Development of Respiratory system - Leah

Question 1

Laryngotracheal Groove and lung form in week _____.

Answer 1

week 4

Question 2

Laryngotracheal groove appears in the ____________.

Answer 2

Floor of caudal pharynx

Question 3

The lung bud is formed by what?

Answer 3

By the laryngotracheal groove protrudes ventrally forming an endoderm outgrowth from the foregut.

Question 4

_______ develops and separates lung bud (ventrally) from the foregut (Distally)

Answer 4

Tracheoesophageal septum

Question 5

_______ develops and separates lung bud (ventrally) from the foregut (Distally).

Answer 5

Tracheoesophageal septum

Question 6

The respiratory diverticulum retains a connection with the pharynx at the ______.

Answer 6

Primordial laryngeal inlet.

Question 7

What causes Esophageal Atresia?

Answer 7

caused by posteriorly deviating septum

Question 8

What are the derivatives of the Lung Bud? (2)

Answer 8

Endoderm = epithelial lining + glands or airways

Splanchnic mesoderm = smooth muscle + CT of airways.

Question 9

Describe the Development of the Larynx….

Answer 9

Laryngeal cartilages and musculature arise from pharyngeal arch pairs 4 & 6.

Question 10

Describe development of epiglottis…

Answer 10

Epiglottis from from mesenchyme of the caudal hypopharyngeal eminence.

Question 11

Laryngeal mm. arising from 4th arch are innervated by __________.

Answer 11

Superior laryngeal N.

Question 12

Laryngeal mm. arising from 6th arch are innervated by __________.

Answer 12

recurrent laryngeal N.

Question 13

What is lung bud splitting and when does it occur?

Answer 13

Lung bud divides to form 2 primary bronchial buds (future primary bronchi)
*Occurs on day 28

Question 14

What happens on day 30 in regards to lung bud splitting?

Answer 14

Primary bronchial buds divide to from secondary bronchial buds (3 on right, 2 on left)
*Each secondary bud will supply one lobe of the lung.

Question 15

Secondary bronchial buds divide yet again to form what?

Answer 15

Tertiary (segmental) bronchial buds (10 on right, 8-9 on left)

Question 16

Tertiary bronchus + surrounding tissue = ?

Answer 16

A bronchopulmonary segment

Question 17

What is the pathway of respiratory tree branching?

Answer 17

Trachea -> PRimary bronchi -> secondary Bronchi - > tertiary (segmental) bronchi -> bronchioles -> terminal Bronchioles -> respiratory bronchioles -> alveolar ducts -> terminal sacs (primitive alveoi)

Question 18

What are the 4 stages of lung development?

Answer 18

Pseudoglandular (6-16 weeks)
Canalicular (16-26) weeks
Terminal Sac (26 weeks - birth)
Alveolar (32 weeks to 8 years of age)

Question 19

What happen during the Pseudoglandular stage?

Answer 19

Lung tissue appears histologically as a collection of exocrine glands

All major lung structures have developed except for most distal portions of respiratory tree where gas exchange occurs (respiratory bronchioles + alveolar sacs)

Question 20

What happen during the Pseudoglandular stage?

Answer 20

Lung tissue appears histologically as a collection of exocrine glands

All major lung structures have developed except for most distal portions of respiratory tree where gas exchange occurs (respiratory bronchioles + alveolar sacs)
* A fetus born here will not survive!

Question 21

What happens during the Canalicular stage?

Answer 21

Lung tissue becomes highly vascular.

At end of this stage, respiration is possible. Each terminal bronchiole has split into 2 (+) respiratory bronchioles which have developed primitive alveolar ducts. Some ducts already lead into terminal sacs.
*Fetus may survive if born at this stage, but many die as lungs are still immature in their development.

Question 22

What happens at Terminal Sac Stage?

Answer 22

More terminal sacs develop and are hugged by capillaries establishing the BLOOD AIR BARRIER.

At week 26: terminal sac walls = a single layer of simple squamous cells, most of which are Type I alveolar cells through which gases diffuse.

Scattered amongst the Type I cells are a few rounded Type II alveolar cells: produce, store, and secrete pulmonary surfactant.