Skin outer protective layer of skin. It is
Skin is the largest organ of the human body and it accounts for 15% of your body weight even though it is only a few millimetres thick.
The thinnest part of your skin is found on your eyelids measuring at 0.02mm thick and the thickest on your feet measuring at 1.4mm. Your skin is a protective layer of tissues which is called the integumentary system. Skin is made up of multiple layers of cells and tissues, which are held to underlying structures by connective tissue. There are three layers main layers to your skin the epidermis, dermis and hypodermis which all have interlinking layers of cells that combine together to create your skin.The Epidermis – is the outer protective layer of skin.
It is made up of four or five layers of packed together epithelial cells, depending on the location of the body. The only areas of the body that have a fifth layer of skin are the palms of your hands and the soles of your feet, they have an extra layer called the stratum lucidum, which is located between the stratum granulosum and the most superficial layer of the epidermis known as the stratum corneum. Everywhere else in the body the epidermis only has four layers which are the stratum basale (which is the deepest layer of the epidermis and is closest to the dermis the next layer of skin), then the stratum spinosum, and the already mentioned stratum granulosum and stratum corneum (the most superficial layer where dead skin cells reside). All the layers of skin apart from the stratum basale have cells which are called keratinocytes. A keratinocyte is a cell that manufactures and stores the protein keratin.
Keratin is an intracellular fibrous protein that gives hair, nails, and skin their hardness and water-resistant properties. The keratinocytes in the stratum corneum are dead and regularly slough away, being replaced by cells from the deeper layers which renew every 28 days. The stratum basale produces the keratinocytes as well as two other cells.
The first is a Merkel cell, which functions as a receptor and is responsible for stimulating sensory nerves that the brain perceives as touch. These cells are especially abundant on the surfaces of the hands and feet. The second is a melanocyte, a cell that produces the pigment melanin. Melanin gives hair and skin its colour, and also helps protect the living cells of the epidermis from ultraviolet (UV) radiation damage. The cells in the stratum basale bond to the dermis via intertwining collagen fibres, referred to as the basement membrane.
The Dermis- is the middle layer of skin, residing between the epidermis and the hypodermis. It is a fibrous network of tissue that provides structure and resilience to the skin. It is made up of dense and irregular connective tissue that houses blood and lymph vessels, nerves, and other structures, such as hair follicles and sweat glands. The dermis is made of two layers of connective tissue (papillary layer and the reticular layer) that compose an interconnected mesh of elastin and collagenous fibres, produced by fibroblasts (which play a critical role in wound healing).The Hypodermis (also called the subcutaneous layer or superficial fascia) is a layer directly below the dermis and serves to connect the skin to the underlying fascia (fibrous tissue) of the bones and muscles.
It is not strictly a part of the skin, although the border between the hypodermis and dermis can be difficult to distinguish. The hypodermis consists of well-vascularized, loose, areolar connective tissue and adipose tissue, which functions as a mode of fat storage and provides insulation and cushioning for the integument. The hypodermis is home to most of the fat that concerns people when they are trying to keep their weight under control. Adipose tissue present in the hypodermis consists of fat-storing cells called adipocytes.
This stored fat can serve as an energy reserve, insulate the body to prevent heat loss, and act as a cushion to protect underlying structures from trauma.