Blood Vessels Review

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School

University of Richmond *

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311

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Anatomy

Date

Oct 30, 2023

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docx

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Uploaded by BrigadierTrout30

1. The general anatomy of each vessel type and the differences between them. a. Arteries (red): carry blood away from the heart; 3 types: elastic (extending from heart cell), muscular (branching from elastic arteries), and arterioles (branching from muscular arteries, feeding into capillaries) i. Composed of 3 tunics 1. Tunica interna (intima): innermost layer surrounding lumen (central blood-containing space surrounded by tunics) 2. Tunica media: middle layer, composed of smooth muscle elastic connective tissue so it can undergo vasal constriction, regulated by sympathetic nervous system, controls vasoconstriction/vasodilation of vessels 3. Tunica externa: outermost layer, protects and reinforces the blood vessels a. Has own blood network (vasa vasorum) bc it’s too far from lumen b. Capillaries : where the exchange between blood and cells and tissues of the body occur; contact tissue cells and directly serve cellular needs i. Smallest blood vessels; thin tunica interna ii. 3 types 1. Continuous: abundant in skin and muscles; have tight junctions bt cells so substances don’t leak out or lose molecules 2. Fenestrated : found where active capillary absorption or filtrate formation occurs (small intestines, endocrine grands, kidneys); looser gap junctions that allow more fluid to leak through; more permeability to solutes and fluid than other capillaries; forms interstitial fluid (fluid bt blood vessels and cells) 3. Sinusoids : loosest of capillaries; irregular shaped lumen and more space bt cells that form wall; space allows for slowing of blood flow as it comes through sinusoids allowing phagocytes to patrol and investigate and look for pathogens; present in liver

where we filter out nutrients, also spleen, bone marrow, and adrenal medulla iii. Capillary beds: where exchange takes place; microcirculation of interwoven networks of capillaries with 1. Vascular shunts: metarteriole – channel connecting an arteriole directly w a post capillary venule 2. True capillaries: branch off the metarteriole and return to channel at distal end of bed c. Veins (blue) : carry blood to the heart; formed when venules converge; capacitance vessels (blood reservoirs) that contain 65% of blood supply i. Composed of 3 tunics 1. Tunica interna (intima): innermost layer surrounding lumen (central blood-containing space surrounded by tunics) 2. Tunica media: middle layer, composed of smooth muscle elastic connective tissue so it can undergo vasal constriction, regulated by sympathetic nervous system, controls vasoconstriction/vasodilation of vessels 3. Tunica externa: outermost layer, protects and reinforces the blood vessels a. Has own blood network (vasa vasorum) bc it’s too far from lumen ii. Much lower bp and thinner walls than arteries iii. Large diameter lumens offering little resistance to flow and valves that prevent backflow of blood (special adaptations to return blood to heart) 2. The relationship between blood flow, blood pressure and resistance. a. Blood flow: actual volume of blood flowing through a vessel, organ, or entire circulation in given period (mL per min) b. Blood pressure: force per unit area exerted on wall of blood vessel by its contained blood (mm Hg) c. Resistance: any opposition to blood flow, increases pressure d. Blood flow is directly proportional to blood pressure gradient

i. If pressure increases, blood flow speeds up e. Blood flow is inversely proportional to peripheral resistance i. If resistance increases, blood flow decreases ii. Blood flow = pressure/resistance f. Resistance is important in influencing blood flow bc its easily changed by altering blood vessel diameter 3. Be able to explain the factors (3) which influence resistance. a. Blood viscosity: thickness of blood; determined by # of cells and amount of protein i. Thicker the blood, greater the resistance in those vessels b. Total blood vessel length: longer the vessel, the greater the resistance encountered bc its spending more time hitting against the walls of these vessels bc they’re longer c. Blood vessel diameter: great influence over resistance; changes in diameter are frequent and significantly alter peripheral resistance i. Increased diameter = decreased resistance = decreased blood pressure 1. Vasoconstriction/vasodilation due to autonomic nervous system stimulation of vessels increases and decreases diameter which increases and decreases resistance a. Vasoconstriction: decreases diameter, increases resistance b. Vasodilation: increases diameter, decreases resistance ii. Small diameter arterioles are major determines of resistance bc they have greatest vasoconstriction control from ans iii. Clots, fatty plaque buildup, decreased elasticity, and stress influence diameter 4. Be able to explain the factors which influence blood pressure. a. Cardiac output (CO): blood flow of entire circulation; determined by venous return and neural and hormonal controls; under stress, cardioacceleratory center increases heart rate and stroke volume

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