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Medulla - Cortex


Medulla

Medulla may not be imaged with normal beam microscopy as it is not continuous and sometimes as it is not present in human hair. When it could be seen in the beam microscopy, it is seen amorphous due to partial keratinization.
Medullar cells are differentiated from matrix cells at the top of dermal papilla. Irregular granules developing from golgi apparatus come together and expand.

Although these granules have similarities with inner root sheaths, these bodies may be differentiated from epidermal kerato-hyaline with the use of cytological and histological chemical methods. They become keratinized by different biochemical processes used in cells of cortex and cuticles forming keratin. Roles of medullar granules in humans are unknown. In vellus and lanuga hair medulla do not develop and medullar cells are seldom seen in terminal hair and sometimes they may not be present. 

 

Cortex

It consists of cells, which have lost their nucleuses during the stage of upward growth of hair matrix and keratinized by filling with keratin fibrils. Keratinization occurs before kerato-hyaline granules form just as it happens in keratinized epidermis. Therefore, keratin of inner root sheath, which contains soft keratin similar to epidermis, is a rigid keratin.