The nucleus exerts a direct influence on different activities of the cell and plays a great role in transmitting hereditary characters from the parents to offspring. Apart from these, one or two small spherical bodies are found in the nucleoplasm, known as nucleolus. The threads are easily stainable by basic dyes they are made up of a substance, called chromatin. Some delicate thread-like structures that suspend in the nucleoplasm are called nuclear reticulum or chromatin network. The nuclear cavity remains filled up with a dense jelly-like substance, known as nucleoplasm. A membrane, known as nuclear membrane surrounds it to keep the core protected. The nucleus is denser than the cytoplasm and it is regarded as the dynamic centre of life. The centriole is the minute granule present in many resting cells, just outside the nuclear membrane. The centrosome is the region of differentiated cytoplasm containing centriole. The vacuole is important as the fluid-filled space within the cytoplasm of a cell, which controls the cell sap isotonic with cytoplasm by expelling or entering the water from the environment, following the process of osmosis. Its functions are not clearly known, but seem to be associated with the formation of secretions. The Golgi body is the local clump of material present in the cytoplasm.
Although the main constituents of mitochondria are protein and fat, it also contains several enzymes, notably oxidative enzyme systems. The mitochondria are the minute, semi-solid body enclosed in a membrane with a complex internal structure. Of the living bodies the mitochondria and the Golgi body are very important.