• 17 steps
  • Checked October 2026

Carbohydrate Digestion Diagram

Follow starch and sugar from the mouth to the blood, one enzyme at a time.

Carbohydrate Digestion Diagram

Name Date

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17
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Write the name of each numbered step.Answer key

  1. Salivary amylase
  2. Stomach acid
  3. Pancreatic amylase
  4. Brush border enzymes
  5. Hepatic portal vein
  6. Liver
  7. Gut bacteria
  8. Maltose
  9. Sucrose
  10. Lactose
  11. Maltase
  12. Sucrase
  13. Lactase
  14. Glucose
  15. Fructose
  16. Galactose
  17. Blood capillary

Drawn for this site on 2026-10-03 from plain geometry. Licence: own work.

Each numbered ring is a button. Use the arrow keys to move between them and Enter to choose. Names are read out in Study, and once a step is answered.

Next step Next: how fat is absorbed, step by step

All 17 steps on the diagram

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Down the tract 7

  1. Salivary amylase Starts splitting starch in the mouth. It is an enzyme in saliva.
  2. Stomach acid Switches salivary amylase off as the food turns acid. No enzyme made here splits carbohydrate.
  3. Pancreatic amylase Made by the pancreas. It splits starch in the small intestine.
  4. Brush border enzymes Finish the job on the lining of the small intestine. Sugars are absorbed here too.
  5. Hepatic portal vein Carries absorbed sugars from the intestine to the liver.
  6. Liver Receives the absorbed sugars first. It stores them or passes them on.
  7. Gut bacteria Ferment fiber, which no enzyme of the body can split.

At the brush border 10

  1. Maltose Two glucose units joined. Amylase leaves it when it cuts starch.
  2. Sucrose Glucose joined to fructose.
  3. Lactose Glucose joined to galactose. It is the sugar of milk.
  4. Maltase Splits maltose into two glucose.
  5. Sucrase Splits sucrose into glucose and fructose.
  6. Lactase Splits lactose into glucose and galactose.
  7. Glucose A single sugar. All three enzymes set it free.
  8. Fructose A single sugar, set free from sucrose.
  9. Galactose A single sugar, set free from lactose.
  10. Blood capillary Takes up the single sugars and carries them away.

How this list was compiled: Every name and every step checked on 2026-10-03 in at least two of these. (1) National Institute of Diabetes and Digestive and Kidney Diseases, Your Digestive System and How It Works, https://www.niddk.nih.gov/health-information/digestive-diseases/digestive-system-how-it-works : saliva has an enzyme that begins to break down starches; the pancreas makes a juice with enzymes that break down carbohydrates; the small intestine completes the breakdown and absorbs the nutrients into the bloodstream; blood carries simple sugars to the liver; bacteria in the large intestine help break down what remains. (2) A university physiology textbook online, Absorption of Monosaccharides, Small Intestinal Brush Border Enzymes, Dietary Polysaccharides and Microbial Fermentation, https://vivo.colostate.edu/hbooks/pathphys/digestion/smallgut/absorb_sugars.html : amylase from saliva and the pancreas cuts starch to maltose; maltase gives two glucose, lactase glucose and galactose, sucrase glucose and fructose, on the brush border; the single sugars pass into blood; bacteria of the large intestine ferment fiber. (3) Wikipedia, text only: Digestion, Alpha-amylase, Disaccharidase, Intestinal villus and Hepatic portal system, https://en.wikipedia.org/wiki/Digestion . (4) Fried, Abramson and Meyer, Passage of salivary amylase through the stomach in humans, 1987, abstract, https://pubmed.ncbi.nlm.nih.gov/3652896/ : amylase is inactivated in gastric juice as it turns more acid, and part of it still passes through. Licence: own work

The drawing: Drawn for this site on 2026-10-03 from plain geometry; nothing traced. Licence: own work

How it works

This carbohydrate digestion diagram has two views. The first follows carbohydrate down the digestive tract. The second enlarges the brush border, where three enzymes split the double sugars and the single sugars pass into the blood.

Read the full guide

Down the tract

Salivary amylase starts to cut starch in the mouth. Stomach acid then switches it off. In the small intestine pancreatic amylase cuts the rest of the starch down to maltose and other short chains. Fiber is not split by any enzyme of the body; bacteria in the large intestine ferment part of it.

At the brush border

Maltase, sucrase and lactase sit on the microvilli of the absorptive cells. Each splits one double sugar into single sugars: glucose, fructose and galactose. These cross the cell into a blood capillary, and the hepatic portal vein carries them to the liver.

  • Enzyme names end in -ase, sugar names in -ose: lactase splits lactose.
  • The quiz accepts the organ too: pancreas counts for pancreatic amylase.

Questions and answers

Where does carbohydrate digestion begin?

In the mouth. Saliva holds salivary amylase, an enzyme that starts to cut starch into shorter chains while food is chewed.

Which enzymes digest carbohydrates?

Salivary amylase and pancreatic amylase cut starch into maltose and other short chains. On the brush border of the small intestine, maltase, sucrase and lactase split the double sugars into single sugars.

Where are carbohydrates absorbed?

In the small intestine. Glucose, fructose and galactose cross the absorptive cells into the blood capillaries of the villi, and the hepatic portal vein carries them to the liver.

How do I label each part of anatomy involved in dietary carbohydrate digestion and absorption?

Work down the tract: salivary glands and mouth, stomach, pancreas, small intestine, hepatic portal vein, liver, large intestine. Each ring here names what happens at that place. The drawing is this site's own, not a figure from any course.

What happens to fiber during digestion?

No enzyme made by the body can split it, so it passes through the small intestine. Bacteria in the large intestine ferment part of it.

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