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Prepared by: Department of Biology and
Human Biology (CGS).
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Prepared by: Department of Biology and
Human Biology (CGS).
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Feeding: The intake of food into the body.
Digestion: The process in which large complex
molecules are broken down into soluble and diffusible
that can be absorbed into the body cells.
Absorption: The process in which digested food
materials are taken into the body cells.
Assimilation: The process whereby some of the food
materials are converted into new protoplasm or used
to provide energy.
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Digestion is defined as the breakdown of
nutrients
We consume:
Carbohydrates
Proteins
Fats
These are broken down into their simplest
forms
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Human Biology (CGS).
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Mouth & Buccal Cavity
The Pharynx
Oesophagus
Stomach
The Liver & the Gall Bladder
Pancreas
Small intestine
Large intestine
Anus
Prepared by: Department of Biology and
Human Biology (CGS).
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Human Biology (CGS).
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Mechanical digestion: the act of chewing
Carbohydrate digestion begins here
Saliva moistens food and contains the enzyme
Salivary Amylase – breaks down complex carbs into
simple sugars. Mucin in saliva softens the food.
Chemical Digestion: enzymes breaking down
carbohydrates
Ball of moistened, partially digested food, known
as the “BOLUS”, moves into the oesophagus
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Human Biology (CGS).
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Human Biology (CGS).
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Prepared by: Department of Biology and
Human Biology (CGS).
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Prepared by: Department of Biology and
Human Biology (CGS).
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Long tube through which “bolus” moves down
into the stomach.
It takes 7 seconds to make the journey.
The contraction of muscles pushes the food
down – known as PERISTALSIS
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Human Biology (CGS).
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PERISTALSIS
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Human Biology (CGS).
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Human Biology (CGS).
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 Protein digestion begins here
The HCL secreted :
 Stops action of salivary amylase
 Provides medium for the gastric enzymes(pepsin
and rennin) to work.
 Changes pepsinogen to pepsin and prorennin to
rennin
 Provides medium for the gastric enzymes to
work.
 Kills germs
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Human Biology (CGS).
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 Pepsin
converts protein into
polypeptide
 Rennin clots soluable milk protein
caseinogen into insoluble casein.
 Then pepsin converts the
insoluble milk protein into
polypeptide.
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Human Biology (CGS).
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Continuation of Carbohydrate and Protein
Digestion; beginning of Fat digestion
The small intestine consists of a U-shaped
duodenum, the jejunum and the much
coiled ileum.
The gland secretes digestive enzymes.
LIVER: releases bile that breaks down fats
into fatty acids
PANCREAS: releases pancreatic juices, of
which completes protein digestion (proteins
to amino acids) and carbohydrate digestion
(complex sugars into simple
monosaccharides)
Absorption of simple nutrients through villi
occurs here
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Human Biology (CGS).
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In the intestine, the Chyme stimulates:
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The intestinal glands to secrete intestinal juice.
The pancreas to secrete pancreatic juice which
passes through the pancreatic duct into the
duodenum.
The gallbladder to release bile.
Three of them are alkaline in nature which
neutralizes the acidic chyme and provides suitable
medium for the enzymes to work.
Trypsinogen converted by enterokinase to
trypsin, protein to peptides by trypsin
and peptides to amino acids by erepsin
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Human Biology (CGS).
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Human Biology (CGS).
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The small intestine also has numerous minute
finger like projection called Villi.
Villi contains numerous microvilli over them.
The villi are richly supplied with blood vessels and
lymphatic vessels to carry food substances.
In each Villus a lacteal is surrounded by blood
vessels.
Glucose and amino acids are absorbed by blood
vessels and supplied to the liver
Glycerol and fatty acids are combined within the
epithelial cells of villi to form small fat globules
and absorbed by lacteal vessels.
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Human Biology (CGS).
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The blood vessels from the intestine unite form a
large vein, the HEPATIC PORTAL vein, which
transports mainly amino acids & sugars to the
liver.Glucose is converted to the glycogen and
stored in the liver.
Excess amino acids are Deaminated. The amino
group is removed converted to urea, which is
removed by urine.
The remains of amino acids are converted into
glucose and stored as excess glycogen.
Fats, are converted to form that can be oxidised or
stored in liver . In inadequate supply of glucose,
the fats are oxidised to provide the energy.
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Human Biology (CGS).
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Functions of Liver:
•Regulation of blood
glucose level
•Protein synthesis
•Iron storage
•Detoxification
•Heat production
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Human Biology (CGS).
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Unabsorbed material moves
through large intestine,
where water and salt are
absorbed
This removal of liquid forms
solid-like faeces; known as
Egestion
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Faeces is stored in the colon
Faeces is removed from the
body, via the anus, by the
process of ELIMINATION
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Region
Secretion Source
Enzyme
Action
Mouth
SALIVA
SALIVARY
GLANDS
Salivary
amylase
starch--maltose
Stomach
Gastric
juice
Gastric
glands
Rennin
pepsin
Prepared by: Department of Biology and Human
Biology (CGS).
Soluble
caseinogens---insoluble
casein
Proteins---polypeptides
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Region Secretion
Source
Enzyme
Action
Small
Bile
Intestine
Liver
------
emulsifies
fat
Pancreatic
juice
Pancreas
Amylase
Trypsin
Lipase
Starch--maltose
Proteins--polypeptides
Fats---fatty
acids &
glycerol
Intestinal
Juice
Intestinal
Glands
Enterokinase
Maltase
Lactase
Sucrase
Erepsin
lipase
Trypsinogen--trypsin
Maltase---glucose
Lactose---Glucose
& galactose
Sucrose—glucose
&fructose
Polypeptides--amino acids
Fats--- fatty acids
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& glycerol.
Prepared by: Department of Biology and Human
Biology (CGS).
Class Work:
Q/A:
1. Describe the digestive processes in the stomach. [5]
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Human Biology (CGS).
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Prepared by: Department of Biology and
Human Biology (CGS).
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