FUNCTIONS OF THE HUMAN BODY

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FUNCTIONS OF THE HUMAN BODY

We have gone through the anatomy of the body in the previous chapter, and now in this chapter we will briefly refer to its Physiology—that is to say its normal functioning in health.

The final unit of any part of the human body is a cell. This is so minute a structure as to be visible to the naked eye: it has a wall, a permeating fluid mass called protoplasm in the midst of which lies nucleus, a sort of directing-body, governing the activities of the cell. A cell lives so long as it receives a certain amount of food, water (moisture), warmth and oxygen. Heating, drying, deprival of food and of oxygen kill the cell. Cold may not kill but temporarily suspend its activity. A cell of the human body is more or less fixed to the part where it grows; in time it grows old and decays; or it buds into two new cells. Cell reproduction happens in three ways firstly, by fission, i.e., a bud appears on the old cell; this bud enlarges and suddenly drops off from the old parent cell, thus giving rise to two cells—one of the dropped bud and, the other the parent-cell rejuvenated; secondly, by simple division—i.e., a cell divides in twain, each of the two rejuvenating; and thirdly by karyokinesis or mitosis—i.e., the nucleus undergoes division and rearrangement of its structure, the two halved nucleus run to the poles of the cell and thence effect the division of the cell into two. The food and oxygen that cells receive are brought to them by the circulating blood. The cells pick up nourishment and oxygen from the presenting blood and give up in blood CO2 and the waste products of their body- activity, called metabolic products. So much about cells in the abstract.

Cells undergo modification according to the needs of a part and their modifications sometimes make it difficult to recognise them. Thus, in the nail, they form compressed homy masses; in the wind-pipe, they have hairy projections (cilia); in the muscle, they are spindle-shaped and long; in the testicle, they get tails; in the stomach, they look like white goblets and so on. In fact, in the body, groups of cells aggregate together to form tissues, with special purpose to serve. We thus get bony tissue, nerve tissue, muscle tissue and so on. Tissues make up the constituents of systems.

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