absorption 20/4/09 prepared by miss izzati apr 09
TRANSCRIPT
Absorption
20/4/09
Prepared by Miss Izzati Apr 09
Previously…
3
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).
4
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!
5
Example
(O) oesophagus
(P) chewing Starch maltoseamylase
6
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
7
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?
9
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
10
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
11
1. Large surface area: volume ratio1.3 The epithelial cells of the villi have
numerous microvilli.
Adaptations of the Small Intestine
12
13
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
14
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
15
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
16
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
18
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.
19
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
20
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.
21
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
22
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
23
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.
24
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
25
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
26
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.
27
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.