Embryology L10: Digestive System
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Questions and Answers

What is the initial position of the duodenum before it shifts during rotation?

  • Posterior to the pancreas
  • Midline position (correct)
  • Left side of the abdominal cavity
  • Right side of the abdominal cavity

What is the primary blood supply to the duodenum?

  • Renal artery
  • Internal thoracic artery
  • Inferior mesenteric artery
  • Celiac artery and branches (correct)

During which week does the liver primordium appear as an outgrowth of the endodermal epithelium?

  • First week
  • Second week
  • Third week (correct)
  • Fourth week

What structure is formed by the ventral outgrowth of the bile duct?

<p>Gallbladder and cystic duct (C)</p> Signup and view all the answers

What happens to the liver’s hematopoietic function by the end of intrauterine life?

<p>It gradually subsides (C)</p> Signup and view all the answers

What is the weight of the liver at approximately the 10th week of development in relation to total body weight?

<p>10% (A)</p> Signup and view all the answers

The structures known as the lesser omentum and falciform ligament are derived from which part of the body?

<p>Mesoderm of the septum transversum (C)</p> Signup and view all the answers

What is the connection formed between the hepatic diverticulum and the foregut called?

<p>Bile duct (B)</p> Signup and view all the answers

Which part of the gut tube is primarily derived from endoderm?

<p>Epithelial lining (D)</p> Signup and view all the answers

What defines an organ as retroperitoneal?

<p>It lies against the posterior body wall with anterior coverage. (B)</p> Signup and view all the answers

What structure is formed from the dorsal mesentery in the region of the stomach?

<p>Dorsal mesogastrium (D)</p> Signup and view all the answers

Where does the ventral mesentery exist?

<p>In the region of the terminal esophagus, stomach, and upper duodenum. (A)</p> Signup and view all the answers

What is the function of mesenteries?

<p>To suspend the gut tube from the abdominal wall. (A)</p> Signup and view all the answers

What is derived from the dorsal pancreatic bud?

<p>Remaining part of the gland (D)</p> Signup and view all the answers

During which developmental week does the connection of the gut tube to the mesenchyme narrow?

<p>Fifth week (D)</p> Signup and view all the answers

What divides the ventral mesentery into the lesser omentum and falciform ligament?

<p>The development of the liver (A)</p> Signup and view all the answers

What artery supplies the entire length of the midgut?

<p>Superior mesenteric artery (D)</p> Signup and view all the answers

When does insulin secretion begin during development?

<p>Fifth month (B)</p> Signup and view all the answers

What is the function of peritoneal ligaments?

<p>To transport blood and lymphatics (A)</p> Signup and view all the answers

Which structure is formed at the site of the minor papilla in the duodenum?

<p>Accessory pancreatic duct (B)</p> Signup and view all the answers

Which part of the gut arises from the cephalic limb of the primary intestinal loop?

<p>Duodenum and jejunum (B)</p> Signup and view all the answers

What does the hindgut give rise to?

<p>Descending colon and sigmoid (B)</p> Signup and view all the answers

What forms the pancreatic connective tissue?

<p>Visceral mesoderm (A)</p> Signup and view all the answers

At what point in fetal development does the midgut communicate with the yolk sac?

<p>Through the vitelline duct (D)</p> Signup and view all the answers

What is formed from the ventral portion of the foregut once the respiratory diverticulum appears?

<p>Respiratory primordium (A)</p> Signup and view all the answers

How is the muscular coat of the esophagus differentiated in its upper two-thirds and lower third?

<p>Striated and smooth (C)</p> Signup and view all the answers

What direction does the stomach rotate around its longitudinal axis during development?

<p>90 degrees clockwise (D)</p> Signup and view all the answers

Which structure is a derivative of the dorsal mesogastrium during stomach development?

<p>Spleen (D)</p> Signup and view all the answers

Which part of the gut does the duodenum primarily originate from?

<p>Foregut and midgut junction (D)</p> Signup and view all the answers

What is the result of the faster growth of the posterior wall of the stomach during its rotation?

<p>Greater curvature and lesser curvature formation (B)</p> Signup and view all the answers

After the rotation of the stomach, which nerve innervates the anterior wall?

<p>Left vagus nerve (D)</p> Signup and view all the answers

What anatomical shape does the duodenum take as it forms during stomach rotation?

