Septum transversum
Encyclopedia
The septum transversum is a thick mass of cranial mesenchyme
that gives rise to parts of the thoracic diaphragm
and the ventral mesentery
of the foregut in the developed human being.
on day 22. During craniocaudal folding it assumes a position caudal to the developing heart at the level of the cervical vertebrae. During subsequent weeks the dorsal end of the embryo grows much faster than its ventral counterpart resulting in an apparent descent of the ventrally located septum transversum. At week 8 it can be found at the level of the thoracic vertebrae.
. During the descent of the septum, the phrenic nerve
is carried along and assumes its descending pathway.
During embryonic development of the thoracic diaphragm
, myoblast
cells from the septum invade the other components of the diaphragm. They thus give rise to the motor and sensory innervation of the muscular diaphragm by the phrenic nerve
.
part of the septum transversum gives rise to the central tendon
of the diaphragm and is the origin of the myoblasts that invade the pleuroperitoneal folds resulting in the formation of the muscular diaphragm.
The caudal part of the septum transversum is invaded by the hepatic diverticulum
which divides within it to form the liver and thus gives rise to the ventral mesentery
of the foregut, which in turn is the precursor of the lesser omentum
, the visceral peritoneum of the liver
and the falciform ligament
.
Though not derived from the septum transversum, development of the liver is highly dependent upon signals originating here. Bone Morphogenic Protein 2 (BMP-2), BMP-4, and BMP-7 produced from the septum transversum join Fibroblast Growth Factor (FGF) signals from the cardiac mesoderm induce part of the foregut to differentiate towards a hepatic fate.
Mesenchyme
Mesenchyme, or mesenchymal connective tissue, is a type of undifferentiated loose connective tissue that is derived mostly from mesoderm, although some are derived from other germ layers; e.g. some mesenchyme is derived from neural crest cells and thus originates from the ectoderm...
that gives rise to parts of the thoracic diaphragm
Thoracic diaphragm
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
and the ventral mesentery
Ventral mesentery
-Development:The cephalic portion of the septum transversum takes part in the formation of the diaphragm, while the caudal portion into which the liver grows forms the ventral mesentery ....
of the foregut in the developed human being.
Origins
The septum transversum originally arises as the most cranial part of the mesenchymeMesenchyme
Mesenchyme, or mesenchymal connective tissue, is a type of undifferentiated loose connective tissue that is derived mostly from mesoderm, although some are derived from other germ layers; e.g. some mesenchyme is derived from neural crest cells and thus originates from the ectoderm...
on day 22. During craniocaudal folding it assumes a position caudal to the developing heart at the level of the cervical vertebrae. During subsequent weeks the dorsal end of the embryo grows much faster than its ventral counterpart resulting in an apparent descent of the ventrally located septum transversum. At week 8 it can be found at the level of the thoracic vertebrae.
Innervation
After successful craniocaudal folding the septum transversum picks up innervation from the adjacent ventral rami of spinal nerves C3, C4 and C5, thus forming the precursor of the phrenic nervePhrenic nerve
The phrenic nerve originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves in humans....
. During the descent of the septum, the phrenic nerve
Phrenic nerve
The phrenic nerve originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves in humans....
is carried along and assumes its descending pathway.
During embryonic development of the thoracic diaphragm
Thoracic diaphragm
In the anatomy of mammals, the thoracic diaphragm, or simply the diaphragm , is a sheet of internal skeletal muscle that extends across the bottom of the rib cage. The diaphragm separates the thoracic cavity from the abdominal cavity and performs an important function in respiration...
, myoblast
Myoblast
A myoblast is a type of embryonic progenitor cell that gives rise to muscle cells .The muscle cells can be skeletal muscle, smooth muscle, and cardiac muscle....
cells from the septum invade the other components of the diaphragm. They thus give rise to the motor and sensory innervation of the muscular diaphragm by the phrenic nerve
Phrenic nerve
The phrenic nerve originates mainly from the 4th cervical nerve, but also receives contributions from the 5th and 3rd cervical nerves in humans....
.
Derivatives
The cranialCranial
Cranial may refer to:* an adjective related to the cranium* Anatomical terms of location* Cranial cavity* Cranial Osteopathy...
part of the septum transversum gives rise to the central tendon
Central tendon
The central tendon of the diaphragm is a thin but strong aponeurosis situated slightly anterior to the vault formed by the muscle, resulting in longer posterior muscle fibers....
of the diaphragm and is the origin of the myoblasts that invade the pleuroperitoneal folds resulting in the formation of the muscular diaphragm.
The caudal part of the septum transversum is invaded by the hepatic diverticulum
Hepatic diverticulum
-External links:* http://www.meddean.luc.edu/lumen/MedED/orfpath/hepaticd.htm* http://www.cincinnatichildrens.org/research/div/dev-biology/fac-labs/zorn-lab/liver-dev.htm* http://www.embryology.ch/anglais/sdigestive/leber02.html...
which divides within it to form the liver and thus gives rise to the ventral mesentery
Ventral mesentery
-Development:The cephalic portion of the septum transversum takes part in the formation of the diaphragm, while the caudal portion into which the liver grows forms the ventral mesentery ....
of the foregut, which in turn is the precursor of the lesser omentum
Lesser omentum
The lesser omentum is the double layer of peritoneum that extends from the liver to the lesser curvature of the stomach and the start of the duodenum.- Structure :...
, the visceral peritoneum of the liver
Liver
The liver is a vital organ present in vertebrates and some other animals. It has a wide range of functions, including detoxification, protein synthesis, and production of biochemicals necessary for digestion...
and the falciform ligament
Falciform ligament
The falciform ligament is a ligament that attaches the liver to the anterior body wall.It is a broad and thin antero-posterior peritoneal fold, falciform in shape, its base being directed downward and backward and its apex upward and backward...
.
Though not derived from the septum transversum, development of the liver is highly dependent upon signals originating here. Bone Morphogenic Protein 2 (BMP-2), BMP-4, and BMP-7 produced from the septum transversum join Fibroblast Growth Factor (FGF) signals from the cardiac mesoderm induce part of the foregut to differentiate towards a hepatic fate.
