Nucleus - The Cell: The Histology Guide - University Of Leeds

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What is the nucleus?

The nucleus is found in the middle of the cells, and it contains DNA arranged in chromosomes. It is surrounded by the nuclear envelope, a double nuclear membrane (outer and inner), which separates the nucleus from the cytoplasm. The outer membrane is continuous with the rough endoplasmic reticulum. The nuclear envelope contains pores which control the movement of substances in and out of the nucleus. RNA is selectively transported into the cytoplasm, and proteins are selectively transported into the nucleus. The nuclear membrane is supported by a meshwork of intermediate filaments, called nuclear lamins.

One or more darkly staining spherical bodies called the nucleoli are found inside the nucleus. These are the sites at which ribosomes are assembled. Nucleoli are most prominent in cells that are synthesising large amounts of protein.

Most cells have a single nucleus, though some have none (ie. red blood cells), and some have several (i.e. skeletal muscle).

This image below shows a diagram of the nucleus.

Nuclei look different cell types, and when cells divide. For example, in different types of white blood cells, in interphase, the nucleus can have one, or more lobes, and the number of lobes is characteristic of the type of white blood cell.

diagram of the nucleus

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