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BIO 304 . WEEK 7 . FRIDAY . LAB WORKBOOK
Digestion and Absorption
What breaks down where, and how nutrients cross into the blood.
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
Digestion happens stepwise: mechanical and chemical. Absorption is largely the job of the small intestine, whose villi enormously expand surface area. Today you'll draw a villus close-up, then the macronutrient digestion pathways.
Box A. Intestinal villus close-up
Directions
- Draw a single intestinal villus: a finger-like projection into the lumen.
- Label the lumen at the top.
- Show the villus surface lined by absorptive epithelial cells (enterocytes), each with microvilli (brush border) facing the lumen. Label both.
- Inside the villus, draw a network of blood capillaries (label) and one central lac#0B1530 (a lymphatic capillary running up the center). Label.
- Add a goblet cell (mucus-secreting) in the epithelium. Label.
- Note the principle: water-soluble nutrients (amino acids, monosaccharides) enter the blood capillaries; fat-soluble nutrients (chylomicrons, fatty acids in lipid form) enter the lac#0B1530s and travel via lymph.
Draw here. Sketch by hand.
Box B. Macronutrient digestion pathways
Directions
- Draw three parallel pathways: Carbohydrates, Proteins, Fats. Each pathway shows where digestion begins, where it continues, and what the final absorbed product is.
- Carbohydrates: starch (mouth, salivary amylase begins) > starch (stomach, no digestion) > maltose (small intestine, pancreatic amylase) > glucose (small intestine, brush-border enzymes like maltase). Absorbed: monosaccharides into blood.
- Proteins: protein (mouth, no digestion) > peptides (stomach, pepsin) > shorter peptides (small intestine, pancreatic proteases) > amino acids (small intestine, brush-border peptidases). Absorbed: amino acids into blood.
- Fats: triglycerides (mouth, no digestion) > triglycerides (stomach, minor lingual lipase) > emulsified fat droplets (small intestine, bile salts from gallbladder) > monoglycerides + fatty acids (small intestine, pancreatic lipase). Absorbed: re-formed triglycerides as chylomicrons into lac#0B1530.
- Label each enzyme, its source (which organ), and the products at each step.
Draw here. Sketch by hand.
1C. Structures to label (18)
After you finish each drawing, label every structure below directly on your sketch.
- Villus
- Microvilli (brush border)
- Enterocyte
- Goblet cell
- Lumen
- Blood capillary
- Lac#0B1530
- Salivary amylase
- Pepsin
- Pancreatic amylase
- Pancreatic protease (trypsin)
- Pancreatic lipase
- Brush-border enzymes
- Bile salts
- Glucose
- Amino acid
- Fatty acid + monoglyceride
- Chylomicron
Part 2 of 2
Physiology Lab
2A. Enzyme, source, substrate, product
Fill in the table to map each major digestive enzyme.
| Enzyme | Source organ | Substrate | Product |
|---|
| Salivary amylase | | | |
|---|
| Pepsin | | | |
|---|
| Pancreatic amylase | | | |
|---|
| Trypsin (and other pancreatic proteases) | | | |
|---|
| Pancreatic lipase | | | |
|---|
| Maltase (brush border) | | | |
|---|
| Lactase (brush border) | | | |
|---|
Lactose intolerance is caused by deficiency of the brush-border enzyme lactase. Predict the patient's symptoms after consuming dairy, and explain why undigested lactose causes osmotic diarrhea and bacterial gas production.
Bile salts are NOT enzymes, yet they are essential for fat digestion. Explain mechanistically how bile salts contribute to fat digestion without breaking any chemical bonds themselves (think: emulsification).
2B. Synthesis questions
Answer each in 2 to 4 sentences. Use the language from this week's lecture and your drawings as evidence.
1. Celiac disease is an autoimmune reaction to gluten that damages and flattens intestinal villi. Predict the consequences for nutrient absorption and the patient's symptoms (weight loss, anemia, fatigue, diarrhea).
2. A patient has their gallbladder removed (cholecystectomy). Predict the effect on fat digestion immediately after surgery and over the long term. Why can the patient still digest fats, just less efficiently?
3. Pancreatic insufficiency (e.g., from cystic fibrosis or chronic pancreatitis) leads to malabsorption of all three macronutrients, but fat malabsorption is most pronounced. Explain mechanistically why fat absorption is hit hardest.
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.