Constitution of the Skin
Each person is ‘wrapped up’ in a big skin cover as big as a blanket. This completely encases the body and, as such, is an essential organ with a variety of critical functions. It is the largest human organ, covering an area of approximately 20 square feet and weighing around a sixth of our total body-weight.
The skin is made up of several layers, a bit like an onion, which allows it to carry out its many functions. Each layer comprises a unique cell-structure which has specific tasks to fulfil.
From the exterior to the interior, the skin (also known as the cutis) is made up of the:
- Outer layer (epidermis)
- Dermis (corium)
- Subcutaneous layer (subcutis)
1. The Epidermis
The Epidermis is the outer layer of skin and is composed of five different layers of skin:
- The outermost layer(stratum corneum)
- Clear/translucent layer (stratum lucidum)
- Granular layer (stratum granulosum)
- Spinous layer (stratum spinosum)
- Basal/germinal layer (stratum basale)
The outermost layer, translucent and granular layers consist of dead, keratinized cells. In the granular layer, a keratin-precursor is produced, a substance which is released into the overlying translucent layer in the form of a fatty mass. Dead skin cells are then pushed upwards through this layer towards the skin’s surface, where they are continuously expelled. You could say that human beings ‘shed’ their skin every 27 days.
In contrast, the spinous- and the basal layers of the outer skin consist of living cells. These are basically responsible for pushing the dead cells out to the three outer skin layers from where they are further repelled. New cells are produced in the basal layer in the event of injury to the skin, to aid the gradual closing of wounds.
2. The Dermis
The dermis is elastic and is primarily made up of loosely interwoven connective tissue. In the same way as the outer skin, the dermis also contains several different layers:
- Papillary dermis (dermal pipillae)
- The reticular layer (stratum reticulare)
The papillae of the papillary dermis are connected to the overlying basal layer of the outer skin. The papillary dermis is traversed by fine capillaries which nourish the epidermis and lymphatic vessels also begin here. Receptors for hot, cold and touch are also found here in the papillary dermis in addition to many blood and other cells.
The interstitium is the space between individual cells which is filled by a gel-type fluid known as the ‘intercellular substance’. Cells can move freely within this substance. This is of great importance given that the majority of the cells in the interstitium constitute a part of the immune defense. These cells intervene in the healing of wounds, for example and fight against infection.
A lesser number of free moving cells are found in the reticular layer. It instead contains a thick net of collagen fibres which run parallel to the skin’s surface. The net is made up of elastic connective tissue. This overall construction is what brings about the elasticity of the skin. The orientation of connective tissue and collagen fibres is aligned in a characteristic manner. The dermis also contains hair follicles as well as sweat, scent and sebaceous glands.
3. The Subcutis
The subcutis is made up of loose connective tissue, in which tiny fat pads are stored. The connective tissue is traversed by offshoots of fixed fibres, such as the fibrous bands which anchor the skin to the layer of tissue below. Depending on how well these retaining bands are developed, the skin can either move on its base (e.g. on the back of the hands) or not (e.g. on the soles of feet).
A generic faschia envelops the layers of skin and is made up of very tight collagen fibres. Depending on the area of the body, the fascia covers muscle, bone, cartilage or fat.
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