Development of alimentary (digestive) system Flashcards
What is gastrulation?
A single layered blastula –> trilaminar gastrula forming the 3 germ layers
What are the 3 germ layers?
Ectoderm, mesoderm and endoderm
What are the general components of the alimentary system and where does it run from?
Mouth to anus (the tract) with associated glands and organs eg liver, gallbladder, pancreas
What week does the primordial gut from?
Week 4
What are the 2 ends of the primordial gut called and what end is broader?
Cranial and caudal with the cranial end being broader
What is the cranial end of the primordial gut closed by?
Oropharnygeal membrane
What is the caudal end of the primordial gut closed by?
Cloacal membrane
As the head and tail folds what part is taken in by the embryo?
Yolk sac
Name the 3 parts of the primordial gut tube
foregut, midgut and hindgut
What part of the primordial gut forms most of the gut, epithelium and glands
Endoderm
What does the intraembryonic coelom give rise to?
Embryonic body cavity
What will the embryonic cavity give rise to?
Peritoneum, pericardium and pleural cavities
What are the constituents of the foregut?
Primordial pharynx, LRT, oesophagus, stomach, duodenum, liver, biliary apparatus and pancreas
What does the tracheoesophageal ridge divide?
Divides the trachea and oesophagus
Oesophageal atresia is due to what?
The oesophagus not growing properly
Failure of recanlization
What is polyhydraminios
The accumulation of excess amniotic fluid
What is a tracheosophageal fistula?
Trachea and oesophagus communicate due to the abnormal deviation of septum
What degrees and in which direction does the stomach rotate?
90, clockwise
What is the dorsal mesogastrium?
The portion of the dorsal mesentery attached to the greater curvature of the stomach
What does the dorsal mesogastrium develop into?
Greater omentum
When the stomach rotates to the left, a space is made behind the stomach? What does this become?
Lesser omentum/ omental bursa
What nerves supply the liver?
vagus (left and right)
What is hypertrophic pyloric stenosis?
When the child will vomit everything up as the pyloric sphincter is enlarged
What are some common causes of hypertrophic pyloric stenosis?
monozygotic twins
Higher in males
Genetics
What does the hepatic diverticulum give rise to?
Liver - sinusoids and vessels
Briefly describe 2 anomalies of the liver
Accessory hepatic ducts
Extra hepatic biliary atresia - obliteration of bile ducts
How do the 2 buds of the pancreas join?
Ventral and dorsal buds join due to the rotation of the stomach
Which parts of the pancreas do the ventral and dorsal buds make?
Head
most of pancreas
What is annular pancreas?
The ventral bud fails to migrate around the duodenum properly causing stenosis
What is accessory pancreatic tissue?
Pancreatic tissue in other parts of the foregut
What week does the dorsal mesogastrium develop?
week 4
What week does the mesenchyme form the spleen?
week 5
Is the spleen mesodermal or endodermal derivative?
mesodermal
Name the parts of the midgut
Duodenum (distal part), jejunum, ileum, caecum, appendix, ascending colon, proximal 2/3 transverse colon
State the 4 stages of the midgut looping
Herniation, rotation, retraction and fixation
What kind of herniation is involved in gut looping and briefly explain
The midgut herniates into the umbilical cord (yolk sac)
What degrees does the midgut loop in umbilical cord?
90 degrees counter clockwise
What degrees does the midgut loop retract?
180 degrees counterclockwise
What degrees does the stomach and midgut loop rotate?
90 degrees clockwise
270 degrees anticlockwise
What is formed if the vitelline duct persists?
Meckel diverticulum due to narrowing of ileum lumen
What can form from the persistence of the vitelline duct?
fistula, vitelline cyst/ ligament
What does the vitelline duct join?
Yolk sac to midgut lumen
What is omphalocele?
The herniation of abdominal viscera through an enlarged umbilical ring due to the failure of retraction of herniated loops
What organs are often involved with omphalocele?
Liver, stomach and intestinal loops
What are the organs protruding in omphalocele enclosed by?
Amnion layer covering the viscera
What is gastroschisis?
A muscular defect with the herniation of abdominal contents through the body wall into the amniotic cavity
What causes gastrochisis and what are the thought causes?
The contents are returned to the abdomen but enter back into the umbilicus
Cocaine and tobacco use
Name the parts of the hindgut
distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum, upper part of anal canal
What does the endoderm of hindgut also go on to make?
Bladder and urethra lining
What is the cloaca?
The expanded terminal part of the hindgut and endoderm lined chamber
What is the allantois?
The ventral part (diverticula) of the cloaca
What is the cloacal membrane?
Separates cloaca and anal pit
What week does the cloacal membrane rupture?
End of week 7 for an opening
What is the job of the urorectal septum?
To divide the rectum and bladder
hindgut and urogenital sinus
The proliferation of what causes the closing of the claudal end?
Ectoderm of anal canal
When does the anal canal reopen?
week 9
What is imperforate anus?
When the anal membrane fails to break down
