Transcript The digestive system

The digestive system
Digestive system
Digestion takes place within a tube called
the digestive tract, which begins with
the mouth and ends with the anus.
Functions of the digestive system:
1. Ingest food
2. Digest it to nutrients that can cross
plasma membrane.
3. Absorb nutrients
4. Eliminate indigestible remains.
Swallowing
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It occurs in the pharynx which receives food from the
mouth and air from the nasal cavity.
Swallowing is reflex action performed automatically
without conscious thought.
During swallowing the soft palate moves back to
close off the nasopharynx and the trachea moves
up under the epiglottis to cover the glottis. The
glottis is the opening to the larynx (voice box).
During swallowing, food normally enters the
esophagus because the air passages are blocked.
Some times food goes the wrong way either into the
nasal cavities or into the trachea. If the later happen
coughing will most likely force the food up out of the
trachea and into the pharynx again.
The esophagus:
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A muscular tube that passes from the
pharynx through the thoracic cavity and
diaghram into the abdominal cavity
where it joins the stomach.
It is ordinarily collapsed, but it opens
and receives the bolus when
swallowing.
Esophagus
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Peristalsis is a rhythmic contrast which
pushes food along the digestive tract.
No chemical digestion of food occurs.
There is a sphincter (valve) between the
esophagus and stomach. Relaxation of the
sphincter allows the bolus to pass into the
stomach, while contrast prevents the acidic
contents of the stomach from backing up into
the esophagus.
If it happens heart burn which feels like
burning pain rising up into the throat.
The accessory organs
A.
Pancreas:
 1. Can be an endocrine gland, it secretes
insulin and glucagons, hormones that help
keep the blood glucose level within normal
limits.
 2. Can be an exocrine gland which produces
pancreatic juice which contains sodium
bicarbonate and digestive enzymes for all
types of food.
 3. Pancreatic amylase—digests starch
 4. Trypsin---digest protein.
 5. Lipase---digest fat.
B.
The
Liver
Functions:
1. Detoxifies blood by removing and metabolizing
poisonous substances.
2. Stores iron and fat-soluble vitamins A, D, E, K and B12
3. Makes plasma proteins, such as albumins and fibrinogen
from amino acids.
4. Stores glucose as glycogen after eating and breaks down
glycogen to glucose to maintain the glucose
concentration of blood between eating periods.
5. Produces urea after breaking down amino acids.
6. Removes bilirubin breakdown products of hemoglobin
from the blood, and excretes it into bile (a liver product)
7. Helps regulate blood cholesterol level, converting some
to bile salt.
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Disorders:
1. Hepatitis: Inflammation of the liver.
 Hepatitis A---from swage-contaminated drinking
water.
 Hepatitis B---spread by sexual contact, blood
transfusion or contaminated needles. Moore
contagious than AIDS.
 Hepatitis C---Acquired by contact with infected
blood, there is no vaccine. Can lead to chronic
hepatitis liver cancer and death.
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2. Cirrhosis: A chronic disease. First the organ
becomes fatty and liver tissue is then
replaced by inactive fibrous scar tissue.
It is seen in alcoholics due to malnutrition and
the excessive amounts of alcohol (toxin) the
liver is forced to break down.
The liver has amazing generative powers and
can recover if the rate of generation exceeds
the rate of damage.
During liver failure there may not be enough
time to let the liver heal itself.
C. The gallbladder
Excess bile is stored in the gallbladder. Water is
reabsorbed by the gallbladder so that bile
becomes thick mucus like material. When
needed bile leaves the gallbladder and
proceeds to the duodenum via common bile
duct. The cholesterol content of bile can
come out of solution and form crystals. If
they grow in size they form gallstones. The
passage of the stones from the gall bladder
may block the common bile duct and cause
obstructive jaundice. Then the gallbladder
must be removed.
Imaging Modalities
1.
Fluoroscopy:
Upper GI------Barium meal
Barium swallow
Lower GI------Barium follow through
Barium Enema
2. Abdominal CT
Cross-sectional slices of the abdomen is
imaged and viewed
Image reconstruction is possible where
3D images, CT endoscopy, CT
fluoroscopy can be produced
Radiograph from
double-contrast
upper GI showing
normal duodenum.
Radiograph from
double-contrast
upper GI showing
normal esophagus.
Stomach with normal
folded lining of the
stomach and normal
duodenum.
Radiograph from
double-contrast
upper GI showing
normal stomach.
Right side of the large
intestine. Air (dark)
distends the bowel
and barium (white)
coats the inner
lining.
Normal air-contrast
barium enema.