Why is "Saying glucose and amino acids go into the lacteal, or fats go into the blood capillaries" a common mistake in Small Intestine: Structure & Adaptations?

Why it happens: Students remember a villus has two vessels but mix up which absorbs what. How to avoid it: Lock in the split: **glucose and amino acids → blood capillaries**; **fatty acids and glycerol (fats) → lacteal**. The lacteal is the FAT vessel. Source: Edexcel Biology examiner reports

Why is "Naming a feature without explaining its effect" a common mistake in Small Intestine: Structure & Adaptations?

Why it happens: Students list adaptations ('large surface area', 'thin wall') but forget questions ask them to EXPLAIN how each helps. How to avoid it: Always pair feature → effect: villi → large surface area → more/faster absorption; thin wall → short diffusion distance → faster diffusion. Source: Edexcel Biology examiner reports 2022–2024

Why is "Saying the blood supply 'carries food away' but not mentioning the concentration gradient" a common mistake in Small Intestine: Structure & Adaptations?

Why it happens: Students stop one step too early and miss the reason it matters. How to avoid it: Add the key link: carrying food away keeps the blood concentration low, which **maintains a steep concentration gradient**, keeping diffusion fast. Source: Edexcel Biology examiner reports

Why is "Confusing villi with microvilli, or treating them as the same thing" a common mistake in Small Intestine: Structure & Adaptations?

Why it happens: The words look almost identical. How to avoid it: **Villi** are the finger-like folds of the wall; **microvilli** are the much smaller folds on each villus cell's surface. Both increase surface area — mention both for top marks. Source: Edexcel Biology examiner reports

Why is "Confusing absorption with digestion" a common mistake in Small Intestine: Structure & Adaptations?

Why it happens: Both happen in the digestive system, so students blur the two stages. How to avoid it: Digestion = breaking food DOWN (by enzymes); absorption = taking the small soluble products INTO the blood. The villi are for absorption, not digestion. Source: Edexcel Biology examiner reports

Why is "Giving 'large surface area' as a structural feature of the villus" a common mistake in Small Intestine: Structure & Adaptations?

Why it happens: Students know surface area is important but state it as if it were a structure. How to avoid it: Large surface area is the RESULT of having villi and microvilli — name the actual structures (villi, microvilli) as the feature, then state the large surface area as the effect. Source: Edexcel Biology examiner reports

Edexcel IGCSE Science(Double Award)-Biology (4WSD0-1B)

Small Intestine: Structure & Adaptations

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Detailed Study Notes

Detailed notes on Structure and Functions in Living Organisms for Edexcel IGCSE Science(Double Award)-Biology, covering key concepts, explanations, examples, and exam-focused revision points.

Small Intestine: Structure & Adaptations — Edexcel International GCSE Science (Double Award) Biology (4WSD0-1B) Study Notes

How the small intestine (ileum) is adapted for the absorption of digested food. Covers villi and microvilli (huge surface area), the thin one-cell-thick wall, the rich blood supply that maintains a steep concentration gradient, and the lacteal for absorbing fats. Double Award Biology spec 2.32, assessed on Biology Paper 1 (4WSD0/1B).

At a glance

The small intestine (ileum) is where soluble digested food is absorbed into the blood.
Its inner wall is folded into millions of tiny finger-like villi (singular: villus).
Each villus cell surface is folded again into microvilli — together giving a huge surface area.
The villus wall is only one cell thick, giving a very short diffusion distance.
A dense capillary network carries absorbed glucose and amino acids away, maintaining the concentration gradient.
A lacteal (lymph vessel) in the centre absorbs the fatty acids and glycerol (fats).
More surface area + shorter distance + steeper gradient = faster absorption (all three boost diffusion).

What you’ll learn

Mapped to the Edexcel IGCSE 4SD0 syllabus (2026 onwards).

2.32 — Understand how the small intestine is adapted for absorption, including the structure of a villus.

What the small intestine does

By the ileum, food is fully digested — now it must be absorbed.

By the time food reaches the small intestine, the large food molecules have been broken down by enzymes into small, soluble molecules:

Carbohydrates → glucose (and other simple sugars)
Proteins → amino acids
Fats (lipids) → fatty acids and glycerol

The job of the ileum (the long, final part of the small intestine) is absorption — moving these small molecules out of the gut and into the blood (and, for fats, into the lymph). This mostly happens by diffusion (and active transport for some molecules), so the ileum is built to make diffusion as fast as possible.

