Which layer contains melanocytes

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.

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. The dermis consists of a papillary and a reticular layer that serve to protect and cushion the body from stress and strain.

Lying underneath the epidermis—the most superficial layer of our skin—is the dermis sometimes called the corium. The dermis is a tough layer of skin. It is the layer of skin you touch when buying any leather goods. The dermis is composed of two layers. They are the papillary layer the upper layer and the reticular layer the lower layer. Human Skin: This image details the parts of the integumentary system.

The papillary layer provides the layer above it, the epidermis, with nutrients to produce skin cells called keratinocytes. It also helps regulate the temperature of our skin and thus the body as a whole. Both the nutrient supply and temperature regulation occur thanks to an extensive network of blood vessels in this layer.

These blood vessels also help remove cellular waste products that would otherwise kill the skin cells if they were allowed to accumulate. The pink tint to the skin of light-skinned individuals is due to the blood vessels found here.

In fact, when you blush, it is the dilation of these blood vessels that causes you to turn red. The reticular layer serves to strengthen the skin and also provides our skin with elasticity. Elasticity refers to how our skin is able to spring back into shape if deformed by something like a pinch.

The reticular layer also contains hair follicles, sweat glands, and sebaceous glands. The sweat gland can either be apocrine, such as those found in the armpits and the groin area, or the eccrine glands, which are found all over the body. The former help contribute to body odor along with the bacteria on our skin , and the latter help regulate our body temperature through the process of evaporation. Special stains are often required to tell the difference between melanocytes and Langerhans cells.

The Merkel cell is a fourth, less visible, epidermal cell. The epidermis forms an undulating appearance, with intermittent regular protrusions of the epidermis layer rete ridges or pegs into the upper layers of the underlying dermis.

In some areas of the body such as the palms and soles, the rete pegs are less pronounced. The pillars of dermis next to the rete pegs form the rete ridges. The small area of epidermis between rete pegs is called the suprapapillary plate. The keratinocytes become more mature or differentiated and accumulate keratin as they move outwards. They eventually fall or rub off. They form four distinct layers, described in the table below from the most superficial to the deepest.

Immediately below the epidermis is the basement membrane , a specialised structure that lies between the epidermis and dermis. It includes various protein structures linking the basal layer of keratinocytes to the basement membrane hemidesmosomes and the basement membrane to the underlying dermis anchoring fibrils. The basement membrane has an important role in making sure the epidermis sticks tightly to the underlying dermis. The epidermis gives rise to a number of specialised appendages also called adnexal structures or adnexae.

Hair and nails are both examples, i. The hair follicles are associated with sebaceous oil glands and arrector pili smooth muscle.

This muscle is responsible for goose bumps appearing on the skin in response to cold. The epidermis also gives rise to eccrine sweat glands, a tangle of tubules deep within the dermis that secrete a watery salt solution into a duct that ends on the skin surface. Larger apocrine sweat glands are found in the armpits and groin. Different areas of the body have different proportions of the adnexal and hair follicle structures present. For example:. Melanocytes are found in the basal layer of the epidermis.

These cells produce a pigment called melanin , which is responsible for different skin colour. Melanin is packaged into small parcels or melanosomes , which are then transferred to keratinocytes. Langerhans cells break the allergen into smaller pieces then migrate from the epidermis into the dermis. They find their way to lymphatics and blood vessels before eventually reaching the lymph nodes.

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