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Chapter 21/blood ves
Blood Vessels and Circulation
| Question | Answer |
|---|---|
| Arteries carry blood away from heart – | all but one carries oxygenated blood (pulmonary artery carries deoxygenated blood to lungs) |
| Veins carry blood toward the heart – | all but the pulmonary veins carry deoxygenated blood (pulmonary veins carry oxygenated blood from lungs to heart to be pumped throughout the body) |
| Elastic arteries | Largest; include the aorta Stretch without injury to accommodate surge of blood forced through them when heart contracts Also when they recoil when ventricles relax |
| Muscular arteries | AKA distributing arteries Carry blood farther away from heart to specific organs and areas of the body Muscular layer in wall of these arteries are proportionately thicker Have a thicker vessel wall than similar-sized veins |
| Arterioles | AKA resistance vessels Smallest arteries Important in regulating blood flow throughout the body Function this way by variable contraction of smooth muscle in their walls |
| Define microcirculation | Blood flow through arterioles, venules, and capillaries Transfer of nutrients and other vital substances between blood and tissue occur at or near capillaries |
| Capillaries = | primary exchange vessels |
| Where exchange of respiratory gases and nutrients occur | |
| Know and describe 3 different types of capillaries | |
| Continuous capillaries | Continuous lining of endothelial cells Have only small openings called intercellular clefts between them |
| Fenestrated capillaries | Have intercellular clefts between endothelial cells Also have small “holes” or fenestrations through plasma membrane of endothelial cells Allows for special function to be discussed later |
| Sinusoid | Have much larger lumen More winding course than other capillaries Basement membrane is either absent or incomplete Fenestrations present in between AND within endothelial cells and are much larger than in other capillary types |
| Know and describe different types of veins | |
| Venules | Have very narrow lumens and porous, thin walls fluid can be exchanged between blood in the smallest venules and tissue spaces Walls consist of little more than endothelial cells, few smooth muscle cells, and occasional fibroblast |
| Medium-sized veins | |
| Large veins | |
| Define venous sinus | Large venous structures that have thin endothelial walls No smooth muscle cells or other support structure Cannot change their shape Depend on surrounding structures for support |
| Know and describe the 3 structural layers of blood vessels | Tunica externa Tunica media Tunica intima |
| Tunica externa | Outermost later “outside coat” Made of strong, flexible fibrous connective tissue Prevents tearing of vessel walls during body movements |
| Tunica media | “middle coat” Made of layer of smooth muscle tissue sandwiched together with a layer of elastic connective tissue Smooth muscle portion allow changes in vessel diameter |
| Tunica intima | inside coat” Made of endothelium Has basement membrane to support it Elastic arteries also have internal elastic membrane |
| Know and describe the 4 types of tissue “fabrics” that make up most vessel walls | Lining endothelial cells Collagen fibers Elastic fibers Smooth muscle cells |
| Endothelial cell lining | Provide smooth luminal surface Influence blood flow and inhibit intravascular coagulation Have intercellular clefts and fenestrations Influence diffusion and movement of substances in and out of blood |
| Collagen fibers | Woven together to reinforce wall Form fibrous protein molecules that aggregate together Very flexible but not near as extensible as elastic fibers Function to keep lumen open and strengthen wall |
| Elastic fibers | Composed of protein polymer, elastin Form a rubberlike network that is highly elastic In large elastic arteries, fibers are arranged in concentric patterns Allow for recoil after distention |
| Smooth muscle cells | Smooth muscle cells found in wall of all segments of vascular system Exception being capillaries Most numerous in elastic and muscular arteries Exert active tension in these vessels when contracting |
| Know how blood flows through the systemic circulation (from heart and finally back to the heart) | L ventricle ascending aorta arteries to various tissues of body arterioles capillaries (exchange of nutrients and respiratory gases occurs here) venules veins inferior and superior vena cava R atrium |
