Embryology 3

Question 1

What are the 4 stages of lung development?

Answer 1

Development of trachea and lung buds

Development of pleural cavity and pleurae

Differentiation of lung buds

Development of diaphragm

Question 2

When does development of the trachea and the lungs occur?

Answer 2

Week 4 of gestation

Question 3

Define primordium

Answer 3

An organ or tissue in its earliest recognizable stage of development

Question 4

Where does the respiratory primordium form?

Answer 4

Starts as a median outgrowth from the laryngotracheal groove (diverticulum) from the ventral part f the foregut

Question 5

When does the diverticulum form the trachea and the lung buds?

Answer 5

When the diverticulum becomes covered with mesoderm on its outside and enlarges

Question 6

What forms between the trachea and the oesophagus?

Answer 6

Oesophagotracheal septum

Question 7

What is a tracheoesophageal fistula?

Answer 7

Fistula = an abnormal or surgically made passage between a hollow or tubular organ and the body surface, or between two hollow or tubular organs, ie. between 2 epithelialized surfaces. TOF is a common congenital abnormality.

Atresia = a condition in which an orifice or passage in

the body is (usually abnormally) closed or absent.

Question 8

Where does the visceral pleura arise from?

Answer 8

The splanchnic mesoderm

Question 9

Where does the parietal pleura arise from?

Answer 9

The somatic mesoderm

Question 10

Where on the diagram is the splanchnic and the somatic mesoderm?

Answer 10

Question 11

Where do the pulmonary arteries individuate?

Answer 11

6th aortic arch

Question 12

Which part of the embry (in the embryonic period) creates the median trachea and two lateral pockets?

Answer 12

The respiratory diverticulum

Question 13

What stages is the foetal period split into?

Answer 13

The pseudoglandular stage

Canalicuar stage

Saccular stage

Question 14

What happens during the pseudoglandular stage?

Answer 14

Set up of all pulmonary structures except elements needed for gas exchange

Question 15

What happens during the canalicular stage?

Answer 15

Terminal bronchioles give rise to tubes that form the respirtory part of the lung. Differentiation of epithelium into cuboidal secretory cells (type 2 pneumocytes) and flat type 1 pneumocytes.

Question 16

What happens during the saccular stage?

Answer 16

Formation of alveolar sacs separated by primary septa.

These sacs are progressively divided into smaller subunits by secondary septa leading to the formation of alveoli.

Question 17

What happens to alveoli during the postnatal period?

Answer 17

More form from the terminal sacs (95% of adult like alveoli are formed post-natally)

Alveoli enlarge

As lungs enlarge - Increase in respiratory bronchioles

Question 18

What is the effect of folding of embryo during week 3?

Answer 18

Gives rise to the primitive gut tube, gut tube forms the endoderm

Question 19

What is the name given to the congenital problem whereby there is insufficient surfactant?

Answer 19

Respiratory distress syndrome or hyaline membrane disease

Question 20

Agenesis is another congenital condition of the lung, what is it and how does it differ from aplasia?

Answer 20

Agenesis refers to the failure of an organ to develop during embryonic growth and development due to the absence of primordial tissue.

Aplasia- the failure of an organ or tissue to develop or to function normally.

Question 21

What is an accessory lobe?

Answer 21

Invaginations of the visceral pleura create accessory fissures that separate individual bronchopulmonary segments into accessory lobes

Question 22

Define azygous lobe.

Answer 22

Congenital variation of the upper lobe of the right lung. Caused when the posterior cardinal vein, one of the precursors of the azygos vein, fails to migrate over the apex of the lung and penetrates it instead, carrying along two pleural layers that invaginates into the upper portion of the right upper lobe.

Question 23

What are the four embryonic components of the diaphragm?

Answer 23

Question 24

Where is the septum transversum originally located?

Answer 24

Opposite C3-C5 somites

Question 25

Where does the septum transversum migrate during the development of the diaphragm?

Answer 25

Caudally, bringing with it spinal nerves C3-C5

Question 26

What are the three major congenital defects?

Answer 26

Diaphragm doesn’t completely close

Herniation of abdominal contents into the chest

Pulmonary hypoplasia

Question 27

What is a hernia?

Answer 27

Hernia is a general term used to describe a bulge or protrusion of an organ through the structure or muscle that usually contains it.

Question 28

What are the names given to these hernia?

Answer 28

Question 29

Give examples of hiatal herniae

Answer 29