
3RD WEEK

AXIAL
› Prechordal
mesenchyme
› Cardiogenic
› Septum transversum

PARAXIAL

INTERMEDIATE

LATERAL PLATE

4th wk.

Inverted U shaped cavity in:
› Cardiogenic area
› Lateral plate mesoderm

Bend –cranial to prochordal
plate – primitive pericardial
cavity

Limbs of U – lateral half of disc

Limbs :
› Pleural cavity
› Peritoneal cavity

Initial part of limbs – flank
foregut

Caudal part of limbs –
communicate with extraembryonic coelom

The two limbs are called
pericarioperitoneal canals

4th week

Pericardial cavity – ventral below foregut

Pericardial cavity bend at right
angle – communicate with
pericardioperitoneal canal

Pericardioperitoneal canal
› Dorsal to septum transversum
› Lateral to foregut

Pleuroperitoneal
canals –

Ventral aspect

Merge – single
peritoneal cavity

The coelome lined by
mesothelium

Derived from:

Somatic mesoderm (parietal
layer)

Splanchnic mesoderm
(visceral layer)

Into:
› Pericardial cavity
› Pleural cavity
› Peritoneal cavity

Division achieved by:
› Septum transversum
› Paired pleuropericardial folds – superior to lungs
› Paired pleuroperitoneal folds – inferior to lungs

4th week

Bronchial budspericardioperitoneal
canal – future pericardial
cavity

Pleural cavity expand –
grow ventrally

Common cardinal vein &
Phrenic nerve raise
ridge in lateral thoracic
wall

Pleural cavity grow in
angle between body wall
& ridge

Result:
› Mesenchyme of body
wall split
 Outer layer – thoracic
wall
 Inner layer –
pleuropericardial
membrane

7th week

membrane – grow medially
Pleuropericardial – fuse with
› Each other
› Mesenchyme ventral to
oesophagus

Separate pericardial from pleural
cavity

Right pleuropericardial
opening close earlier
› Right common cardinal
vein larger – raise bigger
fold

Fused pleuropericardial
membrane form FIBROUS
PERICARDIUM

Separate pleural from peritoneal
cavity

Lung & pleura invade body wall –
strip mesoderm

Ridge formed – caudal end of
pericardioperitoneal canal

Ridge- fold –cresentic free edgeproject into pericardioperitoneal
canal

Liver develop

Fold become membranous

6th week

Pleuroperitoneal
membrane grow ventro –
medially - fuse with:
› Dorsal mesentry of
oesophagus
› Septum transversum

Double layer of peritoneum
enclosing a mass of mesoderm

Connects the organ to the body
wall

Carries vessels, nerves &
lymphatics for the organ

Is the site where the visceral
peritoneum continues as parietal
peritoneum

Transverse folding –medial walls
of intra-embryonic coelon come
together – mesentry

Between layers – mesenchyme –
B.V. & nerves

Transiently divide I.E.Coelom into
two halves

Contain gut in them

Transitory structure

Limited to stomach & duodenum

Gut suspended by it – mid plane

Not in pharynx & upper
oesophagus

Given names– mesoesophagus….

Further development
› Some parts specialized
› Some – secondary attachment
› Some disappear

Heart tube invaginate
pericardium from dorsal aspect

Parietal & fibrous pericardium
derived from somatopleuric
mesoderm lining ventral side of
pericardial cavity

Visceral pericardium derived from
splanchnopleuric mesoderm lining
dorsal side of pericardium

Heart tube suspended in
pericardial cavity by dorsal
mesocardium - disappears

Communication – right & left side
of pericardium – transverse
pericardial sinus

Four sources
1.
Septum transversum
2.
Pleuroperitoneal
membranes
3.
Dorsal mesentery of
esophagus
4.
Muscular ingrowth from
lateral body walls

3rd week
› Unsplit mesoderm
› Cranial to cardiogenic mesoderm

4th week
› Folding
 Septum transversum
 Caudal to pericardium
 Ventral to pericardioperitoneal canal

