Answer:
In general, it is possible to affirm that in areas where there is malnutrition there are high deficits in all the essential vitamins for humans. A characteristic poor diet in these countries occasionally lacks vitamins and with this malnutrition. However, the reports mainly focus on deficits of vitamin A and D because there are more investigations. Vitamins are essential substances for the body and its function and cannot be synthesized by the same body but must be ingested from food. Vitamin deficiency is considered serious because it causes blindness and even death.
Answer:
Schwann cells or neurilemma cells are the cells which form the myelin sheath around neuronal axons in the peripheral nervous system (PNS) only.
Neurilemma is the collective term used for cytoplasm and nuclei present around the myelin sheath which helps in the regeneration process of nerves.
A Schwann cell surrounds the axon, invaginate it and the plasmalemma of the Schwann cells joins and from a double membrane structure called mesaxon. This mesaxon starts wrapping the axon in spiral fashion and cytoplasm start condensing into the compact myelin sheath.
Wind water and ice roads and shape the land. Volcanic activity and earthquakes alter the landscape in a dramatic and often violent manner. And on a much longer time scale, the movement of earths plates slowly reconfigures oceans and continents. Each one of these processes plays a role in the Arctic and Antarctica.