Three things speed up diffusion, and the ileum is adapted for all three:

A large surface area,
A short diffusion distance (thin wall),
A steep concentration gradient (kept up by a good blood supply).

Exam tip. "Absorption" means moving digested food into the blood. Don't confuse it with digestion (breaking food down) — they are different stages.

Ileum = main site of absorption of digested food.
Glucose + amino acids → blood; fatty acids + glycerol → lacteal.
Adapted to speed up diffusion: big area, thin wall, steep gradient.

See the full worked example for small intestine: structure & adaptations →

Villi and microvilli: a huge surface area

Folds upon folds turn a smooth tube into a giant absorbing surface.

If the inside of the ileum were a smooth tube, very little food could be absorbed at once. Instead the wall is adapted to maximise surface area:

The inner lining is folded into millions of tiny finger-like projections called villi (singular: villus).
The surface of each villus cell is folded again into even smaller projections called microvilli (sometimes called the "brush border").

Together, villi and microvilli give the ileum an enormous surface area — far larger than a smooth tube would have. A larger surface area means more digested food can diffuse across at the same time, so absorption is much faster.

Why both? Villi increase the area a lot; microvilli increase it again on each cell. It's folds on top of folds.

Villi fold the wall into fingers; microvilli fold each cell's surface again — folds on folds for a massive surface area.

Villi = finger-like folds of the inner wall (millions of them).
Microvilli = tiny folds on each villus cell surface.
Both together = huge surface area → more diffusion at once.

See the full worked example for small intestine: structure & adaptations →

Thin wall and good blood supply

A one-cell-thick wall plus a rich capillary network speeds diffusion.

Two more adaptations make absorption fast:

1. Thin wall — short diffusion distance

The wall of a villus is only one cell thick (a single layer of cells).
This means digested food has only a very short distance to diffuse to reach the blood.
A shorter diffusion distance = faster diffusion.

2. Good blood supply — steep concentration gradient

Each villus contains a network of tiny blood vessels called capillaries.
Blood flowing through the capillaries constantly carries absorbed glucose and amino acids away from the villus.
This keeps the concentration of these molecules low in the blood and high in the gut, so there is always a steep concentration gradient.
A steep gradient keeps molecules diffusing in quickly — the gradient is maintained rather than running out.

Exam tip. Examiners love the phrase "maintains the concentration gradient". Always link the blood supply to carrying absorbed food away so the gradient stays steep.

Wall one cell thick → short diffusion distance → faster diffusion.
Capillary network carries glucose/amino acids away in the blood.
This maintains a steep concentration gradient for fast absorption.

See the full worked example for small intestine: structure & adaptations →

The lacteal: absorbing fats

A central lymph vessel takes up fatty acids and glycerol.

Not everything goes straight into the blood. In the centre of each villus there is a small lymph vessel called a lacteal.

The lacteal absorbs the products of fat digestion — the fatty acids and glycerol.
These fats are carried away in the lymph, not directly in the blood.
Meanwhile, glucose and amino acids are absorbed into the surrounding blood capillaries.

So a single villus does two transport jobs at once: capillaries take the water-soluble products (glucose, amino acids), and the lacteal takes the fats.

Putting a villus together — every feature has a purpose:

Many villi + microvilli → large surface area
One-cell-thick wall → short diffusion distance
Capillary network → carries glucose/amino acids away, maintaining the gradient
Lacteal → absorbs fatty acids and glycerol

A single villus: thin wall + microvilli (surface area & short distance), capillaries (glucose/amino acids, keep the gradient steep) and a central lacteal (fats).

Lacteal = central lymph vessel; absorbs fatty acids and glycerol (fats).
Capillaries absorb glucose and amino acids.
Each villus feature links to one reason absorption is fast.

See the full worked example for small intestine: structure & adaptations →

Quick recap

The ileum absorbs soluble digested food (glucose, amino acids, fatty acids + glycerol) into the body.
Villi and microvilli give a huge surface area, so more food diffuses across at once.
The villus wall is only one cell thick → short diffusion distance → faster diffusion.
Capillaries carry glucose and amino acids away, maintaining a steep concentration gradient.
A central lacteal absorbs the fatty acids and glycerol (fats) into the lymph.

