REVISION

Part 3

What am I?

Name the cell

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Blood• Plasma – a yellow liquid, adapted to transport

dissolved substances such as water, hormones, antibodies and waste products

• Red blood cells – transport oxygen around the body. Red colour comes from haemoglobin. Oxygen joins to the haemoglobin to form oxyhaemoglobin, which allows it to be transported around the body. They do not have a nucleus – this leaves more room to carry oxygen. They are disc-shaped and have a dent on both sides – this allows them to absorb a lot of oxygen. They are very small so they can carry oxygen to all parts of the body.

• White blood cells – defend the body against disease. They are adapted to change shape, they can wrap around microbes and engulf them. They can squeeze through capillary walls to reach microbes.

• Platelets – help to clot the blood if we cut ourselves.

Is a ‘straw’ coloured liquid which suspends white and red blood cells together with platelets in the Blood

Arteries

Arteries carry high pressure blood Away from the heart.

Lumen

EndotheliumElastic Fibres &

Smooth Muscle

Veins

Veins carry low pressure blood back to the heart.

They have thinner, less elastic walls and

have Valves to prevent backflow of blood.

Large Lumen

Endothelium

Capillaries • Have thin walls

one cell thick! (to allow glucose and oxygen to pass through).

• Are also used to connect arteries to veins.

Thin endotheliu

m

Blood vessels• Artery – thick muscular and elastic wall to

help it withstand high blood pressure as the blood leaves the heart.

• Vein – large lumen (hole) to help blood flow at low pressure; valves stop blood from flowing the wrong way.

• Capillary – thin, permeable wall to allow exchange of material with body tissue

Label me

Aorta

Pulmonaryvein

Pulmonary artery

Vena cava

Vena cava

The Heart1. Deoxygenated blood (i.e. blood without oxygen) enters through the vena cava into the right atrium

2. It’s then pumped through the tricuspid valve into the right ventricle

3. It’s then pumped through the semi-lunar valve up to the lungs through the pulmonary artery

4. Oxygenated blood from the lungs enters through the pulmonary vein into the left atrium

5. It’s then pumped through the bicuspid valve into the left ventricle

6. It’s then pumped out of the aorta to the rest of the body

The Heart

• Structure• Four chambers• Two atria – receive blood from the veins• Two ventricles – pump blood into arteries• Valves – bicuspid, tricuspid, semi-lunar valves

– prevent the blood flowing backwards when the heart relaxes and so maintain blood pressure.

• Four key vessels • Right hand side:

– vena cava, pulmonary artery

• Left hand side:– pulmonary vein, aorta

• Function• The heart pumps blood

around the body. There are two sides to a heart.

• The right side pumps blood to the lungs

• The left side pumps blood to the rest of the body

• The blood leaves the heart in arteries where the pressure is high.

• The blood returns to the heart at low pressure in the veins.

• Heart problems• Blood flows through arteries at high pressure.

Saturated animal fats such as cholesterol can stick to the walls of arteries. This can slow down or block the flow of blood. If this happens in a main blood vessel it can cause a heart attack or a stroke.

• Mending the heart• Mechanical – heart valves• Biological – heart transplant

Divide and Rule

• Every day new cells are made. To do this the body carries out cell division. Cells divide whenever the body needs to:

• Grow• Replace worn out cells• Repair damaged tissue

Mitosis

• Cell resting• Each chromosome is copied, the single strand

forms double-stranded “X” shape• Spindle forms, chromosomes arranged along

equator• Chromosome single strands move to poles of

cell• Two genetically identical cells are produced.

What Are the Stages of Mitosis?

1. DNA all spread out in long strings

2. DNA forms into chromosomes (Remember, the double arms are already duplicates of each other)3. Chromosomes line up at the centre and the cell fibres pull them apart

4. Membranes form around the two sets of chromosome threads. (These become the nuclei of the daughter cells)

5. The threads unwind into long strands of DNA ……. and the whole process starts again!

Meiosis

• A special type of cell division that produces gametes. Gametes are made when diploid cells divide by meiosis to produce haploid cells. Meiosis involves two cell divisions. First the chromosomes separate then the chromosomes divide in the same way as mitosis

MITOSIS MEIOSISReplication followed by ONE DIVISION

Replication followed by TWO DIVISIONS

Results in SAME number of chromosomes

Results in HALF the number of chromosomes

Occurs in ALL normal body cells

Occurs in special cells in OVARIES and TESTES

Used for GROWTH & REPAIR

Used for production of EGG & SPERM

Gametes

Egg• Much larger than the

sperm because it contains food for the developing embryo

• The nucleus of an egg contains genes which hold the instructions to make new cells

Sperm• Much smaller than the egg• Has a tail to help it move• Male releases millions of sperm

to increase the chance of one reaching the egg

• The nucleus of a sperm contains genes which are the instructions to make new cells

• Sperm have to travel along way and then get inside an egg – they have large numbers of mitochondria to release energy for motion.

• Sperm also have a structure called an acrosome – this releases enzymes that digest the cell membrane of an egg and allows the sperm inside.

Egg

Haploid

23 chromosomes

Sperm

Haploid

23 chromosomes

Zygote

(fertilised egg)

Diploid

46 chromosomes

Cell in ovary

Diploid

46 chromosomes

Cell in testes

Diploid

46 chromosomes

Fertilisation

MeiosisMeiosis

Mitosis

Genetic disorders• Haemophilia: an inherited condition , affects

blood clotting. It is sex linked, this means it is carried on an X chromosome. Haemophilia is a recessive disorder. This means if a woman has inherited a healthy X chromosome from one parent and a damaged “haemophilia” chromosome from the other parent, the healthy chromosome dominates and she does not suffer from haemophilia – she does carry it and may pass it on though. A man has only one X chromosome (XY), if he inherits a haemophilia X chromosome he will suffer from it.

Can you do a genetic cross for:

• Carrier female and unaffected male• Carrier female and affected male (very rare!)