| 单词 | arteriole |
| 例句 | Small arteries and arterioles in the limbs also relax over the course of pregnancy, enhancing blood flow and cooling. How much heat is dangerous during pregnancy? 2023-09-27T04:00:00Z Blood capillaries are found beneath the dermis, and are linked to an arteriole and a venule. Fundamentals of Biology 2015-01-01T00:00:00Z By what factor did the radii of the arterioles constrict? College Physics for AP Courses 2015-08-12T00:00:00Z If ventilation is greater than perfusion, the arterioles dilate and the bronchioles constrict. Biology for AP Courses 2022-06-09T00:00:00Z The interlobar arteries, in turn, branch into arcuate arteries, cortical radiate arteries, and then into afferent arterioles. Anatomy and Physiology 2013-06-19T00:00:00Z The answer often lies in the smaller branches and twigs of the vascular system—arterioles and capillaries that deliver oxygen and nutrients to heart muscle. What Ails a Woman's Heart 2019-01-03T05:00:00Z An artery branching off into an arteriole, which branches into a capillary bed. Fundamentals of Biology 2015-01-01T00:00:00Z The pipes that carry blood to the brain – known as arterioles – can expand and contract to regulate blood flow. Sudden Death 2016-08-11T04:00:00Z Likewise, if ventilation is less than perfusion, the arterioles constrict and the bronchioles dilate to correct the imbalance. Biology for AP Courses 2022-06-09T00:00:00Z The afferent arterioles service about 1.3 million nephrons in each kidney. Anatomy and Physiology 2013-06-19T00:00:00Z By contrast, the deeper insulated fibres in the white matter affected by a covert stroke are supplied by single, smaller vessels called arterioles. Perspective: Silent, but preventable, perils : Nature : Nature Publishing Group 2014-06-24T04:00:00Z Video 3: Capillary and arteriole dilation in vivo Penetrating arteriole and primary capillary in Figure 3d in mouse somatosensory cortex in vivo responding to whisker pad stimulation. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z In second-impact syndrome, however, the arterioles malfunction, dilating and opening a flood that engorges the brain. Sudden Death 2016-08-11T04:00:00Z The major arteries diverge into minor arteries, and then smaller vessels called arterioles, to reach more deeply into the muscles and organs of the body. Biology for AP Courses 2022-06-09T00:00:00Z The afferent arterioles form a tuft of high-pressure capillaries about 200 µm in diameter, the glomerulus. Anatomy and Physiology 2013-06-19T00:00:00Z For example, is dilation of larger arterioles, induced by neuronal activity, sufficient to cause an increase in blood flow in smaller capillaries, or is vasodilation initiated at capillaries? Vascular biology: Brain vessels squeezed to death 2014-04-04T18:23:16.270Z This figure would be reduced somewhat if pial arteriole dilation significantly contributes to the flow increase. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z A prominent pathological feature of PH is accumulation of macrophages near the arterioles of the lung. [Research Articles] Blocking Macrophage Leukotriene B4 Prevents Endothelial Injury and Reverses Pulmonary Hypertension 2013-08-28T18:25:19.997Z As blood moves into the arteries, arterioles, and ultimately to the capillary beds, the rate of movement slows dramatically to about 0.026 cm/sec, one-thousand times slower than the rate of movement in the aorta. Biology for AP Courses 2022-06-09T00:00:00Z This is the only portal system in which an arteriole is found between the first and second capillary beds. Anatomy and Physiology 2013-06-19T00:00:00Z Klein adds that perhaps undue contraction of the arterioles, through stimulation by the blood-irritant, may also be a factor in causing arrest of circulation in the Malpighian corpuscles. A System of Practical Medicine by American Authors, Vol. I Volume 1: Pathology and General Diseases 2012-03-17T02:00:54.097Z Video 3: Capillary and arteriole dilation in vivo Penetrating arteriole and primary capillary in Figure 3d in mouse somatosensory cortex in vivo responding to whisker pad stimulation. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z When this sudden systemic arteriole spasm extends to the coronary vessels in a heart whose walls are diseased, a fatal attack of angina with the heart full of blood may be induced. New, Old, and Forgotten Remedies: Papers by Many Writers 2012-02-05T03:00:10Z In the arteries, the hydrostatic pressure near the heart is very high and blood flows to the arterioles where the rate of flow is slowed by the narrow openings of the arterioles. Biology for AP Courses 2022-06-09T00:00:00Z The efferent arteriole is the connecting vessel between the glomerulus and the peritubular capillaries and vasa recta. Anatomy and Physiology 2013-06-19T00:00:00Z Steurer writes: "As the kidneys are the great filters of the human system, I never neglected to examine them, and almost invariably found micrococci filling the arterioles and glomeruli." A System of Practical Medicine by American Authors, Vol. I Volume 1: Pathology and General Diseases 2012-03-17T02:00:54.097Z Whether blood flow is controlled solely by arteriole smooth muscle, or also by capillary pericytes, is controversial. