Human Digestive System: Major Organs and Functions
H
UMAN
DIGESTIVE SYSTEM
OVERVIEW
M
a
j
o
r
o
r
g
a
n
s
Mouth
Esophagus
Stomach
small
intestine
large
intestine
A
c
e
s
s
o
r
y
o
r
g
a
n
s
:
Liver
gall
bladder
Pancreas.
H
UMAN DIGESTIVE
SYSTEM
M
a
j
o
r
o
r
g
a
n
s
Mouth
Esophagus
Stomach
small
intestine
large
intestine.
A
c
e
s
s
o
r
y
o
r
g
a
n
s
:
Liver
Gall
bladder
Pancreas.
The process
of
reducing food into smaller
molecules
that
can be absorbed into the
body
D
i
g
e
s
t
i
v
e
s
y
s
t
e
m
c
o
n
s
i
s
t
s
o
f
2
m
a
j
o
r
p
a
r
t
s
MAJOR
ORGANS
T
HE
M
OUTH
p
H
:
7
The first part of the digestive
system
the entry point of
food.
S
t
r
u
c
t
u
r
e
s
i
n
t
h
e
m
o
u
t
h
t
h
a
t
a
i
d
s
d
i
g
e
s
t
i
o
n
Teeth
– cut,
tear,
crush and grind
food.
Salivary glands
– produce and secrete
saliva into the oral
cavity.
s
a
l
i
v
a
moistens the
food
c
o
n
t
a
i
n
s
e
n
z
y
m
e
s
(
p
t
y
a
l
i
n
o
r
s
a
l
i
v
a
r
y
a
m
y
l
a
s
e
)
b
e
g
i
n
s
d
i
g
e
s
t
i
o
n
o
f
s
t
a
r
c
h
i
n
t
o
s
m
a
l
l
e
r
p
o
l
y
s
a
c
c
h
a
r
i
d
e
s
.
F
u
n
c
t
i
o
n
:
Mechanical
digestion.
increasing surface area for faster chemical
digestion.
T
h
e
E
s
o
p
h
a
g
u
s
a tube connecting the mouth to the
stomach
running through the Thoracic
cavity.
L
o
c
a
t
i
o
n
:
lies behind windpipe
(Trachea).
o
T
h
e
t
r
a
c
h
e
a
h
a
s
a
s
a
n
e
p
i
g
l
o
t
t
i
s
o
preventing food from entering the
windpipe,
o
moving the food to the esophagus while
swallowing.
F
o
o
d
t
r
a
v
e
l
s
d
o
w
n
t
h
e
e
s
o
p
h
a
g
u
s
,
t
h
r
o
u
g
h
a
s
e
r
i
e
s
o
f
i
n
v
o
l
u
n
t
a
r
y
r
h
y
t
h
m
i
c
c
o
n
t
r
a
c
t
i
o
n
s
(
w
a
v
e
-
l
i
k
e
)
c
a
l
l
e
d
p
e
r
i
s
t
a
l
s
i
s
.
F
u
n
c
t
i
o
n
:
•
The lining of the
esophagus
secretes
mucus
•
L
ubricating
to support the
movement
of
food.
E
SOPHAGEAL
SPHINCTER
:
•
bolus reaches
the
stomach
•
must pass through a
muscular ringed
valve
called the
esophageal
sphincter (Cardiac
Sphincter).
•
F
u
n
c
t
i
o
n
:
•
prevent stomach
acids
from back flowing into
the
esophagus.
S
T
OMACH
J-shaped muscular
sac
H
a
s
i
n
n
e
r
f
o
l
d
s
(
r
u
g
a
e
)
Increasing
surface area of the
stomach.
F
u
n
c
t
i
o
n
:
Stomach performs mechanical
digestion
H
O
W
By churning the bolus and mixing it with the gastric
juices
secreted by the lining of the
stomach.
G
A
S
T
R
I
C
J
U
I
C
E
S
HCl, salts, enzymes, water and
mucus
.
