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Home , Foregut, Hepatic diverticulum, Pancreatic bud

EMBRYOLOGY EDIT TABLE OF CONTENTS: LECTURE OBJECTIVES : Development of the 4 •Describe the development of the duodenum.

Development of 6 •Describe the development of the pancreas.

•Describe the development of the small intestine. Development of the small 8 intestine •Identify the congenital anomalies of the small

intestine : Development of the loop 9 •Congenital omphalocele.

Summary 15 •Umbilical hernia.

Mcqs 16 •Meckel’s diverticulum.

Saqs 18 2 to understand the lecture and the development of the alimentary canal in general you should know these little concepts: • The whole GIT tract is developed from . • Primitive gut is gradually patterned into three segments: 1. 2. Midgut 3. • Each segment is supplied by a special artery and give raise to a number of organs as shown bellow.

celiac artery

superior mesenteric artery

supplied by inferior

mesenteric artery 3 Additional slide slide Additional DEVELOPMENT OF THE DUODENUM

<- Stages of th Early in the 4 week, development of the duodenum duodenum, , biliary ducts and develops from: pancreas See the pics: (A-D).

Caudal part of foregut. 4th week 5th week (endoderm)

Cranial part of midgut The junction of the 2 (endoderm) parts of the gut lies just below or distal to the origin of Splanchnic 5th week 6th week mesoderm 4 Congenital anomalies: Duodenal atresia Duodenal stenosis;

• Duodenal loop:

It comes to lie on the The duodenal loop is The duodenal loop is posterior abdominal formed and projected rotated with the wall retroperitoneally ventrally, forming a C- to the right with the developing shaped loop. pancreas. 1- results from failure 1-results from of recanalization incomplete 2- complete occlusion recanalization of of the duodenal lumen duodenum. 3- autosomal recessive 2-partially canalized inheritance

th th During 5 & 6 weeks, the the duodenum Normally lumen of the duodenum is normally becomes degeneration of temporarily obliterated recanalized by the epithelial cells because of proliferation of end of the Bilious occurs vomiting its epithelial cells. embryonic period 5 DEVELOPMENT OF PANCREAS

The pancreas develops from 2 buds arising from the endoderm of the caudal part of foregut: The two pancreatic 1- ventral : which develops from the proximal buds are developed end of (forms the liver & gall bladder). 2- dorsal pancreatic bud : which develops from dorsal wall of duodenum slightly cranial to the ventral bud. ventral Dorsal bud bud duodenum rotates to the right and becomes Uncinate Body C-shaped the ventral process pancreatic bud moves dorsally to lie below Inferior part and behind the dorsal of head of Neck bud pancreas

Tail of pancreas Later the 2 buds fused together and Upper part lying in the dorsal of of head 6 Congenital anomalies:

Anular pancreas; a thin flat band of pancreatic tissue surrounding the second part of the duodenum, causing duodenal obstruction. main is formed from : ● duct of the ventral bud. ● Distal part of duct of dorsal bud. accessory pancreatic duct is derived from: Accessory pancreatic tissue; ● Proximal part of duct of dorsal bud. located in the wall of the stomach or duodenum.

The parenchyma of pancreas is derived from the endoderm of Pancreatic islets pancreatic buds. develops from it

Insuline secretion begins at 5th month of pregnancy. 7 DEVELOPMENT OF THE SMALL INTESTINE •the small intestine is developed from : Caudal Foregut •Caudal part of foregut. Cranial Midgut •All midgut. (supplied by superior mesenteric artery).

MIDGUT LOOP cranial part caudal part

● Distal part of the duodenum ● Lower portion of ileum. (proximal part of duodenum is ● Cecum & appendix. developed from caudal part of ● Ascending colon + foregut) proximal 2/3 of transverse ● Jejunum colon. Cranial Midgut

● Upper part of the ileum Caudal Midgut Cranial Cranial Midgut

STAGES OF DEVELOPMENT OF SMALL INTESTINE: ● Preherniation stage.

● Stage of physiological umbilical hernia.

● stage of rotation of midgut loop.

● Stage of reduction of umbilical hernia.

● Stage of fixation of various parts of intestine. 8 DEVELOPMENT OF THE MIDGUT LOOP

•At the beginning of 6th week, the midgut elongates to form a ventral U-shaped midgut loop.

•Midgut loop communicates with the yolk sac by vitelline duct or yolk stalk.

Midgut loop projects into the umbilical cord …this is called physiological umbilical herniation (begins at 6thw.)

WHY ?! yolk •As a result of rapidly growing liver, kidneys & gut ,so stalk the abdominal cavity is temporarily too small to U-shaped contain the developing rapidly growing intestinal midgut loop loop. 9 This video is highly recommended ROTATION OF THE MIDGUT LOOP to understand this part :)

general Limbs of the • Cranial characteristics of • Caudal the rotation : midgut loop • See fig.A 1- total rotation is 270 degrees (90 in the stage of physiological • 90 degrees see fig.B • Result the cranial limb become on the right and hernia and 180 in the First caudal limb on the left reduction of the • Stage : this event happen during the rotation physiological hernia physiological herniation stage).

2- the rotation axis is • The cranial limb (on the right now )of midgut loop elongates to form the intestinal coiled loops around the superior Fate (jejunum & ileum). See figC mesenteric artery.

