Download Development of body cavities

Embryology:
Development of Body Cavity,
Serous Membranes and Gut (I)
M1 Gross and Developmental Anatomy
11:00-11:50 AM, January 8, 2009
Dr. Milton M. Sholley
Professor of Anatomy and Neurobiology
ANIMATIONS:
The web address listed on syllabus page 29 has changed.
The new address is:
http://cna.uc.edu/embryology/chapter6/animations/contents.htm
Dorsal View of the Embryonic Disc at ~Day 15
Cells from the epiblast migrate through the primitive groove
to replace cells of the hypoblast,
thus forming the definitive endoderm.
Buccopharyngeal
membrane
Epiblast (blue)
Primitive groove
Definitive endoderm
Cloacal membrane
Larsen Website
gast.avi
Dorsal View of the Embryonic Disc
The animation will depict ingress of cells from the epiblast through
the primitive groove to form the intraembryonic mesoderm (~day 16).
Buccopharyngeal
membrane
The dashed line shows the
approximate plane of section
used for the cross sectional
drawings on syllabus page 32.
Primitive groove
Epiblast (blue)
Cloacal membrane
Definitive endoderm
Larsen Website
gast.avi
Differentiation of Intra-embryonic Mesoderm
and
Formation of Intra-embryonic Coelom
Cross sections through the embryonic disc
(Syllabus page 30)
~19 days
~20 days
Adapted from: Langman's Medical Embryology
The Embryonic Disc
is located between and attached to both the Yolk Sac and
the Amniotic Sac, as shown here at the end of the third week.
Cut edge of
amniotic membrane
The dashed line shows the
approximate plane of section
used for the cross sectional
drawings on syllabus page 30.
Yolk sac
Larsen Website
neurul.avi
Differentiation of Intra-embryonic Mesoderm
and
Formation of Intra-embryonic Coelom
Cross sections through the embryonic disc
(Syllabus page 30)
~19 days
~20 days
Adapted from: Langman's Medical Embryology
During the fourth week,
the flat embryonic disc is converted by folding
in both lateral and head-to-tail directions
into a 3-dimensional vertebrate body form.
Animation begins
at ~21 days
Animation ends
at ~25 days
Yolk sac
Larsen Website
neurul.avi
Lateral Folding of the Embryonic Disc
-Converts the flat disc into a tubular embryo
-Closes-off the intra-embryonic coelom
-Pinches-off the tubular gut from the yolk sac
-Expands amniotic cavity to surround embryo
Cross sections of the embryo (Syllabus page 31)
Adapted from: Langman's Medical Embryology
 The abdominopelvic cavity is lined with parietal peritoneum.
 The gut is covered with visceral peritoneum.
 Mesenteries are double layers of peritoneum that connect parietal and visceral layers.
 The space between parietal and visceral layers is called the peritoneal cavity.
Kidney
Aorta
Dorsal mesentery
Parietal peritoneum
Visceral peritoneum
Peritoneal cavity
Intraperitoneal gut
 Mesenteries suspend the gut and gut-associated organs
within the abdominopelvic cavity.
 Mesenteries DO NOT suspend the gut and gut-associated organs
within the peritoneal cavity.
 The peritoneal cavity normally contains nothing but a small amount of
fluid that moistens the surfaces of the peritoneum.
 The peritoneal cavity can expand to contain a large amount of
fluid under abnormal circumstances.
Head to Tail Folding
The animation will start at ~21 days
and end at ~28 days.
Head end
Amniotic cavity
Tail end
Yolk sac
Larsen Website
folding.avi
Head to Tail
Folding
Note that the
head folding causes
relocation of the
heart primordium
and the mesoderm
cranial to it. The
mesoderm cranial
to the heart becomes
the septum transversum
and is relocated from
a cranial to a thoracic
position. The septum
transversum (shown
in green) will form
an important part of
the diaphragm.
Adapted from:
Langman's Medical
Embryology
Model of a 5-week embryo (left) and a cross section
at the level of the septum transversum (right). (Syllabus page 33)
Note the location of the pericardioperitoneal canals and the formation of the diaphragm.
Adapted from: Langman's Medical Embryology
The coelom is divided into thoracic and abdominal cavities by
Formation of the Diaphragm
Division of the Thoracic Cavity
(Syllabus page 34)
Adapted from: Langman's Medical Embryology
Diaphragmatic Hernia
•It is usually congenital (Bochdalek’s Hernia) and, if it is extensive, it is often
associated with severe hypoplasia of the lungs that becomes fatal at birth.
•It is more common on the left side of the body because the pericardioperitoneal
canal on the left tends to close later than that on the right.
From: Langman's Medical Embryology
Head to Tail
Folding
and
Formation of
the Primitive Gut
(Syllabus page 35)
Adapted from:
Langman's Medical
Embryology
Head to Tail Folding
The animation will start at ~21 days
and end at ~28 days.
Head end
Amniotic cavity
Tail end
Yolk sac
Larsen Website
folding.avi
Formation of the Primitive Gut
resulting from
Head to Tail Folding
Endodermal sheet
Starting at
~20 days
Yolk sac
Ending at
~26 days
Larsen Website
9-1.avi
 The abdominopelvic cavity is lined with parietal peritoneum.
 The gut is covered with visceral peritoneum.
 Mesenteries are double layers of peritoneum that connect parietal and visceral layers.
 The space between parietal and visceral layers is called the peritoneal cavity.
Kidney
Aorta
Dorsal mesentery
Parietal peritoneum
Visceral peritoneum
Peritoneal cavity
Intraperitoneal gut
 Mesenteries suspend the gut and gut-associated organs
within the abdominopelvic cavity.
 Mesenteries DO NOT suspend the gut and gut-associated organs
within the peritoneal cavity.
 The peritoneal cavity normally contains nothing but a small amount of
fluid that moistens the surfaces of the peritoneum.
 The peritoneal cavity can expand to contain a large amount of
fluid under abnormal circumstances.
Derivatives of the ventral mesentery are shown in blue
and derivatives of the dorsal mesentery are shown in red.
From: Langman's Medical Embryology
What are the adult derivatives of the primitive gut regions?
See syllabus pages 36-37.
Foregut becomes what?
Midgut becomes what?
Hindgut becomes what?
Adapted from:
Langman's Medical
Embryology
Foregut artery is celiac.
Midgut artery is SMA.
Hindgut artery is IMA.
Obliteration of Chorionic Cavity
by
Enlargement of Amniotic Cavity
Amniotic cavity
See this series
of diagrams on
page 146 of Larsen
(3rd ed.)
Animation:
Starts at 4 weeks
Ends at 8 weeks
Yolk sac
Chorionic cavity
Larsen Website
amnio.avi
Oligohydramnios: Too little amniotic fluid.
Polyhydramnios: Too much amniotic fluid.
For an interesting discussion
of causes and consequences of these two conditions,
see Larsen, 3rd edition, page 490.