Development of the Respiratory System

Question 1

The laryngotracheal groove appears in the floor of the ___ pharynx.

Answer 1

caudal

Question 2

The ___ groove protrudes ventrally, forming an endodermal outgrowth from the ___ known as the ___ ___ (___ ___).

Answer 2

laryngotracheal; foregut; lung bud; (respiratory diverticulum)

Question 3

What separates the lung bud (ventrally) from the foregut (dorsally)?

Answer 3

a tracheoesophageal septum

Question 4

The respiratory ___ retains a connection with the pharynx at the primordial ___ ___.

Answer 4

diverticulum; laryngeal inlet

Question 5

What condition results from the incomplete division of the cranial part of the foregut into respiratory and esophageal parts during the fourth week?

Answer 5

Tracheoesophageal fistula with esophageal atresia

Question 6

What does endoderm of the lung bud form?

Answer 6

epithelial lining and glands of airways

Question 7

what does the splanchnic mesoderm form?

Answer 7

smooth muscle and connective tissue of airways

Question 8

The ___ develops as a portion of the foregut immediately caudal to the pharynx.

Answer 8

esophagus

Question 9

What laryngeal structures arise from the 4 and 6 pairs of the pharyngeal arch?

Answer 9

laryngeal cartilages and musculature

Question 10

What forms the epiglottis?

Answer 10

Mesenchyme of the caudal hypopharyngeal eminence

Question 11

Laryngeal muscles from the 4th arch are innervated by what nerve? 6th?

Answer 11

superior laryngeal n.

recurrent laryngeal n

Question 12

Lung buds divide to form two primary ___ buds on day ___.

Answer 12

bronchial; 28

Question 13

Primary bronchial buds extend into ___ canals.

Answer 13

pericardioperitoneal

Question 14

___ mesoderm gives rise to ___ pleura of the lungs and ___ mesoderm lining the thoracic body wall gives rise to the ___ pleura.

Answer 14

Splanchnic; visceral; somatic; parietal

Question 15

Primary bronchial buds divide to form ___ or ___ bronchial buds that will supply ___ lobe of the lungs. There are ___ on right and ___ on the left. This occurs on day ___.

Answer 15

secondary; lobar; one; 3; 2; 30

Question 16

Tertiary bronchus + the surrounding tissue = a ___ segment. There are ___ on the right and ___ or ___ on the left.

Answer 16

bronchopulmonary; 10; 8 or 9

Question 17

What is the main site of gas exchange?

Answer 17

alveoli

Question 18

What is the respiratory tree branching beginning with the trachea?

Answer 18

trachea, primary bronchi, seconday (lobar) bronchi, teritary (segmental) bronchi, bronchioles, terminal bronchioles, respiratory bronchioles, alveolar ducts, terminal sacs (primitive alveoli)

Question 19

Matching. When do the following lung segments develop?
A. Pseudoglandular
B. Canlicular
C. Terminal sac
D. Alveolar

1. 26 weeks - birth
2. 6 - 16 weeks
3. 16 - 26 weeks
4. 32 weeks - 8 years of age

Answer 19

A. 2
B. 3
C. 1
D. 4

Question 20

During the pseudoglandular stage, how does lung tissue appear histologically?

Answer 20

as a collection of exocrine glands

Question 21

T/F. A fetus born during the pseudoglandular phase will NOT survive.

Answer 21

True.

Question 22

At the pseudoglandular stage, all major lung structures have developed expect for what?

Answer 22

the areas where gas exchange occurs ( respiratory bronchioles and alveolar sacs)

Question 23

When does lung tissue become vascular?

Answer 23

during the canalicular stage (weeks 16 - 26)

Question 24

What happens to the terminal bronchioles at the end of the canalicular stage?

Answer 24

each terminal bronchiole has split into 2 (+) respiratory bronchioles, which have developed primitive alveolar ducts.

Question 25

T/F. A fetus born at the beginning of the canalicular stage will survive because their lungs are no longer immature.

Answer 25

False, a fetus born near the end of this stage may survive, although many die as the lungs are still immature in their development.

Question 26

During the terminal sac stage, more sacs develop and are hugged by capillaries, establishing the ___-___ barrier.

Answer 26

blood-air

Question 27

At ___ weeks, the terminal sac walls = a single layer of ___ ___ cells, most of which are ___ ___ alveolar cells through which gases diffuse.

Answer 27

26; simple squamous; Type I

Question 28

What are scattered amongst the Type I cells and produce, store and secrete pulmonary surfactant?

Answer 28

Type II alveolar cells

Question 29

What is the function of surfactant?

Answer 29

it lines the inner wall of the alveolus, reduces surface tension at the air-alveolar interface and prevents alveolar collapse upon exhaling.

Question 30

When do Type II cells begin producing surfactant?

Answer 30

20 -22 weeks

Question 31

When is the amount of surfactant production sufficient for survival of premature infants?

Answer 31

weeks 26 -28

Question 32

Even if premature babies survive, they may suffer from what condition due to insufficient surfactant?

Answer 32

respiratory distress syndrome

Question 33

At what stage are the alveoli fully functional?

Answer 33

during the alveolar stage (weeks 32 - 8 years of age)

Question 34

When do 95% of alveoli mature?

Answer 34

postnatally (most form within the first 3 years) and continue to develop until 8 years of age