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Formation of body cavities , development of the serous membranes

Formation of body cavities , development of the serous membranes. Mark Kozsurek, M.D., Ph.D. ED I., 21/03/2019. Appearance of the common pericardio-pleuro-peritoneal cavity . Isolation of the pleural and peritoneal cavities: the formation of the diaphragm .

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Formation of body cavities , development of the serous membranes

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  1. Formation of body cavities, development of theserousmembranes Mark Kozsurek, M.D., Ph.D. ED I., 21/03/2019

  2. Appearance of thecommonpericardio-pleuro-peritonealcavity. • Isolation of the pleural and peritoneal cavities: the formation of the diaphragm. • Isolation of the pericardiac and pleural cavities. • Furtherdevelopment of thepericardium, pleura and peritoneum.

  3. A) Appearance of thecommonpericardio-pleuro-peritonealcavity Back tothe 2nd week: bilaminarembryonicdiskcomposed of epiblasts and hypoblasts During the 3rd week: proliferation of epiblastsresults in gastrulation

  4. Gastrulation:junctionsamongepiblastsbecomelooser and duetothecollisionattheprimitivenode and primitivestreakepiblasts sink belowtheiroriginallayer. Some of themreplacethehypoblasts and differentiateintotheultimateendoderm, whileothers, themesoblasts, form a third, middlelayer, theintraembryonicmesoderm. Epiblastremaining in theiroriginallayerwillformtheectoderm.

  5. Initiallytheintraembryonicmesoderm is just a homogenousmass of tissueonthetwosides of thenotochord. Later a mediolateraldifferentiationgivesarisetothesomites, intermediatemesoderm and thelateralplate. Withinthelateralplatecavitiesform and mergeresulting in theisolation of thesomatic (parietal) and splanchnic (visceral) layer of lateralplatemesoderm.

  6. Somatic and splanchniclayers of thelateralplatemesodermenclosethehorse-shoeshaped (orsimply „U”-shaped) intraembryoniccoelom, whichposteriorlyonthelateralsides of theembyocommunicateswiththeextraembryoniccoelom. Withthefurthergrowth of theembryotheintraembryoniccoelomwilldilateanteriorly (thecurve of U - futurepericardium), theproximallimb of U remainsnarrow (pericardioperitonealcanal - thefuturepleuralcavity), whilethevolume of thedistallimb of U alsoincreases (futureperitonealcavity). Oropharyngealmembrane

  7. Isolatedintraembryoniccoelom futurepericardiaccavity Oropharyngealmembrane pericardio-peritoneal canals (future pleural cavities) future peritoneal cavity connectionsbetweentheintra- and extraembryoniccavities

  8. Oropharyngealmembrane A A B B In section B it is wellseenthattheextraembryonicmesoderm is continuouswiththeintraembryonicone, extra- and intraembryoniccoelomscommunicate.

  9. During the 4th week: folding of theembryo has thehighestimpactonthefurterdevelopment of theintraembryoniccavity: heartprimordiummovesontotheventralside of theembryo, septumtransversumturnsintothetransverseplanecaudaltotheheart.

  10. As a result of folding of theembryotheleft and rightlimbs of theintraembryoniccoelomgetclosertothemidline and toeachother and atthesametime, followingthemovements of theheartprimordium, thedilatedcurve of the U-shapedtunnelturnsontotheventralside of theembryo. Butatthisstagethefurtherpericardiac, pleural and peritonealcavitiesarenotisolatedfromoneother (commonpericardiaco-pleuro-peritonealspace).

  11. B) Isolation of thepleural and peritonealcavities: theformation of thediaphragm Notethecentraltendon and thesternal, costal, lumbarparts of thediaphragm. How is itmade?

  12. The narrowpericardiacoperitonealcanalsarefoundbehindtheseptumtransversum. Therearefourstructurescontributingtothediaphragm: septumtransversum pleuroperitonealmembranes– astheygrowthepericardiaco-peritonealcanalnarrows dorsalmesentery of theesophagus – surroundsthe aorta, theesophagus and the IVC muscularingrowthfrom body wall

  13. septumtransversum esophagealmesentery pleuro- peritoneal folds muscularingrowth Myoblastfrom C3-C5 myotomesmigrateintotheseptumtransversum and taketheirnervewiththemselves (phrenicnerve). Butlowerintercostalnervesalsocontributetotheinnervation of theperiphery of thediaphragmformedbythemuscularingrowth of the body wall.

  14. Congenitaldiaphragmatichernia Incompletefusion of thefour parts. Stomach and/orintestineascendintothethoraciccage and compressthelungs.

  15. C) Isolation of thepericardiac and pleuralcavities Formation of thediaphragmhaveisolatedperitonealcavityfromthepericardiacopleuralspace. Diaphragm C3-C5 commoncardinalvein, phrenicnerve Asthehearttubeloopsitscaudal end withthecommoncardinalveinsmovesupward and thephrenicnervesmigratetowardthemidlineformingthepleuropericardial fold.

  16. Duetothechangingposition of thephrenicnerve and thecommoncardinalvein, thepleuro-pericardialmembraneappears, whichlatercompletlyisolatespleural and pericardiaccavities.

  17. Summary 1.The most anterior part, theloop of theintraembryoniccoelomgivesthepericardialcavityenclosingtheheart. 2. Rostrallimbsof theintraembryoniccoelomdonotunite in themidline and as a result of this, two non-communicating, left and rightpleuralcavitiesdevelop. 3. Caudallimbs of theintraembryoniccoelomremainpairedstructuresanteriorlybuttheymergecaudally. Thisexplainswhytheventralmesentery is onlyobservable in theupperone-third of theabdominalcavity, whilethedorsalmesenteryexistsalongthewholelength of it.

  18. D) Furtherdevelopment of thepericardium Asthehearttubeloops, itsarterious and venousendsapproacheachother. Pericardialreflections (viscerallayer – parietallayertransition) arefoundaroundbothends. Betweenthetworeflectionsthetransverse sinus (T) is found.

  19. E) Furtherdevelopment of thepleura Developinglungsgrowintotheleft and rightpleuralcavities. Transitionbetweenthevisceral and parietallayers (pleuralreflection) surroundstheroot of lung and descentstothediaphragmasthepulmonary ligament. pulmonary ligament

  20. E) Furtherdevelopment of theperitoneum

  21. A 3D model of theperitonealcavitydemonstratingthat in theupperone-thirdtheleft and right body cavitiesremainseparated (bothventral and dorsalmesogastrium is seen), butcaudallytheymerge and onlythedorsalmesenterypersists.

  22. right left In theupperone-third of theabdominalcavitytheliver and the spleen developswithintheventral and dorsalmesogastrium, respectively. Astheresult of therotation of theforegut and relatedtransposition of epigastricstructures, thelessersacortheomentalbursaappears. Accordingtothecolourcodethat is derivedfromtheright body cavity (Pleasenote, thatthesidesarenotlabelledcorrectly in Prof. Réthelyi’sFunctionalanatomytextbook).

  23. Thankyouforyourattention!

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