Epidermis: Cell Types and Layers (Nursing)

00:01 The epidermis is made up of four different types of cells.

00:04 The first type of cell is an epithelial cell known as keratinocytes This creates a keratin layer which is very strong intermediate filament found inside of these cells.

00:18 A second type of cell found in the epidermis is melanocytes.

00:22 Melanocytes produces melanin which is the substance that allows us to block UV rays from the sun.

00:31 A third type of cell found in our epidermis are the Langerhan cells or the immune cells which are actually macrophages that help us to block bacteria that are trying to get inside of the body.

00:47 And finally, we have the tactile epithelial cells also referred to as Merkel cells These are going to help us with feeling or cutaneous sensations.

01:03 There are two different types of skin found in the integument.

01:09 The first type of skin is thin skin.

01:12 This is what covers the majority of our body and excludes the skin of our palms as well as the palmar surface of our digits and our toes.

01:23 The second type of skin which is going to cover the palms, digital surfaces of our digits and the the palms of our feet is going to be the thick skin.

01:33 This skin is hairless.

01:36 The epidermis is composed of multiple layers.

01:40 The thin skin contains four layers whereas the thick skin contains five layers.

01:46 Starting from the deepest layer of the epidermis we have the stratum basale.

01:51 The stratum basale is made up of stem cells and in this layer, we are going to be as close to the dermis as possible.

01:59 The reason why is because epithelial tissue is avascular meaning they do not have a source of nourishment, but the stratum basale is close to the dermis therefore it is nourished by the blood vessels in the dermis Also in this layer, is where we will find our melanocytes.

02:19 Just above or superficial to the stratum basale is the stratum spinosum.

02:25 The stratum spinosum is 8 to 10 layers of epithelial cells -keratinocytes specifically that are alive and well also being nourished from the dermal layer.

02:40 Just superficial to the stratum spinosum is the stratum granulosum.

02:45 This is a layer of about 3 to 5 keratinocytes.

02:50 The difference in this layer however, is now we are starting to transition from living cells in the epidermis to non-living cells.

02:59 The reason why is we are starting to be too far away from the nourishment of the dermis and so these cells do not have access to nutrients and so they are starting to die.

03:13 Now located in thick skin only, we have a layer called the stratum lucidum.

03:19 It is actually called the stratum lucidum because this layer appears clear when you look at these cells under the microscope Now the keratinocytes are starting to be flattened, they do not look as squamous as they used to and they're starting to look a little bit more flat.

03:38 There is about 4 to 6 layers of this strata.

03:44 And then finally, we have the stratum corneum.

03:47 The stratum corneum is made up of up to 50 layers of keratinocytes that are dead and pretty much flattened.

03:58 They have very little cytosol inside of these cells.

04:02 It is this layer that is constantly sloughing off as you go throughout life.

04:09 As the skin grows, it grows from that stratum basale layer where you have the stem cells up toward the stratum corneum.

04:17 So it's okay that these cells are breaking off or sloughing off because they are being replaced by the layers below.