Download Digestive System - School District of Clayton

Digestive System
 Every cell in the body must receive food to
perform cellular respiration for energy.
 Food particles are broken down physically
and chemically into food monomers by the
digestive system.
 Food monomers are absorbed into the blood
by the small intestine.
 Food monomers are carried to every cell in
the body by the circulatory system.
Digestion in the Mouth
 Digestion begins when food is broken down
physically by teeth and chemically by saliva.
 The enzyme, salivary amylase, is secreted
by 3 salivary glands and breaks down
starches into complex sugars.
 The bolus- a moistened ball of food, passes
through the pharynx and is swallowed into
the esophagus by moving the epiglottis over
the trachea.
Teeth
Digestive System in the
Human Body
Digestion
 Esophagus connects mouth to stomach.
 Bolus is moved to the stomach by
peristalsis.
 Peristalsis is the wavelike contractions of
smooth muscle.
 The bolus enters the stomach through the
cardiac sphincter.
Digestion in the Stomach
 Gastric Juices are secreted by the walls of the
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stomach.
Stomach pH is 1.0- 3.5
Mucus coating protects the lining of the stomach.
HCl denatures proteins; unravels globular tertiary
structure into long polypeptide chains.
The enzyme pepsin breaks down the polypeptide
chains into shorter amino acid chains.
Peristaltic waves of the stomach help digest food.
The Stomach and Other
Digestive Organs
Stomach Ulcer
Digestion in the S.I.
 Food leaves the stomach through the pyloric
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sphincter as an acidic liquid called chyme.
Bicarbonate ion is released by the pancreas
into the duodenum to neutralize the chyme.
Pancreas secretes pancreatic juices- trypsin,
pancreatic amylase, and lipase, into the
duodenum.
Pancreatic amylase breaks down complex
sugars in into simple sugars.
Trypsin breaks down amino acid chains into
individual amino acids.
Fat Digestion in the S.I.
 Bile is used for emulsification and helps
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dissolve fat soluble vitamins (A, D, E, K).
Bile is produced by the liver, stored in the
gallblader, and transported through the bile duct
into the duodenum.
Fats are non-polar. The enzyme lipase is polar.
Bile is amphipathic- large molecule that is both
polar and non polar.
Emulsification- bile separates large fat globules
into smaller fat droplets so lipase (from the
pancreas) can break them down into fatty acids
and glycerol.
Small Intestine
 Food monomers (sugars, amino acids, glycerol,
fatty acids) are absorbed by villi on the walls of
small intestine.
 Villi and microvilli greatly increase the surface area
of the small intestine.
Villi in the Small Intestine
Cross Section of the Small
Intestine
Large Intestine
 Wastes that are not absorbed by the S.I. are
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removed by the Large Intestine (Colon).
L.I. is ~3.3 ft. long but 3x wide as the S.I.
No digestion in the L.I.
Water and ions are absorbed in the L.I.
Bacteria in the large intestine produce vitamin
K, B Vitamins, and help process feces.
Wastes pass to the end of the colon, the rectum
and expelled by the anus.