Anatomy Chapter 20: circulation
Terms in this set (92)
What are the 3 categories of blood vessels?
arteries, vein, and capillaries.
carry blood away from the heart
carry blood back to the heart
connect smallest arteries to the smallest veins
What are the three layers of the walls of the arteries and veins?
tunica interna or tunica intima, tunica media, and tunica externa
lines the inside of the vessel and is exposed to the blood. it consist of endothelium
acts as a selectively permeable barrier to materials entering or leaving the bloodstream; normally repels blood cells and platelets so that they can flow freely without sticking to vessel wall.
middle layer, thickets later. it consist of smooth muscle, collagen and in some cases elastic tissue
what is the function of the tunica media
it strengthens the vessels and prevents blood pressures from rupturing them and it produces vasomotion
changes in the diameter of a blood vessel
outermost later. It anchors the vessel and provides passage for small nerves, lymphatic vessels,and smaller blood vessels.
What are arteries built to withstand?
the surges of pressure created by the heart
What are the three types of arteries?
conducting (elastic or large) arteries, distributing ( muscular or medium), and resistance (small) arteries
large arteries alternating with thing layers of smooth muscle, collagen, and elastic fibers.
What is the main function of conducting arteries?
Their expansion takes some pressure off the blood so that smaller arteries downstream are subjected to less stress. Their recoil between heartbeats prevents the blood pressure from dropping to low.
medium arteries that distribute blood to specific organs. lots of smooth muscle.
small arteries that have smooth muscle and little elastic tissues.
short vessels that connect arterioles(small arterie) and capillaries
Three kinds of receptors in arteries.
Carotid Sinuses, Carotid bodies, and aortic bodies
respond to changes in blood pressure
they moniter changes in blood composition.
similar in function as carotid bodies
What is the function of capillaries?
allows nutrients, wastes, hormones, and leukocytes mass between blood and the tissue fluids through the walls of the vessels.
What are three kinds of capillaries?
continuous, fenestrated, and sinusoids capillaries.
occur in most tissues. small solutes can pass in them
have filtration pores that allow medium size solutes to pass through
irregular blood-filled spaces in the liver, bone marrow, spleen and other organs. Bigger things can pass through these capillaries.
capillaries organized into networks
open and close capillaries
thin walled and flaccid, and expand easily to accommodate increased volume in blood
Why are veins so thin?
being distant from ventricles of the heart, they are subjected to relatively low blood pressure
what is blood like in veins?
5 types of veins
postcapillary venules, muscular venules, medium veins, venous sinuses, and large veins.
smallest of veins. they receive blood from capillaries directly or by way of distal ends.
receive blood from the postcapillary venules
upward flow of blood. controls blood flow in muscles
thin walss, large lumens and no smooth muscle.
common route of blood
heat to arteries to capillaries to veins to heart
blood flows through two consecutive capillary networks before returning to the heart
point where two blood vessels merge
one vein empties directly into another vein
two arteries merge
the amount of blood flowing through an organ, tissue, or blood vessel in a given time
the flow per given volume
the physical principles of blood flow are based mainly on preseure and resistance.
blood pressure (BP)
the force that blood exerts against a vessel wall.
Where is the brachial artery located
contraction of heart
period in between contractions of the heart
difference in systolic and diastolic
why would it be bad if arteries were rigid tubes? what do healthy arteries do?
pressure would rise in the systole and drop nearly to zero in the diastole. Healthy arteries expand with each systole and absorb the force of ejected blood.
hardening of the arteries
growth of lipid desposits in arterial wall; blood pressure will rise
Bp is determined by what 3 variables?
cardiac output, blood volume, and resistance to flow
the opposition to flow that the blood encounters in vessels AWAY from the heart
pressure is affected by what two factors?
flow and resistance
3 variables of resistance
blood viscosity, vessel length, and vessel radius
why is vessel length important?
the farther a liquid travels through a tube, the more friction it encounters; pressure and flow decline
why is vessel radius important?
when a blood vessels dilates (widens), a greater portion of the blood is in the middle stream (blood flow is faster). When the vessel constricts, the average blood flow is slower
Where is blood flow the fastest?
in the center of a vessel
the narrowing of the vessel
widening of a vessel
what is the most significant factor in control over peripheral resistance?
3 ways of controlling vasomotion
local control, neural control, and hormonal control
autoregulation ( ability of tissues to regulate their own blood supplies)
when hormones control the blood pressure
vasomotor center- sympathatic control over blood vessels
an increase above the normal flow; local control
growth of new blood vessels; local control
2 purposes of vasomotion
raising or lowering of blood pressure and selectively modifying the perfusion of a particular organ and rerouting blood from one region of the body to another
refers to this two-way movement of fluid
3 routes chemicals pass through capillary walls by
the endothelial cell cytoplasm, intercellular clefts between endothelial cells, and filtration pores
the process in which endothelial cells pick up material on one side of the plasma membrane , transport it across the cell, and discharge the material
the physical force exerted by a liquid against a surface
the accumulation of excess fluid in a tissue
3 causes of edema
increased capillary filtration, reduced capillary reabsorption, and obstructed lymphatic drainage.
flow of blood back to the heart
what are 5 things that are important for venous return
the pressure gradient, gravity, the skeletal muscle pump, the thoracic pump and tcardiac suction
state where the cardiac output is insufficient to meet the body's metabolic needs
2 categories of circulatory shock
cardiogenic shock and low venous return shock (LVR)
3 forms of LVR
hypovolemic shock, obstructed venous return shock, and venous pooling shock
produced by loss of blood volume
obstructed venous return shock
occurs when any object is compressing the vein and impedes blood flow
venous pooling shock
occurs when have normal blood volume but too much of it accumulates in the lower body
brain blood flow
total blood flow to the brain fluctuates less than any other organ
how does the brain regulate its blood flow?
skeletal muscle flow
highly variable blood flow
what do muscular contractions do the blood vessels
compress them and slow the flow of blood
what is the main chemical stimulus for cerebral autoregulation?
pulmonary circuit (lungs)
arteries carry oxygen poor blood and veins carry oxygen rich blood.