Describe the structural adaptations of the skin to its function.

❤ The main functions of the skin are protection, regulation of body temperature and synthesis of vitamin D.

❤ It also functions as sensory organ. 

❤It consists of 3 layers known as epidermis, dermis and hypodermis. 

❤ The epidermis is of stratified squamous keratinized type of epithelia. 

❤ It consists of 5 layers. They are, 

❤ Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum from deep to the most superficial.

❤The stratum basale is the deepest layer. It consists of a single layer of columnar or cuboidal cells.

❤ Keratinocyte stem cells are scattered among other cells. The cells are attached to the basement membrane by hemidesmosomes while they are attached to eachother by desmosomes.

❤This firm attachment to membrane and to eachother provides protection. 

❤ Melanocytes and Merkel cells are also present. 

❤ Melanocytes produce pigment melanin that determines the skin colour. 

❤ Merkel cells aid the skin to act as a sensory organ by functioning as sensory mechanoreceptors.

❤The stratum spinosum consist of several layers of polygonal cells which are mitotically active. They contain concentrated tonofilaments.

❤Langerhan cells are scattered among the polygonal cells. 

❤ They are antigen recognizing and processing cells and help to protect the body against antigens. Processes of melanocytes project into the layers of this stratum.

❤The polygonal cells are attached to each other by desmosomes and this firm attachment protects the skin against abrasions.

❤The stratum granulosum consists of 3-5 layers of flattened polygonal cells which contain keratohyalingranules. The cells are not mitotically active.

❤The stratum lucidum is a translucent thin layer of extremely flattened eosinophilic cells. 

❤They do not contain nuclei or any organelles. 

❤Filaments and desmosomes are retained. 

❤ Cells contain eleidin. 

❤Stratum corneum is the outermost layer and is composed of 15-20 layers of cells. 

❤The cells are flattened, non-nucleated and keratinized. 

❤The cells are filled with keratin filaments. 

❤ Keratinization aids in providing protection against abrasions. 

❤The dermis is formed from dense irregular connective tissue.  Interdigitations of the dermis and the epidermis are called dermal papillae. 

❤ They are important in opposing shearing forces between the two layers thus ensuring protection. There are two layers in the dermis as the papillary layer and the reticular layer.

❤ The papillary layer consist of loose connective tissue, loops of small blood vessels, capillaries and nerve endings.

❤The reticular layer consists of dense irregular connective tissue, blood vessels that form av shunts, nerves and lymphatics.

❤ The blood vessels aid in temperature regulation. 

❤ While the nerve endings acting as a sensory organ. 

❤Meissner’s corpuscles, which are confined to dermal papillae act as touch receptors further enabling the skin to act as sensory organ.

❤Pacinian corpuscles, which are found in deep dermis or hypodermis act as pressure receptors. It also enhances the ability of skin to act as a sensory organ. 

❤ Sweat glands are also present in the dermis and aid in temperature regulation.