Download What is The Digestive System?

The Digestive
System
Najelly Sanchez
Mark Tobello
John Venegas
Eliab Hernandez
Per. 1
Parts and
Organs of
The
Digestive
System
What is The Digestive
System?

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The digestive system is a series of hollow organs
joined in a long, twisting tube from the mouth to
the anus. Inside this tube is a lining called the
mucosa. In the mouth, stomach, and small
intestine, the mucosa contains tiny glands that
produce juices to help digest food.
Two solid organs, the liver and the pancreas,
produce digestive juices that reach the intestine
through small tubes. In addition, parts of other
organ systems (for instance, nerves and blood)
play a major role in the digestive system.
Why is digestion important?

When we eat such things as bread, meat,
and vegetables, they are not in a form that
the body can use as nourishment. Our food
and drink must be changed into smaller
molecules of nutrients before they can be
absorbed into the blood and carried to cells
throughout the body. Digestion is the process
by which food and drink are broken down
into their smallest parts so that the body can
use them to build and nourish cells and to
provide energy.
How is food digested?

Digestion involves the mixing of food, its
movement through the digestive tract,
and chemical breakdown of the large
molecules of food into smaller molecules.
Digestion begins in the mouth, when we
chew and swallow, and is completed in
the small intestine. The chemical process
varies somewhat for different kinds of
food.
The Mouth

Mastication, or the chewing
of food in the mouth, is the
first step of digestion. Saliva
initiates digestion and
changes the chewed food
into a soft mass, or bolus.
Saliva makes the bolus
slippery, making it easier to
be swallowed and slide down
the back of the throat and
esophagus. The bolus passes
through the esophageal
sphincter before it enters the
stomach.
The Oral Cavity and Its Functions:
Mechanical
Processing
 Moistening
 Mixing with
salivary
secretions

What is the purpose of Oral
Cavity?
Analyzes and senses material before
swallowing
 Processes material through the actions of
the teeth, tongue, and surfaces of the
palate(roof the Oral Cavity)
 Lubricates material by mixing it with
mucus and salivary secretions
 Begins the digestion of carbohydrates and
lipids with salivary enzymes

Your Teeth

They help
in chewing
and
breaking
down the
food
The Tongue
The tongue is mainly
composed of muscles. It is
covered with a mucous
membrane. Small nodules
of tissue (papillae) cover
the upper surface of the
tongue. Between the
papillae are the taste buds,
which provide the sense of
taste. In addition to taste,
the tongue functions in
moving food to aid chewing
and swallowing, and it is
important in speech.
Your Tongue

It manipulates materials inside the mouth
to bring food into the oral cavity.
Functions of the Tongue:
Processes by compressing and distorting
2. Manipulates to assist in chewing and to
prepare the material for swallowing
3. Analyzes material by touch,
temperature, and taste receptors
1.
Where are your Salivary Glands?
The glands are found in
and around your mouth
and throat. We call the
major salivary glands
the parotid,
submandibular, and
sublingual glands.
They all secrete saliva
into your mouth, the
parotid through tubes
that drain saliva, called
salivary ducts, near your
upper teeth,
submandibular under
your tongue, and the
sublingual through
many ducts in the floor
of your mouth.
The Pharynx

Serves as a
passageway for
solid food, liguids,
and air.
Movement of Food Through the
System


The large, hollow organs of the digestive system contain
muscle that enables their walls to move. The movement of
organ walls can propel food and liquid and also can mix the
contents within each organ. Typical movement of the
esophagus, stomach, and intestine is called peristalsis. The
action of peristalsis looks like an ocean wave moving
through the muscle. The muscle of the organ produces a
narrowing and then propels the narrowed portion slowly
down the length of the organ. These waves of narrowing
push the food and fluid in front of them through each
hollow organ.
The first major muscle movement occurs when food or
liquid is swallowed. Although we are able to start
swallowing by choice, once the swallow begins, it becomes
involuntary and proceeds under the control of the nerves.
The Esophagus

The esophagus is the organ
into which the swallowed
food is pushed. It connects
the throat above with the
stomach below. At the
junction of the esophagus
and stomach, there is a
ringlike valve closing the
passage between the two
organs. However, as the
food approaches the closed
ring, the surrounding
muscles relax and allow the
food to pass.
The Stomach

The food then enters the
stomach, which has three
mechanical tasks to do. First,
the stomach must store the
swallowed food and liquid. This
requires the muscle of the
upper part of the stomach to
relax and accept large volumes
of swallowed material. The
second job is to mix up the
food, liquid, and digestive juice
produced by the stomach. The
lower part of the stomach
mixes these materials by its
muscle action. The third task of
the stomach is to empty its
contents slowly into the small
intestine.
The Stomach cont.