<p>C-shaped loop (C)</p> Signup and view all the answers

Flashcards

What are the sections of the developing gut tube?

The development of the primitive gut tube is divided into four sections: pharynx, foregut, midgut, and hindgut.

What germ layers contribute to the development of the digestive system?

The epithelial lining of the digestive tract is derived from the endoderm. The muscle, connective tissue, and peritoneal components of the gut wall are derived from the visceral mesoderm.

What are mesenteries?

Double layers of peritoneum that enclose an organ and connect it to the body wall. They provide pathways for vessels, nerves, and lymphatics to and from abdominal viscera.

What are intraperitoneal and retroperitoneal organs?

Organs suspended from body walls by mesenteries are called intraperitoneal. Organs that lie against the posterior body wall and are covered by peritoneum on their anterior surface are retroperitoneal.

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What are peritoneal ligaments?

Double layers of peritoneum that pass from one organ to another or from an organ to the body wall. They provide structural support and pathways for vessels.

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What is the dorsal mesentery and what structures does it form?

The dorsal mesentery extends from the lower end of the esophagus to the cloacal region of the hindgut. It forms the greater omentum, dorsal mesoduodenum, and dorsal mesocolon.

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What is the ventral mesentery?

The ventral mesentery exists only in the region of the terminal part of the esophagus, stomach, and upper part of the duodenum. It is derived from the septum transversum.

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How does the liver affect the ventral mesentery?

Growth of the liver divides the ventral mesentery into the lesser omentum (connecting the stomach, esophagus, and duodenum to the liver) and the falciform ligament (connecting the liver to the ventral body wall).

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Duodenum Position Shift

The duodenum, initially positioned in the midline, shifts to the right side of the abdomen due to the growth of the head of the pancreas.

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Duodenum and Pancreas Fixation

The duodenum and head of the pancreas move against the back wall of the abdomen and become fixed.

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Duodenum Recanalization

During the second month, the duodenum's internal space closes off due to cell growth but then opens up again.

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Liver Development

The liver starts developing as a bud from the endoderm, which is the inner layer of the gut tube.

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Bile Duct Formation

The connection between the liver bud and the gut narrows and becomes the bile duct.

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Gallbladder Development

The gallbladder and its connecting duct form from a small outgrowth of the bile duct.

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Liver Weight and Function

The liver's weight is about 10% of the body's weight at 10 weeks, partly due to blood production.

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Liver Hematopoiesis

The liver's blood production function gradually decreases, and it only produces a small amount of blood at birth.

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Esophagus Development

The esophagus develops from the dorsal portion of the foregut, separating from the ventral portion that forms the respiratory primordium (lung bud).

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Esophagus Muscle Types

The muscular coat of the esophagus has two distinct parts: the upper two-thirds are striated muscle controlled by the vagus nerve, and the lower third is smooth muscle controlled by the splanchnic plexus.

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Stomach Development

The stomach originates as a dilation of the foregut, undergoing significant growth and positional changes during development due to differential growth rates and interactions with surrounding organs.

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Stomach Rotation

The stomach rotates 90 degrees clockwise around its longitudinal axis, resulting in the left side facing anteriorly and the right side facing posteriorly. This rotation also reorients the vagus nerve innervation.

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Stomach Curvatures

The greater and lesser curvatures of the stomach develop as a result of the posterior wall growing faster than the anterior wall during the rotation.

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Duodenum Development

The duodenum forms from the terminal part of the foregut and the cephalic part of the midgut. It assumes a C-shaped loop as the stomach rotates, moving to the right.

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Spleen Development

The spleen develops from a mesodermal proliferation between the two leaves of the dorsal mesogastrium, remaining intraperitoneal and connected to the body wall and stomach by ligaments.

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Foregut and Midgut Junction

The junction between the foregut and midgut is directly distal to the origin of the liver bud.

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Pancreas Development

The pancreas develops from two buds: the dorsal and ventral buds, originating from the endodermal lining of the duodenum.

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Pancreatic Bud Locations

The dorsal pancreatic bud lies in the dorsal mesentery, while the ventral bud is close to the bile duct.

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Pancreatic Bud Fusion

As the duodenum rotates, the ventral pancreatic bud moves dorsally, eventually coming to lie below and behind the dorsal bud.

