The Digestive System
Chapter 13
Why Do We Eat?
What is digestion?
2
Let’s find out what happened to
your breakfast today!
Digestion
Processing of Food
(copy)
• Type one
• Mechanical
(physical)
• Chewing
• Tearing
• Grinding
• Mashing
• Mixing
4
(Copy)
• Type two
• Chemical
• Catabolic
reactions
• Enzymatic
hydrolysis
• Carbohydrates
• Proteins
• Lipids
Functions of the digestive system
(copy)
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Ingestion
Movement
Digestion
Secretion
Absorption
Excretion
(Copy)
• Gastrointestinal System
• Includes alimentary canal
and accessory organs
• Accessory organs:
Salivary glands, tongue,
teeth, liver, gallbladder,
and pancreas
Steps in Digestion
(Copy)
• Mouth – Crushing and grinding
• Stomach – Chemical Breakdown
• Small Intestine – Useful material
extracted
• Colon – Water removal
Alimentary canal (copy)
2 main functions:
•Digesting and absorbing
nutrients
•Protecting from invasion
Mouth
-mechanical digestion
mastication) = teeth, tongue
-chemical digestion = saliva
Uvula – prevents food entering
the nose
(COPY)
Trachea - windpipe
Epiglottis – safety hatch.
A flap of cartilage
prevents food from
entering the trachea
Swallowing (Copy)
Sequence
• Voluntary stage
• Push food to back
of mouth
• Esophageal stage
• Open esophagus
• Start peristalsis
11
Oesophagus (Copy)
-transfers food to stomach
by peristalsis
Cardiac sphincter
-opens to allow food oesophagus
stomach
-heartburn –acid escapes
stomach
Peristalsis and Segmentation
13
(Copy) Stomach
Stores the food you eat
Digestion = chemically - breaks it down
into tiny pieces
= mechanical – mixes food with
digestive juices acid in the
stomach kills bacteria
Slowly releases food into
intestine
Cardiac sphincter
Pyloric sphincter
http://35.9.122.184/images/41-AnimalNutrition/41-16-Duodenum-L.gif
Small Intestine (copy)
Around 6m in an adult
Food takes 1-6 h to pass through
Enzymes and bile are added
2 main tasks = digestion, absorption
nutrients pass into bloodstream
through small intestine walls
Anatomy of the Large Intestine
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Large Intestine (copy)
• About 1.5 meters long
• Accepts what small
intestines don’t
absorb.
• Absorbs water and
minerals from the
waste matter.
Liver (copy)
• Directly affects
digestion by
producing bile
• Bile is an
enzyme that
helps dissolve
fat
• Processes
nutrients in the
blood, filters out
toxins and waste.
Related Organs
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Gall Bladder (copy)
• Stores bile from
the liver
• Delivers bile
when food is
digested
• Fatty diets can
cause
gallstones
Pancreas (copy)
• Produces
compounds to
digest fats and
proteins
• Neutralizes acids
that enter small
intestine
• Regulates blood
sugar by
producing insulin
The Organs and Positions in the
Abdominal Cavity
22
Rectum and Anus (copy)
• Rectum
• About 15cm
long
• Stores waste
before
egesting.
• Anus
• Muscular ring
that controls
egesting.