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Jejunum and Ileum (Mobile Segment of the Small Intestine: ~6 m) - Coggle…
Jejunum and Ileum (Mobile Segment of the Small Intestine: ~6 m)
General Features & Topography
Dimensions
~6 m in total length; caliber progressively tapers from 3–4 cm (jejunum) down to ~2 cm (terminal ileum)
Location
Lies entirely within the inframesocolic compartment of the abdomen
Proportions
Jejunum: Proximal 2/5 of mobile small intestine
Ileum: Distal 3/5 of mobile small intestine
Loop Configuration
Composed of ~16 U-shaped intestinal loops, each featuring:
Two convex surfaces
A free convex border (facing the abdominal cavity)
An attached border (anchored to the mesentery)
Extent
Extends from the duodenojejunal flexure (angle of Treitz) to the ileocecal junction (cecum)
Intestinal Loop Groups
Left Group (Jejunum)
Occupies upper left abdominal space
Loops oriented transversely (horizontal)
Right Group (Ileum)
Occupies lower right abdominal space
Loops oriented vertically
Histological Structure (4 Layers: Outer → Inner)
Fixation & The Mesentery (Broad Fan-Shaped Double-Layered Peritoneal Fold)
Borders & Metrics
Root of the Mesentery (Radix Mesenterii):
Fixed posterior border
Length: ~15 cm long
Trajectory: Runs obliquely downward and to the right from the duodenojejunal flexure (
L2
) to the ileocecal junction (right iliac fossa)
Free Intestinal Border
Wraps around the 6 m length of the jejuno-ileal loops
Contents of the Mesentery