Higher Human Biology Unit 1: Human Cells

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1 Higher Human Biology Unit 1: Human Cells Key Area 1.1: Division & differentiation in human cells

2 Learning Outcomes Somatic stem cells divide by mitosis to form more somatic cells. Germline stem cells divide by mitosis and by meiosis. Division by mitosis produces more germline stem cells. Division by meiosis produces haploid gametes.

3 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

4 A somatic cell is any cell in the body other than cells involved in reproduction.

5 Somatic cells neutrophil Ciliated epithelial cell platelets Red blood cell

6 Somatic cells Cardiac muscle Squamous epithelial cells Nerve cells T lymphocyte

7 Germline Cells 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

8 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. o Germline cells are gametes (sperm and Ova) and the stem cells that divide to form gametes.

9 Germline 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

10 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?

11 Division of germline cells Germline cells can divide by mitosis to produce more germline cells Gamete mother cells divide by meiosis to produce gametes

12 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

13 Differentiation 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.. Cellular differentiation is the process by which a cell expresses certain genes to produce proteins characteristic for that type of cell. This allows a cell to carry out specialised functions.

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15 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).

16 Embryonic Types of stem cells Adult also known as tissue 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

17 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

18 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.

19 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.

20 Stem cell research Stem cell research provides us with a wealth of information and can be studied in a variety of ways, including: 1. How cell processes such as growth, differentiation and gene regulation work. 2. The study of diseases and their development. 3. Drug testing. 4. Therapeutic uses in the treatment of diseases such as leukaemia (bone marrow transplant), Hunter s disease and heart disease. 5. Therapeutic uses in medicine including skin grafts for burns and stem cell grafts for cornea repair.

21 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.

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23 Nuclear Transfer Technique for therapeutic stem cell cloning

24 Induced pluripotent stem cells Induced pluripotent stem cells are adult cells that have been genetically reprogrammed to an embryonic stem cell-like state.

25 Ethical Issues Sources of stem cells include embryonic stem cells, tissue stem cells and attempts to reprogram specialised cells to an embryonic state. Ethical issues surrounding the use of embryonic cells include the destruction of the human embryo when extracting the human embryonic stem cells.

26 Regulations Regulations on the use of embryonic stems cells include embryo cells must not be allowed to develop beyond 14 days, around the time a blastocyst would implant into the uterus.

27 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

28 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.

29 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). Cancer Cells do not respond to normal regulatory signals that would instruct them to stop dividing when necessary. To see a very nice overview explaining what cancer is click here 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)

30 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. Benign or Malignant

31 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.

32 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.

33 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?