Layers of Bowel Wall

• Lumen (interior surface of colon "tube")
• Mucosa
• Lamina propria or basement membrane—dividing line between in situ and invasive lesions
• Muscularis mucosae
• Submucosa—lymphatics; potential for metastases increases
• Muscularis propria
• Circular layer
• Longitudinal layer—in three bands called taenia coli
• Subserosa—sometimes called pericolic fat or subserosal fat
• Serosa—present on ascending, transverse, sigmoid only (also called the visceral peritoneum)
• Retroperitoneal fat (also called pericolic fat)
• Mesenteric fat (also called pericolic fat)

http://training.seer.cancer.gov/images/colorectal/layers.jpg