3 RD WEEK AXIAL › Prechordal mesenchyme › Cardiogenic › Septum transversum PARAXIAL INTERMEDIATE LATERAL PLATE

BODY CAVITIES

DR. ZAHRA HAIDER BOKHARI

EXTRA-EMBRYONIC COELOM

MESODERM

3RD WEEK

AXIAL

› Prechordal

mesenchyme

› Cardiogenic

› Septum transversum

PARAXIAL

INTERMEDIATE

LATERAL PLATE

INTRAEMBRYONIC COELOM

INTRA-EMBRYONIC COELOM

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

INTRA-EMBRYONIC COELOM

Initial part of limbs – flank

foregut

Caudal part of limbs –

communicate with extra-

embryonic coelom

The two limbs are called

pericarioperitoneal canals

FOLDING

HEAD FOLDING

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

TRANSVERSE FOLDING

Pleuroperitoneal

canals –

Ventral aspect

Merge – single

peritoneal cavity

The coelome lined by

mesothelium

Derived from:

Somatic mesoderm (parietal

layer)

Splanchnic mesoderm

(visceral layer)

DIVISION OF INTRA-EMBRYONIC COELOM

Into:

› Pericardial cavity

› Pleural cavity

› Peritoneal cavity

Division achieved by:


› Paired pleuropericardial folds – superior to lungs

› Paired pleuroperitoneal folds – inferior to lungs

PLEUROPERICARDIAL MEMBRANE

4th week

Bronchial buds-

pericardioperitoneal

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

PLEUROPERITONEAL MEMBRANE

Separate pleural from peritoneal

cavity

Lung & pleura invade body wall –

strip mesoderm

Ridge formed – caudal end of


Ridge- fold –cresentic free edge-

project into pericardioperitoneal

canal


Liver develop

Fold become membranous

6th week

Pleuroperitoneal

membrane grow ventro –

medially - fuse with:

› Dorsal mesentry of

oesophagus


MESENTERY

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

MESENTRY

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

VENTRAL MESENTRY

Transitory structure

Limited to stomach & duodenum

DORSAL MESENTRY

Gut suspended by it – mid plane

Not in pharynx & upper

oesophagus

Given names– mesoesophagus….

Further development

› Some parts specialized

› Some – secondary attachment

› Some disappear

DEVELOPMENT OF PERICARDIUM

Heart tube invaginate

pericardium from dorsal aspect

Parietal & fibrous pericardium

derived from somatopleuric

mesoderm lining ventral side of

pericardial cavity

DORSAL MESOCARDIUM

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

DORSAL MESOCARDIUM

DEVELOPMENT OF DIAPHRAGM

Four sources

1. Septum transversum

2. Pleuroperitoneal

membranes

3. Dorsal mesentery of

esophagus

4. Muscular ingrowth from

lateral body walls

SEPTUM TRANSVERSUM

3rd week

› Unsplit mesoderm

› Cranial to cardiogenic mesoderm

4th week

› Folding

Septum transversum

Caudal to pericardium

Ventral to pericardio-

peritoneal canal

SEPTUM TRANSVERSUM

Cranial part - diaphragm

Caudal part

› Liver

› Ventral Mesentry

Expand & fuse with

pleuroperitoneal

membrane

Form central tendon


5th week

Develop at caudal end of


Crescent fold - medially

Fuse with:


› Dorsal mesentry oesophagus

Myoblast from S.T. –

pleuroperitoneal membrane

Bulk of muscle form here

DORSAL MESENTERY OF ESOPHAGUS

Initially – median part

Finally mesoesophagus

condenses – L1 – L3

Two muscle bands

› Myoblast grow in dorsal

mesentry of esophagus

Develop into Right &

left crura

CONTRIBUTION FROM BODY WALL

9th – 12th week

Lungs & pleural cavity

enlarge

Burrow into body wall

Mesenchyme split

› External – abdominal wall

› Internal – peripheral part of

diaphragm

CONTRIBUTION FROM BODY WALL

Pleura extend further

› Costodiapharagmatic

recess

› Dome shaped

configuration

DIAPHRAGM

6th week :

Three basic components:

1. Pleuroperitoneal

membranes

2. Mesoesphagus

3. Septum transversum

Fuse - form a complete

partition between thoracic

and abdominal cavities

Body wall:

Peripheral muscular part

Pleuroperitoneal membranes:

Form large portion of fetal

diaphragm

represent a smaller portion in

infants

Septum transversum:

Central tendon

Dorsal mesentery of esophagus:

Crura

POSITIONAL CHANGES & INNERVATION OF THE DIAPHRAGM

• 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

POSTEROLATERAL DEFECTS OF DIAPHRAGM

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

POSTEROLATERAL DEFECT OF DIAPHRAGM

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

POSTEROLATERAL DEFECTS OF DIAPHRAGM

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

EVENTRATION OF DIAPHRAGM

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

GASTROSCISIS & CONGENITAL EPIGASTRIC HERNIA

Herina – between

xiphoid process &

umbilicus

Cause:

› Failure of lateral body

folds to fuse completely

when forming anterior

abdominal wall during

folding

CONGENITAL HIATAL HERNIA

Herniation of part of fetal

stomach through excessively

large esophageal hiatus

May be a predisposing factor

in adult acquired hiatal hernia

RETROSTERNAL (PARASTERNAL) 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

ACCESSORY DIAPHRAGM

Most often on right side

Associated with lung hypoplasia & respiratory comlications

Diagnosis:

› MRI

Treatment:

› Surgical excision

A

B

C

D

E

F

G

mesentry

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

Documents

3 RD WEEK AXIAL › Prechordal mesenchyme › Cardiogenic › Septum transversum PARAXIAL INTERMEDIATE LATERAL PLATE