3.1 Development Of The Gut 3 + 4 Flashcards
Wha does the midgut give rise to?
- Small intestine, including most of duodenum
- Caecum & appendix
- Ascending colon
- Proximal 2/3 transverse colon
How is the primary intestinal loop formed?
The midgut elongated enormously and runs out of space.
Makes a loop with the superior mesenteric artery as its axis.
When does physiological herniation occur?
6th week
Why does physiological herniation occur?
Rapid growth and elongation of the primary intestinal loop
Rapid growth of liver
Abdominal cavity is too small to accommodate both
Intestines herniate into the umbilical cord.
Briefly describe the rotation of the midgut
Midgut has a cranial and caudal end with the SMA as the axis
Goes through 3 counter clockwise 90 degree rotations
Caudal derivates end up lying to the right of cranial derivates
Transverse colon lies above the duodenum
What are common developmental defects associated with the midgut?
Malrotation Reversed rotation Remnants of yolk sac Meckel’s diverticulum Recanalisation Atresia’s and stenoses Pyloric stenosis
What occurs in malrotation of the midgut?
Midgut loop only makes one 90 degree rotation
Results in a left sided colon
What occurs in reversed rotation of the midgut?
- Midgut loop makes one 90° rotation clockwise
* Transverse colon passes posterior to the duodenum
What are developmental problems associated with rotation of the midgut?
Reversed rotation
Malrotation
What abnormalities can occur as a result of a persistent vitelline duct?
Vitelline cyst
Vitelline fistula
Meckel’s diverticula
What is a vitelline fistula?
Direct communication between the umbilicus & intestinal tract
What is the rule of 2s of meckel’s diverticulum?
2% of population
2 feet from ileocaecal valve
Usually detected in under 2s
2:1 ratio male:female
What happens if recanalisation of the gut lumen is partially or wholly unsuccessful?
Atresia - lumen obliterated
stenosis - lumen narrowed
Where do problems with recanalisation usually occur?
Duodenum
What is pyloric stenosis?
hypertrophy of the circular muscle in the region of the pyloric sphincter
In who is pyloric stenosis usually seen?
In infants
What are the characteristic symptoms of pyloric stenosis?
Projectile vomiting
Dysphagia
What are common defects of the anterior abdominal wall?
Gastroschisis
Omphalocele
What is gastroschisis?
- Failure of closure of the abdominal wall during lateral folding of the embryo
- Leaves gut tube & derivatives outside the body cavity
What is omphalocele?
a.k.a. exomphalos
Persistence of physiological herniation, midgut structures remain in umbilical cord. Herniation occurs through the umbilical ring
What structures derive from the hind gut?
- Distal 1/3 transverse colon
- Descending colon
- Rectum
- Superior part of anal canal
- Epithelium of urinary bladder
What divides the superior and inferior parts of the anal canal?
Pectinate line
How does the superior anal canal differ from the inferior anal canal?
Arterial supply, venous drainage, lymphatic drainage, innervation, epithelium type
Describe the structure and neuromuscular supply of epithelium above the pectinate line?
inferior mesenteric artery
S2 S3 S4 pelvic parasympathetics - vague pain due to stretch
Columnar epithelium
Lymph drainage via the internal iliac nodes
- derived from endoderm
