Lip

00:00 First of all, this is the section of the lip. It's taken through the lower lip as if the person is facing the left hand of the screen. On the middle of the lip is a very important muscle, the orbicularis oris that helps to move our lips to change the shape of our lips, and to help in speech, and also a part of the chewing mechanism and out in the mouth for food.

00:34 On the oral side of the lip, you can touch it with your finger. It's moist.

00:40 That's called the oral mucosa. And on the other surface that you can rub here is the skin surface. So it's important now that you orientate where you are looking at on this section through the lip. There's a border where the oral mucosa passes over and then blends on the exterior parts of the lip on the skin. And that transition zone is called the vermillion border. That's the part of the lip that you put lipstick on. In the central part of the lip labelled here, it's a bluey clear color, they're labial glands, tiny little salivary glands. You have them all throughout the oral cavity. And if you rung your tongue along the inside of your lip, you can feel little bumps, they are these labial glands or very small salivary glands that help moisten the oral cavity.

01:41 You don't see those on the surface of the lip, up near the vermillion border where you put your lipstick. So you have to continually lick your lips to keep that surface moist.

01:54 There are no glands there. What I'd like you to do now is concentrate on the oral mucosa labelled there.

02:02 What stains there, the dark-purple color, is the epithelium. It's a stratified squamous epithelium, the sort of epithelium that's specialized to resist abrasion and wear and tear, which is ideal for the oral cavity. It's ideal as being the oral mucosa. It actually adheres very tightly to the underlying lamina propria, which in this case, is not very loose connective tissue. It's rather dense collagenous connective tissue. To make sure that oral mucosa is very strong during the chewing process and to resist the abrasion from food moving about inside the oral cavity.

02:47 It's a lot thicker, as you can see, than the skin on the exterior surface of the lip. If you look at the skin on the exterior surface of the lip, you will find there are hair follicles there, sebaceous glands and sweat glands. You don't have those of course in the oral mucosa.