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Blood Vessels Ch 19

A&P 202 Wk 5

What is the central space where blood flows through the vessel the lumen
What is the innermost layer and has intimate contact with the blood. It contains the endothelium, the simple squamous epithelium that lines the lumen of all vessels The tunica interna, or tunica intima
What layer of the blood vessel is circularly arranged smooth muscle cells and sheets of elastin and is responsible for relaxing or constricting based on the body's needs middle tunic, or tunica media
What is composed largely of loosely woven collagen fibers that protect and reinforce the vessel. It also anchors the vessels to surrounding structures the third layer, or tunica externa
Why would an artery have a thicker tunica media layer? because they are more active in vasoconstriction and less idstensible
Which blood vessels contain more smooth muscle and less elastic than the elastic arteries, owing to their major role in vasoconstriction distributing arteries
What are the smallest blood vessels capillaries
What are low-resistance pathways that conduct blood from the heart to medium sized arteries referred to as? elastic arteries or conducting arteries
What are the 3 types of capillaries called? continuous, fenestrated and sinusoidal
What are the most common type of capillaries? continuous
Where are sinusoid capillaries found? in the liver, bone marrow, lymphoid tissues and some endocrine organs
What removes and destroys any contained bacteria and are found in the lining of the endothelium of the sinusoids in the liver? Kupffer cells
In a capillary bed, what is the vessel structurally intermediate between an arteriole and a capillary? metarteriole
What is a cuff of smooth muscle fibers that surround the root of each true capillary at the metarteriole and acts as a valve to regulate blood flow into the capillary called precapillary sphincter
What regulates the relative amount of blood entering a capillary bed? local chemical conditions and arteriolar vasomotor nerve fibers
When are venules formed and what do they form? When capillaries unite and they form veins
Why are veins called capacitance vessels and blood reservoirs? because of their large blood supply; up to 65% of the body's supply
What low-pressure adaptations ensure venous blood is returned to the heart at the same rate it is pumped into the circulation? large diameter lumens and valves that prevent blood from backflowing
What are venous valves formed from and where are they most abundant and where are they absent? folds of the tunica intima; in the veins of the limbs, where the upward flow of blood is opposed by gravity; they are absent in veins of the ventral body cavity
What is a homeostatic imbalance of veins that causes them to become tortuous and dilated because of leaky valves? Varicose veins
What are several factors that contribute to varicose veins? heredity; prolonged standing in one position, obesity, pregnancy; elevated venous pressure
What are highly specialized, flattened veins with extremely thin walls composed only of endothelium called and where are they found? venous sinuses, ie coronary sinus of the heart and dural sinuses of the brain
What are alternate blood pathways in case one branch is cut or blocked by a clot, provided by anastomoses called? collateral channels
Where do arterial anastomoses occur? around joints, abdominal organs, the brain and the heart
What does arteriovenous anstomoses connect? arterioles and venules
What is friction encountered by blood in the systemic circulation called and what are the 3 important sources? peripheral resistance; blood viscosity, vessel length, and vessel diameter
What is the internal resistance to flow that exists in all fluids and is related to the thickness or "stickiness" of a fluid? blood viscosity
How is blood's peripheral resistance influenced by vessel length? longer veins make for more resistance
How is blood flow related to the peripheral resistance in the systemic circulation? inversely proportional
What is the pressure that propels the blood to the tissues called? mean arterial pressure (MAP) and it is roughly equal to the diastolic pressure plus one-third of the pulse pressure
In what 3 ways do veins adapt to venous return to overcome low pressure? respiratory pump-breathing which squeezes veins & forces blood toward heart;muscular pump-as skeletal muscles surrounding deep veins contract/relax, they 'milk' blood toward heart;layer of smooth muscle around veins that constricts under SNS control
Cardiac output (CO) is equal to Stroke volume times what? heart rate
What is normal CO (cardiac output)? 5.0 to 5.5 L/minute
What is usually in charge of heart rate? cardioinhibitory center in the medulla
What nerves maintain the resting heart rate? parasympathetic vagus nerves
What controls the heart's stroke volume during 'resting' periods? venous return (end diastolic volume)
During stress, which center take over, activating the sympathetic nervous system and increasing both heart rate (by acting on SA node) and stroke volume (by enhancing cardiac muscle contractility)? cardioacceleratory center
What is the neural center - the cluster of neurons in the medulla - that oversees changes in the diameter of blood vessels called? the vasomotor center
How does the cardiovascular center integrate blood pressure control? by altering cardiac output and blood vessel diameter
How is vasomotor tone achieved in the arterioles? by impulses transmitted by the vasomotor center, along sympathetic efferents called vasomotor fibers and innervate the smooth muscle of blood vessels, (mainly arterioles)
What happens in the carotid sinuses when arterial blood pressure rises? neural receptors called baroreceptors are stretched, sending a rapid stream of impulses to vasomotor center which results in vasodilation of arterioles and veins and a decline in blood pressure
What does a decline in mean arterial pressure (MAP) initiate? reflex vasoconstriction and increases cardiac output, causing blood pressure to rise.
