Respiratory Embryology

Question 1

What are the three germ layers?

Answer 1

Endoderm
Mesoderm
Ectoderm

Question 2

What does the endoderm form?

Answer 2

Lining of trachea and bronchial tree

Question 3

What does the ectoderm contribute towards?

Answer 3

Neural innvervation

Question 4

What does the visceral mesoderm form?

Answer 4

All other lung tissue e.g. smooth muscle, cartilage etc

Question 5

What do the head and neck develop from?

Answer 5

Pharyngeal arches

Question 6

Where does the tongue develop from?

Answer 6

The lingual swelling

Question 7

Where does the epiglottis develop?

Answer 7

Behind the tongue

Question 8

What is the function of the epiglottis?

Answer 8

To prevent food entering the respiratory tract and directing it down the oesophagus

Question 9

What is the function of the epiglottis?

Answer 9

To prevent food entering the respiratory tract and directing it down the oesophagus

Question 10

Is the branching of the bronchial tree regulated or irregulated bifurcation?

Answer 10

Very regulated

Question 11

When does the development of the bronchial tree occur?

Answer 11

Mid - late embryonic period

Question 12

What happens in week 5?

Answer 12

Initial lung buds found either side

Question 13

What happens in week 6?

Answer 13

Growth and bifurcation into bronchi

Question 14

What happens in week 8?

Answer 14

Further bifurcation and clear definition of lobes

Extensive branching pattern is now in place

Question 15

What are some respiratory congenital defects?

Answer 15

Oesophageal atresia

Tracheoesopohageal fistula

Question 16

Why are there a number of respiratory congenital defects?

Answer 16

If the separation of the respiratory tract and gut tube does not occur

Question 17

What is oesophageal atresia?

Answer 17

When the upper part of the oesophagus doesn’t connect with the lower oesophagus and stomach but ends in a pouch (blind - ending)

Question 18

What is a fistula?

Answer 18

A communication that isn’t supposed to be there

Question 19

What is tracheoesophageal fistula?

Answer 19

A connection between the upper part of the oesophagus and the trachea.
This causes air to pass from the windpipe to the oesophagus and stomach, and stomach acid to pass into the lungs.

Question 20

What is the most common respiratory congenital defect?

Answer 20

Tracheoesophageal fistula

Question 21

When is the embryonic stage?

Answer 21

26 days - 6 weeks

Question 22

What occurs in the embryonic stage?

Answer 22

Respiratory diverticulum forms

Initial branching gives lungs, lobes and segment

Question 23

When is the pseudoglandular stage?

Answer 23

6 - 16 weeks

Question 24

What occurs in the pseudoglanduar stage?

Answer 24

14 more generations of branching: terminal bronchioles

Question 25

When is the canalicular stage?

Answer 25

16 - 28 weeks

Question 26

What occurs in the canalicular stage?

Answer 26

Terminal bronchioles form respiratory bronchioles which result in 3 - 6 alveolar ducts

Question 27

What occurs in the canalicular stage?

Answer 27

Terminal bronchioles form respiratory bronchioles which result in 3 - 6 alveolar ducts

Question 28

When is the saccular stage?

Answer 28

28 - 36 weeks

Question 29

What occurs in the saccular stage?

Answer 29

Terminal sacs form

Capillaries establish close contact

Question 30

When is the alveolar stage?

Answer 30

36 weeks - early childhood

Question 31

What occurs in the alveolar stage?

Answer 31

Alveoli mature

Question 32

What lines the alveolar sacs?

Answer 32

Cuboidal epithelium

Question 33

Why can’t material diffuse across cuboidal epithelium?

Answer 33

They are thick cells

Question 34

What do the cuboidal epithelium differentiate into during alveolar development?

Answer 34

Type I and Type II pneumocytes

Question 35

What is the function of Type I pneumocytes?

Answer 35

Thin squamous cells that give ruse to the thin barrier (blood - air barrier) and so allow the diffusion of substances

Question 36

What is the function of Type II pneumocytes?

Answer 36

Produce surfactant

Question 37

What is the function of surfactant?

Answer 37

Prevents collapse of alveoli by reducing surface tension

Question 38

What causes respiratory distress syndrome?

Answer 38

Premature infants are born before sufficient maturation of the alveoli so have too little surfactant