blood vessels pt.2 Flashcards
pressure in peripheral venules are less than __ percent than ascending aorta (largest artery)
10
Folds of tunica intima projecting from vessel wall pointing in direction of blood flow. Ensures one-way flow of blood toward heart, powered by contraction of skeletal muscles. Not present in arteries
Valves (in venous system)
Valves permit blood flow in one direction and prevent _______ of blood toward capillaries.
backflow
When valves do not work properly, blood can ______ in veins, causing _______.
pool, distention
condition caused by weak or damaged vein walls and valves. causes discomfort and cosmetic problems in thighs and legs
varicose veins
condition which veins or blood vessels in and around your anal canal and lower rectum become swollen and irritated
hemorrhoids
Systemic venous system contains __ percent of total blood volume
64%
Amount of blood circulating in venous system
3.5 liters
Amount of blood carried in venous networks from digestive organs to liver, providing a blood reservoir.
1 liter
Consists of a tube of endothelial cells. Comprised of delicate basement membrane. Lacking both tunica media and tunica externa. About the width of single RBC
capillary
Two major types of capillaries
continuous and fenestrated
capillaries in which the endothelium is a complete lining. Located throughout body in all tissues except epithelia and cartilage
continuous capillaries
Capillaries permitting diffusion of water, small solutes, and lipid-soluble materials. Otherwise selective vesicular transport is used.
continuous capillaries
Continuous capillaries in CNS & thymus contain _____ ______, only allowing selective vesicular transport. Important for blood-brain barrier.
tight junctions
Capillaries containing “windows,” or pores, penetrating endothelial lining. Permits rapid exchange of water and larger solutes.
fenestrated capillaries
Found in Choroid plexus of brain, capillaries of hypothalamus, pituitary, pineal, and thyroid glands
Absorptive areas of intestinal tract
Kidney filtration sites
fenestrated capillaries
Resemble fenestrated capillaries, but more flat and irregular shape. Has gaps located between endothelial cells. Basement membrane is thin or absent.
sinusoidal capillaries
Structure permitting more water and solute exchange in certain capillaries. Found on capillaries in liver, bone marrow, spleen, and many endocrine organs.
sinusoids
Network of numerous interconnected capillaries. Contain several connections between arterioles and venules
capillary bed
capillary beds may be supplied by more than one ____. The fusion of vessels is an example of _____. Helps deliver blood to capillary bed even when one artery is blocked or compressed.
artery, anastomosis
Regulates bypass of capillary beds (arteriovenous anastomosis).
sympathetic innervation
directly connects arteriole to venule
arteriovenous anastomosis
Initial segment or branch of the arteriole connecting it to the capillary bed. Contains smooth muscle that can change flow rate by adjusting vessel’s diameter
metarteriole or precapillary arteriole
Most direct passageway through capillary bed. Continuation of metarteriole enables blood to bypass capillary bed and flow directly into a venule
thoroughfare channel
Bands of smooth muscle which contract and relax. Control flow into the capillary bed.
precapillary sphincter
At any given time, ____ _____ of body’s capillaries are shut down.
three quarters
When sphincters _____, capillary beds fill with blood. When sphincters ______, they stop blood to the capillary bed.
relax, contract
