Scientific Skin Care News 5

“Roopada”

Scientific Beauty News Letter

7.    Epidermis: A layered Structure!

Let us enjoy the study of skin now.  Epidermis is made up of  four major layers of keratinocytes or corniocytes.

1.      Stratum Basale: Stratum Germinativum

2.      Stratum Spinosum

3.      Stratum Granulosum

4.      Stratum Corneum.

Let us understand the epidermis layer by layer.

1.      Stratum Basale: This is the lowermost layer of epidermis which lies directly on top of dermis. The cells in this layer are shaped like columns. The cells in this layer keep dividing and the newly formed cells push the older cells in the outer direction. As the cells move to the outer layers, they slowly become flatter and eventually die. The constant renewal of the epidermis is caused by the Stratum Basale.

Stratum Basale is layer of just 1 row of undifferentiated columnar stem cells that frequently divide.

Half of the newly formed cells are pushed in the upper layer, where they turn towards maturity. The remaining half cells stay in the basale layer and divide over and over again to replenish the epidermis.

All keratinocytes are formed by mitosis (cell division) in the lower region of the malpighian layer. (Malpighian layer is considered to be the combination of the stratum Basale and stratum spinosum). Most of the dividing cells are found in the basal layer, although about one-third of the divisions occur above this level.

 Proliferating cells undergo a cycle: mitosis is followed by an interphase, and then occurs the DNA synthesis, and then another short resting phase occurs before mitosis begins again.

 The complete mitotic cycle takes about 12 to 19 days. The time for the passage of cells through the epidermis, from formation to desquamation, is considered to be one to three months.

In normal skin the production and loss of cells must be finely balanced; otherwise the thickness of the epidermis would fluctuate.

When the epidermis becomes abnormally thick, as in the plaques of psoriasis, this balance is altered. Either the production of cells in the malpighian layer must be abnormally high or their time of passage must be decreased.

When skin is wounded, the healing response is activated and there is a burst of epidermal mitotic activity about 40 hours later.

 Let us think and workout on the other layers of epidermis.

Credit : Rahul Phate’s