Skin is the organ that gives colour to our body. Moreover, skin reflects our emotions. Although you cannot typically think, that skin is the organ, however, it is the true that skin is composed of tissues that work together and perform different functions. Do you know an interesting fact about skin? Skin is the largest organ of our body and it covers 20 square feet area of the body. A square inch of skin consists of more than 1000 nerve endings, 20 blood vessels, 650 sweat glands as well as makes up one-seventh of our body’s weight. Skin serves as a protective barrier, regulates body temperature and senses touch, heat and cold. Now here comes a question, how can skin perform so many functions in our body? Skin performs different functions because of its structure. First and foremost, let’s know the structure of skin in detail.
Overall structure of skin makes the integumentary system and provides a shield for our body, that protects us from harmful external substances and microorganisms.
Skin is made up of two layers:
Structure Of Skin – The Epidermis
The epidermis is the outermost layer of skin and is made up of keratinized, stratified squamous epithelium. Moreover, the cells of this layer are called keratinocytes. Keratinocytes synthesize keratin and are made up of protein keratin. Keratin provides strength and makes it water-resistant. Thus, keratinocytes act as a barrier against heat and pathogens. Epidermis is not supplied by blood vessels and therefore, it derives nourishment from the interstitial fluid of dermis. On different body parts it varies in thickness. It is thick on palm and soles and thin between fingers and toes.
Epidermis is made up of four layers from deep to superficial these layers are Stratum basale, Stratum spinosum, Stratum granulosum, Stratum lucidum, Stratum corneum.
It is the deepest layer of epidermis which connects epidermis to the dermis and is composed of single layer of cells called basal cells. Basal cells constantly give rise to new cells. As a result of formation of new cells, existing cells are pushed upwards. Within basal cells Merck cells and melanocytes are present. Merck cells are abundant on surfaces of hands and feet which serves as a receptor. Melanocytes synthesize pigment melanin. Melanin gives colour to our skin as well as protect us from ultraviolet rays of sun. However, this layer is also called stratum germinativum.
Stratum spinosum is formed due to cell division in stratum basale. It is made up of eight to ten layers of keratinocytes. Dendritic cells also called Langerhans cells are present between keratinocytes. Langerhan cells engulf pathogens as well as damaged cells. As new keratinocytes are produced from stratum basale, therefore, the older cells are pushed upwards. Thus, these cells become flattened and keratinized.
Stratum granulosum has granular appearance and consists of three to five layers. Cells of this layer have thick cell membrane as well as synthesize keratin and keratohyalin. As the cells die, nuclei and other cell organelles disintegrate leaving behind keratin, keratohyalin and cell membrane.
Stratum lucidum is a smooth, semitransparent, shiny and non-stainable layer. Keratinocytes of this layer are dead and flattened and consists of refractile granules Eledin. This Eledin gives transparency and glossy appearance to layer. This layer is present only in thick skin of palms and soles.
Stratum corneum is superficial and thin layer of epidermis. It consists of closely packed, flattened, cornified dead cells. The cytoplasm and nuclei of cells are replaced by keratin. The superficial cells are sloughed off periodically. Each day around 500 million skin cells are sloughed off. While new cells are pushed up from the stratum basale. Stratum corneum prevents body from microbial infection and mechanical injury.
Structure Of Skin – Dermis
Dermis is present below the epidermis and is composed of tough, elastic, fibrous connective tissue. It is supplied by blood vessels, lymphatic vessels and nerves.
Dermis consists of two layers
- Papillary layer
- Reticular layer
Papillary layer is the outer layer of dermis. It consists of various conical eminences called papillae. These papillae projects into the stratum basale and increase the surface area for distribution of nerve endings and blood vessels. These are numerous in tips of fingers & toes. This layer consists of phagocytes and touch receptors called Meissner corpuscles.
Reticular layer lies beneath the papillary layer. It consists of dense, irregular connective tissue. Its appearance is net-like because of tight meshwork of elastin and collagen fibres. Elastin fibre, give elasticity and collagen fibres give tensile strength. This layer contains sebaceous glands, sweat glands, corpuscles of Ruffini and Pacini, hair follicles and arrectores pilorum muscle associated with the hair follicle.
Human skin has two types of glands, sweat gland and sebaceous gland. Sweat glands and sebaceous glands are called epidermal derivatives.
Sweat glands are slender, coiled tubes embedded in dermis. Its long ducts opens on skin surface. These glands produce sweat and regulates body temperature and helps in osmoregulation. Ciliary glands in eyelids are modified form of sweat glands.
Sebaceous glands are branched alveolar glands opening in hair follicles. They secrete sebum that keeps skin soft, water proof, greasy and glistering. These are abundant in the skin of scalp, face, nostrils, mouth and ears. Cells of sebaceous glands synthesize vitamin D. The oily secretion sebum protect against invasion of microbes.
Layer present below the dermis is called hypodermis. It is not the part of skin but it is difficult to distinguish the border between the hypodermis and dermis. Hypodermis is well vascularized, loose, areolar connective and adipose tissue. It provides insulation against heat and cold.
Functions of Skin
- Conversion – in the presence of sunlight it converts precursor of vitamin D to active vitamin D
- Regulation – through sweating it regulates body temperature and salt concentration
- Absorption – absorbs lipid soluble substances present in cosmetics and therapeutic products.
- Protection – protects against microbes and mechanical injury.
- Excretion – excretes water and salts
- Sensation – senses touch, pain, pressure and temperature.
We can remember this by word CRAPES in which C is for conversion, R is for regulation, A is for absorption, P is for protection, E is for excretion and S is for sensation.
Though skin protects us from various infections but it is also sensitive to some diseases such as eczema, acne, rosacea, abscess, scabies, lichen planus, melanoma and many more.
Some skin problems are caused due to pathogens like bacteria, fungi and viruses. While some are caused due to deficiencies of vitamins and minerals. But major skin problems are caused due to our daily lifestyle activities in which, stress plays an important role. To keep our skin healthy we must include some routines in our daily life. So here are some tips to maintain healthy skin.
😊 How To Keep Skin Healthy 😊
As age increases skin becomes thinner and the process of healing slows down. Elasticity of skin is reduced due to which wrinkles appear on skin surface. However, to slow down the process of ageing one should include antioxidants in diet. In conclusion, skin is very important organ or body part, keep it full nourished as well as prevent it from diseases.
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