Cell StructureHuman cells are too small to see without the use of a microscope, but they all have a:

• Nucleus• Centrosome• Cytoplasm• Cell Membrane

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Nucleus

The nucleus (often called the cells brain) is the most important part of the cell.

• The nucleus controls the cells activities including reproduction and cell division.

• The nucleus also contains chromosomes, which pass on heredity traits from parent cells.

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CentrosomeThe Centrosome controls cell reproduction, it only appears when the cell is ready to reproduce. It helps the nucleus organise and control reproduction of the cell.

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Cytoplasm

• This is the name of the liquid inside the membrane.

• Everything inside the cell floats in this liquid.

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Cell Membrane

• The Cell Membrane is the outside wall of the cell, which holds the cell together. If the cell membrane is damaged the cell will die.

• The cell membrane allows oxygen and food to enter the cell and carbon dioxide and other cell waste products out.

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Cell Function

All cells need to do four main things to live:

• A cell needs oxygen (Respiration)• A cell need energy (Digestion) • A cell must remove waste

(Excretion)• A cell must reproduce (Mitosis)

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Oxygen

• Cells need to breath they take oxygen from the blood and pass carbon dioxide back to the blood stream. This is called respiration

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Energy

• Cells need to take in food from the blood stream and break it down into smaller, more useable parts. This is called digestion. Cells get energy from food that has been broken down.

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Removal of waste

• Cells have to get rid of waste they do this by passing the waste into the blood stream. This is called excretion.

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Cell Division

• Cells need to keep reproducing to replace the cells that die.

• The cells of hair and skin reproduce during a process known as mitosis.

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Mitosis

• Mitosis is the active reproduction of human cells.

Mitosis takes place in the Germinal Matrix Layer

• The germinal matrix layer is a special group of cells at the base of the follicle that are responsible for the reproduction of cells resulting in new hair growth.

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• When the cells of the matrix commence the activity of mitosis, the changes that occur are:

• The nucleus and all of the units of the cell that give it its characteristics, halve, separate and prepare to divide by moving to opposite sides of the cell.

• At this point the cell membrane grows down and divides the cell into two equal parts.

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The newly formed cell then moves away from the matrix and into the hair bulb.

Keratinisation

Cells at the germinal matrix are constantly dividing. As the new cells are formed in the germinal matrix they push the older cells up towards the top of the follicle.

While the cells travel along the follicle to eventually become the hair we see, they go through a number of changes.

This process is called Keratinisation.

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Once the cells have gone through these changes they will have become a new structure called keratin.

Keratin is a protein. Hair is 97% hard keratin Hard keratin (hair)contains more

sulphur than soft keratin(skin) Hard keratin contains less moisture

than soft keratin 17

The structure of hard keratin is in long fibers.

The structure of soft keratin is in flat sheets.

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When the cells are going through keratinisation there are four major changes that take place

1. Cells loose most of their moisture. The moisture level of the cell starts at 90%and ends up at 10%.

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2.Cells change their shape. The nucleus of the cell becomes oval.It is at this stage, the hair cell becomes part of either the cuticle, cortex or medulla.

3.Bonds form between the atoms to make polypeptide chains.

4.Cells loose their nucleus, cytoplasm, centrosome and the cell membrane. 20

These changes take place in the bottom 1/3 of the Follicle

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