Human A&PBIO 304 · American River College ← Week 07 pre-work

BIO 304 · Week 07 · Interactive Workbook

GI Tract Anatomy & Motility

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Part 1 of 4 · Recall

Fill in the blanks

Type the term that completes each statement, using the word bank. Pull it from memory first.

Word bank

Plicae circularesInternal analMasticationMain jobSubmucosaAscending colonEsophagusSigmoid colonLower esophageal (cardiac)PeristalsisModulated by ANSGallbladderSubmucosal plexusDuodenumMouth

  1. mechanical (teeth) and chemical (salivary amylase) digestion; starts swallow
  2. muscular tube; peristalsis to stomach; upper and lower esophageal sphincters
  3. ~25 cm; receives bile and pancreatic juice; most chemical digestion
  4. circular folds increase surface area
  5. right side, up
  6. S-curve into pelvis
  7. water and electrolyte absorption; vitamin K from gut flora; storage of feces
  8. stores and concentrates bile; releases on CCK signal
  9. dense CT with blood vessels, lymphatics, submucosal (Meissner) plexus
  10. controls secretion and local blood flow
  11. parasympathetic stimulates; sympathetic inhibits
  12. prevents reflux; failure = GERD
  13. smooth muscle; involuntary
  14. propulsive wave; pushes contents forward
  15. voluntary; mechanical breakdown

Define it: high-yield vocabulary

Write a clear definition in your own words for each term.

  1. Mucosa
  2. Submucosa
  3. Muscularis externa
  4. Serosa
  5. Peristalsis
  6. Segmentation
  7. Sphincter
  8. Enteric nervous system
  9. Plicae circulares
  10. Villi
  11. Microvilli
  12. Deglutition

Part 2 of 4 · Anatomy lab

Draw and label

Box A. GI tract with accessory organs

Directions

  1. Draw a body outline (head and torso).
  2. 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.
  3. 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.
  4. Show ducts: bile duct from liver and gallbladder, pancreatic duct from pancreas, both emptying into the duodenum.
  5. Label every structure.
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Box B. GI wall layers (cross-section)

Directions

  1. Draw a cross-section of a typical GI tube (e.g., small intestine). Show the lumen in the center.
  2. From the lumen outward, label four layers:
  3. Mucosa (innermost): epithelium + lamina propria + muscularis mucosae. This is the absorptive surface; in the small intestine, show villi projecting into the lumen.
  4. Submucosa: connective tissue with blood vessels and the submucosal nerve plexus. Label.
  5. 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.
  6. Serosa (outermost): thin layer of mesothelium and connective tissue (the visceral peritoneum). Label.
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Structures to label

Label each on your drawing.

  1. Oral cavity
  2. Pharynx
  3. Esophagus
  4. Stomach
  5. Duodenum
  6. Jejunum
  7. Ileum
  8. Cecum
  9. Appendix
  10. Ascending colon
  11. Transverse colon
  12. Descending colon
  13. Sigmoid colon
  14. Rectum
  15. Anus
  16. Salivary glands
  17. Liver
  18. Gallbladder
  19. Pancreas
  20. Bile duct
  21. Pancreatic duct
  22. Mucosa
  23. Submucosa
  24. Muscularis externa
  25. Serosa
  26. Circular muscle layer
  27. Longitudinal muscle layer

Part 3 of 4 · Physiology lab

Reason it through

A. Peristalsis vs segmentation

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.

B. Synthesis

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.

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