1. BODY CAVITIES Slidelearn Team

2. FORMATION OF BODY CAVITY END OF 3 RD WEEK At the end of third week there is differentiation of Intraembryonic mesoderm changes into  Paraxial mesoderm  Intermediate mesoderm  Lateral plate mesoderm

3. FORMATION OF BODY CAVITY Lateral plate mesoderm Intracellular clefts appears in the lateral plate mesoderm at 3 rd week and divides it into  Parietal/somatic layer  Visceral/splanchnic layer  Primitive body cavity Somatic mesoderm later forms the parietal layer of serous membrane lining outside the pericardial, peritoneal and pleural cavities Splanchnic mesoderm form the viseral layer that cover the lungs, abdominal organs and the heart

4. FORMATION OF (intraembryonic coelom) BODY CAVITY Intraembryonic mesoderm give rise to three cavities Pericardial cavity Large Peritoneal cavity Two pericardioperitoneal cavities Lateral body folds: Parietal layer of LPM Overlying ectoderm Cells of adjacent somites Endoderm: folds & closes Gut tube

5. End of 4 th week Closure of gut tube  Midgut connection to yolk sac  Vitelline duct  Incorporate in umbilical cord  Degenerate in 2 nd - 3 rd months Closure of ventral body wall  Head and tail folds  Embryo curve in fetal position  Gap in area of connecting stalk

7. SEROUS MEMBRANES Parietal layer  Serous layer of serous membranes  Lining peritoneal, pleural & pericardial cavities Visceral layer  Visceral layer of serous membrane  Covering abdominal organs, heart and lungs

8. SEROUS MEMBRANES Parietal and visceral layers  Become mesothelial  continuous at junction of gut & posterior abdominal wall  Form Dorsal mesentery  Extent; foregut to hind gut Ventral mesentary  Caudal foregut to upper duodenum  Thinning of septum transversum

9. CLINICAL APPLICATIONS Ventral body defects  Thorax, abdomen, pelvis  Failure of closure of ventral body wall  Mainly involve lateral body folds Ectopic cordis Gastroschisis Bladder & cloacal exstrophy

10. Ectopic cordis Failure in thoracic region Heart outside body cavity Cantrell Pentalogy Secondary to body wall closure defect Defect from sternum to upper abdomen  Ectopia cordis  Defect in diaphragm  Absence of diaphragm  Omphalocele  Gastroschisis

11. Gastroscisis Defect in abdominal region Intestinal loop herniate in amniotic cavity Incidence increasing Common in mothers; lean & below 20yrs Detected by  Ultrasound  Alpha fetoprotein  Affected loops; ulcerate, volvulus, compromised blood supply

12. Bladder & cloacal exstrophy  Pelvic region defect  Minor defect: only bladder involved  Major defect :bladder and rectum exposed

13. Omphalocele Failure of gut tube to return to abdominal cavity Loops of intestine and liver outside Covered by amnion 2-5/10,000 15% cases have chromosomal abnormality Elevated alpha fetoprotein

14. THORACIC CAVITY Septum Transversum  Thick plate of mesoderm  B/w thoracic cavity and yolk sac stalk  Incomplete  “Pericardioperitoneal canals” on each side of gut

15. Lung bud  grow within pericardioperitoneal canals  Expand dorsally, ventrally and laterally  Canals become small  Lungs grow in mesenchyme of body wall

17. THORACIC CAVITY Pleuropericardial folds  Small ridges  Projecting in primitive thoracic cavity  Become membranes  Contain Common cardinal veins Phrenic nerves  Fuse with each other & lung root  Dividing thoracic cavity  Adult “fibrous pericardium”

18. DIAPHRAGM Pleural cavity communicate with peritoneal by pericardioperitoneal canals Crescent shaped pleuroperitoneal folds  Extends medially and ventrally  7 th week fuse with Mesentary of esophagus Septum transversum  Addition of peripheral rim  Myoblasts from somites C3-5 penetrate membrane

19. DIAPHRAGM Derived from  Septum transversum – central tendon  Pleuroperitoneal membranes— membranous part  Somites C3-5 -- Muscular component  Mesentary of esophagus -- crura

20. DESCENT OF DIAPHRAGM Initially  septum transversum---opposite cervical somites  Nerve supply from C-3,4,5  Forming phrenic nerves (sensory and motor)  Pass through pleuropericardial folds  Sensory fibers from thoracic intercostal nerves as most peripheral part derived from thoracic wall mesenchyme 6 th week – level of thoracic somites 3 rd month - Lower thoracic & first lumbar vertebra

21. CLINICAL APPLICATIONS Congenital diaphragmatic hernia  1/2000  Failure of pleuroperitoneal membranes  Pleural and peritoneal cavities communicate  Abdominal viscera enter pleural cavity  85-90 % left side  heart pushed anteriorly  Lungs hypoplastic  75% death

22. Clinical Anomalies Parasternal hernia  Muscular fibers failure  Discover at several years of age  Small peritoneal sac with intestinal loop Esophageal hernia  Shortness of esophagus  Upper part of stomach in thorax  Stomach constricted at diaphragm