Structure of cardiovascular system
The heart- The heart is a key figure in the cardiovascular system. It is responsible for pumping the blood around the body non-stop, all day long. It will never stop beating until it dies. Because of this function, the heart is a cardiac muscle, which means that it will never tier or fatigue. It is also split into two half’s. The left and right side of the heart are separated because they have separate functions. The right side of the heart is responsible for pumping blood to the lungs and back. This means it is at the centre of the pulmonary system. However, the left side of the heart is responsible for pumping the blood around the body. Because of this function the muscle of the right side of the heart is much bigger than the muscle on the left side. This is because the systemic system requires a much stronger pump to get the blood all the way around the body. The heart also has several valves, such as the aortic valve, the pulmonary valve, tricuspid and bicuspid valves. These valves stop the blood from flowing backward and keep the blood in the correct chambers until it is pumped forwards.
Blood vessels- In order to travel around the body, blood moves through a series of blood vessels. On its way out of the heart, the blood will travel through arteries. The artery is made up of a strong outer layer, a thick layer of smooth muscle in the middle and a thin inner layer made of endothelium.
Arteries are responsible for carrying blood around the body at a high pressure. Because of this function, arteries are equipped with a strong outer layer and a thick layer of muscle. This is so that it can stand the high pressure of the blood travelling through it.
As the blood travels along the arteries, it eventually makes its way to arterioles. These are made up entirely the same as arteries, but are much smaller.
Once the blood has travelled through the arterioles, it makes its way to the capillaries. Capillaries are very small blood vessels, which allow the blood to exchange oxygen, food, etc with carbon dioxide, water and waste, etc. Because of this function they have a very thin wall which allows only one red blood cell through at a time. They are also very narrow and small so that they can surround the body cells and allow the diffusion of gasses and nutrients.
Now the blood is deoxygenated, it moves into venuoles. These are similar to veins, only smaller. Veins take the blood back to the heart. They do this at a low pressure unlike arteries. They are very similar to arteries and arterioles, but the have a much thinner layer of smooth muscle. This is because they don’t have to withstand a high pressure of blood flow. Because the blood travels at a low pressure, veins have valves to ensure that the blood only flows in one direction.
Blood- An average adult male will have about 5 litres of blood in his body and is made in the marrow cavity of long bones. Blood is made up of four main things.
1. Plasma- This gives the blood its liquid structure. It consists mainly of water and is yellow in colour. 55% of the bloods volume is plasma. Dissolved into the plasma, there are the following substances:
- Oxygen and carbon dioxide
- Salts
- Glucose
- Fatty acids
- Waste products
2. Red blood cells- These are responsible for transporting oxygen around the body. Each cell contains a protein called haemoglobin which picks up oxygen and carries it to the relevant places in the body. The red blood cell is a biconcave shape and contains no nucleus. This is so that a maximum amount of oxygen can be stored in the cell.
3. White blood cells- These cells contain antibodies which fight against infection and help prevent illness.
4. Platelets- If we unfortunately cut ourselves, platelets in the blood cause a clot at the wound and stop it from bleeding. It does this by forming a scab.
Structure of respiratory system
The respiratory system is an important factor in our lives. It is responsible for the inspiration and expiration of air. As we breathe the respiratory system is hard at work each time we breathe. There are certain parts of the respiratory system which are responsible for different things.
The lungs- The lungs are at the centre of the respiratory system. They are found inside the ribcage were they hang like two balloons. The lungs are made of a flexible material so that they fit as much air in them as possible. Because we continuously breathe, the lungs are lubricated by a set of membranes called the pleura, which are arranged like a double skinned bag. The visceral pleura surrounds the outer surface of the lungs and the parietal pleura create a lining on the inside of the chest cavity. In between these two pleura is a lubricating fluid which lubricates their contact as the lungs continually contract and expand.
As we inspire, the air travels along a series of tubes before reaching its final destination. Firstly the air enters through the mouth and/or the nose. As it passes through the nose it is filtered by the nasal hairs and warmed by mucus. It then passes through to the pharynx and then through the epiglottis, to the larynx. The air then passes into a tubular passage way called the trachea. The trachea is held open by rings of cartilage called hyaline cartilage. The trachea then divides into two other tubes called bronchi. This is a large tube which passes into the lung. These bronchus then further divide into smaller tubes called bronchioles, which are made of smooth muscle. Finally, the air comes to the alveoli, which look like micro-sized bundles of grapes. This is where the gas exchange takes place.
How we breathe
To enable us to breathe we have two different muscle groups. The diaphragm is a dome-shaped muscle which sits underneath the lungs. When it contracts, it changes to a flat shape and therefore, increases the area of the chest cavity. This means that the air pressure inside the cavity is less than outside, and so air is forced into the lungs. The intercostals also aid in this inspiration. The external intercostal muscles contract and pull the ribs upwards, thus increasing the area inside the chest cavity.
When breathing out, the diaphragm relaxes and returns to its usual dome shape. This means that the air pressure inside is more than outside, and so the air is forced out of the lungs. The internal intercostal muscles contract to pull the ribs downwards which, also helps to force air out of the lungs.
The diaphragm is responsible for 75% of the breathing mechanism, meaning the intercostals are only used 25% of the time. However, in sport, we use the intercostal muscles much more. For example, in long distance running, we must consume vast amounts of oxygen to enable our muscles to keep working. Therefore, the intercostals are used more frequently.