Several factors affect emptying of the
stomach, including the nature of the food
(mainly its fat and protein content) and the
degree of muscle action of the emptying
stomach and the next organ to receive the
contents (the small intestine). As the food is
digested in the small intestine and dissolved
into the juices from the pancreas, liver, and
intestine, the contents of the intestine are
mixed and pushed forward to allow further
digestion.
Duodenum

Located at the
junction of the
stomach and the
small intestine, the
duodenum is the
first part of the
small intestine. It is
C-shaped and
about 25 cm long.
What does the duodenum do?

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The duodenum receives the thick liquid mixture of partlydigested food and acid from the stomach. This acid is
quickly neutralised in the alkaline environment of the
duodenum.
The duodenum also receives bile from the gallbladder, and
other digestive enzymes from the pancreas. These enter
the duodenum through small ducts or tubes.
Other glands produce mucus that coats the digestive
mixture to help ease its passage.
The food mixes with bile, mucus, and pancreatic and other
digestive enzymes.
The bulk of the digestion of proteins, fats and
carbohydrates takes place in the duodenum before the
material travels further into the small intestine.
Jejunum and Ileum

The jejunum is the 12 m long, coiled midsection of the small
intestine. The ileum is
the final portion of the
small intestine, which
leads into the large
intestine. The ileum
measures 2-4 m in
length.
The role of the jejunum and ileum
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The inner linings of the jejunum and ileum contain very small finger-like
bumps called 'villi'. The presence of these tiny bumps on the inside of the
small intestine means that the surface area is much larger than if the
lining were just a flat surface. This increased surface area improves the
small intestine's ability to absorb nutrients.
The final stages of digestion are completed in this portion of the small
intestine, where foods and liquids are fully broken down into their nutrient
components such as:
smaller molecules (eg, glucose from carbohydrates; amino acids from
proteins; fatty acids and cholesterol from fats)
vitamins
minerals
salts
water
As the digestive mixture travels through the small intestine, the villi
absorb the nutrients and transfer them to the bloodstream and the liver.
Any food that has not been digested in the small intestine, ie fibre
(along with some water and vitamins) then reaches the large intestine.
Liver

The liver is a very
large organ
weighing up to 3
kg in adult
humans.
What does the liver do?


The liver produces bile, a substance that
helps to break down fats. Bile produced in
the liver is transferred to the gallbladder
where it is stored until needed for digestion.
Once food, medicines, liquids, etc that you
consume are digested in the small intestine
and absorbed by the walls of the small
intestine, these products of digestion
(nutrients and other molecules) are then
transferred to the liver for further processing.
Gallbladder

The gallbladder is
a small (10 cm
long) pear-shaped
organ that is
located near the
duodenum and the
liver. The
gallbladder is
connected to the
liver and the
duodenum through
small tubes.
Where is the gallbladder and what
does it do?


The gallbladder's main function is to store bile, a
dark green digestive liquid produced by the liver.
Bile is a substance that helps to break down fats.
When stored in the gallbladder, bile becomes
more concentrated and therefore more powerful
in its ability to do its work.
When foods containing fats arrive in the small
intestine, the gallbladder releases the stored bile
into the duodenum. Here the bile helps to break
down fats and also neutralize acids in the food
that has arrived from the stomach.
Disorders/problems of the
gallbladder
Gall Stones
 Cholecystitis
 Gallbladder cancer

Pancreas

The pancreas is a
small flat organ
(about 18-25 cm
long) that is located
behind the stomach
and sits close to the
duodenum. It is
connected to the
duodenum via a
tube called the
pancreatic duct.
The pancreas has two main
functions
It is the source of powerful digestive
enzymes required to chemically break
down fats, carbohydrates and proteins.
The pancreas also secrete another
substance to help neutralize stomach
acid
2. The hormone insulin is made by the
pancreas - insulin helps to balance blood
sugar levels in the body
1.
Pancreas cont.
When food reaches the lower stomach and then the
duodenum, these organs give off signals to the
pancreas telling it to secrete its many digestive
enzymes. These enzymes and other substances are
produced within the pancreas and then transferred to
the duodenum where they neutralize acid and break
down fats, carbohydrates and proteins into smaller
molecules (nutrients) that can be used by the body.
Problems of the pancreas
 In some people, the pancreas may become inflamed,
giving rise to a condition known as 'Pancreatitis'.

The Small Intestine

The liquefied bolus, now called
chyme, then passes through the
pyloric sphincter and enters the
duodenum, the first section of the
small intestine. It is here that
enzymes released from the pancreas,
liver, and gallbladder further
breakdown chyme into elements that
can be easily absorbed and used by
the body. The small intestine is lined
with a heavily folded inner mucosa
and small fingerlike projections
called villi. The villi enable digested
food to enter the bloodstream. It is
here, in the small intestine, where all
nutrients and vitamins are absorbed.
The Small Intestine cont.

