Describe the structure of a villus
Locate the epithelium, capillaries and lacteal.
Section B7.5 · Absorption
Cross-referenced to the 2028–2029 0653 section using original teaching from the related single-science courses. A 0653-specific objective-by-objective and Core/Supplement review is in progress. Written practice is self-checked and does not demonstrate supervised laboratory competence or award an official Cambridge grade.
Before you begin
- Recall large and small nutrient molecules, cell membranes and enzyme specificity.
- Use the stated diagram keys and evidence; models are not to scale.
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
Which structure forms the villus surface barrier?
What you will learn
- Locate the epithelium, capillaries and lacteal.
- Explain the short-distance adaptation without inventing an open food-to-blood hole.
A thin boundary around transport structures
A villus has a thin epithelial layer at the surface, with microvilli on the lumen-facing cell membranes. Inside it lie blood capillaries and a lymphatic vessel called a lacteal. The vessels are beneath the surface, not open tubes filled directly with food.
The thin surface provides a short distance for absorbed products to reach underlying transport structures. Do not label the villus as a hole through which intact food simply falls into the bloodstream.
Read a sectional model
The teaching diagram shows an outer epithelial outline, a capillary network and a central lacteal. Their positions help identify them; blood and lymph colours are schematic rather than natural universal identification codes.
A section is a simplified slice through a three-dimensional projection. It omits many cells and details, but retains the required relationships. Arrow directions represent the stated transport model rather than a visible measurement in the still image.
Sources for this lesson
Pause and explain
What is a lacteal?
Worked example
A section shows an outer cell layer, a branching vessel network and a central lymph vessel. Identify the three structures.
Show the worked solution
- Outer layer: epithelium.
- Network: blood capillaries.
- Central lymph vessel: lacteal.
Answer Epithelium, blood capillaries and lacteal.
Try a topic test
Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.
Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Name the outer layer and two internal transport structures of a villus.
Give me a hint
Use epithelium, capillaries and lacteal.
Compare my reasoning
- Surface: epithelium.
- Inside: blood capillaries and lacteal.
Epithelium outside; capillaries and lacteal inside.
Look for these in your work
- All three.
- Correct positions.
Why does the thin epithelium support absorption?
Give me a hint
Consider the distance across the boundary.
Compare my reasoning
- Products cross a short distance.
- Underlying vessels are close.
It provides a short transport distance from lumen-facing surface to underlying transport structures.
Look for these in your work
- Distance link.
- No direct-food-hole claim.
A model draws intact bread falling through a hole straight into a capillary. Correct the structures and mechanism.
Give me a hint
Digestion and crossing a lining are needed.
Compare my reasoning
- A continuous epithelial boundary separates lumen and vessels.
- Small digestion products cross it.
- Intact bread does not fall directly into blood.
Show a lining with small absorbed products reaching underlying vessels, rather than an open hole carrying intact food.
Look for these in your work
- Boundary retained.
- Correct material scale.
Common mistakes
- Vessels are beneath the lining rather than open to food.
- Diagram colours are a key, not a universal tissue colour.
What can you explain now?
What is a lacteal?
Compare with the explanation
A lymphatic vessel in a villus.
It has a transport role.
After trying it yourself, choose your next review. This is your self-assessment.
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Make it stick
Describe a villus from the gut lumen inward to its transport structures.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.