Explain how specific membrane-bound organelles of the keratincoytes are used to produce, transport, and modify aquaporin polypeptides from mRNA.

 

Keratinocytes are a cell of the epidermis that produces keratin, is formed in the basal epidermal layer above the dermis, divides to more keratinocytes, and ultimately migrates into the outer protective layer of the skin and undergoes final differentiation into a coenocyte. Specific membrane-bound organelles pose some of the features to enable them to do their functions as discussed below.

Step-by-step explanation

Epidermis.

It is composed of keratinized, stratified squamous epithelium and is made up of 4 layers of epithelial cells depending on its location in the body. From deeper to superficial these layers are stratum Basale, stratum spinosum, stratum granulosum, and stratum corneum. The cells in all the layers except for stratum besele are called keratinocytes which is a cell that manufactures and stores the protein keratin.

Stratum Basale.

It is a cuboid-shaped stem cell that is a precursor of the keratinocytes of the epidermis. Two other cell types found in this basal cell are Merkel cells which function as a receptor and are responsible for stimulating sensory nerves that the brain perceives as touch. The second is melanocyte that produces melanin pigment which gives the skin its color.

Stratum spinosum.

It is spiny in appearance due to the protruding cell processes that join the cells via a structure called desmosome. The desmosome cell interlock with each other to strengthen the bond between the cell. Keratinocytes in the stratum spinosum stats synthesizing keratin and release water-repelling glycolipid that helps to prevent water losses from the body.

Stratum granulosum.

They are grainy in appearance due to further change in keratinocytes as they are pushes from the stratum spinosum. The cells become flat as their membrane thickens to allow the production of protein keratin which accolades as lamellar granules within the cells.

Stratum Lucidum.

It is a smooth and translucent layer of the epidermis situated above the stratum granulosum. Keratinocytes containing these cells are dead and flat. Stratum lucidum cells are packs with eleiden derived from keratohyalin which give these cells their transparency and provide a barrier to water.

Stratum corneum.

This is the most superficial layer in the epidermis and it prevents penetration of microbes and dehydration of underlying tissues.

Dermis.-This is the inner layer of the skin and has the following functions.

Reticular layer

Just below the papillary layer, we have a much thicker layer called the reticular layer composing of dense connective tissue. It contains elastin fibers providing elasticity to the skin enabling movement.

Hypodermis

This is the layer below the dermis with a function to connect the skin to the fibrous tissues of the bones and muscles. It also consists of well-vascularized, loose, and adipose tissue which functions as a mode of fat storage and provides insulations and cushioning for the integuments.