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Colonic Segments (Subdivisions & Landmarks), Terminal mobile colonic…
Colonic Segments (Subdivisions & Landmarks)
Ceco-Appendiceal Segment (Cecum & Appendix)
Cecum
Position
Normally mobile in the right iliac fossa (can be subhepatic, suprailiac, or pelvic)
Morphology
4 surfaces (anterior, posterior, medial, lateral)
+ 3 teniae coli converging at the appendiceal base
Dimensions
Height: 8–10 cm
Width: 6–8 cm
Internal Orifices
Ileocecal Orifice
Guarded by the Ileocecal Valve (Valve of Bauhin)
Appendiceal Orifice
Located ~2 cm below the ileocecal valve
Vermiform Appendix
Dimensions
Length: 7–8 cm
Diameter: 4–6 mm
Nature
Tubular lymphoid organ arising 2 cm below the ileocecal valve
Clinical Surface Landmark: McBurney’s Point
Located midway along the line connecting the Right Anterior Superior Iliac Spine (ASIS) to the Umbilicus
Projects the exact site of the appendiceal orifice onto the abdominal wall
Ascending Colon & Colic Flexures
Ascending Colon (Fixed Right Lumbar)
Length: 8–15 cm
Fixed in right lumbar fossa
Extends from cecum to hepatic flexure
Left Colic Flexure (Splenic Flexure)
Fixed, deep high in left hypochondrium
Acute angle opening inferiorly & anteriorly
Right Colic Flexure (Hepatic Flexure)
Fixed; lies anterior to right kidney
Acute angle opening inferiorly
Transverse, Descending & Iliopelvic Colon
Descending & Iliac Colon
Descending Colon
Fixed
Deeply situated in left lumbar fossa (~12 cm long)
Tapers downward to 4–5 cm
Iliac Colon
Located in left iliac fossa (~10–15 cm long)
Transitions from 3 to 2 teniae coli
Progressive loss of haustra
& marked increase in epiploic appendages
Pelvic / Sigmoid Colon
Transverse Colon
Mobile, ~50 cm long
Spans across the abdomen between right and left hypochondria
Its mesentery crosses transversely
Dividing the peritoneal cavity into supramesocolic and inframesocolic compartments
Terminal mobile colonic loop (~40 cm long)
Suspended by its mesentery (sigmoid mesocolon)
Lies within the pelvic cavity
Terminates at the rectosigmoid junction
Dimensions: Small caliber (3–4 cm)