GIT- Embryology

• Pancreas development occurs from two endodermal buds of the foregut: the dorsal and ventral pancreatic buds.

• Dorsal bud:

  • Gives rise to the body, tail, and superior part of the head of the pancreas.

  • Its proximal part forms the main pancreatic duct (duct of Wirsung) in most individuals.

• Ventral bud:

  • Contributes to the uncinate process and inferior part of the pancreatic head.

  • The distal part of the ventral bud fuses with the dorsal bud during rotation.

• Option analysis:

  • Insulin secretion starts at the end of intrauterine life ❌

    • Insulin secretion begins earlier in fetal life, around the 10th–12th week of gestation.

  • Dorsal bud forms the uncinate process ❌

    • The uncinate process arises from the ventral bud, not the dorsal.

  • Ventral bud forms entire head of pancreas ❌

    • Ventral bud only forms the inferior part of the head and uncinate process, not the entire head.

  • The distal part of dorsal pancreatic bud forms the main pancreatic duct ❌

    • It is actually the proximal part of the dorsal bud that contributes to the main pancreatic duct.

  • Proximal part of dorsal bud forms the main pancreatic duct ✅

    • Correct embryological origin of the duct of Wirsung.

The superior mesenteric artery (SMA) arises from the abdominal aorta at the level of L1, just below the celiac trunk. It supplies all midgut derivatives, which include:

• Lower half of the duodenum (beyond the bile duct opening)

• Jejunum and ileum

• Cecum, appendix, ascending colon, and proximal two-thirds of the transverse colon

The SMA ensures these regions receive a rich supply of oxygenated blood for absorption and digestion.

❌ Incorrect Options

• Celiac trunk: Supplies foregut derivatives — stomach, liver, pancreas, spleen, and upper duodenum.

• Inferior mesenteric artery: Supplies hindgut — distal one-third of transverse colon, descending colon, sigmoid colon, and rectum.

• Internal iliac artery: Supplies pelvic organs, not the intestine.

• Common iliac artery: Divides into external and internal iliac arteries — does not directly supply gut.

The gastrointestinal tract has contributions from different embryonic layers:

• Endoderm → gives rise to the epithelial lining of the gut and its glands (e.g., liver, pancreas).

• Mesoderm (splanchnic layer of lateral plate mesoderm) → forms the connective tissue, blood vessels, and smooth muscle layers of the gut, including the muscularis externa.

• Ectoderm → contributes only at the ends of the gut (oral cavity epithelium, anal canal below pectinate line).

• Neural crest cells → migrate into the gut wall to form the enteric nervous system (Auerbach’s and Meissner’s plexuses), but they do not form the muscle itself.

• Neural tube → forms the central nervous system, not gut layers.

Thus, the muscularis externa is derived from splanchnic mesoderm.

Why the other options are wrong

Endoderm ❌ → forms epithelium and glands, not muscle.
Ectoderm ❌ → forms oral/anal lining, not gut muscle.
Neural crest cells ❌ → form enteric ganglia, not smooth muscle.
Neural tube ❌ → forms CNS, unrelated to gut wall.

🔎 Step 1: Background

The pancreas develops from two buds arising from the endodermal foregut:

• Dorsal pancreatic bud → Appears first, gives rise to the majority of the pancreas.

• Ventral pancreatic bud → Later rotates dorsally, fuses with the dorsal bud, and contributes to specific parts.

✅ Derivatives of the Dorsal Pancreatic Bud

• Neck

• Body

• Tail

• Most of the head (upper part)

✅ Derivatives of the Ventral Pancreatic Bud

• Lower part of the head

• Uncinate process

• Major contribution to the main pancreatic duct (duct of Wirsung)

❌ Correct Answer (Incorrect Option): Entire main pancreatic duct

• The main pancreatic duct is formed mostly from the ventral duct and only partly from the distal portion of the dorsal duct.

• So, saying the dorsal bud gives rise to the “entire” main pancreatic duct is incorrect.

