1. No category

Body Cavities,
Mesenteries &
Diaphragm
Peritoneal cavity
y
Pleural
cavity
Pericardial cavity
3 week
paraxial
mesoderm
extraembryonic coelom
chorionic
h i i cavity
it
lateral
mesoderm
ectoderm
*
18 day
embryo
lateral
mesoderm
*
intraembryonic coelom:
cardiogenic
g
area
& lateral mesoderm
*
*
20 day
iintraembryonic
t
b
i
coelom
*Intraembryonic coelom
horseshoe-shaped cavity
-Curve
Curve
 future pericardial cavity
-Limbs
Limbs
 future pleural & peritoneal cavities
*
intraembryonic
coelom
*
 Distal part of each limb -- at
the lateral edges of the
embryonic
b
i disc
di -extraembryonic coelom
*
early in the 4th week
Folding of the embryo
Tail fold
Head fold
pericardial coelom
Lateral fold
Lateral fold
*
22 d
Intraembyonic coelom &
E b
Embryonic
i F
Foldings
ldi
~26
26 days
*
*
dorsal mesentery
ventral mesentery
except where it is attached to caudal foregut
(future stomach & proximal duodenum)
~28 days

19 D
20 D
End of 4 week
Embryonic body cavity
Somatic mesoderm
parietal wall
future parietal layer of peritoneum
Splanchnic mesoderm
visceral wall
y of p
peritoneum
future visceral layer
~24 days
Pericardioperitoneal Canals
~24 days
--
Each lies lateral to foregut (future
esophagus) and dorsal to septum
transversum (primordial central
tendon of diaphragm).
• In lateral wall of each
pericardioperitoneal canal:
- cranial ridge: pleuropericardial fold
pleuropericardial membrane
(contain common cardinal veins)
- caudal ridge: pleuroperitoneal fold
pleuroperitoneal membrane
5 wks
6 wks
s
• During the 7th week, pleuropericardial membranes
fuse with the mesenchyme ventral to esophagus
-- Forming
F
i
primordial mediastinum.
-- Separating pericardial cavity
from pleural cavities.
--extend into body wall, splitting the mesenchyme into:
outer layer  thoracic wall inner layer  fibrous
pericardium
7 wks
8 wks
Beginning of
5th W
Diaphragm
Head Fold



septum
transversum
Pleuroperitoneal Membranes
Separates the pleural cavities
from peritoneal cavity.
cavity
•
End of 5th wk
Ventral
End of 6th wk
12th wk
Dorsal
mesentery off
esophagus
Muscular
ingrowth from
l
lateral
l body
b d
walls
Body wall tissue is added
peripherally to the
diaphragm as the lungs and
pleural cavities enlarge
Positional Changes & Innervation
off th
the Diaphragm
Di h
• phrenic nerves
nerves- ventral rami of the 3rd, 4th, &
5th cervical spinal nerves.
phrenic nerves -30
30 cm long in adults.
adults
the beginning
g
g of the 8th week
4th week
6th week
CONGENITAL DIAPHRAGMATIC HERNIA
(CDH, 疝)
Prenatal diagnosis:
Ultrasound & magnetic
g
resonance imaging
g g
of abdominal organs in thorax.
Posterolateral defect
Defective muscular development
Herniation of liver
Herniation of stomach and bowel
Summary (I)
1. the end of the 3rd
1
week:
Intraembryonic coelom
begins to develop.
2. By the 4th week:
2
 a horse-shoe-shaped
y in cardiogenic
g
&
cavity
lateral mesoderm.
The right & left part of the
i t
intraembryonic
b
i coelom
l

peritoneal cavity.
3 the 7th week: pericardial
3.
cavity paired
pericardioperitoneal canals
 peritoneal
it
l cavity
it
Summary (II)
3. During the 5th & 6th weeks,
folds (later membranes) form near
the cranial & caudal ends of these
canals.
4. By the end of the 6th week,
week fusion of
the caudal pleuroperitoneal membranes
d i
during
formation
f
ti
off th
the di
diaphragm
h

p
the p
pleural cavities from
separates
the peritoneal cavity.
Summary (III)
5. By
5
B th
the 7th week,
k
Fusion of the cranial
pleuropericardial membranes
with mesoderm ventral to the
esophagus
separates the
pericardial cavity
p
y from the
pleural cavities.
6 The
6.
Th diaphragm
di h
d
develops
l
from
f
4 structures.