Embryology of Coelomic Cavity and
peritoneum
E-mail: [email protected]
E. mail: [email protected]
Prof. Abdulameer Al-Nuaimi
Anal canal
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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
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
Endoderm
Langman’s Medical Embryology
Sagittal Section
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YOLK SAC
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
Cephalocaudal folding of the Embryo Sagittal sections , the cranial area
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Langman’s Medical Embryology
Parietal mesoderm
Visceral mesoderm
(Langman’s Medical Embryology)
Yolk sac Yolk sac
Yolk sac
4/3/2018
Par Mes
Cross Sect.
Parietal Mesoderm
Visceral mesoderm
Langman’s Medical Embryology)
Lat. Fold
Formation of body wall
Visceral mesoderm
Parietal Mesoderm
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
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
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Yolk sac
Vitelline duct
Posterior abdominal wall
Anterior abdominal wall
Extraperitoneal organ
Partly covered with peritoneum
Intraperitoneal organ
Dorsal mesentery
Ventral mesentery
Dorsal mesentery
Development of Peritoneum and Mesenteries
Peritoneum
Abdominal cavity
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.
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.
Dorsal Mesentery
Ventral Mesentery
Post. Abdominal wall
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Intra peritoneal organ
Extraperitoneal organ
Longitudinal Section Cross section
4/3/2018
4/3/2018
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
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.
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. Liver
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Greater curvature Lesser
curvature
Duodenum
Ventral mesentery Dorsal mesentery
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.
Posterior
Anterior
Spleen
Stomach
Liver
Lt. Kidney
Lienorenal Ligament
Gastrolienal Ligament
Lesser Omentum
Falciform Ligament
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.
Lesser Sac
S S
L L
Omental bursa (Lesser Sac)
Lesser Omentum
Falciform Ligament
Development of Omental bursa (Lesser Sac) www.google.co.uk/search?
Lesser Omentum free margin Contains Portal V., Hepatic Art. and Bile duct
(Lesser Sac)
(Lesser Sac)
Tran. Sec. in the body Long.Sec. Ant. View Less. Sac
L. O
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
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Sagittal Sections
Lesser Omentum
Greater Omentum
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Stomach
Liver Liver
Epiploic Foramen
Falciform Ligament
Anterior view
TMC
Greater Omentum
Les Om
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.
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Falcif Lig.
Lig. Teres
Trans Meso Colon
Anterior views
Epiploic Foramen
C. P. H. Great Omen
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).
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.
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Greater Sac
Lesser Sac
D
TC Mesocolon
Lesser Omentum
Spleen
Greater and Lesser Omentum
Sagittal Section in the abdomen
Anter. view
Liver
Lt. Kidney
Liver
An. Ad. Wall
Pos. A. Wall
Post. Abd. Wall
Ant. Abd. Wall
Lt. Kidney
Spleen Stomach Liver
Diaphragm
Lienorenal lig.
Gastrosplenic Lig.
Lesser Omentum
Falciform
Ligament
Greater Sac
Greater Sac
Umblicus
Dorsal and Ventral Mesenteries of Foregut Prof.Abdulameer Al-Nuaimi
Peritoneum
Umbilical vein
H. A
S
Post. Abd. Wall
Lt. Kidney
Spleen L.
Less. Sac
Dorsal Mesentery
(Greater Omentum)
Liver
Lesser Omentum
Umblicus
Rotation of Stomach
Falciform Lig.
Greater Sac
Prof. Abdulameer Al-Nuaimi
Diaphragm
Umbilical vein
S
Pos. Ad. Wall
Ant. Abd. Wall
Kidney
Spleen
L. Less. Sac
Greater Sac
Greater Omentum
T.C
S.I.
Lesser Omentum
Falciform Lig. Diaphragm www.google.co.uk/search?
L.
Formation of Greater and Lesser Omentums and Sacs Prof. Abdulameer Al-Nuaimi
GS
Greater and Lesser Sac
Parietal peritoneum
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Cross Section in the abdomen
Ant. view
S
G. Om
L L. Om
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.
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