Correct Answer:
Superior mesenteric artery ✅

Why this is correct

• During embryonic development, the midgut undergoes physiological herniation into the umbilical cord around the 6th week because of rapid elongation.

• The midgut loop rotates a total of 270° counterclockwise:

  • 90° during herniation,

  • 180° during its return to the abdominal cavity around the 10th week.

• The axis of this rotation is the superior mesenteric artery (SMA), which supplies the entire midgut.

• The SMA passes through the base of the midgut loop, dividing it into a cranial limb (small intestine) and a caudal limb (large intestine).

Why the other options are incorrect

Abdominal aorta ❌

• Main trunk vessel; SMA branches from it, but the aorta itself is not the axis of rotation.

Celiac trunk ❌

• Supplies the foregut; not involved in midgut development.

Inferior mesenteric artery ❌

• Supplies the hindgut; not part of midgut rotation.

Inferior vena cava ❌

• Venous structure, unrelated to midgut arterial supply or rotation.

During embryonic development, the stomach and surrounding organs are suspended in the peritoneal cavity by two mesenteries:

🔹 Ventral Mesogastrium

• Found only in the foregut region

• Connects the stomach and upper duodenum to the anterior abdominal wall

• Derivatives include:

  • Falciform ligament (connects liver to anterior wall)

  • Lesser omentum (hepatogastric and hepatoduodenal ligaments)

  • Ligaments of the liver (e.g., coronary ligament)

🔹 Dorsal Mesogastrium

• Present throughout the GI tract

• Connects stomach to posterior abdominal wall

• Derivatives include:

  • Greater omentum

  • Gastrosplenic ligament

  • Splenorenal ligament

  • Lienorenal ligament

🔍 Option-by-Option Breakdown:

• Liver ❌
  → Not a direct mesogastrium derivative; it grows into the ventral mesogastrium, but is not itself derived from it.

• Ileorenal ligament ❌
  → No such anatomical structure exists. Possibly a confusion with splenorenal (lienorenal) ligament, which is a dorsal mesogastrium derivative.

• Stomach ❌
  → Derived from foregut endoderm, not from mesogastrium. It is suspended by both mesenteries but not a derivative.

• Greater omentum ❌
  → A classic dorsal mesogastrium derivative.

• Falciform ligament ✅
  → Ventral mesogastrium derivative, connects the liver to the anterior abdominal wall.

🔬 Clinical Relevance:

• The falciform ligament contains the ligamentum teres hepatis, the remnant of the fetal umbilical vein.

• Surgical anatomy of these ligaments is crucial during procedures like liver resections and gallbladder surgery.

During embryological development, the midgut undergoes a specific sequence of rotations around the axis of the superior mesenteric artery (SMA):

1. Physiological herniation into the umbilical cord during the 6th week.

2. The midgut loop rotates 90° counterclockwise during herniation.

3. As the intestines return to the abdominal cavity during the 10th week, they rotate an additional 180° counterclockwise, making a total rotation of 270° counterclockwise.

4. This places the cecum in the right lower quadrant and ensures proper alignment of the small and large intestines.

Option breakdown:

• 270° clockwise – Incorrect: Rotation is counterclockwise, not clockwise.

• 180° counterclockwise – Incorrect: Rotation totals 270°, not just 180°.

• 90° clockwise – Incorrect: The first rotation is 90° counterclockwise, not clockwise.

• 270° counterclockwise – Correct: This is the normal developmental rotation direction and degree.

• 90° counterclockwise – Incorrect: Represents only the initial phase of rotation, not the full process.

The normal herniation of the midgut is a physiological process during fetal development and is essential for proper positioning and fixation of the intestines in the abdominal cavity.

🔍 Key Points about Normal Midgut Herniation:

• When it occurs:

  • Begins around week 6 of intrauterine life, when the midgut loop herniates into the umbilical cord due to rapid elongation of the gut and limited space in the abdominal cavity.

  • The herniated gut returns to the abdomen by week 10.

