Circulatory System Histology

50 terms by monkey05 

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mesothelium

simple squamous epithelium lining both walls of the pericardial sac

endocardium

consists of 2 layers: endothelium and subendocardial CT; wraps around the internal structures of the heart

myocardium

contains layered cardiomyocytes that insert into the cardiac skeleton

endomysium

CT around each cardiac muscle fiber

perimysium

CT between the bundled cardiac layers

epicardium

consists of 2 layers: CT (subepicardium) layer and mesothelium (visceral layer of serious pericardium)

myocardial infarction

death of cardiac muscle cells due to ischemia;
scarring repairs heart wall since cardiac myocytes cannot be replaced; results in cardiac hypertrophy due to the increased size of individual cardiac myocytes (NOT increased # of cells)

chondroid

dense irregular CT with 'cartilage-like' cells

cardiac skeleton

dense irregular CT consisting fibrocollagen and chondroid; (1) attachment site for cardiac muscle, (2) AV separation facilitates conduction, (3) maintains valve patency

annulus fibrosus

CT rings around the openings of each valve; maintains their shape while holding them open

fibrous trigones
(R one is pierced by the AV bundle of HIS)

triangular CT between the valves; supportive structures

septum membranaceum

downward CT extension from trigone into top of IV septum

SA node

at junction of SVC and atria; pacemaker cells fire 70 bpm, (para)sympathetic inn MODIFY rate of depolarization (DONT initiate impulse b/c it's intrinsic)

AV node

found near atrial septum by tricuspid valve; follower cells that pick up the conduction signal

AV bundle of HIS

leave AV node, pierce R. trigone, and enter the IV septum where they divide into L and R branches

L and R bundle branches

travel down IV septum to supply their respective ventricles

subendocardial plexus

impulse from bundle branch runs from apex up toward the base allowing contraction to push blood toward outflow tracts

pacemaker cell

leaky cells (Na+ into cell causes depolarization wave thus initiating contraction); unstable RMP

follower cells

pick up depol. wave via gap junctions

purkinje fibers

modified cardiac muscle cells; start in bundle branches and go into the subendocardial plexus; lots of gap junctions for impulse transfer

tunica intima

simple squamous endothelial lining with a subendothelial CT and a fenestrated internal elastic lamina

tunica media

consists of circularly oriented SM, elastic and collagen fibers, external elastic lamina; prominent in arteries; replaced by pericytes in capillaries and venules; reduces lumen of the vessel

tunica adventita

dense irregular CT with vaso vasorum and longitudinally oriented elastic fibers ; prominent in veins; keeps vessels from distending

atherosclerosis

remodeling of the tunica intima into a thickened structure with fatty streaks (accumulated cholesterol in SM) and plaques; immune condition attracts macrophages which ingest LDL but inability to process LDL creates foam cells

vaso vasorum

blood supply to the larger BVs

elastic artery

large lumen, thin walls, numerous elastic lamellae; has a t. intima characterized by 40-70 layers of elastic sheets; func= maintain BP within vessel during diastole due to passive contraction of elastic lamellae; "conducting"

muscular artery

round lumen, prominent scalloped IEL, thick t.media made of 30-40 layers of SM; "distributing": regulate flow to diff. parts of the body as needed

arteriole

~IEL, no EEL, only 1-3 layers of SM, minimal t.adventitia; feeds the capillary bed to supply metarteriole or AV shunt

microvascular bed

consists of arterioles, true capillaries, central channel, venules, and AV shunts

metarteriole

beginning of the central channel; scattered SMCs; opens into true capillaries (which are smaller)

thoroughfare channel

distal end of the central channel; no SMCs; drains true capillaries into the venule

AV shunt

alternate channel that directly links the arteriole and venule; bypasses capillaries to conserve heat; 2-3 layers of SM

capillary

simple squamous epithelium; tube of endothelial cells; no media (no SM); some pericytes; func= thin-walled for rapid (transport and secretion) exchange with parenchyma

pericyte

myoepithelial cells on capillary and venule walls that form gap junctions for communication; contractile mech. aids in controlling the diameter of the capillary lumen

continuous capillary

found in muscle, CT, gut; connected by tight junctions, continuous basal lamina around the endothelium

fenestrated capillary

found in endocrine/exocrine glands, intestinal villi, pancreas, renal glomeruli; onnected by tight junctions, continuous basal lamina around the endothelium; holes perforating through the cytoplasm

discontinuous capillary

found in spleen, bone marrow, lymph nodes, liver; irregularly shaped with large gaps between endothelial cells; discontinuous basal lamina

endothelial cells

help form basal lamina; secrete collagen type IV; produce signals for extravasation and diapedesis; secrete substances that affect vascular tone; produce clotting factors

von willebrand factor

glycoprotein that promoted coagulation of platelets during clotting; found in weibel-palade (secretory) bodies of endothelial cells

von willebrand's disease

genetic disease that destroys VWF thus slowing down coagulation and causing excessive bleeding

venules

collects blood from capillary beds; companion to arterioles; irregular lumen, thinner but larger than arterioles; no media (no SM); WBCs like to exit here

medium sized veins

companion to muscular arteries; thinner but larger than than muscular arteries; ~IEL, no EEL, thick t.adventitia; only vessels that contains valves

valves

protrusions of the intima into the medium veinlumen of the vein; ensure unidirectional flow of blood; usually in extremities

leaflets

help direct blood flow back to the heart

valve sinus

dilation of the wall behind the leaflet; close and balloon out the leaflets when blood tries to back flow in the wrong direction

varicose veins

large tortuous (usually superficial) veins on surface of legs due to excess venous pressure; causes distention and dilation of vessel walls (leaflets dont meet to prevent backflow)

large veins

large, thin wall (vs. lumen), low P vessels that return blood to heart; no valves, longitudinally-oriented SM in adventitia, no IEL, reduced t.media thickness, thick t. adventitia; vaso vasorum

lymphatic capillary

delicate, have valves to direct fluid back to heart which is taken to nodes for filtering before returning it to the blood vascular system

L thoracic duct

begins as cisterna chyli at level of diaphragm; drains 2/3 body; drains into subclavian vein

R duct

drains upper 1/3 body into R subclavian vein

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