- Describe the embryological basis of tracheo-oesophageal fistulas and associated complications
- Tracheo-oesophageal fistulas form when the tracheoesophageal folds fail to fuse. If they would fuse normally, they would form the tracheoesophageal septum, which separates the trachea from the oesophagus.
- Complications
- Aspiration
- Pneumonitis
- Polyhydraminos
- Regurgitation
- Drooling
- Name the congenital abnormalities of the anterior abdominal wall and state their respective embryological basis
- Congenital omphalocele: The mesodermal and abdominal components of the abdominal wall fail to grow causing the umbilical herniation to persist
- Gastroschisis: The lateral body folds fail to fuse causing gastric contents to be extruded through the anterior abdominal wall
- Bladder Extrophy: Mesoderm fails to migrate between the ectoderm and endoderm of the inferior abdominal wall. This causes the inferior abdominal wall to fail to fuse.
- Cloacal Extrophy: The mucous membrane of the bladder ruptured before the cloacal membrane ruptures. This results in the posterior bladder wall being exposed.
- Ectopia cordis: Lateral body walls fail to fuse during the 4th week. This causes non-fusion of the sternum and an open pericardial sac.
- Umbilical hernia: Intestines reherniate into the umbilicus after the 10th week
- Briefly describe the development of the stomach
- The stomach develops from the foregut.
- The foregut dilates into a fusiform shape at week 4, representing the stomach primordia
- The dorsal border of the dilation enlarges and elongates faster than the ventral border. This forms the greater and lesser curvatures respectively 2 weeks later.
- The stomach rotates 90 degrees clockwise (viewed cranially) causing:
- the lesser curvature to move to the right
- the greater curvature to move to the left
- the left side to become the ventral surface
- the right side becomes the dorsal surface
- the cranial end moves left and inferior to the median plane, and the caudal end moves right and superior
- The Omental bursa forms as the mesenteries are carried to the left during rotation
- Describe the axes of rotation of the stomach and state the respective outcomes
- Longitudinal axis: 90 degrees of rotation
- Right side faces posteriorly
- Left side faces anteriorly
- Lesser curvature to the right
- Greater curvature to the left
- Forms the omental bursa by pulling the dorsal mesogastrium to the left and ventral mesogastrium to the right
- Anteroposterior axis
- Pyloric portion moves to the right and upwards
- Cardiac portion moves to the left and slightly downwards
- Longitudinal axis: 90 degrees of rotation
- Describe the embryological basis of annular pancreas and associated clinical complications
- The bifid ventral pancreatic bud forms and envelopes the duodenum. It then fuses with the dorsal bud forming a ring
- Complications
- Duodenal constriction
- Duodenal obstruction
- Associated with: Down syndrome, Intestinal malrotation, Cardiac defects
- Describe how physiological herniation and retraction of the midgut occurs
- Physiological herniation of midgut loop
- The midgut elongates and forms a U-shaped midgut loop that extends into the extraembryonic coelom of the proximal umbilical cord during the beginning of the 6th week
- The loop communicates with the yolk sac via the omphaloenteric duct until week 10, and is attached to the dorsal abdominal wall via the dorsal mesogastrium
- Herniation occurs because of limited space in the abdominal cavity to accomodate the rapidly growing midgut
- Rotation of midgut loop
- The loop rotates 90 degrees anticlockwise around the axis of the SMA bringing the cranial limb (small intestines) to the right and the caudal limb (large intestines) to the left. Cranial limb elongates to form the small intestines.
- Retraction of midgut loop
- reduction of the midgut hernia occurs during week 10
- Retraction occurs due to enlargement of the abdominal cavity and relative decrease in the size of the liver and kidneys
- Small intestines retract first passing posterior to the SMA to occupy the central abdomen
- Large intestines retract and rotate 180* counterclockwise causing the descending and sigmoid colon to move to the right
- Physiological herniation of midgut loop
- What is the embryological basis of the following congenital anomalies: omphalocele, gastrocschisis, meckel’s diverticulum, apple peel atresia
- Omphalocele The mesodermal components of the anterior abdominal wall fail to enlarge causing the midgut loop to be persistently herniated at the umbilicus
- Gastroschisis Extrusion of gastric contents due to failed fusion of lateral body wall folds
- Meckel’s diverticulum
- Persistent proximal vitelline duct
- Apple peel atresia Atresia of the intestines caused by fetal vascular accident ie. Ischemia
- Describe the development of the midgut
- Physiological herniation of midgut loop
- The midgut elongates and forms a U-shaped midgut loop that extends into the extraembryonic coelom of the proximal umbilical cord during th ebeginning of the 6th week
- The loop communicates with the yolk sac via the omphaloenteric duct until week 10, and is attached to the dorsal abdominal wall via the dorsal mesogastrium
- Herniation occurs because of limited space in the abdominal cavity to accomodate the rapidly growing midgut
- Rotation of midgut loop
- The loop rotates 90 degrees anticlockwise around the axis of the SMA bringing the cranial limb (small intestines) to the right and the caudal limb (large intestines) to the left. Cranial limb elongates to form the small intestines.
- Retraction of midgut loop
- reduction of the midgut hernia occurs during week 10
- Retraction occurs due to enlargment of the abdominal cavity and relative decrease in the size of the liver and kidneys
- Small intestines retract first passing posterior to the SMA to occupy the central abdomen
- Large intestines retract and rotate 180* counterclockwise causing the descending and sigmoid colon to move to the right
- Physiological herniation of midgut loop
