Page 115 - Headlines Histology2024_Neat

primary source of a novel polypeptide hormone called atrial natriuretic
peptide (ANP). ANP induce diuresis (increase excretion of water from the
body), natriuresis (increase excretion of sodium from the body) and
vasorelaxant effect. ANP is a potent hypotensive agent and plays a crucial role
in the regulation of body fluid and electrolytes homeostasis.
• The Epicardium is the outermost layer and consists of outer mesothelium and
subepicardial layer of fibroelastic connective tissue supports the mesothelium.
• The subendocardial layer is connected to the myocardium by a broad layer of
adipose connective tissue containing branches of the coronary vessels and
autonomic nerves.

Cardiac skeleton

• The cardiac skeleton is a dense connective tissue layer to which atrial and
ventricular myocardiocytes are inserted and cardiac valves are connected. It
includes the annuli fibrosi or fibrous rings, the trigonum fibrosum and the
interventricular septum.

• The fibrous rings are dense connective tissue rings surround the
atrioventricular openings and those of the aorta and the pulmonary artery. They
serve to support the valves (mitral, tricuspid and semilunar valves).

• The trigonum fibrosum is a dense irregular connective tissue that fills the
space between the atrioventricular opening and the base of the aorta. It is
fibrocartilage in dog, hyaline cartilage in horse and bone in large ruminants.

• The interventricular septum consists of collagen bundles between the
ventricles.

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