• What rotates and how:

  • During herniation and retraction, the midgut undergoes a total of 270° counter-clockwise rotation (when viewed from the front) around the axis of the superior mesenteric artery (SMA).

  • First 90° occurs during herniation; the remaining 180° happens as the gut retracts back into the abdomen.

• What is involved:

  • The entire midgut is involved, which includes both small and large intestines — not just one.

• The stomach:

  • Rotates independently, earlier in development (~week 4–5), rotating 90° clockwise, and is not part of midgut herniation.

❌ Why the Other Options Are Incorrect:

🧠 What Actually Happens:

1. Week 6: Midgut herniates due to rapid growth.

2. Week 6–10: Undergoes 270° counter-clockwise rotation around SMA.

3. Week 10: Gut returns to abdominal cavity in its final position.

• The septum transversum (mesoderm) contributes to Kupffer cells, hematopoietic cells, and connective tissue of liver.

• The biliary system (intrahepatic and extrahepatic ducts, gallbladder, cystic duct) develops from the endodermal hepatic diverticulum, not from the septum transversum.

• The midgut loop has a cranial limb and a caudal limb:

  • Cranial limb → develops into most of the small intestine (distal duodenum, jejunum, and upper ileum).

  • Caudal limb → develops into lower ileum, cecum, appendix, ascending colon, and proximal 2/3 of transverse colon.

• The duodenum (proximal parts) develops mainly from the foregut (upper half) and cranial limb of midgut loop (distal half), not from the caudal limb.

Thus, among the options, duodenum does not arise from the caudal end.

Why the Other Options Are Wrong ❌

Cecum

• Develops from the caudal limb of the intestinal loop.

Lower part of ileum

• Also from the caudal limb.

Appendix

• Outgrowth of the cecum → caudal limb derivative.

Ascending colon

• Direct derivative of the caudal limb.

The liver develops as an outgrowth from the endoderm of the foregut, specifically from the hepatic diverticulum, which arises from the ventral wall of the distal foregut during the 4th week of development.

This hepatic diverticulum divides into:

• A larger cranial part → forms the liver parenchyma and intrahepatic bile ducts.

• A smaller caudal part → forms the gallbladder and cystic duct.

Variations in lobulation or shape of the liver are therefore foregut-derived anomalies, often benign and detected incidentally on imaging.

❌ Incorrect Options

• Laryngoesophageal diverticulum: Forms the respiratory system (trachea, lungs), not the liver.

• Midgut: Forms small intestine (distal duodenum to proximal 2/3 of transverse colon) — unrelated to liver.

• Hindgut: Forms distal 1/3 of transverse colon, descending colon, sigmoid colon, rectum, not liver.

• Yolk sac: Source of primordial germ cells and early blood cells, but not hepatic tissue.

Meckel’s diverticulum is the most common congenital anomaly of the gastrointestinal tract. It results from the incomplete obliteration of the vitelline (omphalomesenteric) duct, which connects the embryonic midgut to the yolk sac.

To help remember its features, the “Rule of 2s” is often used.

🔍 The Rule of 2s (Clinical Mnemonic):

• 2 inches long ✅

• 2 feet from the ileocecal valve ✅

• Found in 2% of the population ✅

• Often presents in the first 2 years of life

• Can contain 2 types of ectopic tissue: gastric and pancreatic

• Occurs 2:1 in males vs females

✅ Why “Present at the mesenteric border of ileum” is Incorrect:

• Meckel’s diverticulum arises from the antimesenteric border of the ileum — opposite to the mesenteric attachment.

• This is because it originates from the vitelline duct, which was connected anteriorly to the yolk sac during development.

• So, “mesenteric border” is a false anatomical location for Meckel’s diverticulum.

❌ Why the Other Options Are Correct:

Summary:

The primary intestinal loop arises during midgut development and has two limbs:

• Cranial limb → forms the distal duodenum, jejunum, ileum.

• Caudal limb → forms the cecum, vermiform appendix, ascending colon, and proximal two-thirds of the transverse colon.

