DIAPHRAGM & PLEURAL CAVITIES

INTRAEMBRYONIC CEOLOM EMBRYONIC BODY CAVITY

INTRAEMBRYONIC MESODERM 3 RD WEEK AXIAL – PRECHORDAL MESENCHYME – CARDIOGENIC – SEPTUM TRANSVERSUM PARAXIAL INTERMEDIATE LATERAL PLATE

CEOLOMIC SPACES 18 th Day Isolated Small Spaces In lat. Plate mesoderm Due To Apoptosis Primordium Of Intra Embryonic Ceolom Cells at periphery of vesicles,become epithelial.

INTRA EMBRYONIC CEOLOM Horse Shoe Shaped Cavity Caudally to the level of 1 st somite No communication between intra and extra embryonic ceolom

INTRA EMBRYONIC CEOLOM Intraembryonic coelom extends to caudal wall of the yolk sac. Distal part of each limb communicates with the extraembryonic coelom from 4th somite. Connection closes during the 10th week

DERIVATIVES INTRA EMBRYONIC CEOLOM Midline ventral portion, forms pericardial cavity. Pericardioperitoneal canals pleural cavities and the uppermost part of the peritoneal cavity Lower part peritoneal cavity The division is achieved by development of three sets of partitions – Septum transversum (unpaired) – Pleuropericardial membranes (paired) – Pleuroperitoneal membranes (paired

FOLDING 4 TH WEEK CRANIO CAUDALHORIZONTAL

EFFECT OF FOLDING Pericardial cavity & heart relocated ventrocaudally, ant. to foregut Pericardioperitoneal canals, lateral to proximal part of foregut & dorsal to septum transversum The caudal parts turn 90° Single large cavity communicate with extraembryonic coelom ventrally After embryonic folding, the caudal part of foregut, midgut, & hindgut are suspended in the peritoneal cavity by the dorsal mesentery

PLEURAL CAVITIES LUNG BUDS – 4 TH WEEK – VENTRAL WALL OF FOREGUT PERICARDIO PERITONEAL CANALS – PRIMARY PLEURAL CEOLOM – PLEUROPERICARDIAL PLEUROPERITONEAL CANALS

DEFINITIVE PLEURAL CAVITIES PULMONARY RIDGE – PLEURO PERICARDIAL MEMBRANE PHRENIC NERVE COMMON CARDINAL VEIN – PLEURO PERITONEAL MEMBRANES INVASION & SPLITTING OF SOMATOPLEURIC MESENCHYME – CRANIALLY PLEUROPERICARDIAL MEBRANE – VENTROMEDIALLY FIBROUS PERICARDIUM PARIETAL layer of serous pericardium MEDIASTINAL pleura – DORSOCAUDALLY Dorsolumbar part of diaphragm

SEPTUM TRANSVERSUM

3 rd Week – Axial Mesenchyme – Cranial To Cardiogenic Mesoderm 4 th Week Folding – B/W Pericardial & Peritoneal Cavities – Partial Separation Pars Diaphragmatica – Central Tendon – Sternal & Costal Parts – Myoblast Originating In The Septum Trans. Emigrate Into Pleuroperitoneal Membrane Pars Mesenterica – Median sagittal plane Pars Intermedia

THORACO ABDOMINAL DIAPHRAGM MUSCULOTENDINOUS DOME SHAPED PARTITION

DIAPHRAGM COMPOSITE STRUCTURE – SEPTUM TRANSVERSUM Pars diaphragmatica – Sternal & costal parts Pars mesenterica – Gastrohepatic ligament – Anterior to esophageal hiatus – MESENTARY OF ESOPHAGUS – PLEUROPERITONEAL FOLDS & MEMBRANES – MESENCHYME OF BODY WALL LONG ARM OF Ch 15

MESENTERY OF ESOPHAGUS Double Layer Of Peritoneum Connecting To Body Wall Transmits Vessels & Nerves Condenstaion Of Mesenchyme From L1 --- L3 Muscular Bands – Rt. & Lt Crura Of Diaphragm

PLEURO PERITONEAL MEMBRANES 5 th Week Pleuroperitoneal Folds In Pleuro Peritoneal Canals Pleuroperitoneal Membrane 7 th Week Fuses With Mesentery Of Esophagus And Septum Transversum Myoblast of Septum Trans. Migrate into PPM Forming bulk of diaphragmatic musculature Fetal Vs Newborn Diaphragm Right Closes Earlier

MESODERMOF BODY WALL EXPANDING LUNGS – 9th to 12th weeks, the lungs and pleural cavities "burrow" into lateral body walls MESENCHYME OF BODY WALL SPLIT INTO – INNER Contributes to peripheral parts of diaphragm, external to parts derived from pleuroperitoneal membranes – OUTER becomes part of the definitive abdominal wall Further extension into the lateral body walls forms costodiaphragmatic recesses establishing characteristic dome-shaped configuration of the diaphragm.

MUSCLES OF DIAPHRAGM MYOBLAST TWO SOURCES MYOBLAST ORIGINATING IN BODY WALL MYOBLAST ORIGINATING FROM SEPTUM TRANSVERSUM

POSITIONAL CHANGES GROWTH OF DORSAL PART of body ELONGATION OF NECK DESECNT OF HEART ENLARGEMENT OF PLEURAL AND PERICARDIAL CAVITIES 4 TH WEEK CERVICAL SOMITES 6 TH WEEK THORACIC 8 TH WEEK LUMBAR

NERVE SUPPLY PHRENIC LOWER SIX INTERCOSTAL NERVES

DIAPHRAGMATIC HERNIA Congenital Diaphragmatic Hernia – Most Common – Herniation Of Abdominal Visceras Lung Hypoplasia – Polyhydramnios – POSTEROLATERAL – Failure Of Fusion Of Pleuro Peritoneal Membranes – Uni Or Bilateral – UNILATERAL LEFT (Rt. Opening Is Smaller And Closes Earlier

Defects In Septum Transversum Parastenal Hernia (Morgagni) – Sternocostal hiatus for sup. Epigastric vessels – Failure Of Muscular Fiber – Heart into pericardial cavity – Herniation of intestine in pericardial sac Hiatal Hernia – Acquired – Congenital Large esophageal hiatus Short esophagus

Eventration of diaphragm – Failure of muscular tissue from body wall to extend into pleuroperitoneal mebrane Gastroschisis – Defective fusion of lateral body wall – Intestine herniate into abdominal cavity