Transcript Document 307085

Differentiation and Stem
Cells
Higher Human Biology
Unit 1 – Sub-Topic 1.1 (a)
Learning Outcomes
To be able to describe the following:
o Differentiation: During embryological development the unspecialised stem
cells of the early embryo differentiate into cells with specialised functions.
o 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.
o In the very early embryo, embryonic stem cells differentiate into all the cell
types that make up the organism.
o Tissue (adult) stem cells are involved in growth, repair and renewal of the
cells found in that tissue. They are said to be multipotent
o The main body tissue types are epithelial, connective, muscle and nerve
o 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 )
o Tissues work together to form more complex organs, systems and organisms
such as humans
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 is when an unspecialised cell becomes specialised in structure
and biochemical properties, making them perfectly adapted for carrying out
a particular function.
http://www.educationscotland.gov.uk/highersciences/humanbiology/animations/stemce
ll.asp
Name as many specialised cells as you can
and describe how their structure relates
to their function (hint there are 9!)
1. Red blood
cell
2. Motor neuron
3. White blood
cell
4. Cheek
epithelium
5. Ciliated
epithelium
6. Goblet cell
7. Smooth
muscle
8. Egg
9. sperm
1.
2.
3.
4.
5.
6.
7.
Biconcave shape and no nucleus for
larger surface area to carry more
oxygen
Axon - Long insulated extension of
cytoplasm
Destruction of invading microbes by
changing shape and use of enzymes
Flat irregular shape allows cells to form
a loose covering for protection
Hair like cilia beat upwards to remove
mucus
Secretes mucus to trap dirt and
microbes
Spindle shape allows cells to form
sheets that can contract together for
movement
Examples of Differentiation
The original pluripotent
embryonic stem cells
gradually differentiate into
specialised cells which form
tissues.
Tissue types include:•Epithelial
•Connective
•Muscle
•Nervous
Types of tissue
Epithelial – Cover the body surface and line body cavities
Ciliated cells of
windpipe
These can be made of a single
layer or a number of layers.
They line body cavities and
tubular structures such as the
oesophagus and blood vessels.
These need to be replaced
constantly.
Flat cells of cheek
Types of tissue
Connective – Includes blood, bone and cartilage
This is
described as
a large
quantity of
extracellular
material
present in
the spaces
between its
cells. The
matrix can
be solid
(bone),
fibrous,
gelatinous
(cartilage) or
liquid (blood
plasma).
Bone
This is made up of calcified material laid down around blood vessels. Live
blood cells need a supply of oxygen and essential nutrients. They get this
through tiny canals in contact with blood vessels.
Cartilage
Cartilage is an important structural component of the body. It is a firm tissue
but is softer and much more flexible than bone. Cartilage is a connective tissue
found in many areas of the body including: Joints between bones e.g. the elbows,
knees and ankles. Ends of the ribs. There are different types of cartilage
Hyaline cartilage
This is a low-friction, wear-resistant tissue present within joints that is
designed to bear and distribute weight. It is a strong, rubbery, flexible tissue
but has a poor regenerative capacity.
Elastic cartilage
Elastic cartilage is more flexible that hyaline cartilage and is present in the ear,
larynx and epiglottis.
Fibrocartilage
Fibrocartilage is a tough and inflexible form of cartilage found in the knee and
between vertebrae.
Articular cartilage
Articular cartilage is the hyaline cartilage that lies on the surface of bones. This
cartilage is often described in terms of four zones between the articular
surface and the subchondral bone which include:
Blood
Blood is called connective tissue because its extracellular space (about half its
volume) is composed of plasma
Types of tissue
Muscle cells – Form muscle tissue capable of contraction
Skeletal Muscle
Muscles that move your
skeleton
Cardiac Muscle
Muscles cells of the heart
has branches in contact
with adjacent cells.
Smooth Muscle
Muscles in the intestine and
blood vessels. These are
spindle shaped and arranged
in sheets.
Types of tissue
Nervous cells– Form nerve tissue
Nerves carry
messages from sense
organs to the brain
and then return
signals to muscles.
This tissue is made up
of a network of nerve
cells called neurons
and glial cells which
support and maintain
the neurons.
