Sebaceous Glands - Pictures, Function, Types, Location
What are Sebaceous Glands?
The sebaceous glands are minute glands of the skin. It is distributed in the entire skin of the human body except for the palms of the hands and soles of the feet.
The skin is the soft covering of the human body and is the largest organ that makes up the integumentary system. It is made up of multiple layers that protect the fundamental muscles, joints, ligaments and other internal organs of the body from harm and infection. It serves as the first of defense of the human body against the external factors from the environment that can potentially harm the human body. The skin also protects and regulates the temperature of the human body and is also responsible for sensing both hot and cold temperatures.
The sebaceous gland is attached to the hair follicles of the skin and together with the arrector pili muscle made up the pilosebaceous unit. This pilosebaceous unit is generally found on the surface of the human skin. The sebaceous gland begins to form during the embryonic development exactly on the 4th month of gestation. It is well-developed and large in size at birth and decrease or shrinks in size during the childhood stage. The sebaceous gland will once again enlarge and become more and more active as a result of increase in the production of androgen and reaches its maximum production by the third decade of life where it will begin to slow down as the age advances.
Sebaceous gland is the only existing holocrine gland found in the human body. The holocrine gland is composed of acini or the small clusters of cell. It is a type of exocrine gland that uses ducts to secrete the completely broken down cells away from the body through a specific location.
Types of Sebaceous glands
There are different types of sebaceous glands that are classified according to the location of their existence. They may have different names but they all carry the same function in the specific areas they are located.
Fordyce’s spot is a type of sebaceous gland that is often located in the epithelial surface of modified skin such as the lips and the buccal mucosa. This spot is characterized as yellow white spot or pale red spot that initially develop on the epithelial surface during the stage of puberty. The name Fordyce’s spot is rooted from the name of a dermatologist Dr. John Fordyce who first identified and described the spots. The gland is also known as an "ectopic sebaceous gland" due to the abnormality in existence in modified skin.
Tyson gland or preputial glands are modified sebaceous gland found on the prepuce of the human penis particularly in the corona and the inner surface. The gland was named after Edward Tyson who first noted the existence of this gland. It is believed that the secretion of this gland is among the component of smegma. It can also be found in the female clitoris particularly in the folds of the labia minora and in the region of the clitoris.
Montgomery gland is also known as "areolar glands" or "Glands of Montgomery" and can be found in the nipple of both breasts particularly in the area of the areola. The gland was named after an Irish pediatrician, Dr. William Fetherstone Montgomery, who first identified and described the glands. The prominence of the gland is highly observed when the breasts are stimulated and is more pronounced during pregnancy. The amount of glands in the nipple varies and usually average about 4 to 28 round bumps per nipple.
Meibomian gland is also known as "tarsal gland". This is a special type of sebaceous gland located at the rim of the eyelids within the tarsal plate. This gland was named after a German physician named Heinrich Meibom who first identified and described the gland.
Sebaceous gland exists in the entire skin of the human body which serves different functions according to the needs of the part where the glands are located. The largest sebaceous gland and the enormous amount of glands are generally found on the face, chest, back and the skin on the upper outer arms.
Face has a great amount of sebaceous glands that explains why the face have an oily characteristic. It is widely distributed on the face with about three thousand of glands per square inch of the skin on the face.
Scalp is the soft tissue that covers the cranium. It borders the face anteriorly and the neck posteriorly. The layer of the scalp where the skin grows composed of a large amount of sebaceous glands and hair follicles.
The sebaceous gland in the eyes can be located both in the upper and lower rim of the eyelids inside the tarsal plate. The lower eyelids have an average of 25 sebaceous glands while the upper eyelid has about 50 sebaceous glands.
The sebaceous gland in this location is described to have a pale red or whitish discoloration of tiny raised spots. The size of the bumps is about 1mm to 3mm in diameter and is distributed in the vermillion border of the lips.
The sebaceous gland in the male genitalia is usually found on the shaft of the penis, around the corona and in the inner surface of the prepuce of the penis. In female genitalia, the sebaceous gland can be found in the folds of the labia minora and the skin surrounding the clitoris.
The sebaceous glands in the nipple are the round bumps in the areola and on the nipples of both breasts. The number of sebaceous glands in the nipple can vary and can be fewer than 5 glands or more than 20 sebaceous glands per nipple.
The sebaceous gland is responsible for secreting an oily or waxy substance called sebum. It is secreted by the gland to protect the skin from becoming dry and keep the skin moist. The secretion of sebum on the scalp is to keep it from drying including the hair. The oily substance in the rim of the upper and lower eyelids protects the tear film of the eye by preventing its evaporation. The sebaceous gland also plays an important role through secretion of sebum responsible in lubricating both the areola and the nipple and also serve to stimulate the olfactory of newborn babies.