Download Digestive System

Digestive System
Chapter 11 Unit 10
Digestive System
• The digestive system is the group of organs that changes
food into a form that can be used by the body’s cells
• The system is also known as the gastrointestinal(GI) tract or
system
• The digestive process can be divided into four phases:
• 1. Ingestion: food is taken in
• 2. Digestion: preformed by all the organs of the digestive
tract
• 3. Absorption: by the small intestines
• 4. Elimination: by the large intestines, colon, and rectum
Digestive System
• The main organs of the
system are those through
which the food passes
• These organs form a
continuous tube from the
entrance to the exit of the
body
• They are the mouth,
pharynx, esophagus,
stomach, small intestine,
and large intestine
The Mouth
• Food enters the body
through the mouth
• Teeth break up food into
small pieces to make it
easier to swallow and also
to prepare it for more
effective action by
digestive enzymes
• The tongue contains taste
buds and papillae
projections
The Mouth
• The salivary glands
excrete the fluid known
as saliva
• It is released from three
pairs of glands: the
parotid, the
submandibular, and the
sublingual
• Certain foods cause the
glands to secret profusely
often producing some
discomfort, as when
eating something sour
The Esophagus
• Once food is swallowed, its
movement through the
body is maintained by the
smooth, involuntary
muscles called peristalsis
• When food enters the
esophagus, the muscles
alternately contract and
relax, squeezing the bolus(is
a mass of food that has
been chewed at the point of
swallowing)
• This moves the bolus to the
stomach(only takes 5
seconds)
The Stomach
• The upper opening to the
stomach is controlled by a
circular muscle called the
cardiac sphincter
• As the peristaltic wave
approaches, the sphincter
dilates, allowing the food
to enter
• Once the food is inside,
the one-way “gate” closes
to prevent its escape
•
•
•
•
•
•
•
•
•
•
•
The
Stomach
The stomach is a 10-inch-long, J shaped organ constructed of three layers of strong
muscle tissue
It lies just beneath the diaphragm
It can hold about half a gallon of food and liquid
The stomach continues the digestive process that began in the mouth
The stomach lining is formed of mucous membrane, whose glands secret mucus
The stomach has 35 million gastric glands, which secretes mostly hydrochloric
acids(page 508 lists more enzymes)
Hydrochloric acid can burn holes in things, and can destroy the stomach lining and
cause ulcers
An ulcer in the stomach is called a gastric or peptic ulcer
The partially digested food in the stomach is changed
into a semi-liquid state called chyme in 3 to 5 hours
Liquids will pass through the stomach in minutes
When the consistency of the chyme is right, the
pyloric sphincter, at the end of the stomach,
allows the chyme to spurt through the sphincter
into the small intestine
The Stomach
• Because of the two sphincters, food is held in the
stomach until it is properly prepared to leave
• But occasionally, when you suffer from nausea
and vomiting, it is obvious the material did not go
in the right direction
• This action is accomplished by the contraction of
the abdominal muscles, forcefully squeezing the
stomach as it is pushed downward by the
diaphragm
• With this pressure and reverse peristaltic waves,
the contents of the stomach are forced out and
emesis(vomiting) occurs
The Small Intestine
• The small intestine is a tube
about 1 inch in diameter
and about 20 feet in length
• It completes the digestive
process and absorbs the
nutrients from the chyme
• The small intestine is
divided into three sections
• The first is a C-shaped
segment, about 9 inches
long, called the duodenum
• The next is the jejunum,
and is about 8 feet in length
• The last segment, about 12
feet long, is called the ileum
Small Intestine
• The ileum is reduced to
about half an inch in
diameter by the time it
joins the large intestine in
the right lower quadrant
of the abdomen
• The small intestine
completes the digestive
process with the aid of
accessory organs and
sections by the glands of
the small intestine
The Liver
• The liver is the largest gland in
the body
• Its lies below diaphragm in the
upper right quadrant of the
abdomen extending into the
upper left quadrant
• The liver is a vital organ, that
performs several functions
• The liver secretes bile(water
and pigments of rbc’s), this
gives fecal material its yellowbrown color
• The iron from destroyed cells
in the liver are reabsorbed into
the body
The Liver
• The liver also stores
glycogen, needed for
blood sugar
• Toxins (poisons) are
pulled from the blood
by the liver where for
the most part are
rendered harmless
• The liver is a storage for
area for blood and
bodily fluids because of
its large size
The Gallbladder
• The gallbladder is a small sac
attached to the underside of
the liver(right side)
• Its sole purpose is the
concentration and storage of
bile
• When the body needs bile to
digest food, the gallbladder
releases bile to supplement
that being produced by the
liver
• The common duct of the
gallbladder empties the bile
into the duodenum
The Gallbladder
• Obstruction of the bile ducts
from gallstones in the
gallbladder is not uncommon
• Frequently the stones will be
expelled into the duct where
they become logged, causing
pain and inadequate supply of
bile and requiring surgical
removal
• Medical term for gallstones is
cholelithiasis(coliolathysis)
• All stones are of mixed content
to some extent. Those
classified as mixed, however,
contain between 30% and 70%
of cholesterol. In most cases
the other majority constituent
is calcium salts.
