Lungs

Question 1

Diffusion distance and SA of lungs

Answer 1

have short diffusion distance and large SA

Question 2

Structure of lungs

Answer 2

Trachea- tube like structure, carries air from mouth to lungs
Bronchi- trachea splits into two bronchi as it enters lungs, allows air to travel to left/right lung
Bronchioles- bronchi further divide into smaller branches, supply alveoli with air

Question 3

Alveoli adaptions

Answer 3

• large SA to maintain efficient diffusion rate
• rich blood supply to maintain large conc. gradient
• squamous epithelium is one cell thick so thin diffusion distance

Question 4

Pathway of oxygen

Answer 4

• O2 enters trachea into bronchus, bronchioles and alveoli
• alveoli has rich blood supply so large conc. gradient
• squamous epithelium is one cell thick so short diffusion distance
• diffuses through endothelium of capillary
• binds with haemoglobin
• pulmonary arteriole carries deoxygenated blood to alveoli
• pulmonary venule carries oxygenated blood to heart

Question 5

How are gasses in alveoli separated from blood?

Answer 5

gases in alveolar air spaces separated by alveolar squamous epithelium and the endothelial wall of capillary

Question 6

Ventilation

Answer 6

• breathing is a result of difference in pressure between lungs and air outside body
• pressure inside lungs changed by changes in lung volume
  -maintains a conc. gradient (gasses don’t reach equilibrium)

Question 7

Inhalation

Answer 7

1. external intercostal muscles contract, pulling rib cage up and out
2. diaphragm contracts and pulls down
3. thoracic cavity volume increases
4. pressure in lungs lower than atmospheric pressure
5. air moves into lungs down pressure gradient

Question 8

Exhalation

Answer 8

1. external intercostal muscles relax
2. diaphragm relaxes and moves up
3. thoracic cavity volume decreases
4. pressure in lungs greater than atmospheric pressure
5. air moves out of lungs down pressure gradient

Question 9

Describe the gross structure of the human gas exchange system and how we breathe in and out.

Answer 9

1. Named structures – trachea, bronchi, bronchioles, alveoli;
2. Above structures named in correct order
3. Breathing in – diaphragm contracts and external intercostal muscles contract;
4. (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in);
5. Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
6. (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);

Question 10

Describe how the movement of the diaphragm leads to air movement into the lungs

Answer 10

1. Diaphragm contracts and flattens.
2. Volume of lungs increases.
3. Pressure inside the lungs is lower than atmospheric pressure.
4. Air moves into the lungs.

Question 11

Describe and explain the mechanism that causes forced expiration.

Answer 11

1. Contraction of internal intercostal muscles;
2. Relaxation of diaphragm muscles / of external intercostal muscles;
3. Causes decrease in volume of chest / thoracic cavity;
4. Air pushed down pressure gradient.

Question 12

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them

Answer 12

*Many alveoli provide a large surface area
*Many capillaries provide a large surface area so fast diffusion;
*Flattened/ squamous epithelium (So) short diffusion distance so fast diffusion
*Ventilation maintains a concentration gradient so fast diffusion;

Question 13

Describe the pathway taken by an oxygen molecule from an alveolus to the blood

Answer 13

1. (Across) alveolar epithelium;
2. Endothelium of capillary;

Question 14

Explain why death of alveolar epithelium cells reduces gas exchange in human lungs.

Answer 14

1. Reduced surface area;
2. Increased distance for diffusion;
3. Reduced rate of gas exchange;

Question 15

Diffusion of gasses

Answer 15

• deoxygenated blood from pulmonary artery has low O2 conc. and high CO2 conc.
• as blood reaches capillaries surrounding alveoli, O2 diffuses into blood across squamous epithelial and endothelial wall moving from higher to lower O2 conc.

Question 16

Pulmonary ventilation equation

Answer 16

Pulmonary ventilation rate(dm^3min^-1)

tidal volume (dm^3) x breathing rate (min^-1)