Development Of Midgut And Hindgut Flashcards
How does the midgut start to develop?
Begins as a short tube, elongates enormously until it has run out of space
It then forms a primary intestinal loop
What structures does the midgut give rise to?
Small intestine Caecum Appendix Ascending colon Prox two thirds of transverse colon
PICTURESGive features of the primary intestinal loop
The superior mesentric artery is its axis
It is connected to the yolk sac by the vitelline duct
Has cranial and caudal limbs
Why does physiological herniation occur?
Primary intestinal loop grows so rapidly at he same time as the liver. The abdominal cavity is too small to accommodate them so intestines herniate into umbilical cord
In which week does the physiological herniation occur?
6
PICTURE What happens in the first 90* turn?
The distal part of the gut tube is left and the proximal part is right
PICTURE What happens after the first 90* turn?
The distal part develops a bulge which will become the caecum/caecum bud
The proximal part becomes convoluted
PICTURE How does the midgut return to the abdominal cavity?
Proximal part returns first, passing under the distal part, making the second rotation
The distal limb then returns, making another rotation
What happens in the descent of the cecal bud?
Temporarily lies in the upper right quadrant, just beneath the liver
Descends down the right hand side of the abdominal cavity into the right iliac fossa
It develops a narrow diverticulum - the appendix
Derivatives of the proximal limb of the midgut?
Distal duodenum, jejunum, proximal ileum
Derivatives of the caudal/distal limb of the midgut?
Distal ileum, cecum, appendix, ascending colon, proximal two thirds of the transverse colon
What happens if there is incomplete rotation of the midgut?
When the midgut makes only one 90* rotation, colon and cecum are the first to return causing a left sided colon
What happens if there is reverse rotation?
Midgut makes a rotation clockwise
Transverse colon passes posterior to the duodenum
What is a vitelline cyst?
Caused by persistence of the vitelline duct in the middle but both ends form fibrous strands
A cyst forms in the middle portion
What is a vitelline fistula?
When the whole vitelline duct remains patent over the entire length, forming a direct communication between the umbilicus and intestinal tract.
What is a Meckel’s diverticulum?
When a small portion of the vitelline duct persists, forming an outpocketing of the ileum
When can problems arise in a Meckel’s diverticulum?
If it contains heterotopic pancreatic tissue or gastric mucosa
Can cause ulceration, bleeding, perforation
Give the rule of twos about the Meckel’s diverticulum
2% of population 2ft from ileocoecal valve 2 inches long Detected in under 2s 2:1 male:female
When a Meckel’s diverticulum becomes inflamed, what is the main differential diagnosis?
Appendicitis
What incomplete recanalisation lead to?
Atresia of the tube affected - lumen is obliterated
Stenosis of the tube - lumen is narrowed
What can contribute to the incomplete recanalisation?
‘Vascular accident’
Impairment of blood supply to that part of the tube
Where can incomplete recanalisation occur?
Oesophagus
Bile duct
Small intestine
Duodenum (most common)
What is pyloric stenosis?
Hypertrophy of the circular muscle in the region of the pyloric sphincter NOT A RECANALISATION FAILURE
Clinical presentation of pyloric stenosis?
Projectile vomiting in infants
