Outer layer of the alimentary canal; secretes a watery fluid to reduce friction?

Outer layer of the alimentary canal; secretes a watery fluid to reduce friction?

• A. Mucosa
• B. Serosa
• C. Submucosa
• D. Muscularis externa

Answer: (B)

The lubricating outer layer of the alimentary canal is the serosa. This layer is the visceral peritoneum, made up of a thin layer of mesothelial cells with connective tissue underneath, and it secretes serous fluid that provides a slippery film to reduce friction as the intestines move against each other and the surrounding walls. The mucosa is the inner lining that protects the lumen and handles secretion and absorption; the submucosa supports the mucosa and contains vessels and nerves; the muscularis externa supplies the smooth muscle for peristalsis. In parts outside the peritoneal cavity, an outer adventitia may be present instead of serosa, but the serosa specifically is the lubricating outer layer.

The lubricating outer layer of the alimentary canal is the serosa. This layer is the visceral peritoneum, made up of a thin layer of mesothelial cells with connective tissue underneath, and it secretes serous fluid that provides a slippery film to reduce friction as the intestines move against each other and the surrounding walls. The mucosa is the inner lining that protects the lumen and handles secretion and absorption; the submucosa supports the mucosa and contains vessels and nerves; the muscularis externa supplies the smooth muscle for peristalsis. In parts outside the peritoneal cavity, an outer adventitia may be present instead of serosa, but the serosa specifically is the lubricating outer layer.