HCL helps break down of food and kills bacteria that
came
along with
the
food.
T
h
e
b
o
l
u
s
i
s
n
o
w
c
a
l
l
e
d
C
h
y
m
e
.
E
NZYMES IN
STOMACH
:
Acidic environment
H
C
l
s
e
c
r
e
a
t
i
o
n
kill any microbes that are found in
the
bolus,
creating a pH of
2.
Mucus prevents the stomach from digesting
itself.
P
e
p
s
i
n
s
e
c
r
e
a
t
i
o
n
responsible for initiating
the
breakdown of proteins (in
)food.
hydrolyzes proteins to
yield
polypeptides.
P
y
l
o
r
i
c
s
p
h
i
n
c
t
e
r
:
chyme moves from
the
stomach to the small
intestine.
It passes through a
muscular ringed sphincter
called the pyloric
sphincter.
S
T
O
M
A
C
H
D
O
E
S
N
O
T
D
I
G
E
S
T
I
T
S
E
L
F
W
HY
?
First the stomach only secretes small amounts of
gastric juices until food
is
present.
2.
Second the secretion of mucus coats the lining of
the
stomach protecting
it from the gastric
juices.
3.
The third mechanism is the digestive enzyme pepsin
is secreted in an
inactive
protein called pepsinogen. Pepsinogen is converted to pepsin
in the increased presence of hydrochloric acid (pH
1).
P
r
o
t
e
c
t
i
v
e
M
e
c
h
a
n
i
s
m
:
3
protective
mechanisms.
1.
S
MALL
INTESTINE
R
esponsible for the
complete
digestion
of
all
M
acromolecules
and
the absorption
of
their component
molecules
E.g
G
lucose
Glycerol
F
atty
acids
A
mino
acids
N
ucleotides
P
ARTS
OF SMALL
INTESTINE
The
small
intestine
is made up of three
parts
D
u
o
d
e
n
u
m
J
e
j
u
n
u
m
i
l
e
u
m
1.D
UOD
E
N
U
M
T
h
e
f
i
r
s
t
p
a
r
t
i
s
t
h
e
d
u
o
d
e
n
u
m
,
u
-
s
h
a
p
e
d
o
r
g
a
n
.
approximately 30
cm
in
length.
This area completes
most
of
the
digestion processes.
E
n
z
y
m
e
s
a
r
e
s
e
c
r
e
t
e
d
i
n
t
o
t
h
e
d
u
o
d
e
n
u
m
f
o
r
m
t
h
e
p
a
n
c
r
e
a
s
a
n
d
t
h
e
g
a
l
l
b
l
a
d
d
e
r
.
T
h
e
d
u
o
d
e
n
u
m
i
s
l
i
n
e
d
b
y
f
o
l
d
s
o
f
t
i
s
s
u
e
c
a
l
l
e
d
v
i
l
l
i
.
T
h
e
v
i
l
l
i
a
r
e
c
o
v
e
r
e
d
b
y
f
i
n
e
b
r
u
s
h
-
l
i
k
e
m
i
c
r
o
v
i
l
l
i
.
These folds increase
the
surface
area of
the
small intestine increase
the rate of
absorption.
2.
J
E
J
U
N
UM
T
h
e
j
e
j
u
n
u
m
i
s
a
p
p
r
o
x
i
m
a
t
e
l
y
2
.
5
m
l
o
n
g
.
Although some digestion is completed here,
it
has
more villi and microvilli;
its
role is absorption o
f
nutrients.
3
.
I
l
e
u
m
o
T
h
e
i
l
e
u
m
,
i
s
a
p
p
r
o
x
i
m
a
t
e
l
y
3
m
l
o
n
g
.
o
has fewer villi and microvilli than the other
two
parts.
o
Although absorption also occurs here,
it
is
responsible
for
pushing
the
waste materials into
the
large
intestine.
F
UNCTIONS
OF
THE SMALL
INTESTINE
90%
of the
digestion and absorption
of food
occurs
other 10% taking place in
the
stomach and large
intestine.
