Transcript lesson 4 PC 2.3 Cell Structure & Keratinisation

Cell Structure
•
•
•
•
Human cells are too small to see
without the use of a microscope, but
they all have a:
Nucleus
Centrosome
Cytoplasm
Cell Membrane
1
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.
2
Centrosome
The 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.
3
Cytoplasm
• This is the name of the liquid inside the
membrane.
• Everything inside the cell floats in this
liquid.
4
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.
5
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)
6
Oxygen
• Cells need to breath they take
oxygen from the blood and pass
carbon dioxide back to the blood
stream. This is called respiration
7
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.
8
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.
9
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.
10
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.
11
• 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.
12
13
14
The newly formed cell then
moves away from the matrix
and into the hair bulb.
15
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.
16
 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.
18
 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%.
19
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
21