Embryology 1

Question 1

What structures comprise the alimentary canal?§

Answer 1

Mouth to anus - including all associated glands and organs

Question 2

At what week of development does the primordial gut form?

Answer 2

4th

Question 3

Which membranes enclose the primordial gut at its cranial and caudal end respectively?

Answer 3

Cranial - oropharyngeal membrane

Caudal - cloacal membrane

Question 4

What is the process of gastrulation?

Answer 4

Formation of trilaminar disc (echo, end and mesoderm)

Question 5

What three regions is the primordial gut divided into?

Answer 5

Foregut, midgut and hindgut

Question 6

What does the endoderm of the primordial gut form?

Answer 6

Most of the gut, epithelium and glands

Question 7

Epithelium from the cranial and caudal end of gut are derived from what two structures? Give specific names

Answer 7

Ectoderm (stomodeum) and anal pit (proctodeum)

Question 8

What forms the embryonic body cavity at the forth week of development?

Answer 8

Intraembryonic coelom

Question 9

The embryonic body cavity divides into what three well defined structures?

Answer 9

Pericardial and peritoneal cavity plus two pericardia-peritoneal canals

Question 10

What are the derivative structures of the foregut?

Answer 10

Primordial pharynx
Lower resp. tract
Oesophagus and stomach 
Duodenum
Liver and biliary apparatus (including pancreas)

Question 11

What is the pharynx?

Answer 11

Space in the throat which is a shared for both digestive and respiratory systems

Question 12

What is the duodenum?

Answer 12

Proximal tubing of intestines to the stomach where bile is secreted

Question 13

What is oesophageal atresia?

Answer 13

Congenital non-seperation/blockage/extensive narrowing of oesophagus

Question 14

What is abnormal deviation of trachea-oesophageal septum called?

Answer 14

Oesophageal fistula

Question 15

What is polyhydramnios?

Answer 15

Too much amniotic fluid around the foetus, sue to atresia

Question 16

Outline the main events in the development of the stomach

Answer 16

• Rotation of stomach (90 degrees clockwise)

- Mesenteries of stomach and mental bursa (lesser sac) develop

Question 17

What is hypertrophic pyloric stenosis?

Answer 17

Overgrowth of the pyloric sphincter (opening from stomach into duodenum)

Question 18

What is the prevalence of hypertrophic pyloric stenosis?

Answer 18

1 in 150 for males

1 in 750 for females

Question 19

What are potential causes for hypertrophic pyloric stenosis? What evidence supports it?

Answer 19

Genetic factors (high presence in monozygotic twins)

Question 20

What is the only treatment for hypertrophic pyloric stenosis?

Answer 20

Surgery

Question 21

Outline the development of the liver and biliary apparatus?

Answer 21

Hepatic diverticulum septates… thats about it so far

Question 22

What anomalies of the hepatic system are possible?

Answer 22

Accessory hepatic ducts (5% of population) and extrahepatic biliary atresia (obliteration of the bile ducts)

Question 23

What occurs if the ventral bus fails to migrate around the duodenum correctly?

Answer 23

Annular pancreas

Question 24

Describe accessory pancreatic tissue?

Answer 24

Pancreatic tissue may form in other areas of the foregut

Question 25

Explain the origins and development of the spleen

Answer 25

End of the 4th week a mesenchymal condensation develops forming the dorsal mesogastrium

During the 5th week the mesenchyme differentiates into spleen tissue

Question 26

What laminar disc does the spleen develop from?

Answer 26

Mesoderm

Question 27

Outline the main events of the midgut loop

Answer 27

• Herniation (physiological umbilical herniation)
• Rotation of midgut 90 degrees anticlockwise in the umbilical cord
• Retraction of intestinal loops - 180 degrees more anticlockwise rotation
• Fixation of intestines

Question 28

In what percentage of people does the small vitelline duct persist?

Answer 28

2-4%

Question 29

What does a persistent vitelline duct form?

Answer 29

Merkel diverticulum

Question 30

What complications can raise from a persistent vitelline duct?

Answer 30

Fistula or cyst

Question 31

What is omphalocele?

Answer 31

Herniation of abdominal viscera through an enlarged umbilical ring

Question 32

What visceramay an omphalocele include?

Answer 32

Herniation of liver, stomach and intestinal loops

Question 33

What covers the viscera of an omphalocele?

Answer 33

Amnion

Question 34

What is amnion?

Answer 34

A membrane which closely covers embryo

Question 35

What is herniation of abdominal contents directly through the body wall into the amniotic cavity called?

Answer 35

Gastroschisis

Question 36

What are suggested causes for rising prevalence in births with babies afflicted with gastroschisis, especially from young women?

Answer 36

Cocaine use

Question 37

What is the prevalence of gastroschisis not associated with?

Answer 37

Chromosomal defects

Question 38

What structures comprise the hindgut?

Answer 38

Distal third of transverse colon, descending colon, sigmoid colon, rectum and upper part of anal canal

Question 39

What does the endoderm of the hindgut also form?

Answer 39

The lining of the bladder and urethra

Question 40

What is the cloaca?

Answer 40

The expanded terminal part of the hindgut and endoderm lined chamber

Question 41

What is the allantois?

Answer 41

The ventral diverticula of cloaca

Question 42

What is the function of the cloacal membrane?

Answer 42

Separates cloaca and the anal pit

Question 43

Describe the partitioning of the cloaca

Answer 43

1. Week 7 - the cloacal membrane ruptures (opening for hindgut)
2. Ectoderm proliferates at the anal canal and closes caudal end
3. Week 9 - anal canal re-opens

Question 44

List hindgut developmental anomalies

Answer 44

Urorectal fistula
Rectovaginal fistula
Rectoanal atresia
Imperforate anus