The
main function
of the small
intestine is absorption
of
nutrients and minerals
from
food.
D
i
g
e
s
t
i
o
n
o
f
p
r
o
t
e
i
n
s
Proteins, peptides and amino acids
are acted
upon by
enzymes such as
trypsin
and chymotrypsin, secreted by
the
pancreas. This breaks
them
down
to
smaller
peptides.
D
IGESTION
OF
LIPIDS
Enzymes,
like
lipases secreted from the
pancreas,
act
on fats and lipids in
diet.
L
ipase can break them into the smaller parts that
can enter the intestinal villi for
absorption.
D
i
g
e
s
t
i
o
n
o
f
c
a
r
b
o
h
y
d
r
a
t
e
s
Carbohydrates are broken down to simple sugars and
monosaccharides like
glucose.
Pancreatic amylase breaks down some
carbohydrates
to
oligosaccharides
as
well.
Some carbohydrates and fibers pass undigested to the
large intestine where they
may,
depending on their type,
be broken-down by intestinal
bacteria.
A
BSORPTION
IN
THE SMALL
INTESTINES
T
he
nutrients
are
absorbed
by the
inner walls
of
the
small intestine into the blood
stream.
The
nutrients are absorbed by processes of
simple/passive
diffusion,
facilitated
diffusion,
primary active transport, or secondary active
transport.
For
transport, nutrients commonly rely
upon
Lipids
–
undergo passive or simple
diffusion
Short-chain
fatty
acids
–
diffusion
Amino acids
–
primary active
transport
Glucose
–
secondary active
transport
Fructose –
facilitated
diffusion
A
BSORPTION
IN
THE SMALL
INTESTINES
Other
absorbed substances
in the
small
intestines
include:
1
.
W
a
t
e
r
80% is absorbed by the small
intestine
10% by
the
large
intestine
remaining 10% excreted in
the
faeces.
2
.
E
l
e
c
t
r
o
l
y
t
e
s
3
.
V
i
t
a
m
i
n
s
a
n
d
m
i
n
e
r
a
l
s
L
A
R
G
E
I
N
T
E
S
T
I
N
E
(
p
a
r
t
s
&
f
u
n
c
t
i
o
n
)
C
OMPONENTS
OF
L
ARGE
I
NTESTINE
The large intestine is composed of several very
distinctive
parts:
C
e
c
u
m
:
C
o
l
o
n
:
T
h
e
c
o
l
o
n
c
o
n
s
i
s
t
s
o
f
f
o
u
r
p
a
r
t
s
:
Ascending
colon
Transverse
colon
Descending
colon
Sigmoid
colon
R
e
c
t
u
m
C
ECUM
F
irst section of your large
intestine
looks like a
pouch,
two inches
long.
R
O
L
E
T
aking
in
digested
liquid
from the ileum(small intestine)
&
passes it on to the
colon.
C
OLON
:
major section of the large
intestine
F
u
n
c
t
i
o
n
:
the principal place for water
reabsorption,
absorbs salts when
needed.
C
o
m
p
o
n
e
n
t
s
:
The colon consists of 4
parts:
Ascending
colon
Transverse
colon
Descending
colon
Sigmoid
colon
C
OMPONENTS
OF
COLON
A
s
c
e
n
d
i
n
g
c
o
l
o
n
:
1st portion of the
colon
pushes any undigested debris up
from
the
cecum
just under the right lower end of the
liver.
T
r
a
n
s
v
e
r
s
e
c
o
l
o
n
:
2nd portion of the
colon
Food traveling from left
to
right just
under
your
stomach.
C
OMPONENTS
OF
COLON
D
e
s
c
e
n
d
i
n
g
c
o
l
o
n
:
3
r
d
p
o
r
t
i
o
n
o
f
c
o
l
o
n
pushes its contents from
down to the lower left side
of
your
abdomen
S
i
g
m
o
i
d
c
o
l
o
n
:
final
S-shaped length of the
colon,
empties into the
rectum.
