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The Digestive System
Ch 35-1 NWRC BIO 30
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Video on Digestion
http://uk.youtube.com/watch?v=sCn5uvvc3WE&feature=relatedhttp://uk.youtube.com/watch?v=sCn5uvvc3WE&feature=related -
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The esophagus is the
first part of thedigestive tract..
Approximately 10
inches in length, it
consists of three tissuelayers consistent with
the rest of the gut.The
muscles of peristalsis
begin propelling the
food bolus through the
esophagus into the
stomach.
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What stops food going
the wrong way!
The swallowing reflex
is activated by the
pushing of food to the
back of the throatfood is swallowed into
the esophagus. The
epiglottis covers the
trachea so food doesnt
go the wrong way
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The
Stomach
Very acidic
environment
(enzyme)pepsin
breaks
down
proteins
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The Stomach
The stomach is a C-shaped pouch that receives the
food bolus from the esophagus. It aids both in
mechanical and chemical digestion. Acting like achurn, the stomach mixes the food with gastric
acid and breaks down the food into a milky
substance known as chyme. The acid reduces the
pH of the stomach, in the process allowingactivation of an enzyme called pepsin. This starts
the chemical digestive process.
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The Stomach
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Small intestineThe majority of digestion occurs
in the small intestine. This
compartment has three distinctportions, each of which is highly
specialized for different digestive
functions. VIDEO
http://uk.youtube.com/watch?v=xu5jDCX2cHM&feature=relatedhttp://uk.youtube.com/watch?v=xu5jDCX2cHM&feature=related -
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The small Intestine
The small intestine is the longest portion of the
digestive tract - it is more than 6-7 meters long
and is located within the middle of the abdomen. Ithas three sections, the duodenum, jejunum and
ileum
Digestion of fats, proteins and carbohydrates
contained in the foods you consume, is completedwithin the small intestine.
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The Small Intestine
The lining of the small
intestine secretes a
hormone calledsecretin, which
stimulates the
pancreas to produce
digestive enzymes.
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The pancreas
Digestive enzymes are released from the
pancreas to enable the degradation process.
Bile is released from the gall bladder andmixes with the chyme to aid in fat digestion
and absorption.
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The Liver
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The LiverThe liver is the largest
glandular organ of the body. It
weighs about 3 lb (1.36 kg). It
is reddish brown in color andis divided into four lobes of
unequal size and shape. The
liver lies on the right side of
the abdominal cavity beneaththe diaphragm.
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The Liver
Some of the functions are: to produce
substances that break down fats,
convert glucose to glycogen, produce
urea (the main substance of urine),make certain amino acids (the building
blocks of proteins), filter harmful
substances from the blood (such as
alcohol), storage of vitamins and
minerals) and maintain a proper level
or glucose in the blood.
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The Gall Bladder
The gallbladder is
about 10-12 cm long in
humans and appearsdark green because of
its contents (bile),
rather than its tissue. It
is connected to the liver
and the duodenum
(small intestine)
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The Gall Bladder
The gallbladder stores
about 50ml of bile
which is released whenfood containing fat
enters the digestive
tract.
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The Gall BladderThe bile, produced in theliver, emulsifies fats and
neutralizes acids in partly
digested food.
After being stored in the
gallbladder, the bile becomes
more concentrated than
when it left the liver,increasing its potency and
intensifying its effect on fats.
Most digestion occurs in the
duodenum
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The Large Intestine
The large intestine (the colon) has several majorcomponents. The cecum is the entrance to the right side ofthe colon. There is a circular muscle, or sphincter, that
separates the small intestine from the large intestine. Thesphincter protects the small intestine from the concentrated
bacteria of the large intestine. Following the cecum, theascending colon rises up and leads into the transversecolon. From there, the descending colon dives back down
on the left side of the abdomen into the sigmoid colon andrectum. Waste is finally eliminated through the anus.
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Assessment
1. Digestion begins in
mouth, continues in
stomach and ends insmall intestine
Each type of molecule
is broken down into its
simplest part thoroughthe use of enzymes.
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Assessment
2. Mechanicaldigestion such aschewing grinds foodinto smaller particles
Chemical digestion byacids and enzymeschanges foodchemically such as
breaking proteinsdown into amino acids
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Assessment
3. the 3 main functions
are to
A. ingest food B. break it down
C. eliminate what
cannot be digested
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Assessment
4. The villi increase
the surface area so that
more nutrients can beabsorbed, if the lining
was smooth fewer
nutrients would be
absorbed
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Extra Review
Link to printable worksheetstest yourself!
http://www.wikieducator.org/Digestive_System_Worksheethttp://www.wikieducator.org/Digestive_System_Worksheet