Differentiation in Somatic
Cells
Higher Human Biology
Unit 1 – Sub-Topic 1.1 (b)
Learning Outcomes
(a) Somatic cells divide by mitosis to form more
somatic cells.
(b) Cellular differentiation is the process by
which a cell develops more specialised functions
by expressing the genes characteristic for that
type of cell.
Once a cell becomes differentiated it only
expresses the genes that produce the proteins
characteristic for that type of cell.
Somatic cells
Somatic cells are the differentiated cells that
form the different types of body tissue that exist
• Somatic cells have stopped growing and only express
the genes that produce the proteins characteristic
for that type of cell, e.g nerve cells will only express
proteins involved in the transmission of nerve
impulses
Smooth muscle
B Lymphocyte
Hyaline cartilage
Somatic cells
neutrophil
Ciliated epithelial cell
platelets
Red blood cell
Somatic cells
Cardiac muscle
Squamous epithelial cells
Nerve cells
T lymphocyte
Differentiation in Germline
Cells
Higher Human Biology
Unit 1 – Sub-Topic 1.1 (c)
Learning Outcomes
o The nucleus of germline cells have 23 pairs of chromosomes and are
said to be diploid.
o When germline cells divide by mitosis they can produce new diploid
cells
o Germ line cells called gamete mother cells found in the sex organs
give rise to sex cells i.e. Sperm and eggs
o The nucleus of a gamete mother cells may also divide by meiosis to
produce sex cells with only 23 individual chromosomes.
o Sex cells or gametes are said to be haploid .
o Mutations that occur in germline cells will be passed to offspring
whereas mutations in somatic cells will not.
Germline cells
Germline cells include the sex cells or gametes and the
cells that produce the gametes called gamete mother
cells
The nucleus of a gamete mother
cells may also divide by meiosis
to produce sex cells with only 23
individual chromosomes.
To see a lovely explanation of how
chromosome numbers are halved during
meiosis click here
Questions
1. Draw a labelled diagram of mitosis
2. What cells are involved in mitosis?
3. How many chromosomes are present in
the mother and daughter cells?
Division of germline cells
• Germline cells can
divide by mitosis to
produce more
germline cells
• Gamete mother cells
divide by meiosis to
produce gametes
In the diagram above ‘n’ just means sets. In normal cells produced by
mitosis there are two sets but in gametes produced by meiosis there is
only one set
Mutations
If a mutation occurs in a
germline cell then it will be •
passed onto the offspring.
For example: Cystic
Fibrosis
A gene mutation on
chromosome 7 may become
the recessive form (leading
to production of thick and
sticky mucus). This mutant
allele is passed onto gametes
during meiosis. If the other
parent is a carrier of the
same recessive allele then
the resulting zygote will be
a cystic fibrosis sufferer.
If a mutation
occurs in a
somatic cell e.g. a
mole then this will
not be passed
onto the offspring
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.
Somatic cells are
any cells that are
not reproductive.
Germline cells are
cells that
eventually lead to
the formation of
sex cells
(gametes).
Types of stem cells
Embryonic
•Found in blastocyst
•Pluripotent ( can make all
cell types)
•Called embryonic when
they self re-new in the lab
Adult – also known as tissue
•Found in specific areas of
the body e.g. Bone marrow
•Multipotent ( can only
make cell types in a
particular tissue
Embryonic stem cells
• Embryonic stem cells
are derived from an
embryo about 4–5
days old (blastocyst).
• These cells have the
ability to
differentiate into all
of the cell types that
make up an organism.
They are said to be
pluripotent
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 multipotent
• These cells replenish
differentiated cells that need
replaced in the tissues in which
they are found.
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.
Stem cell research
1.
2.
3.
4.
5.
Stem cell research provides us with
a wealth of information and can be
studied in a variety of ways,
including:
How cell processes such as growth,
differentiation and gene regulation
work
The study of diseases and their
development
Drug testing
Therapeutic uses in the treatment
of diseases such as leukaemia (bone
marrow transplant), Hunter’s
disease and heart disease
Therapeutic uses in medicine
including skin grafts for burns and
stem cell grafts for cornea repair
For example, stem cells could be turned into new bone
cells, and then injected into weak or broken bones.
Or, they could become nerve cells that could
heal spinal cord injuries,
Skin cells could replace burnt skin, or brain
cells that could help people who have
suffered brain damage.
