Trypanosomiasis refers to a group of diseases caused by Trypanosoma There are two types of trypanosomiasis that affect humans, they are divided according to their geographical location: African trypanosomiasis, or sleeping sickness, is caused by Trypanosoma brucei parasites in sub-Saharan Africa and is transmitted by the tsetse fly? (Glossina).
Specilized cells in the epidermis called melanocytes produce melanin, a dark pigment that provides skin color. Melanin absorbs ultraviolet radiation in sunlight and preventing mutations in the DNA of skin cells and other damaging effects.ifferences in skin color result from differences in the amount of melanin that melanocytes produce and the distribution and size of pigment granules. Skin color is genetically determined.
The skin has two layers: the upper layer is the epidermis, and the lower layer is the dermis. Below the dermis is the hypodermis, or subcutaneous layer, composed of fat or other connective tissue . The epidermis itself is an epithelium made up of sublayers. The outermost portion consists of many layers of flat, dead, dry epithelial cells called keratinocytes. Clearly this barrier of dead cells needs no blood supply. The waxy surface coating of these cells allows the skin to be waterproof and dry. In effect, the body surrounds itself with a hostile desert where few germs can live. Living keratinocytes in the deepest layer of the epidermis undergo rapid cell division and push the overlying cells toward the surface. Melanocytes are also deep and produce the dark pigment in the skin, melanin. Upon exposure to ultraviolet light, melanin production is increased, a process called tanning.