1. Differentiation and Stem Cells
Higher Human Biology
Unit 1 – Sub-Topic 1 (a)

2. Learning Intention
To discuss what differentiation of cells is and to gain knowledge of the types of stem cells

3. Why have specialised cells?

4. Introduction
The human body is made up of many specialised cells that perform specific functions.
Specialised cells arise from the differentiation of unspecialised cells during embryological development.
Differentiation also occurs in later developmental stages tissue repair etc in mature adults
Link is to an animation on differentiation
Differentiation is when an unspecialised cell becomes specialised in structure and biochemical properties, making them perfectly adapted for carrying out a particular function.

5. Examples of Differentiation
The original pluripotent embryonic stem cells gradually differentiate into specialised cells which form tissues.
Tissue types include:-
Epithelial
Connective
Muscle
Nervous

6. Epithelial – Cover the body surface and line body cavities
Types of tissue
Epithelial – Cover the body surface and line body cavities
Ciliated cells of windpipe
Flat cells of cheek

7. Types of tissue
Connective – Includes blood, bone and cartilage

8. Muscle cells – Form muscle tissue
Types of tissue
Muscle cells – Form muscle tissue
Muscles that move your
skeleton
Muscles of the heart
Muscles in the intestine and blood vessels

9. Types of tissue
Nervous cells– Form nerve tissue
Nerve carry messages from sense organs to the brain and then return signals to muscles.
DON’T LEARN

11. What are stem cells?
Stem cells are unspecialised somatic cells that have the ability to reproduce and differentiate into a diverse range of specialised cells.
Why relatively? It is either unspecialised or not

12. Stem cell definitions
Potency……….. A measure of how many types of specialized cell a stem cell can make
Stem cell type
Description
Examples
Totipotent
Each cell can develop into a new individual
Cells from early (1-3 days) embryos (zygote)
Pluripotent
Cells can form any (over 200) cell types
Some cells of blastocyst (5 to 14 days)
Multipotent
Cells differentiated, but can form a number of other tissues
Fetal tissue, cord blood, and adult stem cells
Unipotent
Can give rise to only 1 cell type
Spermatogonial cells in testicles only make sperm
Stem cell jargon
Scientists use the words pluripotent and multipotent to help them describe stem cells. ALL stem cells can both self-renew and differentiate, BUT some stem cells can make more kinds of specialized cells than others. The terms on the slide are the key ones to remember. There are also stem cells that are:
TOTIPOTENT: can differentiate into all types of specialized cells in the body PLUS cells that are needed during development of the embryo only: placenta, yolk sac, umbilical cord.
UNIPOTENT: can only differentiate into one type of specialized cell. For example, spermatogonial stem cells (found in the testicles) are unipotent because they can only form sperm cells.
A useful place to look up other words and phrases to do with stem cells is the EuroStemCell online glossary: 12

13. Types of stem cells Adult – also known as tissue Embryonic
Found in blastocyst
Pluripotent ( can make all cell types)
Called embryonic when they self re-new in the lab
Found in specific areas of the body
e.g. Bone marrow
Multipotent ( can only make cell types in a particular tissue

14. Embryonic stem cells
Embryonic stem cells are derived from an embryo about 4–5 days old (bastocyst).
These cells have the ability to differentiate into all of the cell types that make up an organism. They are said to be pluripotent

15. Adult (tissue) stem cells
Adult or tissue stem cells are found in small numbers in the tissues and organs of adults and children, including the brain, bone marrow, skeletal muscle and skin.
These cells give rise to a much more limited range of cell types and will tend to develop into cell types that are closely related to the tissue in which they are found. They are said to be mutipotent
These cells replenish differentiated cells that need replaced in the tissues in which they are found.

16. Other types of stem cells
Stem cells can also be taken from the umbilical cord of new babies.
Like adult stem cells, these cells can differentiate into a limited range of specialised cells.

17. Induced pluripotent stem cells
Induced pluripotent stem cells are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state.
First video is method used by Gurdon and Yamanaka
Second Video is an interview with Gurdon

18. System Cell Organism Tissue
Questions and Answers
What process is responsible for unspecialised cells becoming different?
2. Name the 3 other different types of tissue and give an example of each
Epithelial e.g. Cheek cells
3. What are stem cells and name the two types of stem cells?
4. In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism. What term is used for cells that can do this?
5. Tissue (adult) stem cells are involved in growth, repair and renewal of the cells found in that tissue. What term is used for cells that can do this?
6. Put the following in the correct order of complexity
System Cell Organism Tissue

19. System Cell Organism Tissue
Questions and Answers
What process is responsible for unspecialised cells becoming different
Differentiation
2. Name the 3 other different types of tissue and give an example of each
Epithelial e.g. Cheek cells
Connective e.g. Blood, bone or cartilage
Muscle e.g. Skeletal, cardiac or smooth
Nerve e.g. Sensory or motor nerves
3. What are stem cells and name the two types of stem cells
Stem cells are unspecialised somatic cells that have the ability to reproduce and differentiate into a diverse range of specialised cells
Embryonic and Adult ( tissue )
4. In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism. What term is used for cells that can do this?
Pluripotent
5. Tissue (adult) stem cells are involved in growth, repair and renewal of the cells found in that tissue. What term is used for cells that can do this?
Multipotent
6. Put the following in the correct order of complexity
System Cell Organism Tissue

20. Learning Outcomes
Differentiation: During embryological development the unspecialised
stem cells of the early embryo differentiate into cells with specialised
functions.
Stem cells: Stem cells are unspecialised somatic cells that can divide to make
copies of themselves ( self renew ) and can differentiate into specialised cells of one or more types.
In the very early embryo, embryonic stem cells differentiate into all the cell types that make up the organism.
Tissue (adult) stem cells are involved in growth, repair and renewal of the cells found in that tissue. They are said to be multipotent
The main body tissue types are epithelial, connective, muscle and nerve
Multipotent haematopoietic stem cells in the red bone marrow give rise to all the cell types in the blood e.g. red blood cells, platelets and the various forms of phagocytes and lymphocytes.( see previous lesson )
Tissues work together to form more complex organs, systems and organisms such as humans