Jejunum – Definition
| Category | Details |
|---|---|
| What is it? | The jejunum is the middle portion of the small intestine, located between the duodenum and ileum, responsible for the majority of nutrient absorption, especially sugars, amino acids, and fatty acids. |
| Characterized Anatomically By | – Begins at the duodenojejunal flexure (supported by the ligament of Treitz) – Makes up about 40% of the small intestine (after the duodenum) – Located mostly in the left upper quadrant of the abdomen |
| Characterized Physiologically By | – Continues enzymatic digestion initiated in the duodenum – Absorbs nutrients through highly folded mucosa – Rich in blood vessels for efficient absorption |
| Composed of (Major Parts/Units) | – Circular folds (plicae circulares) – Villi and microvilli – Mucosa, Submucosa, Muscularis externa, Serosa layers – Arterial supply: branches of the superior mesenteric artery (SMA) |
| Common Diseases | – Celiac disease – Crohn’s disease – Small bowel obstruction |
| Diagnosis (Most Common) | – Clinical Presentation: Malabsorption (diarrhea, weight loss, nutrient deficiencies), abdominal pain |
| Imaging Characteristics | – CT enterography / MR enterography for Crohn’s, mass lesions – Capsule endoscopy for mucosal evaluation |
| Laboratory Findings | – Nutrient deficiencies (e.g., iron, folate) – Positive celiac serology (anti-TTG, anti-endomysial antibodies) |
| Treatment | – Disease-specific: gluten-free diet (celiac), immunomodulators/biologics (Crohn’s), surgery for obstruction |
Major Parts of the Jejunum
| Part | Description |
|---|---|
| Plicae Circulares | Prominent permanent mucosal folds that slow passage of food and enhance absorption. |
| Villi and Microvilli | Increase surface area massively; key for nutrient absorption. |
| Arterial Arcades | Blood vessels supplying the jejunum; fewer and larger loops compared to the ileum. |
| Mesentery | Fan-shaped peritoneal structure attaching the jejunum to the posterior abdominal wall; contains blood vessels, lymphatics, and nerves. |
History of the Jejunum
| Era | Highlights |
|---|---|
| Ancient Times | Early anatomists recognized a middle portion of the intestines, but without functional understanding. |
| Middle Ages–Renaissance | Term “jejunum” derived from Latin jejunus meaning “fasting or empty” — because it was often found empty post-mortem. |
| 17th–18th Century | Continued anatomical exploration, recognizing differences between jejunum and ileum. |
| 19th Century | Advances in microscopy revealed the structure of villi and microvilli. |
| 20th–21st Century | Modern imaging (CT/MR enterography), capsule endoscopy, and better understanding of diseases like celiac and Crohn’s disease expanded clinical importance. |
MCQs on the Jejunum (with Full Explanations)
🧠 Basic Science MCQs
Q1. What structure greatly increases the absorptive surface area of the jejunum?
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A) Rugae
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B) Haustra
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C) Villi and microvilli
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D) Teniae coli
✅ Correct Answer: C) Villi and microvilli
Explanation:
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Correct: Villi and microvilli massively expand the surface area for nutrient absorption.
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Incorrect:
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A) Rugae: Stomach folds.
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B) Haustra: Sacculations in the colon.
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D) Teniae coli: Longitudinal muscle bands in colon.
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Q2. Which artery provides the main blood supply to the jejunum?
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A) Celiac artery
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B) Superior mesenteric artery
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C) Inferior mesenteric artery
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D) Splenic artery
✅ Correct Answer: B) Superior mesenteric artery
Explanation:
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Correct: The SMA supplies the jejunum via jejunal branches.
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Incorrect:
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A) Celiac artery: Supplies stomach, liver, spleen.
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C) Inferior mesenteric artery: Supplies the distal colon.
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D) Splenic artery: Supplies spleen.
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🏥 Clinical MCQs
Q3. A deficiency of which nutrient suggests a jejunal malabsorption issue?
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A) Vitamin B12
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B) Folate
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C) Bile salts
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D) Vitamin K
✅ Correct Answer: B) Folate
Explanation:
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Correct: Folate is primarily absorbed in the jejunum; deficiency suggests proximal small bowel disease.
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Incorrect:
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A) Vitamin B12: Absorbed in the ileum.
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C) Bile salts: Absorbed in the ileum.
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D) Vitamin K: Absorbed later in small intestine/colon.
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Q4. Which disease leads to flattening of villi in the jejunum?
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A) Crohn’s disease
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B) Ulcerative colitis
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C) Celiac disease
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D) Lactose intolerance
✅ Correct Answer: C) Celiac disease
Explanation:
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Correct: Celiac disease causes autoimmune destruction of villi leading to malabsorption.
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Incorrect:
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A) Crohn’s: Causes transmural inflammation but patchy, not diffuse villous flattening.
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B) Ulcerative colitis: Limited to colon.
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D) Lactose intolerance: No villous destruction.
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🖼️ Imaging MCQs
Q5. What imaging modality best evaluates mucosal detail of the jejunum?
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A) CT abdomen with contrast
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B) Barium enema
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C) MR enterography
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D) Chest X-ray
✅ Correct Answer: C) MR enterography
Explanation:
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Correct: MR enterography provides high-resolution imaging of the small bowel mucosa and is excellent for inflammatory diseases.
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Incorrect:
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A) CT: Good overview but less detailed mucosal imaging.
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B) Barium enema: Evaluates colon.
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D) Chest X-ray: Unrelated.
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Q6. Which imaging finding might you see in jejunal celiac disease on barium study?
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A) Nodular pattern with scalloping of folds
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B) Apple core lesion
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C) Pneumoperitoneum
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D) Curvilinear calcifications
✅ Correct Answer: A) Nodular pattern with scalloping of folds
Explanation:
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Correct: Loss of normal folds and nodularity in the jejunum are typical signs of celiac disease.
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Incorrect:
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B) Apple core lesion: Seen in colon cancer.
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C) Pneumoperitoneum: Free air (perforation).
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D) Calcifications: Suggests chronic pancreatitis or other causes.
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✅ MCQs completed with full explanations!
Memory Image Idea for the Jejunum – Offbeat and Fun
🎨 Idea:
Imagine a Massive Absorptive Forest:
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Tall trees (villi) stretching up to catch “nutrient rain” falling from the sky.
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Leaves and branches represent microvilli multiplying the surface area.
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Forest paths (plicae circulares) slow down the rain runoff, allowing maximum nutrient absorption.
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Stream (blood and lymphatic vessels) carries absorbed nutrients to the rest of the body!
Concept Name:
🌳🌧️ “The Nutrient Rainforest”
This captures:
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Anatomy (villi, microvilli)
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Function (absorption)
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The lush, dense, efficient environment of the jejunum!