R
E
C
TUM
The final
section
measures from 1
to
1.6 inches (or 2.5 to 4
cm).
Leftover waste collects
there
expanding the
rectum
emptied
through
anus
F
UNCTION
OF
L
ARGE
I
NTESTINE
1
.
A
b
s
o
r
b
W
a
t
e
r
One of the primary functions is to absorb
water
prepare the waste as a solid stool that will be expelled
from
the
body.
2
.
A
b
s
o
r
b
V
i
t
a
m
i
n
beneficial
bacteria
role in breaking down undigested sugars and fibers into
fatty
acids.
produce many vitamins, of which are
Vitamin
K and
Biotin
that
are absorbed back into the
body.
F
UNCTION
OF
L
ARGE
I
NTESTINE
(
LI
)
3
.
R
e
d
u
c
e
A
c
i
d
i
t
y
The
fatty
acids cause acidic
environment.
The LI produces alkaline
solutions
reduce the acidity and balance the pH in the
LI
4
.
P
r
o
t
e
c
t
f
r
o
m
I
n
f
e
c
t
i
o
n
s
The mucous lining of the large intestine acts as a
protective
layer
prevents harmful bacteria from being reabsorbed into
the
body.
F
UNCTION
OF
L
ARGE
I
NTESTINE
(
LI
)
5
.
P
r
o
d
u
c
e
A
n
t
i
b
o
d
i
e
s
a
l
s
o
p
r
o
d
u
c
e
s
a
n
t
i
b
o
d
i
e
s
h
e
l
p
t
o
b
o
o
s
t
i
m
m
u
n
i
t
y
.
It is believed
that
the appendix may have been a major
producer of antibodies at some point
in the
evolutionary
process
T
HE
A
CCESSORY
O
RGANS
:
support the digestive system BUT are not part of the
digestive
tract
These organs secrete fluids
into
the digestive tract, and
are
connect by
ducts.
The accessory organs
include
liver
gall
bladder
pancreas.
1.L
I
VER
largest of these
organs
mass of about 1.5
kg.
liver
produces
bile
b
i
l
e
greenish yellow pigment
made up bile pigments
and
bile
salts
it breaksdown old red
blood
cells.
2.G
ALL
BLADDER
a storage
sac.
The bile is secreted into
it
The
bile
is
stored
here.
HOW IT
WORKS
food containing fat
enters
the digestive
tract
salts are secreted into the
small intestine to digest
fats.
The bile
emulsifies
fats
in
partly digested
food
thereby
assisting
their absorption
3.P
ANCREAS
The pancreas secretes a number of
different
enzymes
into
the
small
intestine
.
Role is to
digest
carbohydrates
lipids
&
proteins
completely.
I
t
a
l
s
o
s
e
c
r
e
t
e
s
b
i
c
a
r
b
o
n
a
t
e
i
o
n
s
R
o
l
e
:
N
eutralize the
HCl
from the stomach
change the pH of the small intestine to
a
pH of
8.
The pancreas will secrete about 1.0 L. of pancreatic fluids
per
day.
The human digestive system is a complex network of organs working together to break down food into smaller molecules for absorption. It consists of major organs like the mouth, esophagus, stomach, small intestine, and large intestine, along with accessory organs such as the liver, gallbladder, and pancreas. Each organ plays a crucial role in the process of digestion, from mechanical breakdown in the mouth to chemical digestion in the stomach. Understanding how these organs function can provide insights into maintaining good digestive health.
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Presentation Transcript
OVERVIEW Major organs Mouth Esophagus Stomach small intestine large intestine Acessory organs: Liver gall bladder Pancreas.
HUMAN DIGESTIVE SYSTEM The process of reducing food into smaller molecules that can be absorbed into the body Digestive system consists of 2 major parts Major organs Mouth Esophagus Stomach small intestine large intestine. Acessory organs: Liver Gall bladder Pancreas.
