Low-power micrograph showing the secretory segment of an two types of glands.
apocrine sweat gland. The sectioned profiles seen here represent several coiled branches of a single gland surrounded by dense connective tissue (DCT). In the upper part of this
Apocrine sweat gland, skin, human, H&E, ×256.
The epithelium (Ep) of the apocrine sweat gland from the boxed area to the left is simple columnar. The individual cells vary in height, and some show the bleb-like protrusions (B). At the base of the epithelium are the spindle-shaped myoepithelial cells. In some regions of the tubule, these cells have been cut longitudinally and thus appear as a deeply stained eosin band (EB). At other sites, the cells have been sectioned tangentially and appear as a series of parallel linear profiles (MyC).
Eccrine sweat gland, skin, human, H&E, ×512.
At this very high magnification, two cross-sectioned profiles of the secretory segment (SS) and one profile of the duct segment (DS) from the boxed area to the left are shown. When the tubule wall of the secretory segment is cut in a perpendicular plane, the simple columnar nature of the epithelium (Ep) is evident. Because the tubule is so tortuous, more often the epithelium appears to be multilayered. The myoepithelial cells of the secretory segment appear here both as a circumferential band (CB) and in a cross-sectioned array (CA) in which they resemble the teeth of a saw blade. Occasionally, myoepithelial cell nuclei (MyN) are present. Such profiles give the appearance of a pseudostratified epithelium. The duct segment (DS) lacks the myoepithelium and also differs in that it is stratified cuboidal. See next plate.
KEY A, apocrine gland B, bleb-like protrusions CA, cross-sectioned array CB, circumferential band D, dermis DCT, dense connective tissue DS, duct segment E, eccrine gland EB, eosin band Ep, epithelium H, hypodermis HF, hair follicle MyC, linear profiles of myoepithelial cells MyN, myoepithelial cell nuclei SG, sebaceous gland SS, secretory segment SwG, sweat glands
Normally, the body loses ~600 mL of water a day through evaporation from the lungs and skin. Under conditions of high ambient temperature, water loss is increased by an increased rate of sweating. This thermoregulatory sweating first occurs on the forehead and scalp, extends to the face and the rest of the body, and occurs last on the palms and soles. Emotional sweating, however, occurs first on the palms and soles and in the axillae. Sweating is under both nervous control through the autonomic nervous system and hormonal control. Sebaceous glands secrete sebum, an oily substance that coats the hair and skin surface. Sebaceous secretion is a holocrine secretion; the entire cell produces, and becomes filled with, the fatty secretory product while it simultaneously undergoes progressive disruption, fol-lowed by necrosis, as the product fills the cell. Both secretory product and cell debris are discharged into the pilosebaceous canal.
Sweat gland, skin, human, H&E ×1000.