Functional histology of the respiratory system

Question 1

What are the 4 stages of mechanical respiration?

Answer 1

inspiration
gas conduction
gas transfer
exhalation

Question 2

Where does gas transfer occur?

Answer 2

alveolar spaces

Question 3

What is the conduction zone?

Answer 3

consists of all of the structures that provide passageways for air to travel into and out of the lungs: the nasal cavity, pharynx, trachea, bronchi, and most bronchioles

Question 4

Function of the conducting zone?

Answer 4

passage of air from environment to lungs
airway protection
air humidification + warming
smell
speech

Question 5

What is the shape of the trachea?

Answer 5

C-shaped to allow swallowing
no cartilage at junction with oesophagus so oesophagus can expand

Question 6

What 3 types of protection are present in the conducting zone?

Answer 6

mechanical (cellular)
- mucociliary escalator
- physical environment between external environment and tissue

immunological
- identification and removal of pathogens

mechanical (anatomical)
- reflex protection

Question 7

What happens to the number of mucus-secreting cells in response to irritation?

Answer 7

number increases
more mucus secreted

Question 8

2 types of cells that secrete mucus

Answer 8

goblet cells (within epithelium)
seromucinous glands (within submucosa)

Question 9

Is cilia action dependent on nervous control?

Answer 9

no, cilia action is independent of nervous control and can persist several hours after death

Question 10

What is the difference between the mucus secreted by goblet cells and seromucinous glands?

Answer 10

serous cells produce more watery, thin mucus

goblet cells and mucus cells produce thicker mucus

Question 11

Roughly how many cilia are there per cell and how fast do they beat?

Answer 11

200-300 cilia/cell
beat 20x/second

Question 12

What do the cilia beat towards?

Answer 12

nasopharynx

Question 13

What immunological protection is there in the airway?

Answer 13

MALT (mucosa-associated lymphoid tissue)

Nasopharynx:
- Waldeyer’s ring
- dense lymphoid tissue

Bronchial epithelial cell + serous cell secretions
- lysozymes, lactoferrin, antiprotease, IgA, epithelial peroxidase

Question 14

What refexes are there in the airway?

Answer 14

Cough reflex
Gag reflex
Swallow reflex

Question 15

Describe the cough reflex

Answer 15

pulmonary irritant receptors
mechanical and chemical stimuli
vagus nerve
carina = specialised nervous tissue
stimulated by foreign body = violent coughing

Question 16

What does the swallow reflex involve?

Answer 16

enables the epiglottis to cover the larynx to prevent aspiration

Question 17

Describe the gag reflex

Answer 17

(pharyngeal reflex or laryngeal spasm)
reflex contraction of the back of the throat
prevents foreign bodies entering the upper airways
stimulus = touch from back of throat, tonsils, uvula, roof of mouth of base of tongue

Question 18

How do we smell odours?

Answer 18

odours dissolve in mucus secreted by olfactory mucosa

Question 19

What are the 3 phases of speech?

Answer 19

respiration -> lung function
phonation -> laryngeal function
articulation -> vocal tract (upper airways and oral cavity)

Question 20

Above what structure is classed as the upper airway?

Answer 20

above the larynx

Question 21

Where are alveolar macrophages?

Answer 21

lie on top of pneumocytes or free in alveolar spaces

Question 22

Function of alveolar macrophages

Answer 22

phagocytose particles from inspired air (often carbon which is why a smoker’s lung is blackened)

Question 23

What are pores of Kohn?

Answer 23

small gaps between alveoli
not present at birth
provides channels for spread of pneumonia and cancer that grows along the walls of alveoli

Question 24

What are Lambert’s canals?

Answer 24

tubular connections which connect terminal and respiratory bronchioles with adjacent peribronchial alveoli

Question 25

Describe type 1 pneumocytes

Answer 25

flattened nuclei
thin for gas exchange

Question 26

Describe type 2 pneumocytes

Answer 26

larger darker nuclei
surfactant production

Question 27

Function of pulmonary veins

Answer 27

return oxygenated blood back to the heart

Question 28

What are the lungs themselves oxygenated by?

Answer 28

bronchial arteries
arise from systemic circulation

Question 29

Function of the pleura

Answer 29

facilitates respiratory movement

Question 30

Describe the pleura

Answer 30

a pair of serous membranes lining the thoracic wall (parietal), and lungs (visceral)
mesothelial cell lining (secrete fluid rich in hyaluronic acid)
connective tissue submesothelium
elastin layer

Question 31

How does the elastin layer of the pleura differ between the parietal and visceral pleurae?

Answer 31

visceral = double layer and thicker to account for lung movement

parietal = single layer and thinner