Memorise this

Verbatim phrases and definitions Edexcel mark schemes credit.

Villi + microvilli = large surface area → more diffusion at once.
Wall one cell thick = short diffusion distance → faster diffusion.
Capillary network carries glucose/amino acids away = maintains the concentration gradient.
Lacteal absorbs fatty acids and glycerol (fats).
Absorbed: glucose + amino acids → blood capillaries; fats → lacteal (lymph).

How it’s examined

Assessed on Biology Paper 1 (4WSD0/1B), 2 hours, 110 marks, untiered (Double Award has no Biology Paper 2). Common shapes: label a villus diagram; 'describe how the small intestine / a villus is adapted for absorption' (3–4 marks); and 'explain how each adaptation speeds up absorption' (linking surface area, diffusion distance and concentration gradient). The marks come from naming the feature AND giving its effect (e.g. villi → large surface area → faster absorption).

Sources: Pearson Edexcel International GCSE Science (Double Award) 4SD0 specification — Issue 4, September 2024 (valid for 2026 onwards); Pearson Edexcel International GCSE Biology 4BI1 specification — Issue 4 (shared Biology Paper 1 content); Pearson Edexcel 4SD0 / 4BI1 examiner reports 2022–2024. Last reviewed 2026-06-04.

Take this whole topic with you

Step-by-step worked examples — Small Intestine: Structure & Adaptations

Step-by-step solutions to past-paper-style questions on small intestine: structure & adaptations, written exactly the way a tutor would explain them at the board.

Question type:

