Sebaceous are minute glands located in the skin, which secrete oily matter known as sebum that is essential to lubricate the skin and the hair. On the human body, the maximum number of glands is located on the scalp and the face. These glands are present on all parts of the body with the exception of the soles and the palms. Within the eyelids, meibomian sebaceous glands secrete specialized sebum in the tears. Sometimes, the sebaceous causes several medical conditions, such as acne, cysts, hyperplasia, adenoma and carcinoma.
Sebaceous glands are located in the hairy parts of the body and are attached to the hair follicles. A pilosebaceous unit comprises the hair, hair follicles, the arrector pili muscle, and the sebaceous glands. Although, it is a common belief that the glands protect the skin and the hair, there is no scientific research to prove the same. Most scientists believe that the sebaceous glands serve little purpose in the human body.
The components that make up the sebum are different in different mammals. In the human body, sebum comprises of the following; 25% wax monoesters, 41% triglycerides, 16% free fatty acids, and 12% squalene. A unique component in the human body is sapienic acid, which is a type of the sebum fatty acid.
The sebaceous glands undergo changes during the lifecycle of human body. The fetus within the uterus secretes a waxy substance known as Vernix caseosa, which is a white substance that coats the skin of a newborn baby. The increased levels of androgens during puberty cause the activities of these glands to increase. In the males, the glands appear on the penis, shaft, and the rim of the penile head. In the female body, the sebaceous glands are predominant in the labia minora.
Some of the common problems associated with overactive sebaceous glands include acne and keratosis pilaris. Sebum and keratin may create hyper-keratotic plug, micro-comedone within the skin pores. Isotretinoin is prescribed to reduce the secretion of sebum and is often used to treat acne. Often the glands are stimulated by certain steroids used by athletes causing severe acne on the face, neck, chest, shoulders, and back. Secretion of sebum may also be stimulated by piercing the body.
Some of the other medical conditions associated with these glands are sebaceous cyst, hyperplasia, carcinoma, and adenoma. These are caused due to several reasons, such as blockage or enlargement of the sebaceous glands.