Digestion easy notes for grade stage 4 igcse

Digestion easy notes for grade 4 igcse

1. Digestion
10/12/19

2. LEARNING OUTCOME
•Define digestion
•Nutrition and steps of nutrition
•Organs involved in digestion
•Function of each organ
•Role of different enzymes involved in digestion

3. The Digestive System
•Thefunctionsofthedigestivesystemare:
–digestion:breakingdownfoodsothatitissmall
andsolublesubstances.
–absorption:transportingdigestedfoodmolecules
fromthegutintotheblood
http://kidshealth.org/PageManager.jsp?lic=1&article_set=59299&cat_id=20607
http://www.bbc.co.uk/education/clips/z7vygk7

4. Process of Nutrition
STEPS DEFINITION
IngestionIntake of food.
i.e. eating
DigestionBreaking down of food so that it can be absorbed
AbsorptionThe process of absorbing food in the form of
nutrients into the blood stream
AssimilationThe process of nutrients being absorbed by each cell
of the body in the form of energy
Egestion: Secretion of waste, unwanted and excess substances
from the body after food has been digested.

5. LearningOutcomes:
Recall the different parts of the digestive system
Explain the functions of the different digestive organs
Did you know… The hydrochloric acid
that is found in our stomach is strong
enough to melt zinc metal. There is a
layer of mucus that protect the cells
and the cells regrow quickly which
protects our stomach from getting
damaged.

6. Mouth
Salivary Glands
Anus
Rectum
Small intestine
Large intestine
Pancreas
Oesophagus
Stomach
Liver
ORGAN
SYSTEM

7. Enzymes break down large
insoluble food molecules into
smaller soluble ones.
These soluble food molecules
are then adsorbed into the
blood through the small
intestine.
Enzymes in digestion

9. Theoesophaguscarriesfoodtothe
stomach.
Theoesophagusisamusculartube.
Foodispushedthroughthe
oesophagusandintothestomachby
meansofaseriesofcontractionscalled
peristalsis.

10. Digestion in the stomach
When food enters the stomach it stimulates the secretion of hydrochloric
acid(HCl) from the stomachwall. HCl increases the acidity of the stomach
to about pH2 –the optimum pH for stomach enzymes.
oesophagus
duodenum
mucus cells
parietal cells
(acid-producing)
gastric gland

11. Digestion in the Small
Intestine
•Digestive enzymes found in the small
intestine are damaged by a strongly
acidic pH.
How does the body avoid this problem?
•The liver produces bile(an alkali),
which is stored in the gall bladder and
released into the small intestine.
Big Question: What roles do different enzymes play in the
body?
gall
bladder
duodenum bile duct
pancreas
hepatic
duct

13. •The small intestine has a very
large surface area covered in
villi.
•It also has a rich blood supply
and short diffusion distance to
the blood vessels
•This greatly increases diffusion
and active transport of food
into the blood.
The small intestine

14. Villi

15. Water adsorption at the large intestine
•The muscular walls of
the small intestine
squeeze undigested
food (peristalsis) on to
the large intestine.
•This is where water is
adsorbedfrom the
undigested food into
your blood

16. The rectum is an eight-inch chamber that
connects the colon to the anus.
The rectum:
•Receives stool from the large intestine.
•Lets the person know there is a stool to
be evacuated.
•Holds the stool until evacuation
happens.
Theanusisthelastpartofthedigestive
tract.

17. Other organs involved in
digestion
•The liver is also
involved in digestion
(amongst other roles
such as
detoxification).
•The liver produces bile
which aids in the
digestion of lipids
(fats).

19. •Carbohydrate enzyme –carbohydrase
•Fat enzyme –lipase
•Protein enzyme -protease
Amongotherfunctions,the
pancreasproducesdigestive
enzymes.
Thesearesecretedintothefirstsegmentofthe
smallintestine.
Theseenzymesbreakdownproteins,fats,and
carbohydrates.
Thepancreasalsomakesinsulin,secretingit
directlyintothebloodstream.Insulinisthe
chiefhormoneformetabolisingsugar.

20. Mouth vii. Beginning of the digestive track. Mechanical
digestiontakes place here
Oesophagus ix. Carries food and liquids from the mouth to the
stomach
Stomach iv. Stores food and begins digestion due to
hydrochloric acid found there
Liver iii. Produces bile
Gall bladder vi. Stores bile after it is made, until required in
digestion
Pancreas i. Produces digestive fluids and enzymes. Also
regulates blood sugar
Smaller intestineii. Digests and absorbs soluble food
Large intestinev. Absorbs water from undigested food and
produces faeces
Rectum viii. End of the large intestine and storage for faeces
Anus x. Excretion of faeces

21. Challenge –Beat the question grid
1.State 3 organs
of the digestive
system
4.State the function
of the mouth
7. State the typeof
tissue which lines the
small intestine.
2. Name thefirst
organ of the
digestive system
5.State the function
of the oesophagus
8. Explain how the
small intestine is
adapted to its function
3.Name the last
organ of the
digestive system
6. Describe the role
of enzymes in
digestion
9.Explain the role of
the liver within
digestion