MAJORORGANS THEMOUTH pH: 7 The first part of the digestive system the entry point of food. Structures in the mouth that aids digestion Teeth cut, tear, crush and grind food. Salivary glands produce and secrete saliva into the oral cavity. saliva moistens the food contains enzymes (ptyalin or salivary amylase) begins digestion of starch into smaller polysaccharides. Function: Mechanical digestion. increasing surface area for faster chemical digestion.
The Esophagus a tube connecting the mouth to thestomach running through the Thoraciccavity. Location: lies behind windpipe (Trachea). o The trachea has as an epiglottis o preventing food from entering the windpipe, o moving the food to the esophagus while swallowing.
Food travels down the esophagus, through a series of involuntary rhythmic contractions (wave-like) called peristalsis. Function: The lining of the esophagus secretes mucus Lubricating to support the movement of food.
ESOPHAGEALSPHINCTER: bolus reachesthe stomach must pass through a muscular ringed valve called the esophageal sphincter (Cardiac Sphincter). Function: prevent stomachacids from back flowing into the esophagus.
STOMACH J-shaped muscular sac Has inner folds (rugae) Increasing surface area of the stomach. Function: Stomach performs mechanical digestion HOW By churning the bolus and mixing it with the gastricjuices secreted by the lining of the stomach. GASTRIC JUICES HCl, salts, enzymes, water and mucus. HCL helps break down of food and kills bacteria thatcame along with the food. The bolus is now called Chyme.
ENZYMES IN STOMACH: Acidic environment HCl secreation kill any microbes that are found in thebolus, creating a pH of 2. Mucus prevents the stomach from digestingitself. Pepsin secreation responsible for initiating the breakdown of proteins (in)food. hydrolyzes proteins to yield polypeptides.
Pyloric sphincter: chyme moves from the stomach to the small intestine. It passes through a muscular ringed sphincter called the pyloric sphincter.
STOMACH DOES NOT DIGEST ITSELF WHY? Protective Mechanism: 3 protective mechanisms. 1. First the stomach only secretes small amounts ofgastric juices until food ispresent. Second the secretion of mucus coats the lining ofthe stomach protecting it from the gastricjuices. The third mechanism is the digestive enzyme pepsinis secreted in an inactive protein called pepsinogen. Pepsinogen is converted to pepsin in the increased presence of hydrochloric acid (pH1). 2. 3.
SMALL INTESTINE Responsible for the complete digestion of all Macromolecules and the absorption of their component molecules E.g Glucose Glycerol Fatty acids Amino acids Nucleotides
PARTS OF SMALL INTESTINE The small intestine is made up of three parts Duodenum Jejunum ileum
1.DUODENUM The first part is the duodenum, u-shaped organ. approximately 30 cm in length. This area completes most of the digestion processes. Enzymes are secreted into the duodenum form the pancreas and the gall bladder. The duodenum is lined by folds of tissue called villi. The villi are covered by fine brush-like microvilli. These folds increase the surface area of the small intestine increase the rate of absorption.
2.JEJUNUM The jejunum is approximately 2.5 m long. Although some digestion is completed here, it has more villi and microvilli; its role is absorption of nutrients. 3.Ileum o The ileum, is approximately 3m long. o has fewer villi and microvilli than the other two parts. o Although absorption also occurs here, it is responsible for pushing the waste materials into the large intestine.
FUNCTIONS OF THE SMALL INTESTINE 90% of the digestion and absorption of food occurs other 10% taking place in the stomach and large intestine. The main function of the small intestine is absorption of nutrients and minerals from food. Digestion of proteins Proteins, peptides and amino acids are acted upon by enzymes such as trypsin and chymotrypsin, secreted by the pancreas. This breaks them down to smaller peptides.
DIGESTION OF LIPIDS Enzymes, like lipases secreted from the pancreas, act on fats and lipids in diet. Lipase can break them into the smaller parts that can enter the intestinal villi for absorption. Digestion of carbohydrates Carbohydrates are broken down to simple sugars and monosaccharides like glucose. Pancreatic amylase breaks down some carbohydrates to oligosaccharides as well. Some carbohydrates and fibers pass undigested to the large intestine where they may, depending on their type, be broken-down by intestinal bacteria.