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z The muscular layer varies from single scattered cells, in the arterioles, to bands of fibers making up the body of the vessel in the medium-sized arteries and veins. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z Throughout the cardiac cycle, the blood continues to empty into the arterioles at a relatively even rate. Biology for AP Courses 2022-06-09T00:00:00Z The glomerulus is a high-pressure capillary bed between afferent and efferent arterioles. Anatomy and Physiology 2013-06-19T00:00:00Z By prolonging the cardiac diastole and contracting the arterioles it allows the left ventricle to fill, restores the arterial tension, diminishes correspondingly the intravenous pressure, and promotes absorption. A System of Practical Medicine by American Authors, Vol. I Volume 1: Pathology and General Diseases 2012-03-17T02:00:54.097Z In vivo, when sensory input increases blood flow, capillaries dilate before arterioles and are estimated to produce 84% of the blood flow increase. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z It is readily understood how the maximum pressure falls as the periphery is approached, until in the arterioles the maximum and minimum pressures are about equal. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z Figure 31.20 Blood pressure is related to the blood velocity in the arteries and arterioles. Biology for AP Courses 2022-06-09T00:00:00Z This is a modified, smooth muscle cell lining the afferent arteriole that can contract or relax in response to ATP or adenosine released by the macula densa. Anatomy and Physiology 2013-06-19T00:00:00Z Vaso-motor nerve-paralysis, acting at the same time on the pulmonary artery and arterioles, and on other large arterial trunks, probably gives rise to the murmurs heard in them. A System of Practical Medicine by American Authors, Vol. I Volume 1: Pathology and General Diseases 2012-03-17T02:00:54.097Z Thus, capillaries dilate before the penetrating arteriole feeding them. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z The pressure then in these arterioles is practically the same as the diastolic pressure. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z The cortical radiate arteries branch into numerous afferent arterioles, and then enter the capillaries supplying the nephrons. Biology for AP Courses 2022-06-09T00:00:00Z Included in this vasodilation are the afferent arterioles supplying the glomerulus, resulting in increased GFR, and water loss by the kidneys. Anatomy and Physiology 2013-06-19T00:00:00Z Also in the earliest cases the multiplication or germination of the nuclei of the muscular coat of the arterioles was observed, with a corresponding increase in the thickness of the walls of these vessels. A System of Practical Medicine by American Authors, Vol. I Volume 1: Pathology and General Diseases 2012-03-17T02:00:54.097Z The faster dilation in capillaries compared to arterioles indicates that capillary dilation is not a passive response to a pressure increase produced by arteriole dilation. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z The arterioles are generally the seat of a moderate thickening of the intima and media, but it is not usual to find obliterating endarteritis. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z The branch that enters the glomerulus is called the afferent arteriole. Biology for AP Courses 2022-06-09T00:00:00Z This allows for the maintaining of muscle “tone” in smooth muscle that lines arterioles and other visceral organs with very little energy expenditure. Anatomy and Physiology 2013-06-19T00:00:00Z According to this, a state of spasm of the arterioles and capillaries causes the chill, while the fever is merely the rebound of functions held in abeyance during the chill. A System of Practical Medicine by American Authors, Vol. I Volume 1: Pathology and General Diseases 2012-03-17T02:00:54.097Z These mechanisms resemble those controlling arteriole dilation, and may reflect glutamate release activating the production of arachidonic acid and its derivatives in astrocytes or neurons. Capillary pericytes regulate cerebral blood flow in health and disease 2014-04-04T18:24:22.627Z The primary change is an increased tension in the arterioles which later leads to thickening of the coats of the vessels and to the other consequences of arterial disease. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z The branch that exits the glomerulus is called the efferent arteriole. Biology for AP Courses 2022-06-09T00:00:00Z When body temperatures drop, the arterioles constrict to minimize heat loss, particularly in the ends of the digits and tip of the nose. Anatomy and Physiology 2013-06-19T00:00:00Z In the one case there is a spasm of the arterioles causing what the French call "dead fingers," and in the other paralysis of the vasomotor system with venous congestion in the parts. Psychotherapy 2011-06-19T02:00:20.053Z Two great trunks, the aorta and pulmonary artery, leave the heart and divide again and again, until they become minute vessels to which the name of arterioles is given. Encyclopaedia Britannica, 11th Edition, Volume 2, Slice 6 "Armour Plates" to "Arundel, Earls of" If the narrowing of the arterioles is brought about by thickening due to arteriosclerosis, then it would seem a priori that such obliteration should cause a rise in pressure. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z Once the efferent arteriole exits the glomerulus, it forms the peritubular capillary network, which surrounds and interacts with parts of the renal tubule. Biology for AP Courses 2022-06-09T00:00:00Z It constricts the arterioles in the peripheral circulation, which reduces the flow of blood to the extremities and thereby increases the blood supply to the core of the body. Anatomy and Physiology 2013-06-19T00:00:00Z In vaso-motor paresis, and still more paralysis, the arterioles supplying the capillaries are widely dilated, and at the lowest blood pressure probably send more blood into the latter than in the normal state. On Snake-Poison: its Action and its Antidote Its first action on any of the body-tissues is upon unstriped muscle, so that the first consequence of its absorption is a contraction of the arteries and arterioles. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" Any agent which acts to produce thickening of the walls of the arterioles, narrowing their lumina, produces the same effect. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z Once the afferent arterioles are constricted, blood flow into the nephrons stops. Biology for AP Courses 2022-06-09T00:00:00Z The arterioles can also constrict or dilate, which varies their resistance, to help distribute blood flow to the tissues. Anatomy and Physiology 2013-06-19T00:00:00Z Albert followed it, watching as it passed into the pulmonary artery, tracing it out through the smaller vessels until it stopped squarely across a junction of two arterioles. Insidekick No other known drug has an equally marked action in contracting the arterioles. Encyclopaedia Britannica, 11th Edition, Volume 8, Slice 4 "Diameter" to "Dinarchus" Also the arterioles show extensive intimal thickening, fibrous in character, with occasional obliterating endarteritis. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z These again split to form arcuate arteries, from which cortical radiate arteries radiate out and branch into many afferent arterioles that enter the capillaries supplying the nephrons. Biology for AP Courses 2022-06-09T00:00:00Z Vascular shock occurs when arterioles lose their normal muscular tone and dilate dramatically. Anatomy and Physiology 2013-06-19T00:00:00Z The cells are fed and sustained by the circulation of the blood; they are reached from the smaller branching arteries by a network of minute, thread-like channels, sometimes called 'arterioles.' Solaris Farm A Story of the Twentieth Century Blood is brought to the tissues by arterioles, or the small terminations of the arteries, and is carried off from them by the veinlets, or the commencement of the veins. Special Report on Diseases of the Horse The diastolic pressure is determined by the tone in the arterioles and is under the control of the vasomotor sympathetic system. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z These again split to form arcuate arteries, from which cortical radiate arteries radiate out and branch into many afferent arterioles that enter the capillaries supplying the nephrons. Biology for AP Courses 2022-06-09T00:00:00Z One arteriole and an accompanying venule supply and drain one pulmonary lobule. Anatomy and Physiology 2013-06-19T00:00:00Z These arterioles are accompanied by the equally fine wires of the nervous system, closely connected with the brain centers. Solaris Farm A Story of the Twentieth Century Nævus.—A nævus is a collection of dilated capillaries, the afferent arterioles and the efferent venules of which often share in the dilatation. Manual of Surgery Volume First: General Surgery. Sixth Edition. It is after all in the arterioles and smaller arteries that the lesions of arteriosclerosis do the most damage. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z These again split to form cortical radiate arteries that radiate out and branch into many afferent arterioles that enter the capillaries supplying the nephrons. Biology for AP Courses 2022-06-09T00:00:00Z At the same time, the pulmonary arterioles that serve alveoli receiving sufficient ventilation vasodilate, which brings in greater blood flow. Anatomy and Physiology 2013-06-19T00:00:00Z A minute blood vessel connecting the arterioles with the venules; very minute blood vessels. Mother's Remedies Over One Thousand Tried and Tested Remedies from Mothers of the United States and Canada A dilated arteriole or a vein winding about among the capillaries may sometimes be detected. Manual of Surgery Volume First: General Surgery. Sixth Edition. In the smaller arteries and arterioles the arteriosclerotic process appears on superficial examination to be a different process from that in the aorta and large arteries, but the difference is only apparent. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z These again split to form arcuate arteries, from which cortical radiate arteries radiate out and branch into many afferent arterioles that enter the capillaries supplying the nephrons. Biology for AP Courses 2022-06-09T00:00:00Z In addition to muscle and connective tissue to support its structure, each villus contains a capillary bed composed of one arteriole and one venule, as well as a lymphatic capillary called a lacteal. Anatomy and Physiology 2013-06-19T00:00:00Z Almost immediately a benign animal magnetism pervaded the bosom of Payson Clifford, and from his bosom reached out through his arteries and veins, his arterioles and venioles, to the uttermost ends of his being. By Advice of Counsel The incompetence of the valves allows the pressure in the varicose veins to equal that in the arterioles, so that the capillary circulation is impeded. Manual of Surgery Volume First: General Surgery. Sixth Edition. It will be recalled that there is relatively much more muscle tissue in the arterioles than in the large arteries. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z It constricts the afferent arterioles, causing the flow of blood into the nephrons to stop. Biology for AP Courses 2022-06-09T00:00:00Z When blood pressure increases, smooth muscle cells in the wall of the arteriole are stretched and respond by contracting to resist the pressure, resulting in little change in flow. Anatomy and Physiology 2013-06-19T00:00:00Z Raynaud suggested that the local syncope was produced by contraction of the vessels; the asphyxia is probably caused by a dilatation of the capillaries and venules, with persistence of the spasm of the arterioles. Anomalies and Curiosities of Medicine Forci-pressure.—Bleeding from the smallest arteries and from arterioles can usually be arrested by firmly squeezing them for a few minutes with artery forceps. Manual of Surgery Volume First: General Surgery. Sixth Edition. In the arterioles three kinds of changes occur: a muscular hypertrophy; a fibrosis of all the coats; or a marked proliferation of the intimal endothelium. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z They constrict the afferent arterioles, causing the flow of blood into the nephrons to stop. Biology for AP Courses 2022-06-09T00:00:00Z NO has the opposite effect, relaxing the afferent arteriole at the same time ATP and adenosine are stimulating it to contract. Anatomy and Physiology 2013-06-19T00:00:00Z We also have our spring when the little arterioles dilate, the lymph flows in a brisker stream, the glands work harder, winnowing and straining. The Parasite Disease, or symmetrical gangrene, is supposed to be due to spasm of the arterioles, resulting from peripheral neuritis. Manual of Surgery Volume First: General Surgery. Sixth Edition. Such a deposition of layer upon layer of cells in an arteriole and the resulting fibrosis leads to the condition of disappearance of the lumen of the vessel, endarteritis obliterans. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z It constricts the efferent arterioles, causing the flow of blood into the nephrons to stop. Biology for AP Courses 2022-06-09T00:00:00Z Decreased blood pressure is also sensed by the granular cells in the afferent arteriole of the JGA. Anatomy and Physiology 2013-06-19T00:00:00Z A fibrosis of the heart muscle and of the arterioles gradually develops, and the heart muscle sooner or later feels the strain. Disturbances of the Heart There are thousands of miles of minute tubing in the human body—the arterioles, veins, capillaries and lymphatic vessels. The Royal Road to Health The muscular arterioles throughout the body by their tonus serve to keep up the normal blood pressure and to distribute the blood evenly to the various organs. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z They constrict the efferent arterioles, causing the flow of blood into the nephrons to stop. Biology for AP Courses 2022-06-09T00:00:00Z As their own lumen averages just 30 micrometers or less, arterioles are critical in slowing down—or resisting—blood flow. Anatomy and Physiology 2013-06-19T00:00:00Z Digitalis also increases the blood pressure, not only by improving the activity of the heart, but also by causing some contraction of the arterioles. Disturbances of the Heart Under normal conditions the main arterial trunks supply their respective organs, the little connecting arterioles playing an insignificant part. A History of Science — Volume 4 The arterioles are thickened, the sclerosis being either of the intima or media or of both. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z It increases GFR through concurrent vasodilation of the afferent arteriole and vasoconstriction of the efferent arteriole. Anatomy and Physiology 2013-06-19T00:00:00Z Each metarteriole arises from a terminal arteriole and branches to supply blood to a capillary bed that may consist of 10–100 capillaries. Anatomy and Physiology 2013-06-19T00:00:00Z The moment that the heart and its arterioles relax, the attack is often over. Disturbances of the Heart In turn, muscular arteries branch to distribute blood to the vast network of arterioles. Anatomy and Physiology 2013-06-19T00:00:00Z There it acts primarily on the musculature of the arterioles causing tonic contraction and an increase of work on the part of the heart to force the blood through narrowed channels. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z With a lumen averaging 30 micrometers or less in diameter, arterioles are critical in slowing down—or resisting—blood flow and, thus, causing a substantial drop in blood pressure. Anatomy and Physiology 2013-06-19T00:00:00Z Less dramatic than the vasoconstriction seen in smaller arteries and arterioles, venoconstriction may be likened to a “stiffening” of the vessel wall. Anatomy and Physiology 2013-06-19T00:00:00Z If small hemorrhages occur in the arterioles of the extremities, of course the prognosis is not serious. Disturbances of the Heart The importance of the arterioles is that they will be the primary site of both resistance and regulation of blood pressure. Anatomy and Physiology 2013-06-19T00:00:00Z Contraction of a large area of arterioles increases the blood pressure and, strangely enough, the arteries respond to increased arterial pressure, not by dilatation, but by contraction. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z An arteriovenous anastomosis, which directly connects the arteriole with the venule, is shown at the bottom. Anatomy and Physiology 2013-06-19T00:00:00Z Although the effect diminishes over distance from the heart, elements of the systolic and diastolic components of the pulse are still evident down to the level of the arterioles. Anatomy and Physiology 2013-06-19T00:00:00Z Any drug or substance that raises the blood pressure by stimulating the vasomotor center or the arterioles, when constantly repeated, will be a cause of hypertension. Disturbances of the Heart As noted earlier, arterioles are normally partially constricted: With maximal stimulation, their radius may be reduced to one-half of the resting state. Anatomy and Physiology 2013-06-19T00:00:00Z It would appear that rise of blood pressure tends to throw increased work upon the musculature of the arterioles. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z Full dilation of most arterioles requires that this sympathetic stimulation be suppressed. Anatomy and Physiology 2013-06-19T00:00:00Z When blood leaving an arteriole first enters a capillary bed, the CHP is quite high—about 35 mm Hg. Anatomy and Physiology 2013-06-19T00:00:00Z Generally speaking, a low systolic pressure shows a weak acting heart muscle, and a very low diastolic pressure shows a dilated condition of the arterioles. Disturbances of the Heart Sympathetic stimulation of the peripheral arterioles will also decrease, resulting in vasodilation. Anatomy and Physiology 2013-06-19T00:00:00Z For blood tension to be raised all over the body, conditions must favor the generalized contraction of a large area of arterioles. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z Bear in mind, however, that dilation and constriction of the arterioles feeding the capillary beds is the primary control mechanism. Anatomy and Physiology 2013-06-19T00:00:00Z When it is, an arteriole can expand by as much as 150 percent. Anatomy and Physiology 2013-06-19T00:00:00Z The myogenic response is a localized process that serves to stabilize blood flow in the capillary network that follows that arteriole. Anatomy and Physiology 2013-06-19T00:00:00Z Blood pumped by the heart flows through a series of vessels known as arteries, arterioles, capillaries, venules, and veins before returning to the heart. Anatomy and Physiology 2013-06-19T00:00:00Z In the brain the result of gradual thickening of the arterioles is a diminished blood supply, softening of the portion supplied by the artery, and later a connective tissue deposit. Arteriosclerosis and Hypertension: with Chapters on Blood Pressure, 3rd Edition. 