Transcript Digestive System

The Alimentary Canal
The human digestive system
consists of the alimentary canal
and its accessory glands. It’s a
long tube starting from the
mouth and ending at the anus.
Humans digest all their food
extracellularly, that is outside of
their cells.
If you laid out your alimentary canal from
end to end, how long would it be ?
a) Same as your height
b) As long as a sports car
c) As wide as a tennis court
Click here for answer
9 meters ! As wide as a tennis court !
Mouth
Esophagus
Stomach
Small Intestine
Large Intestine
Anus
Mouth
The mouth opens into a
cavity called the oral cavity.
This cavity is surrounded by
upper and lower jaws
bearing teeth.
A thick muscular tongue is
present on the floor of the
mouth cavity. It
manipulates food during
chewing and swallowing.
In mammals, it bears taste
buds to sense the taste of
food.
Upper lip
Teeth
Tongue
Lower lip
Diagram of the Human Alimentary Canal
Large Intestine
- about
1.5
Esophagus
- a 25 cm
long tube
Intestine
-gland
the
longest
m Small
long,
and
divided
into
that
opens
into
the
stomach.
Liver
- the
largest
in the
tube
in colon
the
human
body.
About
caecum,
and
rectum.
human
body.
Divided
into
left
and 7
Also
called
the
food
pipe.
The
m long,
divided
into the divided
Stomach
-awhich
ablind
'J’-shaped
right
lobes,
are
further
Caecum
–and
pouch,
about
wall
of
the
esophagus
is highly
duodenum,
the
jejunum
and
the
structure,
divided
into
three
Gall
bladder
a
hollow
pearinto
sub
lobes.
The
ducts
from
the
6
cm
long.
The
vermiform
muscular
and
no
digestion
ileum.
regions:
cardiac,
fundic
and
right
and
left
lobes,
calledis
hepatic
shaped
sac
that
stores
bile
appendix
(2-7
cm
long)
occurs
in
it.
Duodenum
-esophagus
the
initial
short
part,
Pancreas
-to
the
second
largest
ducts,
join
form
the
common
pyloric.The
opens
into
produced
by
the
liver.
attached
to
it.
somewhat
C-shaped,
and
25
gland
after
liver.
Itwhich
isabout
hepatic
duct. the
This
hepatic
duct
joins
the
cardiac
stomach,
is
Colon
is further
divided
into and
cm
long.
It receives
bile
duct
carrot-shaped
and
lies
below
and
the
cystic
duct
from
the
gall
bladder
surrounded
by
cardiac
sphincter.
the
ascending
colon,
the
pancreatic
duct.
The
concave
to
form
a bile
duct.middle
TheThe
bile
duct
and
behind
the
stomach.
head
of
The
part
in
the
is
the
portion
articulates
the
pancreas.
transverse
colon,
the
pancreatic
ductisofencircled
the pancreas
join
the
pancreas
by
the
fundic
stomach.
The
pyloric
Jejunum
–
the
part
in
the
middle;
descending
colon
and touches
sigmoid,
together
toand
form
a common
bile and
duodenum
its
tail
stomach
opens
into
the
small
about
2.5
m colon.
long.
ie,
S-shaped
pancreatic
duct
which opens into
the
spleen.
Anus
- the
opening
through
Ileum
the
final
coiled
part, by
intestine
which
is12
surrounded
duodenum
small
intestine.
Rectum -ofathe
tube
cm
long
which
undigested
about
3.6m
long. It liesfood
between
pyloric
sphincter.
that
opens
into
the
anus.
thematter
arches (faeces)
of the large
intestine.
is egested
out from the body.
Digestion Begins in the Mouth
Digestion begins in the mouth
with the mechanical action of
teeth and the chemical action of
digestive enzymes present in
the saliva. The enzyme, salivary
amylase, breaks starch into the
sugar, maltose.
Saliva lubricates the contents of
the mouth.
The tongue manipulates food into a
bolus/mushy ball as it is chewed
and initiates the swallowing
process.
Starch
Salivary Amylase
Maltose
Role of Salivary Glands in Digestion
The salivary glands secrete
saliva.
This fluid moistens food
particles, helps bind them,
and begins the chemical
digestion of carbohydrates.
Saliva is also a solvent,
dissolving foods so they can
be tasted, and it helps
cleanse the mouth and teeth.
