Skin

 Enumerate the Functions of Skin.

1. Protection: Protect the body from mechanical injury and pathogens.
2. Thermoregulation : Helps in maintaining normal body temperature .
   • In summers the excess heat is lost from the body by
     1. secretion and evaporation of sweat from sweat glands,
     2. radiation from the dilated blood vessels.
   • In winters heat is conserved due to the presence of the subcutaneous fat and hair.
3. Prevents loss of body fluids.
4. Acts as a sense organ:Is provided with various types of sensory endings for the perception of sensations such as pain, touch, heat & cold.
5. synthesizes Vitamin D.

Enumerate the Layers of  Skin.

•  Outer Epidermis
•  Inner Dermis

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Enumerate the Layers of Epidermis.

Epidermis is made up of keratinized stratified squamous epithelium, therefore like all epithelia, it is avascular.

Layers of epidermis  are:

• Stratum germinativum
• Stratum spinosum
• Stratum granulosum
• Stratum lucidum ( is found only in thick skin of palm and sole)
• Stratum corneum

Describe the layers of Dermis.

The dermis is composed of two layer – papillary layer (superficial layer) and reticular layer (deeper layer).

• Papillary layer- consists of loose connective tissue containing elastic, reticular, collagen fibers and capillaries ( help in nourishing epidermis). It form projections called dermal papillae, which fit into reciprocal  depressions of epidermis.
• Reticular layer – consists of dense  irregular connective tissue containing larger blood vessels,nerve endings, lymphatics, and epidermal appendages, elastic and collagen fibers  that are arranged in layers parallel to the surface.  Direction of the collagen fibers produces clevage/Langer lines. 

Enumerate the Appendages of Skin.

• Hair 
• Nail
• Sweat gland
• Sebaceous gland    

What are the Langer’s Lines?

 Langer’s lines or clevage lines are the lines on the surface of skin which are caused due to the orientation of collagen fibers in the dermis. They run longitudinally in the limbs and circumfrentially in the neck and trunk. Incisions made along or parallel to the Langer’s lines will severe fewer fibers as a result the healing is faster and the scar formation is minimal.

 Define Dermatome.

The area of skin supplied by a single segment of spinal nerve is called dermatome. Knowledge of dermatomes is essential to carry out neurological examination. Touching (using a cotton) skin  in a particular dermatome in conscious patient can be used to localize injury  to a specific spinal nerve or specific spinal segment.

Enumerate the Pigments that Contribute to the Colour of Skin.

 The colour of skin is due to the presence of the:

• Melanin – black brown pigment produced by melanocytes ( all humans have almost same number of melanocytes, but the amount of melanin synthesized is different in different races, which determines the colour  of the skin of individuals.
• Carotene –  yellow – orange pigment  which is taken up from the vegetables  (such as carrot).
• Hemoglobin –  present in blood is responsible for pink colour.

Enumerate the Areas  of skin Devoid of Sebaceous Glands

• Skin of Palm and Sole

 Enumerate the Areas  of Skin with Abundant Sebaceous Glands

• Face
• Scalp
• Ears
• Nostrils

How is the Degree of Burns Assessed in Extensive Burns?

 It is assessed by calculating the percentage of the skin covering the area that is affected. This follows the ‘rule of nine’ and is expressed as follows.

• Head & neck 9%
• Each upper limb 9%
• Front of the trunk 18%
• Back of the trunk 18%
• Each lower limb 18%
• Perineum 1%

How are skin burns classified?

The skin burns are classified as :

•  First degree: Only epidermis is involved and heals in 3-5 days.
• Second degree : Involves epidermis and superficial part of dermis. Heals within few weeks.
• Third degree:  Both epidermis and dermis are burnt.  Requires skin grafting as regeneration is not possible. the hair follicles, sebaceous  and sweat glands are destroyed which  are the sites where regeneration begins.

Applied Aspects