Development of the Respiratory System

Question 1

Describe the development of the neural crest

Answer 1

Part of the ectoderm will develop into the neural groove and the tips of the walls of this groove are called neural crest cells.

Question 2

What do the parietal (somatic) and visceral (splanchnic) mesoderm form?

Answer 2

Parietal = body walls,
Visceral = Surround the organs

Question 3

Describe what occurs in lateral plate mesoderm folding

Answer 3

The parietal layer of the lateral plate mesoderm merges with the ectoderm. The primitive yolk sac will become pinched and will form the digestive tract or gut tube and the visceral layer will envelope the future gut tract. Finally the parietal layer and ectoderm merge and fuse in the ventral midline.

Question 4

What does the connection between the gut tube and secondary yolk sac form?

Answer 4

Vitelline duct

Question 5

At the end of lateral folding, what is present?

Answer 5

• A cavity which will become the thoracic, abdominal and pelvic cavity.
• A body wall made out of the surface ectoderm and parietal lateral plate mesoderm below it.
• Gut tube, suspended by visceral layer of lateral plate mesoderm

Question 6

What occurs while the lateral folding takes place?

Answer 6

Cranio-caudal folding which it where head and tail meet with the two lateral folds at the umbilicus.

Question 7

Describe the start of the development of the lung buds at week 4

Answer 7

In the cervical region of the gut tube, the respiratory diverticulum starts to appear. It begins to expand ventrally towards the chest. Meanwhile tracheo-oesophageal ridges (folds) grow towards each other and split the respiratory diverticulum from the gut tube. The diverticulum bifurcates into two branches. Later these expand. Terminal ends of these are called lung buds.

Question 8

What are pharyngeal arches?

Answer 8

Growth of mesenchyme tissue in the cranial region resulting in formation of arches which are separated by pharyngeal clefts

Question 9

How many pharyngeal arches are there?

Answer 9

5, numbered; 1,2,3,4,6.

Question 10

When do the pharyngeal arches begin to develop?

Answer 10

4-5th week of development

Question 11

Where does the laryngeal orifice arise?

Answer 11

In-between the laryngeal and epiglottic swellings

Question 12

What is maintained despite the tracheo-esophageal septum separates gut tube and resp tract.

Answer 12

The laryngeal opening. This is because both nose and mouth share a common pathway

Question 13

What does the upper, middle and lower end of the respiratory diverticulum become?

Answer 13

Upper - Larynx,
Middle - Trachea,
Lower - Tertiary bronchi, bronchioles and alveoli.

Question 14

What is the respiratory diverticulum developed from?

Answer 14

Endoderm and is then surrounded by the visceral layer of lateral plate mesoderm

Question 15

Describe what occurs when the bronchial tree begins to develop?

Answer 15

It pushes the viseral layer of lateral plate mesoderm which becomes the visceral pleura

Question 16

Epithelium of the respiratory system is derived from what?

Answer 16

Endoderm

Question 17

Besides respiratory epithelium, what is the rest of the respiratory system developed from?

Answer 17

Mesoderm

Question 18

Describe the four overlapping stages in lung development

Answer 18

1) Pseudoglandular
2) Canicular
3) Terminal Saccular
4) Alveolar

Question 19

What stages of lung are not compatible with life

Answer 19

The first two stages and at this point the sections involved in gas exchange are not developed yet.

Question 20

What occurs from 20 weeks that allows a foetus to be able to survive in a NICU

Answer 20

Type 2 pneumocytes being to secrete surfactant

Question 21

From what gestation age can a foetus can survive on its own?

Answer 21

28 weeks onwards

Question 22

What are the four sources of origin from the diaphragm?

Answer 22

1) Pleura-peritoneal fold
2) The pleura-peritoneal fuse with the septum transversum (2)
3) Mesentery of the oesophagus (from which the crura develop.
4) Muscular in-growth from the body wall.

Question 23

What forms the central tendon of diaphragm?

Answer 23

The septum transversum which contains myoblasts from somites in C3,4,5.

Question 24

What happens if something goes wrong and the tracheo-esophageal folds do not fuse properly

Answer 24

in 90% of cases there will be communication between the trachea and oesophagus called a tracheo-oesophageal fistula, which is usually accompanied by oesophageal atresia.

Question 25

What occurs in other form of tracheo-esophageal folding abnormalities

Answer 25

When the baby attempts to feed, milk enters the trachea causing chocking and possible development of pneumonitis and pneumonia. Also possibility of retrograde passage of gastric acid from GI tract into respiratory

Question 26

What occurs in oesophageal atresia?

Answer 26

During normal pregnancy, the foetus swallows amniotic fluid which is reabsorbed from the gut and returned to maternal circulation. If oesophageal atresia develops then this circulation of fluid is prevented and polyhydramnios develops.

Question 27

How does failure in fusion of diaphragmatic origins cause?

Answer 27

Diaphragmatic hernia

Question 28

What is respiratory distress syndrome?

Answer 28

Insufficient surfactant results in the collapse of the alveolar wall during expiration.

Deficiency of surfactant secretion results in respiratory distress syndrome. Treatment can be artificial surfactant and treatment with glucocorticoids to stimulate surfactant secretion