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B5 - The living Body

Bones and Cartilage
1. The advantages of having external skeleton are:
  1. It can easily grow within the body
  2. It's easy to attach muscles to it
  3. It's more flexilble than an exoskaleton
  4. It gives the body support and provides a framework
2. Bones
  1. Bones are Living tissue
    1. Bones are made up of living cells, so they can grow and repair themselves if damaged.
    2. Long Bones are hollow, this makes them hollow which makes themstronger and movement far more efficient.
      1. The hole in the middle of some long bones is filled with bone marrow, bone marrow is a spongy substance that makes new blood cells.
    3. Even when bones are no longer growing, bone tissue is constantly being broken down and renewed.
  2. Fish, Amphibians, Reptiles, Birds and Mammals are all vertebrates.
  3. Insects are Invertebrates, so they have an exoskeleton.
3. Cartilage
  1. Bones are living tissue that start off as cartilage
  2. Bones start off as cartilage in the womb. Cartilage is a living tissue that looks and feels rubbery. it can grow and repair itself too.
  3. As you grow, a lot of cartilage is replaced by bone. Blood vessels deposit calcium and phosphorus in the cartilage, this eventually hardens into bone. This process is called ossification.
  4. You can tell if someones still growing by looking at how much cartilage is present
  5. Even when you're fully grown, the ends of the bones remain covered with cartilage to prevent friction between them..
4. Bones and Cartilage can get damaged
  1. Cartilage and bone are both made up of living tissue, so can get infected
  2. Even though bones are strong, they can be fractured or broken by a sharp knock.
    1. Fractures are hard tissue injuries where the bone cracks or breaks, the tissue around the bone can also get damaged.
    2. It can be dangerous to move someone with a suspected fracture as moving them could cause further damage to the bone, tissue and nervous system.
    3. There are three types of fractures:
      1. Compound (open) fractures are when the skin is broken and part of the bone is sticking out, this is the most serious type of fracture.
      2. Simple (closed) fractures are when the bone is cracked but the skin isn't broken.
      3. Greenstick fractures are when the bone is cracked on one side and bent on the other.
  3. Elderly people are more prone to brake bones as they are more brittle Elderly people often suffer from osteoporosis, this is where calcium is lost making the bones softer.
Heart-Rate, The Cardiac cycle and Circulatory System
1. Bicuspid valve
2. The heart is a muscular organ located in the thorax. It pumps blood continuously around the body.
3. The blood supplies cells with oxygen and glucose, needed for respiration.
4. The blood also transports the waste products, such as carbon dioxide, the waste product of respiration, and urea.
5. Special arteries called coronary arteries carry blood to the heart to supply the heart muscle cells with oxygen and glucose for contraction .
6. Circulatory systems
  1. A circulatory system consists of a group of organs that transport substances, such as oxygen, around the body.
  2. Some organisms, such as insects, have an open circulatory system, where the fluid moves freely between cells.
  3. Other organisms, including humans, have a closed circulatory system where blood is contained within vessels, where these factors can be controlled:
    1. The speed of the blood flow
    2. The pressure of the blood
    3. The distribution of blood in the body
  4. A single circulatory system has a two-chambered heart so that blood can be returned to one chamber, and pumped back out of the heart from the second chamber. This ensures blood flow in one direction only.
  5. Humans and other mammals have a double circulatory system. This has two circuits from the heart, one to the body and the other to the lungs.
  6. In a double circulatory system, you need a for chambered heart. This allows the blood to be pumped separately to the lungs and to the body, this is important for maintaining a high pressure.
    1. In animals with a Single circulatory system, the blood loses as its pumped to the gills and then around the rest of the body, this means overall pressure is relatively low.
    2. Keeping the blood pressure at a higher pressure allows materials to be transported around the body more quickly
  7. Unborn babies don't need a Double circulatory system. they get their oxygen from their mother via the placenta, so their blood doesn't need to travel to their lungs. As a result all unborn babies have a hole in their heart which allows blood to bypass the lungs. It closes up soon after birth.
7. The Cardiac cycle
  1. The heart pumps blood around the body by contracting and relaxing the atria and ventricles in sequence.
  2. Blood is prevented from flowing in the wrong direction by the atrio-ventricular and semilunar valves.
  3. The sequence of events in one complete heartbeat is called the cardiac cycle:
    1. 1. Blood flows into the two atria, the semilunar valves are closed and the atrio-ventricular valves are open.
    2. 2. The atria contracts, pushing the blood into the ventricles
    3. 3. The ventricles contract, forcing the blood into the aorta and pulmonary artery. This causes the semilunar valves to open and the atrio-ventricular valves automatically close.
