1. Embryology of Coelomic Cavity and peritoneum
Prof. Abdulameer Al-Nuaimi
E. mail:

2. Anal canal

3. Gastrointestinal tract
Parts
Blood supply
Components
Foregut
Celiac artery
Pharynx, oesophagus, stomach, proximal half of duodenum and the derivatives (liver, biliary apparatus and pancreas)
Midgut
Superior mesenteric artery
Small intestine (distal half of duodenum, jejunum and ileum), caecum, vermiform appendix, ascending colon and right 2/3 of the transverse colon
Hindgut
Inferior mesenteric artery
Left 1/3 of the transverse colon, descending colon, sigmoid colon, rectum and anal canal
Gastrointestinal tract

4. Oropharyngeal membrane
Located at the cranial end of the embryonic disc, it consists of a small region of tightly adherent ectoderm and endoderm cells, there is no intervening mesoderm, it represents the future opening of the oral cavity
Cloacal membrane
Formed at the caudal end of the embryonic disc
It consists of tightly adherent ectoderm and endoderm cells, there is no intervening mesoderm. When this membrane appears, the posterior wall of the yolk sac forms a small diverticulum, the Allantois which extends into the connecting stalk
Langman’s Medical Embryology
Sagittal Section
YOLK SAC
Endoderm

5. Folding of the embryo
during the fourth week, the embryo passes in cephalocaudal and lateral folding. Folding of the embryo is influenced and directed by the expression of specific genes, in addition to that is the disproportionate growth of different parts of the embryo
The Cranial area of the embryo contains the Oropharyngeal
Membrane, the Cardiogenic area (the heart) and Septum transversum,
Cephalocaudal Folding brings the Oropharyngeal membrane, cardiogenic area and septum transversum ventraly, forming the ventral surface of the future face, neck and chest. It brings the heart into its thoracic position and septum transversum to the diaphragm. Cloacal membrane is brought anteriorly

6. Cephalocaudal folding of the Embryo
Sagittal sections , the cranial area
Langman’s Medical Embryology

7. (Langman’s Medical Embryology)
Parietal mesoderm
Yolk sac
Yolk sac
Visceral mesoderm
Yolk sac

8. Par Mes
2/17/2019

9. Formation of body wall 2019/2/17 Parietal Mesoderm Visceral mesoderm
Cross Sect.
Parietal Mesoderm
Visceral mesoderm
Lat. Fold
Formation of body wall
Langman’s Medical Embryology)

10. The Endoderm gives rise to
The primitive gut is derived from the Endoderm and Visceral Mesoderm as follows
The Endoderm gives rise to
1- Epithelial lining of digestive tract
2- Hepatocytes of liver
3- Endocrine and Exocrine cells of Pancreas
Visceral Mesoderm gives rise to
1-Muscle, Connective tissue and peritoneal components of the wall of the gut
2- Connective tissue for the glands

11. The Primitive gut, is a blind-ended tube and is described as
Foregut, Midgut and Hindgut.
The Midgut, remains connected temporarily to the yolk sac by means of Vitelline duct (yolk stalk)
Foregut extends from Oropharyngeal membrane Liver bud.
Midgut: from Liver bud end of Rt. 2/3 of Transverse Colon.
Hindgut: from beginning of Lt. 1/3 of Transverse Colon Cloacal membrane
Yolk sac
Vitelline duct

12. Development of Peritoneum and Mesenteries
Posterior abdominal wall
Extraperitoneal
organ
Partly covered
with peritoneum
Intraperitoneal
organ
Dorsal mesentery
Abdominal
cavity
Ventral mesentery
Anterior abdominal
wall
Peritoneum
Dorsal mesentery
Development of Peritoneum and Mesenteries

13. Mesenteries
Parts of the gut tube are suspended from the dorsal and ventral body walls by Mesenteries. The latter are double layers of peritoneum that surround the organ and connect it to the body wall, such organ is called intraperitoneal
When an organ is sitting directly on posterior abdominal wall and covered by peritoneum on its anterior surface only, it is called extraperitoneal (retroperitoneal) organ.
Ligaments: are double layers of peritoneum pass from one organ to another or from an organ to the body wall.
Mesenteries and ligaments provide pathway for blood vessels, lymphatics and nerves to go to and come from the abdominal viscera.
Folds and Omenta are other forms of peritoneal layers
By the 5th week, the lower part of the foregut, midgut and major part of hindgut are suspended from posterior abdominal wall by dorsal mesentery.
Dorsal mesentery extends from the lower part of Oesophagus to the Cloacal region.

