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B2 G) The Lungs
B2 G) The Lungs
Aerobic respiration happens in all cells in the body. Aerobic respiration reacts glucose with oxygen to produce carbon dioxide, water and energy. The word equation for aerobic respiration is shown below:
Cells need a continuous supply of oxygen in order to aerobically respire. Cells receive a continuous supply of oxygen from red blood cells. The red blood cells pick up oxygen in the lungs and carry it around the bloodstream. The red blood cells then deposit oxygen to cells that require oxygen.
Gas exchange takes place in the lungs and there are two types of gas exchanges taking place. One of the gas exchanges is that oxygen goes from the lungs into the bloodstream. The second gas exchange is that carbon dioxide goes from the bloodstream into the lungs. Air/ gas moves in and out of the lungs so that there is always new oxygen in the lungs to diffuse into the bloodstream, and so that the carbon dioxide that has entered the lungs from the bloodstream is taken out of the body. The process of air coming into and out of the lungs is known as ventilation.
Gas exchange takes place in the lungs and there are two types of gas exchanges taking place. One of the gas exchanges is that oxygen goes from the lungs into the bloodstream. The second gas exchange is that carbon dioxide goes from the bloodstream into the lungs. Air/ gas moves in and out of the lungs so that there is always new oxygen in the lungs to diffuse into the bloodstream, and so that the carbon dioxide that has entered the lungs from the bloodstream is taken out of the body. The process of air coming into and out of the lungs is known as ventilation.
The Structure of the Thorax
The thorax is the area between your neck and the abdomen. There are many different parts of the gas exchange system.
The thorax is the area between your neck and the abdomen. There are many different parts of the gas exchange system.
Air is taken into our body through our nose or mouth. The air then passes down the trachea (windpipe). The trachea splits into two tubes known as bronchus. There are two bronchi because we have two lungs and each bronchi takes air from the trachea to each respective lung. The two bronchi are called left bronchi and right bronchi. Each bronchi splits into smaller and smaller tubes that are known as bronchioles. The bronchioles become smaller and smaller until they eventually end up at alveoli. The alveoli are where gas exchange takes place. We will be looking at how gas exchange takes place in the alveoli later in this section. So, the route for air is through the nose or mouth, down the trachea, bronchus, bronchioles and finally the alveoli.
The lungs are inside the ribcage and above the diaphragm. The ribcage is made up of many ribs that are joined together by two sets of muscles that are called intercostal muscles. The diaphragm is a C-shaped structure of muscle and fibrous tissue. The ribcage and the diaphragm are responsible for ventilation, which they do by increasing or decreasing the volume of the lungs.
The lungs are surrounded by two pleural membranes, which ensures that the lungs are airtight. There is a cavity between the two membranes, which is known as the pleural cavity. The pleural cavity is filled with pleural fluid, which is a lubricant – the pleural fluid ensures that the lungs do not stick to the ribcage when we breathe.
The lungs are inside the ribcage and above the diaphragm. The ribcage is made up of many ribs that are joined together by two sets of muscles that are called intercostal muscles. The diaphragm is a C-shaped structure of muscle and fibrous tissue. The ribcage and the diaphragm are responsible for ventilation, which they do by increasing or decreasing the volume of the lungs.
The lungs are surrounded by two pleural membranes, which ensures that the lungs are airtight. There is a cavity between the two membranes, which is known as the pleural cavity. The pleural cavity is filled with pleural fluid, which is a lubricant – the pleural fluid ensures that the lungs do not stick to the ribcage when we breathe.
Alveoli
The alveoli are responsible for gas exchange. There are millions of alveoli in our lungs. There is a diagram of the alveoli below.
The alveoli are responsible for gas exchange. There are millions of alveoli in our lungs. There is a diagram of the alveoli below.
Blood travels very close to all of the alveoli through the capillaries. There is only a two cell gap between the alveoli and the capillary; one cell from the wall of the alveoli and the other cell from the wall of the capillary. Both of these cells allow oxygen and carbon dioxide to diffuse through them.
The lungs are part of the pulmonary circulatory system. The pulmonary system is where blood is pumped from the heart, through the lungs and back to the heart. The blood in the capillaries at the start of the alveoli is deoxygenated because it has come from the rest of the body. Deoxygenated blood is blood that contains little oxygen and lots of carbon dioxide. As the blood is deoxygenated, it means that there is a higher concentration of oxygen in the alveoli compared to the bloodstream, which results in oxygen diffusing from the alveoli into the bloodstream (remember, diffusion is the net movement of particles from high concentration to low concentration). There is a higher concentration of carbon dioxide in the bloodstream compared to the alveoli, which means that carbon dioxide diffuses from the bloodstream into the alveoli. So, oxygen diffuses from the alveoli into the bloodstream, and carbon dioxide diffuses from the bloodstream into the alveoli. This results in blood in the capillaries at the end of the alveoli being oxygenated (high in oxygen and low in carbon dioxide). This oxygenated blood travels back to the heart, where it will be pumped out on the other circulatory system around the body (the systemic system).
The alveoli are designed so that the diffusion/ exchange of gases is as efficient as possible. Here are some of the features that the alveoli have:
The alveoli are designed so that the diffusion/ exchange of gases is as efficient as possible. Here are some of the features that the alveoli have:
- A very high surface area. There are millions of alveoli in the lungs
- There are only two cells between the inside of the alveoli and the inside of the bloodstream. This means that the distance for diffusion is short which increases the rate of diffusion.
- The alveoli have a very good blood supply through the network of capillaries. This maintains the concentration differences between the inside of the alveoli and the inside of the bloodstream
- They have a moist lining so that the gases dissolve, which makes diffusion of gases faster
What Happens at Cells
Blood travels through capillaries very close to all of the cells in our body.
Blood travels through capillaries very close to all of the cells in our body.
The blood passing these cells through the capillaries is oxygenated blood (high in oxygen and low in carbon dioxide).
The concentration of oxygen is greater in the bloodstream compared to the body cells. This results in oxygen diffusing from the bloodstream into the cells.
The body cells will be undertaking respiration reactions, which produces carbon dioxide. The concentration of carbon dioxide will be greater in the body cells than in the bloodstream. This results in carbon dioxide diffusing from the body cells into the bloodstream.
So, oxygen diffuses from the bloodstream into body cells, and carbon dioxide diffuses from body cells into the bloodstream. This results in blood in the capillaries at the end of the body cells being deoxygenated blood (low in oxygen and high in carbon dioxide). This deoxygenated blood travels back to the heart.
The concentration of oxygen is greater in the bloodstream compared to the body cells. This results in oxygen diffusing from the bloodstream into the cells.
The body cells will be undertaking respiration reactions, which produces carbon dioxide. The concentration of carbon dioxide will be greater in the body cells than in the bloodstream. This results in carbon dioxide diffusing from the body cells into the bloodstream.
So, oxygen diffuses from the bloodstream into body cells, and carbon dioxide diffuses from body cells into the bloodstream. This results in blood in the capillaries at the end of the body cells being deoxygenated blood (low in oxygen and high in carbon dioxide). This deoxygenated blood travels back to the heart.