Download - module B3 revision part 3
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!)