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Questions and Answers
Which structures are formed by the differentiation of the intraembryonic mesoderm?
Which structures are formed by the differentiation of the intraembryonic mesoderm?
What is the primary function of splanchnic mesoderm in the gastrointestinal system?
What is the primary function of splanchnic mesoderm in the gastrointestinal system?
What does the allantois develop from in the early stages of embryonic development?
What does the allantois develop from in the early stages of embryonic development?
Which of the following statements is true regarding the vitelline duct?
Which of the following statements is true regarding the vitelline duct?
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What are the three main components of the intraembryonic coelom as described?
What are the three main components of the intraembryonic coelom as described?
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What does the somatopleure contribute to during embryonic development?
What does the somatopleure contribute to during embryonic development?
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How is the cloaca eventually divided during development?
How is the cloaca eventually divided during development?
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What is the role of the umbilical vein in adult anatomy?
What is the role of the umbilical vein in adult anatomy?
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What is formed when the lateral plate mesoderm splits?
What is formed when the lateral plate mesoderm splits?
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Which structures are found within the caudal free edge of the lesser omentum?
Which structures are found within the caudal free edge of the lesser omentum?
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What connects the gut tube to the ventral body wall?
What connects the gut tube to the ventral body wall?
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What happens to the peritoneal cavity after the rotation of the stomach?
What happens to the peritoneal cavity after the rotation of the stomach?
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How does the gall bladder connect to the biliary system?
How does the gall bladder connect to the biliary system?
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What is a significant change in the entrance to the omental bursa post-stomach rotation?
What is a significant change in the entrance to the omental bursa post-stomach rotation?
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From which embryological structure does the pancreas develop?
From which embryological structure does the pancreas develop?
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What is the consequence of the vitelline duct remaining attached to the umbilicus?
What is the consequence of the vitelline duct remaining attached to the umbilicus?
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What borders the epiploic foramen dorsally?
What borders the epiploic foramen dorsally?
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Which structure serves as a key landmark during midgut rotation?
Which structure serves as a key landmark during midgut rotation?
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How much does the midgut rotate during its return to the abdominal cavity?
How much does the midgut rotate during its return to the abdominal cavity?
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What condition results when the midgut does not return from the umbilical cord?
What condition results when the midgut does not return from the umbilical cord?
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During the development of the midgut, which limb grows more rapidly?
During the development of the midgut, which limb grows more rapidly?
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What is often referred to as 'The Mesentery' in the context of midgut development?
What is often referred to as 'The Mesentery' in the context of midgut development?
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Which developmental abnormality particularly involves intestinal contents lying externally and covered by the amnion?
Which developmental abnormality particularly involves intestinal contents lying externally and covered by the amnion?
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What happens to the cecum during midgut rotation?
What happens to the cecum during midgut rotation?
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Study Notes
Digestive System
- Key Terms: Ventral folding morphogenesis, Vitelline duct, Mesentery, Cloacal membrane, Foregut, Midgut, Hindgut, Hox genes in Gl patterning, Liver, Celiac artery, Cranial mesenteric artery, Caudal mesenteric artery, Stomach, Duodenum, Dorsal mesogastrium, Ventral mesogastrium, Greater omentum, Lesser omentum, Omental bursa, Rumen, Non-glandular fore-stomachs, Colon, Rectum, Cloacal membrane, Urogenital sinus, Urorectal septum, Anal membrane, Meckel's diverticulum, Physiologic umbilical hernia, Umblical hernia, Omphalocele, Imperforate anus/atresia ani, Vascular ring anomalies.
Learning Objectives
- Describe the embryonic formation of the early gut tube.
- Name the embryonic tissues that give rise to the GI tract and its derivatives (e.g., liver).
- Describe the relationship between the yolk sac and the embryonic gut tube, and identify the connecting structure.
- Explain basic mechanisms for establishing cranial/caudal regional identity in development.
- Describe stomach development and how it varies between species.
- Describe the development of the omentum (greater and lesser) and its associated bursa.
- Describe liver development and inductive effects from nearby tissues.
- Identify two reasons why mesenteries are critical to the GI tract.
- Explain the vascular supply to different parts of the GI tract.
- Explain the role of physiologic herniation in abdominal organ development.
- Describe Meckel's diverticulum and related anomalies.
- Explain how different species' GI tracts develop specialized forms.
- Explain developmental defects and their clinical presentations.
Introduction and Review
- Endoderm initially forms the primitive endoderm lining the yolk sac.
- Definitive endoderm forms from cells migrating during gastrulation, replacing the hypoblast.
- Endoderm in the embryo connects to the yolk sac endoderm.
- Embryo bends and folds due to nervous system growth, creating craniocaudal and lateral folding (ventral folding morphogenesis).
Mesodermal Layers
- Intraembryonic mesoderm differentiates into paraxial, intermediate, and lateral plate mesoderm.
- Lateral plate mesoderm further splits into splanchnic (visceral) and somatic (parietal) mesoderm.
- Somatic mesoderm fuses with ectoderm to form somatopleure.
- Splanchnic mesoderm forms gut tube wall; endoderm forms epithelium.
Gut Tube Development
- Gut tube develops with a dorsal mesentery.
- Nerves, blood vessels, and lymphatics run through mesentery.
- Septum transversum is a mesodermal layer.
- Septum transversum partially separates developing heart/lungs from abdominal organs.
- Gut is divided into foregut, midgut, and hindgut sections.
Midgut
- Foregut begins at the buccopharyngeal membrane to distal of the liver bud/duodenal papillae.
- Midgut extends from duodenum distal to liver bud to left colic flexure.
- Structures of the midgut are supplied by branches of the cranial mesenteric artery.
- Hindgut extends from left colic flexure to midpoint of anal canal.
- Hindgut structures are supplied from branches of the caudal mesenteric artery.
Caudal Foregut
- Foregut development discussed in relation to pharynx.
- Proximal foregut includes the esophagus; thoracic structures descend.
- Diaphragm separates the thorax and forms an opening for esophagus into the abdomen.
Simple Stomach
- The stomach initially forms as a dilation of the gut tube.
- Dorsal surface (greater curvature) grows faster than ventral (lesser curvature).
- Stomach rotates 90 degrees longitudinally and rotates again 90 degrees around its dorso-ventral axis.
- Dorsal mesentery becomes the greater omentum; ventral mesentery forms the lesser omentum.
Ruminant Stomach
- This stomach has forestomachs (rumen, reticulum, omasum) and one glandular portion (abomasum).
- Rumen is largest part.
- Rumen, reticulum, and omasum aid in grinding and digesting food.
- Abomasum is comparable to a simple stomach's pyloric portion.
Liver
- Endoderm (from duodenum) gives rise to the liver.
- Signals from septum transversum (BMPs) and cardiac mesoderm (FGFs) specify cells.
- Liver grows into septum transversum, connecting to the duodenum as bile duct.
Lesser Omentum
- Mesentery between liver and stomach/duodenum.
- Includes bile duct, portal vein, hepatic arteries.
Malformations of the Digestive System
- Atresia and stenosis (blockage/narrowing of segments).
- Aganglionosis (absence of autonomic nerves).
- Rotation defects (e.g., situs inversus).
- Omphalocele/umbilical hernia (midgut doesn't return).
- Umbilical hernia (protrusion at the umbilicus).
- Imperforate Anus (incomplete development).
- Vascular ring anomalies (constriction of esophagus).
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Description
Test your knowledge on the embryonic development of the digestive system. This quiz covers key terms, structures, and mechanisms involved in the formation of the gut tube and its derivatives. Learn about the relationships and identities in the early stages of development.
