The sebaceous glands are a tissue that releases oil in the skin of a mammal. When a piece of the epidermis is examined under a microscope, we see a hair follicle that pierces the surface of the skin to the subcutaneous layer. Inside there is a secretory sebaceous tissue. Waxy oil, which is excreted into the hair follicles, is called sebum. This oil lubricates the skin and the scalp of mammals.
Sebum is a mixture of fats (triglycerides, cholesterol, squalene, wax esters), debris and keratin. It creates a light oil film on the surface of our skin. If you’ve ever taken a picture of yourself and appeared shiny in the frame, it was the sebum that happened.
We best recognize sebum as a waxy substance on our faces and scalps before we jump into the shower.
But in fact, the sebaceous glands are found in every part of the skin, except for the lower lip, palms, and soles of the feet. There are two types of sebaceous glands: those that bind to the hair follicle and those that do not. These hair-follicular hairpins apply sebum to the hair that carries it along the length of the follicle. The ones that exist in the hairless areas of the skin are on the inside of the nose, the penis, and the labia. Similarly, Meibomian glands fill our eyelids and give off seborrhea in tears for extra weight and lubrication. The bottoms of the lymph nodes surround the nipples and protect the skin from drying or scaling.
At the base of each pore is the sebaceous gland. It has a mucoid structure because the pubic glands look like blueberry patches. These flakes or sacks give off an oily suspension.
The function of sebaceous glands
The main function of the fatty sebaceous gland is skin lubrication. This prevents loss of moisture. In turn, the skin stays moisturized and elastic. Without the sebum, the skin will dry and easily tear. Dry patches are more susceptible to infection because pathogens are able to penetrate the wounded skin. This proves the importance of sebum in maintaining intact skin.
On the other hand, the sebum in our hair makes our hair waterproof. As mentioned earlier, keratin is an important constituent of sebum (and hair). Water cannot penetrate or break the thread. Without the sebum, the hair would not have a protective barrier to prevent brittleness or even evaporation. Of course, evolutionarily, hair protects the skin from the harmful effects of the environment.
Tallow secreted by the sebaceous gland in humans consists mainly of triglycerides 41%, wax esters 26%, squalene 12% and free fatty acids 16%. The composition of sebum varies depending on the species. Wax esters and squalene are unique to sebum and are not produced as end products anywhere else in the body. Hydrochloric acid is a fatty acid sebum that is unique to humans and is involved in the development of acne. Sebum is odorless, but its decomposition by bacteria can cause strong odors. Dihydrotestosterone acts as a primary androgen in the prostate and hair follicles.
The immune function and nutrition
The sebaceous glands are an integral part of the body and are used to protect the body against germs. The sebaceous glands secrete acids that form an acidic coat. It is a very thin, slightly acidic film on the surface of the skin that acts as a barrier to bacteria, viruses and other potential contaminants that can penetrate the skin. Skin pH is between 4.5 and 6.2, and this acidity helps to neutralize the original character of impurities.
Acid lipids make a significant contribution to maintaining the integrity of the skin barrier and express both proinflammatory and anti-inflammatory properties. Sebum can act as a delivery system for antioxidants, antibacterial lipids, pheromones and hydration of the stratum corneum. The insoluble fatty acids contained in sebum have a wide antimicrobial activity. In addition, the secretion of sebaceous glands provides vitamin E to the upper layers of the facial skin.
Unique sebaceous glands
In the last three months of fetal development, the sebaceous glands of the fetus produce vernos caseosa, a waxy white substance that covers the skin to protect it from amniotic fluid.
The areolar glands are found in the shell, which surrounds the nipple in the woman’s breast. These glands secrete an oily fluid that lubricates the nipple and also release volatile compounds that are considered to be an olfactory stimulus for the newborn. During pregnancy and lactation, these glands, also called Montgomery glands, become enlarged.
Meibomian glands, on the eyelids, emit an eye layer of sebum called meibum, which slows the evaporation of tears. It also serves to create a tight seal when the eyes are closed and its lipid quality also prevents eyelids from sticking together. Meibomian glands are also known as the tarsal gland, the Zeis glands and the eyelid glands. They attach directly to the hair follicles of eyelashes, which are arranged vertically within the eyelids. Fordyce spots, or Fordyce granules, are ectopic sebaceous glands located on the genitals and oral mucosa. They show themselves as yellowish-white milia (milk stains). These secretions are sticky and have a high lipid content, which ensures good lubrication.
The development of sebaceous glands
The sebaceous gland is formed during late embryogenesis until the early stage of life. Usually begins her journey in the fourth month of pregnancy. Stem cells begin to differentiate in the outer root envelope (or ORS) and appear as protrusions or small bags from the hair shaft. When these cells disintegrate, they release their oily secretions. Genetics also affects the appearance of sebaceous glands.
In fact, a clear, waxy substance that after birth covers the skin of newborns is excreted from sebaceous glands. However, after birth, the sebaceous glands shrink until almost no activity. This changes after the age of six and reaches the peak of activity during adolescence. Gland activity is closely related to the level of the male hormone, testosterone.
Problems with sebaceous glands
Non-production or overproduction of sebum causes some complications. As with most processes, homeostatic control balances this delicate line. Unproductive glands will lead to skin rupture and infection. The possible breakdown of triglycerides in the bacterial tallow releases fatty acids that will trigger inflammatory changes or “pimples”. Similarly, overactive glands can cause seborrhoeic cysts. These are painful purulent pockets that form in the bile ducts when they clog. Unlike acne pellets, which are close to the surface of the skin, cysts will be deeper in the skin and painful to the touch due to the proximity of the skin nerves.