1What is absorbed and where it goes (Getting started)
Getting startedIdentify & classify• 4WSD0/1B style — short answer• absorption, spec-2.32
Question
The small intestine absorbs the products of digestion. State which two products are absorbed into the blood capillaries, and which products are absorbed into the lacteal. (3 marks)
Step-by-step solution
1. Step 1
  Into the blood (1 + 1). Glucose and amino acids are absorbed into the blood capillaries.
2. Step 2
  Into the lacteal (1). Fatty acids and glycerol (the products of fat digestion) are absorbed into the lacteal.
Answer
Blood capillaries: glucose and amino acids. Lacteal: fatty acids and glycerol.
Examiner tip
A very common opener. Remember the split: water-soluble products (glucose, amino acids) → blood; fats (fatty acids + glycerol) → lacteal.
2Why villi increase absorption (Getting started)
Getting startedIdentify & classify• 4WSD0/1B style — short answer• villi, surface-area, spec-2.32
Question
The inside wall of the small intestine is covered in villi. Explain how the villi help with absorption. (2 marks)
Step-by-step solution
1. Step 1
  Feature → effect (1). The villi (finger-like folds) give the wall a large surface area.
2. Step 2
  Why it matters (1). A larger surface area means more digested food can diffuse / be absorbed at the same time, so absorption is faster.
Answer
Villi give a large surface area, so more digested food can be absorbed (diffuse across) at once.
Examiner tip
Don't just write 'large surface area' — link it to the effect ('more absorption / faster diffusion') to secure the second mark.
3Thin wall and diffusion distance (Building confidence)
Building confidenceIdentify & classify• 4WSD0/1B style — structured• thin-wall, diffusion, spec-2.32
Question
The wall of a villus is only one cell thick. Explain how this feature helps the absorption of digested food. (3 marks)
Step-by-step solution
1. Step 1
  Feature (1). The wall being one cell thick gives a short diffusion distance (digested food has only a short way to travel).
2. Step 2
  Effect (1). A shorter distance means diffusion happens faster.
3. Step 3
  Outcome (1). So digested food is absorbed more quickly into the blood.
Answer
A one-cell-thick wall gives a short diffusion distance, so molecules diffuse across faster and digested food is absorbed more quickly.
Examiner tip
Use the precise phrase 'short diffusion distance', then 'faster diffusion'. 'The wall is thin so it works better' is too vague to score.
4How the blood supply keeps absorption going (Building confidence)
Building confidenceMulti-step problem• 4WSD0/1B style — structured• capillaries, concentration-gradient, spec-2.32
Question
Each villus has a network of blood capillaries. Explain how this good blood supply helps the absorption of glucose. (3 marks)
Step-by-step solution
1. Step 1
  Carries away (1). Blood flowing through the capillaries continuously carries absorbed glucose away from the villus.
2. Step 2
  Effect on gradient (1). This keeps the glucose concentration low in the blood and high in the gut, so a steep concentration gradient is maintained.
3. Step 3
  Outcome (1). The steep gradient keeps glucose diffusing into the blood quickly (so the gradient doesn't run out).
Answer
The capillaries carry absorbed glucose away, keeping its concentration low in the blood. This maintains a steep concentration gradient, so glucose keeps diffusing in quickly.
Examiner tip
The mark scheme wants the chain: carries food away → maintains the concentration gradient → keeps diffusion fast. Missing the middle link is the most common reason students drop a mark.
5Explain three adaptations of a villus (Stretch)
StretchMulti-step problem• 4WSD0/1B style — extended• villus, adaptations, spec-2.32
Question
Describe three ways a villus is adapted for the efficient absorption of digested food, and explain how each adaptation helps. (6 marks)
Step-by-step solution
1. Step 1
  Surface area (1 + 1). Villi and microvilli give a large surface area → more digested food can be absorbed at the same time.
2. Step 2
  Diffusion distance (1 + 1). The wall is one cell thick → a short diffusion distance → faster diffusion of food into the blood.
3. Step 3
  Concentration gradient (1 + 1). A capillary network carries absorbed glucose/amino acids away → maintains a steep concentration gradient → keeps absorption fast.
Answer
Villi + microvilli → large surface area → more absorption at once. 2) Wall one cell thick → short diffusion distance → faster diffusion. 3) Capillary network carries food away → maintains the concentration gradient → keeps absorption fast.
Examiner tip
Each adaptation earns a mark for the feature AND a mark for its effect. Always pair them: feature → effect. Adding microvilli alongside villi shows top-end knowledge.
6The role of the lacteal (Stretch)
StretchIdentify & classify• 4WSD0/1B style — extended• lacteal, fats, spec-2.32
Question
The diagram of a villus shows a central vessel called a lacteal as well as a network of blood capillaries. (a) State what is absorbed by the lacteal. (b) Explain why a villus needs both a lacteal and blood capillaries. (4 marks)
Step-by-step solution
1. Step 1
  (a) Lacteal (1). The lacteal absorbs the products of fat digestion — fatty acids and glycerol.
2. Step 2
  (b) Capillaries (1). The blood capillaries absorb glucose and amino acids (the water-soluble products).
3. Step 3
  Two routes (1). Different digested products are transported by different routes — fats by the lacteal (lymph), sugars and amino acids by the blood.
4. Step 4
  Efficiency (1). Having both means the villus can absorb all the products of digestion efficiently at the same time.
Answer
(a) Fatty acids and glycerol. (b) Capillaries take glucose and amino acids into the blood, while the lacteal takes fatty acids and glycerol into the lymph — two transport routes so all the digested products are absorbed.
Examiner tip
A frequent labelling/diagram question. The lacteal is for FATS only; glucose and amino acids go into the capillaries. Mixing these up is the classic error.

Model Answers — Small Intestine: Structure & Adaptations

High-scoring sample answers for small intestine: structure & adaptations on the Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) paper, with examiner-style notes mapping each response to the mark scheme and assessment objectives.

Question 1
4WSD0/1B style2 marks
Name two features of a villus that increase the surface area of the small intestine for absorption. (2 marks)
Model answer
Villi — the millions of finger-like folds/projections of the inner wall.

Microvilli — the tiny folds on the surface of each villus cell (the "brush border").

Together they greatly increase the surface area available for absorption.
Why this scores
1 mark each. 'Villi' and 'microvilli' are different things — both are credited. Don't give 'large surface area' as a feature; that is the effect, not the structure.
Question 2
4WSD0/1B style3 marks
State which products of digestion are absorbed into (a) the blood capillaries and (b) the lacteal of a villus. (3 marks)
Model answer
(a) Blood capillaries: glucose and amino acids (the water-soluble products of carbohydrate and protein digestion).

(b) Lacteal: fatty acids and glycerol (the products of fat/lipid digestion).
Why this scores
Glucose + amino acids into blood = 2 marks; fatty acids + glycerol into lacteal = 1 mark. Putting fats into the capillaries is a common slip.
Question 3
4WSD0/1B style5 marks
Describe how the small intestine is adapted for the absorption of digested food. (5 marks)
Model answer
The small intestine (ileum) is adapted in several ways:

Its inner wall is folded into millions of villi, and each villus cell has microvilli, giving a very large surface area so more food can be absorbed at once.

