Download Section Two Reading Notes 4

Reading Notes
Section 6.2
Pages 217-231
The Digestive System
The organs that make up the human digestive tract are the ___________,
______________, stomach, ___________ intestine, large intestine, ___________,
and anus.
The accessory organs are the salivary glands, ___________, gall bladder, and
_____________.
PHYSICAL DIGESTION BEGINS
The _____________ (physical) digestion of food begins in the mouth because you
use your ___________ to chew your food. Water and mucus in saliva aid the teeth
as they tear and grind food into smaller pieces, increasing the ___________
available for the __________ digestion of any __________ that has been ingested.
Chemical digestion starts in the mouth, when an enzyme in saliva, called
________________, begins to break down starch into simpler sugars
(________________).
The __________ moves through the _____________ partly by ____________ but
mainly through a wave-like series of muscular ________________ and
_________________ called ________________. As _______________ continues,
food is propelled through the ____________ toward the _______________, where
the next stage of digestion occurs.
Entry to the ______________ is controlled by a ring-like muscular structure called
the ____________________. Relaxation of the ______________________ allows
the bolusto pass into the ________________. ________________ of this sphincter
usually prevents the _______________ contents of the ________________ from
backing up into the esophagus.
STORING, DIGESTING AND PUSHING FOOD: THE STOMACH
Both _________________ and _________________ digestion occur in the
stomach. Waves of __________________ push food against the bottom of the
stomach, churning it backward, breaking it into ____________ pieces, and mixing
it with ____________ to produce a thick liquid called _____________.
Once active, ____________ hydrolyzes proteins to yield ________________—a
first step in protein digestion in the digestive tract.
Very few substances are absorbed from the chyme in the stomach because most
substances in the chyme have not yet been broken down _________________. The
stomach does absorb some ____________ and salts, however, as well as certain
anti-inflammatory medications, such as ____________, and ________________.
In the ___________________, bands of circular _______________ briefly contract
forming closed _______________. This process is called _____________.
__________ is sloshed back and forth within the segment, causing
_______________ digestion and mixing the nutrient ________________ with
digestive ______________. Such movement increases contact between nutrients
and the intestinal wall which enhances nutrient ______________.
Peristalsis also occurs, mixing food and enzymes and pushing it on toward the
_____________ intestine.
DIGESTING AND ABSORBING NUTRIENTS: THE SMALL INTESTINE
The ridges in the inner lining of the small intestine are covered in tiny projections
called _____________, which, in turn, are covered in microvilli. Together, the
ridges, ____________, and ____________ vastly increase the absorptive
_______________of the small intestine.
The _______________, _____________, and gall bladder produce and/or store
secretions necessary for digestion of macromolecules.
_______________: The pancreas delivers about 1 L of pancreatic fluid to the
_________________ each day. Pancreatic fluid contains a multitude of
____________, including:
■ trypsin and ______________, which are proteases that digest ______________;
■ pancreatic ______________, which is a ________________ that digests
_______________ in the small intestine; and
■ ________________, which digests fat.
Liver: The liver is the _______________ internal organ of the human body. The
main digestion-related secretion of the liver is ___________, a greenish-yellow
fluid mixture that is made up of ________________ and bile _____________. Bile
salts assist ____________ in accessing fats because they are partly soluble in
___________ and partly soluble in _____________. Bile salts work like a
______________, dispersing large fat droplets into a fine __________________ of
______________ droplets in the chyme. This ___________________ process
produces a _________________ surface area of fats on which the
________________ can act.
_______________: After bile is produced in the liver, it is stored in the
___________. The arrival of ___________, with a high __________
concentration, in the duodenum stimulates the _____________ to contract. This
causes bile to be transported through a __________ (shared by both the gall
bladder and the liver) and injected into the ___________.
Most of the digestion of __________________ does not take place until the chyme
enters the small intestine, where the pH is about ____________.
In the ________________, pancreatic amylase completes the digestion of starch
into ________________-. Other carbohydrases hydrolyze the disaccharides into
___________________, such as glucose and ________________.
_________________ are absorbed by active transport into the cells of the intestinal
_____________. The _________________ of glucose and other monosaccharides
requires ______, which is produced in the _____________ of cells. From the cells
of the intestinal lining, the _______________ enter the bloodstream and are
transported directly to the ____________.
The arrival of ___________ (fats) in the duodenum stimulates the secretion of
__________, which ____________ the fat droplets. The breakdown of fats by
hydrolysis is carried out by ___________ secreted in the duodenum. The resulting
________________ and _____________ are absorbed into the cells of the villi by
simple ________________.
In the small intestine, _____________ are digested by enzymes, called nucleases,
to yield ________________. The nucleotides are hydrolyzed to their constituent
_____, ______________, ______________. These molecules are then
____________, like glucose and amino acids, into the bloodstream by active
transport.
______________, produced by the lower part of the stomach, enters the
bloodstream and stimulates the upper part of the stomach to produce more gastric
juice.
Secretin and CCK, produced by the duodenal wall, stimulate the ______________
to secrete its digestive juice and the gall bladder to release ___________.