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Pancreatic Bud Contributions

The fusion of the dorsal and ventral buds forms the complete pancreas. The ventral bud forms the uncinated process and inferior part of the head, while the remaining part is derived from the dorsal bud.

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Pancreatic Duct Formation

Two main pancreatic ducts form: the main pancreatic duct and the accessory pancreatic duct. The main duct is formed by the distal part of the dorsal duct and the entire ventral duct.

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Pancreatic Duct Entry

The main pancreatic duct and bile duct enter the duodenum at the major papilla. The accessory duct enters at the minor papilla.

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Midgut Development

The midgut is suspended by a mesentery and connected to the yolk sac by the vitelline duct. It forms parts of the small intestine and the colon.

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Midgut Loop Development

The cephalic limb of the midgut loop develops into the jejunum, ileum, and part of the duodenum. The caudal limb forms the remaining ileum, cecum, appendix, ascending colon, and proximal transverse colon.

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Study Notes

Embryology L10: Digestive System

  • The development of the primitive gut tube and its derivatives is typically discussed in four sections:

    • Foregut: Extends from the oropharyngeal membrane to the respiratory diverticulum.
    • Midgut: Remainder of the foregut.
    • Hindgut: The remainder of the foregut.
  • Endoderm forms the epithelial lining of the digestive tract. Muscle, connective tissue, and peritoneal components of the gut wall are derived from visceral mesoderm.

Divisions of the Gut Tube

  • The foregut, midgut, and hindgut initially contact the mesenchyme of the posterior abdominal wall.
  • By the fifth week, these regions are suspended from the abdominal wall by the dorsal mesentery.
    • The stomach develops a dorsal mesogastrium (greater omentum).
    • The duodenum develops a dorsal mesoduodenum.
    • The colon develops a dorsal mesocolon.
  • The jejunal and ileal loops develop the mesentery proper.

Mesenteries

  • Double layers of peritoneum suspend portions of the gut tube and its derivatives from the dorsal and ventral body walls.
  • Organs enclosed by peritoneum are intraperitoneal; those against the posterior body wall are retroperitoneal (e.g., kidneys).
  • These layers/mesenteries provide pathways for vessels, nerves, lymphatics to and from abdominal viscera.

Foregut

  • Esophagus: The esophagus develops from the foregut as the respiratory diverticulum (lung bud) emerges.
  • The muscular coat is striated in the upper two-thirds and innervated by the vagus nerve; the lower third is smooth muscle and innervated by splanchnic plexuses.
  • Stomach: The stomach forms as a dilation of the foregut and rotates, changing position.
    • The left side faces anteriorly and the right side posteriorly.
    • The original posterior wall grows faster than the anterior wall to create the greater and lesser curvatures.
    • During further growth, the stomach rotates, moving the pyloric part to the right and the cardiac portion to the left.

Duodenum

  • Formed by the terminal part of the foregut and the cephalic portion of the midgut.
  • Initially in the midline, rotation leads to a C-shape and placement on the right side of the abdominal cavity.
  • The duodenum and head of the pancreas press against the dorsal body wall in a retroperitoneal position.
  • The lumen is obliterated then recanalized during the second month of development.
  • The duodenum is supplied by branches from both celiac and superior mesenteric arteries.

Liver and Gallbladder

  • The liver primordium (liver bud) appears in the third week, extending from the foregut.
  • The hepatic cells penetrate the septum transversum and connect to the foregut (duodenum), forming the bile duct.

Midgut

  • Develops into the duodenum, jejunum, part of the ileum, cecum, appendix, ascending colon, and proximal two-thirds of the transverse colon.
  • The midgut is suspended by the superior mesenteric artery and initially connected to the yolk sac via the vitelline duct. The gut and its mesentery elongate, forming the primary intestinal loop (first mesenteric loop).

Hindgut

  • The distal third of the transverse colon, the descending colon, sigmoid colon, rectum, and upper anal canal originate from the hindgut.
  • The endoderm of the hindgut develops into the internal lining of the bladder and urethra..

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Description

Explore the intricate development stages of the digestive system in this quiz focusing on embryology. Learn about the primitive gut tube, its divisions including foregut, midgut, and hindgut, as well as the role of endoderm and mesoderm in gut development. Test your knowledge of key concepts and terminologies related to this essential aspect of human embryology.

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