| medullary ischemic reflex | an autonomic response to a drop in perfusion of the brain. in seconds, the cardiac and vasomotor centers of the medulla oblongata send sympathetic signals that induce heart race and force of contraction, as well as widespread vasoconstriction. these actions raise BP and restore perfusion to the brain. |
| angiotensin II | a vasoconstrictor hormone which raises the blood pressure |
| aldosterone | "salt-retaining hormone" which promotes the retention of Na+ by the kidneys. na+ retention promotes water retention, which promotes a higher blood volume and pressure |
| atrial natriuretic peptide | a hormone secreted by the heart, antagonizes aldosterone. It increases Na+ excretion by the kidneys, which therefore reduces the blood volume and blood pressure...as well as a generalized vasodilator effect |
| antidiuretic hormone | a hormone that promotes water retention. in high concentrations is is also a vasoconstrictor. both of these effects raise the blood pressure |
| epinephrine and norepinephrine | sympathetic catecholamine that bind to alpha-adrenergic receptors on the smooth muscle of most blood vessels, this stimulates the muscle to contract, producing vasoconstriction and raising the blood pressure. in the coronary blood and blood vessels of the skeletal muscles, these chemicals bind to beta-adrenergic receptors and causes vasodilation, which increases blood flow to the myocardium and muscular system during excercise |
| capillary exchange | two-way movement of fluid across capillary walls that exchanges occur between the blood and surrounding tissues. chemicalls given off to serve the perivascular tissues include oxygen, organic nutrients, and hormones. chemicals taken up by the capillaries include CO2 and other wastes. many chemicals have a two-way traffic between the blood and connective tissue. Three routes that chemicalls can pass through the capillary wall 1) endothelium cell cytoplasm, 2) intracellular clefts between the endothelial cells, 3)filtration porese of the fenestrated capillaries |
| diffusion | important mechanism of exchange. glucose and oxygen and more concentrated in the systemic blood than in the tissue fluid and need to spread to the blood, and wastes are more concentrated in the in the tissue fluid, and needs to spread into the blood |
| transcytosis | a process in which endothelial cells pick up droplets of fluid on one side of the plasma membrane by pinocytosis, transport the vesicles across the the cell, and discharge the fluid on the other side by exocytosis |
| hydrostatic pressure | physical force exerted against a surface such as a capillary wall, by a liquid. ex. blood pressure |
| colloid osmotic pressure | the portion of the osmotic pressure due to protein, opposes the forces of hydrostatic pressure |
| oncotic pressure | the difference between the colloid osmotic pressure of blood and of tissue fluid. tends to draw water into the capillary by osmosis, opposing hydrostatic pressures |
| net filtration pressure | the product of the opposition of the net hydrostatic pressure and oncotic pressure |
| net reabsorption pressure | found at the venous end of the capillary because osmotic pressure voerrides filtration pressure. inward force causing the capillary to reabsorb fluid at this end= 7mmHg. differences in this pressure and filtration pressure are because of:*more branches of capillaries towards the venous end, *about twice the diameter at the venous end. |
| solvent drag | the process of "dragging" chemicals dissolved in water through the bloodstream, and pass through the capillary wall if they are not too large |
| glomeruli | capillary networks in the kidneys that are devoted entirely to filtration, have little or no reabsorption |
| venous return | the flow of blood back to the heart. achieved by 5 mechanisms: the pressure gradient, gravity, skeletal muscle pump, thoracic (respiratory) pump, and cardiac suction ( caused by the closing of the AV valve |
| central venous pressure | the pressure at the point where the venae cavae enter the heart. this pressure decreaseswhen the veins constrict and oppose flow, but when all veins constrict, the pressure increases because there is less "storage capacity" in the circulatory system |
| venous pooling | the accumulation of blood in the limbs because venous pressure is not high enough to override the weight of the blood and drive it upward, result of a person being still for a long time. |
| syncope | dizinessbecause the cardiac out put became so low and the brain is inadequately perfused; the result of people standing for long periods of time and excessive amounts of blood accumulating in the legs |
| hypertension | cardiovascular disease, major casue of heart failure, renal failure, and stroke. It damages the heart because it increases the afterload, which makes the ventricles work harder to expel blood. The myocardium enlarges up to a point, but eventually it becomes excessively stretched and can create lesions. It can strain the blood vessels and tear the endothelium. Aso, the arterioles of the kidney can thicken in response to stress, their lumens become narrower, and the renal blood flow declines. |
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