External respiration is the process of taking oxygen into and expelling carbon dioxide from the body. External respiration is essential for life as it supplies oxygen to extract energy from food via internal or cellular respiration. Additionally, it removes carbon dioxide, which is a waste product of respiration.
The nucleus is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction.It is commonly the most prominent organelle in the cell. The nucleus is surrounded by a structure called the nuclear envelope.This membrane separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed within the nucleus.he nucleus is surrounded by a structure called the nuclear envelope. This membrane separates the contents of the nucleus from the cytoplasm. The cell's chromosomes are also housed within the nucleus.
In other fields, such as: In Physics, a nucleus refers to the positively-charged center of an atom that usually contains the protons and neutrons. In Chemistry, a nucleus is a fundamental arrangement of atoms that occur in compounds through substitution of atoms without a change in structure.n Botany, a nucleus is the central kernel of a nut or seed, or the center of a starch granule. In Anatomy, a nucleus is a group of specialized nerve cells in the brain or spinal cord. Word origin: L: kernel, syncopated var. of nuculeus, equiv. to nucu(la) little nut (nuc-, s. of nux nut + -ula-ULE) + -leus n. suffix.