The Pancreas
• The pancreas lies behind
the stomach, with the head
in curve of the duodenum
• If pancreatic juices are
absent, serious digestive
problems occur
• The pancreas secretes
directly into the
bloodstream a substance
called insulin
• After you eat a meal, any
carbohydrates you’ve eaten
are broken down into
glucose and passed into the
bloodstream
• The pancreas detects this
rise in blood glucose and
starts to secrete insulin.
The Absorption Function
• When all the digestive juices and enzymes
have been added and the chyme passes into
the jejunum, digestion has progressed to the
point where absorption of some nutrients and
other substances can begin
Duodenum
• It should be clear now why the duodenum is
such a critical segment of the digestive tract,
because it receives products from four
organs- the stomach, liver, gallbladder, and
pancreas
• Any ulceration or tumors may interfere
drastically with the digestive system and is a
cause for concern
The Large
Intestine
• With digestion completed
and the useful nutrients and
other substances absorbed
from the chyme, the waste
products, and the excess
water are sent into the large
intestine
• The large intestine is about
5 feet and approximately 2
inches in diameter
• The colon as it is also called,
frames the abdomen
The Large Intestine
• The large intestine absorbs the liquid from the
chyme
• Some salts and proteins, are later filtered by
the kidneys to be eliminated in the urine
• The remaining fibrous waste materials are
formed into feces to be eliminated through
the rectum
The Appendix
• The appendix is a wormshaped structure about the
size of the little finger
• It tends to become filed easily
but drains rather slowly
• Occasionally, a
substance(stool)causes
irritation to the lining,
resulting in a painful,
inflammatory process known
as appendicitis
• Appendicitis is a medical
emergency that requires
prompt surgery to remove the
appendix. Left untreated, an
inflamed appendix will
eventually burst, or perforate,
spilling infectious materials
into the abdominal cavity
The Ascending, Transverse,
And Descending Colon
• The large intestine is
divided into ascending,
transverse, and descending
sections as a means of
identification
• The first part of large bowel
is the right colon or
otherwise known as the
ascending colon(leading
upward)
• Smallest of the colon
• In the ascending bowel, the
liquid stool is acted upon by
bacteria(gut flora)
The Ascending, Transverse, And
Descending Colon
• The transverse colon begins
at the hepatic flexure and
extends in a loop across the
abdominal cavity to the
point below the spleen
• This is the longest and most
movable part of the colon
• Cancers form more
frequently here, as the
contents become more solid
(water is removed) in order
to form feces
The Ascending, Transverse, And
Descending Colon
• The descending section
extends downward along
the left side of the
abdomen until it reaches
the edge of the pelvic
cavity
• It is firmly anchored to
the abdominal wall to
maintain its position
• The function of the
descending colon is to
store food that will be
emptied into the rectum.
