Question

Describe the various layers of skin epidermis.

Answer 1

Epidermis: 

• It originates from the embryonic ectoderm. 
• It is thickest in the body regions subjected to wear and tear such as soles and palm. 
• It is very thin in eyelids and cornea. 
• The epidermis is without nerves and blood vessels. 
• It is a stratified epithelium and consists of five types of layers. 
• They are as follows from inside to outside. 

Stratum Malpighi or stratum germinativum: 

• It is the innermost layer of the epidermis which is living. 
• It is made up of one layer of columnar cells. 
• These cells divide constantly to form upper layers of the epidermis. 
• This layer pushes into the dermis. 
• These pushing are called as rete pegs. 
• ]This layer also contains some melanocytes. 
• These cells contain melanin pigments which impart colour to the skin. 

Stratum spinosum: 

• This layer is situated outside the stratum Malpighi. 
• It consists of many layers of branched polyhedral cells. 
• These cells bear a hook-like structure. 
• This layer provides strength to the skin. 

Stratum granules: 

• It is situated outside the stratum spinosum. 
• It includes 5 – 6 layers of cells having granules of keratohyalin protein. Stratum lucidum: 
• It is situated outside the stratum granulosum. It consists of 3 – 4 layers of living and flat cells. 
• These cells contain a protein called Elieidin which is formed by keratohyalin. 
• The cells of this layer are enucleated and translucent. 
• It is waterproof and also called a barrier layer. 

Stratum corneum: 

• It is the outermost layer which is made up of flat squamous cells. 
• These cells are dead because of the presence of dead Keratin protein. 
• It is the thickest layer of the epidermis and consists of 8 – 10 layers of cells. 
• It’s outermost layers sloughed off constantly. 

Keratinization: 

• The process of formation of Keratin protein in the epidermis is called Keratinization. 
• This process leads in the formation of hair, nails etc.