The rectum, however, does not come from the midgut at all. It is a hindgut derivative. The hindgut gives rise to the distal third of transverse colon, descending colon, sigmoid colon, rectum, and upper anal canal.

So, while cecum, appendix, ascending colon, and proximal 2/3 of transverse colon are correctly from the caudal limb of the midgut, the rectum is not.

During embryonic development, the midgut undergoes rapid elongation and temporarily herniates into the extraembryonic coelom of the umbilical cord around the 6th week. As it elongates, the midgut loop rotates a total of 270° counterclockwise around the axis of the superior mesenteric artery (SMA):

• First 90° rotation: Occurs during physiological herniation.

• Remaining 180° rotation: Occurs as the intestines return to the abdominal cavity around the 10th week.

This rotation correctly positions the intestines in the abdominal cavity, with the duodenojejunal junction to the left and the cecum in the right lower quadrant.

Other options:

• Inferior mesenteric artery – Incorrect: Supplies the hindgut, not the midgut, so it is not the axis of rotation.

• Umbilical artery – Incorrect: Involved in placental circulation, not gut rotation.

• Celiac trunk – Incorrect: Supplies the foregut, not the midgut.

• Vitelline artery – Incorrect: Early embryonic vessel associated with the yolk sac, not the midgut rotation.

• The right and left hepatic ducts drain bile from the respective lobes of the liver.

• They join to form the common hepatic duct.

• The cystic duct (from the gallbladder) then joins the common hepatic duct → together they form the common bile duct.

• The common bile duct later unites with the main pancreatic duct at the hepatopancreatic ampulla (ampulla of Vater), which opens into the second part of the duodenum at the major duodenal papilla.

Now the other options:

• Cystic duct and right hepatic duct ❌ – Right hepatic duct first joins left hepatic duct to form common hepatic duct.

• Cystic duct and pancreatic duct ❌ – Pancreatic duct only joins later at ampulla of Vater.

• Left hepatic duct and right hepatic duct ❌ – They form the common hepatic duct, not the common bile duct.

• Common hepatic and pancreatic duct ❌ – That union forms the hepatopancreatic ampulla, not the common bile duct.

• Normally, during development (6th week), the midgut undergoes physiological herniation into the umbilical cord because the abdominal cavity is too small.

• By the 10th week, the gut returns to the abdominal cavity after completing a 270° counterclockwise rotation.

• If this return fails, the bowel remains herniated and covered by peritoneum and amnion, forming an omphalocele.

Why the Other Options Are Wrong ❌

Persistence of vitelline duct

• Leads to Meckel’s diverticulum.

• Not due to failure of gut return.

Retrocolic hernia

• An internal hernia due to abnormal rotation of the gut, not failure of return.

Gastroschisis

• Congenital defect where bowel herniates through the abdominal wall (usually right of umbilicus).

• Here, the bowel is not covered by peritoneum.

• Cause: abdominal wall closure defect, not failed return of physiological hernia.

Megacolon (Hirschsprung disease)

• Due to failure of migration of neural crest cells, leading to absence of enteric ganglia.

• Not related to herniation or return of the gut.

The hindgut gives rise to:

• Distal third of the transverse colon, descending colon, sigmoid colon, rectum, and anal canal.

Anal canal embryology:

• Upper two-thirds: Derived from hindgut endoderm → columnar epithelium, autonomic innervation.

• Lower one-third: Derived from ectoderm of proctodeum → stratified squamous epithelium, somatic innervation.

• The pectinate (dentate) line marks the junction of endodermal and ectodermal origins.

Option breakdown:

• Descending colon – Incorrect: Entirely endodermal.

• Sigmoid colon – Incorrect: Entirely endodermal.

• Anal canal – Correct: Has dual origin: endoderm (upper) + ectoderm (lower).

• Transverse colon – Incorrect: Derived from midgut (endoderm).

