Respiratory System

Question 1

Describe the serous membrane of the lungs

Answer 1

lubricating fluid between the two layers, which envelope the lungs

Visceral; inner
Parietal: outer

Question 2

What is pneumothorax?

Answer 2

Pleural cavity filled with air

Question 3

What is haemothorax?

Answer 3

Pleural cavity filled with blood

Question 4

What is empyema?

Answer 4

Pleural cavity filled with pus

Question 5

What is pleural effusion?

Answer 5

A watery transudate or exudate filling pleural cavity

Question 6

How can fluid be drained from the pleural cavity

Answer 6

Fluid can be drained from the pleural cavity by inserting a wide-bore needle through an intercostal space (usually the 7th posteriorly). Nowadays done under ultrasound guidance. The needle is inserted a fraction above the superior border of the lower rib, thus avoiding the intercostal nerves and vessels, which run along the inferior border of each rib.
Below the 7th intercostal space there is a danger of penetrating the diaphragm.

Question 7

How can cancer of the lung cause paralysis of the diaphragm?

Answer 7

Tumours of the lung can cause a paralysis of one side of the diaphragm, if tumour impinges on the left or right phrenic nerve.

Question 8

How can cancer of the lung lead to wasting in the lower arm?

Answer 8

Cancer in the apex of the lung can impinge on the brachial plexus, causing wasting of muscles in the lower arm.

Question 9

How can a hoarse voice result from cancer of the lung?

Answer 9

Cancer of the lung can result in a hoarse voice as a result of impingement on the left recurrent laryngeal nerve, which loops under the aorta.

Question 10

What is the conducting portion of the respiratory tract?

Answer 10

Conducting portion of respiratory tract = nasal cavity to bronchioles. (extrapulmonary)

Question 11

What is the respiratory portion of the respiratory tract?

Answer 11

Respiratory portion of respiratory tract = respiratory bronchioles to alveoli. (intrapulmonary)

Question 12

Describe the epithelial changes as you move down the respiratory tract

Answer 12

Pseudostratified epithelium, with cilia and goblet cells, lines the airways from the nasal cavity to the largest bronchioles.

Simple columnar epithelium with cilia and Clara cells but no goblet cells in the terminal bronchioles

Simple cuboidal epithelium with Clara cells and a few sparsely scattered cilia in the respiratory bronchioles and alveolar ducts

Simple squamous/type 1 (+ septal/type 2) cells in the alveoli

Question 13

How is air flow alternated in the nasal region?

Answer 13

Venous plexuses swell every 20-30 minutes, alternating air flow from side to side, preventing overdrying. Arterial blood flow warms inspired air.

Question 14

How does the olfactory region differ from the non-olfactory region in the nasal cavity?

Answer 14

Pseudostratified epithelium:

• particularly tall in olfactory region
• no mucus-secreting goblet cells
• cilia non-motile
• contains olfactory cells (bipolar neurons – one dendrite extends to the surface to form a swelling from which non motile cilia extend parallel with the surface. These
cilia increase surface area and respond to odours).
• Serous glands (Bowman’s glands) flush odourants from the epithelial surface.

Question 15

What is in the secretions of the trachea and bronchi epithelia?

Answer 15

SECRETIONS from the epithelium and submucosal glands of the trachea and bronchi contain mucins,
water, serum proteins, lysozyme (destroys bacteria), antiproteases (inactivate bacterial enzymes). Lymphocytes contribute immunoglobulins (esp. IgA).

Question 16

What happens in COPD, in terms of histological changes

Answer 16

In chronic obstructive pulmonary disease (COPD) there is goblet cell hyperplasia, a smaller proportion of ciliated cells, and hypertrophy of the submucous glands……. (so, more mucus and fewer cilia to move the mucus).

Question 17

How does the histology of secondary and tertiary bronchi differ to primary?

Answer 17

Histology similar to primary bronchi except cartilages arranged as irregular crescent plates or islands, rather than rings.

Question 18

How does a bronchiole stay open?

Answer 18

It is 1 mm or less in diameter and has no subepithelial cartilage or glands. Surrounding alveoli keep the lumen open.

Question 19

How does asthma affect bronchioles?

Answer 19

Absence of cartilage in walls of bronchioles can be problematic because it allows these air passages to constrict and almost close down when smooth muscle contraction becomes excessive.

Such bronchoconstriction can become excessive in asthma and cause more difficulty with expiration than inspiration (during expiration the bronchial walls are no longer held open by the surrounding alveoli).

Question 20

What are clara cells and what do they secrete?

Answer 20

Clara cells secrete a surfactant lipoprotein, which prevents the walls sticking together during expiration.

Clara cells also secrete abundant Clara cell protein (CC16):

• a measurable marker in bronchoalveolar lavage fluid (if lowered then lung damage).
• a measurable marker in serum (if raised then leakage across air-blood barrier).

Question 21

Why aren’t goblet cells present in terminal bronchioles?

Answer 21

Absence of goblet cells in these very narrow airways is important to prevent individuals from ‘drowning’ in their own mucus.

Question 22

What is the difference between type 1 alveolar cells and type 2 alveolar cells?

Answer 22

Type I cells (squamous) cover 90% of surface area and permit gas exchange with capillaries.

Type II cells (cuboidal) cover 10% of surface area and produce surfactant.

Numerous macrophages line alveolar surface (phagocytose particles).

Gas exchange occurs across blood-air barrier.

Question 23

Describe the pathophysiology of pneumonia

Answer 23

Destruction of alveolar walls and permanent enlargement of air spaces which can result from smoking or alpha 1-antitrypsin deficiency. Alveolar walls normally hold bronchioles open, allowing air to leave the lungs on exhalation. When these walls are damaged, bronchioles collapse, making it difficult for the lungs to empty. Air becomes trapped in the alveoli. Hallmark sign: pursed-lip breathing.

Question 24

Describe the pathophysiology of emphysema

Answer 24

Inflammation of the lung caused by bacteria. The lung consolidates as the alveoli fill with inflammatory cells. Most common causative bacterium is Streptococcus pneumoniae. Others are: Haemophilus influenzae Staphylococcus aureus Legionella pneumophila & Mycoplasma pneumoniae.

Question 25

What is the purpose of the lubricating fluid in the pleural cavity?

Answer 25

• allows pleura to slide easily during breathing

- lung contains a lot of elastin, pleural fluid provides surface tension to prevent lungs from recoiling

Question 26

Describe pressure changes within the pleura on inhalation and exhalation

Answer 26

The area between the pleurae is called the pleural space (sometimes referred to as “potential space”). Normally, vacuum (negative pressure) in the pleural space keeps the two pleurae together and allows the lung to expand and contract

• During inspiration, the intrapleural pressure is approximately -8cmH20
• During exhalation, intrapleural pressure is approximately -4cmH20

This prevents lung collapse as intrapleural pressure is always lower than intrapulmonary pressure

Question 27

What is the role of alveolar surfactant?

Answer 27

Surfactant molecules move apart on inspiration and move closer on expiration. They reduce surface tension when they are concentrated and allow lungs to inflate more easily.