11. Gas exchange

Question 1

Alveoli

Answer 1

Tiny air sacs in the lungs that provide a large surface area to volume ratio for efficient gas exchange.

Gas exchange happens at the surface of the alveoli, allowing oxygen to diffuse from the air into blood in the capillaries, and carbon dioxide to diffuse from the blood in the capillaries into the air

Question 2

Path of air into lungs when breathing.

Answer 2

nose/mouth → larynx → trachea → bronchi → bronchioles → alveoli

Question 3

Larynx

Answer 3

Voice box

a hollow, tubular structure connected to the top of the windpipe (trachea); air passes through the larynx on its way to the lungs.

Question 4

Trachea

Answer 4

A tube made of cartilage that allows ventilation to the lungs from the mouth and nose.

Contains rings of a tough material called cartilage. These support the airway and help to keep it open.

Question 5

Bronchi

Answer 5

Bronchi is the plural form of bronchus.

The bronchi are the two large tubes that carry air from the windpipe (trachea) into the lungs and back out again.

Question 6

Bronchioles

Answer 6

The bronchi branch off into smaller and smaller passageways.

The smallest airways, called bronchioles, lead to tiny air sacs called alveoli.

Question 7

Optimising gas exchange in the alveoli

Answer 7

The gas exchange surfaces….

• Have a large surface area
• Are thin
• Have a good blood supply
• Have good ventilation with air.

Question 8

Ventilation

Answer 8

The process of inhaling and exhaling into the lungs, driven by muscles contracting.

Question 9

Thorax - Lungs

Answer 9

The thorax is the chest, the part of the body between the neck and the abdomen.

It contains the heart and lungs.

Changes in the volume of the thorax allow air to be pushed into and out of the lungs.

Question 10

Thorax - How ventilation works

Answer 10

Inhaling

• The volume of the thorax increases
• The pressure inside decreases and becomes less than the pressure outside
• Air is pushed into the lungs.

Exhaling

• The volume of the thorax decreases
• The pressure inside increases and becomes more than the pressure outside
• Air is pushed out of the lungs.

Changes in volume of thorax caused by…

• Contraction and relaxation of the diaphragm
• Contraction and relaxation of the intercostal muscles resulting in movement of the ribs

Question 11

Diaphragm

Answer 11

A large dome-shaped muscle at the base of the thorax (chest) that helps to ventilate the lungs.

If the diaphragm contracts (flattens/pulls down and away from lungs) –> increases space in lungs –> decreases pressure –> pulls air into lungs

Vice versa for exhaling (pressure increases bc diaphragm pushes up.)

Question 12

Intercostal muscles

Answer 12

Muscle tissue between the ribs in the thorax. Contraction and relaxation of these muscles allows the lungs to be ventilated.

Internal intercostal muscles - In the inside of the ribcage.

External intercostal muscles - On the outside of the rib cage.

Question 13

Internal intercostal muscles - Ventilation

Answer 13

Breathing in

• Muscles relax

Breathing out

• Muscles contract

Question 14

External intercostal muscles - Ventilation

Answer 14

Breathing in

• Muscles contract

Breathing out

• Muscles relax

Question 15

Ribcage - Ventilation

Answer 15

Breathing in

• Moves upwards and outwards

Breathing out

• Moves downwards and inwards

Question 16

Inspired air - Composition

Answer 16

Air you breathe in

(Nitrogen - 78%)
Oxygen - 21%
Carbon dioxide - 0.04%
Water vapour level - Variable (depends on the relative humidity in the air)

Question 17

Expired air - Composition

Answer 17

Air you breathe out

(Nitrogen - 78%)
Oxygen - 16%
Carbon Dioxide - 4%
Water vapour level - Always high

• Oyxgen lower than inspired air bc used in cells for aerobic respiration
• Carbon dioxide higher bc waste product that has to removed from body due to respiration
• More water vapour bc moisutre evaporates from the cells of the gas exchange surface.

Question 18

Effect of exercise on breathing

Answer 18

• Cells of body respire more during physical activity –> to provide energy needed by muscles.
• Increased rate of respiration produces more carbon dioxide as a waste product.
• Increased concentration of CO2 in blood is detected by the brain –> triggers the body to respond by increasing rate + depth of breathing to expel CO2 from body.
• Increases oxygen obtained –> increases aerobic respiration.

Question 19

Methods used to protect the breathing system.

Answer 19

Air that you breathe in contains pathogens /+ other particles

• When breathing in through the nose –> air is moistened, warmed + filtered.
• Hair inside your nose helps filter dust particles.
• Goblet cells + ciliated cells of breathing system also help protect.

Question 20

Goblet cells - Protecting breathing system

Answer 20

Goblet cells produce sticky mucus (secreted from these cells)

• This mucus lines the inside of the trachea –> pathogens + particles in inspired aire become trapped in the sticky mucus.

Question 21

Mucus - Goblet cells

Answer 21

A sticky substance secreted by specialised cells that helps to trap particles/pathogens.

Question 22

Ciliated cells

Answer 22

Line the surface of the nose, trachea, bronchi + bronchioles

Specialised cells with fine structures called cilia.

• Movement of cilia sweeps mucus out of the breathing system to the throat (where it is then swallowed)
• Carries pathogens / particles away from the breathing system
• Smoking damages cilia –> mucus less efficiently swept up.

Question 23

Inspired air vs expired air

Answer 23

Inspired air

Nitrogen - 78%
Oxygen - 21%
Carbon dioxide - 0.04%

Expired air

Nitrogen - 78%
Oxygen - 16%
Carbon Dioxide - 4%