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

5.  4 th 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

6.  Initial part of limbs – flank foregut  Caudal part of limbs – communicate with extra- embryonic coelom  The two limbs are called pericarioperitoneal canals

8.  4 th 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

9.  Pleuroperitoneal canals –  Ventral aspect  Merge – single peritoneal cavity

10.  The coelome lined by mesothelium  Derived from:  Somatic mesoderm (parietal layer)  Splanchnic mesoderm (visceral layer)

11.  Into: › Pericardial cavity › Pleural cavity › Peritoneal cavity  Division achieved by: › Septum transversum › Paired pleuropericardial folds – superior to lungs › Paired pleuroperitoneal folds – inferior to lungs

12.  4 th week  Bronchial buds- pericardioperitoneal canal – future pericardial cavity  Pleural cavity expand – grow ventrally  Common cardinal vein & Phrenic nerve raise ridge in lateral thoracic wall

13.  Pleural cavity grow in angle between body wall & ridge  Result: › Mesenchyme of body wall split  Outer layer – thoracic wall  Inner layer – pleuropericardial membrane

14.  7 th week  membrane – grow medially Pleuropericardial – fuse with › Each other › Mesenchyme ventral to oesophagus  Separate pericardial from pleural cavity

15.  Right pleuropericardial opening close earlier › Right common cardinal vein larger – raise bigger fold  Fused pleuropericardial membrane form FIBROUS PERICARDIUM

16.  Separate pleural from peritoneal cavity  Lung & pleura invade body wall – strip mesoderm  Ridge formed – caudal end of pericardioperitoneal canal  Ridge- fold –cresentic free edge- project into pericardioperitoneal canal

17.  Liver develop  Fold become membranous  6 th week  Pleuroperitoneal membrane grow ventro – medially - fuse with: › Dorsal mesentry of oesophagus › Septum transversum

18.  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

19.  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

20.  Transitory structure  Limited to stomach & duodenum

21.  Gut suspended by it – mid plane  Not in pharynx & upper oesophagus  Given names– mesoesophagus….  Further development › Some parts specialized › Some – secondary attachment › Some disappear

22.  Heart tube invaginate pericardium from dorsal aspect  Parietal & fibrous pericardium derived from somatopleuric mesoderm lining ventral side of pericardial cavity

23.  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

25.  Four sources 1. Septum transversum 2. Pleuroperitoneal membranes 3. Dorsal mesentery of esophagus 4. Muscular ingrowth from lateral body walls

26.  3 rd week › Unsplit mesoderm › Cranial to cardiogenic mesoderm  4 th week › Folding  Septum transversum  Caudal to pericardium  Ventral to pericardio- peritoneal canal

27.  Cranial part - diaphragm  Caudal part › Liver › Ventral Mesentry  Expand & fuse with pleuroperitoneal membrane  Form central tendon

28.  5 th 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

29.  Initially – median part  Finally mesoesophagus condenses – L1 – L3  Two muscle bands › Myoblast grow in dorsal mesentry of esophagus  Develop into Right & left crura

30.  9 th – 12 th week  Lungs & pleural cavity enlarge  Burrow into body wall  Mesenchyme split › External – abdominal wall › Internal – peripheral part of diaphragm 

31.  Pleura extend further › Costodiapharagmatic recess › Dome shaped configuration

32.  6 th week  6 th week :  Three basic components: 1. Pleuroperitoneal membranes 2. Mesoesphagus 3. Septum transversum thoracic abdominal cavities  Fuse - form a complete partition between thoracic and abdominal cavities

33. 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

34. 4 th week 4 th week cervical somites Septum transversum opposite 3 rd – 5 th cervical somites 5 th week 5 th week Myoblasts from somites - developing diaphragm bringing their nerve fibers with them

35. Rapid growth of the body - descent of diaphragm 6 th week thoracic somites 6 th week the diaphragm - level of the thoracic somites 8 th week first lumbar vertebra End of 8 th week - diaphragm - level of first lumbar vertebra

36.  4 parts of the diaphragm fuse  Mesenchymal cells from the septum transversum - other three parts,  Change into myoblasts -muscles of the diaphragm.  Phrenic nerve  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

37.  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

38.  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

39.  Foramen closes at 6 th 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

40.  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

41.  Herina – between xiphoid process & umbilicus  Cause: › Failure of lateral body folds to fuse completely when forming anterior abdominal wall during folding

42.  Herniation of part of fetal stomach through excessively large esophageal hiatus  May be a predisposing factor in adult acquired hiatal hernia

43.  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

44.  Most often on right side  Associated with lung hypoplasia & respiratory comlications  Diagnosis: › MRI  Treatment: › Surgical excision

52.  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