Anatomy of Blood Vessels
College: Fourth year
Arteries
carry blood away from the heart
veins
drain tissues and return blood to heart
Gas exchange takes place
through the capillary walls
capillaries
-contact tissue cells and directly serve cellular needs
-endothelium w/sparse basal lamina
structure of blood vessel walls (arteries and veins)
tunica intima, tunica media, tunica externa
lumen
central blood-containing space
tunica intima
-endothelium lines lumen of all vessels
tunica media
-smooth muscle and sheets of elastin
-controlled by sympathetic nervous system
tunica externa
-collagen fibers protect and reinforce (connective tissue)
-nourishing layer
elastic (conducting) arteries
-large thick walled arteries with elastin in all three tunics
-pressure réservoirs-- expand and recoil as blood is ejected from the heart
muscular "pump"
contraction of skeletal muscles that "milk" blood through veins toward the heart
pressure changes that occur in the thorax during breathing
aid return of blood to the heart
the largest artery of the body
the aorta
the aorta is what type of artery
elastic (conducting) artery
muscular (distributing) arteries and arterioles
-distal to elastic arteries
-deliver blood to body organs
-have thick tunica media w/more smooth muscle
active in vasoconstriction
muscular (distributing) arteries and arterioles
arterioles
-smallest arteries
-lead to capillary beds & control flow into capilary beds by vasodilatation and vasoconstriction
Capillaries are in all tissues except
cartilage, epithelia, cornea and lens of eye
functions of capillaries
exchange of gases, nutrients, wastes, hormones, etc.
respiratory "pump"
pressure changes during breathing move blood toward heart by squeezing abdominal veins as thoracic veins expand
vasoconstriction of veins
under sympathetic control
venules
-formed when capillary beds unite
-very porous--allow fluids and WBCs into tissues
post-capillary venules consist of
endotheluum and a few pericytes
larger venules have
one or two layers of smooth muscle cells
veins
-formed when venules converge
-have thinner walls, larger lumens compared to corresponding arteries
blood pressure of veins
is lower than in arteries
Veins have a _________ tunica media and a thick _____ which consist of
-thin tunica media
-thick tunica externa
-consist of collagen fibers and elastic networks
vascular anastomoses
interconnections of blood vessels (networking)