The document discusses the process of assimilation and transport of digested food throughout the body. It defines assimilation as the distribution and use of digested food as an energy source or to build new cells. It describes how sugars, amino acids, and fats are transported via the hepatic portal vein to the liver and then throughout the body. It specifically explains that glucose is used by cells for energy, excess is stored as glycogen in the liver, and insulin stimulates the conversion of glucose to glycogen.

2. OBJECTIVES
You will learn:
• 1) Define assimilation as the process where the products
of digestion are distributed and use as an energy source or
converted into protoplasm required for growth and repair
of worn-out parts.
• 2) State the role of the hepatic portal vein in transporting
sugars and amino acids to the liver.
• 3) Explain how sugars, amino acids and fats are utilised in
the body.
• 4) State that the hormone insulin is produced by islets of
Langerhans in the pancreas.
• 5) Explain the effect of insulin on glucose.

3. Transport of food substances
Hepatic
Portal vein
Small intestine
Liver
Blood capillaries
Gall
bladder
Bile
Duct
Absorbed food
substances (sugars
and amino acids) are
transported via the
hepatic portal vein to
the liver
Note: Fats are
transported through the
lacteal into the lymphatic
system

4. Transport and utilization of
Glucose
Small
intestine
Function of glucose:
Glucose is used by all
cells as a source of
energy.
Hepatic vein
Some glucose is transported by the
blood leaving the liver to other parts
of the body
Excess glucose is
converted to glycogen
and stored in the liver.
Hepatic portal vein
Glycogen

5. Conversion of Glucose
Islets of Langerhan
cells in the pancreas –
secretes a hormone
Insulin
Insulin stimulate the
liver to convert excess
glucose to glycogen
and stored.

6. Transport and utilization of
Amino acids
Amino acids pass through
the liver before they are
transported to the rest of
the body.
Small
intestine
Hepatic vein
Function of amino acids:
• Make new cells for growth
• Replace worn-out cells
• Make useful substances
such as enzymes and
hormones
Excess amino
acids are
deaminated.
Hepatic
Portal
Vein

7. Transport and utilization of
Fats
Fats is transported from
the Lacteal  Lymphatic
vessels  Bloodstream
 Rest of the body and
Liver
Lacteal

8. Transport and utilization of
Fats
Fate of Fats
• Use to form parts
of the cell such
as cell membrane
• Prevent excessive
heat loss.
Excess fats stored in
adipose tissues
When glucose supply is low,
fats are broken down in the
liver to provide energy

9. Assimilation
The distribution and use of
the digested food products
as an energy source or
converted into protoplasm
required for growth and
repair of worn-out parts -
Assimilation
Small
intestine

10. Let’s review
You have learnt:
• 1) Define assimilation as the process where the products
of digestion are distributed and use as an energy source or
converted into protoplasm required for growth and repair
of worn-out parts.
• 2) State the role of the hepatic portal vein in transporting
sugars and amino acids to the liver.
• 3) Explain how sugars, amino acids and fats are utilised in
the body.
• 4) State that the hormone insulin is produced by islets of
Langerhans in the pancreas.
• 5) Explain the effect of insulin on glucose.

12. What processes take place in the same part of the
alimentary canal where ingestion of food takes
place?
1. Physical digestion only
2. Chemical digestion only
3. Physical and chemical digestion
4. Digestion and absorption

13. Which of the following statement(s) about the
Oesophagus is/are true?
I. There is no digestion occuring in the oesophagus
II. Food moves down the oesophagus via peristalsis
III. There is digestion of starch in the oesophagus
IV. The wall of the oesophagus secrete digestive
enzymes
1. II and III only
2. I and II only
3. II and IV only
4. II only

14. Complete the following equations
Starch _____________
Protein ______________
Fats _______________
amylase
proteases
lipase
Maltose
Amino acids
Fatty acids + glycerol

15. Why are bile salts not considered
enzymes?
Bile salts does not digest fats,
it only emulsify fats – Increase
surface area for digestion by
lipase.

16. TRUE / FALSE
Fat digestion will stop if the bile duct is
blocked by gallstones.
False .
Fat digestion will not stop
But will become very slow since
bile is absent to emulsify fats

17. At which part of the digestive system is
digestion of all food completed.
1. Stomach
2. Colon
3. Oesophagus
4. Ileum

18. Which of the following listed below is not a
feature of the ileum?
1. The inner surface is folded.
2. It releases gastric juice.
3. It is a very long tube.
4. Its main function is the absorption of
digested food.

19. The diagram below shows part of the human digestive
system and the associated blood vessels.
Blood vessel X would least likely contain _____________
1. Glycerol 2. Amino acids 3. Water 4. Glucose
X

20. The diagram below shows the percentage of proteins,
carbohydrates and fats digested as they pass through the
alimentary canal in man.
Which is PART C likely to be?
1. Ileum 2. Duodenum 3. Stomach 4. Oesophagus
Percentageofundigested
foodmolecules

21. How would the composition of the blood in the
hepatic vein change if there was a high intake
of protein-rich food? Explain.
The composition of the blood
would not change since excess
amino acids caused by the high
intake of protein-rich food will
be deaminated in the liver.