Download The Digestive System 2012 new notes

 http://www.youtube.com/watch?v=N2diPZ
Otty0

Recap of supersize me
http://www.oprah.com/health/Inside-Dr-OzsDigestive-System-Video
Flashcard Warm-up May 22nd
Peristalsis
 Define
and Draw a picture
Flashcard Warm-up Jan. 2nd
The Digestive System

Anatomy of the Digestive
System
A.
B.
The organs of the digestive system
can be separated into two main
groups: the alimentary canal (also
called the gastrointestinal tract)
and the accessory digestive
organs.
The alimentary canal consists of
the following organs: Mouth,
Pharynx, Esophagus, Stomach,
Small intestine, Large intestine,
and Anus
Digestive System
II. Overview of Gastrointestinal Processes
A.
Ingestion- putting the food into your mouth! Then,
mechanical digestion and chemical digestion
begins.

Food Propulsion- The processes that
move food to the next digestive
organ.
 This includes swallowing, peristalsis
and segmentation.
Howstuffworks "Peristalsis"
 Peristalsis- involuntary alternating
contraction and relaxation of muscles to
squeeze the food through the digestive
tract.
 Segmentation- single segments of the
intestine alternately contract and relax.
Because active segments are separated
the food is moved forward and then
backward. This mixes the food rather
than simply propelling through the tract.
Digestive Process
 Food

Breakdown:
Mechanical digestion is mixing of food in the
mouth by the tongue, churning of food in the
stomach, and segmentation in the small
intestine. This prepares the food for chemical
digestion.
Chemical Digestion- Enzymes break down food
products into their building blocks. Enzymes are
located in saliva, stomach, and the
pancreas
releases enzymes into the intestines that help break
down the food. The pancreas enzymes are totally
responsible for fat digestion with the enzyme lipase.
Carbohydrates are broken into monosaccharides
(simple sugars) by amylase and maltase.



2. Proteins are broken down into amino acids
by PEPSIN and TRYPSIN.
3. Lipids are broken down into fatty acids and
glycerol by LIPASE
Omega-3 fatty acids have been found to be beneficial for
the heart. Positive effects include anti-inflammatory and
anti-blood clotting actions, lowering cholesterol and
triglyceride levels, and reducing blood pressure. These
fatty acids may also reduce the risks and symptoms for
other disorders including diabetes, stroke, rheumatoid
arthritis, asthma, inflammatory bowel disease, ulcerative
colitis, some cancers, and mental decline.

Absorption- The small intestine
is the main site where food is
absorbed into the blood or
lymph. The villi play a huge
role in the absorption of food.

Defecation- The elimination of
indigestible substances from
the body. This is the job of the
large intestines. The “residue”
spends about 12 to 14 hours in
the large intestine as bacteria
work to metabolize some of the
remaining nutrients, releasing
gases that contribute to the
odor of feces. You produce
about 500 mL of gas per day!
Organs of the Digestive system
Accessory digestive organs include the salivary
glands, teeth, pancreas, liver and gallbladder.


Salivary glands- contain an
enzyme, salivary amylase that
begins the process of starch
digestion. The saliva also
helps bind food together into a
mass called a bolus which
makes chewing and
swallowing easier.
Teeth- aid in mastication, or
chewing. This tears and
grinds the food breaking it
down into smaller pieces.

Pancreas- produces a
wide variety of enzymes
to help break down food.
The enzymes are
secreted into the
duodenum in an alkaline
fluid, which neutralizes
the acidic chyme coming
in from the stomach. The
pancreas also produces
the hormones insulin and
glucagon.


Liver- The largest organ in your body!! It
is located under the diaphragm more to
the right side of the body. The liver is
connected to the gall bladder via the
common hepatic duct. The liver has over
500 known functions!!! Three three
important functions are to produce bile,
clean your blood, and stores energy in the
form of a sugar called glycogen.
Bile is a yellow to green watery solution
that contains bile salts, bile pigments
(bilirubin a breakdown product of
hemoglobin), cholesterol, phospholipids,
and a variety of electrolytes. The bile
salts help to emulsify fats by physically
breaking large fat globules into smaller
ones.

