This video will cover the appendages of the skin, most of them being associated with the dermis. However, there's some crossover between different structures in the skin. So appendages is a term that means other structures that are associated with the skin.
So we're going to start off with the two major classifications of glands that we have in our dermis and what we'll notice about them is that they are basically there's two different types of gland there's the eccrine gland and then there's the sebaceous gland and at first glance you may not be able to tell them apart very easily but actually so this is a cross-section of an eccrine gland this is a cross-section of a sebaceous gland one of the ways you're going to be able to tell the sebaceous glands easily is that they are always associated with a hair follicle So whenever you see a hair follicle, you're going to see a little sebaceous gland there. And whenever you see a sebaceous gland, it will be with a hair follicle. So they always go hand in hand.
And they release their product to the surface of the skin. However, they release the product directly through the hair follicle. In contrast, the eccrine gland, which is shown here, is kind of more like a snake-like or little sinusoidal structure.
And it actually has a duct that leads directly to the surface of the skin. You can see that it's called a sweat pore. So this is where your perspiration comes from, from the eccrine glands.
All right, so let's start off with the pseudoriferous glands. Pseudoriferous make up all of the sweat glands. And there's two different types that we'll be discussing today, the eccrine glands shown here and then the apocrine glands, which are closely related.
There are... 3 to 4 million sweat glands on your body, 3 to 4 million pseudoriferous glands on your body, and they produce 500 milliliters or more of sweat per day. You can actually secrete as much as 12 liters of sweat per day.
So the eccrine gland, which is shown here, is the most common. These are found in the palms of the hand, the soles of the feet, and the forehead, and they are responsible for secreting sweat. Now, the product of sweat is basically water plus salts, some electrolytes.
And then there are also acid wastes of metabolism present here. Generally speaking, the acid wastes of metabolism are filtered through the kidneys. However, some of them are released through the eccrine glands as well, through the, sorry, through the pseudoriferous glands as well.
And that helps to keep your skin at a slightly acidic tone. So you know probably that the acid, uric acid, is secreted in your urine. Uric acid is also secreted in your sweat. So that's one example of acid waste that you'll find there.
Generally speaking, your sweat is usually also going to have a protein called dermcidin, which dermcidin is going to kill off things that are found in the epidermis. So there's two layers of protection. that are immediately garnered just through your sweat.
That slightly acidic concept that your sweat is slightly more acidic than water. It's slightly acidic. And Dermcidin, which basically kills off bacteria and anything else that it comes into contact with, both of these things garner protection to the outer surface of your skin. The second type of pseudoriferous gland is called the apocrine gland.
The apocrine gland is found in your axillary and anogenital areas. And it basically has sweat. So everything that sweat has, water, salts, acid weights and metabolism, dermcidin. But it also has lipids and proteins in it.
And that makes it a little bit different. This is secreted in response to stress and in response to sexual stimulation. The secretion itself is odorless, but that lipid and protein content is actually quite attractive to bacteria. And the bacteria come along and they begin to decompose the lipids and the proteins. They begin to actually consume them.
And then it's the decomposition of these structures that actually start to release a distinctive smell that we call body odor. There are two other types of pseudoriferous glands. The ceruminous glands release earwax within your ear canal, and the mammary glands, which secrete milk at certain times of life, especially in women. So there are actually four different types of pseudoriferous glands, but only two that we concentrated on.
The eccrine glands and the apocrine glands. And then just keep in mind that the ceruminous glands and the mammary glands are also types of pseudoriferous glands. Okay, the sebaceous glands.
The sebaceous glands are also called oil glands. So if the pseudoriferous glands are sweat glands, the sebaceous glands could be nicknamed as oil glands. These secrete a substance called sebum into the hair follicles, which helps to lubricate the hair and the skin.
And it also serves as a bactericide. So again, you have a substance that's secreted that is meant to fight off bacteria. All right, the third appendage of the skin is going to be the nail. The fingernail and the toenail, these are basically scale-like modifications of the epidermis.
In other words, they're made basically of keratin. In the case of nails, it is made of hard keratin, whereas the skin has a softer version of keratin. The nails are going to have cells in there that have a harder structure.
And I think the only thing I really wanted to point out here... There's a number of different structures you can take a look at here if you're interested in. There's a few pages in the book on nails.
But if you look down here, this is your nail matrix. This is where your nail is actually grown from. So it actually starts back kind of below the proximal nail fold where you kind of see the end of your nail. And the nail is born further back than that. And that's going to be important for a case study we're going to do in class.
Lastly, we have hair. Hair is a structure that, again, is keratin. You notice a pattern here.
Your epidermis is made of keratin, your fingernails are made of keratin, and your hair is made of keratin. In the case of hair, the keratin is in concentric circles. And again, it's hardened keratin, but it's in concentric circles. And it starts to grow out from... hair bulbs down below here.
So it undergoes mitosis at this level and it begins to grow. But this is going to be the only area where you actually have actively mitotic cells. After this point, it begins to grow out as deadened cells. So the cells are no longer living after they are grown from that level.
So they start to add to the basal level and then kind of grow superficially. The one structure I did want to point out is this structure here which is the erector pili muscle, sometimes called the pilierector muscle in one word, but you can see the spelling here erector pili muscle. The erector pili muscle is basically attached to the underside of the epidermis and then also to the shaft of the hair and pretty much every hair in your body is going to have an erector pili muscle, just a tiny little involuntary muscle.