Definition
The sebaceous glands belong to the appendages of the skin. They serve to produce and excrete a secretion called sebum. This has the task of protecting the skin from dehydration and consists mainly of lipids and proteins. A special form of the sebaceous glands in the eye are the Meibomian glands. They are located at the back of the eyelid and produce the fat-rich part of the tear film.
Anatomy of the sebaceous glands of the eye
Sebaceous glands are found on the body mainly in connection with the hair sheaths, the so-called follicles, or hair roots. In the eye these are the eyelashes. In addition, there are so-called “free sebaceous glands”, which are not associated with follicles but are isolated in the upper layers of the eyelids.
The glands form small, sack-shaped cell accumulations on the sides of the follicles or in the upper layers of the skin. In contrast to other glands, they do not have their own excretory duct in which the cells secrete the secretion. Instead, the cells continue to fill up with secretion and are finally released as a whole to the outside.
This form of substance release is called holocrine. The sebum is then led outwards along the lashes and is distributed to the skin of the eyelids. The secretion of the meibomian glands also mixes with the tear fluid.
Function of sebaceous glands in the eye
The secretion of the sebaceous glands primarily performs a protective function. Due to its high content of lipids, it protects the skin and hair from drying out. It also makes them stable and more resistant to external influences.
The sebum supports the natural barrier function of the skin and thus helps to defend against pathogens and harmful substances such as chemicals. The secretion of the meibomian glands is of particular importance. After release from the glands, this combines with the tear fluid produced in the tear glands and forms the fat-rich part of the tear film.
This is necessary to prevent the tear film from evaporating quickly. Only then can sufficient moistening and supply of the cornea with nutrients be guaranteed. Furthermore, the tear fluid serves to compensate for irregularities on the corneal surface, to a certain extent, and thus to improve the optical properties of the eye.
It also has a cleaning function for the eye. All this can only function optimally if the natural composition of the tear film is guaranteed by the unrestricted function of the various glands. If the Meibom gland is permanently inflamed, a disease pattern called hailstone occurs. This disease is completely harmless, but has a negative impact on the cosmetic aspect.