| Know how the blood flows from the heart through the pulmonary circulation | R atrium R ventricle pulmonary artery lung arterioles lung capillaries (exchange of gases between blood and air takes place) lung venules 4 pulmonary veins L atrium L ventricle |
| Define portal system | Blood passes through 2 consecutive capillary beds rather than one |
| Know 2 types of vascular anastomosis | Arterial anastomoses Venous anastomoses |
| Define peripheral resistance | resistance to blood flow imposed by the force of friction between blood and the walls of its vessels |
| List 2 factors contribute to blood viscosity | Increase in either increases blood viscosity Under normal conditions, blood viscosity changes very little Under abnormal conditions (anemia), blood viscosity may lead to such a decrease in peripheral resistance, circulatory failure may result |
| Define vasoconstriction | increased contraction of muscular coat Increases resistance to blood flow Blood flow to tissue decreases |
| Define vasodilation | increase in vessel diameter caused by relaxation of vascular muscles Decreases resistance to blood flow Blood flow to tissue increases |
| Know how vasomotor pressoreflexes respond to an increase or decrease in arterial pressure | Sudden increases in arterial BP stimulates aortic and carotid baroreceptors Stimulates cardiac control center to reduce HR Inhibits vaso-constrictor center Occurs due to more impulses going out over parasympathetic fibers to heart and blood vessels S |
| Know function of chemoreceptor reflex | functions as emergency mechanism when hypoxia or hypercapnia endangers stability of internal environment |
| Nitric Oxide = | vasodilator |
| Endothelin = | vasoconstrictor |
| Define reactive hyperemia | Locally produced substances activate the local vasodilator mechanism Nitric oxide (NO) Others constrict arterioles Endothelin Local vasodilation is also referred to as |
| Define venous return | amount of blood returned to heart by way of veins |
| Define stress-relaxation effect | Overall BP rises Elastic nature of blood vessels allows them to expand to adapt to higher pressure This maintains normal blood flow This effect occurs in all blood vessels to some degree Within certain limitations to its adaptability |
| Define orthostatic effect | shift of blood to reservoir to veins in legs when standing |
| Know how venous pumps overcome influence of gravity on blood flow in veins | Can help overcome the influence of gravity Maintain pressure gradients necessary to keep blood moving into the central veins And onto the atria of the heart |
| Define capillary exchange | Exchange of materials between plasma in the capillaries and the surrounding interstitial fluid of the systemic tissues |
| Define Starling’s law of the capillaries | Several factors govern movement of fluid back and forth across capillary walls Factors include inwardly and outwardly directed forces Balance between these forces determine whether fluids will move in or out of plasma at any point |
| List 3 mechanisms discussed that affect blood volume and HOW they affect blood volume | |
| ADH | (antidiuretic hormone) mechanism: ADH hormone is released by neurohypophysis Acts on kidneys in a way that reduces amount of water lost by the body ADH increases amount of water that the kidneys resorb from urine before urine is excreted The more ADH |
| RAAS | Renin-angiotensin-aldosterone system (RAAS): Renin is released when BP in kidney is low Triggers a series of events that leads to secretion of aldosterone Aldosterone promotes sodium retention by kidney This, in turn, stimulate osmotic flow of water f |
| ANH | Atrial natriuretic hormone (ANH) mechanism: ANH is secreted by specialized cells in atrial wall in response to overstretching Overstretching occurs when venous return is abnormally high ANH adjusts venous return back down by promoting loss of water fro |
| Define sphygmomanometer | Measures the amount of air pressure equal to the BP in an artery Measurement made in terms of how many mm high the air pressure raises a column of Hg in a glass tube Originally consisted of rubber cuff attached by a rubber tube to a compressible bulb an |
| Know how blood pressure is measured | Air is pumped into cuff by compressing on the bulb This puts pressure on the outside of the artery Air is added until pressure exceeds pressure within the artery The air in the cuff is slowly released and air pressure decreases until it approximately e |
