Digestive system

1.

2. FOOD

• A nutrient is a substance required
by the body for energy, growth,
repair, and maintenance. Nutrients
in food and beverages include
carbohydrates, lipids, proteins,
vitamins, and minerals.

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4.

Energy and Building Materials
• Each nutrient plays a different role
in maintaining a healthy body.
• Carbohydrates, proteins, and lipids
are involved in providing both
energy and building materials to
the cells.

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6.

Carbohydrates
Carbohydrates that exist as single sugar
molecules are called monosaccharides or
simple carbohydrates. Carbohydrates
made of two or many sugar molecules
linked together by chemical bonds are
called complex carbohydrates.
Complex carbohydrates must be broken
down into simple sugars before cells can
use their energy.

7.

Proteins
Amino acids from proteins are used
by the body for making additional
proteins. Extra amino acids in the
diet are used for energy or converted
to fat.
The body needs 20 different amino
acids to function. Ten amino acids
(called essential amino acids) must be
obtained directly from food.

8.

Lipids
The body uses lipids to make steroid
hormones and cell membranes and to
store energy.
Fats are lipids that store energy in
plants and animals. Fats are also
stored around organs and act as
padding and insulation.

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10.

• Vitamins are organic substances
that occur in foods in small
Vitamins,
Minerals,
and Water
amounts.
They
are necessary
in
trace amounts for the normal
metabolic functioning of the body.
• Minerals are naturally occurring
inorganic substances that re used to
make certain body structures and
substances. They are also needed
for normal nerve and muscle
function.

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13.

14. DIGESTION

Organisms must break down their
foodstuffs into their components for
passing through
the cell membrane.
This process is
called digestion.

15.

TYPES OF DIGESTION
There are two types of digestion.
These are;
• Mechanical digestion
• Chemical digestion

16. MECHANICAL DIGESTION

Pieces of food are firstly cut, crushed,
or broken into smaller particles
without being changed chemically.
This process is called mechanical
digestion.
Mechanical breakdown increases the
surface area of the food particles.
.
Protein
Protein

17.

18.

CHEMICAL DIGESTION
• Chemical digestion is series of
reactions in which foods are
hydrolyzed, aided by water and
enzymes. Food split into its
monomers by means of chemical
digestion.
STARCH + WATER
n GLUCOSE

19.

20. TYPES OF DIGESTION ACCORDING TO THE THEIR MEDIUM

• There are two types digestion
according to the their
medium.These are
• EXTRACELLULAR DIGESTION
• INTRACELLULAR DIGESTION

21. INTRACELLULAR DIGESTION

•In unicellular organisms foodstuffs
are digested within food vacuoles in
the cytoplasm. They are taken into
cell by pinocytosis or phagositosis.

22. EXTRACELLULAR DIGESTION

In this process, digestion of food
takes place within an area external
to the organism by the secretion of
digestive enzymes.
Extracellular digestion is seen in
protista, invertebrates and all
vertebrates.

23.

24. HUMAN DIGESTIVE SYSTEM

The digestive system is made up of
highly specialized digestive tube and
several organs.
Human Digestive System includes;
•Mouth
•Eusophagus
•Stomach
•Small Intestine
•Large Intestine

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28.

29. MOUTH

•Food enters the body through the
mouth.
•Mechanical and chemical digestion
occur in mouth. Teeth help in
mechanical digestion.
•There are three pairs of salivary glands
in the lining of the mouth. Salivary
glands secrete saliva into the mouth.
They help in chemical digestion

30.

31. TEETH

•Teeth are adapted for mechanical
digestion of food.
• Each tooth is composed of crown
and root
• The crown is covered with enamel.
It is hardest material of our body.

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34.

35.

36. TYPES OF TEETH

• There are 4 types of teeth. These are
1- Molars
12
2- Pre molars
8
3- Canines
4
4- Incisors
8
TOTAL
32

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40.

41. ESOPHAGUS

•After chewing of food, it is pushed by
the tongue to the esophagus. The
esophagus connects mouth with the
stomach.
• Peristalsis begins in the esophagus.
Peristalsis is the series rhythmic muscles
contraction and relaxations. Food moves
through the digestion system by
peristalsis.

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44.

45. STOMACH

• Food is stored temporarily in the
stomach. Mechanical and chemical
digestion occur in mouth. Food is
broken down mechanically into
smaller particles by the
contractions of the muscles.
• Stomach secretes enzymes for
chemical digestion

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50.