Cranial part - diaphragm

Caudal part
› Liver
› Ventral Mesentry

Expand & fuse with
pleuroperitoneal
membrane

Form central tendon

5th week

Develop at caudal end of
pericardioperitoneal canal

Crescent fold - medially

Fuse with:
› Septum transversum
› Dorsal mesentry oesophagus

Myoblast from S.T. –
pleuroperitoneal membrane

Bulk of muscle form here

Initially – median part

Finally mesoesophagus
condenses – L1 – L3

Two muscle bands
› Myoblast grow in dorsal
mesentry of esophagus

Develop into Right &
left crura

9th – 12th week

Lungs & pleural cavity
enlarge

Burrow into body wall

Mesenchyme split
› External – abdominal wall
› Internal – peripheral part of
diaphragm

Pleura extend further
› Costodiapharagmatic
recess
› Dome shaped
configuration

6th week :

Three basic components:
1.
Pleuroperitoneal
membranes

2.
Mesoesphagus
3.
Septum transversum
Fuse - form a complete
partition between thoracic
and abdominal cavities
Septum transversum:
Central tendon
Pleuroperitoneal membranes:
Form large portion of fetal
diaphragm
represent a smaller portion in
infants
Dorsal mesentery of esophagus:
Crura
Body wall:
Peripheral muscular part
•
4th week
•
Septum transversum opposite 3rd – 5th
cervical somites
•
5th week
•
Myoblasts from somites - developing
diaphragm bringing their nerve fibers
with them
•
Rapid growth of the body descent of diaphragm
•
6th week the diaphragm level of the thoracic
somites
•
End of 8th week diaphragm - level of first
lumbar vertebra

4 parts of the diaphragm fuse

Mesenchymal cells from the septum
transversum - other three parts,

Change into myoblasts -muscles of
the diaphragm.

Phrenic nerve supplies all the
muscles of diaphragm

Phrenic nerve - sensory to
diaphram except peripheral region
derived from the body wall and brings
its nerve supply (lower intercostal
nerves) with it

Only common anomaly

1 in 2200 newborns

Associated with CDH

Inhibition of development & inflation of lung- breathing difficulties

Lung hypoplasia – infant may die

Severe lung hypoplasia – alveoli rupture – pneumothorax

Polyhydramnios maybe present

Cause:
› Defective formation / fusion of
pleuroperitoneal membrane with...

Large opening in posterolateral
part of diaphragm

Peritoneal & pleural cavities
communicate

85-90% on left side – foramen of
Bochdalek

Foramen closes at 6th wk.

If open –viscera in thorax – lying

Lungs & heart pushed anteriorly

Most defects on left side – heart
pushed to right

Severity of lung development –
extent of viscera in thorax – no
room for development

Treatment
› Repair of defect – post natally
› Lung achieve normal size

Half of diaphragm – defective
musculature – diaphragmatic pouch

Superior displacement of viscera

Cause:
› Failure of muscular tissue from body
wall to extend into pleuroperitoneal
membrane

Clinical manifestation – CDH

Treatment:
› Surgical repair
 Latissimus dorsi flap
 Prosthetic patch

Herina – between
xiphoid process &
umbilicus

Cause:
› Failure of lateral body
folds to fuse completely
when forming anterior
abdominal wall during
folding

Herniation of part of fetal
stomach through excessively
large esophageal hiatus

May be a predisposing factor
in adult acquired hiatal hernia

Herniation through the sternocostal hiatus (foramen of Morgagni) – opening
for superior epigastric B.V.

Hiatus – between sternal & costal parts of diaphragm

Herniation of:
› Intestines into pericardial sac
› Heart into peritoneal cavity

Large defects associated with body wall defects

Most often on right side

Associated with lung hypoplasia & respiratory comlications

Diagnosis:
› MRI

Treatment:
› Surgical excision
Double layer of peritoneum
enclosing a mass of mesoderm
 Connects the organ to the body
wall
 Carries vessels, nerves &
lymphatics for the organ
 Is the site where the visceral
peritoneum continues as parietal
peritoneum
