-The duodenum develops from the caudal part of the foregut and cranial part of the midgut . So, it is supplied by branches from both celiac and cranial mesenteric arteries.
-Due to rotation of the stomach, the duodenum rotates to be located in the right side. Anomalies of duodenum: 1-Duodenal stenosis:- Narrowing of the duodenal lumen results from:- a-Incomplete recanalization of duodenum b-It may be caused by pressure from an annular pancreas.
2-Duodenal atresia:- -A short segment of duodenum is occluded due to failure of recanalization of this segment. -In fetus with duodenal atresia , vomiting begins within few hours of birth before ingestion of any fluid -Often there is distension of epigastrium resulting from overfilled stomach and upper duodenum. Liver -The liver appears as a hepatic bud from the ventral aspect of (duodenum) distal end of the foregut. -The hepatic bud is divided into two cranial and caudal. -The cranial part gives liver and hepatic duct while caudal part gives gall bladder and cystic duct. -The hepatic bud directed towards the septum transversum. - The hepatic bud differentiate into hepatic cords which invade the umbilical and vitelline veins of the septum transversum and transforms them into hepatic sinusoids. - The hepatic cords differentiate into the parenchyma and the lining of the bile duct. - The hemopiotic cells , capsule and connective tissue supporting the liver are differentiated from the mesoderm of the septum transversum. Anomalies of liver:- 1-Atresia of gall bladder This results from failure of vacuolization of the gall bladder, consequently the bladder remains atretic i.e solid. 2-Duplication of the gall bladder 3-Atresia of the bile duct
• In which the lumen of the bile duct fails to reopen • The gall bladder and hepatic duct proximal to the atresia are distended and sever jaundec will become obvious after birth.
Pancreas -It originates from ventral and dorsal pancreatic buds which originate from (duodenum) foregut .
-Each bud expands , therefore, the dorsal pancreatic bud gives dorsal pancreas and dorsal pancreatic duct, and the ventral pancreatic bud gives ventral pancreas and ventral pancreatic duct. -Ventral pancreas includes at first two parts which fuse together latter on.
Anomalies of pancreas :- Annular pancreas: - This anomaly occurs when absence of fusion of the two parts of the ventral pancreas . So each part rotates in opposite direction of the other around the duodenum , so the duodenum becomes surrounded by a ring of pancreas → annular pancreas - If it causes slight pressure on the duodenum leads to narrowing . - If it causes strong pressure on the duodenum leads to obstruction of the duodenum.
The midgut -It communicates with yolk sac by vitelline duct. Development of the midgut: A-Formation of U-shaped loop: Rapid elongation of midgut and its mesentery resulting in the formation of primary intestinal loop which consists of: a.Cranial limb: gives distal part of the duodenum, jejunum and proximal part of the ileum. b.Caudal limb: gives distal part of ileum, cecum, ascending colon and proximal two thirds of transverse colon. c.Apex of the loop: remains connected with the vitelline duct.
B-Herniation: Due to increase rate of liver growth, mesonephros and intestinal loop. The intra abdominal pressure increases leading to herniation of the intestinal loop into the umbilical cord. C-Rotation The intestinal loop rotates 270°c anticlockwise along the longitudinal axis of the cranial mesenteric artery. It rotates 90°c during herniation and 180°c during retraction. During rotation the rate of growth of small intestine is more rapid than that of large intestine resulting in , the small intestine becomes longer, narrower and coiled than the large intestine. D-Retraction Due to decrease in rate of liver growth , degeneration of mesonephros and increase in size of abdominal cavity. The intraabdominal pressure decreased leading to retraction of intestinal loop from umbilical cord to the abdominal cavity.
Anomalies:- I- Anomalies in relation to abdominal wall:- Omphalocele:- It results from failure of the intestine to return to the abdomen II- Anomalies in relation to vitelline duct: 1-Vitelline fistula :- - The vitelline duct remains open over its length. thus forming direct connection between umbilicus and intestinal tract. - A fecal discharge may be found at the umbilicus. 2-Vitelline cyst :- -Both ends of vitelline duct transformed into fibrous cord (vitelline ligament) while middle portion forms large cyst , vitelline cyst. 3- Ileal (Meckels) diverticulum :- - Normally vitelline duct becomes oblitrated and disappears completely. Small portion of the duct persists forming
IV-Anomalies in relation to canalization :- 1-Atresia and stenosis of the gut:
-If the failure of canalization of gut is complete lead to atresia , if partially leads to stenosis. -Most commonly in duodenal and ileal regions. -In fetus has the duodenal atresia , vomiting begins within few hours of birth before ingestion of any fluid. -2-Duplication of the intestinal tract:
Hind gut -The hindgut is supplied by caudal mesenteric artery. -It gives distal third of the transverse colon, descending colon and rectum. -The endoderm of hindgut also forms the internal linning of urinary bladder, urethra, vagina in female and prostate and bulbourethral gland in male. Cloaca Division of cloaca:- 1.The mesoderm between rectum and allantois termed cloacal (urorectal) septum extends caudally to come in contact with cloacal membrane dividing. 2.The septum divides the cloaca and cloacal membrane as follow: a-The cloaca→ into dorsal part, the rectum and ventral part which is subdivided into cranial part ( urinary bladder) and caudal part(urogenital sinus). b-The cloacal membrane →into a dorsal part (anal membrane) closes the rectum and ventral part( urogenital membrane) closes the urogenital sinus 1.The anal membrane deepens to form the proctodeum . thenafter, the anal membrane disappears and the proctodeum which becomes the anal canal becomes connected with the rectum. 2.The ventral part which includes the urinary bladder cranially and urogenital sinus caudally. The urinary bladder : - Enlarged and communicated cranially with the allantois by the urachus. - At its caudal end it receives the two common stems of mesonephric ducts and ureters. - A constriction between the bladder and urogenital sinus takes place forming the urethra. - Due to enlargement of the bladder which is endodermal in origin absorbed the common stem which is mesodermal in origin - Consequently, the bladder has four openings. two upper openings of the ureters which are a part of each other - The four openings form a triangle , trigoneum viscae which is smooth . It represents the absorbed common stems which are mesodermal in origin in the bladder which is endodermal in origin . The urogenital sinus : - In female it forms the vaginal vestibule. - In male it subdivided into pelvic and phallic part which give rise the pelvic and the penile urethra respectively. - In male the prostate and bulbourethral gland originate from the urogenital sinus.
Anomalies of cloaca:- 1-Persistant anal membrane ( imperforated anus) The anal membrane persists as a diaphragm between the anal canal and rectum. 2-Rectal fistula: Failure in subdivision of the cloaca leads to communication between the rectum and underlying structures. In female→ Rectivaginal fistula between rectum and vagina . The fecal matter observed in vagina . In male → 1-Rectovesicular fistula 2-Rectourethral fistula
3-Rectal atresia : Means absence of the caudal part of the rectum. 4-Anal atresia : absence of the proctodeum. 5-Anal stenosis ( Microscopic anus) -The anal canal is very narrow Thanks