2 2 organisation the cardiovascular and respiratory system

True. The lungs are the gas exchange surface in humans.

The trachea, or windpipe, connects the nose and mouth to the lungs/bronchi.

Alveoli are tiny air sacs surrounded by a network of capillaries, serving as the site of gas exchange between the air and the blood.

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.

The process that takes place in the alveoli is gas exchange.

False. Alveoli and surrounding capillaries are surrounded by single layers of cells to minimise diffusion distance.

Alveoli are an efficient gas exchange surface because:

A steep concentration gradient for both oxygen and carbon dioxide is maintained in the alveoli as follows:

A dense network of capillaries directly surrounding the alveoli helps to maximise the rate of gas exchange by providing

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. 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.

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.

Deoxygenated blood from the body:

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.

Valves in the heart prevent the backflow of blood, ensuring that blood flows in only one direction through the heart chambers and vessels.

Oxygenated blood returns from the lungs to the heart via the pulmonary veins.

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.

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.

False. Deoxygenated blood enters the right side of the heart from the body.

True. The right ventricle muscle wall is thinner than the left ventricle muscle wall.

The pulmonary vein is the only vein to carry oxygenated blood, returning blood to the heart after gas exchange has taken place.

The three main types of blood vessel are arteries, veins, and capillaries.

Arteries carry blood at high pressure away from the heart.

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.

Veins carry blood at low pressure towards the heart.

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.

Valves prevent the back-flow of blood in the veins where blood travels under low-pressure.

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.

The rate of blood flow in this example is: 1230 ÷ 2 = 615 ml minute-1 OR 1230 ÷ 120 = 10.25 ml sec-1

False. Veins have valves to prevent backflow, the pressure of the blood in the arteries is enough to drive it forwards in one direction.

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.