ABSORPTION IN THE SMALL INTESTINES The nutrients are absorbed by the inner walls of the small intestine into the blood stream. The nutrients are absorbed by processes of simple/passive diffusion, facilitated diffusion, primary active transport, or secondary active transport. For transport, nutrients commonly rely upon Lipids undergo passive or simple diffusion Short-chain fatty acids diffusion Amino acids primary active transport Glucose secondary active transport Fructose facilitated diffusion
ABSORPTION IN THE SMALL INTESTINES Other absorbed substances in the small intestines include: 1.Water 80% is absorbed by the small intestine 10% by the large intestine remaining 10% excreted in the faeces. 2.Electrolytes 3.Vitamins and minerals
LARGE INTESTINE (parts & function )
COMPONENTS OF LARGE INTESTINE The large intestine is composed of several verydistinctive parts: Cecum: Colon:The colon consists of fourparts: Ascending colon Transverse colon Descending colon Sigmoid colon Rectum
CECUM First section of your largeintestine looks like a pouch, two inches long. ROLE Taking in digested liquid from the ileum(small intestine) & passes it on to the colon.
COLON: major section of the large intestine Function: the principal place for water reabsorption, absorbs salts when needed. Components : The colon consists of 4 parts: Ascending colon Transverse colon Descending colon Sigmoid colon
COMPONENTS OF COLON Ascending colon: 1st portion of the colon pushes any undigested debris up from the cecum just under the right lower end of theliver. Transverse colon: 2nd portion of the colon Food traveling from left to right justunder your stomach.
COMPONENTS OF COLON Descending colon: 3rd portion of colon pushes its contents from down to the lower left side of your abdomen Sigmoid colon: final S-shaped length of the colon, empties into the rectum.
RECTUM The final section measures from 1 to 1.6 inches (or 2.5 to 4cm). Leftover waste collects there expanding the rectum emptied through anus
FUNCTION OF LARGE INTESTINE 1. Absorb Water One of the primary functions is to absorbwater prepare the waste as a solid stool that will be expelled from the body. 2. Absorb Vitamin beneficial bacteria role in breaking down undigested sugars and fibers intofatty acids. produce many vitamins, of which are Vitamin K and Biotinthat are absorbed back into the body.
FUNCTION OF LARGE INTESTINE(LI) 3. ReduceAcidity The fatty acids cause acidic environment. The LI produces alkaline solutions reduce the acidity and balance the pH in theLI 4.Protect from Infections The mucous lining of the large intestine acts as aprotective layer prevents harmful bacteria from being reabsorbed intothe body.
FUNCTION OF LARGE INTESTINE(LI) 5. Produce Antibodies also produces antibodies help to boost immunity. It is believed that the appendix may have been a major producer of antibodies at some point in theevolutionary process
THE ACCESSORYORGANS: support the digestive system BUT are not part of thedigestive tract These organs secrete fluids into the digestive tract, andare connect by ducts. The accessory organs include liver gall bladder pancreas.
1.LIVER largest of these organs mass of about 1.5 kg. liver produces bile bile greenish yellow pigment made up bile pigments and bile salts it breaksdown old red blood cells.
2.GALL BLADDER a storage sac. The bile is secreted into it The bile is stored here. HOW IT WORKS food containing fat enters the digestive tract salts are secreted into the small intestine to digest fats. The bile emulsifies fats in partly digested food thereby assisting their absorption
3.PANCREAS The pancreas secretes a number of different enzymes intothe small intestine. Role is to digest carbohydrates lipids & proteins completely. It also secretes bicarbonate ions Role : Neutralize the HCl from the stomach change the pH of the small intestine toa pH of 8. The pancreas will secrete about 1.0 L. of pancreatic fluidsper day.