The Sigmoid, Rectum, And Anal Canal
• After the large intestine enters
the pelvic cavity, it makes two
bends suggestive of an S and is
therefore labeled the sigmoid
section of the colon
• This extends from the left iliac
crest over the back to join the
rectum
• The rectum serves as a
collecting area for the remains
of digestion, and is 6 to 8
inches long
• When enough material is
accumulated, sensors are
activated, and the urge to
defecate is felt
The Sigmoid, Rectum, And Anal Canal
• The anal canal is a
narrow passageway
about an inch long,
extending from the
rectum to the anus
(opening from the
body)
Diagnostic
Examinations
• Colonoscopy: is
the endoscopic examination
of the large bowel and
the distal part of the small
bowel with a fiber
optic camera on a flexible
tube passed through
the anus.
• It may provide a visual
diagnosis
(ulceration, polyps) and
grants the opportunity
for biopsy or removal of
suspected lesions.
Diagnostic
Examinations
• Barium swallow: is a test
that may be used to
determine the cause of
painful
swallowing, difficulty with
swallowing, abdominal pain
bloodstained vomit or
unexplained weight loss
• Compound that shows up
on x-ray and is used to help
see abnormalities in
the esophagus and stomach
Diagnostic
Examinations
•
•
•
•
Esophagogastroduodeoscopy
(EGD): is an examination of the lining
of the esophagus, stomach, and upper
duodenum with a small camera
(flexible endoscope) which is inserted
down the throat
The endoscope is advanced through
the esophagus (food pipe) to the
stomach and duodenum
Air is introduced through the
endoscope to enhance viewing
The lining of the esophagus, stomach,
and upper duodenum is examined,
and biopsies can be taken through the
endoscope
Biopsies are tissue samples that are
reviewed under the microscope
Diseases And
Disorders
• Appendicitis: is swelling
(inflammation) of the
appendix.
• Appendicitis is one of the most
common causes of emergency
abdominal surgery
• It usually occurs when the
appendix becomes blocked by
feces, a foreign object(tumor)
• Colitis: is swelling
(inflammation) of the large
intestine (colon)
• Symptoms can include:
abdominal pain and bloating
bloody stools; or dehydration
Diseases And
Disorders
• Cirrhosis: is scarring of
the liver and poor liver
function. It is the final
phase of chronic liver
disease.
• Symptoms may develop
gradually, or there may
be no symptoms
(hepatitis or alcohol)
Diseases And Disorders
• Colostomy: is a surgical
procedure in which
a stoma is formed by
drawing the healthy end
of the large intestine or
colon through
an incision in
the anterior abdominal
wall and suturing it into
place
Diseases And Disorders
• Crohn’s disease: is a type
of inflammatory bowel
disease that may affect
any part of the
gastrointestinal tract
from mouth to anus,
causing a wide variety
of symptoms
• It primarily
causes abdominal pain,
diarrhea, vomiting
or weight loss
Diseases And
Disorders
• Diverticulitis: is the condition
of having diverticula in
the colon, which are
outpocketings of the
colonic mucosa and
submucosa through
weaknesses of muscle layers in
the colon wall
• Without fiber to add bulk to
the stool, the colon has to
work harder than normal to
push the stool forward. The
pressure from this may cause
pouches to form in weak spots
along the colon.
Diseases And Disorders
• Gastroesophageal reflux
disease(GERD): is a
condition in which the
stomach contents (food
or liquid) leak backwards
from the stomach into
the esophagus
• This action can irritate the
esophagus, causing
heartburn and other
symptoms.
Diseases And
Disorders
• Hemorrhoids: are painful,
swollen veins in the lower
portion of the rectum or
anus
• Hernia: a sac formed by
the lining of the
abdominal cavity
(peritoneum)
• The sac comes through a
hole or weak area in the
fascia, the strong layer of
the abdominal wall that
surrounds the muscle.
Diseases And
Disorders
• Irritable Bowel
Syndrome(IBS): is a disorder
that leads to abdominal pain
and cramping, changes
in bowel movements, and
other symptoms
• In IBS, the structure of the
bowel is not abnormal(not like
chron’s dx)
• Peptic ulcer: is a defect in the
lining of the stomach or the
first part of the small intestine,
an area called the duodenum
• Caused by alcohol, smoking, or
regular use of aspirin or
ibuprofen