Embryology: Development of the midgut and hindgut Flashcards Preview

ESA 3 > Embryology: Development of the midgut and hindgut > Flashcards

Flashcards in Embryology: Development of the midgut and hindgut Deck (9)
Loading flashcards...
1
Q

What physiological herniation occurs during the 6th week?

A

During the 6th week the growth of the primary intestinal loop is very rapid and the liver also grows rapidly
The abdominal cavity is too small to accommodate both so the intestines herniate into the umbilical cord

2
Q

What occurs to the midgut whilst it is herniated into the umbilical cord?
What consequences can occur if this process is abnormal?

A

It undergoes 3 90 degree anticlockwise rotations then returns to the abdominal cavity

  • if there is only 1 rotation the colon is all located on the left side
  • if there is only 1 rotation and it occurs clockwise then transverse colon passes posterior to the duodenum
3
Q

What is the vitelline duct?

A

A long narrow tube that joins the yolk sac to the midgut lumen of the developing fetus - it usually regresses
If it persists:
- failure of the duct to close is termed a vitelline fistula
- can also get Meckel’s diverticulum, which is situated about two feet above the ileocecal junction and may be attached by a fibrous cord to the abdominal wall at the umbilicus

4
Q

In what structures does recanalisation occur?

A

Sometimes cell growth is so rapid the lumen can become partially or completely blocked
Recanalisation then occurs to restore the lumen - this occurs in the oesophagus, bile duct and small intestine

(if recanalisation is unsuccessful there can be atresia or stenosis of the structure)

5
Q

What is the difference between atresia and stenosis?

A

Atresia - lumen completely blocked

Stenosis - lumen is narrowed

6
Q

What causes pyloric stenosis and how does this present?

A

Pyloric stenosis is due to hypertrophy of the circular muscle of the pyloric sphincter (not a recanalisation failure)
Causes characteristic projectile vomiting in infants

7
Q

What is the pectinate line of the anal canal?

A

Divides the upper 2/3rds and lower 1/3 of the anal canal

Above pectinate line: inferior mesenteric artery supply, has columnar epithelium, supplied by S234 pelvic parasympathetics
Below pectinate line: supplied by pudendal artery, has stratified squamous epithelium, supplied by S234 pudendal nerve

8
Q

What is the cloaca separated into?

A

A wedge of mesoderm grows down into the cloaca and divides it into the urogenital sinus and anorectal canal

9
Q

What is the fate of the dorsal and ventral mesenteries?

A

Dorsal mesentery becomes: greater omentum, ligaments from stomach to spleen and spleen to kidney, mesocolon
Ventral mesentery becomes: lesser omentum, falciform ligament which connects liver to ventral wall

Decks in ESA 3 Class (96):