What is skin?
Firstly, we should know that the skin is the soft outer covering of vertebrates. It is the largest organ in human body and hence, its total area is of 20 square feet and weighs around 16% of your body weight. However, the thickness of human skin may vary from person-to-person. In short, the skin Anatomy comprises of many different elements in 1 square inch including:
- 5 million cells
- 650 sweat glands
- 95 to 100 oil glands
- 65 hair follicles
- 19 yards of blood vessels
- 78 yards of nerves
- 19500 sensory cells at the end of nerve fibre
- 1300 nerve endings to record pain
- The skin covers the body surface and hence, protects the deeper parts
- Similarly, the purpose of this outer covering for the body is to protect against injury, infection, heat, cold and store water, fat and vitamins.
- An average adult weighs 8-10 pounds.
- An average area of about 22 square feet..
- It is an important part of the excretory & nervous system.
- Its thickness varies from less than 1 mm on the eyelid to 4 mm on palm.
- Every 28 days, new skin comes on the top.
Layers of Skin/ Study of Skin:
In the anatomy of skin, the skin has basically 3 layers
The epidermis plays a major role in skin anatomy. It is the outermost layer of skin, hence, provides a waterproof barrier and creates our skin tone.In addition, it constantly shreds dead skin cells and replace them with new and healthy which grows in lower layers.
Epidermis has 4 types of cells:
- Keratinocytes– produces keratin-protein-gives toughness, act as a cement substance between cells
- Melanocytes- produces skin pigment called as melanin.
- Langerhans cells- immune cells involved in contact sensitization.
- Merkel cells- sensory receptors for tough, pain & temperature.
Epidermis has 4 layers of cells:
- Corneal layer- it is made up of cells filled with keratin.
- Granular layer- it is made up of granular cells.
- Spinous layer- it is made up of spinous cells.
- Basal layer- it is made up of basal cells.
Dermis is beneath the epidermis, contains tough connective tissue, hair follicles, and sweat glands. In addition, it contains ground substances, collagen & elastic fibres (connective tissue). Embedded in the connective tissue are blood vessels, lymph vessels, nerves, muscles, sebaceous gland, sweat glands and hair follicles.
- Nerve endings- for sensation of touch, pain & temperature.
- Blood vessels- for supply of food & oxygen to skin.
- Lymphatic vessels- to drain the lymph from the skin.
- Sweat glands- excrete sweat from the skin and moreover it maintains the body temperature.
- Sebaceous glands- The main function is to maintain the oiliness of the skin, prevents evaporation of water, oil produced by sebaceous gland is known as sebum.
3. Subcutaneous tissue (Hypodermis) –
Hypodermis is made of fat and connective tissue. Lies below the dermis. Its purpose is to attach the skin to underlying bone and muscle as well as supplying it with blood vessels and nerves. Subcutis also provides insulation for your body, keeping you warm and it also acts as a shock absorber for your vital organs.
Functions of skin:
- Protection- Protects body from harmful germs, ultraviolet rays, etc.
- Sensation- It is organ of touch and other senses. Skin contains sensory nerve endings, which detects stimuli of heat, cold, pressure, etc.
- Heat Regulation- Regulates the body temperature.
- Homeostasis- Prevents water loss from the body.
- Excretion- Excretes the waste products.
- Vitamin D- Produces vitamin D through the action of ultraviolet rays.
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