1. DIGESTION
B M Subramanya Swamy M.Sc. B.Ed.
CIE Co ordinator & Examination Officer
Kanaan Global School
Jakarta
Indonesia
subramanyaswamy1591978@gmail.com
3. Digestion
Process by which the body breaks down food
(carbohydrates, fats and proteins) into
simpler substances
These substances are absorbed and used by
cells in the body
4. Types of digestion
Types of digestion
Process
Mechanical
Mastication (chewing, mashing and breaking)
into smaller particles
In the mouth, teeth cuts and grinds food.
Rolling action of tongue and secretion of
saliva rolls food into bolus
Bolus is swallowed and transported through
pharynx to stomach by waves of rhythmic
contraction called peristalsis
Chemical
Changing food into smaller particles through
action of enzyme
Involves hydrolysis (addition of water)
e.g. amylase converts carbohydrates into
simple sugars
7. MOUTH
Functions : analysis material before swallowing, mechanical processing
by the teeth, tongue and palatal surfaces, lubricating, limited
digestion
8. TEETH
Functions :
Grinding action (mastication) breaks down food
Expose large area for enzyme action
child
adult
10. SALIVARY GLANDS
Secretions
Saliva contains:
Water
Functions
Moisten and soften food
As solvent and for hydrolysis
Mucus
Sticks food together to form bolus
maltose
Salivary amylase Starch
11. PHARYNX
Function : involuntary action pushes bolus into
oesophagus
Nasal cavity
Palate
Oral cavity
Tongue
Mandible
Pharynx
12. OESOPHAGUS
Functions :
• Walls made up of circular and longitudinal muscles
• Peristalsis transports food to the stomach
CARDIAC SPHINCTER
Function :
• Controls entry of food into the stomach
14. Peristalsis
Characteristic
Automatic
Length of alimentary canal made up circular and
longitudinal muscle
Alternate contraction and relaxation of muscle
Result
Movement of food down the canal
16. STOMACH
Secretions
Functions
Gastric juice
Muscular walls churn food into chyme
Stored food for 2 – 6 hours
Absorbs glucose and alcohol
Hydrochloric acid
Acidic medium (pH 1) for enzyme action
Kills bacteria brought in with food
Activates enzymes
Water
As solvent and for hydrolysis
Mucus
Protects stomach wall from acidic gastric juice
Lubricant for movement of food in the stomach
Pepsin
Protein
Rennin
Converts protein into insoluble curds (coagulates
milk) for hydrolysis of pepsin.
polypeptides
20. PANCREAS
Secretions
Functions
Pancreatic juice
Hydrolysis of food in duodenum
Amylase
Starch → maltose
Trypsin
Polypeptides → peptides
Lipase
Fats → fatty acids and glycerol
Water
As solvent for hydrolysis
Insulin
Excess glucose is converted to
glycerol in the liver
21.
22. LIVER
Secretions
Dark green bile
Functions
Provides alkaline pH
Bile is stored in the gall bladder
Emulsifies fats, provides increased
surface area for action of lipase
Neutralise acidic chyme
25. SMALL INTESTINE
Secretion
Function
Intestinal juice
Final stage of digestion pH 8 (alkaline)
DUODENUM
Secretions
Erepsin
Lactase
Sucrase
Maltase
Water
Functions
Peptides → amino acids
Lactose → glucose and galactose
Sucrose → glucose and fructose
Maltose → sucrose
As solvent and for hydrolysis
31. LARGE INTESTINE
Function : absorption of water from undigested food
CAECUM AND APPENDIX
Function :
Vestigial organs with no particular function
Forms junction of small and large intestine
COLON
Secretion
Mucus
Function
Peristalsis compact undigested food to
form faeces
Lubricates faeces and protects wall from
digestive juice
35. Comparison of human and herbivore digestive system
Human
Herbivore
Food
Carbohydrates, Mainly plant proteins
fats and proteins and cellulose
Alimentary canal
Stomach
Short
Simple
Long
Caecum
Very small
Large caecum with
cellulase to break down
cellulose to glucose
Several chambers
Contains bacteria for
digestion of cellulose
36. ABSORPTION OF DIGESTED FOOD
Nutrients from digested food must be moved from intestines
to the bloodstream
This process is called absorption
Almost all of the digested food is absorbed in the ileum
The small intestine is about 6 -7 m long
Water soluble end – products of digestion enter the blood
system by diffusion
Fatty acids and glycerol are absorbed by the lacteals
Once inside, fatty acids recombine with glycerol to form
globules of fat
They are carried by the lymphatic system to the veins
39. Adaptation of the ileum to absorb digested food
Features
Length
Adaptation
Longest part of the alimentary canal
Internal surface area Internal walls are folded to increase surface area for
absorption
Villi
Further increase surface area for absorption
Microvilli
Villus covered with epithelial cells
The plasma membrane of each cell has minute finger – like
projections (microvilli)
Further increase surface area
Movement
Villi move back and forth independently
Motion faster after meals
Absorption rate increases
Membrane
Absorption across membrane
Either by diffusion or active transport
capillary network
Dense capillary network close to epithelium
Carry away absorbed food particles quickly
Maintain concentration gradient between ileum and blood
capillaries to aid diffusion
40. ASSIMILATION
Assimilation uptake and use of food within the body
Fate of end products of digestion
End – product
Fate
Glucose
Excess is converted to glycogen (insoluble granules)
and stored in the liver
Converted back to glucose when body needs energy
and blood sugar level is low
Further excess of glucose is stored as fats in the
adipose tissue
Used in cellular respiration
Fats
Part of it stored as fats in adipose tissue
Used in synthesis of cell membrane
Utilised in respiration when glucose and glycogen is
used up
