Page 412 - Atlas of Histology with Functional Correlations

FIGURE 10.11 ■ Wall of a large vein: portal vein (transverse section). Stain:
hematoxylin and eosin. Low magnification.

FIGURE 10.12 | Heart: Left Atrium,

Atrioventricular Valve, and Left Ventricle

(Longitudinal Section)

The wall of the heart consists of three layers: an inner endocardium, a middle

myocardium, and an outer epicardium. The endocardium consists of a simple
squamous endothelium and a thin subendothelial connective tissue. Deeper to the
endocardium is the subendocardial layer of connective tissue. Here are found

small blood vessels and Purkinje fibers. The subendocardial layer attaches to the
connective tissue endomysium of the cardiac muscle fibers. The myocardium is
the thickest layer and consists of cardiac muscle fibers. The epicardium consists
of a simple squamous mesothelium and an underlying subepicardial layer of
connective tissue. The subepicardial layer contains coronary blood vessels,

nerves, and adipose tissue.

A longitudinal section through the left side of the heart illustrates a portion
of the atrium (1), the cusps of the atrioventricular (mitral) valve (5), and a
section of the ventricle (19). The endocardium (1, 9) lines the cavities of the

atrium and the ventricle. Below the endocardium (1, 9) is the subendocardial
connective tissue (2). The myocardium (3, 19) in both the atrium (3) and the
ventricle (19) consists of cardiac muscle fibers.

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