Each and every part of our body is composed of tiny microscopic units called the ‘cell’. Cell is the structural and functional unit of the body. Cells have different shapes and sizes according to their nature of work. For example, muscle (cells) fibres are spindle shaped for contraction; glandular cells are cubical in form, specialized for secretion.
Every cell is covered and well protected by a very thin wall called the plasma membrane. A cell is composed of:
- A living stuff called Cytoplasm, a colloid substance that contains many microscopic structures called cell organelles.
- A highly specialized structure in the center of the cell called nucleus, which controls all the cellular activities.
Thus the cell can absorb the nourishment, transport the oxygen, expel the waste material, respond to different situations, grow and reproduce the cell of its own kind, just like an organism.