I am a Licensed Practical Nurse with five years' experience in this profession. I believe it is essential to go back to the basics in all things in order to really understand them. I am fascinated by how our bodies work and I hope I can get my readers to share my fascination. I hope we all learn new things and marvel again at the things we already know. This feature -- which includes a closing section on how disease affects the topic in question -- will run on The Cancer Blog on Wednesdays, and The Cardio Blog and The Diabetes Blog on Thursdays. [The contents in this post are for informational purposes only and should not be construed as medical advice or substitute for professional medical care.]

We start with the cell, because so much of what happens to us when we get sick, and how we get healthy again, can be explained by what happens on a cellular level. The cell is extremely complex and I will only touch on the basics in these posts, but at least we can have a rudimentary understanding.

We have discussed cell membranes (May 24), as well as cell organelles (May 31). On , June 7,we discussed the cellular transport mechanisms. Today we will look briefly at the cell nucleus. As with the other parts of the cell, this can be a short discussion or a series of articles in and of themselves. I have decided to stay very basic and not discuss each component separately.

With the exception of mature red blood cells, human cells have a nucleus and some, like skeletal muscle cells, have more than one. The nucleus is composed of three main parts, the nuclear envelope, the nucleolus and the chromatin.

The nucleus is separated from the cytoplasm by a double membrane (nuclear envelope) that have lipid bilayers like the plasma membrane. The outer membrane of the nuclear envelope is continuous with the rough endoplasmic reticulum (ER). It controls the movement of substances between the nucleus and the cytoplasm through nuclear pores -- channels that perforate the nuclear envelope. Small molecules can diffuse through the nuclear pores, but larger molecules, like ribonucleic acid (RNA), need to use active transport facilitated by carrier proteins. The other structural element of the nucleus is the cellular lamina, a mesh-work that adds support, much like the cytoskeleton supports the cell as a whole.

Within the nucleus is a dense body called the nucleolus that is not surrounded by a membrane. It contains ribosomes, RNA, DNA (deoxyribonucleic acid) and proteins. One of its main roles is to form a type of RNA called ribosomal RNA. This is used to construct the subunits of organelles called ribosomes, which play a key role in protein synthesis.

The chromatin contains DNA and proteins formed into packets of code called chromosomes. Each human cell has 46 chromosomes, 23 inherited from each parent. Functional units of the chromosomes are referred to as genes. DNA is the genetic code for the characteristics and activities of the cell. Only a small number of genes are actually active in a particular cell. These active genes are the codes for the proteins necessary for the specific cell type.

How does this affect you?
New research points to the possibility of receptors in the nucleus reacting to an ingredient of plastic and provoking insulin resistance. Read about this discovery in my 18 June blog.