The integumentary system consists of the skin and its appendages, including the hair, nails, and glands. There are two main types of glands found in the skin: sweat glands and sebaceous (oil) glands.
Both of these glands originate in the epidermis (the outermost layer of the skin) and grow down into the dermis and even hypodermis during fetal development.
Sweat Glands Anatomy
First, let’s talk about sweat glands. The skin contains two main types of sweat glands, which are also called sudoriferous glands (from the Latin, meaning “bearing sweat”):
- Eccrine glands are found almost everywhere on the skin’s surface, but they are especially concentrated on the palms of the hand, soles of the feet, and head. If you ever have sweaty palms, you can thank your eccrine glands for that! These tubular glands have a coiled appearance and secrete a watery substance through a pore on the skin’s surface, and they become functional soon after birth. The primary function of eccrine glands is to help cool the skin, but they also secrete up to 1% of salts, waste, and other compounds that inhibit the growth of pathogens.
- Apocrine glands are the sweat glands found primarily in the armpits, anus, and genital regions. These glands secrete a milky substance rich in protein that stinks after bacterial decomposition. Whereas eccrine glands have pores that open on the skin’s surface, apocrine glands secrete their milky substance through openings in hair follicles, and they don’t become active until hormonal changes during puberty.
Here’s a really easy way to remember the difference between apocrine and eccrine sweat glands. Just remember that apocrine starts with an “a” because those glands are mostly found in the armpits and anogenital (anus and genital) region (which also start with an “a”). And since you grow hair in those areas during puberty, that can help you remember when apocrine glands become active. Eccrine starts with “e” because they are almost EVERYWHERE else on the skin!
Modified Apocrine Sweat Glands
There are also special subtypes of apocrine glands in the skin, which are called modified sweat glands:
- Ceruminous glands work with the oil-secreting sebaceous glands to create earwax (cerumen) in the ear, which provides important functions such as lubrication and waterproofing of the ear canal, protection against pathogens and debris, and more. These glands start with “cerum,” which helps you remember that they produce cerumen.
- Ciliary glands are found along the eyelid and work with oil-secreting sebaceous glands to keep eyelashes flexible. When something is silly you roll your eyes, so that can help you remember where ciliary glands are located.
- Mammary glands are specialized glands that secrete milk. The word mammary refers to breasts. Although males also have these glands, they typically only become active in females during and after a pregnancy, especially soon after giving birth (We have a video on breastfeeding tips.)
All of the sweat glands that I just covered release their contents through exocytosis, where the contents transfer from inside the cell to outside the cell. The secretion type is called merocrine secretion, which simply means that the cell remains unharmed and intact during the secretion process.
So to recap, the one of the main types of glands found in the skin are sweat glands, including the special modified apocrine sweat glands known as ceruminous glands (located in the ear), ciliary glands (located along the eyelid), and mammary glands (located in the breast).
Sebaceous Glands
The second type of gland found in the skin is the sebaceous oil gland. These glands produce sebum, an oily substance that helps lubricate the skin and hair. Sebum also helps the skin retain water.
You’ll notice that sebaceous and sebum both start with “seb,” so that’s an easy way to remember what these glands produce.
Sebaceous glands are found throughout the skin, except for the palms of the hands and soles of the feet. Remember, eccrine sweat glands are found in abundance in those areas, but you’re generally not going to find sebaceous glands there.
These glands form in grape-like clusters and are made up of acini cells, which eventually become full and rupture, releasing sebum into a small duct that connects to a main central duct in the hair follicle.
Unlike the sweat glands, this type of secretion is known as holocrine secretion, because the cells are damaged as they rupture and release their contents. (Remember, sweat glands do not rupture during their merocrine type secretion, but instead release contents via exocytosis.)
Similar to the apocrine sweat glands, these glands typically become active during puberty. Just think about how your skin tends to get greasy and form more pimples when you hit puberty—you can thank sebaceous glands for that!
These glands most commonly attach to hair follicles. However, sebaceous glands are also present in some areas without hair, in which case they secrete sebum through a pore in the skin.
Free Quiz and More Anatomy Videos
Take a free skin gland anatomy quiz to test your knowledge, or review our skin gland anatomy video. In addition, you might want to watch our anatomy and physiology lectures on YouTube, or check our anatomy and physiology notes.