Page 424 - Atlas of Histology with Functional Correlations

ENDOTHELIUM

Forms a semipermeable barrier between blood and interstitial tissue
Pinocytotic vesicles in endothelium allow bidirectional movement of

molecules
Provides smooth surface for blood flow without damage to the platelets
Lined by glycocalyx and secretes prostacyclin to prevent platelet adhesion
and blood clotting

Produces nitrous oxide, which induces vasodilation
Produces endothelin proteins that counteract nitrous oxide and cause
vasoconstriction
Converts angiotensin I to angiotensin II, a vasoconstrictor that raises blood

pressure
Inactivates certain compounds, degrades lipoproteins, and produces growth
factors
Contains electron-dense Weibel-Palade bodies that store von Willebrand

factor
Releases von Willebrand factor during damage to increase platelet adhesion
and blood clotting

HEART WALL: ENDOCARDIUM,

MYOCARDIUM, AND EPICARDIUM

Pacemaker

Impulse conduction by specialized cardiac cells located in SA and AV nodes

SA and AV nodes located in the wall of the right atrium
SA node sets the pace for the heart and is the pacemaker of the heart
Impulse from SA node conducted via gap junctions to all heart musculature
AV bundles located on right and left sides of the interventricular septum

AV bundles become Purkinje fibers
Pacemaker activities influenced by autonomic nervous system (ANS) and
hormones
Sympathetic axons stimulate heart rate; parasympathetic nerves decrease

heart rate

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