4 digestion ppt lesson 4

Human Digestive System

OBJECTIVESYou 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.

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

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

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.

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 PortalVein

Transport and utilization of Fats

Fats is transported from the Lacteal Lymphatic vessels Bloodstream Rest of the body and Liver

Lacteal

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

Assimilation The distribution and use of the digested food productsas an energy source or converted into protoplasm required for growth and repair of worn-out parts - Assimilation

Small intestine

Let’s reviewYou 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.

What processes take place in the same part of the alimentary canal where ingestion of

food takes place?

1. Physical digestion only2. Chemical digestion only3. Physical and chemical digestion4. Digestion and absorption

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 only2. I and II only3. II and IV only4. II only

Complete the following equations

Starch _____________

Protein ______________

Fats _______________

amylase

proteases

lipase

Maltose

Amino acids

Fatty acids + glycerol

Why are bile salts not considered enzymes?

Bile salts does not digest fats, it only emulsify fats – Increase surface area for digestion by lipase.

TRUE / FALSE

Fat digestion will stop if the bile duct is blocked by gallstones.

False . Fat digestion will not stopBut will become very slow

since bile is absent to emulsify fats

At which part of the digestive system is digestion of all food completed.

1. Stomach

2. Colon

3. Oesophagus

4. Ileum

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.

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

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

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food

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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.