Transcript Digestive Structures

Digestive Structures
Unit D – Human Systems
Breaking down digestion
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There are four components to the process
of digestion:
Ingestion  taking food into your body.
Digestion  breakdown of food by
enzymes.
Absorption  transportation of digested
food to the cells of the body.
Review Video
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Digestion Review Video
4. Egestion  Removal of food waste from
body.
Physical Digestion
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Also known as mechanical digestion.
Breaks up large pieces of food into smaller
pieces.
Purpose is to increase surface area so that
enzymes can break down small pieces of
food.
Examples: chewing by teeth, churning of
stomach.
Chemical Digestion
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Use of enzymes (NOT CHEMICALS) to
break down food into small enough pieces
that it can be absorbed into your
bloodstream.
NOTE: In this section, enzymes will be
denoted by italics.
Salivary glands
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Release watery fluid called saliva into your
mouth.
Saliva dissolves food particles, lubricates
food so it can be swallowed, and allows
you to taste food.
Saliva contains amylase enzyme.
Saliva Secretion Video Clip
Mouth/Teeth
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Food enters here and is broken down into
smaller pieces by teeth.
Different teeth are specialized for cutting,
tearing, grinding and crushing your food.
Tongue forms saliva and food into a ball or
bolus, which is ready to move down your
throat.
Esophagus
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Tube that connects your mouth to your
stomach.
Bolus of food stretches the walls of the
esophagus, activating waves of
contractions called peristalsis which move
food along your gastrointestinal tract.
Entry into the stomach is control by a
muscle called a sphincter.
Stomach
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Site of food storage and beginning of
protein digestion.
Can hold about 1.5 L of food.
Stomach fluids are also called gastric
fluids.
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The three major components of gastric
fluids are hydrochloric acid, mucus and
pepsinogen.
Hydrochloric acid destroys bacteria that
enter the body along with food.
Hydrochloric acid activates pepsinogen
enzyme into its active form called pepsin.
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In order to protect your stomach from the
hydrochloric acid, it is lined with an alkaline
or basic layer of mucus.
Food material will now be in liquid form and
passes through the pyloric sphincter to
enter the small intestine.
Small Intestines
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Major site of chemical digestion and
absorption of food into the bloodstream.
Approximately 7 metres in length.
Has a basic pH of around 9.
Covered with long fingerlike projections
called villi, which increase the surface area
of the small intestine.
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Increased surface area for absorption
means that more nutrients can be
absorbed.
Each villus (singular of villi) has its own
blood supply and lymphatic supply, so that
absorbed food can be taken to cells all
around the body.
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Digested carbohydates
(monosaccharides) and proteins (amino
acids) are absorbed into the bloodstream.
Digested fats are too large to move into the
bloodstream and enter lacteals, which are
transportation tubes that make up the
lymphatic system.
Large Intestine
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Major site of water reabsorption and stores
undigested food.
Bacteria like E.coli live here and breakdown
waste material to make vitamins B and K.
Undigested plant material (cellulose, fiber)
builds up in your large intestine.
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When enough waste is present, the
intestinal walls are stretched, a signal is
sent to the central nervous system and
waste is eliminated from the body.
Bowel movements make sure that toxic
substances can be removed from the body.
Student Tasks
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Draw a flow chart linking the major organs
of digestion and summarizing the basic
functions of each.
Label digestive system diagram.
Complete pg. 263 #2,3,5,6,7,13,14,15 for
your homework book.
Review your notes and key terms for
tomorrow’s class.