Ever wonder how pimples appear? Is it simply a blocked pore or maybe a hair follicle? Is bacteria involved? Learn about the glands that cause acne and the glands that help you cool off in this lesson on sebaceous and sweat glands of the integumentary system.
You wake up to walk the dog and step outside into what feels like a sauna! Within minutes, you're sweating! Where does the sweat come from? Or, what about the oil that appears on your face as you go through the day (well, for those of us with oily skin, anyway)? And, why do you get all those pimples on your face?
The structures that perform these actions are located in your skin. And together, your skin, plus the accessory structures located in it, make up your integumentary system. In this lesson, we'll be looking at two of the accessory structures that secrete substances from inside your body to the outside, the sweat glands and the sebaceous (or oil) glands.
Both of these structures are considered to be exocrine glands because they secrete substances through ducts to the outside of the body.
Let's start with the sebaceous glands. These glands are more commonly referred to as oil glands because they secrete an oily liquid into the hair follicles or onto the surface of our skin. Let's take a look.
See this structure below?
The production of hair takes place in the hair follicle.
This is the hair follicle. That's where the production of hair takes place. Up on the side of the follicle is the sebaceous gland. It shares a common duct with the hair follicle. This is where it secretes an oily, lipid-based substance called sebum. You can remember it this way: sebaceous glands secrete sebum.
Some functions of sebum include:
- the inhibition of bacterial growth on the surface of the skin
- lubrication of our hair
- conditioning of our skin
But, not all sebaceous glands are alike! That's right; you have different types of sebaceous glands. But don't worry, the differences are pretty minor, and they still all secrete sebum, so their functions are the same.
The simplest sebaceous glands are called just that: simple sebaceous glands. These types of glands are the ones associated with a single hair follicle. They're considered simple because they share a single common duct with the hair follicle. The sebum from these glands is discharged into the hair follicle duct instead of directly onto the surface of the skin.
On the other hand, sebaceous follicles are larger forms of sebaceous glands. They are not associated with a hair follicle and discharge their sebum directly onto the surface of the skin. They also aren't as widespread as the simple glands, being found mostly on the face, the back, chest, nipples and genital regions.
So, what do you think happens if the ducts of sebaceous glands get blocked by dirt or dead skin cells? What might happen to all that sebum being secreted? Hmm, figured it out yet? Well, if you said pimples, then you are right!
When sebum starts to build up in the blocked duct, it creates pressure beneath the surface and the formation of a pimple! This can cause a bacterial infection and inflammation. When the pressure gets to be too much, the follicle can rupture, filling with fluid and that nasty white pus!
Okay, so we answered the question of how we get pimples and why our face gets oily, but what about sweating? Why do you get all sweaty in hot weather or while you're working out?
You probably know your body sweats as a way to cool itself off. As you work out, your muscles produce heat, and sweating helps your body keep its blood, brain and other organs at a normal temperature for functioning. But, did you know that you have different types of sweat glands?
Two types, to be exact, which are the apocrine and eccrine sweat glands. And, just like our sebaceous glands, they secrete their substances outside the body, onto the skin. Apocrine sweat glands are found in the smellier areas of your body! They are found in the armpits, on your scalp and in the pubic or genital region. Hmm, notice something else similar about all these areas? No? Well, if you think about it, they all contain hair! And, all apocrine sweat glands secrete their products into hair follicles.
Let's take a closer look. See that coiled up tube below?
Apocrine sweat glands produce odorous secretions.
That's a sweat gland, and apocrine sweat glands produce a more odorous secretion than eccrine sweat glands do. Hence the smellier areas of your body, and, since these glands start functioning at puberty, that's why your armpits all of sudden start to smell as you reach those teenage years. This secretion is usually produced during moments of emotional stress and, because it contains lipids (or fats), it makes a great food source for bacteria! This tends to increase the 'smelliness factor' produced in these areas and gives us the term 'stress sweat.'
The rest of your body has what we call eccrine (or merocrine) sweat glands. These glands secrete their substances directly onto the surface of the skin.
Hmm, see a common thread here? Did you notice the difference between the two sweat gland types and the difference between the two sebaceous glands? Both stem from where the secretions are released, either into a hair follicle or onto the skin surface.
Let's take a closer look at the eccrine glands. These glands, like our others, are located beneath the skin surface. They have the same coiled tube-like structure seen in the apocrine glands, but their ducts exit on the surface of the skin, as seen below, and they are slightly smaller in size.
Eccrine gland ducts exit on the surface of the skin.
These glands are a lot more numerous than the apocrine glands and can be found pretty much all over your body, with their highest concentration being on the palms of the hands and soles of the feet.
Unlike the apocrine glands, the secretion produced by eccrine glands is 99% water with a little bit of salt and other electrolytes thrown in, accounting for the salty taste.
When you step outside into that 100-plus-degree weather, or when your muscles produce too much heat as you're working out, your eccrine sweat glands work with your apocrine glands to cool your body surface, helping reduce body temperature.
Other functions include:
- getting rid of excess salt and electrolytes
- protection from environmental hazards by diluting chemicals that come in contact with the skin surface
- making it more difficult for microorganisms to camp out on the surface of your skin
Together, your sweat and sebaceous glands protect, condition and cool your skin surface. Simple sebaceous glands secrete an oily substance into the hair follicles of your skin. They're found almost all over your body; well, wherever you have hair, at least, while sebaceous follicles are found mostly on your face, back, chest, nipples and genital regions. These glands secrete oil directly onto the surface of the skin.
Sweat glands can also be divided into two types. Apocrine glands are associated with hair follicles, similar to the simple sebaceous glands. They can be found on your scalp, in your armpits and your pelvic region. They also tend to be more odorous than your eccrine (or merocrine) sweat glands. These secrete a sweat that is about 99% water and 1% salt and other electrolytes. They can be found all over your body, but mostly on the palms of your hands and soles of your feet.
And, don't forget that because both sebaceous and sweat glands secrete their products outside the body, they are called exocrine glands. You know, because their products are exiting the body. And, that's it - the answers to why you get pimples and sweat!
After reviewing this lesson, you'll have the ability to:
- Describe the two types of sebaceous glands and their functions
- Explain what causes pimples
- Identify the two types of sweat glands and their functions
- Define exocrine glands and explain why sebaceous and sweat glands are classified as exocrine glands