The wall of each villus is only one cell thick, giving a short diffusion distance so food diffuses across quickly.

Each villus has a network of blood capillaries that carry absorbed glucose and amino acids away, maintaining a steep concentration gradient for fast absorption.

Each villus also contains a lacteal, which absorbs the fatty acids and glycerol from fat digestion.

These adaptations together make absorption fast and efficient.
Why this scores
5 separate marking points available: villi/microvilli (surface area), thin wall (short distance), capillaries, maintains the gradient, lacteal for fats. List clearly so each point is easy to credit.
Question 4
4WSD0/1B style6 marks
Explain how the good blood supply to the villi helps to keep absorption rapid. (6 marks)
Model answer
Each villus contains a dense network of blood capillaries, so there is a good blood supply.

Glucose and amino acids are absorbed across the thin villus wall into these capillaries.

The flowing blood continuously carries the absorbed glucose and amino acids away from the villus.

This keeps their concentration low in the blood while it stays high in the gut (lumen).

So a steep concentration gradient is maintained between the gut and the blood.

Because the gradient stays steep, the food molecules keep diffusing into the blood quickly — the gradient does not run out, so absorption stays rapid.
Why this scores
The discriminating idea is 'maintains the concentration gradient'. Examiner reports note that weaker answers stop at 'carries food away' without explaining the effect on the gradient and on diffusion rate.
Question 5
4WSD0/1B style — extended open response7 marks
Using the structure of a villus, explain how its adaptations increase the rate of diffusion of digested food into the blood. (7 marks)
Model answer
Diffusion is faster when there is a larger surface area, a shorter diffusion distance and a steeper concentration gradient — and a villus is adapted for all three:

Large surface area: the wall is folded into many villi, and each villus cell has microvilli. This large surface area means more molecules can diffuse across at the same time, increasing the rate of absorption.

Short diffusion distance: the villus wall is only one cell thick, so digested food has only a very short distance to diffuse to reach the blood. The shorter the distance, the faster the diffusion.

Steep concentration gradient: each villus has a network of capillaries with a good blood supply. The blood carries absorbed glucose and amino acids away, keeping their concentration low in the blood. This maintains a steep concentration gradient between the gut and the blood, so molecules keep diffusing in rapidly.

In addition, the central lacteal absorbs fatty acids and glycerol, so the fat products are also removed efficiently. Together these adaptations maximise the rate of absorption.
Why this scores
Top answers explicitly link each structural feature to one of the three factors affecting diffusion (surface area, distance, gradient) and state the effect on rate. Marks: surface area + effect, thin wall + effect, capillaries + maintains gradient + effect, plus lacteal.
Question 6
4WSD0/1B style — extended open response8 marks
A student is shown a labelled diagram of a single villus. (a) Name the structure in the centre of the villus and the structure forming the network around it. (b) Explain how the features of this villus make it efficient at absorbing all the products of digestion. (8 marks)
Model answer
(a)

The structure in the centre of the villus is the lacteal (a lymph vessel).

The network around it is the blood capillaries.

(b) The villus is efficient because every feature has a purpose:

The outer surface is folded into microvilli and the wall is part of one of millions of villi, giving a large surface area so a lot of food is absorbed at once.

The wall is only one cell thick, giving a short diffusion distance so glucose and amino acids diffuse in quickly.

The blood capillaries absorb glucose and amino acids and continuously carry them away, maintaining a steep concentration gradient so absorption stays fast.

The central lacteal absorbs the fatty acids and glycerol (fat products) into the lymph.

Because there are two transport routes — capillaries for sugars and amino acids, and the lacteal for fats — the villus can absorb all the products of digestion efficiently at the same time.
Why this scores
(a) lacteal + capillaries = 2 marks. (b) up to 6 marks for surface area, short distance, capillaries maintaining the gradient, and the lacteal for fats — each linked to its effect. Putting fats into the lacteal (not the blood) is the key discriminator.

Key Definitions and Keywords — Small Intestine: Structure & Adaptations

Definitions to memorise and the exact keywords mark schemes credit for small intestine: structure & adaptations answers — sharpened from recent examiner reports for the 2026 Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) sitting.

