Core Concepts of Pediatrics. Anatomy of the Skin Epidermis The epidermis is the most superficial layer of the skin and provides the first barrier of protection from the invasion of substances into the body. The epidermis is subdivided into five layers or strata: stratum basale stratum spinosum stratum granulosum stratum lucidum stratum corneum Keratizination The principal cells of the epidermis are keratinocytes.
Thickness Epidermis varies in thickness throughout the body depending mainly on frictional forces and is thickest on the palms of the hands and soles of the feet, and thinnest in the face eyelids and genitalia.
Dermis and Subcutaneous Fat The dermis is a tough but elastic support structure that houses nerves, blood vessels, lymphatics, and cutaneous appendages pilosebaceous units, eccrine and apocrine sweat glands. This is a layer of adipocyte cells and connective tissue that stores large amounts of lipids and thus carries out the two important functions of energy storage and thermal insulation.
Click here to. Components of Cells. The Macromolecules. Skin Morphology. What the skin does. Notice that there are no hairs in this region. The photograph opposite shows a section through thick skin. Thick skin like this is only found in areas where there is a lot of abrasion - such as palms, fingertips, and soles of your feet.
Why do you think this is? You should notice that the dermis extends up into the epidermis in structures called dermal papillae. These have two functions. Second, in areas of thick skin like this, they provide a large surface area, to nourish the epidermal layer.
Don't forget the epidermis is a stratified squamous epithelium, so it does not have its own blood supply. It relies solely on the blood supply from the dermis. The dermis is a connective tissue layer, that contains collagen and elastin fibres, and fibroblasts, macrophages and adipocytes, as well as nerves, glands and hair follicles.
The dermis is tough, and is the layer used to make leather. This layer contains loose connective tissue, and it has many capillaries. It extends up into the epidermis in small projections called dermal papillae. This region also contains Meissners corpuscles, which are touch receptors, as well as free nerve endings non-myelinated that are sensitive to temperature.
The collagen bundles are woven into a coarse network. Thick skin is thicker due to it containing an extra layer in the epidermis, called the stratum lucidum. Thick skin actually has a thinner dermis layer than thin skin, but is still thicker due to the stratum lucidum layer present in the epidermis. Thick and thin skin appear differently under a microscope. Thin skin contains four layers in the epidermis, while thick skin contains a fifth layer. These layers include :. The stratum basale, also known as the stratum germinativum, is the deepest layer of the epidermis.
It is the layer just above the dermis. This layer continuously produces new skin cells. It also contains melanocytes, which are cells that produce skin pigment and help protect the skin from sun damage. The stratum spinosum consists of eight to ten layers of cells. People may refer to the stratum spinosum as the prickle cell layer because of the irregular structure of cells, which look like spines or prickles.
The stratum granulosum consists of three to five layers of cells. The stratum granulosum contains granules, which are rich in lipids. Only thick skin contains the stratum lucidum layer. The stratum lucidum is a thin, transparent layer consisting of two to three layers of cells. It contains a protein called eleidin. The stratum corneum is the upper layer of the epidermis. It consists of 20—30 layers of cells. It contains keratin and horny scales, which make it tougher and able to thicken into calluses.
The stratum corneum contains dead keratinocytes, which produce defensins. Defensins are strings of amino acids that protect the body from infection.
Connecting the dermis and epidermis are structures called dermal papillae.
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