• Rectum – Incorrect: Upper rectum is endodermal; no ectodermal contribution except anal canal.

Key point:
The anal canal is unique in the hindgut because it is derived from both endoderm and ectoderm, creating differences in epithelium type and nerve supply.

During embryonic development, the diaphragm forms from four key components:

1. Septum transversum

2. Pleuroperitoneal membranes

3. Dorsal mesentery of esophagus

4. Body wall musculature

Failure of the pleuroperitoneal membranes to close the pericardioperitoneal canals results in a defect in the posterolateral part of the diaphragm, most commonly on the left side → known as a Bochdalek hernia (type of congenital diaphragmatic hernia).

This allows abdominal viscera (e.g., stomach, intestines, spleen) to herniate into the thoracic cavity, compressing the developing lungs, leading to pulmonary hypoplasia and respiratory distress at birth.

❌ Incorrect Options

• Omphalocele: Failure of midgut loops to return to abdominal cavity; herniation through umbilical ring, covered by peritoneum and amnion.

• Gastroschisis: Lateral abdominal wall defect, usually right of umbilicus; intestines protrude without a covering.

• Hiatal hernia: Herniation of stomach through esophageal hiatus; occurs after birth, not due to pleuroperitoneal membrane defect.

• Tracheoesophageal fistula: Abnormal communication between trachea and esophagus due to defective foregut partitioning, unrelated to diaphragm development.

To understand this question, we need to review pancreatic embryology:

🔬 Embryological Development of the Pancreas:

• The pancreas develops from two buds:

  • Dorsal pancreatic bud: arises first and forms most of the pancreas (body, tail, and part of the head).

  • Ventral pancreatic bud: forms the uncinate process and the inferior portion of the head of the pancreas.

🔄 Normal Rotation:

• The ventral bud rotates posteriorly (behind the duodenum) from the right side to fuse with the dorsal bud on the left.

• Fusion results in a single pancreas with a unified duct system.

⚠️ Malrotation:

• If the ventral bud splits into two parts (which is normal), but they rotate in opposite directions (abnormal), they may encircle the duodenum and compress it.

✅ Correct Answer:

Annular pancreas

An annular pancreas occurs when two ventral buds rotate in opposite directions and form a ring of pancreatic tissue around the duodenum, which can lead to duodenal obstruction.

❌ Why the other options are incorrect:

• Ectopic pancreas: Pancreatic tissue found in abnormal locations (e.g., stomach, duodenum) but not related to ventral bud malrotation.

• Accessory pancreatic bud: Refers to additional buds, but not necessarily due to faulty rotation.

• Accessory pancreas: Synonym for ectopic pancreas.

• Accessory pancreatic duct: A normal remnant of the dorsal bud (duct of Santorini), not a result of ventral bud malrotation.

The medial umbilical ligament (sometimes referred to as medial umbilical cord) is a fibrous remnant of the obliterated umbilical arteries. During fetal life, the umbilical arteries carry deoxygenated blood from the fetus to the placenta. After birth, they close off and become fibrous structures that run along the inside of the anterior abdominal wall, covered by folds of peritoneum.

That’s why in a 5-year-old child, if the surgeon resects a fibrous remnant of a fetal artery, it must be the medial umbilical ligament.

❌ Incorrect Options Explained

• Lateral umbilical cord ❌
  This is not a fetal remnant. The lateral umbilical fold actually contains the inferior epigastric vessels, which are normal postnatal blood vessels, not obliterated fetal vessels.

• Median umbilical cord ❌
  This is the remnant of the urachus, a fetal structure connecting the bladder to the umbilicus. It is not derived from arteries, but from the allantois.

• Ligamentum venosum ❌
  This is the remnant of the ductus venosus, which shunted blood from the left umbilical vein to the inferior vena cava in fetal life. Not related to umbilical arteries.

• Ligamentum teres hepatis ❌
  This is the remnant of the left umbilical vein, which carried oxygenated blood from the placenta to the fetus. Again, not an artery.

