). The intact Skin offers resistance to many harmful agent like bacteria, toxic

Because In such persons, sufficient sun rays could not penetrate the skin to produce vit D from 7 dehydrocholesterol (a precursor of vit D, normaly found In the skin) So they died o fit deficiencies (racket /osteomalacia) and the gene was eliminated By the same argument, one would expect that, in South African countries, white skidded people died of skin cancers and sun bum, leaving only the dark skinned people Skin cancers, it may be noted, are found usually in the white persons who are excessively exposed to sun, the cancer occurring in the exposed parts of the body. (2). The intact Skin offers resistance to many harmful agent like bacteria, toxic chemicals etc If there is an injury of the skin, the barrier fails and infections due to invasion of bacteria from the external world can occur For this protective function, the keratinized stratum corneum plays the fundamental role The skin normaly harbors a bacterial as well as an yeast flora Bacteria present are mostly staphylococci and comytoaclena. Their presence is beneficial as they destroy more pathogenic organisms of the external world water balance The stratum corium is such a membrane that it does not allow water to pass in and out imagine, a subject is bathing in a sea water (NaCI concentration of the sea water is more than isotonic) in absence of the str .corneum, water from the body of the subject would have massively migrated to the sea water. Reverse would have happened during a bath in sweet water or during exposure to heavy rain in Introduction Classification of muscles I. Skeletal Muscle. 1. Functional anatomy. 2. Mechanism of contraction. 3. Fast and slow muscles. 4. Neuromuscular junction and neuromuscular transmission. 5 .Properties of skeletal muscle Introduction. There are three types of muscles in our body skeletal, smooth and cardiac. The skeletal muscles (also called, striated or voluntary muscles) are found in association with the bones (skeletal system), which explains the name Under Light microscope, each muscle cell Is seen lo contain large number of transverse (= cross) lines (- strletions) at regular intervals, hence these muscles are also known as striated (cross striated) muscles These muscles are supplied by somatic nerves and they can be contracted (or relaxed) under will (will = volition), so they are also called voluntary muscles in short, skeletal muscles = striated rustles = voluntary muscles Plain (also called, 'smooth' muscles), on the other hand, are associated with the viscera but not with the bones Thus, these muscles are found in the walls of hollow tubes of gastrointestinal viscera (stomach, small intestine. large intestine), bronchi tubes, urrary bladder, blood vessels (but not In the heart) and so on They are therefore also called visceral muscles' These muscles are supplied by autonomic nerves (sympathetic and parasympathetic) and their contraction/ relaxation are independent of the