Gall Bladder- a thin-walled
green sac that sits in the
inferior surface of the liver.
When food digestion is not
occurring bile backs up in
the cystic duct and enters
the gall bladder where it is
stored. If bile is stored for
too long or too much water
is removed, the cholesterol
it contains crystallize to
form gallstones
The Alimentary Canal

• Mouth- where the food enters the
body. The hard palate forms the
anterior roof, while the soft palate
forms the posterior roof of the mouth.
Swallowing or deglutition is completed
by the muscular tongue.
Mechanical digestion and chemical
digestion begins. Once food is placed in
the mouth the physical breakdown begins
by chewing. Salivary amylase starts the
chemical breakdown of starches and to
moisten the food to make swallowing and
digestion an easier process. No food
absorption occurs in the mouth.
• Pharynx- serves as
passageway for food and air.
Food movement is by
alternating contractions of
the muscle layers
(peristalsis).

The epiglottis closes off the trachea
to ensure we do not choke on our
food.
• Esophagus- the passageway for
food only that runs from pharynx
to stomach through the
diaphragm

Conducts food by peristalsis (slow
rhythmic squeezing)- involuntary
alternating contraction and
relaxation of muscles to squeeze the
food through the digestive tract
4) Stomach- located on the left side
of the abdominal cavity. Acts
as a storage tank for food, a
site of food breakdown,
chemical breakdown of protein
begins, delivers chyme
(processed food) to the small
intestine.

The internal folds of the
stomach mucosa are called
rugae this allows for
expansion of the stomach.
 Food
enters at the cardioesophageal
sphincter then enters regions of the
stomach. Food empties into the small
intestine at the pyloric sphincter.

As the food enters the
stomach the walls begins to
stretch and the secretion of
gastric juices begins. In
addition, the presence of food
and falling pH levels in the
stomach stimulate the
stomach cells to secrete the
hormone gastrin, prodding the
stomach to produce more of
the protein-digesting enzymes,
mucus and hydrochloric acid.
2 to 3 liters of gastric juice are
secreted everyday.

Occasionally the
cardioesophageal sphincter fails
to close tightly and gastric juice
backs up in the esophagus.
This is commonly called
heartburn. If the acids in the
stomach begin digesting the
stomach itself this is called a
peptic ulcer. Helicobacter pylori
(H. pylori) is a bacteria that is
the major cause of peptic ulcers.
Excessive use of NSAIDs—such
as aspirin and ibuprofen—is
another common cause.


The stomach works to compress
and pummel the food breaking it
apart physically. The chemical
digestion of proteins also begins
in the stomach using enzymes
called pepsin.
Once the food is well mixed a
rippling peristalsis begins in the
lower half of the stomach. The
pylorus holds about 30 mL of
chyme, and each contraction
squirts only 3 mL through the
pyloric sphincter into the small
intestine. The emptying of the
stomach takes about 4 hours
after a well-balanced meal, and 6
after a high fat meal to empty.
5) Small Intestine- The body’s major
digestive organ, because nearly all
nutrient absorption from food occurs in
the small intestine. This muscular tube
can extend 6-13 feet in a living person.
There are three subdivision of the small
intestine:

Duodenum- Attached to the stomach
and curves around the head of the
pancreas

Jejunum- attaches anteriorly to the
duodenum

Ileum- extends from jejenum to the
large intestine
.


Once food reaches the small
intestine it is only partially digested.
Carbohydrate and protein digestion
has begun but no fat has been
digested at this point. The journey
through the small intestine will take
about 3 to 6 hours to complete.
Food will be moved through the
small intestine using peristaltic
contractions and segmented
movements to mix the chyme and
propel through.
The microvilli of the small intestine
have important enzymes, known as
brush border enzymes that break
down double sugars into simple
sugars and complete protein
digestion.

