BODY CAVITIES,

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BODY CAVITIES, MESENTERIES DIAPHRAGM
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
• Somatic (parietal) layer under ectoderm
• 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
• A pericardial cavity the curve of U
• Two pericardioperitoneal canals (future pleural
  cavities) the proximal parts of the limbs of U
• 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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Dorsal Mesentery
Gut
Peritoneal Cavity
Ventral Mesentery
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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
• Outer layer forms thoracic wall
• 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
• Pericardial cavity
• 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
• Septum transversum forms the central tendon
• Dorsal mesentery of esophagus forms the right
  left crus
• Muscular ingrowth from lateral body wall
  posterolateral part (costal part)
• 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 cervical 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
• Both motor sensory supply of the diaphragm is
  derived from phrenic nerve
• 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
• Herniation of abdominal contents into thoracic
  cavity
• 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)