Skin Anatomy and Physiology – Glands of the Skin
The skin is the body’s largest organ, and as such, performs many key functions. It is a barrier, protecting the body from external elements, injury, and oxidation. It regulates body temperature through regulation of moisture loss, which helps the body adapt to changing ambient conditions. It also is your largest sensory organ and plays a tremendous role in the immune system, thanks to Merkel and Langerhan cells.
Skin care products play a large role in maintaining these key functions. As an example, sunscreen protects against UV radiation, and thus, premature ageing as well as preservation of the skin’s immune response. Moisturizers can reduce excessive bacteria, acne formation, and maintain a healthy barrier function, which reduces water loss from the skin that is associated with dehydration.
The presence of sweat glands also helps the body eliminate harmful substances from the metabolic activities of the intestines and liver. The skin is also loaded with glands that secrete hormones and respond to the other hormones in the body, for better or for worse.
The skin has a number of glands throughout. These are important for cooling, protection, and secreting substances that can be harmful if allowed to remain in the body for too long, such as cholesterol and minerals.
The most important glands that I will discuss in a bit of detail are the sebaceous glands (oil glands) as well as the sweat glands (eccrine and apocrine glands).
Sebaceous glands are attached to the same duct that contains the hair follicle (pilosebaceous duct), which is situated in the dermis — the second layer of skin. A complete pilosebaceous duct contains one hair follicle and one sebaceous gland, though some skin may contain multiple sebaceous glands per follicle, resulting in oilier skin. These sebaceous glands are responsible for the oil that is secreted onto the skin, and have ducts that open onto the upper portion of the follicle, near the top of the dermis. The face and the back contain the highest number of sebaceous glands per square inch, where the palms of the hands and soles of the feet contain none.
This oil prevents excessive evaporation of water, and contains some anti-fungal properties, but excessive oil can be associated with acne, while insufficient amounts are often associated with drier skin types.
Sweat glands are also abundant through the skin, and there are two types: apocrine and eccrine. Eccrine glands are the most common, found throughout the body as glands that open directly onto the skin as pores. As you can imagine, they are most commonly found on the palms of the hands and soles of the feet. They are also the glands that tend to be hyperactive in conditions like hyperhidrosis (excessive sweating). Apocrine glands are most commonly found in the “smellier” parts of the body, such as the armpits and groin. They are positioned along the hair follicle, above the sebaceous glands, and secrete their fluids out onto the hair and eventually, the skin. While the areas of these glands are most associated with having a particular smell, this is not due to the fluid being secreted, but the skin’s flora that is pushed out along the hair follicle with the fluid.
All sweat glands secrete fluids composed mainly of water, lactic acid, urea, waste, and bacteria-fighting substances, though the primary function of these glands is to cool and regulate body temperature, not just to remove waste from the body.
One common myth of all sweat glands is that sweat “purifies” the pore and thus, the skin, resulting in less acne or breakouts. Some people feel this is why they break out more when they work out. However, it is important to note that congestion — the plug that causes acne — in the pore occurs much deeper than where these glands are situated and sweat does not clean out this waste.
As I’ve noted before, skin is fairly acidic, maintaining a pH of roughly 4.4-5.6. This protective layer of sebum and perspiration from the glands forms a protective layer known as the “acid mantle.” Maintaining this mantle helps the skin ward off infection, prevents the growth of bacteria, and allows for normal exfoliation of the surface dead cells. This is why harsh skin care is especially damaging for skin, particularly harsh soaps.
Hopefully this was educational! Tomorrow, I will share with you about the layers of the skin — something I’ve discussed a bit on this blog but will go a bit more into depth on, including the skin cell types and how it all ties together to create this organ.