Layers of the skin
The integumentary system is the largest organ system. In humans, this system accounts for about 16 percent of total body weight and covers 1.5-2m2 of surface area.It distinguishes, separates, protects and informs the animal with regard to its surroundings. Small-bodied invertebrates of aquatic or continually moist habitats respire using the outer layer (integument). This gas exchange system, where gases simply diffuse into and out of the interstitial fluid, is called integumentary exchange.
The human skin (integumentary) is composed of a minimum of 3 major layers of tissue, the Epidermis, the Dermis and Hypodermis. The Dermis comprises two sections, the Papillary and Reticular layers; they contain connective tissues, vessels, glands, follicles, hair roots, sensory nerve endings, and muscular tissue. The third layer is the Hypodermis and it is made up of adipose tissue.
The human skin (integumentary) is composed of a minimum of 3 major layers of tissue, the Epidermis, the Dermis and Hypodermis. The Dermis comprises two sections, the Papillary and Reticular layers; they contain connective tissues, vessels, glands, follicles, hair roots, sensory nerve endings, and muscular tissue. The third layer is the Hypodermis and it is made up of adipose tissue.
Epidermis
This is the top layer of skin made up of epithelial cells. It does not contain blood vessels. Its main function is protection, absorption of nutrients, and homeostasis. In structure, it consists of a keratinized stratified squamous epithelium comprising four types of cells:keratinocytes, melanocytes, Merkel cells, and Langerhans' cells. The major cell of the epidermis is the keratinocyte, which produces keratin.Keratin is a fibrous protein that aids in protection. Keratin is also a water-proofing protein. Millions of dead keratinocytes rub off daily. The majority of the skin on the body is keratinized, meaning waterproofed. The only skin on the body that is non-keratinized is the lining of skin on the inside of the mouth. Non-keratinized cells allow water to "stay" atop the structure.
The protein keratin stiffens epidermal tissue to form fingernails. Nails grow from thin area called the nail matrix; growth of nails is 1-mm per week on average. The lunula is the crescent-shape area at the base of the nail, this is a lighter colour as it mixes with the matrix cells.
The protein keratin stiffens epidermal tissue to form fingernails. Nails grow from thin area called the nail matrix; growth of nails is 1-mm per week on average. The lunula is the crescent-shape area at the base of the nail, this is a lighter colour as it mixes with the matrix cells.
Dermis
The dermis is the middle layer of skin, composed of dense irregular connective tissues such as collagen with elastin arranged in a diffusely bundled and woven pattern. These layers serve to give elasticity to the integument, allowing stretching and conferring flexibility, while also resisting distortions, wrinkling, and sagging[5]. The dermal layer provides a site for the endings of blood vessels and nerves. Manychromatophores are also stored in this layer, as are the bases of integumental structures such as hair, feathers, and glands.
Hypodermis
Although technically not part of the integumentary system, the hypodermis, or subcutaneous tissue, is the layer of tissue directly underneath the dermis. It is composed mainly of connective and adipose tissue. Its physiological functions include insulation, the storage of energy, and aiding in the anchoring of the skin. This is the thickest layer of the integumentary system.