During embryonic development, the midgut forms a U-shaped primary intestinal loop that herniates temporarily into the umbilical cord and later returns to the abdomen after rotation.

This loop has two limbs:

• Cephalic (upper) limb → gives rise to the distal duodenum, jejunum, and most of the ileum.

• Caudal (lower) limb → gives rise to the distal ileum, cecum, appendix, ascending colon, and proximal two-thirds of the transverse colon.

Therefore, the jejunum is a derivative of the cephalic limb of the primary intestinal loop.

❌ Incorrect Options

• Appendix: Derived from the caudal limb along with the cecum.

• Cecum: Also from the caudal limb.

• Ascending colon: From the caudal limb.

• Right colic flexure: Formed by the junction of ascending and transverse colon, both caudal-limb derivatives.

Correct Answer:
Endoderm ✅

Why this is correct

• The parenchyma (functional tissue) of the liver, biliary apparatus, and pancreas is derived from the endoderm of the foregut.

• Specifically:

  • Liver: arises from the hepatic diverticulum (endodermal outgrowth of foregut).

  • Gallbladder and bile ducts: develop from the cystic diverticulum of the hepatic diverticulum (endodermal origin).

  • Pancreas: develops from dorsal and ventral pancreatic buds (endodermal outgrowths of duodenum).

• The stroma and connective tissue of these organs, however, are derived from splanchnic (lateral plate) mesoderm.

Why the other options are incorrect

Ectoderm ❌

• Forms nervous system, epidermis, and neural crest derivatives; not hepatobiliary or pancreatic parenchyma.

Intermediate mesoderm ❌

• Gives rise to urogenital structures (kidneys, gonads, reproductive ducts), not liver or pancreas.

Lateral mesoderm ❌

• Specifically the splanchnic mesoderm contributes connective tissue, blood vessels, and stroma of these glands, but not the functional parenchyma.

Paraxial mesoderm ❌

• Forms somites → axial skeleton, skeletal muscle, and dermis; unrelated to GI glands.

The gastrointestinal (GI) epithelium is lined with a variety of specialized cells that originate from pluripotent stem cells located at the base of the crypts of Lieberkühn. One such important cell type is the goblet cell.

🔍 Goblet Cells: Mucus-Secreting Defenders

• Function: Goblet cells secrete mucin, which becomes mucus upon hydration. Mucus forms a protective, lubricating layer over the epithelium.

• Location: Found throughout the small and large intestines, increasing in number from the duodenum to the colon.

• Origin: Derived from intestinal stem cells (pluripotent) in the crypts.

• Appearance: Named for their goblet-like shape; they stain pale with H&E and deeply with PAS stain (for mucin).

❌ Why the Other Options Are Incorrect:

Summary:

✅ Goblet cells are the mucus-secreting cells of the intestinal epithelium that arise from pluripotent stem cells in the crypts.

Meckel’s diverticulum (the “rule of 2s”):

• True diverticulum of the ileum.

• Located on the anti-mesenteric border of the ileum, about 2 feet from the ileocecal valve.

• Present in ~2% of the population.

• Can contain ectopic gastric or pancreatic tissue → may cause ulceration and bleeding.

• Caused by persistence of the vitelline (omphalomesenteric) duct.

Why the other options are correct (not odd)

• It can function as ectopic pancreatic tissue ✅ → True, may also contain gastric tissue.

• It is also called ileal diverticulum ✅ → Correct name.

• It is present in 2% of the population ✅ → Matches the “rule of 2s.”

• It is due to a persistent vitelline duct ✅ → Correct embryological cause.

• It forms on mesenteric side ❌ → Wrong; it is on the anti-mesenteric side.

✅ Correct Answer

Omphalocele is usually a right-sided abdominal wall defect without a covering membrane.

That statement is false because it actually describes gastroschisis, not omphalocele.

• Omphalocele → midline defect at umbilical ring, covered by amnion + peritoneum, due to failure of midgut return, often linked with chromosomal anomalies and neural tube defects.

