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The Digestive SystemChapter 13
Why Do We Eat?
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What is digestion?
Let’s find out what happened to your breakfast today!
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DigestionProcessing of Food
(copy)
• Type one • Mechanical (physical)• Chewing• Tearing• Grinding• Mashing• Mixing
(Copy)
• Type two • Chemical• Catabolic
reactions• Enzymatic
hydrolysis• Carbohydrates• Proteins• Lipids
• Ingestion• Movement• Digestion• Secretion• Absorption• Excretion
Functions of the digestive system(copy)
(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
Mouth-mechanical digestion mastication) = teeth, tongue-chemical digestion = saliva
Uvula – prevents food entering the nose
Alimentary canal (copy)2 main functions:•Digesting and absorbing nutrients•Protecting from invasion
(COPY)
Epiglottis – safety hatch. A flap of cartilage prevents food from entering the trachea
Trachea - windpipe
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Swallowing (Copy)
Sequence• Voluntary stage
• Push food to back of mouth
• Esophageal stage• Open esophagus• Start peristalsis
Oesophagus (Copy)-transfers food to stomach by peristalsis
Cardiac sphincter
-opens to allow food oesophagus stomach
-heartburn –acid escapes stomach
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Peristalsis and Segmentation
http://35.9.122.184/images/41-AnimalNutrition/41-16-Duodenum-L.gif
(Copy) Stomach
Stores the food you eatDigestion = chemically - breaks it down into tiny pieces
= mechanical – mixes food with digestive juices acid in the stomach kills bacteria
Cardiac sphincter
Pyloric sphincter
Slowly releases food into intestine
Small Intestine (copy)Around 6m in an adultFood takes 1-6 h to pass throughEnzymes and bile are added2 main tasks = digestion, absorption
nutrients pass into bloodstream through small intestine walls
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Anatomy of the Large Intestine
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.
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Related Organs
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
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The Organs and Positions in the Abdominal Cavity
Rectum and Anus (copy)
• Rectum• About 15cm
long• Stores waste
before egesting.
• Anus• Muscular ring
that controls egesting.