Embryology 3

Question 1

Which four structures does the embryo need to develop in terms of the respiratory system?

Answer 1

Trachea
Lungs
Pleura
Diaphragm

Question 2

What are the two layers of the bilaminar disc?

Answer 2

Epiblast
Hypoblast

Question 3

What are the three layers of the trilaminar disc?

Answer 3

Ectoderm
Mesoderm
Endoderm

Question 4

What is the name of the process which turns the bilaminar disc to the trilaminar disc?

Answer 4

Gastrulation

Question 5

What else is found between the trilaminar disc?

Answer 5

Notochord

Question 6

What happens during lateral folding?

Answer 6

Somatic mesoderm folds down to surround the splanchnic mesoderm of the intraembryonic body cavity

Question 7

What happens to the yolk sac during the lateral folding process?

Answer 7

It gets absorbed into the primitive gut.

Question 8

Where do the lungs and trachea form from?

Answer 8

Foregut part of the primitive gut tube

Question 9

What does the folding of the embryo give rise to?

Answer 9

Primitive gut tube

Question 10

Where does the primitive gut tube form from?

Answer 10

Endoderm

Question 11

Where is the somatic layer of the mesoderm?

Answer 11

Close to the endoderm.

Question 12

Where is the splanchnic layer of the mesoderm?

Answer 12

Close to endoderm/gut tube

Question 13

At how many weeks do the lung buds form?

Answer 13

4

Question 14

Where do the lung and trachea buds come from?

Answer 14

Bud out from the ventral/anterior wall of the primitive foregut (endoderm)

Question 15

What are the lung and trachea buds closely surrounded by?

Answer 15

Lateral plate splanchnic (visceral) mesoderm

Question 16

Where is the trachea related to the oesophagus?

Answer 16

Trachea lies anterior to oesophagus

Question 17

What are the three portions of the gut?

Answer 17

Foregut
Midgut
Hindgut

Question 18

What develops between the oesophagus/pharynx and the trachea, completely separating them?

Answer 18

Oesophagotracheal septum

Question 19

What may occur is the oesophagotracheal septum doesn’t form?

Answer 19

Tracheoesophageal fistula (TOF) and Oesophageal Atresia

Question 19

Define fistula

Answer 19

An abnormal passage between 2 epithelialized tubes or surfaces.

Question 20

Define artesia.

Answer 20

Condition in which an orifice or passage in the body is closed or absent.

Question 21

What type of pleura is the lung covered with?

Answer 21

Visceral

Question 22

What type of pleura are the lungs lined with?

Answer 22

Parietal pleura

Question 23

Describe the growing of the lung buds.

Answer 23

Each lung bud invaginates the wall of the coelomic cavity and then grwos to fill a greater part of the cavity.
Pleura then forms.

Question 24

What happens to the coelomic cavity as a result of the lungs growing?

Answer 24

Reduced to a slitlike space known as the pleural cavity

Question 25

Where does the pleura develop from?

Answer 25

Lateral plate mesoderm

Question 26

Which layers of the lateral plate mesoderm forms- 1. the visceral pleura 2. the parietal pleura

Answer 26

1. Visceral= splanchnic layer 2. Parietal= somatic layer

Question 27

Describe the formation of the pleural cavity

Answer 27

Lung buds push the splanchnic mesoderm towards the somatic mesoderm and become completely surrounded by both layers. The space between the two layers will become the pleural cavity.

Question 28

However, the space between the splanchnic and somatic mesoderm around the lungs is initially continuous with what? What is this continuity called?

Answer 28

Pericardial and peritoneal cavity Pericardioperitoneal canal.

Question 29

Why does the pleural cavity need to be separated off from the pericardioal and peritoneal cavity?

Answer 29

To maintain the correct ventilatory pleural cavity pressures.

Question 30

How is the the pericardoperitoneal canal separated from the pericardial cavity?

Answer 30

Formation of the pleuropericardial folds

Question 31

Describe the structure of pleuropericardial folds.

Answer 31

Formed from the body wall and lined by somatic mesoderm

Question 32

When is the Pseudoglandular stage?

Answer 32

7-17 weeks

Question 33

What happens in the Pseudoglandular stage?

Answer 33

Development of lung except respiratory part

Question 34

When is the Canalicular stage ?

Answer 34

Weeks 17-27

Question 35

What happens in the Canalicular stage ?

Answer 35

Formation of respiratory part. Alveolar ducts form and epithelium starts to differentiate into Type I and Type II pneumocytes

Question 36

When is the Saccular stage ?

Answer 36

Weeks 27-40

Question 37

What happens in the Saccular stage ?

Answer 37

Formation of alveolar sacs, primitive alveoli and surfactant

Question 38

At what stage does gas exchange begin to happen?

Answer 38

Saccular stage

Question 39

When is the alveolar stage?

Answer 39

32 weeks-8 years old

Question 40

What happens in the alveolar stage?

Answer 40

Proliferation of alveoli into alveolar scas

Question 41

What is Neonatal Respiratory Distress Syndrome ?

Answer 41

Partial collapse of the alveoli

Question 42

hat cuases Neonatal Respiratory Distress Syndrome?

Answer 42

Surfacing deficiency

Question 43

What % of neonates are affected by Neonatal Respiratory Distress Syndrome?

Answer 43

2%

Question 44

What happens because of the partial collapse of the alveoli?

Answer 44

Debris consisting of blood elements accumulate ->this gives a glassy appearance under the microscope because of hyaline membranes

Question 45

What is lung agenesis caused by?

Answer 45

-Failure of lung bud to develop/ branch -Insufficient mesoderm -Teratogens

Question 46

What is pulmonary hypoplasia?

Answer 46

Incomplete development of the lungs, resulting in an abnormally low number or size of bronchopulmonary segments or alveoli.

Question 47

What closes off the pleural cavities from the peritoneal cavity of the abdomen?

Answer 47

Pleuroperitoneal folds/membranes forming the diaphragm

Question 48

What part of the diaphragm does Septum transversum form?

Answer 48

Central tendon of the diaphragm

Question 49

What forms the muscular part of the diaphragm?

Answer 49

Skeletal muscle ingrowth from the peripheral body wall

Question 50

What does the dorsal mesentery of the oesophagus do?

Answer 50

Attaches the embryological oesophagus to the posterior thoracic wall

Question 51

Skeletal muscle from the periphery covers the dorsal mesentery to form what?

Answer 51

Diaphragmatic crura.

Question 52

Name the four structures which form the diaphrgam.

Answer 52

Septum transversum Pleuroperitoneal folds Skeletal muscle ingrowth from the peripheral body wall The dorsal mesentery of the oesophagus

Question 53

Name three weak areas in the developed diaphragm

Answer 53

Oesophageal hiatus Foramen of Bochdalek Foramen of Morgagni

Question 54

What can happen at the Foramen of Bochdalek or the Foramen of Morgagni?

Answer 54

Diaphragmatic hernia

Question 55

What can happen at the Oesophageal hiatus?

Answer 55

Hiatus hernia

Question 56

Define hiatal hernia

Answer 56

Protrusion of an organ through the structure or muscle that usually contains it.