SFP: respiratory tract and lung histology

Question 1

What portions of the lungs are part of the conducting zone?

Answer 1

Bronchi, bronchioles, and terminal bronchioles

Question 2

What portions of the lungs are part of the respiratory zone?

Answer 2

Respiratory bronchioles, alveolar ducts, and alveoli

Question 3

What are the necessary characteristics of the conducting zone for normal pulmonary function?

Answer 3

1. A wall that can stay patent for airflow
2. Surface mucosa that transports foreign substances or debris out of the system
3. Mucosa contributing to a moist surface to condition air

Question 4

What is the mucosa that lines the conducting system?

Answer 4

Respiratory epithelium aka pseudostratified ciliated columnar epithelium

Question 5

What cells are found in respiratory epithelium?

Answer 5

Ciliated columnar cells, goblet cells, brush cells, granule cells, and basal (stem) cells

Question 6

What do goblet cells do?

Answer 6

Produce mucin

Question 7

What is the function of brush cells in respiratory epithelium?

Answer 7

They’re sensory/chemoreceptors; they can sense chemical toxins and trigger various responses

Question 8

What are the main proteins found in cilia?

Answer 8

Dynein, nexin, and tubulin

Question 9

What is dynein?

Answer 9

A protein in cilia that allows for movement

Question 10

What is nexin?

Answer 10

A protein in cilia that limits the sliding/bending caused by dynein

Question 11

What is tubulin?

Answer 11

The protein that makes up the bulk of cilia

Question 12

What is the muco-ciliary escalator? What happens if it doesn’t work?

Answer 12

A combination of a layer of mucus floating on top of water that is moved by coordinated cilia. Chronic infections happen if it does not function correctly.

Question 13

What are 3 factors that can impact the ability of cilia to move mucus along the surface?

Answer 13

1. Metaplasia
2. Mutations in dynein changing the structure of cilia and causing ciliary dyskinesia
3. CTFR gene mutation alters chloride channels and causing thicker mucus (seen in cystic fibrosis)

Question 14

Describe the histology of the trachea (deep to superficial).

Answer 14

1. Mucosa: respiratory epithelium
2. Lamina propria with seromucous glands that make watery mucous
3. Submucosa: 12 horseshoe cartilages and the trachealis muscle
4. Adventitia: perichondrium and connective tissue

Question 15

Stimulation of ___ causes forceful coughing.

Answer 15

The trachealis muscle

Question 16

What is the difference between terminal bronchi and bronchioles?

Answer 16

Bronchioles have no cartilage

Question 17

Describe the histology of bronchi.

Answer 17

1. Mucosa: respiratory epithelium with fewer goblet cells
2. Lamina propria with seromucous glands
3. Cartilage in the form of plates
4. Smooth muscle bundles that increase distally as cartilage decreases

Question 18

Describe the histology of bronchioles.

Answer 18

1. Mucosa: more cuboidal but still ciliated
2. Lamina propria with no glands
3. No cartilage

Question 19

What differentiates a terminal from a respiratory bronchiole?

Answer 19

The presence of an alveolus

Question 20

What are club cells?

Answer 20

The stem cells of bronchioles that secrete components of surfactant, lysozyme, secretory components of IgA.

Question 21

In club cells, what metabolizes irritants?

Answer 21

Smooth ER P450

Question 22

Where do we find MALT?

Answer 22

In the submucosa of bronchioles

Question 23

What is a pulmonary lobule?

Answer 23

A functional unit that defines everything served by a single terminal bronchiole

Question 24

Blood coming to the capillary travels ___, and blood moving away from the capillary travels ___?

Answer 24

Along the bronchial tree; At the periphery

Question 25

What are type I alveolar cells?

Answer 25

Squamous alveolar cells that make up the majority of alveolar wall. They contain tight junctions and desmosomes, turnover surfactant, and provide a thin barrier that is permeable to gases

Question 26

What are type II alveolar cells?

Answer 26

Cells interspersed with type I that act as stem cells and produce surfactant to reduce surface tension and prevent alveolar collapse