Absorption

20/4/09

Prepared by Miss Izzati Apr 09

Previously…

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GROUP ACTIVITYYou are provided with:1. Organs Cards (O)2. Physical Digestion Cards (P)3. Chemical Digestion Cards (C)4. Mahjong Paper with body outline.5. Markers (to draw arrows).

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Instructions1. Label all the organs in the digestive system. Use all

the Organs (O) cards .2. Label all the physical digestion processes that you

have learnt. Stick the Physical Digestion (P) cards near the correct body part where the process occurs.

3. Label all the chemical digestion processes that you have learnt. Stick the Chemical Digestion (C) cards near the correct body part where the process occurs.

4. Fastest group wins!

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Example

(O) oesophagus

(P) chewing Starch maltoseamylase

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INGESTION

DIGESTION

ABSORPTION

EGESTION

ASSIMILATION

Food is taken into body

Carbohydrates, proteins and fats are broken down into soluble glucose,

amino acids, fatty acids and glycerol.

Glucose, amino acids, fattyacids and glycerol are absorbed

into body cells

Removal of undigested food e.g. dietary fibre

Absorbed nutrients are transported and utilized by the body

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ABSORPTIONMonosaccharides (glucose, fructose and galactose), amino acids, fatty acids, glycerol and water are absorbed in the small intestine.

The absorbed nutrients passesfrom the lumen of the small intestine into the bloodstream.

http://www.colorado.edu/intphys/Class/IPHY3430-200/image/villi.jpg

lumen

How to ensure that nutrients are quickly absorbed?

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Adaptations of the Small Intestine

1. Large surface area: volume ratio1.1 The inner walls of the small intestine have

numerous folds

http://www.path.cam.ac.uk/Normal/AR_Alimentary/SI_Small_intestine/N_AR_SI_08small.jpg

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Adaptations of the Small Intestine

1. Large surface area: volume ratio1.2 Folded inner walls are lined with

numerous minute finger-like projections called villi

http://www.technion.ac.il/~mdcourse/274203/slides/Digestive%20tract/17-Intestinal%20villi%20Jejunum-A.jpg

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1. Large surface area: volume ratio1.3 The epithelial cells of the villi have

numerous microvilli.

Adaptations of the Small Intestine

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Adaptations of the Small Intestine

http://www.siumed.edu/~dking2/erg/images/GI020b.jpg

2. The villi wall (epithelial cell layer) is only one cell thick.

http://www.biog1105-1106.org/demos/105/unit6/media/villus.structure.jpg

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Adaptations of the Small Intestine

3. Presence of numerous capillaries to carry away the absorbed nutrients.

blood capillaries

Lacteal/lymphatic capillary

Digested food enters villuslumen

epithelial cell layer

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Adaptations of the Small Intestine

Blood capillaries: transport monosaccharides and amino acids.

Lymphatic capillaries (lacteals): transport fats

The continual removal of nutrients maintains a concentration gradient for diffusion.

liver

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Adaptations of the Small Intestine

4. Small intestine is long to provide sufficient time for absorption.

http://blog.lib.umn.edu/trite001/pstl1082anatomy/SmallIntestine.jpg

The small intestine is about 6m long!

How are the nutrients absorbed?

Recall what you have learnt in the topic Movement of Substances!

(Diffusion, osmosis, active transport….)

glucose

amino acids

Fatty Acids

glycerol

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What type of movement occurs through the epithelium in these situations?

• High concentration of glucose and amino acids in the lumen of the small intestine.

• Low concentration of glucose and amino acids in the lumen of the small intestine.

• High concentration of fatty acids and glycerol in the lumen of the small intestine

• High water potential in the lumen of the small intestine.• High concentration of minerals salts in the lumen of the

small intestine.

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How does absorption take place in the villi?

Soluble substance Type of movement into the epithelium

Note:

Monosaccharides(e.g: glucose)

DiffusionActive Transport

High conc. in lumenlow conc. in lumen

Amino Acids DiffusionActive transport

High conc. In lumenlow conc. In lumen

Fatty acids and glycerol Diffusion Glycerol and fatty combine to form small fat droplets that enter the lacteals.

Water Osmosis Enter the blood capillaries

Mineral Salts Diffusion Enter the blood capillaries

Water soluble vitamins (B and C)

Diffusion Enter the blood capillaries

Fat –Soluble Vitamins (A, D, E and K)

Diffusion Enter the lacteals

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SUMMARYAdaptations of the small intestine:

1. Large SA: Vol. folds, villi and microvilli.

2. Villi epithelial wall is one cell thick rapid diffusion.

3. Blood capillaries and lacteals maintain concentration gradient.

4. Long allows sufficient time for absorption

Movement into villi:

• Glucose and amino acids absorbed by diffusion or active transport into blood capillaries of the villi.

• Glycerol and fatty acids diffuse into the epithelium combine to form minute fat globules which enter lacteals.

• Water and mineral salts are also absorbed by the small intestine.

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Egestion•In the colon, water and mineral salts are absorbed from the undigested food material.

•Bacterial Activity

•Presence of dietary fibre/roughage helps in peristalsis.

•Unabsorbed matter is stored temporarily in the rectum.

•Faeces is discharged through the anus.

colon

rectumanus

http://z.about.com/d/coloncancer/1/0/1/3/LargeIntestine.300x300.jpg

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INGESTION

DIGESTION

ABSORPTION

EGESTION

ASSIMILATION

Food is taken into body

Carbohydrates, proteins and fats are broken down into soluble glucose,

amino acids, fatty acids and glycerol.

Glucose, amino acids, fattyacids and glycerol are absorbed

into body cells

Removal of undigested matter e.g. dietary fibre

Absorbed nutrients are transported and utilized by the body

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QUICK CHECK1. Which one of the following features of the small

intestine does not help in its function of absorption?

a) The constant production of mucusb) The folding of its inner surfacec) One cell thick villi walld) Presence of villi and microvilli.

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QUICK CHECK2. Which of the following statements correctly

describe the labelled diagram?

I II IIIA Blood

capillaryLacteal Epithelial

cellB Epithelial

cellLacteal Blood

capillaryC Blood

capillaryEpithelial cell

Lacteal

D Epithelial cell

Blood capillary

Lacteal

I

IIIII

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QUICK CHECK3. Which of the following statements correctly

describe the functions of II and III?

II III

A Transports monosaccharides and amino acids

Transports fats

B Transports proteins Transports glycogen

C Transports monosaccharides and amino acids

Transports fatty acids and glycerol

D Transports fats Transports monosaccharides and amino acids.

I

IIIII

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QUICK CHECK4. How are glucose and amino acids absorbed into

the blood capillaries of the villi?a) Diffusion only.b) Diffusion and active transportc) Active transport onlyd) Osmosis and diffusion.

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QUICK CHECK5. How are water and mineral salts absorbed into the

blood capillaries of the villi?a) Active transport only.b) Diffusion and active transportc) Osmosis and active transportd) Osmosis and diffusion.