• Gastroschisis → right-sided, no covering membrane, less often associated with anomalies.

Correct Answer:
Spleen ✅

Why this is correct

• The spleen is a vascular lymphoid organ that develops from mesenchymal cells in the dorsal mesogastrium (not from the endodermal gut tube).

• During development, as the stomach rotates, the spleen is carried to the left hypochondrium.

• Functionally, it is part of the immune and circulatory systems: filters blood, stores red blood cells, and initiates immune responses.

• Unlike the liver, gallbladder, and pancreas (which develop from endodermal outgrowths of the foregut), the spleen has a mesodermal origin.

Why the other options are incorrect

Gall bladder ❌

• Derived from the endoderm of the hepatic diverticulum (foregut derivative).

Liver ❌

• Also derived from endoderm (hepatic diverticulum of foregut).

Pancreas ❌

• Develops from dorsal and ventral pancreatic buds (endodermal origin).

Salivary gland ❌

• Develop from oral ectoderm and endodermal epithelium, not from dorsal mesogastrium mesenchyme.

Meckel’s diverticulum is a congenital pouch resulting from the persistence of the vitelline (omphalomesenteric) duct.

• Location:

  • Usually arises from the antimesenteric border of the ileum, about 2 feet proximal to the ileocecal junction.

• Clinical relevance:

  • Can cause painless rectal bleeding, intestinal obstruction, or inflammation (diverticulitis).

• Rule of 2s:

  • Occurs in 2% of the population, 2 feet from the ileocecal valve, 2 inches long, often symptomatic by age 2, and may contain 2 types of ectopic tissue (gastric or pancreatic).

Option breakdown:

• Gastro-esophageal junction – Incorrect: Proximal GI tract; unrelated.

• Gastro-duodenal junction – Incorrect: Proximal small intestine; not typical site.

• Ileo-cecal junction – Correct: Terminal ileum near the ileocecal valve, the classic site of Meckel’s diverticulum.

• Gastro-colic junction – Incorrect: Not an anatomical junction.

• Duodeno-jejunal junction – Incorrect: Proximal small intestine; Meckel’s occurs distally.

Key point:
Meckel’s diverticulum is a distal ileal remnant of the vitelline duct, typically found near the ileocecal junction, making it a common cause of pediatric GI bleeding.

The uncinate process and part of the head of the pancreas develop from the ventral pancreatic bud, which originates from the endoderm of the foregut. During development, the ventral bud rotates posteriorly around the duodenum to fuse with the dorsal pancreatic bud, which forms the rest of the head, neck, body, and tail.

Incorrect options:

• Septum transversum: Contributes to the diaphragm and liver, not the pancreas.

• Dorsal pancreatic bud: Forms most of the pancreas (body, tail, part of the head) but not the uncinate process.

• Mesoderm of duodenum: Pancreas develops from endoderm, not mesoderm.

• Endoderm of duodenum: While the buds are endodermal, the specific structure forming the uncinate process is the ventral bud, not just general duodenal endoderm.

🔎 Step 1: Understanding the Question

The hepatic bud (also called the liver diverticulum) develops from the endoderm of the foregut. The key is to remember which structures in the liver come from endoderm (the hepatic bud itself) and which come from mesoderm.

✅ Correct Answer: Parenchyma of liver

• The parenchyma of the liver (hepatocytes and bile duct epithelium) develops from the endodermal cells of the hepatic bud.

• These endodermal cells proliferate into the septum transversum mesenchyme and form the bulk of the functional tissue of the liver.

❌ Why the Other Options Are Incorrect

• Hepatic sinusoids → Derived from the vitelline veins and umbilical veins, i.e., mesodermal in origin.

• Hemopoietic cells → Derived from mesoderm of the septum transversum, not from the hepatic bud.

• Stroma of liver (connective tissue framework) → Mesodermal origin.

• Kupffer cells (specialized macrophages) → Derived from mesoderm (monocyte lineage), not from the endodermal hepatic bud.