1. Human Cells Division And Differentiation
Higher Human Biology
Human Cells
Division And Differentiation

2. Welcome to the class

3. Human Cells - Introduction
This topic will look at human cells.
You should be familiar with these topics from N5
Tissues, organs and systems
Cell division
Cell ultrastructure and function
Cell division and chromosomes
Base sequence and base pairing of DNA
Function of proteins
Enzymes
Summary equation for respiration
ATP and energy
nat5biopl.edubuzz.org

4. Human Cells - Introduction
You will learn:
More about the division of labour in organisms
More about the importance of DNA, its structure and replication
More about the use of DNA technologies
More about the chemistry of respiration and ATP
About metabolic pathways, their importance and how they can be disrupted

5. Division and differentiation in human cells
Somatic cells
What are they?
How many different ones are there in a human?
What do they do?
What DNA do they have?
How do they make copies of themselves?

6. Somatic cells
Specialised differentiated cells that perform a specific function within tissues or organs
Over 200 different types in human body
It depends on the tissues or organs they are in
All of it (46 chromosomes), they are diploid
By the process of mitosis

7. Somatic cells
Skin
Liver
Brain
Muscle
Kidney
Bone

8. Main body tissue types The main body tissue types are: epithelial
connective
muscle
nerve tissue
The body organs are formed from a variety of these tissues.

9. Tissue Stem Cells
Tissue stem cells found in adults develop into cells to replace damaged, worn out, dead cells or to produce more tissue stem cells.
These adult stem cells are limited to the type of cells they can develop into and are called multipotent.
They can only produce the cells for the tissues they are from or self-renew.
An example of tissue (adult) stem cells are blood (haematopoietic) stem cells in bone marrow which can produce red blood cells, platelets and the various forms of phagocytes and lymphocytes.

10. Haematopoietic Stem Cells

11. Epithelial cells
Epithelial cells cover the body surface and line body cavities.
These include linings of breathing system, blood vessels, lymphatic system, kidney tubules, digestive tract, uterus, mouth and obviously skin

12. Connective Tissue Cells
Connective tissue includes blood, bone and cartilage cells.

13. Muscle tissue cells Muscle cells form muscle tissues.
There are 3 different types of muscle:
striated, smooth and heart

14. Nerve Tissue Cells
Nerve cells form nervous tissue.

15. Differentiation In the beginning there was you – a zygote.
You multiplied to produce a blastocyst (ball of cells).
Each cell was identical, produced by mitosis but could develop into any type of cell – PLURIPOTENT
(Called embryonic stem cells when grown in a Lab.)
At some point in development specific areas of the embryo formed.
Those areas were fixed and the cells in specific areas could only perform specific functions.
Cells had undergone differentiation.
There was no going back for differentiated cells.

16. DNA and differentiation
All somatic cells contain a full set of DNA.
During normal embryo development organisation ensures the body develops correctly.
Not all genes are needed to be expressed by all cells.
Genes not required are ‘switched off’ or not expressed.
Genes required by a cell will be expressed (active).
This process is differentiation.

17. DNA and differentiation
What genes will be expressed in most cells?
Why?
Will gene expression change over the lifetime of a human?
How do cells know what genes to express and when?
How complicated is the human body and life!

18. Cell division and mutation
Cell division by mitosis in somatic cells produces diploid cells with 23 homologous pairs of chromosomes.
Tissue stem cells (germline cells) divide by mitosis to produce more germline cells (diploid) or by meiosis to produce haploid gametes.
Mutations in somatic cells only affect the human in which they occur.
Mutations in gametic cells are passed to offspring.

19. Cancer caused by mutation
Somatic cells that mutate can cause cancer.
If the mutation causes a problem with the control of the cell life cycle then they can divide excessively.
A mass of abnormal cells are produced (tumour)
These cells do not respond to regulatory signals.
If the cancerous cells become detached from each other they can spread around the body and cause secondary tumours.

20. Common cancers of somatic cells
Skin
cancer
Lung cancer
Bowel cancer

21. Stem cells and research
Stem cells are researched for their therapeutic uses for the repair of damaged or diseased organs or tissues such as corneal transplants and skin grafts for burns
Stem cell research provides information on how cell processes such as cell growth, differentiation and gene regulation work.
Stem cells can also be used as model cells to study how diseases develop or for drug testing.
There are ethical issues for stem cell use.
The regulation of stem cell research and use is quite significant.

22. Corneal transplants Stem cells can be used instead.
Eye stem cells from the edge of the cornea are taken.
Grown in culture and applied to the damage cornea.
Or they can applied directly between eyes

23. Skin grafts for burns

24. Using stem cells to grow skin
Skin stem cells are taken from patient.
Grown in special conditions
Placed over wounds
Read Case study Therapeutic use of stem cells in textbook

25. Stem cell sources and ethics
Sources of stem cells include embryonic stem cells, tissue stem cells and attempts to reprogram specialised cells to an embryonic state (induced pluripotent stem cells [iPS]).
Embryos used for research must not be allowed to develop beyond 14 days, around the time a blastocyst would be implanted in a uterus.
Ethical issues include regulations on the use of human embryos and the use of iPS cells.
What do you think about the use of stem cells?
Read Case study Embryonic stem cell debate in textbook

26. Consolidation Go over PPT and make your own notes
Read chapter 1 in textbook and make own notes
Complete questions on page 8 and 15
Look at this section on Scholar
Complete multiple choice and matching exercises in book pages 2 to 9