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chpt 19
blood vessels
| Question | Answer |
|---|---|
| What carries oxygenated blood away from the heart; except for pulmonary circulation and umbilical vessels of a fetus? | Arteries |
| What contact tissue cells and directly serve cellular needs | Capillaries |
| What carry deoxygenated blood toward the heart ? | Veins |
| In Tunica intima, Endothelium lines the lumen of all | vessels |
| In Tunica media,Smooth muscle and sheets of elastin. Sympathetic vasomotor nerve fibers control | vasoconstriction and vasodilation of vessels |
| In Tunica externa ,Collagen fibers protect and reinforce Larger vessels contain | vasa vasorum to nourish the external layer |
| These are large thick-walled arteries with elastin in all three tunics Eg: Aorta and its major branches Large lumen offers low-resistance Act as pressure reservoirs—expand and recoil as blood is ejected from the heart | Elastic (Conducting) Arteries |
| Distal to elastic arteries; deliver blood to body organs Have thick tunica media with more smooth muscle Active in vasoconstriction | Muscular (Distributing) Arteries and Arterioles |
| Smallest arteries Lead to capillary beds Control flow into capillary beds via vasodilation and vasoconstriction | Arterioles |
| Microscopic blood vessels Walls of thin tunica intima, one cell thick Pericytes help stabilize their walls and control permeability | Capillaries |
| Abundant in the skin and muscles Tight junctions connect endothelial cells Intercellular clefts allow the passage of fluids and small solutes | Continuous Capillaries |
| The least permeable capilllary ? | Continuous capillaries of the brain |
| More permeable than continuous capillaries Function in absorption or filtrate formation (small intestines, endocrine glands, and kidneys) | Fenestrated Capillaries |
| Fewer tight junctions, larger intercellular clefts, large lumens Usually fenestrated Allow large molecules and blood cells to pass between the blood and surrounding tissues Found in the liver, bone marrow, spleen | Sinusoidal Capillaries |
| Interwoven networks of capillaries form the microcirculation between arterioles and | venules |
| What directly connects the terminal arteriole and a postcapillary venule | Vascular shunt |
| 10 to 100 exchange vessels per capillary bed Branch off the metarteriole or terminal arteriole | True capillaries |
| Regulated by local chemical conditions and | vasomotor nerves |
| Precapillary sphincters regulate blood flow into | true capillaries |
| Formed when capillary beds unite Very porous; allow fluids and WBCs into tissues | Venules |
| Formed when venules converge Have thinner walls, larger lumens compared with corresponding arteries | veins |
| veins Blood pressure is lower than in | arteries |
| veins have a _____________ ___________ which consist of collagen fibers and elastic networks | Thin tunica media and a thick tunica externa |
| veins contain | 65% of blood supply |
| Adaptations that ensure return of blood to the heart Large-diameter lumens offer little resistance Valves prevent backflow of blood Most abundant in veins of the limbs | veins |
| Venous sinuses | flattened veins with extremely thin walls |
| Force per unit area exerted on the wall of a blood vessel by the blood | Blood pressure (BP) |
| Resistance (peripheral resistance) | Opposition to flow Measure of the amount of friction blood encounters |
| Three important sources of resistance | Blood viscosity Total blood vessel length. Blood vessel diameter |
| The “thickness” of the blood due to formed elements and plasma proteins | Blood viscosity |
| The longer the vessel, the greater the resistance encountered | Blood vessel length |
| Small-diameter arterioles are the major determinants of | peripheral resistance |
| Abrupt changes in diameter or fatty plaques from atherosclerosis dramatically increase resistance Disrupt laminar flow and cause turbulence Resulting in a | bruit |
| Blood flow (F) is directly proportional to the blood (hydrostatic) pressure gradient (P) If P increases, | blood flow speeds up |
| Blood flow is inversely proportional to peripheral resistance (R) If R increases, blood flow | decreases |
| Is highest in the aorta Declines throughout the pathway Is 0 mm Hg in the right atrium | Systemic pressure |
| pressure exerted during ventricular contraction | Systolic pressure |
| lowest level of arterial pressure | Diastolic pressure |
| difference between systolic and diastolic pressure | Pulse pressure |
| pressure changes created during breathing move blood toward the heart by squeezing abdominal veins as thoracic veins expand | Respiratory “pump”: |
| contraction of skeletal muscles “milk” blood toward the heart and valves prevent backflow | Muscular “pump” |
| The main factors influencing blood pressure: | Cardiac output (CO) Peripheral resistance (PR) Blood volume |
| cardiac output isDetermined by venous return and | neural and hormonal controls |
| Resting heart rate is maintained by the cardioinhibitory center via the | parasympathetic vagus nerves |
| neural and hormonal controls Counteract fluctuations in blood pressure by altering peripheral resistance | short term blood pressure |
| renal regulation Counteracts fluctuations in blood pressure by altering blood volume | Long-term blood pressure |
| A cluster of sympathetic neurons in the medulla that oversee changes in blood vessel diameter Maintains vasomotor tone (moderate constriction of arterioles) Receives inputs from baroreceptors, chemoreceptors, and higher brain centers | Vasomotor center |
| Baroreceptors taking part in the carotid sinus reflex | protect the blood supply to the brain |
| Baroreceptors taking part in the aortic reflex help maintain | adequate blood pressure in the systemic circuit |
| Chemoreceptors respond to rise in CO2, drop in | pH or O2 |
| Adrenal medulla hormones norepinephrine (NE) and epinephrine cause generalized | vasoconstriction and increase cardiac output |
| generated by kidney release of renin, causes vasoconstriction | Angiotensin II |
| what causes blood volume and blood pressure to decline, causes generalized vasodilation. Lower BP | ANP + BNP |
| A in arterial bp | release of renin |
| Renin produces the production of | angiotensin II |
| Angiotensin II is a potent | vasoconstrictor |
Created by:
jennysevere24
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