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BIO 304 . WEEK 7 . FRIDAY . LAB WORKBOOK
GI Tract Anatomy and Motility
Mouth to anus, plus the accessory organs that empty into the tract.
Print this page. You will draw your own diagrams from the directions below, then hand-label the structures listed. Drawing by hand is the integrity mechanism for this course.
1A. What you will draw
The GI tract is a tube from mouth to anus. Food and chyme move through it by two main mechanisms: peristalsis (propulsion) and segmentation (mixing). Today you'll draw the GI tract with accessory organs, then the wall layers common to most segments.
Box A. GI tract with accessory organs
Directions
- Draw a body outline (head and torso).
- Label, in order, the tube of the GI tract: mouth (oral cavity), pharynx, esophagus, stomach (J-shaped, in the upper left abdomen), small intestine (long coiled tube with 3 parts: duodenum, jejunum, ileum), large intestine (frames around the small intestine: cecum/appendix, ascending colon, transverse colon, descending colon, sigmoid colon, rectum), anus.
- Now add accessory organs (they don't carry food but contribute to digestion): salivary glands near the mouth, liver in the upper right abdomen, gallbladder under the liver, pancreas behind the stomach.
- Show ducts: bile duct from liver and gallbladder, pancreatic duct from pancreas, both emptying into the duodenum.
- Label every structure.
Draw here. Sketch by hand.
Box B. GI wall layers (cross-section)
Directions
- Draw a cross-section of a typical GI tube (e.g., small intestine). Show the lumen in the center.
- From the lumen outward, label four layers:
- Mucosa (innermost): epithelium + lamina propria + muscularis mucosae. This is the absorptive surface; in the small intestine, show villi projecting into the lumen.
- Submucosa: connective tissue with blood vessels and the submucosal nerve plexus. Label.
- Muscularis externa: usually two layers of smooth muscle, an inner circular and an outer longitudinal. Between them runs the myenteric nerve plexus. These layers produce peristalsis and segmentation. Label.
- Serosa (outermost): thin layer of mesothelium and connective tissue (the visceral peritoneum). Label.
Draw here. Sketch by hand.
1C. Structures to label (27)
After you finish each drawing, label every structure below directly on your sketch.
- Oral cavity
- Pharynx
- Esophagus
- Stomach
- Duodenum
- Jejunum
- Ileum
- Cecum
- Appendix
- Ascending colon
- Transverse colon
- Descending colon
- Sigmoid colon
- Rectum
- Anus
- Salivary glands
- Liver
- Gallbladder
- Pancreas
- Bile duct
- Pancreatic duct
- Mucosa
- Submucosa
- Muscularis externa
- Serosa
- Circular muscle layer
- Longitudinal muscle layer
Part 2 of 2
Physiology Lab
2A. Peristalsis vs segmentation
Compare the two main GI motility patterns by filling in the table. Then answer the follow-up questions.
| Property | Peristalsis | Segmentation |
|---|
| Primary function (propulsion / mixing) | | |
|---|
| Direction of movement | | |
|---|
| Where dominant in GI tract | | |
|---|
| Muscle layers involved | | |
|---|
| Wave pattern | | |
|---|
Trace a bite of food from the moment it enters the mouth to the moment chyme leaves the stomach. Identify which motility patterns dominate at each step and approximately how long each stage takes.
Defecation is a complex motor act involving both involuntary smooth muscle (internal anal sphincter) and voluntary skeletal muscle (external anal sphincter). Explain why a patient with a high spinal cord injury loses voluntary control but may still defecate reflexively.
2B. Synthesis questions
Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.
1. Dysphagia (difficulty swallowing) can result from problems with the pharynx, the esophagus, or the lower esophageal sphincter. Predict the symptoms in each case, and which patient population is most affected by each.
2. Gastroparesis (delayed gastric emptying) is a common complication of diabetes. Predict the patient's symptoms after a meal and explain why dampened autonomic input to the stomach reduces its motility.
3. Irritable bowel syndrome (IBS) is characterized by altered motility, often producing either diarrhea (too fast) or constipation (too slow). Predict what changes in segmentation and peristalsis would produce each pattern.
3. What to submit
Complete both the Anatomy Lab (your own drawings, hand-labeled, plus the structures list) and the Physiology Lab (activity and synthesis questions). Photograph or scan every page and upload to Canvas before the deadline listed on the schedule. Hand-drawn, hand-labeled work is the integrity mechanism for this course. Typed or AI-generated diagrams are not accepted.