Skin

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

3. Skin structure

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
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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
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8. Hypodermis
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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.