SMALL INTESTINE
• Most digestion and absorption
occur in small intestine. Most
chemical digestion and all
absorption occur in ileum. All
digestion is completed in the small
intestine.
• The small intestine has three parts.
They are duodenum jejunum and
ileum.

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56.

LARGE INTESTINE
• Undigested materials pass from the
small intestine into the large
intestine. There is no digestion in
this part.
• The large intestine contains many
bacteria. They produce vitamins
such as vitamin K.
• Large intestine opens to the outside
of the body through the anus.

57. FUNCTIONS OF LARGE INTESTINE

• Reabsorption of water
• Absoption of vitamins
• Eliminations of undigested
materials

58.

59. DIGESTION OF CARBOHYDRATES IN THE MOUTH

• Chemical digestion of carbohydrate
starts in mouth. Salivary glands secrete
saliva into the mouth. Saliva is juice
which contain digestive enzyme is
called ptyalin or amylase.
• Amylase breaks down starch into
dextrin and maltose.
Amylase
Starch + Water
Dextrin + Maltose

60. DIGESTION OF CARBOHYDRATES IN THE STOMACH

•Stomach is an acidic area. Amylase
can not work in acidic region.
•Therefore chemical digestion of
carbohydrates stop in stomach.

61. DIGESTION OF CARBOHYDRATES IN THE SMALL INTESTINE

When food passes into the small
intestine from stomach, it stimulates
cells of small intestine. Than small
intestine secretes two hormones into
the blood. These hormones are
secretin and cholecystokinin.

62.

They stimulate pancreas and it
secretes pancreatic enzymes to
small intestine. Enzymes act on
every types of carbohydrates.
Pancreatic juice includes
amylase, maltase, lactase and
sucrase.

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64.

Dextrin + H2O
Maltose + H2O
Sucrose + H2O
Lactose + H2O
Amylase
Maltase
Sucrase
Lactase
Glucose + Glucose +……
Glucose + Glucose
Glucose + Fructose
Glucose + Galactose
Digestion of carbohydrates is
completed in small intestine.

65.

66. DIGESTION OF PROTEINS

• Digestion of protein starts in stomach
and complete in small intestine.
• When food enter the stomach, it
stimulates some stomach cells.These
cells secretes GASTRINE hormone.
This hormone stimulates gastric
gland and it produces gastric juice.
• Gastric Juice is composed of;
Mucus, HCl and Pepsinogen

67. REACTIONS IN THE STOMACH

Pepsinogen + HCl
Protein + H2O
Milk + H2O
Casein+ H2O
Pepsin
Pepsin
Peptones
Rennin
Pepsin
Casein
Peptones + a.a….

68. DIGESTION OF PROTEINS IN THE INTESTINE

• Tripsinogen and Chymotripsinogen
take role in the digestion of proteins
that are secreted by pancreas.
• Enterocinase and Erepsin are
secreted by intestinal glands to
digest proteins.

69. DIGESTION OF PROTEINS IN THE SMALL INTESTINE

Tripsinogen + Enterocinase
Peptones+H2O
Tripsin Peptides + Amino acids
Erepsin
Peptides+ H2O
Tripsin
aa + aa + aa + aa +…

70.

71. DIGESTION OF LIPIDS

•Digestion of lipid occurs only in
small intestine. The cells of the liver
produce bile. Than it is stored in gall
bladder. When food enters to small
intestine it secretes cholecystokinin
hormone. This hormone causes
removing of bile from gall bladder
to small intestine.

72.

• Bile does not contain enzyme
but it aids mechanical digestion
of lipid. This process is called
emulsification.

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74.

75. Lipid

Bile
Small lipid particles
Lipase is secreted from pancreas.
Lipase breaks down lipid molecules
into fatty acids and glycerol.
Lipid + H2O
Lipase
3 Fatty acid + Glycerol

76.

77. ABSORBTION

• There are many finger like projections in
lining of small intestine.They are called
VILLI.
• Villi increas the absorption surface of
small intestine.
• Passing of digested materials from small
intestine to blood is called absorption.
• Vitamins and inorganic materials pass
into the blood without digestion.

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79.

• The digestive products of
carbohydrates, aminoacids and
vitamins pass from the microvilli to
the venules (the small branches of the
veins).
• Fatty acids and glycerol pass from the
microvilli to the lymph circulation.