Digestion
L3
Definitions
Digestion
 Breakdown of large molecules to small
molecules, small enough to pass through
the GI tract epithelial cells into the blood
Absorption
 passage of digested food from the GI tract
into the blood/lymph
 90% takes place in the small intestine/10%
in the large intestine
5 basic processes
Ingestion
 Movement (motility – through GI tract)
 Digestion
 Absorption
 Defecation

Gastro intestinal tract (GI)
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mouth
throat
oesophagus
stomach
small intestine
large intestine
MOUTH (Oral cavity)
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
ingestion
mastication
saliva
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CHO
salivary amylase
break down to
mono/disaccharides
FATS
lingual lipase
secreted by tongue
Oesophagus



Swallowing
bolus passes into
the stomach
Constriction of
smooth muscle
Stomach


mixing of food
(peristalsis) – CHYME
gastric emptying
Digestion
 PROTEINS
 Pepsin
(proteins –
peptides)
 FATS
 lingual lipase
Lining of stomach wall



Specialised cells
secrete digestive
enzymes
Acidic environment
Folds increase
surface area
Small intestine
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
absorption (chyme)
peristalsis – large
intestine
Duodenum- 1st 25
cm
Jejunum - middle
portion
Ileum- end portion
Digestion in Small Intestine
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CHO
Pancreatic Amylase starch – saccharides
FATS
bile salts
- emulsification – TriG – smaller droplets
Pancreatic Lipase -TriG – FA + monoG
PROTEINS
Trypsin/Peptidases proteins & peptides– Amino acids
Large intestine



5 feet
long/2.5
inches in
diameter
absorption of
water
action of
bacteria
Digestion in Large
intestine
CHO
 bacteria ferment CHO and release
Hydrogen,CO2 & Methane
PROTEIN
 bacteria convert remaining proteins to
Amino Acids
Other
organs
involved in
digestion
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Liver
Gall bladder
Pancreas
Liver
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produce bile emulsify lipids
Emulsification coating of fat droplets
with bile salts
prevents droplets from
recombining
allows more efficient
lipase action
Micelles - water
soluble fat droplets absorbed
Gall Bladder


store/concentrates
bile from the liver
secretes the bile in
response to body’s
need
Pancreas


secretion of
digestive
enzymes
Pancreatic
amylase lipase,
trypsin,
peptidase
Mouth
Food is chewed into smaller pieces
and mixed with saliva
Mouth
Food is chewed into smaller pieces
and mixed with saliva
Oesophagus
The tube that connects your mouth to
your stomach
Oesophagus
The tube that connects your mouth to
your stomach
Stomach
Muscular bag that secretes acid
Stomach
Muscular bag that secretes acid
Liver
Chemical factory - makes lots of
chemcials including bile
Liver
Chemical factory - makes lots of
chemcials including bile
Pancreas
Produces lots of different enzymes
Pancreas
Produces lots of different enzymes
Ileum
Also known as small intestine, place
where food is absorbed into the blood
Ileum
Also known as small intestine, place
where food is absorbed into the blood
Colon
Also known as large intestine, place
where water is absorbed from the
waste food
Colon
Also known as large intestine, place
where water is absorbed from the
waste food
Rectum
Waste (faeces) is stored here, ready to
be got rid of
Rectum
Waste (faeces) is stored here, ready to
be got rid of
Anus
Ring of muscle that allows the faeces
out
Anus
Ring of muscle that allows the faeces
out
Task

Assign the labels provided to the
correct place on the picture of the
digestive system