Page 14 - LECTURE NOTES

Melanocytes -they are the melanin (pigment) producing cell of the epidermis. Melanin

prevents the skin from. The number of melanocytes in the epidermis is the same,
regardless of the person’s race or skin color; it is the number , shape and size of

melanosomes (melanin containing granules) and the type of melanin that determine
difference in skin color.

Langerhans' cells - these are cells with dendrite processes specialized in antigen

processing and presentation (building immunity to infection). They are found in the

epidermis but they constantly move as a result, they transport antigens to the regional
lymph nodes and present them to naïve T lymphocytes in the regional lymph nodes

and consequently the naive T lymphocytes become recruited to the specific antigen

and the resultant immunologic response occurs. ("They take the offenders to the
police station for investigation and appropriate response "). E.g. when a child receives

BCG vaccination and develops a scar. In this way, the skin is very crucial part of the
immune system because of the large surface area that it spans. Countless varieties of

external antigens can be sensed by the immune system via the Langerhans' cells in
the epidermis.

2.5 Physiological Functions of the Skin

1. Display: the skin as a display enables us to assume our own identity and to

recognize among our selves and with out the skin emotional expressions wouldn't
be possible.

2. Protection: it protects the body from many environmentally unfavorable factors;

such as, thermal, chemical, ultra violet radiation and different disease-causing
microorganisms. It also protects from unnecessary entry and egress of fluids into

and from the body.
3. Thermoregulation: because it bears receptors to detect temperature, it conveys

sensory input to the CNS so that the thermoregulatory centre can respond
appropriately. The skin is a peripheral thermoregulatory organ through sweating,

vasodilation, and shivering.

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