LEARNING OUTCOMES ALL MUST… Know that enzymes are used in the digestion of food in the body, which...
-
Upload
garry-daniels -
Category
Documents
-
view
212 -
download
0
Transcript of LEARNING OUTCOMES ALL MUST… Know that enzymes are used in the digestion of food in the body, which...
LEARNINGOUTCOMES
ALL MUST…
Know that enzymes are used in the digestion of food in the body, which can then be absorbed into the bloodstream
LEARNINGOUTCOMES
ALL MUST…
Know that enzymes are needed to break down (digest) large, insoluble molecules into small, soluble ones:
View the photograph on the next slide and jot down
• Where you would find it
• What produced it
• What it is
The Human Digestive System
The process of digestion has 5 functions:
Ingestion: taking food into the body
Digestion:breakdown of insoluble substances into soluble ones
Absorption: uptake of soluble substances into cells
Assimilation: how cells use food
Egestion: removal of undigested waste
Absorption
Ingestion
Digestion
Egestion
faeces
Food is broken down into smaller
pieces by biting, chewing,
churning, bile action.
These pieces are not soluble but have
a large surface area for enzymes to
work on.
2cm
2cm
2cm
Surface area = 24 cm2
Volume = 8 cm3
SA : V ratio = 24:8 = 3:1
1cm
1cm
1cm
Surface area = 6 cm2
Volume = 1 cm3
SA : V ratio = 6:1
Digestive enzymes break chemical bonds to make insoluble food
particles soluble.
Carbohydrases break down carbohydrates into sugars
Proteases break down proteins into amino acids
Lipases break down fats (lipids) into fatty acids and glycerol
model gut experiment
boiling tube
LEARNINGOUTCOMES
ALL MUST…
Label a diagram of the component parts of the digestive system and identify their function.
LEARNINGOUTCOMES
to include:• buccal cavity - the mechanical
digestion by teeth and the chemical digestion of starch by amylase;
LEARNINGOUTCOMES
to include:
• stomach - the production of gastric juice containing protease enzyme and acid, and the digestion of proteins;
Pin the pancreas on the body
What do you
remember
Salivary gland
Buccal cavity
Oesophagus
Stomach
Liver
Ileum
Appendix
Pancreas
Colon
Rectum
Duodenum
Anus
Add gall bladder, bile duct, sphincter
Mechanical: chewing, biting
Chemical: Saliva from the salivary glands contains the enzyme CARBOHYDRASE.
Starch + carbohydrase sugar (maltose)
The ball of food is called a bolus
NO FOOD IS BROKEN DOWN HERE
Muscles in the wall of the oesophagus contract, pushing food down to the
stomach. This is called PERISTALSIS
peristalsis
FOOD
Oesophagus wall
Food moves forwards
Muscles in wall contract
PERISTALSIS
The strong muscle walls contract to churn and mix food with stomach juices
called GASTRIC JUICES.
Cells in the stomach wall produce a protease enzyme that digests
proteins, breaking them down into amino acids.
The stomach cells also produce hydrochloric acid HCl, which
• Lowers the pH for the protease enzyme to work• Kills bacteria• Stops salivary amylase from working
A circular, sphincter muscle at the exit of the stomach opens to allow food into the small
intestine.
It controls release of food from the stomach.
LEARNINGOUTCOMES
to include:
• liver - the production of bile, its storage in the gall bladder and its actions in the duodenum in neutralisation of acids and emulsification of fats
LEARNINGOUTCOMES
to include:
• duodenum - enzyme production by the pancreas and the duodenal wall to include carbohydrases, lipases and proteases
LEARNINGOUTCOMES
to include:• ileum - relate its structure to its function
of absorption of digested food molecules and the ways it is adapted: large surface area (length, folds and villi), good blood supply, and thin and permeable membranes;
LEARNINGOUTCOMES
SOME MAY…
explain how the structure of a villus (finger-like shape, single layer of surface cells, capillary network and lacteal) is adapted for the efficient absorption of digested food molecules.
Bile, made in the liver and stored inthe gall bladder passes along the
bile duct into the duodenum.
Bile breaks fats into very small droplets, increasing the surface area
for enzymes to work on.This is called emulsification.
Bile is alkaline and therefore also neutralises acid from the stomach.
gall bladder
bile duct
pancreatic duct
digestive enzymes produced in pancreas
duodenum
bile made in the liverpasses into the gall bladder
ENZYMES are added to the duodenum from:• The pancreas
• The wall of the duodenum
Carbohydrases break down starch to sugars
Proteases break down protein to amino acids
Lipase breaks down fat to fatty acids and glycerol
Main function is absorption.
The walls are adapted for efficient diffusion of the soluble products of
digestion.
ridge covered with villi
villus
musclelayer
network of blood capillaries
lactealabsorbs fatty acids
arteriole venuole
single layer of epithelial cells
A villus
ileum wallMade of epithelial cells
bloodcapillaries
to liver
sugar
amino acids
lactealfatty acids
• Long length (5m), folds and villi increase the surface area for absorption
• Villi contain blood vessels to carry away absorbed nutrients
• Villi contain lacteals to carry away absorbed fats
• The walls are thin, one cell thick, and permeable to form a short diffusion distance
The absorbed nutrients, amino acids and sugars are carried in the blood to the
liver in the
HEPATIC PORTAL VEIN.
LEARNINGOUTCOMES
to include:
• colon - large surface area for water absorption;
• rectum & anus - storage and removal of faeces.
NO DIGESTION OCCURS HERE
The colon has a large surface area for the absorption of water
from the fluid we drink, food we eat, mucus and digestive juices.
It also absorbs mineral salts.
Solid waste made up of undigested food, bacteria and cells from the
gut
forms faeces,
which is stored in the rectum before passing out of the body through the
anus.
transverse colon
ascending colon
descending colon
appendixrectum
anus
Summary
bbc learning zoneclip 4180
dvd
Cut & stick activity