Stratum basale (also called the stratum germinativum).Stratum lucidum (only in palms and soles).The epidermis can be further subdivided into the following strata or layers (beginning with the outermost layer): Keratinocytes are the major cells, constituting 95% of the epidermis, while Merkel cells, melanocytes and Langerhans cells are also present. It forms a protective barrier over the body's surface, responsible for keeping water in the body and preventing pathogens from entering, and is a stratified squamous epithelium, composed of proliferating basal and differentiated suprabasal keratinocytes. The epidermis is composed of the outermost layers of the skin.
#The skin deep app skin#
Amphibian skin plays key roles in everyday survival and their ability to exploit a wide range of habitats and ecological conditions. For example, a frog sitting in an anesthetic solution would be sedated quickly as the chemical diffuses through its skin. Amphibian skin is not a strong barrier, especially regarding the passage of chemicals via skin, and is often subject to osmosis and diffusive forces. Reptiles and most fish have hard protective scales on their skin for protection, and birds have hard feathers, all made of tough beta-keratins. On some animals, the skin is very hard and thick and can be processed to create leather. Primarily, fur augments the insulation the skin provides but can also serve as a secondary sexual characteristic or as camouflage. The speed and quality of wound healing in skin is promoted by the reception of estrogen. The skin on the palms and the soles of the feet is the thickest skin on the body as 4 mm thick. In humans, for example, the skin located under the eyes and around the eyelids is the thinnest skin on the body at 0.5 mm thick and is one of the first areas to show signs of aging such as "crows feet" and wrinkles. The thickness of skin also varies from location to location on an organism. This is sometimes discoloured and depigmented. Severely damaged skin may heal by forming scar tissue. Its other functions are insulation, temperature regulation, sensation, and the production of vitamin D folates. For example, the skin plays a key role in protecting the body against pathogens and excessive water loss. The skin interfaces with the environment and is the first line of defense from external factors.
Īll mammals have some hair on their skin, even marine mammals like whales, dolphins, and porpoises that appear to be hairless. Skin (including cutaneous and subcutaneous tissues) plays crucial roles in formation, structure, and function of extraskeletal apparatus such as horns of bovids (e.g., cattle) and rhinos, cervids' antlers, giraffids' ossicones, armadillos' osteoderm, and os penis/ os clitoris. Skin of a different nature exists in amphibians, reptiles, and birds. In mammals, the skin is an organ of the integumentary system made up of multiple layers of ectodermal tissue and guards the underlying muscles, bones, ligaments, and internal organs.
The adjective cutaneous means "of the skin" (from Latin cutis 'skin'). Other animal coverings, such as the arthropod exoskeleton, have different developmental origin, structure and chemical composition. Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
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