Structure and Function of Skin

Structure of Skin

Layers of the skin (from superficial to deep) are:
Epidermis – it is made up of stratified squamous epithelium keratinized
Dermis – it is made up of connective tissue.

It consists of following layers (deep to superficial):
Stratum basale or basal layer – It is made up of single layer of columnar cells that rest on a basal lamina. The cells in this layer undergo mitosis to give off keratinocytes.

Stratum spinosum (Malpighian layer) – It consists of several layers of polygonal cells (keratinocytes)

Stratum granulosum – 1-5 layers of flattened cells with deeply stained granules in their cytoplasm.
Stratum lucidum – The layer appears homogenous with indistinct cell boundaries. Flattened nuclei are seen.

Stratum corneum – This layer is acellular and is made up of flattened scale like elements containing keratin filaments. The thickness of this layer depends on the exposure to friction like the layer is thicker on the palm and soles.

The dermis
The dermis is made up of connective tissue. Immediately below the epidermis the connective tissue is dense and constitutes the papillary layer. Deep to this, lies reticular layer of dermis which consists mainly of collagen fibers along with elastic fibers and adipose tissue.

Functions of Skin 

The skin has three main functions: protection, regulation and sensation

Protection: The primary function of the skin is to act as a barrier. The skin provides protection from: mechanical impacts and pressure, variations in temperature, micro-organisms, radiation, chemicals and is water resistant.

Regulation: Skin is also important for regulating several aspects of physiology, including: body temperature via sweat and hair, and changes in peripheral circulation and fluid balance via sweat.

Sensation: Skin provides a sensory interface between the body and the external environment.

It also acts as a reservoir for the synthesis of Vitamin D and helps in absorption of medicine that is administrated through the skin.

Following resources are used while preparing this post (readers are strongly recommended to go through them for more details):

Wheater's Functional Histology: A Text and Color Atlas

Junqueira's Basic Histology: Text and Atlas