Stem cells could be taken from someone with heart disease
and be turned into heart cells, which can gather in a dish
and throb!
They could then be injected back into the patient to
rebuild their heart tissue and combat heart disease.
Parkinson's disease
Parkinson's is a very common disease
starting with mild symptoms, a mask-like
face, stiffness, tremors until sufferers
eventually become immobile. It's caused
by a slow deterioration of certain brain
cells (neurons) and there's no cure.
Actor
Michael J.
Fox.
Former
boxer
Muhammad
Ali
Replacing the affected brain cells seems more hopeful than finding better
drugs. Many think that stem cells could be grown into new brain cells which
will help to treat or even cure Parkinson's.
Nuclear
Transfer
Technique
for
therapeutic
stem cell
cloning
Induced pluripotent stem cells
Induced pluripotent stem cells are adult cells
that have been genetically reprogrammed to an
embryonic stem cell-like state.
http://www.bbc.co.uk/news/science-environment-19878542
http://www.bbc.co.uk/news/science-environment-19872346
Questions and Answers
1. What process is responsible for unspecialised cells becoming different
• Differentiation
2. Name the four 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
Cancer
Higher Human Biology
Unit 1 – Section 1 (e)
Learning Outcomes
o Cancer cells divide excessively to
produce a mass of abnormal cells (a
tumour) that do not respond to
regulatory signals and may fail to attach
to each other.
o If the cancer cells fail to attach to
each other they can spread through the
body to form secondary tumours.
Cancer cells
Cancer cells have many
characteristics that make them
different from normal cells:
• Cancer cells continue to
reproduce to produce a mass of
abnormal cells (a primary tumour).
To see a very nice overview
explaining what cancer is
click here
• Cancer Cells do not respond to
normal regulatory signals that
would instruct them to stop
dividing when necessary.
• Cancer cells lose the molecules on
their surface that would normally
hold them in place and can
therefore be detached from
their neighbours, causing the cells
to spread (secondary tumour).
Skin cancer cells (melanoma)
Benign or Malignant
Tumours can be either
benign or malignant.
Benign tumours aren't
cancer. Malignant ones are.
Benign tumours grow only in
one place.
Benign tumours cannot
spread or invade other parts
of your body. Even so, they
can be dangerous if they
press on vital organs, such
as your brain.
10 Cancer Facts from the World Health Organisation
Warning – You will not be asked details from below but we thought this
information is important and links to stem cells as possible treatments
Fact 1
There are more than 100 types of cancers; any part of the body can be
affected.
Fact 2
In 2008, 7.6 million people died of cancer - 13% of all deaths worldwide
Fact 3
About 70% of all cancer deaths occur in low- and middle-income countries.
Fact 4
Worldwide, the 5 most common types of cancer that kill men are (in
order of frequency): lung, stomach, liver, colorectal and oesophagus.
Fact 5
Worldwide, the 5 most common types of cancer that kill women are (in
the order of frequency): breast, lung, stomach, colorectal and cervical. In
many developing countries, cervical cancer is the most common cancer.
Fact 6
Tobacco use is the single largest preventable cause of cancer in the world
causing 22% of cancer deaths
Fact 7
One fifth of all cancers worldwide are caused by a chronic infection,
for example human papillomavirus (HPV) causes cervical cancer and
hepatitis B virus (HBV) causes liver cancer
Fact 8
Cancers of major public health relevance such as breast, cervical and
colorectal cancer can be cured if detected early and treated adequately
Fact 9
All patients in need of pain relief could be helped if current knowledge
about pain control and palliative care were applied.
Fact 10
More than 30% of cancer could be prevented, mainly by not using
tobacco, having a healthy diet, being physically active and moderating
the use of alcohol. In developing countries up to 20% of cancer deaths
could be prevented by immunization against the infection of HBV and
HPV.
Lifestyle and cancer
The risk of getting cancer can be
reduced by changes in lifestyle.
For ten tips on how to reduce your
risk of getting cancer click here
For an overview on how stem cells are
being investigated as a way of studying
and treating cancer click here
Questions
• How are cancer cells different from other
cells?
• What is a tumour?
• How does a cancer spread?
• What is the difference between a malignant
tumour and a benign tumour?
• Give one way in which stem cells are being
studied as a form of cancer treatment?