14. Ventral Mesentery: Is present only in the region of the Foregut (terminal part of the oesophagus, the stomach and the upper part of duodenum). Thus the foregut has a dorsal and ventral mesenteries, while the midgut and hindgut have got only a dorsal mesentery.
The ventral mesentery is derived from Septum Transversum.; its free lower margin contains, the Hepatic art., Portal V. and Bile duct.
Liver develops in the ventral mesentry and divides it into Lesser Omentum and Falciform Ligament.
Post. Abdominal wall
Extraperitoneal
organ
Dorsal Mesentery
Intra peritoneal organ
Ventral Mesentery
Longitudinal
Section
Cross section

15. 2/17/2019

16. A- The point where the oesophagus A
Development of alimentary tract passes in stage of elongation. Most parts increase in length especially between four fixed regions. The points of fixation are GIT
A- The point where the oesophagus A
passes through the developing foregut
diaphragm
B- The point where the proximal B
part of the duodenum lying on Midgut
the posterior abdominal wall
C- The point at junction between C
the mid and hind gut Hindgut
D- The point where the rectum
passes through the pelvic D
Diaphragm
Points of fixation of GIT
Diaphragm
Pelvic diaphragm
2/17/2019

17. Development of Stomach
Stomach appears as a fusiform dilatation in the foregut at age of the 4th week. Its appearance and position changes greatly as a result of the different rate of growth in various regions of its wall and also due to its rotation around a longitudinal and anteroposterior axis.
The stomach rotates 90° in clockwise direction around its longitudinal axis, thus its Lt. side becomes anterior and its Rt. Side becomes posterior.
Simultaneously its nerves also change their position, hence, the Lt. Vagus nerve now is anterior and the Rt. Vagus is posterior.
During this rotation, its left wall grows faster than the right side, this gives rise to the development of Greater and Lesser curvatures.

18. Rotation of stomach around an anteroposterior axis
Upper and lower ends of stomach originally lie in the midline, but during further development, the stomach rotates around anteroposterior axis in a way that its pyloric end moves to the right and upward and its cardiac end moves to the left and slightly downward, thus the stomach axis extends from upper left to lower right.
Ventral mesentery
Liver
Dorsal mesentery
Greater curvature
Lesser curvature
Duodenum
Rotation of Stomach

19. Formation of Lesser Sac (Omental Bursa)
Stomach has dorsal and ventral mesenteries; due to the axial rotation and disproportionate growth of the stomach during the fifth week of development, there is a change in the position of these mesenteries.
Longitudinal rotation pulls the dorsal mesentery to the left and creating a space behind the stomach, this space is called Omental Bursa or Lesser Sac
At the same time, the ventral mesentery is pulled to the right.
The Spleen develops as a mesodermal proliferation in the left layer of the dorsal mesentery of stomach.
With continued rotation of the stomach, the dorsal mesentery of stomach lengthens, and the portion between the spleen and dorsal midline swings to the left and fuses with the peritoneum of the posterior abdominal wall.
The fused two layers (posterior leaf of the dorsal gastric mesentery and the peritoneum covering the posterior abdominal wall) degenerate.

20. Posterior
Lt. Kidney
Lienorenal Ligament
Lesser Sac
Spleen
Gastrolienal Ligament
Stomach
Lesser Omentum
Liver
Falciform Ligament
Anterior
The spleen was connected to the posterior abdominal wall at the midline, but it has changed the position of its connection, it is now connected to the posterior abdominal wall in the region of the left kidney by the mesentery called Lienorenal Ligament and is connected to the stomach by the Gastrolienal ligament.

