Blood Vessels & Blood Pressure

5 types of blood vessels

arteries, arterioles, capillaries, venules, veins

direction of blood flow through blood vessels

arteries→arterioles→capillaries→venules→veins

3 parts of basic blood vessel structure

tunica interna, tunia media, tunica extrena

tunica interna

endothelium on basement membrane (endothelial cells)

tunica media

smooth muscle

tunica extrena

connective tissue (elastic and collegen fibers); strongest part, protects vessels from breaking

arteries

thick-walled blood vessel that transports blood away from the heart to the rest of the body

arteries have a thick

tunica media, made up of smooth muscle, elastic fibers, and elasticity that is important for BP

arteries have to be strong vessels to withstand

high pressures

arterioles

abundant microscopic blood vessels that branch out from larger arteries and connect them to tiny capillaries

arterioles have a thick layer of

smooth muscle (tunica media) which is controlled by the sympathetic NS

arteriole vessel diameter can undergo

vasoconstriction and vasodilation

arteriole vasoconstriction

smaller the lumen = greater resistance to flow

increased resistance = increased BP

arterioles are

resistance vessels

factors that affect blood vessel diameter

sympathetic NS, endocrine system, medical drugs, pathology (smoking, atherosclerosis)

sympathetic NS affects blood vessel diameter by

controlling fight/flight response; releases norepinephrine; smooth muscles contract; vasoconstriction

endocrine system affects blood vessel diameter by

hormones traveling through blood

epinephrine released by adrenal medulla during fight/flight; can cause vasoconstriction/vasodilation; norepinephrine released causes vasoconstriction

another endocrine system factor that affects blood vessel diameter

RAAS

medicinal drugs affect on blood vessel diameter

vasodilators, vasoconstrictors

pathology affect on blood vessel diameter

smoking causes vasoconstriction and vessel damage

atherosclerosis narrows lumen due to plaque buildup

capillaries

the smallest type of blood vessel that connects small arteries (arterioles) to small veins (venules), site of exchange

capillary structure

one layer of endothelial cells and basement membrane

blood flow is slowest in

capillaries

blood velocity is inversely related to

cross sectional area

capillaries are

exchange vessels

capillaries the the most __ blood vessel in our body, meaning they have

abundant, largest cross-sectional area

capillaries slower blood velocity allow time for

material exchange

capillary exchange

movement of substances between blood and IF, done by exchange vessels

3 methods of capillary exchange

diffusion, transcytosis, bulk flow

diffusion

easiest and most-used method for material exchange

substances move down concentration gradient (no energy needed)

in diffusion, gaps between adjacent endothelial cells form

pores within the capillary wall

types of substances that pass through the pores

small, hydrophilic

type of substances that pass through the membrane

hydrophobic

transcytosis

use of pinocytotic vesicles (vesiscular transport) for endo and exocytosis, transfer larger molecules through membrane

bulk flow

capillary exchange method used when needing to move large molecules or a large amount of substances; passive process where large numbers of ions, molecules, or particles (big) in a fluid move together in the same direction

bulk flow is important for

blood volume and blood pressure; helps regulate blood volume and blood pressure by controlling the movement of fluid into and out of capillaries

what determines the direction of bulk flow

pressure gradients, fluid moves according to differences in pressure

2 pressures that control capillary bulk flow

hydrostatic pressure, osmotic pressure

bulk flow filtration

blood hydrostatic pressure pushes fluid OUT of capillaries into surrounding tissues

bulk flow reabsorption

blood colloid osmotic pressure moves fluids from surrounding tissues INTO capillaries

blood hydrostatic pressure is generated by

pumping action of the heart done by arteries (aorta)

blood colloid osmotic pressure is exerted by

colloids that draw up water

colloids

microscopic particles in blood, mostly proteins and blood cells

Starling’s Law of Capillaries explains

how opposing hydrostatic and osmotic pressures determine net fluid movement

Arterial end of the capillary in Starlings Law

high outward hydrostatic pressure promotes net filtration because it exceeds opposing osmotic pressure

hydrostatic pressure along a capillary

decreases as it moves from the arterial to the venous end

Venous end of the capillary in Starlings Law

inward osmotic pressure exceeds outward hydrostatic pressure, reabsorption is favored

amount of filtered fluid absorbed in starlings law

90%, other 10% is collected by the lymphatic system and returned to blood circulation

edema

an abnormal increase in interstitial fluid, can cause an increase in BP and a decrease in plasma proteins (bc blood carries lower amount of thrombocytes)

veins