There are two types of
secretory cells, within a
salivary gland:
 Serous cells – Produce
Amylase
 Mucous cells – Produce
mucus
Why do you think bread tastes sweet when you chew it?
Saliva converts bread, containing starch, into maltose
Role of Teeth in Digestion
Teeth are an important
feature of almost all
vertebrates.
Mammals are
characterized by
differentiation of teeth
for various functions.
Moving from front to
rear of the mouth, the
types of teeth are:
 Incisors - Tearing
 Canines - Gripping
 Premolars - Grinding
 Molars - Grinding
Esophagus (The Food Pipe)
On the way to the stomach
After being chewed and
swallowed, the food enters the
esophagus.
The esophagus is a long tube that
runs from the mouth to the
stomach. It uses rhythmic, wavelike muscle movements (called
peristalsis) to force food from
the throat into the stomach.
This muscle movement gives us
the ability to eat or drink even
when we're upside-down.
No digestion occurs in the
esophagus.
Cardiac
stomach
Esophagus
Stomach
Pyloric
stomach
Fundic
stomach
Digestion in the Stomach
The stomach has branched and
tubular glands present on its wall.
Proteins
Lipids
The secretions of these glands
are collectively called gastric
juice, which is a mixture of
Gastric
secretory products of three
Lipase
types of glands secreting
Pepsin
hydrochloric acid, protein
digesting enzyme and mucus.
In acidic medium of gastric juice
Fatty
Peptones
(pH 1 - 3), the protein digesting
acids
enzyme, pepsin, breaks down
proteins into peptones (partial
hydrolyzed protein).
Gastric lipase partially breaks
down lipids/fats.
Role of the Liver
Liver produces a fluid
called bile.
Bile is released in the
duodenum of the small
intestine via the bile
duct.
Bile breaks down fats
into smaller fatty acids
and glycerol.
Excess bile is stored in
the gall bladder.
Fats
Bile
Fatty acids
&
Glycerol
What causes our feces/poop to be
yellowish-brown in color ?
BILE !
Gall bladder
Liver
Role of the Pancreas
The pancreas produces
pancreatic juice, which
Proteins
Fats
Starch
contains the following
enzymes:
Trypsin and
Chymotrypsin: Breaks
down large proteins into
Lipase
Amylase
Trypsin
partially digested
proteins.
Pancreatic Lipase:
Breaks down fats into
fatty acids and glycerol.
Fatty acids
Peptones
Maltose
&
Pancreatic Amylase:
Glycerol
Breaks down starch into
maltose.
Digestion in the Small Intestine
The partially digested
food containing proteins, Peptones
carbohydrates and fats
enter the small intestine.
It is here that the
intestinal juice, succus
entericus, complete the
digestion of proteins into
amino acids,
carbohydrates into
glucose and fats into
fatty acids and glycerol.
Fats
Carbo
hydrates
Intestinal juice
Succus entericus
Amino
acids
Fatty acids
&
Glycerol
Glucose
Absorption in the Small Intestine
Bicarbonate ions secreted
by the small intestinal wall
makes the medium alkaline.
Inside, the wall of the small
intestine is provided with
numerous long finger-like
projections called villi,
which increase the surface
area of the inner lining of
the intestine.
This enhances the
intestinal wall’s absorption
capacity for nutrients that
are then sent to the
bloodstream.
Stomach
Small
Intestine
The Large Intestine/Colon
In the large intestine, some of
the water and chemicals like
sodium are absorbed from the
food by the walls of the intestine.
Very little digestion goes on in
the colon, as compared to the
small intestine. Many microbes
present in it (bacteria like
Bacteroides, Lactobacillus
acidophilus, Escherichia coli, and
Klebsiella) help in the digestion
process.
Undigested food matter is stored
in the rectum and finally sent out
via the anus.
Colon
Small
Intestine
Rectum
Anus
Caecum
Summary
Starch
Maltose
Amylase
Proteins
Peptones
No digestion
Peptones
Fats occurs
Carbohydrates
Trypsin,Chymotrypsin
Fats Succus entericus
Fatty acids
Fats
Bile Fatty acids
Proteins LipasePeptones
Pepsin
Maltose
LipidsStarch Partially
digested fats
Amino acidsAmylase
Fatty acids Glucose
Lipase