5 Development of the Gastrointestinal tract II Flashcards
How is the primary intestinal loop formed?
Midgut elongates
Runs out of space
Makes loop
Superior mesenteric artery= axis of loop
How is the primary intestinal loop connected to the yolk sac?
Via viteline duct
Why is physiological herniation necessary in the developing embryo?
- Growth of primary intestinal loop= very rapid (6th week)
- Liver growing rapidly
Abdominal cavity to small to accomodate
Intestines herniate into umbilical cord
What does the allantois develop into?
Umbilical cord
How does the midgut (primary loop) rotate?
270 degrees
Axis: superior mesenteric artery
Whilst in umbilical cord
What does the rotation of the midgut achieve?
Fixes structures in place
Transverse colon in front of duodenum
Name two variants of malrotation of the midgut (ie what types of malrotation) and the consequences of these.
(Most complications present in neonatal period)
- Incomplete rotation
- Left-sided colon
- Reversed rotation
- Transverse colon passes posterior to duodenum
What is a volvulus?
A loop of intestine twists around itself and the mesentery that supports it, resulting in a bowel obstruction
What complications can a volvulus cause?
Stangulation
Ischaemia
What conditions can arise if the vitelline persists?
- Vitelline cyst
- Vitelline fistula
- Meckel’s diverticulum
Describe meckel’s diverticulum (ie who does it affect, when is it detected, how much of the population does it affect, where is it, what other tissue can it contain)
RULE OF 2s
-
Who
- 2:1 male:female
-
Where
- 2 feet from ileocaecal valve
-
%
- 2%
-
When detected
- Under 2s
-
Other tissue
- Ectopic gastric
- Pancreatic
What can happen within the primitive gut tube if the cell growth of some stuctures is too rapid?
Lumen partially/completely obliterated
Eg oesophagus, small intestine, bile duct
Recanalisation occurs to restore lumen
If recanalisation unsuccessful: can cause stenosis/atresia
What is pyloric stenosis?
Hypertrophy of circular muscle in region of pyloric sphincter
(NOT recanalisation failure)
Common abnormlaity of stomach in infants- projectile vomiting
What is gastroschisis?
Failure of closure of abdominal wall during folding of the embryo- gut tube and derivatives= outside body cavity
(Usually: isolated defect, prepared for in utero, caesarian= necessary)
What is an omphalocele? (aka exomphalos)
No longer physiological herniation of gut
Label the line in the following image. What is the significance of this division?
Divides superior and inferior part
Different blood supply, innervation and lymphatic drainage
How is the anal canal formed from the hindgut (ie the opening)?
Ectoderm puches up (blue on diagram)
Differentiate between the cell type, blood supply, innervation and lymphatic drainage and sensation felt above and below the pectineal line in the anal canal.
Sensation:
Above: only sensation possible= stretch
Below: temperature, touch, pain
In what region on the body would visceral pain be felt from the foregut, midgut and hindgut.
Name 3 hindgut abnormalities.
- Imperforate anus (failure of anal membrane to rupture)
- Anal/anorectal agenesis
- Hindgut fistulae
Which parts of the midgut and hindgut retain their mesenteries and which structures have fused mesenteries?
The liver grows into the ventral mesentary and divides it into two parts. What are these two parts?
- Falciform ligament
- Lesser omentum
The pancreas is a foregut structure. It develops from a dorsal portion and a ventral portion. Which parts of the pancreas do these portions form?
- Dorsal portion: gland
- Ventral portion: duct system
What are the derivatives of the cranial and caudal limbs of the primary intestinal loop?
What is the most common cause of atresias/stenoses in the:
- Upper duodenum
- Lower duodenum
- Upper duodenum
- Failure of recanalisation
- Lower duodenum
- Vascular accident
- –> caused by : Malrotation, volvulus, body wall defect
- Vascular accident
Summary notes: (may be helpful)
Summary notes: (may be helpful)
