Early Development of the GIT & Anatomy of Esophagus Flashcards
What are the different stages of the primitive gut during the longitudinal folding?
Pre-somite embryo
Embryo with 7 somites
Embryo with 14 somites
What are the two different folding formations of the primitive gut?
Longitudinal and transverse
Which protein is related to stomach and esophagus formation?
CSOX2
Which protein is related to pancreas development?
PDX1
Which protein is related to liver development?
HOX
Which protein is related to vitalline duct development?
CDXC
What is the primitive gut lined with?
Endoderm
What is the endoderm that lines the primitive gut supported by?
Intraembryonic splanchnic mesoderm
What does the endoderm form?
Tissue lining of digestive tract (epithelium)
The parenchyma or secretory cells of the glands that open into the digestive system
The parenchyma or secretory cells of which organs’ glands are made by the endoderm?
Liver, gallbladder, pancreas
What does the mesoderm form?
The smooth muscle
Connective tissue
Blood vessels
What does the foregut give rise to?
Respiratory tree
Esophagus
Liver, gallbladder, pancreas
Duodenum
Which parts of the duodenum arise from the foregut?
The first part and the first half of the second part, as far as the entrance of the common bile duct
Which parts of the respiratory tree give rise to what?
Anterior part –> trachea and lungs
Posterior part –> oesophagus
Which major blood vessels supply the foregut?
Aortic arches
Dorsal aorta
Celiac trunk
At what point does the celiac trunk supply the foregut?
T12
What is the neural innovation of the foregut?
Parasympathetic –> vagus nerve
Sympathetic –> Greater thoracic splanchnic nerve (T5 to T9)
Which part of the mediastinum will the oesophagus run across?
Through the superior and into the inferior mediastinum
Which major blood vessel is the midgut supplied by?
Superior mesenteric artery
Which major blood vessel is the hindgut supplied by?
Inferior mesenteric artery
What causes the gradual separation between the foregut and the respiratory diverticulum?
Tracheoesophageal septum
What structures arise once the tracheoesophageal septum is formed?
Pharynx
Trachea
Lung buds
Esophagus
The respiratory system is what compared to the primitive foregut?
Respiratory system is an outgrowth of the primitive foregut
Where does the respiratory diverticulum arise from?
The cranial part of the primitive foregut
What is caused by oesophageal Artesia or tracheoesophageaal fistula?
Polyhydramnios
–> Proximal blind-end of oesophagus
–> OR Communication between oesophagus and trachea
What is the result of elongation of the oesophagus?
The stomach will be pushed towards the abdominal cavity, from the cervical region
What is congenital hiatal hernia?
Failure of the oesophagus to elongate, pulling the stomach through the oesophageal opening
What is a common sign of congenital hiatal hernia?
Heartburn sensation
At what level does the oesophagus enter the diaphragm?
T10, left of the median plate
What is the process of occlusion and recanalization of the foregut?
The epithelium of the tube (endoderm) will proliferate rapidly and fill the lumen
Appearance of vacuoles with degeneration of epithelial cells occur
What can failure of recanalization lead to?
Artesia or stenosis
What is oesophageal stenosis?
Narrowing of the esophagus due to incomplete or partial re-canalization of lumen
What can oesophageal stenosis lead to?
Poor vacuole formation (level of section E1)
Narrow lumen (level of section E3)
What is oesophageal artesia?
Failure of the lumen to recanalize
What can oesophageal artesia lead to?
No vacuole formation (level of section F1)
Transverse septum (level of section F3)
What is the stomach attached to the dorsal abdominal wall by?
Dorsal mesogastrium
What is the stomach attached to the ventral abdominal wall by?
Ventral mesogastrium
What is the mesogastrium?
Double layer peritonium
When does the growth and the rotation of the stomach occur?
Week 5 to 6
Why does the rotation of the stomach occur?
The dorsal wall grows more rapidly that the ventral –> greater curvature will be on the left
What is the process of the growth and rotation of the stomach?
The stomach rotates 90o clockwise around its longitudinal axis
In which axis direction does the stomach rotate?
Anteroposterior axis
After the rotation of the stomach where will the right vagal nerve be?
Towards the back
What is the function of the oesophagus?
Food transportation, no digestion
Where does the esophagus begin?
