Histology and Embryology (Respiratory)

Question 1

What are the respiratory system functions in blood pressure control?

Answer 1

Via renin-angiotensin system. Angiotensin I -> angiotensin II via angiotensin-converting enzyme (ACE) in lung capillaries.

Question 2

Describe the epithelial changes that happen as you move through the nasal cavity.

Answer 2

Initial part (vestibule) has keratinised stratified squamous epithelium, then keratin is lost, then it is respiratory epithelium.

Question 3

Describe respiratory epithelium.

Answer 3

Pseudostratified ciliated columnar epithelium with goblet cells.

Question 4

What does the lamina propria in the nose contain?

Answer 4

Seromucous glands and a rich venous plexus which can quickly engorge with blood and block the nose.

Question 5

What is the difference between olfactory and respiratory epithelium?

Answer 5

It is taller.

Question 6

What parts of the oropharynx and epiglottis have non-keratinised stratified squamous epithelium?

Answer 6

All of the oropharynx, the anterior (lingual) surface and upper part of the posterior surface of the epiglottis.

Question 7

What are the vocal folds and adjacent structures covered with?

Answer 7

Stratified squamous epithelium.

Question 8

What is the open side of the C shaped cartilage of the trachea spanned by?

Answer 8

Fibroelastic tissue and smooth muscle (trachealis muscle).

Question 9

Describe the layers of the trachea.

Answer 9

Respiratory epithelium -> basal lamina -> lamina propria (connective tissue with abundant elastic fibres) -> submucosa (connective tissue, includes numerous seromucous glands).

Question 10

What are the rings of hyaline cartilage in the trachea replaced by in the bronchi?

Answer 10

Irregularly shaped cartilage plates.

Question 11

Describe the layers of a bronchus.

Answer 11

Respiratory epithelium -> lamina propria -> muscularis (ring of smooth muscle) -> submucosa (adipose tissue with some seromucous glands)

Question 12

When is cartilage lost in the airway?

Answer 12

When it is about 1mm in diameter.

Question 13

Compared to bronchi, what do bronchioles lack and still have?

Answer 13

Lack cartilage and glands, still have smooth muscle.

Question 14

What happens to the epithelium as you progress down the respiratory tree?

Answer 14

It decreases in height from columnar to cuboidal.

Question 15

What is the lamina propria composed of in bronchioles?

Answer 15

Smooth muscle, elastic and collagenous fibres.

Question 16

What are the terminal bronchioles?

Answer 16

The smallest bronchioles that lack respiratory (gas exchange) function.

Question 17

What are the roles of club cells and where are they found?

Answer 17

Stem cells, detoxification, immune modulation, surfactant production.

Question 18

Where does gas exchange start?

Answer 18

Respiratory bronchioles.

Question 19

Describe type I alveolar cells (pneumocytes).

Answer 19

Simple squamous epithelium that lines the alveolar surfaces covering over 90% of alveolar surface. Provide a barrier of minimal thickness that is permeable to gases.

Question 20

Describe type II alveolar cells (pneumocytes).

Answer 20

Polygonal in shape, free surface covered by microvilli and cytoplasm displays dense membrane bound lamellar bodies which contain surfactant (released by exocytosis).

Question 21

What are alveolar macrophages (dust cells)?

Answer 21

Free cells in septa or migrating over luminal surfaces of alveoli, phagocytosing inhaled particles that escape entrapment.

Question 22

What does the air-blood barrier consist of?

Answer 22

Type I cell, the endothelial cell and the basal lamina of each (200-600nm).

Question 23

What are the pores of Kohn?

Answer 23

Pores between alveoli.

Question 24

What are the pleural membranes composed of?

Answer 24

Outer layer of simple squamous epithelium (mesothelium) backed by layers of fibrous and elastic connective tissue.

Question 25

What is the structural difference between the visceral and parietal pleura?

Answer 25

They are similar but parietal generally simplest membrane lining the thoracic cavity.

Question 26

What is the ridge called that forms between the respiratory diverticulum and the eosophagus?

Answer 26

Treacheoesophageal ridge.

Question 27

What does the respiratory diverticulum split into?

Answer 27

2 lung buds.

Question 28

What does the tracheoesophageal ridge close up to form?

Answer 28

The trachea and the oesophagus.

Question 29

What surrounds the lung buds and the oesophagus?

Answer 29

Splanchnic mesoderm.

Question 30

What is an oesophageal atresia?

Answer 30

Blind ending of the oesophagus.

Question 31

What is a tracheoesophageal fistula?

Answer 31

Communication between the trachea and oesophagus.

Question 32

Can fistulas and atresias occur in combos?

Answer 32

Yes.

Question 33

At what days do the primary, secondary and tertiary bronchial buds form?

Answer 33

Primary - 28 days, secondary - 30 days, tertiary - 38 days.

Question 34

When are the terminal bronchioles formed?

Answer 34

At 16 weeks.

Question 35

What are the stages of embryological lung development?

Answer 35

Embryonic, pseudoglandular, canalicular, saccular, alveolar.

Question 36

What time periods are these stages associated with?

Answer 36

Embryonic: 26 days - 6 weeks. Pseudoglandular: 6-16 weeks. Canalicular: 16-28 weeks. Saccular: 28-36 weeks. Alveolar: 36 weeks - early childhood.

Question 37

Describe lung tissue in the newborn.

Answer 37

Blood capillaries are in direct contact with the mature alveoli.