Anatomy 534: Development of Body Cavities PDF

Anatomy 534 Development of Body Cavities 1 The intra-embryonic coelom is one continuous cavity. The coelom has to be divided into 4 body cavities: - 1 pericardial yet...

Anatomy 534 Development of Body Cavities 1 The intra-embryonic coelom is one continuous cavity. The coelom has to be divided into 4 body cavities: - 1 pericardial yet - 2 pleural I - 1 peritoneal Two partitions must develop to do this - the diaphragm and the fibrous Inroads pericardium. Tart hi That portion of the intra-embryonic coelom that crosses the midline of the embryo cranial to the buccopharyn- geal membrane will form the peri- cardial cavity. The cavity comes to lie ventral to the pharynx. I g o Tithrane Buccophorous membrane LUNY  Anatomy 534 Development of Body Cavities 2 Esophagus At this stage the pericardial cavity is in buttube free communication with the peritoneal cavity through the pericardioperitoneal canals. Th marriage Fungs main flffll take me Tbd feat Erik admost The endocardial tube will invaginate the dorsal surface of the pericardial cavity and becomes suspended within Pericardial it by the dorsal mesocardium. We sac will continue with the development of the heart in a later lecture. laudium visceralpericardium parietalpericardium  Anatomy 534 Development of Body Cavities 3 Formation of the Fibrous Pericardium i The fibrous pericardium separates the pericardial from the pleural cavities. Two pleuro- pericardial membranes (sheets of somatic mesoderm) form the fibrous pericardium. These membranes form when the developing lungs grow into the body wall. heart Past inum mediastinum parietater viceryla E 1D ftfflfffiffffffdg.gg ffÉi ÉÉ É É of Pay.li diu HIt pericardial Development of the Diaphragm The diaphragm separates the pleural cavities from the peritoneal cavity. It is formed through fusion of tissue from 3 sources: 1. The septum transversum, a mass of mesoderm located between the heart and the developing liver. It forms the central portion of the diaphragm - including the central tendon. 2. Two pleuroperitoneal membranes, sheets of somatic mesoderm that grow anteriorly from the posterior body wall. These are largely responsible for the peripheral regions of the muscle diaphragm, pleura and perioneum that cover its upper and lower surfaces respectively. 3. The dorsal mesentery of the esophagus which is invaded by developing muscle cells and forms the crura of the diaphragm. FTP Anatomy 534 Development of Body Cavities 4 ID 3 parts EXAM what they develop into The septum transversum is an incomplete septum formed in the neck region by fusion of the third, forth and fifth cervical segments (C3, 4, 5). The decent of the heart from the I IE if EI neck pushes the septum caudally pulling is nerve supplied (derived from C3,4,5) with it. Meanwhile the pleuroperitoneal membranes on either side start to grow medially from the body wall fusing with the septum transversum anteriorly to the esophagus. Fibro I.im Diaphragmatic ei iif ii io partitiest.si pleuroperietonea folds Positional Changes in the Diaphragm During week 4 the diaphragm begins formation in the cervical region. By week 8 it has descended, carrying his the phrenic nerves with it - explaining their long length Anatomy 534 Development of Body Cavities 5 Development of the Pleural Cavities With the development of the lung buds, the splanchnic mesoderm covering them is invaginated into the pericardioperitoneal canals. This portion of each canal becomes the pleural cavity on each side. mustache fhff.ph mural cavith The pleuropericardial membranes grow inward rostally to form the fibrous pericardium. The pleuroperitoneal membranes grow inward caudally to help form the diaphragm. The embryo now has four cavities: a pericardial cavity, two pleural cavities, and a peritoneal cavity. Anatomy 534 Development of Body Cavities 6 Development of the Lungs About week 4 of development, a median longitudinal groove, the laryngotracheal groove, develops in the pharyngeal floor. The edges of the groove fuse and forms a laryngotracheal tube and its lumen is separated from the foregut. As the lung buds grow, they migrate inferiorly and further invaginate the intra-embryonic coelom. This part of the coelom forms the pleural sacs. Each lung receives a covering of visceral pleura derived from splanchnic mesoderm. The parietal pleura is formed from somatic mesoderm. Phuffation train 1 I 11 E c Root of lung Stiitiitation