4.2 Development of the Midgut and Hindgut Flashcards
(27 cards)
What occurs in physiological herniation?
The growing midgut and liver cannot both fit in the abdominal cavity so the intestinal loop herniates into the umbilical cord
Describe midgut rotation
The midgut rotates 90 degrees anticlockwise when herniated
It then turns another 180 degrees as it reenters the abdominal cavity.
How does the cecal bud form?
The cranial limp of the primary intestinal loop reenters the cavity first and moves to the left. Once inside the cecal bud drops to form the ascending colon
What does the cranial limb of the primary intestinal loop become?
Distal duodenum, jejunum, proximal ileum
What does the caudal limb of the primary intestinal loop become?
Distal ileum, cecum, appendix, ascending colon, proximal 2/3rd of descending colon
What happens if the midgut only rotates 90 degrees?
The colon is on the left hand side
What happens if the midgut rotates in the opposite direction 90 degrees?
The transverse colon passes posterior to the duodenum
What is a volvulus of the bowel?
Twisting or compression of the bowel which results in strangulation and ischaemia.
What is a vitelline cyst?
The vitelline duct forms fibrous strands with the patent middle section
What is a vitelline fistula?
Direct communication between the umbilicus and the intestinal tract
What is Meckel’s diverticulum?
A small diverticulum of the bowel
2 feet from ileocecal valve, 2 inches long, detected in under 2s, 2:1 ration in men to women
Can contain ectopic pancreatic or gastric tissue which becomes inflamed.
What is recanalisation?
In growth, some structures close due to the rapid growth. Recanalisation is the reopening of these structures
What are the two consequences of failed recanalisation?
Atresia- complete failure to open
Stenosis- narrow lumen
What is pyloric stenosis?
Hypertrophy of the circular muscle around the pyloric sphincter. Characterised by projectile vomiting
What is gastroschisis?
Failure of closure of the abdominal wall during embryo folding which leaves the gut tube outside of the body
What is omphalocoele?
Persistance of physiological herniation so the gut is outside the body but covered in a layer of amnion
What is the cloaca?
The end part of the hindgut and the urinary tract
Above the pectinate line:
i. ) What is the blood supply?
ii. ) What type of epithelia is present?
i. ) Inferior mesenteric artery
ii. ) Columnar
Below the pectinate line:
i. ) What is the blood supply?
ii. ) What type of epithelia is present?
i. ) pudendan artery
ii. ) Stratified
How does sensation alter on either side of the pectinate line in the anus?
Above the line the only sensation that can be felt is stretch. Below the line, the tissue is sensitive to temperature, touch and pain.
What is an imperforate anus?
Failure of anal membrane to perforate
What is anal/anorectal agenesis?
Anus does not form
What is a hindgut fistula?
An abnormal connection between the hindgut and the bladder
Where is viceral pain of the foregut felt?
Epigastrum
