The composition of human skin

The composition of human skin

Human skin is composed of two layers, namely the epidermis and dermis. Epidermis and dermis can be bound to one another due to the ridge papilare dermis and epidermis.

The epidermis is the top layer of human skin and has a different thickness: 400-600 μm for a thick skin (the skin on the palms of the hands and feet) and 75-150 μm for thin skin (skin other than hands and feet, hair). In addition to epithelial cells, the epidermis is also composed of layers:

Melanocytes, the cells that produce melanin through the process of melanogenesis.

Langerhans cells, ie cells that are bone marrow derived macrophages, which stimulates T lymphocyte cells, binding, processing, and represents an antigen to T lymphocyte cells Thus, Langerhans cells play an important role in skin immunology.

Tues Merkel, the cells that function as mekanoreseptor sensory and related functions with diffuse neuroendocrine system.

Keratinocytes, which are layers of the outermost layer to innermost being as follows:

Stratum corneum, consists of 15-20 layers of flattened cells, without a nucleus with a cytoplasm filled with keratin.

Stratum lucidum, consisting of a thin layer of eosinophilic epidermal cells that are very flat, and dense cytoplasm terdri of keratin. Between cells are desmosom.

Granulosum stratum, composed of 3-5 layers of flattened polygonal cells containing granular cytoplasm keratohialin. In the granule cell membrane there is an issue lamella adhesive material between cells, acting as a selective filter against the entry of foreign materials, as well as providing a protective effect on the skin.

Spinosum stratum, composed of cells kuboid. Spinosum cells are held together with a filament, this filament has a function to maintain the cohesiveness (adhesiveness) between cells and fight the effects of abrasion. Thus, this spinosum cells numerous in areas that potentially have such friction soles.

Stratum Basal / Germinativum, a bottom layer of the epidermis, consists of a layer of cells kuboid. In the stratum basal mitotic activity occurs, so that this stratum is responsible for the renewal process of epidermal cells on an ongoing basis.

Dermis, the layer of skin below the epidermis, has a thickness that varies depending on the area of ​​the body and reaches a maximum of 4 mm in the back. Dermis is composed of two layers with no real limits, namely the stratum papilare and reticular stratum.

Papilare stratum, which is the main part of the dermal papilla, composed of loose connective tissue. In this stratum was found fibroblasts, mast cells, macrophages, and leukocytes out of the vessels (extravasation).

Retikulare stratum, which is thicker than the stratum papilare and composed of irregular dense connective tissue (mainly collagen type I)

In addition to the above second stratum, the dermis also contains several epidermal derivatives, namely hair follicles, sweat glands, and sebaceous glands

Hair, is a long berkeratin structures derived from epithelial invaginasi epidermis, the hair follicle. On the widening of the terminal follicles have shaped bumps on a papillary dermis. Dermal papilla contains a capillary and covered by cells that will form the hair cortex, hair cuticle, and hair root sheath.

Sweat glands, which consists of merokrin sweat glands and apocrine sweat glands

Merokrin sweat glands, in the form sipleks coiled tubular glands with the channel empties into the surface of the skin. The line is branched and has a diameter smaller than 0.4 mm of their secretions. There are two kinds of cells that surround the secretory mioepitel, the dark cells containing secretory granules and light cells that do not contain secretory granules.

Apocrine sweat glands, has a larger size (3-5 mm) of sweat glands merokrin. These glands are set in the dermis and hypodermis, and duktus empties into the hair follicle. There is in the armpit and anus.

Sebaceous gland, which is a gland holokrin, immersed in the dermis with the amount varying from one hundred to nine hundred per square centimeter. Secretions of the sebaceous glands are sebum, which is composed of a mixture of lipids include triglycerides, wax, squalene, and cholesterol and its esters.

At the bottom of the dermis, there is a loose connective tissue called the subcutaneous tissue containing fat cells that vary. This network is also called superficial fascia, or panikulus adiposus. This network contains a rich fabric of blood vessels and lymph vessels. Arteries that have formed two plexus, one of the stratum papilare and retikulare, another one between the dermis and subcutaneous tissue. The branches of the plexus is bloody papillae dermis. While venous plexus form three, two are located such as arteries, one in the mid-dermis. The lymph vessels have the same location with the arteries.

To support the skin function as a recipient of the stimulus, then there are many nerve endings, including the epidermis, hair follicles, cutaneous glands, dermis and subcutaneous tissue, and dermal papilla. These nerve endings responsive to stimuli such as palpation, pressure, tactile sensation, temperature high / low, pain, itching, and other sensations. These nerve endings include tip Ruffini, Vaterpacini, Meissner, and Krause.

Also leather is another derivative of the nail. Nails are plates have keratinepithelial cells on the dorsal surface of each distal phalanx. Nail plate lies in the stratum corneum, while the base of the nail lies in the basal and stratum spinosum.