[Maximum number: 2]

Smooth muscle is a tissue composed of smooth muscle cells. The cells contain cytoplasm packed with proteins that are involved in contraction and relaxation.

(a)

Smooth muscle is present in the airways of the gas exchange system.

Explain how smooth muscle cells in the walls of the bronchioles contribute to the function of these airways.

[ 2 ]

[Maximum number: 7]

Fig. 1.1 is a photomicrograph of epithelial cells in the bronchus.

Fig. 1.1

(a)

(i)

State one feature of the cells, visible in Fig. 1.1, which indicates that these are not epithelial cells from the alveolus.

[Maximum number: 1]

Name as precisely as you can the structure described in each of the following statements.

(a)

The tissue that prevents the collapse of the trachea during inhalation.

[ 1 ]

[Maximum number: 4]

Fig. 1.1 is a scanning electron micrograph of part of the wall of the bronchus of a healthy human.

Fig. 1.1

(a)

Describe the appearance of a section through the wall of a bronchus in a person with chronic bronchitis.

[ 4 ]

[Maximum number: 1]

Fig. 2.1 is a photomicrograph showing a transverse section through a bronchus and the surrounding lung tissue.

Fig. 2.1

magnification x40

(a)

(i)

In Fig. 2.1, the area labelled R shows a section through some alveoli.

Name the tissue that lines the air spaces of the alveoli.

[ 1 ]

[Maximum number: 6]

Fig. 2.1 is a section of an alveolus and surrounding tissue.

Fig. 2.1

(a)

(i)

Describe the role of elastic fibres in the wall of the alveolus.

[ 2 ]

(ii)

With reference to Fig. 2.1, explain how alveoli are adapted for gas exchange.

[ 4 ]

[Maximum number: 2]

Tobacco smoking is known to be associated with atherosclerosis and emphysema.

(a)

Fig. 2.1 is a scan of the lungs of a person with emphysema. One common feature in the damaged areas labelled is a loss of the elastic fibres of the alveoli. Another feature is an increased number of macrophages and neutrophils.

Fig. 2.1

[ 2 ]

(i)

Suggest how the loss of the elastic fibres would cause the enlargement of the lung shown in Fig. 2.1.

[ 2 ]

[Maximum number: 2]

Fig. 3.1 shows the structure of an alveolus and surrounding structures in a mammalian lung. The lining of each alveolus is formed by two types of epithelial cell, alveolar type 1 and alveolar type 2.

Fig. 3.1

(a)

Explain how the structure of an alveolar type 1 cell is adapted to its function.

[ 2 ]

(a)

The trachea, bronchi and bronchioles in the gas exchange system require a supply of glucose and oxygen from the blood for the functioning of smooth muscle.

Outline the function of smooth muscle in the gas exchange system.

[ 2 ]