Finally, all of the digested nutrients are
absorbed through the intestinal walls. The
waste products of this process include
undigested parts of the food, known as
fiber, and older cells that have been shed
from the mucosa. These materials are
propelled into the colon, where they
remain, usually for a day or two, until the
feces are expelled by a bowel movement.
Problems/disorders of the small
intestine

There are a number of things that can go
wrong in the small intestine. Information
leaflets on some of these conditions are

Coeliac disease
Peptic ulcers
Infections of the digestive tract
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The Large intestine

Chyme can travel through
up to 20 feet of small
intestine before it passes
through the ileocecal valve
to enter the large intestine.
Very little digestion occurs
in the large intestine.
Undigested chyme that
enters the large intestine is
considered waste. The
waste becomes more and
more solid as it passes
through the large intestine
because water is
continuously being
reabsorbed from the waste.
Caecum

The caecum is the
first part of the large
intestine. Shaped like
a small pouch and
located in the right
lower abdomen, it is
the connection
between the small
intestine and the
colon.
What does the caecum do?
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The caecum accepts and stores processed
material from the small intestine and moves
it towards the colon. As the processed food
approaches the end of the small intestine, a
valve separating the small and large
intestines opens, the caecum expands and
the material enters. At this stage, the
mixture normally contains:
undigested food (fibre)
a little bit of water
some vitamins
some minerals or salts
Appendix
The appendix is a small
projection emerging
from the caecum.
 In human beings, the
appendix has no known
function and is thought
to be a remnant from a
previous time in human
evolution.
 In some people, the
appendix becomes
infected or inflamed (a
condition known as
'appendicitis'), and the
appendix needs to be
removed (via surgery).

Appendicitis
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Appendicitis is a painful swelling and infection of the appendix.
The Appendix is attached to the large intestine and located in the lower right area of the abdomen.
Scientists are not sure what the appendix does, if anything, but removing it does not appear to
affect a person’s health.
What causes Appendicitis.
trauma to the abdomen
eces, parasites, or growths that clog the appendiceal lumen
enlarged lymph tissue in the wall of the appendix, caused by infection in the gastrointestinal tract
or elsewhere in the body

The symptoms are:

Trouble moving around due to agonizing pain
Pain gets worse within hours
pain start at the belly button and moves to the bottom right
Vomiting
loss of appetite
constipation or diarrhea.
and inability to pass gas.
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Colon

Shaped like an
inverted 'U', the
colon is the
longest part of the
large intestine.
Where is the colon?
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The colon has four sections that are located in the
abdominal cavity.
Ascending colon - starts at the caecum at the bottom
right hand side of the abdomen and ascends (ie, goes
upwards) towards the liver.
Transverse colon - transverse means 'across'. This
part of the colon extends across the abdomen from
right to left.
Descending colon - descends (goes downwards) on
the left hand side of the abdomen.
Sigmoid colon - it is the last part of the large
intestine, and is located on the bottom left hand side
of the abdomen. It is the S-shaped connection
between the descending colon and the rectum.
What does the colon do?
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Within the colon, the mixture of fibre, small amounts of
water, and vitamins, etc, mixes with mucus and with
bacteria that live in the large intestine - and starts to form
faeces.
As faeces travels through the colon, the lining of the colon
absorbs most of the water and some vitamins and
minerals.
The bacteria in the colon chemically break down some of
the fibre to produce nutrients for their own survival and to
nourish the cells lining the colon. Thus, the fibre in your
diet is extremely important to maintain the long-term
health of the colon.
Through muscular movements of the colon, faeces is
pushed along until finally, the walls of the sigmoid colon
contract, causing the faeces to move into the rectum.
The Rectum

Waste collects in the
rectum, or end of
the large intestine,
until the brain
signals for it to be
expelled from the
body.
Interesting facts
The esophagus is approximately 25cm long. Muscles contract in waves to move
the food down the esophagus. This means that food would get to a person's
stomach, even if they were standing on their head.
 "Gas is basically produced by foods that have indigestible or
excess carbohydrates, which are not absorbed when they get to the
colon, explains Van Thiel. "Beans, for example, have complex
carbohydrates that are maldigested. And the same holds true for
mushrooms. Many people don't realize that mushrooms contain a
unique sugar called raffinose, which humans can't break down.
Cabbages and onions do the same thing." As a group, vegetarians
produce more gas than meat-eaters because the intestinal enzymes
can't digest the cellulose in vegetables' cell walls. However,
the colon's bacteria relish the stuff. The outcome: When a group
of young men, in the service of science, feasted on a diet rich
in pork and beans, their flatus elimination increased from 15 ml
to 176 ml per hour!
 The average male will eat about 50 tons of food during his lifetime in order to
sustain a weight of 150 pounds.
 The liver performs more than 500 functions.

Any
Questions?