dr. ahmed fathalla ibrahim. intraembryonic coelom
TRANSCRIPT
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Dr. Ahmed Fathalla Ibrahim
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INTRAEMBRYONIC COELOM
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INTRAEMBRYONIC COELOM• Appears as isolated spaces in the lateral
mesoderm• In the 4th week, the spaces fuse to form a single
horseshoe-shaped (U-shaped) cavity• The coelom divides the lateral mesoderm into:1. Somatic (parietal) layer: under ectoderm2. Splanchnic (visceral) layer: over endoderm• Somatopleure = somatic mesoderm + overlying
ectoderm• Splanchnopleure = splanchnic mesoderm +
underlying endoderm
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INTRAEMBRYONIC COELOM
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INTRAEMBRYONIC COELOM• DERIVATIVES: It gives rise to three body
cavities:1. A pericardial cavity: the curve of U2. Two pericardioperitoneal canals (future pleural
cavities): the proximal parts of the limbs of U3. Two peritoneal cavities: the distal parts of the
limbs of U• Each cavity has a parietal layer (derived from
somatic mesoderm) & a visceral layer (derived from visceral mesoderm)
• FUNCTION: It provides space for the organs to develop & move
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DEVELOPMENT OF PERITONEAL CAVITY
• Major part of intraembryonic coelom• Develop from the distal parts of the limbs
of the U-shaped cavity• Originally, it is connected with
extraembryonic coelom (midgut herniates to the outside through this connection)
• At 10th week, it looses its connection with extraembryonic ceolom (when midgut returns to abdomen)
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DEVELOPMENT OF PERITONEAL CAVITY
• Originally, there were 2 peritoneal cavities
• After lateral folding of embryo, the peritoneum becomes a single cavity
HOW?
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Ventral Mesentery
Gut
Dorsal Mesentery
Peritoneal Cavity
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MESENTERIES• A MESENTERY is a double layer of
peritoneum that begins as an extension of the visceral peritoneum covering an organ
• The mesentery connects the organ to the body wall and transmits vessels and nerves to it
• Transiently, the dorsal & ventral mesenteries divide the peritoneal cavity into right & left halves
• The ventral mesentery disappears EXCEPT where stomach develops
• (WHY?)
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PERICARDIAL CAVITY
• Develops from the curve of the U-shaped cavity
• During formation of head fold, the heart & pericardial cavity move ventrocaudally & become anterior to the foregut (esophagus)
• It is bounded by an outer somatic & an inner visceral layer, forming the serous pericardium
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PERICARDIAL CAVITY
• Originally, it is connected with the 2 pericardioperitoneal canals
• Later on, it become separated from the 2 pericardioperitoneal canals
HOW?
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PERICARDIAL CAVITY• Originally, the bronchial buds are small
relative to the heart• Bronchial buds grow laterally into
pericardioperitoneal canals (future pleural cavities)
• Pleural cavities expand ventrally around heart & splits mesoderm into:
1. Outer layer: forms thoracic wall
2. Inner layer: pleuropericardial membrane
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PLEUROPERICARDIAL MEMBRANES
• THE PARTS SURROUNDING THE SEROUS PERICARDIUM: form the fibrous pericardium
• THE PARTS BEHIND THE HEART: fuse with the ventral mesentery of the esophagus (at 7th week), forming the mediastinum & separating pericardial from pleural cavities
• N.B.: The right pleural cavity separates from pericardial cavity earlier than left
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PLEURAL CAVITIES
• Develop from the 2 pericardiperitoneal canals
• Originally, they are connected with pericardial & peritoneal cavities
• Later on, they become separated from:
1. Pericardial cavity
2. Peritoneal cavity (HOW?)
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PLEUROPERITONEAL MEMBRANES
• Produced when developing lungs & pleural cavities expand into the body wall
• During 6th week, they fuse with dorsal mesentery of esophagus & septum transversum, separating pleural cavities from peritoneal cavity
• N.B.: The right pleural cavity separates from peritoneal cavity earlier than left
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DEVELOPMENT OF DIAPHRAGM
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DEVELOPMENT OF DIAPHRAGM
• The diaphragm develops from:1. Septum transversum: forms the
central tendon2. Dorsal mesentery of esophagus:
forms the right & left crus3. Muscular ingrowth from lateral body
wall: posterolateral part (costal part)4. Pleuroperitoneal membranes: small
portion of diaphragm
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SEPTUM TRANSVERSUM• At 3rd week, it is in the form of mass of
mesodermal tissue in the cranial part of embryo (opposite the 3rd, 4th & 5th cervical somites)
• At 4th week (during formation of head fold), it moves ventrocaudally forming a thick incomplete partition between thoracic & abdominal cavities
• At 6th week, it expands & fuse with dorsal mesentery of esophagus & pleuroperitoneal membranes to form the diaphragm
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INNERVATION OF DIAPHRAGM• Myoblasts from 3rd, 4th & 5th somites
migrate into diaphragm & bring their nerve fibers from them
• Nerve fibers derived from ventral rami of 3rd, 4th & 5th cervical nerves fuse to form phrenic nerve that elongate to follow the descent of diaphragm
1. Both motor & sensory supply of the diaphragm is derived from phrenic nerve
2. The part of diaphragm derived from lateral body wall receives sensory fibers from lower intercostal nerves
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ANOMALIES OF DIAPHRAGM
1. CONGENITAL DIAPHRAGMATIC HERNIA
2. EVENTRATION OF DIAPHRAGM
3. CONGENITAL HIATAL HERNIA
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CONGENITAL DIAPHRAGMATIC HERNIA
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CONGENITAL DIAPHRAGMATIC HERNIA
• A posterolateral defect of diaphragm• Cause: defective formation and/or fusion of
pleuroperitoneal membrane with other parts of diaphragm
• Effects: 1. Herniation of abdominal contents into
thoracic cavity2. Peritoneal & pleural cavities are connected
with one another• The defect usually occurs in the left side
(WHY?)
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EVENTRATION OF DIAPHRAGM
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EVENTRATION OF DIAPHRAGM
• Cause: failure of muscular tissue from body wall to extend into pleuroperitoneal membrane on one side
• Effects: superior displacement of abdominal viscera (surrounded by a part of diaphragm forming a pocket)
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CONGENITAL HIATAL HERNIA
• Herniation of part of the stomach through a large esophageal hiatus (opening)