Internal Gastrointestinal Tract of the Dogfish Shark


1. Papillae of esophagus
2. Rugae of Stomach
3. Stomach
4. Vulvular Intestines
5. Position of Anus
6. Rectum
7. Spiral Valve
    Papillae line the lumen of the esophagus, and rugae line the lumen of the stomach. The rugae allow the stomach to expand, thus permitting the shark to overfeed. The rugae in this shark are not easily seen because the shark had just recently eaten. Spiral valves are readily apparent in the lumen of the intestines. Their purpose is to increase surface area.