| Systolic blood pressure | 1st tapping sound appears when column of Hg indicates the systolic BP Force with which the blood is pushing against the artery walls when the ventricles are contracting Gives valuable information about the force of the L ventricular contraction |
| Diastolic blood pressure | Lowest point at which the sounds can be heard, just before they disappear is ~ the diastolic BP Force of the blood when the ventricles are relaxed Gives valuable information about the resistance of the blood vessels |
| Know what “normal” healthy blood pressure is | Normal BP in adults is 120/80 Upper number = systolic BP Lower number = diastolic BP |
| Define pulse pressure | Difference between systolic and diastolic pressure is called |
| Describe why blood escapes from arteries in spurts but flows steadily and slowly from veins | Blood exerts a comparatively high pressure in arteries and a very low pressure in veins When arteries are cut, blood gushes out with considerable force When veins are cut, blood seeps in a slow, steady stream When ventricles contract, pressure in arter |
| Define minute volume | Volume of blood circulating through body per minute Determined by magnitude of BP gradient and peripheral resistance |
| Most rapid blood flow occurs in the arteries; slowest blood flow occurs in the capillaries | |
| Define pulse | Alternate expansion and recoil of an artery |
| List 2 factors that are responsible for the existence of a pulse | Intermittent injections of blood from heart to aorta which alternately increases and decreases pressure in that vessel If blood poured steadily from heart, pressure would remain fairly constant and there would be no pulse Elasticity of arterial walls wh |
| Know where a pulse wave begins | Pulse wave can be felt at the common carotid artery in the neck Is a large and powerful and rapidly follows the first heart sound |
| Know why pulse wave felt at the carotid arteries occurs at same time as ventricular contraction whereas pulse wave felt at radial artery in wrist does not | |
| Know where the pulse can be felt | Radial artery Temporal artery Common carotid artery Facial artery Brachial artery Popliteal artery Posterior tibial artery Dorsalis pedis artery |
| Know 6 pressure points that can be used to stop arterial bleeding | Temporal artery Facial artery Common carotid artery Subclavian artery Brachial artery Femoral artery |
| Know where venous pulse can be felt | Detectable pulse exists in large veins only Most prominent in the veins close to the heart Because of changes in venous BP brought about by alternate contraction and relaxation of the atria of the heart Clinical significance of venous pulse is not as g |
| Know 6 structures that are necessary for fetal circulation | |
| Umbilical arteries | Additional blood vessels in fetus that carries fetal blood close to maternal blood Umbilical arteries, umbilical veins, and ductus venosus |
| Placenta | Where interchange of gases, foods, and wastes between fetal blood and maternal blood can occur This exchange occurs without actually mixing the fetal and maternal blood Each have their own capillaries |
| Umbilical veins | |
| Ductus venosus | Detour by which most of blood returning from placenta bypasses fetal liver |
| Foramen ovale | Foramen ovale and ductus arteriosus provide detours by which blood bypasses the lungs Foramen ovale is a small hole in septum between the R and L atria |
| Ductus arteriosus | Ductus arteriosus is a small vessel connecting pulmonary artery with the descending aorta Almost all fetal blood is a mixture of oxygenated and deoxygenated blood |
| Define arteriosclerosis | Hardening of arteries Thickening of walls eventually progressing to hardening |
| Define aneurysm and cerebrovascular accident | Section of artery has been widened due to weakening of arterial wall Dangerous because of their tendency to burst Brain aneurysm can lead to a stroke Cerebrovascular accident (CVA) Ischemia of brain tissue results Often fatal |
| Define circulatory shock | Failure of the circulatory system to deliver enough oxygen to tissues Results in impaired cell function Can lead to death if untreated Has many causes All result in decreased blood flow through vessels of the body |
| Define anaphylactic shock | Results from acute allergic reaction called anaphylaxis Blood vessels dilate significantly which greatly reduces blood pressure Blood flow decreases as a result |
| Define septic shock | Results from complications of septicemia Toxins dilate blood vessels initiating shock |
Created by:
coffeecake49
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