RESPIRATORY TRACT HISTOLOGY AND DEFENCE MECHANISMS

Question 1

What is in the upper respiratory tract?

Answer 1

Nasal cavity. Pharynx and larynx

Question 2

What is in the lower respiratory tract?

Answer 2

Trachea, primary bronchi and lungs

Question 3

What makes up the conducting zone?

Answer 3

The conducting zone, which includes everything from the nose to the smallest bronchioles, moves air into and out of the lungs.

Question 4

What makes up the respiratory zone?

Answer 4

The respiratory zone includes the respiratory bronchioles and alveoli and moves the respiratory gases,

Question 5

What is the mucociliary escalator?

Answer 5

The mucus and cilia acting together to move mucus out of the respiratory zone

Question 6

Describe how the histology of the conducting zone changes as you move down towards the respiratory zone?

Answer 6

The nasal cavity, trachea and bronchi have columnar cells with goblet cells
As you move down to the bronchioles the cells are more cuboidal and have Clara cells rather than goblet cells

Question 7

What’s the function of Clara cells?

Answer 7

They secrete surfactant

Question 8

What is the lamina propria?

Answer 8

A type of connective tissue found under the thin layer of tissues covering a mucous membrane.

Question 9

What are the 2 layers of the mucus layer in the mucociliary escalator?

Answer 9

Gel layer - produced by goblet cells it’s composed of high molecular weight glycoproteins
Sol layer - enables the gel mucus present at the tips of the cilia to be transported by the ciliary beating of the ciliated cells.

Question 10

What does mucus contain?

Answer 10

water, epithelial (surface) cells, dead leukocytes, mucin, and inorganic salts, anti-proteases, lysosomes and anti-microbial agents

Question 11

What are the 3 cell types that make up alveoli?

Answer 11

Type 1 pneumocystis
Type 2 pneumocytes
Alveolar macrophages

Question 12

How are neighbouring alveoli interconnected?

Answer 12

Through pores of Kohn

Question 13

Describe type 1 pneumocytes?

Answer 13

They make up 90% of alveolar surface, are highly flattened and consist of simple squamous epithelium. They cannot replicate or divide
They form a thin diffusion barrier

Question 14

Describe type 2 pneumocytes?

Answer 14

They are more numerous than type 1 but only make up 10% of alveolar surface.
They are cuboidal and are capable of rapid division
They produce surfactant which reduces surface tension and prevents alveoli from collapsing

Question 15

Describe alveolar macrophages?

Answer 15

They’re a phagocytes immune cell dispersed throughout alveoli

Question 16

What defence mechanisms do we have in the nose?

Answer 16

Hair which excludes large materials
Humidifying and warming the air can cause problems in terms of destroying the ideal environment for pathogens
It also has a mucociliary escalator

Question 17

What are some respiratory protective reflexes?

Answer 17

Cough
Sneeze
Swallow

Question 18

What is the deglutition reflex?

Answer 18

When respiration is inhibited as you swallow

Question 19

What is the Hering Breuer reflex?

Answer 19

Over-expansion of the lungs excites stretch receptors in the airways. Stimulation of these receptors, which send signals to the medulla by the vagus nerve, shortens inspiratory times as tidal volume increases, accelerating the frequency of breathing.

Question 20

What are juxtacapillary (J) receptors?

Answer 20

sensory nerve endings located within the alveolar walls in juxtaposition to the pulmonary capillaries of the lung, and are innervated by fibers of the vagus nerve

Once stimulated, impulses travel via the vagus nerve in slow conducting fibers, leading to rapid, shallow breathing. Extreme stimulation may result in apnea.

Question 21

What is apnoea?

Answer 21

The temporary cessation of breathing

Question 22

What is BALT?

Answer 22

Bronchus-associated-lymphoid-tissue