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Block 4 Cardio Histo
Dr. Hill
32
Histology
Graduate
05/15/2012

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Cards

Term
tunica intima
Definition
innermost layer composed of endothelial cells with a thin underlying layer of connective tissue
Term
tunica media
Definition
middle layer composed of circular oriented smooth muscle cells
Term
tunica adventitia
Definition
outermost layer composed of connective tissue. usually merges with surrounding connective tissue of organ.
Term
elastic arteries
Definition
largest ones, near the heart that contain circumferential sheets and fenestrated sheets of elastic fibers primarily within tunica media. extra elastic fibers located in internal elastic lamina of intima and external elastic lamina of adventitia. allow stretching during systole and subsequent relaxation between systolic blood flow (important in moderatio of blood pressure)
Term
vasa vasorum
Definition
tunica media highly invested with blood vessels
Term
muscular arteries
Definition
derived as major branches off elastic arteries to supply organs and extremities. muscle important in constriction/dilation of the artery that allows direct role in controlling blood flow. smooth muscle of tunica media respons to nervous, hormonal and local metabolite stimuli. 3 tunicas plus internal and external elastic laminas very distinct
Term
arterioles
Definition
most distal branches of arterial system in which smooth muscle layer is still continuous. most important for controlling blood flow/pressure.
Term
metarterioles
Definition
small lumenal diameter and only occasional and scattered smooth muscle cells. important in controlling blood flow thru capillaries
Term
capillaries
Definition
smallest blood vessels of system with thinnest walls. site of all exchange. meshwork supplying all cells of the body. consists of endothelium and basal lamina (one cell thick)
Term
pericyte
Definition
multipotent cell occasionally found in capillaries that retain ability to differentiate into several other types of cells. important in repair.
Term
continuous capillaries
Definition
endothelia forms complete lining without any defects - most common type
Term
fenestrated capillaries
Definition
endothelia processes minute pores that renders capillary wall more permeable. found in GI tract, endocrine glands, kidney, choroid plexus.
Term
sinusoids
Definition
channels that are larger than normal capillaries and have a highly fenestrated basal lamina. found in liver, spleen, bone marrow, and some endocrine glands
Term
veins
Definition
large lumen and thin walls. tunicas less distinctly demarcated.
Term
low pressure system
Definition
need for valves in veins of legs to return blood to the heart
Term
cardiac muscle
Definition
striations like skeletal muscle, but not as full (nucleus centrally located). cylindrical cells that are often branched produces a woven or interlaced appearance. rich supply of capillaries
Term
atrial cells
Definition
type of cardiac muscle cells
Term
purkinje cells
Definition
larger cells, frothy central cytoplasm with few striations all located peripherally. component of cardiac conduction system
Term
intercalated discs
Definition
junctional complex connecting ends of adjascen cardiac muscle cells. desmosomes. adherent junctions.gap junctions.
Term
adherent junctions
Definition
actin fibers cross between cells
Term
gap junctions
Definition
allow greater coordination between cells
Term
cardiac tissue damage
Definition
no regeneration possible due to high degree of differentiation. lost tissue replaced by a connectie tissue scar.
Term
lymphatic vessels
Definition
run parallel for capillary and venous side of circulatory system. movement via muscle compression. requires valves to prevent backflow
Term
lymphatic capillaries
Definition
endothelial cells not tightly joined, edges loosely overlap. fibers anchor endothelial cells to surrounding structures, expose slits and keep vessels from collapsing when interstitial pressure increased. overlapping endothelial cells forms minivalves in lymphatic capillaries, prevents backflow.
Term
larger lymphatic vessels
Definition
extremely thin wall due to low pressure, vessel often partially collapsed in section. equipped with valves. typically found adjascent to circulatory vessels.
Term
endocardium
Definition
inner layer of simple squamous epithelial and supporting layer of fine connective tissue
Term
myocardium
Definition
middle layer of cardiac muscle. thickest layer. atria thinner. ventricle thicker. myocytes separated by rich capillary network.
Term
epicardium
Definition
outermost layer. synonymous with visceral pericardium. composed of simple squamous epithelial covering, underlying connective tissue contains copious amounts of adipose
Term
papillary muscles
Definition
provide tension for chordae tendinae
Term
chordae tendinae
Definition
collagenous and elastic structures that prevent prolapse of AV valves
Term
SA and AV nodes
Definition
composed of irregular twirling of small fibers that lack intercalated discs and are embedding in collagenous connective tissue
Term
purkinje cells
Definition
modified myocytes that act as terminal branches of cardiac conduction system in ventricles. located just deep to endocardium. cells typically larger than myocytes and often binucleated. less myofibrils. large glycogen stores surrounding nucleus (shows up as clear area around nucleus).
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