21. S S L L Development of Omental bursa (Lesser Sac) Omental bursa
Lesser Omentum
Lesser Omentum free margin
Contains Portal V., Hepatic Art.
and Bile duct
Falciform Ligament
L. O
(Lesser Sac)
Less. Sac
Long.Sec.
Ant. View
Tran. Sec. in the body
Development of Omental bursa (Lesser Sac)

22. Formation of Greater Omentum
When the stomach rotates along the anteroposterior axis, the dorsal Gastric mesentery (Mesogastrium) bulges down. It continues to grow down forming a double layered sac in front of transverse colon and small intestine (like an apron).
The four layers of this apron fuse together, forming the Greater Omentum hanging from the greater curvature of the stomach . The posterior layer of the greater omentum also fuses with the mesentery of the transverse colon.
duodenum
mesocolon TC
Sagittal Sections

23. Anterior view Lesser Omentum Greater Omentum Falciform Ligament Liver
Stomach
Epiploic Foramen
Greater Omentum
Anterior view

24. Ventral mesentery of foregut
Epiploic
Foramen
Falcif
Lig.
TMC
Lig. Teres
C. P. H.
Great Omen
Les Om
Trans Meso Colon
Greater
Omentum
Anterior views
Ventral mesentery of foregut
Gives rise to lesser omentum and Falciform Ligament.
The free margin of Falciform ligament contains the umbilical vein which is obliterated after birth to form the Ligamentum Teres.

25. Free margin of Lesser Omentum
contains
1- Common Bile duct
2- Hepatic artery
3- Portal vein
The Free margin of Lesser Omentum forms the anterior boundary of the Epiploic Foramen (Foramen of Winslow), which is the opening connecting the Lesser Sac with the rest of the peritoneal cavity (Greater Sac).

26. Greater Omentum, Lesser Omentum, Greater Sac and Lesser Sac.
Greater Omentum: is part of the dorsal mesentery of stomach, which is hanging down from its greater curvature.
Lesser Omentum: is part of the ventral mesentery of stomach, it is attached superiorly to the liver and to the lesser curvature of stomach inferiorly
Greater Sac: is that part of peritoneal cavity you enter, when you
open the anterior abdominal wall and the parietal peritoneum.
Lesser Sac: is that part of peritoneal cavity, which is trapped behind the stomach and liver.

27. Greater and Lesser Omentum
Liver
Sagittal Section in the abdomen
Liver
Lesser Omentum
Lesser
Sac
Lt. Kidney
Greater Sac D
Spleen
An. Ad. Wall TC
Mesocolon
Pos. A. Wall
Greater and Lesser Omentum
Anter. view

28. Dorsal and Ventral Mesenteries of Foregut
Diaphragm
Ant. Abd. Wall
Greater Sac
Peritoneum
Umbilical vein
Liver
Stomach
Spleen
Lt. Kidney
Umblicus
Falciform
Ligament
Lienorenal lig.
Post. Abd. Wall
Gastrosplenic Lig.
Greater Sac
H. A
Lesser Omentum
Dorsal and Ventral Mesenteries of Foregut
Prof.Abdulameer Al-Nuaimi

29. Falciform Lig. Liver Diaphragm Umblicus Lesser Omentum Less. Sac L.
Spleen
Umbilical vein
Lt. Kidney S
Post. Abd. Wall
Greater Sac
Dorsal Mesentery
(Greater Omentum)
Rotation of Stomach
Prof. Abdulameer Al-Nuaimi

30. Formation of Greater and Lesser Omentums and Sacs
Falciform Lig.
Diaphragm L. L.
Less. Sac
Ant. Abd. Wall
Lesser Omentum
Spleen
Kidney S
Pos. Ad. Wall
Greater Sac
T.C
S.I.
Greater Omentum
Formation of Greater and Lesser Omentums and Sacs
Prof. Abdulameer Al-Nuaimi

31. S L L. Om Greater and Lesser Sac G. Om Ant. view Parietal peritoneumGS
Ant. view L S
L. Om
Cross Section in the abdomen
Greater and Lesser Sac
G. Om

32. Summary
The primitive gut is formed as a result of the folding of the embryo.
Foregut has dorsal and ventral mesentery.
Liver develops in the ventral mesentery and the spleen develops in the dorsal mesentery.
Stomach rotates along two axes, this leads to the formation of lesser and greater omentums, and lesser and greater sacs.

33. passion flower
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