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Skin
1.
2. The skin
Skin – our largest organ
Accounts for 7% of body weight
The skin varies in thickness from 1.5 to 4mm distinct region
The superficial region is a thick epithelial tissue
Divided into two distinct layers
Epidermis
Dermis
4. Epidermi
s
Composed of cellular components only.
It is formed of keratinocytes & dendritic cells.
Dendritic cells include melanocytes, Langerhans cells & indeterminate
dendritic cells.
Layers of Epidermis
A. Stratum Germinativum
B. Stratum spinosum
C. Stratum granulosum
D. Stratum lucidum
E. Stratum corneum
5. Layer of the
Epidermis
Stratum basale
Deepest layer of epidermis.
Attached to underlying dermis.
Also called the Stratum germinativum.
Stratum spinosum (spiny layer)
Contains thick bundles of intermediate filaments
Contains star-shaped cells are part of the immune
system
6. Stratum granulosum
Consists of one to five layers of flattened keratinocytes and intermediate filaments
Intermediate filaments contain Keratohyaline granules – help form keratin
Lamellated granules – contain a waterproofing glycolipid
Stratum lucidum (clear layer)
Occurs only in thick skin but not in thin skin
Consists of a few rows of flat, dead keratinocytes
It is also named the transition zone
Stratum corneum (horny layer)
Thick layer of dead keratinocytes andthickened plasma membranes
Protects skin against abrasion andpenetration
7. Dermi
s
Second major layer of the skin
Composed of Strong, flexible connective tissue
Richly supplied with blood vessels and nerves fibers
It is arranged into two region:
1. Upper papillary dermis: 20% of thickness of the dermis
2. Deeper reticular dermis: 80% of thickness of the dermis
8. Hypodermis
Deep to the skin – also called superficial fascia
Composed of areolar and adipose connective tissues
It serve as a reserve energy supply.
It act as an insulator because fat is a poor conductor of heat, it
helps prevent heat loss from the body
9. Skin
color
Three pigments contribute to skin color
Melanin – most important pigment – made from tyrosine
Carotene – yellowish pigment from carrots and tomatoes
Hemoglobin
10. Functions of Skin
Protect the body from mechanical injuries, effect of chemicals & heat also.
Prevent the entry of MOS into the body.
Act as a excretory organ – sweat
Maintain body temperature
Outer layer of skin contain cholesterol which form vitamin D.