Fats stored under skin and around organs act as
energy store and insulation
41. Fate of end products of digestion
End – product
Fate
Amino acids
Synthesis of proteins, enzymes and hormones
For growth and development
Excess amino acids are not stored in the body
It is broken down and deaminated in the liver to form
ammonia and glycogen (glycogen is stored in the
liver)
Egestion
In the large intestine water and vitamins (synthesised
by bacteria) compact undigested food to form faeces
Propelled along colon and rectum
42. LIVER
• Structure
Large, reddish brown organ
Located just beneath the diaphragm and
overlaps the stomach
Plays an important role in metabolism,
homeostasis and excretion
44. • Vessels associated with the liver
Vessels
Function
Hepatic portal vein
Hepatic artery
Carries oxygenated blood to liver
Hepatic vein
Carries blood containing waste
products away from liver
Blood capillaries of villi join to
form the hepatic portal vein
Carries blood containing end
products of digestion from ileum
to liver
45. • Function of the liver
Function
Mode of action
Metabolism of glucose
Regulates the blood sugar concentration in
the body
Excess sugars stored as glycogen granules
This occurs in the presence of insulin
When plasma sugar levels fall, glucagon
converts glycogen to glucose
Metabolism of amino acids
Regulates amount of amino acids in the
body
Excess amino acids cannot be stored
Converted during deamination into glucose
and urea
Excess glucose is stored as glycogen
Urea is excreted
46. Function
Mode of action
Production of bile
Produces bile, which is used in digestion
Storage of iron
Excretion of the bile
pigment
Synthesis of plasma
proteins
Storage of vitamins
Stores vitamin A and D
Reservoir for blood
Blood spaces and network of blood
capillaries hold a large volume of blood
Stores iron from breakdown of haemoglobin
Used in the synthesis of new haemoglobin
Haemoglobin is broken down into bile
pigments biliverdin and bilirubin
Both pigments are excreted into duodenum
as bile pigments
Synthesises plasma protein (fibrinogen,
serum globulin and serum) from amino acids
They are responsible for the clotting of blood
47. Function
Mode of action
Source of heat energy
Metabolically active, producing a large
amount of heat energy to replace that lost by
the body
Heat distributed to all parts of the body
Detoxification
Toxins produced bacteria in large intestines
are absorbed and converted to harmless
substances in the liver
Liver removes about 95% of alcohol from
blood
Alcohol oxidised in the liver to energy
May also be converted to fats
The other 5% lost as sweat, urine and
during breathing
50. Vertical section of molar
Crown
Enamel
Dentine
Gum
Pulp cavity containing
nerves and blood
vessels
Root
Jaw bone
Cementum
51. Tooth structure and function
Tooth structure
Components
Function
Enamel
Non – living layer of
hard calcium salts
Dentine
Softer bone – like layer Acts as a shock absorber
Pulp cavity
Contains tooth cells,
nerves and blood
capillaries
Tooth
Cement
Thin layer of bone –
like material
Covers
Root opening
Pathway for blood
capillaries and nerves
For
Protects
dentine
Forms a hard biting surface
cells divide to form
dentine
Supply food and oxygen to
cells
dentine of root
Holds root in socket
blood supply, growth and
replacement of tooth
Nerves carry messages to
and from brain
52. Tooth structure
Components
Function
Jaw bone with socket
Bone made of calcium Tooth fits into socket
phosphate
of jaw bone
Incisor
Single root
Sharp cutting edge
Biting of pieces of
food
Canine
Single root
Sharp and pointed
Tearing, seizing food
Premolar and molar
Wide and flat surface
Has cusps (points) or
ridges
Crushing and grinding
food
53. Different types of dental formula
Omnivore
Carnivore
Herbivore
Dental
formula
i:2
c:1
pm : 2
m :3
i:3
c :1
pm : 4
m: 2
i:0
c:0
pm: 3
m: 3
2
1
2
3
3
1
4
3
3
1
3
3
Mode of
nutrition
Plant and animal
Animal
Plant
Incisor
Chisel shaped
Sharp and pointed
Canine
About the same size as
incisors
Long, pointed, curved
Diastema
X
X
Upper incisor absent
Small lower incisor,
bites against upper
horny pad
Upper canines
absent
Lower canines have
sharp edges, bites
against upper horny
pad
54. Omnivore
Premolar / molar
Surface has small
cusps
Carnassial teeth
Carnivore
Surface has sharp,
pointed edges
X
Herbivore
Surface flattened
with small cusps
X
Feeding action
Upper and lower
Upper and lower
jaw meet
jaw move up and
Grind food with
down
lateral movements Scissor – like
(side to side) of
action
lower jaw
Tight jaw
attachment
Example
Adult human
Goat
Dog
Upper and lower
jaw meet
Grind food with
lateral movements
(side to side) of
lower jaw
Loose jaw
attachment
55. Tooth Decay
Dental plaque is the result of bacteria acting on food or sugar
stuck on teeth
Tartar is the hard deposit on the teeth caused by bacterial
plaque, calcium phosphate and calcium carbonate
It leads to gum disease resulting in gum irritation and swollen
gum
As the bacteria in plaque grow, it produces acid in the layer of
plaque
This acid destroys the enamel and later, the dentine layer of
the teeth
When the decay (cavity) spreads to the pulp cavity, the entire
tooth is affected
The result is painful and swollen gum
56. Prevention of gum disease
Prevention
Action
Taking food rich in calcium,
phosphorous and vitamin D
Form strong teeth
Drinking water or using toothpaste
with added fluoride
Hardens tooth surface
Makes them less susceptible to
acids
Brushing teeth regularly
Remove food particles in teeth
Flossing teeth
Remove food lodged between
teeth
Reducing sugar in the diet
Reduce bacterial affect
Regular dental check up
Monitor health of teeth