Session 3 - Embryology II / Anatomy Flashcards
During the 6th week, the very speedy growth of the midgut results in..
Herniation of the primary intestinal loop into the umbilicus
What does the primary intestinal loop rotate around?
SMA
What are the starting positions for rotation of the primary intestinal loop?
Cranial end (future SI) is superior, caudal end (future TC) is inferior
By how much does the primary intestinal loop rotate and in which direction
Anticlockwise 270 degrees
What is incomplete rotation
Only rotates one rotation, gets stuck at stage with SI on right and colon on left
What is reversed rotation
One clockwise rotation and TC ends up behind the duodenum
Midgut defects are associated with…
volvulus
What is the vitelline duct
Connects primary intestinal loop to yolk sac
Most common congenital SI abnormality?
Meckel’s diverticulum (2% of pop)
What is Meckel’s diverticulum
Outpouching of vitelline duct that has not fully regressed so it looks like a bulging out of the SI. Often has stomach or pancreas cells in it, produce things that form ulcers, it bleeds.
Name three abnormalities associated with the vitelline duct
Vitelline cyst, vitelline fistula, Meckel’s diverticulum
What is a vitelline cyst
Cystic remnant of vitelline duct, has fibrous band connecting to abdo wall
What is a vitelline fistula
Open vitelline duct, communciation between SI and umbilicus
What is pyloric stenosis (+one symptom)
Hypertrophy of pyloric sphincter, projectile vom
Why is recanalisation important in gut growth
During gut growth it can grow so fast that the lumen disappears (in oesophagus, bile duct and SI). Need recanalisation to restore it- if wholly/partly unsuccessful then atresia or stenosis
Where does atresia/stenosis occur most commonly after failed recanalisation?
Duodenum
Compare contrast omphalocele and gastroschisis
Omphalocele- herniation of midgut within parietal peritoneum into umbilical cord persists outside the body, covered with sac
Gastroschisis- congenital defect in abdominal wall so guts herniate out, have no sac and in contact with amniotic fluid so get oedematous and inflamed
Omphalocele is persistance of physiological herniation, whereas gastroschisis is a defect, failure of abdo wall to fuse.
What’s an umbilical hernia?
Gut pushes through weak region near umbilicus, but covered with skin and subcute tissue, doesn’t get far
What divides the anal canal into 2 parts?
The pectinate line
Another name for the anal pit..
Proctodeum
Why do above and below the pectinate line have different features
One comes from the proctodeum (ectoderm) and one comes from the hindgut (endoderm)
What is the blood supply below and above the pectinate line
Above is IMA, below is pudendal artery
Describe epithelium above and below pectinate line
Above is columnar, below is stratified
Describe nerve supply above and below pectinate line
Above is pelvic parasympathetics, below is pudendal nerve