3- the rotation is counterclockwise(1). Second • Additional 180 degrees • Stage: reduction of physiological hernia rotation will be explained in 10 the coming slide عكس عقارب الساعة :(1) FIXATION OF VARIOUS PARTS OF RETURN OF MIDGUT TO ABDOMEN: INTESTINE reduction of physiological midgut hernia: 1- it is a stage that the intestines return to the abdomen due to regression of liver & kidneys + expansion of abdominal cavity. 2- happens during the 10th week. 3- Rotation is completed and the 1. At first the mesentry of jejunoileal coiled intestinal loops lie in their loops is continuous with that of the final position in the left side. acending colon. (after 270 degrees) 2. then, the mesentry of ascending colon fuses with the posterior abdominal wall. The caecum: •The caecum at first lies below 3. So the mesentry of small intestine the liver, but later it descends to lie in the right iliac fossa. becomes fan-shaped and acquires a new line of attachment that passes from duodenojejunal junction to the ileocecal junction. 11 FIXATION OF VARIOUS PARTS OF INTESTINE

Intestines after fixation Intestines prior to fixation 4.The enlarged colon presses the duodenum & pancreas against the posterior abdominal wall. C & F 5.Most of duodenal mesentery is absorbed, so most of duodenum ( except for about the first 2.5 cm derived from foregut) & pancreas become retroperitoneal. C & F

Congenital anomalies Congenital Congenital Ileal (Meckel’s) Omphalocele Umbilical Hernia Diverticulum 12 Congenital Congenital Omphalocele Congenital Umbilical Hernia Ileal (Meckel’s) Diverticulum anomaly common type of hernia most common anomalies Definition it is a persistence of herniation The intestines return to It is a small pouch from the ileum, and of abdominal contents into abdominal cavity at 10th may contain small patches of gastric & proximal part of umbilical cord week, but herniate through an pancreatic tissues causing ulceration, imperfectly closed umbilicus bleeding or even perforation

Cause failure of reduction of physiological hernia to abdominal cavity at 10th week. covered by epithelium of the umbilical cord/ by skin & subcutaneous the . tissue.

Notes • Herniation of intestines • The herniated contents are • about 2% -4% of people, more common in occurs in 1 of 5000 usually the greater males • It arises from antimesenteric border of ileum • Herniation of liver & omentum & small intestine. • 1/2 m from ileocecal junction. intestines occurs in 1 of • It protrudes during • inflammed >> causes symptoms that mimic 10,000 crying,straining or appendicitis • accompanied by small coughing • may be connected to the umbilucus by one abdominal cavity • easily reduced through of the following : • 1 - a fibrous cord fibrous ring at umbilicus. • 2 - middle portion forms a cyst • 3 - remain patent forming the fistula • so, faecal matter is carried through the duct into umbilicus.. 13 Congenital Congenital Omphalocele Congenital Umbilical Hernia Ileal (Meckel’s) anomaly common type of hernia Diverticulum most common anomalies

Management Immediate surgical repair is required. Surgery is performed at age of 3-5 years.

14 parts SMALL INTESTINE

DUODENUM JEJUNUM +ILLUME PANCREAS

Origen Duodenal lope from: Mid gut lope from : midgut give the caudal part of foregut: (all from Caudal part of foregut. ventral bud: from proximal end of hepatic endoderm) + Cranial part caudal part diverticulum Cranial part of midgut Part of duodenum lower part of illume dorsal bud: from dorsal wall of duodenum + Jejunum Cecum & appendix. Splanchnic mesoderm. upper part of illume Ascending colon +2/3 of transverse

Notes _____ ..Midgut is supplied by superior mesenteric artery ventral bud forms :Uncinate process. ..Midgut loop communicates with the yolk sac by vitelline duct or yolk stalk. And Inferior part of head ..Midgut loop has a cranial & a caudal limbs dorsal bud forms : Upper part of head, Neck, Body &Tail hepatic diverticulum forms: liver & gall bladder

Changes ..Duodenal lope start as ..Preherniation : ..main duct C shape ventrally  ..physiological umbilical hernia.: As a result of rapidly grow of abdominal components ventral bud duct + distal part of dorsal bud rotate to the right  and small abdominal cavity Midgut loop projects into the umbilical cord duct retroperitoneal .. rotation of midgut loop. around the superior mesenteric artery ..accessory duct Proximal part of dorsal ..Epithelial proliferation total rotation is 270 degrees (90 in the stage of physiological hernia and 180 in the bud duct temporarily obliterated reduction of the physiological herniation stage) ..Pancreatic parenchyma  buds lumen degeneration of .. reduction of umbilical hernia. endoderm epithelial  lumen due to regression of liver & kidneys + expansion of abdominal cavity ..Pancreatic islets  parenchymatous recanalization Caecum location change and descends from below the live to the right iliac fossa. tissue.

.. fixation of various parts of intestine. mesentery of ascending colon fuses with the summary posterior abdominal wall lead the fan-shape of the mesentery of small intestine +duodenum and pancreas fixed on the posterior abdominal wall and retro

Congenital Duodenal stenosis; Congenital Omphalocele Ileal (Meckel’s) Diverticulum Accessory pancreatic tissue; located in anomalies incomplete .. failure of reduction of physiological hernia .. most common anomalies of GIT the wall of the stomach or duodenum. recanalization Duodenal .. small abdominal cavity. ,

 What does duodenal atresia mean? it means congenital occlusion of the duodenal lumen results from failur of recanalization

 Cranial part of the midgut gives rise to? 1-Distal part of the duodenum 2- Jejunum

3- Upper part of the ileum SAQs  TIME LINE : of all events in this lecture:

18 DONE BY . Rana Alhumeamydi . Daa’d Alotaibi . Hadeel Alsulami . Amal Aseeri

. Lenah Alaseem . Sarah m.Aljasser

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