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The skeleton, bones and joints

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The skeleton has five main functions: protection, shape, support, movement and blood production.
The vertebral column is composed of vertebrae each of which are separated by discs.
There are five main sections to the vertebral column: the cervical, thoracic, lumbar, scaral and coccyx vertebrae.
Joints are where two bones meet. There are three main types: fibrous joints, cartilaginous joints and synovial joints.
Joints are made up of five main components: cartilage, tendon, ligament, synovial fluid and the synovial membrane.
Bones are formed from cartilage in a process known as ossification.
With age bones lose their density and if very extreme it’s known as osteoporosis.
There are four main groups of bone: long, short, flat and irregular.

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When you inhale air enters through the nose or mouth and moves through the trachea into the bronchi. In the lungs the bronchi split up into bronchioles which end in alveoli where gaseous exchange takes place.
When you inhale the intercostal muscles contract which makes the ribcage expand.The diaphragm contracts as well and pulls downwards which makes it flatter. This causes the volume in the chest to increase.When the pressure in the thorax decreases, air is pulled into the lungs.
When you exhale the intercostal muscles relax which makes the ribcage drop in and down.The diaphragm also relaxes and moves upwards. This causes the chest volume to decrease. The increase in pressure in the thorax squeezes the air out of the lungs.
Aerobic respiration requires oxygen and glucose is completely broken down to release energy: glucose + oxygen ? energy + water + carbon dioxide
When not enough oxygen can reach the muscles (for example during heavy exercise) the muscle cells need to respire anaerobically.
In anaerobic respiration no oxygen is required, not as much energy is made because the glucose isn’t completely broken down, and lactic acid is produced: glucose ? energy + lactic acid
Exhaled air contains less oxygen then inhaled air because oxygen is used by the body for respiration and it contains more carbon dioxide because this is expelled by the body as a waste product.

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The circulatory system is made up of the heart, blood vessels and blood.
It’s called a double circulatory system because it’s composed of two circuits: the pulmonary circuit which pumps deoxygenated blood to the lungs, and the systemic circuit which pumps oxygenated blood around the rest of the body.
the heart is composed of two sides separated by the septum.
Cardiac output = heart rate x stroke volume
The heart is made up of four chambers: two atria and two ventricles.
The heart also contains valves to prevent blood from flowing in the wrong direction.
Arteries carry oxygenated blood. They have think walls and thin lumen because they carry the blood at high pressures.
Veins carry deoxygenated blood. They have thinner walls, larger lumens and valves because they carry the blood at low pressure.
Capillaries allow gases to be exchanged. Their walls are only one cell thick.
Blood is composed of plasma, red blood cells, white blood cells and platelets.
Blood is important during exercise for oxygen and nutrient transport, waste removal, acidic balance and temperature regulation.