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Blood Vessels
-closed circuit of tubes carrying blood from the heart to body & back -arteries & arterioles: carry blood away from ventricles -capillaries: exchange materials between blood and tissues -venules & veins: returns blood to the atria TERM 2
Summary of Circulation
DEFINITION 2 -heart->arteries->arterioles->capillaries->venules->veins-
heart TERM 3
Histology of an Artery
DEFINITION 3 -strong & elastic -carries blood away from the heart - subdivided into arterioles TERM 4
tunica intima
DEFINITION 4 -innermost -simple squamous epithelium on top of a CT membrane -internal elastic membrane:boundary between tunica intima &media -separates blood flow from vessel wall, prevents blood clotting by secreting various chemicals, helps to regulate blood pressure TERM 5
tunica media
DEFINITION 5 -middle layer -bulk of wall -smooth muscle & elastic CT - external membrane: boundary between tunica media & externa
tunica externa (adventitia)
-outer most layer -thin, made of CT, elastic & collagenous fibers -attaches artery to surrounding tissues -contains vasa vasorum (blood vessels that feed the walls of larger blood vessels) TERM 7
Functions of Tissues
DEFINITION 7 -endothelium: smooth surface for blood to flow -CT: elasticity -smooth muscle: innervated by sympathetic branches of ANS, vasoconstriction (constriction of blood vessels), vasodilation (dilation of blood vessels) TERM 8
Artery vs. Vein
DEFINITION 8 -walls of artery thicker and have much more smooth muscle - arteries appear smaller due to contraction of walls - endothelium of an artery can not contract TERM 9
elastic arteries
DEFINITION 9 -large diameter -in areas of high pressure -tunica media: has a high % of elastic tissue & less smooth muscle -ex.: pulmonary trunk, aorta, carotid, subclavian, common iliac TERM 10
muscular arteries
DEFINITION 10 -have large to small diameters -carry blood to skeletal muscles & organs -tunica media: much smooth muscle; less elastic tissue -ex.: femoral, carotids, brachials, mesenteries
continuous capillaries
-smallest -many tight junctions & desmosomes; pinocytic vesicles -allow movement by: passive diffusion & active transport -located in the CNS, Skeletal muscle, & lungs -may be modified to form low permeability barriers: -blood-brain barrier -blood-thymus TERM 17
fenestrated capillaries
DEFINITION 17 -swiss cheese appearance because of pores (much more permeable) -pinocytic vesicle: allows movement of peptides & proteins -locations: kidneys, intestines, endocrine glands, choroid plexus TERM 18
sinusoidal capillaries
DEFINITION 18
- largest -specialized for max exchange by: large intercellular gaps, fenestrated (pores), discontinuous basement membrane, allows for movement of cells -allows cells to enter/exit; ex. spleen & bone marrow -other locations: liver & adrenal glands TERM 19
Capillary
beds
DEFINITION 19 -interconnected capillaries -# of capillaries in a tissue depends on rate of metabolism, & varies between body parts -form networks -derived from arterioles -have pre-capillary sphincters: manages blood flow -metarterioles: a direct connection through the bed, leads to a thoroughfare channel TERM 20
Anastomoses
DEFINITION 20 -arterial anastomosis: connection made where 2 arteries (collaterals) fuse, allows twice as much blood supplied, found in areas with high O2 demands -arteriovenous anastomosis: direct connection between arterioles & venule, found where blood flow may be hindered by posture
venules
-smallest of veins -collects blood -tunica external & intima can have limited amounts of muscles TERM 22
medium vein
DEFINITION 22 -has all 3 layers, tunica media is very thin, tunica externa is thick -has valves -has low blood pressure TERM 23
large vein
DEFINITION 23 -has all 3 layers, tunica media is very thin, tunica externa is thick -has valves -has low blood pressure -ex: superior & inferior vena cava TERM 24
venous valves
DEFINITION 24
- flap-like structure projecting inward -folds of the tunica interna -found in extremities, arms & legs -prevents the back flow of blood TERM 25
venous blood-flow
DEFINITION 25 -under little pressure, therefore must rely on other factors -skeletal muscle pump: when a muscle contracts it massages veins & forces blood up opening valves, when blood goes through valves close - respiratory movements (Thoracoabdominal pump): during respiration diaphragm lowers this decreasing pressure in the thoracic cavity while pressure in the abdomen is increased
