Organisation: The Cardiovascular & Respiratory System (AQA GCSE Biology)
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- FrontThe Lungs
True or False?
The lungs allow gas exchange in humans.
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True or False?
The lungs allow gas exchange in humans.
True.
The lungs are the gas exchange surface in humans.
What is the function of the trachea?
The trachea, or windpipe, connects the nose and mouth to the lungs/bronchi.
What are the alveoli?
Alveoli are tiny air sacs surrounded by a network of capillaries, serving as the site of gas exchange between the air and the blood.
Describe the role of the bronchi.
The bronchi (singular bronchus) branch off the trachea and carry air into the right and left lungs. They contain mucus to trap dust and pathogens.
Which process takes place at the alveoli?
The process that takes place in the alveoli is gas exchange.
True or False?
Alveoli and surrounding capillaries are surrounded by multiple layers of cells to minimise diffusion distance.
False.
Alveoli and surrounding capillaries are surrounded by single layers of cells to minimise diffusion distance.
What are the features of alveoli that make them an efficient exchange surface?
Alveoli are an efficient gas exchange surface because:
They have a large total surface area
They provide a short diffusion distance
They have a good blood supply and good ventilation, maintaining a steep concentration gradient
They are lined with a layer of moisture in which gases can dissolved
How is a steep concentration gradient for both oxygen and carbon dioxide maintained in the alveoli?
A steep concentration gradient for both oxygen and carbon dioxide is maintained in the alveoli as follows:
Good ventilation means that a high concentration of oxygen and a low concentration of carbon dioxide is maintained inside the alveoli
A good blood supply ensures that blood is constantly flowing; this means that the blood immediately next to each alveolus is always low in oxygen and high in carbon dioxide
How does a dense capillary network directly surrounding the alveoli help to increase the rate of gas exchange?
A dense network of capillaries directly surrounding the alveoli helps to maximise the rate of gas exchange by providing
a short diffusion distance between the alveoli and the red blood cells
a large surface area over which gas exchange can occur
Why is a faster rate of gas exchange important during exercise?
A faster rate of gas exchange is important during exercise as a greater amount of oxygen is required for a higher rate of respiration in muscle tissues.
There is also a higher quantity of carbon dioxide being produced which needs excreting from the body via the lungs.
True or False?
The blood entering the capillaries in the lungs has a high concentration of carbon dioxide.
True.
The blood entering the lungs has returned from the body where oxygen has been exchanged for the carbon dioxide produced in respiration. The carbon dioxide is then carried to the lungs where it is exchanged for oxygen again.
What is the function of the heart?
The heart is an organ that pumps oxygenated blood from the lungs to the rest of the body and deoxygenated blood from the body to the lungs.
Describe the pathway of deoxygenated blood through the heart from the body.
Deoxygenated blood from the body:
Enters the right atrium through the vena cava
Flows through the atrio-ventricular valve into the right ventricle
Is pumped through the pulmonary semilunar valve into the pulmonary artery
To the lungs for oxygenation
Why does the left ventricle have a thicker muscle wall than the right ventricle?
The left ventricle has a thicker muscle wall to pump oxygenated blood at high pressure throughout the body, while the right ventricle pumps deoxygenated blood at lower pressure to the lungs.
What role do valves play in the heart?
Valves in the heart prevent the backflow of blood, ensuring that blood flows in only one direction through the heart chambers and vessels.
How does blood return from the lungs to the heart?
Oxygenated blood returns from the lungs to the heart via the pulmonary veins.
What supplies the cardiac muscle tissue of the heart with oxygenated blood?
The coronary arteries supply the cardiac muscle tissue of the heart with oxygenated blood, ensuring it receives a constant supply of oxygen and glucose for aerobic respiration to release energy for muscle contraction.
How does the heart prevent damage to the capillaries in the lungs?
The heart maintains low pressure in the pulmonary artery, preventing damage to the capillaries in the lungs during blood circulation. The muscle in the right hand side of the heart is thinner and weaker to allow this.
True or False?
Deoxygenated blood enters the left side of the heart from the body.
False.
Deoxygenated blood enters the right side of the heart from the body.
True or False?
The right ventricle muscle wall is thinner than the left ventricle muscle wall.
True.
The right ventricle muscle wall is thinner than the left ventricle muscle wall.
Which vein is the only vein in the body to carry oxygenated blood?
The pulmonary vein is the only vein to carry oxygenated blood, returning blood to the heart after gas exchange has taken place.
What are the three main types of blood vessel?
The three main types of blood vessel are arteries, veins, and capillaries.
What is the function of arteries?
Arteries carry blood at high pressure away from the heart.
How are the walls of arteries adapted to their function?
Arteries have thick muscular walls containing elastic fibres to withstand high blood pressure and maintain it as the blood recoils. They also have a narrow lumen to help maintain high blood pressure.
What is the function of veins?
Veins carry blood at low pressure towards the heart.
How are the walls of veins adapted to their function?
Veins have thin walls and a large lumen to reduce resistance to blood flow under low pressure. They also contain valves to prevent backflow of blood.
What is the function of valves?
Valves prevent the back-flow of blood in the veins where blood travels under low-pressure.
What are the key features of capillaries?
Capillaries carry blood at low pressure within tissues, have walls that are one cell thick, and allow substances to easily diffuse in and out through their 'leaky' walls.
1230 ml of blood flows through a blood vessel in 120 seconds.
What is the rate of blood flow?
The rate of blood flow in this example is:
1230 ÷ 2 = 615 ml minute-1
OR
1230 ÷ 120 = 10.25 ml sec-1
True or False?
Arteries have valves to prevent backflow.
False.
Veins have valves to prevent backflow, the pressure of the blood in the arteries is enough to drive it forwards in one direction.
Identify the blood vessel shown below:
This blood vessel is an artery. It is identified by a circular shape, a thick later of muscle and elastic tissue and a small lumen.