Sebaceous glands are usually embedded in the dermis. Deep in the sebaceous glands cells are smaller with intact nuclei. Cell size increases with the accumulation of sebum as the cells are gradually displaced towards the opening of the gland into the hair follicle. The nuclei condense, become darker and irregularly shaped.
Sweat Glands
Two types of sweat glands are present in humans. They are distinguished by their secretory mechanism into merocrine (~eccrine) sweat glands and apocrine sweat glands. In addition, they differ in their detailed histological appearance and in the composition of the sweat they secrete.
Merocrine sweat glands are the only glands of the skin with a clearly defined biological function. They are of critical importance for the regulation of body temperature. The skin contains ~3,000,000 sweat gland which are found all over the body - with the exception of, once again, parts of the external genitalia.
Sweat glands are simple tubular glands. The secretory tubulus and the initial part of the excretory duct are coiled into a roughly spherical ball at the border between the dermis and hypodermis.
The secretory epithelium is cuboidal or low columnar. Two types of cells may be distinguished: a light type, which secretes the watery eccrine sweat, and a dark type, which may produce a mucin-like secretion. The cells have slightly different shapes and, as a result of the different shapes, the epithelium may appear pseudostratified.
A layer of myoepithelial cells is found between the secretory cells of the epithelium and the basement membrane.
The excretory duct has a stratified cuboidal epithelium (two layers of cells).