Corpus: Sebaceous gland

The sebaceous glands are epithelial skin appendages that serve to secrete sebum, which protects the skin against dehydration. They are holocrine glands that are made up of several small glandular lobules. Their cellular basis are the sebocytes.

Sebaceous glands are found almost all over the body. They are found either together with hair or isolated as so-called "free" sebaceous glands. Free sebaceous glands are only found on the following parts of the body:

• Anus
• Eyelids
• Glans penis
• prepuce
• Labia minora
• lips

However, sebaceous glands are associated with hairs on most of the body surface covered with field skin. There is an average of 40 sebaceous glands per square centimetre of field skin.

Sebaceous glands are multi-layered, flask-shaped glands that have no recognisable lumen. Their secreting end piece is located in the corium. In their periphery there are a variety of cell shapes, which can be cubic or flattened. In the centre of the gland, sebum mixed with cell debris can be seen under the light microscope. The basal cells are mitotically active, in the overlying layers the cells form lipid droplets and the cell nuclei slowly become pyknotic.

Sebaceous glands produce a fatty secretion known as sebum. It consists of triglycerides, fatty acids and wax esters and serves to lubricate and protect the epidermis.

Reduced sebum production is called sebostasis, overproduction is called seborrhoea. Sebaceous glands are often a starting point for bacterial infections, which then lead to clinical pictures such as acne or hordeolum. In rare cases, the cells that make up sebaceous glands can degenerate into malignant tumours. This results in a sebaceous gland carcinoma.