Differentiation and Stem Cells Higher Human Biology Unit

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/stemc ell. asp

Name as many specialised cells as you can and describe how their structure relates to their function (hint there are 9!) 1. 2. 3. 4. 5. 6. 7. 8. 9. Red blood cell Motor neuron White blood cell Cheek epithelium Ciliated epithelium Goblet cell Smooth muscle Egg 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 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 is more flexible that hyaline cartilage and is present in the ear, larynx and epiglottis. Fibrocartilage is a tough and inflexible form of cartilage found in the knee and between vertebrae. 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 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 Muscles that move your skeleton Cardiac Muscles cells of the heart has branches in contact with adjacent cells. Smooth 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 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 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 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 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?