Podcast
Questions and Answers
What is the length of the cecum?
What is the length of the cecum?
Which is the longest segment of the colon?
Which is the longest segment of the colon?
Which of the following sections of the colon does not have a mesentery?
Which of the following sections of the colon does not have a mesentery?
At which point does the sigmoid colon start?
At which point does the sigmoid colon start?
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What is the Jackson's membrane?
What is the Jackson's membrane?
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What is the primary vascular supply to the midgut portion of the colon?
What is the primary vascular supply to the midgut portion of the colon?
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Which of the following is true about the rectosigmoid colon?
Which of the following is true about the rectosigmoid colon?
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The rectum begins variably from which anatomical landmark?
The rectum begins variably from which anatomical landmark?
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What is the corresponding spinal level of the origin of the inferior mesenteric artery (IMA)?
What is the corresponding spinal level of the origin of the inferior mesenteric artery (IMA)?
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Which artery is considered the second branch of the superior mesenteric artery (SMA)?
Which artery is considered the second branch of the superior mesenteric artery (SMA)?
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Which of the following is to about the right colic artery
Which of the following is to about the right colic artery
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Which of the following is true about the blood supply of the sigmoid colon?
Which of the following is true about the blood supply of the sigmoid colon?
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What forms the Gastrocolic Trunk of Henle?
What forms the Gastrocolic Trunk of Henle?
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Where does the marginal artery of Drummond run?
Where does the marginal artery of Drummond run?
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Which of the following is true about Toltd's fascia
Which of the following is true about Toltd's fascia
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What is the clinical significance of the 'arc of Riolan'?
What is the clinical significance of the 'arc of Riolan'?
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What is a function of the superior hypogastric plexus?
What is a function of the superior hypogastric plexus?
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Flashcards
Colon Length
Colon Length
The colon is approximately 150-165 cm long.
Tenia Coli
Tenia Coli
Three longitudinal bands in the colon wall.
Haustra
Haustra
Sacculations (pouches) of the colon, formed by tenia coli.
Cecum Structure
Cecum Structure
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Transverse Colon Mesentery
Transverse Colon Mesentery
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Sigmoid Mesocolon
Sigmoid Mesocolon
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Rectosigmoid Colon
Rectosigmoid Colon
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Colon blood supply
Colon blood supply
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Middle colic artery origin
Middle colic artery origin
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Ileocolic artery location
Ileocolic artery location
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Right colic artery frequency
Right colic artery frequency
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IMA origin
IMA origin
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Left colic artery's function
Left colic artery's function
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Superior sigmoidal artery
Superior sigmoidal artery
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Marginal artery of Drummond
Marginal artery of Drummond
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Ileocolic vein drainage
Ileocolic vein drainage
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Gastrocolic Trunk of Henle frequency
Gastrocolic Trunk of Henle frequency
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Toldt's fascia description
Toldt's fascia description
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Study Notes
Colon Anatomy and Blood Supply
- Length: Colon varies in length, approximately 150-165 cm.
- Structure: The colonic wall contains 3 longitudinal bands (tenia coli), creating haustra (sacculations).
- Regions: The cecum, ascending colon, hepatic flexure, transverse colon, splenic flexure, descending colon, sigmoid colon, and rectosigmoid colon are anatomically distinct regions.
Cecum
- Dimensions: ~5-10 cm in length and ~7.5 cm in diameter.
- Wall: Relatively thinner compared to other colon regions.
- Mesentery: No mesentery.
- Jackson's Membrane: A prececal fibrous band containing small blood vessels, clinically insignificant.
Ascending Colon
- Length: ~15-20 cm.
- Location: Extends from cecum to liver.
- Mesentery: No mesentery.
- Position: Overlaps the right kidney and ends under the right liver.
Transverse Colon
- Length: ~45-50 cm (longest colon portion).
- Location: From liver to spleen.
- Redundancy: Most redundant portion of the colon.
- Embryological Origins: Proximal 2/3rd midgut; distal 1/3rd hindgut.
- Mesentery: Has a mesentery (transverse mesocolon).
- Mesocolon Content: The transverse mesocolon contains the middle colic artery and is enveloped by visceral peritoneum of both sides, extending over the pancreas.
Descending Colon
- Length: ~12-30 cm.
- Location: From splenic flexure to left psoas muscle, transitioning to the sigmoid colon.
- Mesentery: No mesentery.
Sigmoid Colon
- Length: ~40 cm (variable).
- Location: Starts at iliac crest, lateral psoas muscle.
- Wall: Relatively more thick-walled.
- Mesentery: Has a mesentery (sigmoid mesocolon).
- Mesocolon Shape: Inverted V shape; inter-sigmoid recess between limbs; left ureter exiting at apex.
Rectosigmoid Colon
- Definition: Segment (~7-8 cm) of colon where taenia coli merge into a single layer, marking the rectum's beginning.
- Mesentery: Shorter, more tethered mesentery compared to the colon.
- Rectum Beginning: Begins variably between the promontory and S3.
Arterial Supply
- Sources: Blood from both superior mesenteric artery (SMA) and inferior mesenteric artery (IMA).
- SMA Branches:
- Middle colic artery: Constant; arises from SMA inferior border of pancreas; travels through the transverse mesocolon.
- Ileocolic artery: Constant; terminal SMA branch; runs posterior or anterior to the superior mesenteric vein (SMV); sometimes branches to right colic artery.
- Right colic artery: Variable (~25% of cases); can branch from the ileocolic artery or occasionally the SMA.
- IMA Branches:
- Left colic artery: Originates distal to IMA; supplies left colon; collateralizes with middle colic via marginal artery of Drummond.
- Sigmoidal branches: 2-5 branches to the sigmoid colon, forming a marginal artery near the bowel wall; superior (constant) and inferior (variable) divisions.
- SMA-IMA Collateralization:
- Marginal artery of Drummond: Constant; within 3cm of bowel wall; important for mesenteric windows.
- Arc of Riolan: Rare (~5.5-11.4% of cases); collateral vessel; indicative of possible mesenteric stenosis.
Venous Drainage
- Ileocolic vein: Drains into SMV (98%) or Gastrocolic Trunk of Henle (GTH) (~2%); important for ligation during colon cancer surgery.
- Right colic vein: Variable (~50-90%); drains into SMV or GTH.
- Gastrocolic Trunk: Formed by right gastroepiploic, superior right colic, and superior pancreaticoduodenal veins; drains into SMV; present in ~80% of patients.
Nerve Supply
- Superior hypogastric plexus: (L4/L5); important for genitourinary function; high IMA ligation can protect this.
Other Structures
- White line of Toldt: Peritoneal reflection of colon.
- Toldt's fascia: Interface of visceral and parietal layers of the colon, not as thick as a fascia.
- Vascularity: Variable; depends on BMI.
Clinical Significance
- Dissecting along anterior mesocolon maintains avascular plane.
- Avoid caudal or anterior traction on transverse mesocolon to avoid accidental avulsion of Gastrocolic Trunk.
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Test your knowledge on the anatomy of the colon as relevant to his general surgeon and surgical oncologist.
