Lecture 23: Heart Vessels Microstructure, Content (1/2) Flashcards
flow of blood, from capillary to vein
capillary > poscapillary venule > venule > small (muscular) vein > medium (muscular) vein > large vein
walls of arteries/large veins
3 concentric layers, called tunics
tunics of blood vessel walls
tunica intima (inner) tunica media (middle) tunica adventitia (out)
characteristics of tunica intima
endothelium and its basement membrane
subendothelial CT
internal elastic lamina
tunica media characteristics
elastic fiber - external elastic lamina; collagen fiber, ground substance, smooth muscle cells
vasa vasorum
vessels of the vessel
associated with walls of arteries
what mediates vasoconstriction of the vessel wall?
smooth muscles in the t. media’s postganglionic sympathetic nerves
laminae
sheaths/layers of fenestrated elastic membrane that make up artery wall
elastic artery (i.e. aorta) characteristics
40-70 sheets of fenestrated elastic membranes (laminae)
external and internal elastic lamina, not conscpicious
vasa vasorum and nerves in t. adventitia
what has thinner t. media- elastic artery or large vein?
large vein
what can be described as physiologically conducting vessels?
elastic arteries
how elastic arteries work, physiologically
aorta and its major branches
lots of elastic tissue in wall –> distend as fill with blood during systole
during diastole (while heart fills), elastic recoil of artery –> blood moves along vessels –> maintains arterial pressure
examples of large veins
superior venae cavae, inferior venae cavae
what could be called reservoir vessels or compliance vessels?
veins
how veins work, physiologically
pressure in venous system is low, continues to drop as veins go to heart
vein walls are thin, distensible, compliant; they act as reservoir for blood collected from other vasculature
neurovascular bundle
artery, vein, nerve together
what type of artery/vein tend to go together?
muscular artery, medium muscular vein
does muscular artery or medium vein have thicker wall?
artery
does muscular artery or medium vein t. media have more elastic fiber?
vein
how many layers of smooth muscle in t. media of muscular artery?
up to 40
muscular artery or medium vein have larger t. adventitia?
muscular artery
examples of muscular arteries
brachial, femoral, coronary arteries
characteristics of muscular arteries
large proportion of muscle, low resistance to blood flow, allows rapid blood distribution to tissues
divisions of muscular arteries
branching muscular arteries > small muscular arteries > arterioles
medium veins characteristics
companion veins of muscular arteries
have valves
are collecting vessels (from arterial system)
distributing arteries
muscular arteries
what tissue layer forms valve of medium veins?
t. intima
how does valve of medium vein work?
valve opens; pushes blood upstream; gravity causes blood to backflow; backflow facilitates valve’s closing
IEL
internal elastic lamina
outermost part of t. intima
elastic tissue
how many smooth muscle layers in t.media of small (muscular) artery?
3-10
how many smooth muscle layers in t.media of small (muscular) vein?
few smooth muscles in wall
how many smooth muscle layers in t.media of small (muscular) arteriole?
1-3
how many smooth muscle layers in t.media of small (muscular) venule?
few
has very irregular lumen
what do arterioles control?
systemic blood pressure
what controls arteriole diameter?
contraction of smooth muscle in response to sympathetic neural and non-neural stimuli
what does arteriole contraction cause?
increases resistance to blood flow; pressure in muscular and elastic arteries rule
what are resistance vessels?
arterioles
microcirculation flow
from heart > artery > arteriole > capillary bed > venule > vein > to heart
how many RBC can capillary lumen accommodate?
1
characteristics of postcapillary venules
10-25 um diameter; 3x capillary
endothelium more permeable than capillary
where WBC emigrate from blood circulation, esp during inflammation
what vessels handle inflammation?
postcapillary venules
what are pericytes
replace smooth muscle cells in postcapillary venules, capillaries
contractile proteins (actin, myosin, tropomyosin)
regulates blood flow through capillaries
can differentiate into smooth muscle, endothelial cells in response to injury or stimulation by growth factors
capillaries
site of gas, fluid, nutrient, metabolic waste exchange between blood/tissue
are metabolic exchange vessels
continuous capillaries
muscles, brain, lungs, bone
fenestrated capillaries
intestines, endocrine glands, kidneys
fenestrations in endothelial cells, continuous basal lamina
rapid transport of fluid, nutrients, hormones from tissue of cell/organ into circulation
discontinuous (sinusoids) capillaries
liver, bone marrow, spleen
what does liver sinusoid have
fenestrated endothelium so have bidirectional flow between hepatocyte and cytosol
no basement membrane
