The scanning electron micrograph shows the inner surface of a human trachea.
What is the identity of the part of the electron micrograph labelled T?
Options
A ciliated epithelial cell
B goblet cell
C mucus
D squamous epithelial cell
Which rows correctly summarise the typical distribution of cartilage and smooth muscle within different parts of the gas exchange system of humans?
1 bronchi
2 bronchioles
3 trachea
Options
| cartilage | smooth muscle | |
|---|---|---|
| A | 1, 2 and 3 | |
| B | 1 and 2 only | |
| C | 1 and 3 only | |
| D | 2 and 3 only |
key
✓ = present
✗ = not present
(Note: The table in the PDF shows ticks and crosses for each row: 1 has ✓ for both, 2 has ✗ for both, 3 has ✓ for both. The options A-D refer to which rows are correct.)
A molecule of oxygen diffuses from the air in an alveolus to haemoglobin in a red blood cell.
Assuming that the molecule crosses cellular layers by passing through cells, rather than between cells, what is the minimum number of phospholipid layers that the molecule of oxygen must pass through?
Options
A 5
B 6
C 8
D 10
How many times must an oxygen molecule pass through a cell surface membrane to get from the air in the alveolus to the haemoglobin in a red blood cell?
(Assume there are no pores between the cells the oxygen molecule must pass through.)
Options
A 2
B 3
C 4
D 5
Asthma can affect children and adults. The air passages become narrower, severely restricting the flow of air into the lungs.
Salbutamol is a drug that widens the air passages to relieve the symptoms of asthma.
How does salbutamol relieve the symptoms of asthma?
Options
A It decreases mucus secretions in the terminal bronchioles.
B It decreases the surface area of the alveoli.
C It causes recoil of elastic tissue in the bronchioles.
D It relaxes smooth muscle in the bronchi and bronchioles.
The photomicrograph shows the transverse section of part of the trachea.
Which letter represents a tissue that can contract and relax to adjust the diameter of the airways?
Options
A A
B B
C C
D D
Which row shows the tissues that are present in the wall of the trachea and the wall of the bronchus?
| cartilage | ciliated epithelium | smooth muscle | |
|---|---|---|---|
| A | ✓ | ✓ | ✓ |
| B | ✓ | ✓ | ✗ |
| C | ✓ | ✗ | ✓ |
| D | ✗ | ✓ | ✗ |
key
✓ = present
✗ = not present
Options
A row A
B row B
C row C
D row D
Which factors maintain the diffusion gradient for carbon dioxide at the surface of the alveoli?
1 blood flow around the alveoli
2 breathing movement exchanging air in the lungs
3 thin epithelial lining of the alveoli
Options
A 1 and 2
B 1 and 3
C 1 only
D 2 and 3
The photomicrograph shows a transverse section of part of the human gas exchange system.
Which row shows the label and function of smooth muscle?
Options
| label | function | |
|---|---|---|
| A | P | regulates air flow towards the gas exchange surfaces |
| B | Q | pumps air towards the gas exchange surfaces |
| C | P | pumps air towards the gas exchange surfaces |
| D | Q | regulates air flow towards the gas exchange surfaces |
Which feature of the human gas exchange system helps to maintain a steep diffusion gradient?
Options
A A large number of alveoli are present in each lung.
B Alveoli walls contain elastic fibres allowing expansion.
C The air brought into the alveoli has a high concentration of oxygen.
D The endothelium of the capillary wall is made of flattened cells.