What are regulated together so that changes in blood pressure are minimized? peripheral resistance and cardiac output
What is the function of rapidly responding barorecptors? to protect the circulation against short-term changes in blood pressure, such as those which occur when you change your posture
When do chemoreceptors in the aortic arch and large arteries of the neck transmit impulses to the cardioacceleratory center, to increase cardiac output and to the vasomotor center, which causes reflex vasoconstriction? when the oxygen content or pH of the blood drops sharply or the CO2 levels rise
What are the 2 most prominent chemoreceptors located close by the baroreceptors in the carotid sinus and aortic arch? carotid and aortic bodies
Where are reflexes that regulate blood pressure found? integrated in the medulla of the brain stem
Hormones that affect blood pressure are: Adrenal medulla hormones - norepinephrine and epinephrine; atrial natriuretic peptide (ANP); ADH(vasopressin); angiotensin II
What mechanisms are a long term control of blood pressure? renal mechanisms
How does the direct renal mechanism alter blood volume? dependently or independently of hormones independently
How does the indirect renal mechanism (renin-angiotensin mechanism) alter blood volume? kidneys release renin into blood which triggers a series of reactions that produce angiotensin II which increasing peripheral resistance via its potent vasoconstriction properties
How does aldosterone affect blood pressure? enhances renal reabsorption of sodium and prods posterior pitutiary to release ADH, which promotes more water reabsorption, causing both blood volume and blood pressure to rise
What is hypotension? low blood pressure - systolic pressure below 100 mm Hg
What is orthostatic hypotension? temporary low blood pressure and dizziness when suddenly arising
What can chronic hypotension be a sign of? Addison's disease; hypothyroidism, or severe tissue wasting. Can be an important signs of circulatory shock
What is hypertension and who is likely to have it? high BP; obese people due to more total length of their blood vessels
What can happen in cases of prolonged hypertension? heart failure, vascular disease, renal failure, and stroke
What factors can contribute to hypertension? diet; obesity; age (over 40); diabetes mellitus; heredity; stress; smoking
How can primary hypertension be controlled? by restricting salt, fat, and cholesterol intake, losing weight, stopping smoking, managing stress, and antihypertensive drugs (diuretics, beta-blockers, calcium channel blockers, and angiotensin-converting enzyme (ACE) inhibitors.
What is the function of tissue perfusion? delivery of oxygen and nutrients to and removal of wastes from, tissue cells, gas exchange in the lungs; absorption of nutrients from digestive tract; urine formation in the kidneys
What percent of blood flow does the following receive when the body is at rest: brain heart kidneys abdominal organs skeletal muscles brain - 13% heart - 4% kidneys - 20% abdominal organs - 24% skeletal muscles - 20%
What is the primary role of the sympathetic nervous system in ruling blood vessel diameter? vasoconstriction
What is the primary role in causing vasodilation? Nitrous oxide
What potent vasoconstrictor is released by the endothelium? endothelins
What is the dramatically increased blood flow into a tissue that occurs after the blood supply to the area has been temporarily blocked? reactive hyperemia
What are 1)metabolic and 2)myogenic factors that determine the final autoregulatory response of a tissue? chemical and physical
What is the phenomenon called that is particularly common in the heart when a coronary vessel is partially occluded where the number of blood vessels in the region increases and existing vessels enlarge? angiogenesis
When muscles becomes active, blood flow increases in direct proportion to their greater metabolic activity and is known as what? active or exercise hyperemia
What organ in the the body is the most metabolically active but the least able to store essential nutrients? the brain
What is the usual result of pressures over 160 mm Hg, which dramatically increases brain capillary permeability? cerebral edema
What 3 functions does blood flowing thru the skin provide/ 1) supplies nutrients to the cells 2) aids in body temp regulation 3) provides a blood reservoir
What does low pulmonary oxygen levels in the pulmonary circulation system cause? vasoconstriction (narrowing of the blood vessels resulting from contraction of the muscular wall of the vessels)
The blood flow thru capillary networks is slow and intermittent and is known as what? vasomotion
What is the force exerted by a fluid pressing against a wall? hydrostatic pressure
Hydrostatic pressure is the same as? capillary blood pressure
What is the process of forcing fluids thru the capillary walls via capillary hydrostatic pressure? filtration
What is the force opposing a hydrostatic pressure, created by the presence in a fluid of large nondiffusible molecules such as plasma proteins, called? colloid osmotic pressure