Pancreatic juices are also enzyme
rich and delivered to the small
intestine to complete the digestion of
starch, protein, and are totally
responsible for fat digestion using
lipases, and digest nucleic acids.
The pancreatic juice also contains
bicarbonate which neutralizes the
acidity of the chyme.

The two hormones that regulate the
release of pancreatic juice into the
small intestine are secretin and
cholecystokinin.


Bile also plays a role in fat
digestion but is not an enzyme.
It acts to emulsify or help break
down large fat globules.

The small intestine also
contains absorptive cells called
villi. These are fingerlike
projections that has a rich
capillary bed where the
digested foodstuffs are
absorbed.

At the end of the ileum all that
remains is the indigestible food
materials and large amounts of
bacteria.

6) Large Intestine- Larger in diameter, but
shorter than the small intestine this
tube extends only 5 feet. Its major
functions are to dry out the indigestible
food residue by absorbing water and to
eliminate these residues from the body
as feces. Structures of the large
intestine include:
a)
Cecum – saclike first part of the
large intestine
b)
Appendix- Accumulation of
lymphatic tissue that sometimes
becomes inflamed (appendicitis)
and hangs from the cecum
a)
Colon- includes the
ascending, transverse,
descending and sigmoid
regions.
b)
Rectum and the anal
canal (external opening)



Peristalsis and mass movements (slow-moving powerful
contractile waves that move over the colon three to four
times a day) are the two propulsive movements
occurring in the large intestine. Bulk, or fiber, increases
the strength of colon contractions softening the stool and
allowing the colon to function properly.
Watery stools or diarrhea results when food passes
through the large intestine before water can be
absorbed. If food remains in the large intestine for
extended periods too much water is absorbed and the
stool becomes difficult to pass. This is called
constipation, usually due to low fiber diets, “failing to
heed the call”, and laxative abuse.
More than 500 vital functions have been identified with the
liver. Some of the more well-known functions include the
following:
•Production of bile, which helps carry away waste and break down fats in the small
intestine during digestion
•Production of certain proteins for blood plasma
•Production of cholesterol and special proteins to help carry fats through the body
•Conversion of excess glucose into glycogen for storage (glycogen can later be
converted back to glucose for energy)
•Regulation of blood levels of amino acids, which form the building blocks of
proteins
•Processing of hemoglobin for use of its iron content (the liver stores iron)
•Conversion of poisonous ammonia to urea (urea is an end product of protein
metabolism and is excreted in the urine)
•Clearing the blood of drugs and other poisonous substances
•Regulating blood clotting
•Resisting infections by producing immune factors and removing bacteria from the
bloodstream
Discovery education Video
 Digestion
is the process of breaking down
food into a form that can be used by the
body’s tissues. Explain the functions of
each part of the digestive system.
 • What is the role of each part in aiding
digestion?
 • Why is digestion described as both a
mechanical and a chemical process?
Digestive System Poster
 Follow
directions on 14 A, labels for
structures are on 14B
 ADD to your poster the FUNCTION of
each labeled part
 LABEL visible structures of each organ:
example- small intestines should have
duodenum, jejunum, and ileum labeled
 Complete questions on 14 C and D if time,
you will have SOME time tomorrow to
complete these
Flashcard Warm-up May 23rd
 CHEMICAL
DIGESTION
 List
the enzymes discussed in yesterday’s
notes


Amylase, maltase, pepsin, trypsin, lipase
Indicate what macromolecule they break
down and WHERE this digestion takes place
in the body.
III. Activities occurring through the digestive tract
Digestion animation
A.
Activities occurring in the mouth, Pharynx, and
esophagus
1. Once food is placed in the mouth the physical
breakdown begins by chewing. Salivary amylase also
contributes to the breakdown of starches and to moisten
the food to make swallowing and digestion an easier
process.
2. Swallowing or deglutition is aided by the tongue,
soft palate, pharynx and esophagus. Once the bolus is
forced into the pharynx by the tongue we no longer have
conscious control and are into the realm of our reflex
activity.
3. The epiglottis closes off the trachea to ensure we
do not choke on our food.
4. Food is moved down through the esophagus
through peristaltic contractions.