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Embryology of Coelomic Cavity and
peritoneum
Prof. Abdulameer Al-Nuaimi
E-mail: [email protected]
E. mail: [email protected]
Anal canal
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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
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
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YOLK SAC
Endoderm
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
Langman’s Medical Embryology
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(Langman’s Medical Embryology)
Parietal mesoderm
Yolk sac
Visceral mesoderm
Yolk sac
Yolk sac
Lateral folding resulted in the incorporation of a portion of
the yolk sac (which is lined with endoderm) into the embryo
to form the primitive gut. Parietal mesoderm forms the
peritoneum. The remaining part of the yolk sac and Allantois
remain outside the embryo.
Par. Mes Amn. cavity
Amn. cavity
Amn. cavity
Amn
Mem
GIT
peritoneum
Yolk sac
Cross section
YS
Cross section
Cross section
Peritoneal cavity
Foregut
Midgut
Embryo
Hindgut
Chor. Cav.
Allantois
Heart
Longitudinal sections
Umblical cord
Longtud. Sect www.google.co.uk/search?
Parietal Mesoderm
Visceral mesoderm
Cross Sect.
Parietal Mesoderm
Visceral mesoderm
Lat. Fold
Formation of body wall
Langman’s Medical Embryology
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
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
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Liver bud.
Vitelline duct
Posterior abdominal wall
Extraperitoneal Partly covered
organ
with peritoneum
Intraperitoneal
organ
Dorsal mesentery
Abdominal
cavity
Ventral mesentery
Anterior abdominal
wall
Peritoneum
Dorsal mesentery
Development of Peritoneum and Mesenteries
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.
Post. Abdominal wall
Extraperitoneal
organ
Dorsal Mesentery
Intra peritoneal
organ
Ventral Mesentery
Cross section
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Longitudinal
Section
GIT
Diaphragm
Anterior abdominal
wall
Ventral
Mesentery
L
Dorsal
mesentery
Foregut
Lesser Omentum
Falciform ligament
Umbilical vein
S
------------------
Umbilicus
Bile duct, Hepatic
art. and. Portal vein
Mid gut
-----------------Hind gut
5/3/2017
Pelvic diaphragm
K
Posterior abdominal
wall
Development of alimentary tract passes in stage of
elongation. Most parts increase in length especially between
four fixed regions. The points of fixation are DiaphragmGIT
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
Pelvic diaphragm
Diaphragm
Points of fixation of GIT
5/3/2017
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.
Ventral mesentery
Dorsal mesentery
Liver
Lesser
curvature
Greater
curvature
Duodenum
Rotation of Stomach
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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 anterior 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
Lt. Kidney
Spleen
Stomach
Liver
Lesser Sac
Lienorenal Ligament
Gastrolienal Ligament
Lesser Omentum
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.
Omental bursa
(Lesser Sac)
(Lesser Sac)
S
L
Lesser Omentum free margin
Contains Portal V., Hepatic Art.
and Bile duct
S
L
Lesser Omentum
Falciform Ligament
L. O
(Lesser Sac)
Less. Sac
Tran. Sec. in the body
Long.Sec.
Development of Omental bursa (Lesser Sac)
Ant. View
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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.
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duodenum
TC mesocolon
Sagittal Sections
Falciform Ligament
Liver
Liver
Lesser Omentum
Stomach
Epiploic Foramen
Greater Omentum
Anterior view
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Falcif
Lig.
Epiploic
Foramen
TMC
Lig. Teres
Great Omen
C. P. H.
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.
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.
Liver
Sagittal Section in the abdomen
Lesser Omentum
Lesser
Sac
Greater Sac
Liver
Lt. Kidney
D
Spleen
An. Ad. Wall
TC
Mesocolon
Pos. A. Wall
Anter. view
Greater and Lesser Omentum
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Diaphragm
Ant. Abd. Wall
Greater Sac
Liver
Stomach
Peritoneum
Spleen
Lt. Kidney
Umblicus
Falciform
Ligament
Lienorenal lig.
Post. Abd. Wall
Gastrosplenic Lig.
Greater Sac
Lesser Omentum
Dorsal and Ventral Mesenteries of Foregut
Prof.Abdulameer Al-Nuaimi
Falciform Lig.
Liver
Diaphragm
Umblicus
Lesser Omentum
Less. Sac
L.
Spleen
S
Lt. Kidney
Post. Abd. Wall
Greater Sac
Dorsal Mesentery
(Greater Omentum)
Rotation of Stomach
Prof. Abdulameer Al-Nuaimi
Falciform Lig.
Diaphragm
L.
Ant. Abd. Wall
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L.
Less. Sac
Spleen
Lesser Omentum
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
Parietal peritoneum
GS
Ant. view
L
L. Om S
Cross Section in the abdomen
G. Om
Greater and Lesser Sac
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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.
passion flower
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