Download Digestive System

Digestive System
Digestion
The process of breakdown of complex food
molecules into simple molecules.
Process involves
 Ingestion (Intake of Food)
 Digestion( breakdown of food)
 Absorption ( Movement of digested food into
the blood stream)
 Assimilation (The process by which cell use
the food for cellular build up and processes)
 Egestion ( removal of waste as solid form)
Classification of organisms on the
basis of nutrition
Nutrition: The process of intake of food and its
conversion into living protoplasm in cells.
 Autotrophs- Organisms which can prepare
their food
 Heterotrophs- Organism which cannot
prepare their own food due to lack of
chlorophyll.
 Holophytic Nutrition: the mode of nutrition in
which living organisms use inorganic material
to prepare their own food
 Holozoic Nutrition: The mode of nutrition in
which living organisms ingest food from
outside and digest it in their body to obtain
energy.
Classification of Heterotrophs
 Herbivores
 Carnivores
 Omnivores
 Parasites
 Scavengers
 Saprophytes
 Sanguivores.
Nutrition in Plants
 Plants are autotrophs
and therefore prepare
their own food by the
process of
photosynthesis.
 Photosynthesis: The
process by which green
plants prepare their own
food in the presence of
sunlight utilizing
chlorophyll, CO2, water
and minerals.
Structure of LeafCuticle
Upper epidermis
Pallisade parenchyma
Bundle sheath
Xylem
Phloem
Lower epidermis
9. Spongy parenchyma
10. Guard cells
11. Intercellular space
The cells between the upper and
lower epidermis are called
mesophyll cells.
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Process of Photosynthesis
Photosynthesis is a two phase process:
Light Reaction -Light dependent reaction takes
place in the thylakoids in grana.
During this phasea) Light is absorbed by photosensitive pigment
chlorophyll present in the thylakoids.
b) Photolysis of water takes place. This forms
H+ ions.
c) The energy currencies ATPs are generated.
d) Reducing agent NADPH are formed.
 Dark Reaction -Light independent reaction
takes place in the stroma or the matrix of the
chloroplast.
During this reaction –
a) CO2 is reduced into carbohydrates
Digestion in unicellular
organisms
Intracellular digestion by intracellular
enzymes.
Nutrition in Amoeba
In amoeba, The food is
engulfed by the
process of
phagocytosis, and
then digested
intracellularly by
enzymes.
Waste is expelled out by
the Contractile
Vacuole
Contractile Vacuole in amoeba
Digestion in Human
beings.
Digestive system
Alimentary Canal
Associated Glands
Structure of the alimentary canal
Mouth



Oral cavity or Buccal cavity.
Lined by squamous epithelial tissue.
Contains tongue, teeth, salivary glands.
Tongue – muscular organ used for taste, mixing food
and cleaning the oral cavity.
 Teeth- set of teeth is called Dentition.
 Human dentition is Heterodont (4 kinds of teeth),
Thecodont (Tooth in sockets in gums), Diphydont
(Formed twice)
 Teeth help in mastication of food.
Structure of the alimentary canal
Oesophagus
 Muscular tube connecting oral cavity to the
stomach
 Conveys masticated food (bolus) by waves of
relaxation and contraction – This is called
Peristalsis.
Structure of the alimentary canal
Stomach
 Main organ of digestion
 Highly muscular
 Food is further churned and broken into simpler
molecules by the action of enzymes.
 Inner lining of stomach is called Mucosa.
 Stomach contains gastric cells that secrete HCL and
gastric juice.
 Entry of food guarded by Cardiac Sphincter and Exit
of food regulated by Pyloric sphincter.
Structure of the alimentary canal
Small Intestine
 Divided into three parts : Duodenum,
Jejunum and ileum
 Longest part of the alimentary canal.
 Site for digestion and absorption of digested
food (maximum)
 Inner lining folded into finger like projections
called villi.
 Receives digestive juices from liver, gall
bladder and pancreas.
Structure of the alimentary canal
Large intestine
 Divided into : Caecum, colon rectum and
anus.
 Most of the water is absorbed from the waste.
 Stores solid waste (faeces) in the rectum
temporarily.
 Exhibit muscular contractions and relaxation
called bowel movements – helping in
defecation.
 The exit is guarded by the anal sphincter
Structure of Associated Glands
Salivary glands present in the oral cavity.
 Three pairs called parotid, sub maxillary and
sub-lingual
 Secretes saliva containing enzyme – salivary
amylase and a bactericidal enzyme called
lysozyme.
Structure of Associated Glands
Liver
 The largest gland of the body
 Exocrine in nature
 Synthesizes and Secreted Bile.
 Regulates blood sugar by storing excess glucose as
glycogen
 Stores iron
 Converts excess amino acids into urea
 Manufactures fibrinogen and heparin( natural anticoagulant)
 Detoxifies body metabolites.
 Stores Vitamin a and D
Structure of Associated Glands
Pancreas
 Lobed mixed gland
 Secretes pancreatic juice
 Also secretes hormones
 Drains its secretions through the common bile
duct.
Structure of Associated Glands
Gall Bladder
 Small gland which store bile temporarily
Process of digestion of food
Region of
Alimentary
Canal
Digestive
glands
Digestive
Juice
Enzyme in
the juice
Class of
food acted
upon
Substance
produced
Notes
Mouth
Salivary
Glands
Saliva
Salivary
amylase
Starch
Maltose
Slightly acidic
or neutral;
Mucus help
form bolus
Stomach
Gastric glands
Gastric juice
Pepsin
Proteins
Peptides and
peptones
0.5% Hcl
provides acidic
medium for
pepsin
Rennin
Milk protein
Clots milk
Trypsin
Peptides and
peptones
Amino acids
Amylase
Starch
Maltose
Lipase
Fats
Fatty Acids and
Glycerol
Duodenum
Pancreas
Pancreatic
Juice
Bile emulsifies
fats and aids in
their
absorption into
lacteals;
Doudenum
contents are
slightly acidic.
Process of digestion of food
Region of
Alimentary
Canal
Ileum
Digestive
glands
Digestive
Juice
Enzyme in
the juice
Class of
food acted
upon
Substance
produced
Notes
Liver
Bile
No enzymes
but has
sodium salts
and bile
pigments
Fats
Emulsified fats
Sodium salts
provide
alkaline
medium
Lining of the
ileum
Succus
Entericus
Erepsin
Peptides
Amino Acids
Most
absorption
occurs in the
ileum
Lipase
Fats
Fatty acids and
Glycerol
Maltase
Maltose
Glucose
Sucrase
Sucrose
Glucose and
Fructose
Lactase
Lactose
Glucose and
Galactose