BIOS256 W1 Lab Exercise

1233 words 5 pages

Mechanical Digestion in the Gastrointestinal Tract Directions:
a. Click the Contents button.
b. Open the Digestive System File.
c. Click Animations.
d. Click Mechanical Digestion in the Gastrointestinal Tract.


1. Define the gastrointestinal tract (GI). The gastrointestinal tract (GI) also known as the Alimentary Canal is one of the two groups of organs composed in the digestive system. It is defined as a continuous tube that extends from the mouth to the anus through the thoracic and abdominopelvic cavities. Organs of the GI tract includes the mouth, most of the pharynx, esophagus, stomach, small intestines, and large intestines.

2. Identify three mechanical digestion activities.

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a. Inhibits gastrin production, Decreases gastric motility and secretion b. Stimulates contraction of pyloric sphincter decreasing chyme release into duodenum c. Increases mucus production in duodenum

13. Determine if these motor impulses are sympathetic or parasympathetic. The neurons in the motor impulses are found to be in parasympathetic.

Segmentation and Migrating Motility Complexes

14. Describe segmentation and its effect. Mechanical digestion in the small intestine is a localized mixing contraction. Segmentations is a type of peristalsis used to mix chyme and bring it in contact with the mucosa for absorption. It begins in the lower portion of the stomach and pushes food forward along a small stretch of small intestine. It is governed by the myenteric plexus.

15. Describe migrating motility complexes. Are waves of activity that sweep through the intestines in a regular cycle during a fasting state.
Gastroileal Reflex

15. The ileocecal valve is normally closed. Explain the role of the gastroileal reflex. It causes relaxation of the ileocecal valve, intensifies peristalsis in the ileum, and forces any chyme into the cecum.
Haustral Churning

16. What ultimately stimulates closing of the ileocecal valve. It is the sphincter muscle that opens and closes allowing for digested materials to move from the small intestine to the large.

17. Describe houstral churning and its function. The haustra remain relaxed and become