2011-10-11T02:01:07.890Z Arteries transport blood away from the heart and branch into smaller vessels, forming arterioles. Anatomy and Physiology 2013-06-19T00:00:00Z The pulmonary arteries in turn branch many times within the lung, forming a series of smaller arteries and arterioles that eventually lead to the pulmonary capillaries. Anatomy and Physiology 2013-06-19T00:00:00Z In terms of scale, the diameter of an arteriole is measured in micrometers compared to millimeters for elastic and muscular arteries. Anatomy and Physiology 2013-06-19T00:00:00Z And if an artery or arteriole dilates to twice its initial radius, then resistance in the vessel will decrease to 1/16 of its original value and flow will increase 16 times. Anatomy and Physiology 2013-06-19T00:00:00Z In fact, arterioles are the site of greatest resistance in the entire vascular network. Anatomy and Physiology 2013-06-19T00:00:00Z However, the site of the most precipitous drop, and the site of greatest resistance, is the arterioles. Anatomy and Physiology 2013-06-19T00:00:00Z The white pulp surrounds a central arteriole and consists of germinal centers of dividing B cells surrounded by T cells and accessory cells, including macrophages and dendritic cells. Anatomy and Physiology 2013-06-19T00:00:00Z This explains why vasodilation and vasoconstriction of arterioles play more significant roles in regulating blood pressure than do the vasodilation and vasoconstriction of other vessels. Anatomy and Physiology 2013-06-19T00:00:00Z Figure 20.20 summarizes the effects of nervous, endocrine, and local controls on arterioles. Anatomy and Physiology 2013-06-19T00:00:00Z Vasoconstriction of the arterioles increases vascular resistance, whereas constriction of the veins increases venous return to the heart. Anatomy and Physiology 2013-06-19T00:00:00Z Arteries, arterioles, venules, and veins are composed of three tunics known as the tunica intima, tunica media, and tunica externa. Anatomy and Physiology 2013-06-19T00:00:00Z This is achieved by constricting the pulmonary arterioles that serves the dysfunctional alveolus, which redirects blood to other alveoli that have sufficient ventilation. Anatomy and Physiology 2013-06-19T00:00:00Z The glomerulus has a relatively high pressure inside its capillaries and can sustain this by dilating the afferent arteriole while constricting the efferent arteriole. Anatomy and Physiology 2013-06-19T00:00:00Z This includes vasoconstriction of the afferent arterioles, further reducing the volume of blood flowing through the kidneys. Anatomy and Physiology 2013-06-19T00:00:00Z This mechanism works in the afferent arteriole that supplies the glomerulus. Anatomy and Physiology 2013-06-19T00:00:00Z Recall that the DCT is in intimate contact with the afferent and efferent arterioles of the glomerulus. Anatomy and Physiology 2013-06-19T00:00:00Z As mentioned above, a greater partial pressure of oxygen in the alveoli causes the pulmonary arterioles to dilate, increasing blood flow. Anatomy and Physiology 2013-06-19T00:00:00Z It is produced in the lungs but binds to the surfaces of endothelial cells in the afferent arterioles and glomerulus. Anatomy and Physiology 2013-06-19T00:00:00Z It acts systemically to cause vasoconstriction as well as constriction of both the afferent and efferent arterioles of the glomerulus. Anatomy and Physiology 2013-06-19T00:00:00Z Figure 20.4 Types of Arteries and Arterioles Comparison of the walls of an elastic artery, a muscular artery, and an arteriole is shown. Anatomy and Physiology 2013-06-19T00:00:00Z This means, for example, that if an artery or arteriole constricts to one-half of its original radius, the resistance to flow will increase 16 times. Anatomy and Physiology 2013-06-19T00:00:00Z It causes the kidneys to retain water, constricts arterioles in the peripheral circulation, and affects some social behaviors in mammals. Anatomy and Physiology 2013-06-19T00:00:00Z Although the diameter of an individual capillary is significantly smaller than the diameter of an arteriole, there are vastly more capillaries in the body than there are other types of blood vessels. Anatomy and Physiology 2013-06-19T00:00:00Z In the arterial system, vasodilation and vasoconstriction of the arterioles is a significant factor in systemic blood pressure: Slight vasodilation greatly decreases resistance and increases flow, whereas slight vasoconstriction greatly increases resistance and decreases flow. Anatomy and Physiology 2013-06-19T00:00:00Z Figure 21.3 Lymphatic Capillaries Lymphatic capillaries are interlaced with the arterioles and venules of the cardiovascular system. Anatomy and Physiology 2013-06-19T00:00:00Z |
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