Embryology part 2

Question 1

What does the ectoderm go on to form ?

Answer 1

The epidermis of the skin and the neural tube

Question 2

What does the paraxial mesoderm go on to from ?

Answer 2

The dermatome, myotome and sclerotome

Question 3

What does the intermediate plate mesoderm go onto form ?

Answer 3

The urogenital system (kidneys and reproductive)

Question 4

What does the lateral plate mesoderm go onto form ?

Answer 4

The peritoneum, pleura and body cavities

Question 5

What does the endoderm go onto form ?

Answer 5

The respiratory system

Question 6

What happens to the bilaminar plate after the mesoderm has split?

Answer 6

It starts to fold and this creates the head and the bottom

Question 7

What is teratology ?

Answer 7

The study of the things which can go wrong during a babies development

Question 8

What are some examples of teratogens?

Answer 8

Environmental factors = Drugs, alcohol, tobacco, infectious agents, radiation, virus
Genetics

Question 9

What affects the risk which a teratogen poses ?

Answer 9

• The period of exposure. The earlier on the terogen is encountered in the pregnancy the more risk it carried. (3-8 weeks is the greatest risk)
• Dosage
• Genetic constitution of the embryo some are more susceptible to teratogens

Question 10

Suggest some investigations that can be antenatally to find the damage done by a teratogen

Answer 10

Bloods
Ultrasound
Invasive tests such as chronic villus sampling

Question 11

Suggest some investigations that can be postnatally to find the damage done by a teratogen

Answer 11

looking for hip stability, issues with fingers and toes, hearing

Question 12

From what tissue does the respiratory system develop ?

Answer 12

The endoderm

Question 13

Describe the endoderm

Answer 13

It gives rise to the primitive tube which has a hindgut, a midgut and a foregut.

Question 14

Which part of the endoderm does the respiratory system develop from ?

Answer 14

The foregut

Question 15

Describe the development of the respiratory system

Answer 15

The trachea and lung buds grow out from the ventral wall of the primitive foregut and form the lung bud
The foregut will become the oesophagus and the trachea will remain in front of the oesophagus

Question 16

How does the oesophagus and lung bud separate ?

Answer 16

The oesophagotracheal septum develops.

Question 17

What does the lung tissue develop from ?

Answer 17

The mesoderm

Question 18

How does the pleura of the lungs form ?

Answer 18

The splanchnic mesoderm is pushed towards the somatic mesoderm so that they become completely surrounded by both layers.

Question 19

What is the visceral pleura from ?

Answer 19

The splanchnic mesoderm

Question 20

What is the parietal pleura from ?

Answer 20

The somatic layer of the mesoderm

Question 21

Is the pleural cavity complete ?

Answer 21

No because the pleura is still continuous with the heart and the abdomen (peritoneal cavity)

Question 22

What happens to end this continuation ?

Answer 22

A pericardioperitoneal canal
A lateral plate of somatic mesoderm grows and separates the lungs and heart. This is called the pleuropericardial fold and will becomes the pericardium of the heart.

Question 23

What is the Pseudoglandual stage ?

Answer 23

7-17 weeks where the lung structures develop except the respiring parts

Question 24

What are the names of the stages ?

Answer 24

Embryonic 
Pseudoglandual 
Canalicular 
Saccular 
Alveolar

Question 25

What is the canalicular stage ?

Answer 25

17-27 weeks where the formation of the respiratory parts comes i.e. alveolar ducts from and the epithelium starts to differentiate into type 1 and type 11 pneumocytes

Question 26

What is the saccular stage ?

Answer 26

27-40 weeks where there is formation of alveolar sacs, primitive alveoli and surfactant and gas exchange begins

Question 27

What is the alveolar stage ?

Answer 27

32 weeks to 8 years where there is growth of alveoli and alveolar sacs

Question 28

What are the four things which come together to create the diaphragm ?

Answer 28

Septum transversum
Pleuroperitoneal folds
Skeletal muscle
Dorsal mesentery

Question 29

How does the septum transversum create the diaphragm ?

Answer 29

Forms the central tendon

Question 30

How does the pleuroperitoneal folds create the diaphragm?

Answer 30

They are somatic mesodermal folds which grown in from the sides and fuse with the transversum

Question 31

How does the skeletal muscles form the diaphragm ?

Answer 31

it grows in a covers the pleuroperitoneal folds and forms the muscular part of the diaphragm

Question 32

How does the dorsal mesentery help create the diaphragm ?

Answer 32

Attaches the oesophagus to the thoracic wall. It is then covered in skeletal muscle to form the diaphragmatic crura.

Question 33

Name some congenital lung conditions ?

Answer 33

• Tracheoesophageal fistula and oesophageal atresia
• Neonatal respiratory distress syndrome
• Lung agenesis
• Congenital abnormalities of diaphragm

Question 34

Describe Tracheoesophageal fistula and oesophageal atresia

Answer 34

If that oesophagotracheal septum doesn’t develop properly then the child will have a tracheosophageal fistula (TOF) or a Oesophageal Atresia. A fistula is an abnormal passage between 2 epithelialized tubes or surfaces. TOF is a common congenital abnormality. Atresia is a condition in which an orifice or passage in the body is closed or absent.

Question 35

Describe Neonatal respiratory distress syndrome

Answer 35

Neonatal respiratory distress syndrome (Hyaline membrane disease). It is caused by surfactant deficiency and therefore partial collapse of alveoli. Debris consisting of blood elements accumulate which have a glassy (hyaline) appearance. It affects 2% of neonates and makes up 30% of neuronal disease.

Question 36

Describe Lung agenesis

Answer 36

Lung agenesis. This is failure of lung bus to develop/branch (this will have happened on one side otherwise I’m guessing child wouldn’t have been born) it can also happen because there is insufficient mesoderm to allow formation or the presents or teratogens.

Question 37

Describe Congenital abnormalities of diaphragm

Answer 37

Congenital abnormalities of diaphragm development occur as a result of two major defects. 1. the failure of the diaphragm to completely close during development, this is called a hernias. 2. the pulmonary hypoplasia. Hernia is a general term to describe a profusion of an organ through the structure or muscle that usually contains it.