At C6, a continuation of the pharynx
Follows the curve of the vertebral column
Where does the oesophagus run across?
Runs in the posterior mediastinum, across the superior and into the inferior sections
Where does the oesophagus also pass through?
The superior thoracic aperture
Where does the change in the mucosa from oesophageal to gastric occur?
Esophagogastric junction at T11
Where is the inferior oesophageal sphincter located?
Above the esophagogastric junction
What is the function of the inferior oesophageal sphincter?
Physiological prevents reflux, requires a stimulus from autonomic system
What are the different parts of the oesophagus?
Cervical
Thoracic
Abdominal
Which oesophageal part is the longest?
Thoracic part
What are the three natural constrictions of the oesophagus?
- Junction between pharynx and oesophagus
- By left principal bronchus and aortic arch
- At oesophageal hiatus
Where are the natural constrictions located?
Junction between pharynx and oesophagus –> C6
Left principal bronchus and aortic arch –> T4/T5
Eosphageal hiatus –> T10
What is the arterial supply for the upper 1/3 of the oesophagus?
Inferior thyroid artery comes from the thyrocervical trunk
What is the arterial supply of the middle 1/3 of the oesophagus?
Descending thoracic artery
What is the arterial supply of the lower 1/3 of the oesophagus?
Left gastric artery comes from the celiac trunk
What is the venous drainage of the upper 1/3 of the oesophagus?
Inferior thyroid veins –> systemic venous system, will eventually drain into brachiocephalic
What is the venous drainage for the middle 1/3 of the oesophagus?
Azygous and hemizygous veins
What is the venous drainage for the lower 1/3 of the oesophagus?
Left gastric vein –> will end up in the portal vein circulation system!!
Drains the lower end of the oesophagus and the fundus of the stomach
What happens in case of oesophageal hypertension?
Blood does not smoothly return to the liver so alternative options are activated
One of: anastomosis –> can lead to dilation and congestion
Results in: Oesophageal varices
What will be the result/ sign of oesophageal varices endoscopic view?
Bleeding caused by the rupture of veins
What is the lymph drainage for the upper 1/3 of the oesophagus?
Deep cervical nodes
What is the lymph drainage of the middle 1/3 of the esophagus?
Superior and posterior mediastinal nodes.
What is the lymph drainage of the lower 1/3 of the esophagus?
Left gastric blood vessels and celiac nodes
Why is lymph drainage and its location important?
In case of cancers, when doing biopsy you will have to check the other organs that drain into the same region in case of metastasis or spread
What is the innervation of the oesophagus?
Parasympathetic –> Right and left vagal nerves (X)
Sympathetic –> Fibres of the inferior cervical and thoracic ganglia
What is the purpose of villi in the small intestine?
To increase the mucosal surface
What are the layers of the mucosa?
Epithelium
Lamina propia
Muscularis mucosa
What is the function of the epithelium layer?
Protection and absorption
What is the function of the lamina propria?
Support
What is the function of the muscularis mucosa?
Mucosal motility
What is the function of glands?
Secretion
What are the components of the submucosa?
Glands
Submucosal (Meissner) plexus
What are the components of the muscularis layer?
Inner - circular
Myenteric (Auerbach) plexus
Outer - longitudinal
What is the function of the inner circular and outer longitudinal layers of the muscularis?
Motility
What is the function of serosa?
Support
What is the serosa?
A covering in the peritoneum
What is the ‘serosa’ of the esophagus?
Adventia
What is the histology of the epithelium layer of the mucosa?
Non-keratinised stratified squamous epithelium
What is the histology of the lamina propria layer of the mucosa?
Loose CT, vessels and glands
What is the histology of the muscularis mucosa layer of the mucosa?
Contains smooth muscles
What is the histology of the oesophageal glands of the submucosa?
Mucus-secreting glands, protect mucosa
What is the histology of the oesophageal cardiac glands of the submucosa?
Additional mucus-secreting glands in the lamina propria, protect against stomach acid
What is the histology of the muscularis layer of the oesophagus?
Striated (skeletal muscles) in the upper two-thirds and innervated by vagus
Smooth in the lower third and innervated by splanchnic plexus
What is specific about the skeletal muscles in the upper two thirds of the oesophagus?
Even though skeletal muscles are usually voluntary, these are involuntary.
What is the histology of the stomach?
Simple columnar epithelium