Absorption
Examiner keyword
The movement of small, soluble digested food molecules out of the gut (small intestine) and into the blood or lymph, mainly by diffusion.
Ileum / small intestine
Examiner keyword
The long, final part of the small intestine where the absorption of digested food takes place. Its wall is covered in villi.
Villus (plural: villi)
Examiner keyword
One of the millions of tiny finger-like folds of the inner wall of the small intestine that greatly increase the surface area for absorption.
Microvilli
Examiner keyword
Tiny folds on the surface of each villus cell (the 'brush border') that increase the surface area even further for absorption.
Lacteal
Examiner keyword
The small lymph vessel in the centre of a villus that absorbs the products of fat digestion — fatty acids and glycerol.
Capillary network
Examiner keyword
The dense network of tiny blood vessels in a villus that absorbs glucose and amino acids and carries them away, maintaining the concentration gradient.
Diffusion distance
Examiner keyword
The distance a molecule must diffuse to cross a surface. The villus wall is only one cell thick, so the diffusion distance is short, making absorption fast.
Concentration gradient
Examiner keyword
The difference in concentration between two areas. A steep gradient (high in the gut, low in the blood) drives fast diffusion; the blood supply keeps it steep.

Common Mistakes and Misconceptions — Small Intestine: Structure & Adaptations

The traps other students keep falling into on small intestine: structure & adaptations questions — taken from recent Pearson Edexcel IGCSE Biology Paper 1 (4WSD0/1B) examiner reports and mark schemes — and how to avoid them.

✕Saying glucose and amino acids go into the lacteal, or fats go into the blood capillaries
Edexcel Biology examiner reports
Why it happens
Students remember a villus has two vessels but mix up which absorbs what.
How to avoid it
Lock in the split: glucose and amino acids → blood capillaries; fatty acids and glycerol (fats) → lacteal. The lacteal is the FAT vessel.
✕Naming a feature without explaining its effect
Edexcel Biology examiner reports 2022–2024
Why it happens
Students list adaptations ('large surface area', 'thin wall') but forget questions ask them to EXPLAIN how each helps.
How to avoid it
Always pair feature → effect: villi → large surface area → more/faster absorption; thin wall → short diffusion distance → faster diffusion.
✕Saying the blood supply 'carries food away' but not mentioning the concentration gradient
Edexcel Biology examiner reports
Why it happens
Students stop one step too early and miss the reason it matters.
How to avoid it
Add the key link: carrying food away keeps the blood concentration low, which maintains a steep concentration gradient, keeping diffusion fast.
✕Confusing villi with microvilli, or treating them as the same thing
Edexcel Biology examiner reports
Why it happens
The words look almost identical.
How to avoid it
Villi are the finger-like folds of the wall; microvilli are the much smaller folds on each villus cell's surface. Both increase surface area — mention both for top marks.
✕Confusing absorption with digestion
Edexcel Biology examiner reports
Why it happens
Both happen in the digestive system, so students blur the two stages.
How to avoid it
Digestion = breaking food DOWN (by enzymes); absorption = taking the small soluble products INTO the blood. The villi are for absorption, not digestion.
✕Giving 'large surface area' as a structural feature of the villus
Edexcel Biology examiner reports
Why it happens
Students know surface area is important but state it as if it were a structure.
How to avoid it
Large surface area is the RESULT of having villi and microvilli — name the actual structures (villi, microvilli) as the feature, then state the large surface area as the effect.

Small Intestine: Structure & Adaptations

Detailed Study Notes

At a glance

What you’ll learn

Quick recap

Memorise this

How it’s examined

Take this whole topic with you

1What is absorbed and where it goes (Getting started)

2Why villi increase absorption (Getting started)

3Thin wall and diffusion distance (Building confidence)

4How the blood supply keeps absorption going (Building confidence)

5Explain three adaptations of a villus (Stretch)

6The role of the lacteal (Stretch)

Absorption

Ileum / small intestine

Villus (plural: villi)

Microvilli

Lacteal

Capillary network

Diffusion distance

Concentration gradient

✕Saying glucose and amino acids go into the lacteal, or fats go into the blood capillaries

✕Naming a feature without explaining its effect

✕Saying the blood supply 'carries food away' but not mentioning the concentration gradient

✕Confusing villi with microvilli, or treating them as the same thing

✕Confusing absorption with digestion

✕Giving 'large surface area' as a structural feature of the villus