    4. 4. The blood then flows along the arteries, the atria fill again and the cycle starts over.
8. Heart rate
  1. Heart rate changes according to activity
    1. When you exercise, your muscles need more oxygen to work harder, so you need to breath faster. Your heart also pumps faster to deliver more oxygenated blood to your muscles.
    2. Hormones can also effect your heart rate, e.g. Adrenaline increases heart rate to make sure your muscles have plenty of oxygen.
  2. The heart has a pacemaker
    1. The heart is told how fast to beat by a group of cells called pacemakers
    2. These cells produce a small electric current which spreads to the surrounding muscle cells causing them to contract
    3. The Cardiac cycle and circulation
      1. The sino-atrial node (SAN) stimulates the atria to contract
      2. The Atio-ventricular node (AVN) stimulates the ventricles to contract
      3. In one heartbeat the SAN produces an electric current first, which spreads to the atria (making them contract). The current current stimulates the AVN to produce an electric current (causing the ventricles to contract) . This process ensures that the atira always contract before the ventricles.
      4. An artificial pacemaker is often used to control heartbeat if the pacemaker calls are defective, it's a little device that's implanted under the skin and has a wire going to the heart where an electric current is produced.
  3. ElectoCardioGram's (ECG's) measure the heart
    1. ECG's shows the electrical activity of the heart, they can show:
      1. Heart Attacks
      2. Irregular heartbeats
      3. The general health of the heart
      4. The diagram below shows a normal ECG:
9. Heart Disease
  1. There are three main ways the heart can go wrong:
    1. 1. Hole in the heart: A hole in the heart is a gap in the wall separating either the two ventricles or the two atria. It allows blood to move directly from one side of the heart to the other. This allows deoxygenated blood and oxygenated blood to mix, which reduces the amount of oxygen in the blood being pumped to the body.
      1. A hole in the heart sometimes needs to be corrected by surgery.
    2. 2. Valve damage: The valves in the heart can be weakened by heart attacks, Infection or old age. The damage may cause the valve not to open properly, causing high blood pressure. It may even allow blood to flow in both directions rather than just forwards, this means it doesn't circulate as effectively as normal.
      1. Severe valve damage can be treated with replacing the valve with an artificial one.
    3. 3. Coronary Heat Disease: CHD is when the Coronary Arteries supplying blood to the heart muscle get blocked by Fatty deposits. This reduces blood flow to the heart muscle and often results in a heart attack.
      1. It can be treated by a Coronary bypass operation, where a piece of blood vessel is taken from another part of the body and inserted to bypass the blockage.
10. Artificial parts can be used instead of Heart transplants
  1. 1. The main advantage of using artificial parts (valves and pacemakers) is that rejection isn't normally a problem. They're usually made from metals or plastics, which the body can't recognise as foreign in the same way as it does with living tissue.
  2. 2. Replacing a valve is a much less drastic procedure than a transplant, and inserting a pacemaker only involves a short stay in hospital.
  3. 3. However, the main disadvantage is that the new valves and pacemakers might not last very long and will need replacing as a result.
Blood Cloting and Transfusions
1. Blood sometimes doesn't clot properly
  1. 1. when you're injured, your blood clots to prevent too much bleeding. A clot is a mesh of fibrin fibre proteins that plugs the damaged area. Clots are formed by a series of chemical reactions that take place when platelets (small fragments of cells that help blood clot) in your blood are exposed to damaged blood vessels.
  2. 2. Too little clotting could mean you bleed too death. too much clotting can cause strokes and Deep Vein Thrombosis (DVT)
  3. 3. People who are at risk of strokes or DVT can take drugs to reduce their risk. Warfarin, heparin and aspirin all help prevent the blood from clotting.
  4. 4. Haemophilia is a genetic condition where the blood doesn't clot easily because a clotting factor can't be made by the body, this missing clotting factor can be injected.
2. Blood type is important in Transfusions
  1. 1. When you have lost a lot of blood, you will need it to be replaced in a transfusion, using blood from a blood donor.
  2. 2. People have different blood groups, you can be anyone of: A, B, AB or O. These letters refer to the type of antigens on the surface of a persons red blood cells (an antigen is a substance that can trigger a response from the body's immune system).
  3. 3. Red blood cells can have either A or B antigens (or neither or both) on their surface. Blood plasma can also contain anti-A or anti-B antibodies.
  4. 4. If an anti-A antibody meets an A antigen, the blood clumps together. This is known as agglutination. This also happens when an anti-B antibody meets a B antigen. The antibodies are acting as agglutinins (things that make stuff clump together).
  5. This table explains which blood groups can donate blood to other blood groups:
Organs

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	Created by Rattan Bhorjee about 10 years ago