An Insight Into the Sebaceous Gland

The sebaceous gland is such an important gland!
It helps maintain the hydration of the skin and in fact, it provides up to 50% of fat to the barrier of the skin, protecting it against moisture loss and invasion of bacteria.
You will find this tiny gland over the entire surface of the skin, though it is not found on the palms of the hands, nor is it found on the soles of the feet. There is more coverage of sebaceous glands found on the facial area, the scalp, chest and mid back, which is why these areas are generally more prone to breakout activity.

If we compare the amount of sebaceous glands on the body to the face, there are many more found on the face with numbers between 400 to 900.

There are two types of sebaceous glands

1. Free sebaceous glands which are independent of the hair follicle. These are found in areas between the skin and mucous membranes. The vermillion border of the lips, eye lids, oral mucosa, digestive tract, and the areola.
   
   
2. The glands associated with hair are called the Pilosebaceous gland. These are found between the arrector pili muscle and the actual hair follicle itself. For that reason, pilosebaceous glands are only found in the dermis. One point to note is that there is no relationship between the thickness of the hair and the actual size of the pilosebaceous gland. These are the glands that are prominent on the face, forehead, chest and midback.

The gland is categorised as a holocrine gland, which is a type of exocrine gland; exocrine meaning to secrete a substance.

As we know, the substance secreted from our sebaceous glands is called sebum, which is made up of triglycerides, wax esters, squalene, and metabolites of fat-producing cells.
So how is sebum secreted? The sebaceous gland houses sebocyte cells, and sebum is released when the secretory cells degenerate.

The secretions are produced in the cytoplasm of the cell. The cell membrane ruptures with the build-up of sebum, the sebum is then released which destroys the cell. The Sebum is then secreted into the follicular duct that surrounds the hair shaft, where it then flows through the duct, out through the follicle and over the skin surface.

Androgens (or male hormones) are known to stimulate the sebocyte cell. This stimulation increases the flow of sebum which can ultimately result in these sticky cells blocking the skin’s hair follicles, trapping the sebum and leading to blockages. The blocked, oil-filled follicle then causes the bacteria normally found in the hair follicles to multiply, leading to inflammation, redness and pustules.
A bacteria called staphylococcus aureus being one of the main offending culprits in creating the inflammation.

There are many studies that have shown an overactive sebaceous gland contributes to the world’s number one skin condition which is acne. Because of sticky sebum, skin cells are not able to shed normally.
There are many other factors that have to be explored to fully understand the development of acne but the activity of the sebaceous gland is certainly a high consideration.
Increased sebum will also have an impact on essential fatty acids.
When sebum increases, EFAs will decrease, which then affects the cell membrane.
It is interesting to note that while lower levels of sebaceous gland activity can contribute to dry skin, it is not always the cause of dry skin.
As we age the number of sebaceous glands are the same throughout life, though the size of the glands and the activity of the gland will vary. Skins may become oily or dryer with age.

Yours in skin,

Gay Wardle