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Bones and muscles

Ossification is when human skeletons start off being cartilage which is replaced by the addition of calcium and phosphorus.

There are four main advantages of an internal skeleton; provides the framework of the body, it can grow with body, easy to attatch muscles, flexibility.

Long bones are stronger than solid bones because they are hollow. They have a head with a covering of cartilage and a shaft, which is bone marrow with blood vessels.

If bones break there are dangers to moving them; if any of the bone frgaments are unstable they can move and injure the spinal cord which could possibly paralyse the person.

A synovial joint has hyaline cartilage which reduces fricition and acts as a shock absorber. The synovial membrane produces synovial fluid which keeps the joint lubricated. The tendon joins muscle to bone and the ligaments join bones to bones.

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Blood Circulation and the Heart

Humans have a double circularity system. The first circuit connects the heart to the lungs (the pulmonary artery takes blood to the lungs, the vena cava takes the OXYGENATED blood back to the heart). The second system connects the heart to the rest of the body (the aorta carries the blood away, the pulmonary vein carries the DEOXYGENATED blood back to the heart).


-The bicuspid valve is between the left atrium and the left ventricle.

-The semi lunar valve prevents blood going in the wrong way in the aorta and pulmonary artery.

-The tricuspid valve is between the right atrium and the right ventricle. 

Heart muscle contraction is controlled by a group of cells called the pacemaker which produce a small electric current. The pacemaker cells are called SAN and AVN.

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Problems with circulation

A hole in the heart could cause oxygenated and deoxygenated blood to mix, whilst damaged/weakened valves may allow blood to flow in the wrong direction. A blocked coronary artery will restrict blood flow to the heart or the muscles.

These problems can be solved by heart transplants, which save lives by improving heart function and blood flow. But some people may find it unethical and heart transplants can cause infection, not to mention the fact that an incorrect blood type will result in rejection.

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Blood Components and Coagulation

White blood cells fight disease by producing antibodies and antitoxins. Platelets will form clots or scabs and red blood cells carry haemoglobin which allows them to transport oxygen. The blood plasma is present to keep it runny.

Agglutinins in red blood cells will destroy different types of blood cells, therefore determining how the body will react to new organs/blood.

Haemophilia is an inherited condition where blood doesn't easily clot. Vitamin K, alcohol, green vegetables and cranberries can affect clotting. Warfarin, heparin and aspirin are used to control clotting.

Clotting happens when a damaged blood vessel wall is covered by a clot containing platelets and fibrin. This stops bleeding and starts to repair the damaged blood vessel.

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Fish gills can provide efficient gas exchange in water because the filaments contain a capillary network and provide a large surface area. The water will enter the gills and travel along the filaments whilst the capillary blood flows in the opposite direction providing a large concentration gradient.

Total air is the amount of air you exhale and inhale in a single breath during regular breathing. Vital capacity is the maximum amount of air a person can exhale and residual air is the portion of air in the lungs which can never be expelled. 

Efficient intake and output of air involves the intercostal muscles and diaphragm which change the volume and pressure inside the chest. Efficient diffusion in the lungs is possible because the alveoli have a large surface area and there is a moist surface with a thin lining and good blood supply.

The cilia protect the respiratory system by removing mucus and bacteria from the lungs.

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Lung disease

There are three types of lung disease; industrial (like asbestosis), genetic (like cysic fibrosis) and life style (like lung cancer).

During an asthma attack there will be an increase in mucus, muscle tightening and inflammation and swelling.

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Filtration in the Kidneys

Nephrons are the filtration units in the kidneys. Ultrafiltration happens when a high pressure is built up. This squeezes water, urea, ions and sugar out of the blood vessel into the bowman's capsule. The membrane between the capsule and the blood vessel acts like a filter so big molecules like proteins and blood cells stay in the blood. Useful nutrients (sugar, sufficient water and sufficient ions) are reabsorbed into the blood when the liquid flows along the nephron.

The kidney tubule has a filter unit of glomerulus and the bowman's capsule. It also has a region for selective reabsorbtion and a region for salt and water regulation.

Urea is made by the liver from excess amino acids and is removed by the kidneys. The amount of urine will be affected by the heat, excersise and water intake.

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Water and CO2 Regulation

The amount of water reabsorbed in the kidney nephrons is controlled by anti-diuretic hormones. This is released when the brain measures the water content of the blood and then instructs the pituitary gland to release ADH. 

High levels of CO2 are reduced when the brain detects it and causes an increased breathing rate. 

Dialysis machines are used when kidneys stop working. Blood will flow along a selectively permeable barrier, surrounded by dialysis fluid. The dialysis fluid will have the same concentration of dissolved ions and glucose as healthy blood, meaning that only waste substances and excess ions and water will diffuse across the membrane.

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The Menstrual Cycle

Days 1-4 the lining of the uterus will break down. 

Days 4-14 the lining will build up again. 

Day 14 an egg will develope and be released from the ovary.

Days 14-28 the lining of the uterus will be maintaned. If an egg hasn't been fertilsed the lining of the uterus will break down again.

FSH (follicle stimulating hormone) is produced in the pituitary gland and causes an egg to mature in the ovaries. It also stimulates the ovaries to produce oestrogen, which causes the lining of the uterus to thicken and grow and stimulates the production of LH.

LH (leutenising hormone) is also produced in the pituitary gland but stimulates the release of an egg at day 14.

Progesterone is produced in the ovaries and maintains the lining of the uterus.

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This can be treated by six different methods;

-artificial insemination

-use of FSH


-egg donation


-ovary transplants.

Fertility treatments allow more women to have children, but doesn't always work and can sometimes result in multiple pregnancies.

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Growth and Transplants

Animals grow in the early stages of their lives, whilst plants grow continuously. Both plants and animals produce new cells for growth via mitosis, but in plants growth only occurs at the meristems.

Extremes in height can be caused by genes or hormone inbalances. The human growth hormone is produced in the pituitary gland.

Organ donations are rare because there is a shortage of donors, and issue of tissue match and the size and age can be problematic. Transplants are hard to perform because the new organ may be rejected and immuno-supressive drug treatment is needed. 

There are also problems with using mechanical replacements, such as the size, power supply, body reactions and materials used.

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