Download Mammalian digestion powerpoint File

Mammalian digestion
Teeth
• Teeth provide mechanical
digestion by tearing food
up into bits.
• See teeth powerpoint for
differences in herbivore
and carnivore dentition.
• Food is mixed with saliva
which helps form it into a
bolus.
• saliva also contains the
enzyme salivary amylase
which acts on starch ( see
next slide)
Salivary Amylase
• Salivary amylase works
on insoluble starch and
breaks it down into
maltose which is
soluble.
• Salivary amylase works
best in slightly alkali
conditions so the
mouth has a pH of 11
swallowing
• muscular contractions
of the tongue push the
food past the pharynx.
• The epiglottis closes
over the wind pipe
preventing food from
entering
Peristalsis
• Food moves through
the gut by a wave of
peristalsis.
• The wall of the gut in
front of the bolus of
food relaxes and the
muscles behind the
food contract pushing it
forward.
The stomach
• Gastric juice is mixed with
the food and it is churned
up to produce chyme.
• pepsin (enzyme) acts on
protein to break it down
into polypeptides.
• HCl ( hydrochloric acid)
helps break down food
and kills most bacteria.
• Pepsin only works in acid
conditions.
• Food is released through
the pyloric sphincter a
small amount at a time.
The duodenum (upper small intestine)
Lots of enzymes breakdown the food
The duodenum secretes:- the pancreas secretes:• Maltase to breakdown
• amylase to breakdown
maltose into glucose.
starch to maltose
• Peptidases to
• Trypsin and
breakdown
chymotrypsin to
polypeptides into amino
breakdown protein to
acids.
polypeptides.
• Lipase to breakdown
fats to fatty acid and
glycerol
… still in the duodenum
• Bile which is made in
the liver and stored in
the gall bladder is
released. Its job is to
emulsify any fat into
small droplets to make
it easier to digest.
In the ileum ( lower small intestine)
• Digested food is
absorbed through the
wall of the gut into the
blood.
• The small intestine is
covered with villi which
are covered in microvilli
to increase the surface
area for absorption.
The large intestine
• this consists of the
appendix, caecum and
colon.
• In humans the appendix
does nothing(- ish) and
the large intestines
function is the
reabsorption of water,
electrolytes ( Na+) and
some vitamins.
• Faeces is collected in the
rectum and egested
through the anus.
Digestion in ruminants
• cows, goats and sheep
are foregut fermenters.
• The stomach is divided
into a series of chambers
to slow digestion and give
tough plant material time
to break down.
• They rely on microbes in
the rumen to break down
cellulose.
• They regurgitate, rechew
and reswallow partly
digested food.
•
Food is digested slowly in
different parts of the multi
chambered rumen by
bacteria.
• Bacteria ferment the plant
material to make methane,
and VFA ( volatile fatty
acids) which are absorbed
into the blood stream.
• Herbivores have long guts
to digest and absorb plants
• Ruminants burp and fart a
lot.
Hindgut fermenters
• Horses and rodents
have bacteria in their
hind gut or caecum to
digest vegetation to
make VFA’s which are
absorbed into the blood
.
• Rabbits are
caecotrophes (see next
slide)
Rabbits make 2 types of poo.
Carnivores have much shorter guts.
• Meat and
animal
products are
easier to
digest and
have more
energy. This
allows
carnivores to
have much
shorter guts.
Carnivore vs ruminant
Insectivore vs hind gut fermenter