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digestive system
- a coiled hollow, muscular tube that is open on both ends
- mouth -> anus
- lined with mucous membrane
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3 components of the digestive system
- digestive tract
- alumentary canal
- gastrointestinal tract
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4 major functions of digestive tract
- ingestion
- digestion
- absorption
- defecation
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ingestion
putting food into mouth
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digestion
breaking the food down into smaller molecules that our cells can use
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absorption
absorption of nutrients from digestive tract into blood
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defecation
ridding the body of wastes
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we take food into the mouth
the teeth will mechanically break down food into smaller pieces
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why do we break food into smaller pieces in the mouth?
- so it fits down the throat
- increase surface area for more efficient chemical breakdown
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why is food mixed with saliva?
it contains amylase
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amylase
enzyme that breaks down carbs
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bolus
a ball that is formed by the tongue mixing the food with saliva
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What does the tongue do with the bolus?
pushes it into the oropharynx
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stomach
- temporary storage tank for the chyme
- can hold up to a gallon of chyme when full
- walls are thrown into folds called rugae when empty
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chyme
what used to be the bolus
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gastroesophageal sphincter
keeps the chyme from flowing back up into esophagus
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heartburn
- when stomach is over full or gastroesophageal sphincter doesn't close properly
- achidic chyme burns walls of esophagus
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pyloric sphincter
- regulates stomach emptying
- lets out a little chyme at a time
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small intestine
- "small" because of its diameter
- some chemical breakdown occurs here by enzymes
- major function - absorption of nutrients into the bloodstream
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what 3 structures does the small intestine have that make it very efficient at absorption
- villi
- microvilli
- circular folds
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circular folds within small intestine
greatest absorptive surface area
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large intestine
- frames the small intestine
- "large" because of it's diameter
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parts of large intestine
- cecum
- colon - ascending, transverse, descending, sigmoid
- rectum
- anus
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function of large intestine
- to absorb water back into the body
- dries out the waste (feces)
- propels the waste to outside the body
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bile
- an emulsifier that helps to break down fats (lipids)
- stored and concentrated in the gall bladder
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gall bladder
- stores and concentrates bile
- releases bile into duodenum
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vitamins
- fat soluble - A, D, E, K
- water soluble - B, C
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esophagus
- about 10" long
- muscular tube
- collapsed when empty
- posterior to trachea
- pushed bolus into stomach by peristalsis
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peristalsis
wave like muscular contractions
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3 devisions of the small intestine
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3 macronutrients
- carbohydrates
- lipids
- proteins
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carbohydrates
- breakdown into: simple sugars
- enzyme: amylase
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lipids
- breakdown into: fatty acids
- enzyme: lipase
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proteins
- breakdown into: amino acids
- enzyme: protease
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What 2 types of digestion take place in the stomach?
- chemical by enzymes
- mechanical by churning
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