SKIN:
·
.
Largest organ in the body
·
.
Weight=4.5kg, total area 20sq feat
·
.
Integumentary system is formed by skin and its derivatives skin
·
Accounting
for about 15% of total adult body weight
FUNCTIONS:
·
Protection
of the human body against external physical, chemical and biologic assailant
·
Immunity:
as the skin plays first line of defense in human body
·
Thermoregulation
·
Sensation:
transmitting information to the CNS about surrounding
·
Excretion
of certain type of waste material from the body
·
Serves
as an endocrine function for example synthesis of vit D
Layers of Skin:
Skin is composed of two layers and a closely associated
layer
·
Epidermis
·
Dermis
·
Subcutaneous tissue
EPIDERMIS:
·
.
Form a protective water proof barrier
·
.
Keratinized stratified squamous epithelium layer
·
.
Avascular
·
.
On the palms of the hand and soles of the feet the epidermis is extremely thick
(1.5mm) to withstand with tear and fear
·
.
Eyelid has thinnest layer of epidermis (less than 0.1 mm)
·
.
Mainly composed of two types of cells Keratinocyles and dendritic cells
·
.
Skin that has four layers of cells
is refered to as thin skin
·
.
From deep to superficial these are striatum
basale, stratum spinosum, stratum granulosum and stratum corneum
·
.
Thick skin has a fifth layer called
stratum lucidum located between stratum
corneum and granulosum
·
For
remembering of these layers this
mnemonic is helpful (Boys say girls look cute , B= stratum basale , S=
stratum spinosum , G= Stratum granulosum , L= Stratum lucidum , C=Stratum
corneum )
·
.
Keratinocytes are found in all
layers except striatum basale
·
.
Keratinocytes is a cell that produces and stores keratin protein (keratin is an
intracellular fibrous protein that give hair, nails and skin their hardness and
water resistant properties)
·
.
Keratinocytes are dead in stratum corneum
Cont…..
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