Histology: Heart and Vessels Flashcards
arteries
blood away from heart
veins
blood toward heart
exchange at capillaries?
nutrient, oxygen, waste
capillary structure?
singe layer of simple squamous epithelium surrounded by basement membrane
endothelium
the simple squamous epithelium lining vessels
vessels?
all lined by epithelium
red blood cell diameters?
7.5 microns
vessel is 8 microns (barely fits!)
passive exchange
simple diffusion to capillaries
-small molecules (water-soluble) and water
pinocytotic exchange
transport soluble high molecular weight molecules across endothelial wall
invaginations of cell membrane on both inner and outer surfaces
diapedesis
ameboid migration movement that allows cells (WBCs and macrophages) to pass endothelium
also done by immune cells
capillary junctions
adjacent cell membranes joined by tight junctions
prevent fluid loss
-not a strong adhesion
white blood cells can break these tight junctions
red blood cells
can bend (flexible)
fenestrae
in some organ capillary endothelium
thin windows
-pores closed by diaphragm thinner than unit membrane
discontinuous capillary
sinusoid
pericytes
cells surrounding capillaries and small venules
supportive - angiogenesis and vessel repair
may have contractile properties
-possible cause for constriction of vessels
sinusoid
not continuous membrane (or basement membrane)
where you need an excessive amount of exchange
liver, spleen, bone marrow
disse space
in liver
-allows direct communication between vascular space and parenchyma of organ
things can move back and forth
phagocytic cells
in some sinusoids
-
kupffer cells
liver sinusoids
macrophages
bone marrow, spleen sinusoids
tunica intima
nearest lumen
tunica media
external to intima
tinuca adventita
outermost vessel coat
aka tunica externa
morphology tunica intima
endothelium surrounds lumen
basement membrane underlies endothelium
subendothelial connective tissue
fibroblasts and CT fibers some of which run longitudinally
inner elastic lamina
IEL
fenestarted layer composed of accumulated elastic fibers
outermost component of tunica intima
morphology of tunica media
consists largely of smooth muscle
also connective tissue fibers
circumferentially arranged
-numerous CT fibers formed by specialized smooth muscle cells
external elastic lamina
EEL
concentration of elastic fibers
form outermost component of tunica media
morphology of tunica adventitia
largely connective tissue of moderate density
longitudinally arranged**
formed by fibroblasts
merges with loose connective tissue
classifications of arteries
arterioles
medium sized - muscular arteries
large sized - elastic arteries
**continuous transitions between artery type
arteriole
has less than 5 layers of smooth muscle***
tunica intima - very thin
tunica media - 1-5 layers of smooth muscle
-control blood flow, regulate BP, no visible external elastic lamina
tunica adventitia - usually thinner than media (not well developed)
capillary
have no smooth muscle
medium arteries
muscular artery
tunica intima - small amount of subendothelial CT present, also a well-developed IEL
tunica media - 5-40 layers of smooth muscle
smaller arteries have lower elastic fiber content, larger arteries have increasing quantities of elastin
ANS control of smooth muscle regulates blood flow
tunica adventitia
-usually thinner than media, some elastic fiber near media, mostly composed of collagen
elastic lamina
produced by smooth muscles
help to create an elastic vessel
want it to be able to maintain size**
-efficient delivery
what is larger?
veins larger than artery
because it is lower pressure
large artery
elastic artery
tunica intima - endothelial cells may be polygonal
subendothelial CT relatively thick with many fibers
IEL present but not as distinct muscular arteries
tunica media - smooth muscle fibers, much elastic fiber accumulation
elastic lamina - numerous thin tubular elastic membranes
tunica adventitia - thinner than media, exclusively CT
radial artery
medium artery
verhoefs stain
silver staining
elastic fibers take it up
vasa vasorum
small nutrient arteries supplying walls of larger arteries
blood supply to the wall of larger vessels
carotid body
mass of epitheliod and nerve endings
found at biurcation of common carotid to internal and external
stimulates response in response to lowered blood O2
carotid sinus
dilation of internal carotid artery
contains specialized nerve endings
in response to blood pressure
vein classification
venules
-post-capillary and muscular
small veins
medium veins
large veins
pericytic venules
post-capillary venules
vein structure
tunica intima -diffuse IEL, only larger veins tunica media -major point of difference -not prominent layer in veins (but it is in arteries) tunca adventitia -where you find venous smooth muscle -thickest part of vein
valves
in medium veins
-and in lower limb
paired invagination of tunica intima
free edges face in direction of blood flow
have intimal core
-reinforced by collagen and elastic fibers
absent in portal systems
assist under low blood pressure
venule structure
tunica adventitia - thickest part
primarily
medium vein structure
see notes**
large vein structure
see notes**
vena cava, portal vein
arteries versus veins
see notes**
cardiac muscle
see notes**
