Anatomy & Physiology: Chapter 21

arteries

carry blood away from heart

arterioles

are smallest branches of arteries

capillaries

are smallest blood vessels, location of exchange between blood and interstitial fluid

venules

veins, collect blood from capillaries

veins

return blood to heart

pulmonary trunk

carries blood from right ventricle to pulmonary circulation

aorta

carries blood from left ventricle to systemic circulation

capillaries

allow one RBC to pass through at a time, have a small diameter and thin walls, chemicals and gases diffuse across walls

three layers of vessels

1 - tunica intima (deep)

2 - tunica media

3 - tunica externa (superficial)

tunica intima

inner layer, includes endotheial lining, connective tissue layer and internal elastic membrane

internal elastic membrane

in arteries, a layer of elastic fibers in outer margin of tunica intima

tunica media

middle layer, contains concentric sheets of smooth muscle in loose connective tissue, binds to inner and outer layers, contains external elastic membrane

external elastic membrane

in the tunica media, separates tunica media from tunica externa

tunica externa

outer layer, anchors vessel to adjacent tissues in arteries, contains collagen fibers, elastic fibers; in veins, contains elastic fibers and smooth muscle cells

differences between arteries and veins

1 - arteries and veins run side by side

2 - arteries have thicker walls and higher blood pressure

3 - collapsed artery has small, round lumen

4 - vein has large, flat lumen due to lower pressure system

5 - vein lining contracts, artery lining does not

6 - artery lining folds

7 - arteries more elastic

8 - veins have valves

elasticity

___ allows arteries to absorb pressure waves that come with each heartbeat

contractility

arteries change diameter, controlled by sympathetic division of ANS

vasoconstriction

the contraction of arterial smooth muscle, enlarging the lumen

affect of vasoconstriction and vasodilation

1 - afterload on heart

2 - peripheral blood pressure

3 - capillary blood flow

elastic arteries

the largest arteries

muscular arteries

medium sized arteries

arterioles

the smallest arteries

elastic arteries

aka conducting arteries, large vessels, tunica media has many elastic fibers and few muscle cells, elasticity evens out pulse force to give peripheral arteries an even flow of blood

muscular arteries

aka distribution arteries, medium sized, tunica media has many muscle cells, found in neck, shoulders, arms and legs

arterioles

small arteries, have little or no tunica externa, thin or incomplete tunica media

resistance

opposition to blood flow

aneurysm

a bulge in an arterial wall, caused by weak spot in elastic fibers, pressure may rupture vessel; high blood pressure

high pressure

arteries are a ____ system

low pressure

veins are a ____ system

capillaries

smallest vessels with thin walls, microscopic networks permeate all active tissues, especially highly metabolic tissues

capillary function

location of all exchange functions of cardiovascular system, materials diffuse between blood and interstitial fluid

capillary structure

endotheial tube, inside thin basement membrane, no tunica media or externa, diameter is similar to a red blood cell

capillary types

continuous, fenestrated, sinusoids

continuous capillaries

complete endothelial lining, found in all tissues except epithelia and cartilage, functions: permit diffusion of water, small solutes and lipid soluble materials, block blood cells and plasma proteins

specials continuous capillaries

in CNS and thymus, very restricted permeability, ex: blood brain barrier

fenestrated capillaries

pres in endothelial lining, permit rapid exchange of water and larger solutes between plasma and interstitial fluid, found in: choroid plexus, endocrine organs, kidneys, intestinal tract

sinusoids

gaps between adjacent endothelial cells, (liver, spleen, bone marrow, endocrine organs), permit free exchange of water and large plasma proteins between blood and interstitial fluid; phagocytic cells monitor blood at sinusoids

capillary beds

aka capillary plexus, connect one atreriole and one venule

precapillary sphincter

guards entrance to each capillary, opens and closes causing capillary blood to flow in pulses

veins

collect blood from capillaries in tissues and organs, return blood to heart, larger in diameter than arteries, thinner walls than arteries, lower blood pressure

venules

very small veins, collect blood from capilaries

medium-sized veins

thin tunica media and few smooth muscle cells, tunica externa with longitudinal bundles of elastic fibers

large veins

have all three layers, thick tunica externa, thin tunica media

venous valves

folds of tunica interna, prevent blood from flowing backward, compressed pushes blood towards heart

2/3

___ of blood is in the venous system at any moment, 1/3 of venous blood is in the large venous networks of the liver, bone marrow and skin

capacitance

ability of a blood vessel to stretch, relationship between blood volume and blood pressure, veins stretch more than arteries

venous response to blood loss

1 - systemic veins constrict (vasoconstriction)

2 - veins in liver, skin and lungs redistribute venous reserve

cardiac output

total capillary blood flow equals ____, and is determined by pressure and resistance

pressure

the heart generates this to overcome resistance, the gradient is more important

pressure gradient

circulatory pressure, the difference between pressure at the heart and pressure at peripheral capillary beds

flow

proportional to the pressure difference, divided by resistance

blood pressure

arterial pressure in mm Hg

capillary hydrostatic pressure

pressure within the capillary beds

venous pressure

pressure in the venous system

circulatory pressure

pressure gradient across the systemic circuit (about 100 mm Hg)

total peripheral resistance

the resistance of the entire cardiovascular system, must be overcome by circulatory pressure

total peripheral resistance factors

vascular resistance, blood viscosity, turbulence

vascular resistance

due to friction between blood and vessel walls, depends on vessel length and vessel diameter, resistance increases as vessel diameter decreases

viscosity

resistance caused by molecules and suspended materials in liquid, about 4x that of water

turbulence

swirling action that disturbs smooth flow of liquid, occurs in heart chambers and great vessels, atherosclerotic plaques cause abnormal turbulence

systolic pressure

peak arterial pressure during ventricular systole

diastolic pressure

minimum arterial pressure during diastole

pulse pressure

difference between systolic pressure and diastolic pressure

mean arterial pressure

= diastolic pressure + 1/3 pulse pressure

120/80

normal blood pressure

hypertension

abnormally high blood pressure, over 140/90

hypotension

abnormally low blood pressure

elastic rebound

arterial walls stretch during systole, recoil during diastole, keep blood moving during diastole

respiratory pump

thoracic cavity action, inhaling decreases thoracic pressure, exhaling raises thoracic pressure which forces blood to the heart

diffusion, filtration, reabsorption

materials move across capillary walls by ___, ___, and ____

diffusion

movement of ions or molecules from high to lower concentration along a concentration gradient

filtration

driven by hydrostatic pressure, water and small solutes forced through capillary wall, leaves larger solutes in bloodstream

reabsoprtion

the result of osmotic pressure; blood colloid osmotic pressure equals pressure required to prevent osmosis; caused by suspended blood proteins that are too large to cross capillary walls

out of

net hydrostatic pressure forces water ____ a solution

into

net osmotic pressure forces water ___ a solution

autoregulation

causes immediate, localized homeostatic adjustments

neural mechanisms

respond quickly to changes at specific sites

endocrine mechanisms

direct long-term changes