Anatomy: HUMAN SKIN--- --Rizwan

HUMAN SKIN

The Human Skin is outer covering of body. In Human it is largest organ of integumentry system.
DERMETOLOGY study of Skin.
Skin with a total area of about 20 square feet.
Human skin is simillar to that most of mammals, though nearly all Human skin is covered with hair follicles.
Skin has a mesodermal cells, Pigmentation , such as melanin provided by melanocytes, which absorb some of potentially dangerous UV in Sunlight. It also contain DNA repair enzyme that help reverse UV damage such that People lacking these genes for these enzymes suffer high rate of skin cancer.
The skin is largest organ of human body, for average adult human the skin has a surface area of b/w 1.5-2.0 square meter. The thickness of skin varies considerably over all parts of body, Men and Women, Young and Old. An example is the skin of forearm which is n average 1.3mm in male and 1.26 in female.
The average square inch (6.5 cm2) of skin holds sweat glands, 20 blood vessels, 60,000 melanocytes and more than 1000 nerve endings.
SKIN HAS A THREE LAYERS
EPIDERMIS Layer
DERMIS Layer
HYPODERMIS Layer
1. EPIDERMIS layer:- Epidermis layer is outer most layer of skin, provides a water proof barier and create our skin tone.
Epidermis contain no blood vessels (AVASCULAR) and cells in deepest.
the main type of cells which make up epidermis are Markel cells, Keratinocytes, with Melanocytes cells are present.
Epidermis is divided into FIVE sub-layers or strarta.
1: Stratum Corneum
2: Stratum Lucidum
3: Stratum Granulosum
4: Stratum Spinosum
5: Stratum Germinatium (also called stratum basale).

2: DERMIS Layer:- It is a true Skin made of Connective tissue and is a VASCULAR.
It is a thicker inner layer of skin.
matted masses of Connective tissue, Elastic Fibers, Nerve endings, Muscles, Hair follicles, Oil and Sweat glands.
Dermis contain lots of sensory cells (heat, cold, pain, pressure).
3: HYPODERMIS Layer:- Subcutaneous. Attaches integument to muscle.
It is a loose Connective tissue and FAT of body's store.
Absorbs shocks.
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FUNCTIONS OF SKIN
Cover-protects from germs, dehydration, injury.
First line of Defense.
Regulate body temperature.
Manufactures Vitamin D.
Site of many Nerve endings.
Temporary storage of Gulucose, fat, water and salt.
Protect from UV Radiations.
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ONE square cm of skin contains:
3,000,000 cells.
10 Hairs.
1 Yard of blood vessels.
4 Yards of nerves.
700 Sweat glands.
200 nerve endings to record pain.
3000 Sensory cells at the end of nerve fiber.
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DISEASE OF SKIN:
ACENE:- A common and Chronic disrder of sebaceous glands.