Embryology

Question 1

In the initial stages of embryonic development, what is the position of the septum transversum relative to the primordial heart? How does this position change by day 26 of development?

Question 2

What structure in the embryo contributes to the diaphragm?

Answer 2

Septum transversum (specificlly contributes to the future central tendon of the diaphragm)

Question 3

Somites within the cervical region associated with C3, C4 and C5

Question 4

As myoblasts start migrating towards

Question 5

Which part of the embryo grows at a faster rate? How does this affect the diaphragm?

Answer 5

The dorsal side grows at a faster rate than the ventral side. This causes the diaphragm to move down with respect to the C3, C4, C5 cervical regions.

Question 6

What is the role pf the pleuroperitoneal membranes?

Answer 6

Slowly fuse with the septum transversum, closing up the pericardio-peritoneal canal (close up the space). Muscular tissue from C3, C4, C5 somites follow the membrane and start to replace it. This is the start of the separation of the thoracic cavity from the abdominal cavity.

Question 8

The septum transversum becomes the … of the diaphragm.

Answer 8

central tendon

Question 9

What areas are susceptible to herniation

Question 10

As the pericardio-peritoneal canal gets closed off by the invading pleuroperitoneal membranes, a separation is created between…

Answer 10

the thoracic and abdominal cavity

Question 11

What happens when you fail to create a complete distinction between the abdomen and thorax?

Answer 11

hernia….

Question 12

The intraembryonic coelem will become…

Answer 12

the body cavity

Question 13

The developing gut tube’s wall is made of…

Answer 13

splanchnopleure, i.e. …

Question 14

What is the name of the horseshoe-shaped cavity? What does it become?

Answer 14

Intraembryonic coelom - forms future body cavities (pericardial, pleural and peritoneal cavities)

Question 15

What happens whn the body wall does not “close” properly?

Answer 15

Varying degrees of consequences:
- severe defects (viscera, like the heart or GIT organs, develop outside of the body cavity)
- minor defects (two sides of the sternum do not fuse together, creating a space within the sternum)

Question 16

Where is the pericardial cavity? Where is the peritoneal cavity?

Answer 16

Pericardial: thorax
Peritoneal: abdomen

Question 17

Week 5: What is the development of the heart and lungs like?

Answer 17

Substantial development of the heart, little development of the lungs.

Question 18

Week 6: What is the development of the heart and lungs like?

Answer 18

Distinction is created between the two pleural cavities and the peritoneal cavity (dorsally, ventrally,….)

Question 19

What allows us to form two rather than one cavity for the lungs?

Question 20

Initially, lungs start developing dorsally to the heart. However, over time, the pleural spaces become larger causing the lungs to…

Answer 20

wrap around the heart (move ventrally)?

Question 21

Where are the phrenic nerves?

Answer 21

Directly between the heart (pericardial cavity) and lungs (pleural cavity)

Question 22

What does the entire respiratory system develop from?

Answer 22

Respiratory diverticulum

Question 23

Small grooves start to form within the developing gut tube. Name the one related to the respiratory system

Answer 23

Laryngotracheal groove (opening of the respiratory diverticulum, which is like an outpouching)

Question 24

As the laryngotracheal groove grows larger, …

Question 25

Where is the trachea growing?

Answer 25

In the laryngeal

Question 26

Why is the respiratory and digestive system so tightly connected?

Answer 26

Because the respiratory system develops off of the developing digestive tube

Question 27

What does it mean that the respiratory diverticulum is a blind outpouching?

Answer 27

it is closed

Question 28

What develops between the future espohagus and respiratory bud?

Answer 28

Tracheoesophageal septum (separation of the trachea and esophagus)

Question 29

What happens if there is no proper separation between the trachea and esphagus?

Answer 29

Fistula: abnormal opening between the esophagus and trachea

Question 30

Define atresia

Answer 30

Closure or blind end either of the esophageal or respiratory portion of the tracheoesophageal tube

Question 31

What is the cause of atresia and fistula?

Answer 31

Mutations in the factors involved in embryonic signalling pathways

Question 32

As the diverticulum starts to lengthen, it begins to ...

Answer 32

bifurcate (split into 2)

Question 33

As the bronchial buds grow, they will receive signals to branch into ..

Answer 33

secondary bronchial buds, then tertiary bronchial buds, and so forth all the way into alveolar buds.

Question 34

What can cause the formation of cysts in the lungs?

Question 35

What causes the absence of lung tissue and tracheobronchial tree on one side of the body? What is this condition called?

Answer 35

Complete unilateral pulmonary agenesis

Question 36

What is pulmonary sequestration?

Answer 36

A congenital malformation - non-functional lung forms where it shouldn't

Question 37

What happens if the intestines start herniating through the ..???? cavity?

Answer 37

Lung may not develop correctly - pulmonary hypoplasia (?)

Question 38

During the embryonic phase (weeks 4-6)

Answer 38

- respiratory diverticulum forms - openings at the cuadal and cranial end of ... i.e. oropharyngeal membrane and claucal membrane

Question 39

The oropharyngeal and claucal membranes will give rise to...

Question 40

During the pseudoglandular phase (weeks 5-17)

Answer 40

- Lungs resemble glands histologically - Lungs are not viable yet (not enough capillaries and ??)

Question 41

During the canalicular phase (weeks 16-25)

Question 42

During the terminal sac phase (week 24-fetal)...

Answer 42

- Capillaries surround the alveoli - Surfactant production beginning, preventing the alveoli from collapsing - alveoli thin and develop -

Question 43

What do we call the collapse of alveoli due to lack of surfactant?

Answer 43

Atelectasis

Question 44

Name the 3 factors that affect fetal lung growth

Answer 44

- adequte space in the pleural cavities - adequate amount of amniotic fluid (why?) - fetal breathing movements

Question 45

Explain Potter syndrome

Answer 45

Due to lack of urine production (because kidneys do not develop), there is a substantially lower amount of amniotic fluid circulating in the developing fetus - therefore we won't have proper lung growth because we won't have sufficient pressure.

Question 46

How is urine important of lung development?

Question 47

What are symptoms of Potter syndrome and their underlying cause

Answer 47

Uterus starts shrinking, causing clubbed feet and flattened facial features - pulmonary hypoplasia - fetal growth deficiency