It is the layer we see with our eyes. It contains no blood supply of its own—which is why you can shave your skin and not cause any bleeding despite losing many cells in the process.
The epidermis is itself divided into at least four separate parts. A fifth part is present in some areas of our body. In order from the deepest layer of the epidermis to the most superficial, these layers strata are the:.
Skin overview : Skin layers, of both hairy and hairless skin. Human skin: This image details the parts of the integumentary system. The stratum basale, also called the stratum germinativum, is the basal base layer of the epidermis.
This layer is one of the most important layers of our skin. This is because it contains the only cells of the epidermis that can divide via the process of mitosis, which means that skin cells germinate here, hence the word germinativum.
In this layer, the most numerous cells of the epidermis, called keratinocytes, arise thanks to mitosis. Keratinocytes produce the most important protein of the epidermis. This protein is appropriately called keratin. Keratin makes our skin tough and provides us with much-needed protection from microorganisms, physical harm, and chemical irritation. Millions of these new cells arise in the stratum basale on a daily basis. The newly produced cells push older cells into the upper layers of the epidermis with time.
As these older cells move up toward the surface, they change their shape, nuclear, and chemical composition. These changes are, in part, what give the strata their unique characteristics. The stratum basale is primarily made up of basal keratinocyte cells, which can be considered the stem cells of the epidermis. They divide to form the keratinocytes of the stratum spinosum, which migrate superficially.
From the stratum basale, the keratinocytes move into the stratum spinosum, a layer so called because its cells are spiny-shaped cells. From there the keratinocytes move into the next layer, called the stratum granulosum.
This layer gets its name from the fact that the cells located here contain many granules. The keratinocytes produce a lot of keratin in this layer—they become filled with keratin. This process is known as keratinization. The keratinocytes become flatter, more brittle, and lose their nuclei in the stratum granulosum as well.
Once the keratinocytes leave the stratum granulosum, they die and help form the stratum lucidum. This death occurs largely as a result of the distance the keratinocytes find themselves from the rich blood supply the cells of the stratum basale lie on top off. Devoid of nutrients and oxygen, the keratinocytes die as they are pushed towards the surface of our skin. This layer is only easily found in certain hairless parts of our body, namely the palms of our hands and the soles of our feet.
Meaning, the places where our skin is usually the thickest. From the stratum lucidum, the keratinocytes enter the next layer, called the stratum corneum the horny layer filled with cornified cells. This the only layer of skin we see with our eyes. The keratinocytes in this layer are called corneocytes. They are devoid of almost all of their water and they are completely devoid of a nucleus at this point.
Find out more about the four different types of cell found in the epidermis. The basal cell layer stratum basale , or stratum germinosum , is a single layer of cells, closest to the dermis. It is usually only in this layer that cells divide. Some of the dividing cells move up to the next layer. The prickle cell layer stratum spinosum is the next layer layers of cells.
The cells in these layers have lots of desmosomes, which anchor the cells to each other, and contain thick tufts of intermediate filaments keratin. When the cell shrinks slightly, during fixation, the desmosomes from neighbouring cells remain tightly bound to each other, and these connections look like 'prickles' or 'spines', hence the name prickle cells.
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Related Articles No related articles found See all Related Topics. This the only layer of skin we see with our eyes. The keratinocytes in this layer are called corneocytes. They are devoid of almost all of their water and they are completely devoid of a nucleus at this point. They are dead skin cells filled with the tough protein keratin.
In essence, they are a protein mass more so than they are a cell. The corneocytes serve as a hard protective layer against environmental trauma, such as abrasions, light, heat, chemicals, and microorganism. The cells of the stratum corneum are also surrounded by lipids fats that help repel water as well. These corneocytes are eventually shed into the environment and become part of the dandruff in our hair or the dust around us, which dust mites readily munch on.
This entire cycle, from new keratinocyte in the straum basale to a dead cell flaked off into the air, takes between 25—45 days. Layers of the Epidermis The epidermis is the outermost layer of our skin. In order from the deepest layer of the epidermis to the most superficial, these layers strata are the: Stratum basale Stratum spinosum Stratum granulosum Stratum lucidum Stratum corneum Skin overview : Skin layers, of both hairy and hairless skin.
Stratum Basale Human skin: This image details the parts of the integumentary system.
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