What is the condition called in which blood vessels are inadequately filled and blood cannot circulate normally resulting in inadequate blood flow to meet tissue needs? circulatory shock
What is the most common form of circulatory shock, resulting from large scale loss of blood, as in hemorrhage, severe vomiting or diarrhea or extensive burns? hypovolemic shock
What occurs when the heart is so inefficient that it cant sustain adequate circulation, usually caused by myocardial damage, such as heart attack? cardiogenic shock
What is the most common cause of sudden cardiovascular death in men in their early 40s and 50s? hypertension
All systemic arteries branch from where? The aorta
Where does blood pass to after first moving thru pulmonary circuit and systemic veins? systemic arteries
Blood is carried away from the heart by what? arteries
Blood is brought toward the heart by what? veins
What carries blood to tissue cells and are exchange sites? capillaries
All blood vessels except what have three layers: capillaries
Where are elastic (conducting) arteries that expand during systole and act as pressure reservoirs found? close to the heart
What carries blood to specific organs, are less stretchy and more active in vasoconstriction? muscular (distributing) arteries
What regulates blood flow into capillary beds? arterioles
What is a degenerative vascular disease that decreases the elasticity of arteries? arteriosclerosis
What is the formation of fatty subendothelial lesions called? atherosclerosis
What is found on capillaries and aid in the exchange between the blood and interstitial fluid? clefts
What are the most permeable capillaries? sinusoids (wide, tortuous channels)
What are the 2nd most permeable capillaries? fenestrated capillaries
What are the least permeable capillaries and why? continuous capillaries, which lack pores
What do vascular shunts connect? terminal arteriole and venule at opposite ends of a capillary bed
Where do most true capillaries arise from? the shunt channels
What regulates the amount of blood flowing into the true capillaries? precapillary sphincters
How do veins serve as blood reservoirs? They are usually only partially filled
What is the joining together of arteries to provide alternate channels for blood to reach the same organ called? anastomosis
Where do vascular anastomoses form? between veins and between arterioles and venules
Where is systemic blood pressure highest and lowest? highest - aorta lowest - venae cavae
Where is the steepest drop in BP? in the arterioles, where resistance is greatest
What does arterial blood pressure depend on? compliance of the elastic arteries and on how much blood is forced into them
When does arterial blood pressure peak? during systole
What varies directly with CO (cardiac output), peripheral resistance, and blood volume? blood pressure
How does the vasomotor center regulate blood pressure? regulates blood vessel diameter
How do kidneys regulate low bp? releasing renin, which triggers the formation of angiotensin II (a vasconstrictor) and release of aldosterone
What is the major cause of myocardial infarct, stroke, and renal disease? hypertension
What is considered chronic hypertension? 140/90 or higher
Which other 2 organs are most affected vascularly by chronic hypertension? eyes and kidneys
What are risk factors of hypertension? high fat, high salt diet, obesity, diabetes mellitus, advanced age, smoking, stress, being black and having a family history
What is autoregulation usually controlled by? oxygen deficits and accumulation of local metabolites
What is autoregulation in the brain controlled by? primarily by a drop in pH and by myogenic mechanisms
How do water soluble substances move across capillary walls? thru clefts or fenestrations
Where do fat-soluble substances pass thru the capillary wall? through the lipid portion of the endothelial cell membrane
How are larger molecules transported through capillary walls? actively transported via pinocytotic vesicles or caveolae
What collects the small net loss of fluid and protein into the interstitial space and returns it to the cardiovascular system? the lymphatic vessels
What occurs when blood perfusion of body tissues is inadequate? circulatory shock
What do most cases of shock reflect? low blood volume (hypovolemic shock), abnormal vasodilation (vascular shock), pump failure (cardiogenic shock)
Which circulation system transports oxygen-poor, carbon dioxide rich blood to the lungs for oxygenation and carbon dioxide unloading? pulmonary circulation
Which circulation system transports oxygenated blood from the left ventricle to all body tissues via the aorta and its branches? systemic circulation
Which veins tend to have numerous interconnections? superficial veins
What does the dural sinuses and the hepatic portal circulation have in common? They are both venous drainage patterns
Where does the fetal vasculature develop from? embryonic blood islands and mesenchyme
By which week is the fetal vasculature functioning? the 4th week
What happens to the pulmonary and hepatic shunts and special umbilical vessels shortly after birth? they are occluded
Created by: svking01



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