chapter 20 - blood cells + circulation Flashcards
Blood vessel wall layers
Tunica intima - innermost; endothelial lining and underlying connective tissue with elastic membrane (AKA internal elastic membrane in arteries)
Tunica media - middle; concentric sheets of smooth muscle in loose connective tissue with external elastic membrane (arteries only); contains smooth muscle responsible for dilation/constriction
Tunica externa - outermost; connective tissue sheath; anchors vessel to adjacent tissues; contains collagen and elastic fibers +smooth muscle (in veins)
veins (functions + morphology)
Veins - return blood to heart
HIGH compliance and LOW elastance compared to arteries
Larger in diameter than arteries, have thinner walls with less elastin and much lower blood pressure
arteries (function + morphology)
Arteries - carry blood away from heart
Elasticity - allows arteries to absorb+store pressure waves from heartbeat
Contractility - change vessel diameter via sympathetic division of ANS
Vasoconstriction - contraction of arterial smooth muscle; shrink lumen
Vasodilatation - relaxation of arterial smooth muscle; enlarging the lumen
elastic arteries/conducting arteries
1-2.5 cm
Large vessels (pulmonary trunk and aorta)
Tunica media has MANY elastic fibers and few muscle cells; even out pulse
muscular arteries/distribution arteries
0.3-1 cm Medium sized (most arteries); tunica media has many muscle cells
arterioles
no longer a pulse, rather even flow
10 microm-0.3mm
venules
(internal diameter 8-100 microm)
Very small veins
Carry blood from capillaries
Small ones (<50 microm) LACK tunica media
medium-sized veins
(2-9 mm)
Thin tunica media and few smooth muscle cells
Tunica externa with longitudinal bundles of elastic fibers
large veins
> 9 mm
thick tunica externa
thin tunica media
GENERAL structure/function of capillaries
function: location of all exchange functions fo cardiovascular system
strucutre: endothelial tube inside thin basal lamina. ONLY TUNICA INTIMA. 8-10 micrometer diameter
CONTINUOUS capillaries structure/function
structure: complete endothelial lining
most common and LEAST permeable
tight junctions and desmosomes join epithelial cells
gaps of unjoined membranes (intercellular clefts) allow small molecules in/out of capillaries
function: permit diffusion of water, small solutes, and lipid-soluble materials while blocking plasma, proteins, and blood cellls
FENESTRATED capillaries
structure: have pores in endothelial lining
function: permit rapid exchange of water and larger solutes between plasma and interstitial fluid w/in choroid plexuses, endocrine organs, kidneys, and intestinal tract
SINUSOID capillaries
structure: gaps BETWEEN adjacent endothelial cells
function: permit free exchange of water, LARGE plasma proteins, and blood cells w/in liver, spleen, bone marrow, and endocrine organs
where is most blood found at rest; how does its distribution change during hemorrhaging or vigorous exercise?
at rest, most blood is found at blood reservoir : systemic veins contain ~65% of total blood volume
the blood reservoir can constrict during hemorrhage to keep volume in capillaries and arteries near normal
blood pressure in pulmonary circulation, arterial side of systemic circulatory system, at the arteriole side of capillary, venule of capillary, and in veins
PC: ~15/8 mmHg arterial side: ~120-80 mmHg arteriole side: 53 mmHg venule: 15-18 mmHg veins: ~15-18 mmHg
