(g) Gas Exchange (Human)

Question 1

Describe the structure of the Ribs?

Answer 1

Bones that protect and ventilate the lungs.

Question 2

Describe the structure and function of the Intercostal muscles?

Answer 2

They are a group of muscles found between the ribs that are involved in breathing by changing the size of the thorax (moving ribs).

Question 3

Describe the structure and function of the Diaphragm?

Answer 3

Sheet of muscles which is doomed.

It helps make breathing movements and separates the thorax from the abdomen.

Question 4

Describe the structure and function of the Trachea?

Answer 4

Tube with incomplete rings of cartilage carries air to lungs.
It is lined with cells making mucus, and cells with cilia to move the mucus away.

Question 5

Describe the function of the Bronchi?

Answer 5

It carries air to lungs.

Question 6

Describe the function of the Bronchioles?

Answer 6

Bronchi splits to smaller tubes called bronchioles, they carry air to alveoli.

Question 7

Describe the function of the Alveoli?

Answer 7

Tiny air sacs with capillaries around them, they are adapted for gas exchange.

Question 8

Describe the structure and function of the Pleural muscles?

Answer 8

Thin moist membranes forming an airtight seal around the lungs and separating inside of thorax from lungs. It also covers the lungs, reduces friction and keeps the lung moist.

Question 9

What is the process of air entering the lungs?

Answer 9

Air gets drawn in the trachea.
The trachea splits into 2 tubes called bronchi, each one going into a lung.
The bronchi then splits into small tubes called bronchioles, and at the end of the bronchioles, there are little air sacs known as alveoli.

Question 10

What does ventilation require?

Answer 10

Ventilation is the moving of air in and out of the lungs, and it requires a change in air pressure.
Air moves from a place where the pressure is high to a place where the pressure is lower.

Question 11

What happens during inhalation?

Answer 11

When we need to increase the rate of gas exchange (e.g during strenuous activity), the intercostal muscles contract, making the ribs to move upwards and outwards. Then, the diaphragm contracts and flattens. These 2 opening out movements increase the volume of the thorax and draw breaths to the lungs.
As the volume of the thorax increases, the pressure inside the lungs decreases.
Once it drops below the air pressure outside the lungs, air will be forced in.

Question 12

What happens during exhalation?

Answer 12

The diaphragm relaxes and becomes dome-shaped;
The intercostal muscles contract;
The volume of the thorax decreases and the pressure inside the thorax increases, and the air will be forced out.

Question 13

What are the components of the air breathing in?

Answer 13

Oxygen: 21%

Carbon Dioxide: 0.04%

Question 14

What are the components of the air breathing out?

Answer 14

Oxygen: 16%

Carbon Dioxide: 4%

Question 15

What are the general roles of the alveoli?

Answer 15

The oxygen needs to get into the bloodstream, and this is done through gaseous exchange, which happens in the alveoli.
Waste carbon dioxide diffuses out of the bloodstream, into the alveoli and get ready to be breathed out. The oxygen displaces the CO2 and diffuses into the bloodstream.

Question 16

What are the adaptations of the alveoli? (5 points)

Answer 16

1. Large surface area (about 90 m2) to allow faster diffusion of gases across the surface.
2. Thin walls (the air and the blood are only separated by 2 layers of cells) to ensure diffusion distances remain short.
3. Moist surface allows the gases to dissolve and diffuse across easily.
4. Good blood supply to maintain a high concentration gradient so diffusion occurs faster.
5. Permeable to gases.

Question 17

What 3 issues can be caused by smkoing?

Answer 17

1. Lung disease
2. Heart disease
3. Increased risks of several different types of cancer

Question 18

What Chemicals are present in cigarettes?

Answer 18

1) Tar – a carcinogen (a substance that causes cancer)
2) Nicotine – a highly addictive substance which also narrows blood vessels, causing the blood pressure to increase.
3) Carbon monoxide – reduces the oxygen carrying capacity of the blood.

Question 19

What effects does smkong have on air passages?

Answer 19

It causes a build up of mucus.
Tar destroys the cilia (which carry dust and microbes trapped by mucus away from the lungs), causing the buildup of mucus and potentially leading to bronchitis as the lining of the bronchi become irritated.

Question 20

What effects does smkong have on alveoli?

Answer 20

Tar contributes to the breakdown of the walls of the alveoli, causing them to merge together. This creates an insufficient surface area to volume ratio, allowing less gas exchange. This also reduces the efficiency of gas exchange, causing emphysema where less oxygen is carried in blood (making exercise difficult).

Question 21

How can smoking lead to lung cancer?

Answer 21

Tobacco smoke contains many carcinogens, including tar.

Question 22

What effects does smoking have on the circulatory system?

Answer 22

Nicotine narrows blood vessels, and increases blood pressure. Narrow blood vessels are more likely to become clogged with fat, including cholesterol.
This causes coronary heart disease, when heart muscle cells do not get sufficient oxygen and so less aerobic respiration takes place. Therefore, the cells respire anaerobically, producing lactic acid which cannot be removed (due to lack of blood supply), leading to a low pH environment and causes enzymes to denature and eventually heart muscle cells will die. This mght cause a heart attack.
Carbon monoxide binds irreversibly to haemoglobin, reducing the capacity of blood to carry oxygen. This puts more strain on the circulatory system and also increases the risk of coronary heart disease and strokes.