Transcript 1.Body cavities2008-02

Dr. Ahmed Fathalla Ibrahim
INTRAEMBRYONIC COELOM
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 ectoderm
2. Splanchnic (visceral) layer: over endoderm
• Somatopleure = somatic mesoderm +
overlying ectoderm
• Splanchnopleure = splanchnic mesoderm +
underlying endoderm
INTRAEMBRYONIC COELOM
INTRAEMBRYONIC COELOM
•
DERIVATIVES: It gives rise to three body
cavities:
1. A pericardial cavity: the curve of U
2. Two pericardioperitoneal canals (future
pleural cavities): the proximal parts of the
limbs of U
3. 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
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)
DEVELOPMENT OF
PERITONEAL CAVITY
• Originally, there were 2 peritoneal
cavities
• After lateral folding of embryo, the
peritoneum becomes a single cavity
HOW?
Dorsal
Mesentery
Gut
Peritoneal
Cavity
Ventral
Mesentery
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?)
PERICARDIAL CAVITY
• Develops from the curve of the Ushaped 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
PERICARDIAL CAVITY
• Originally, it is connected with the 2
pericardioperitoneal canals
• Later on, it become separated from the
2 pericardioperitoneal canals
HOW?
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
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
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?)
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
DEVELOPMENT OF DIAPHRAGM
DEVELOPMENT OF DIAPHRAGM
• The diaphragm develops from:
1. Septum transversum: forms the
central tendon
2. Dorsal mesentery of esophagus:
forms the right & left crus
3. Muscular ingrowth from lateral body
wall: posterolateral part (costal part)
4. Pleuroperitoneal membranes: small
portion of diaphragm
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
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
ANOMALIES OF DIAPHRAGM
1. CONGENITAL DIAPHRAGMATIC
HERNIA
2. EVENTRATION OF DIAPHRAGM
3. CONGENITAL HIATAL HERNIA
CONGENITAL DIAPHRAGMATIC
HERNIA
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 cavity
2. Peritoneal & pleural cavities are connected
with one another
• The defect usually occurs in the left side
(WHY?)
EVENTRATION OF DIAPHRAGM
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)
CONGENITAL HIATAL HERNIA
• Herniation of part of the stomach
through a large esophageal hiatus
(opening)