the digestive system. digestive system built around an alimentary canal (one-way tube) built around...
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The Digestive SystemThe Digestive System
Digestive SystemDigestive System
Built around an alimentary canal Built around an alimentary canal (one-way tube)(one-way tube)
IncludesIncludesMount, pharynx, esophagusMount, pharynx, esophagusStomachStomachSmall intestineSmall intestineLarge intestineLarge intestineSalivary glands, pancreas, liverSalivary glands, pancreas, liver
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The Digestive System
Mouth Mouth
Begins mechanical digestion with Begins mechanical digestion with chewingchewingTeeth crush food to make a fine paste Teeth crush food to make a fine paste
for swallowingfor swallowingBegins chemical digestion with salivaBegins chemical digestion with saliva
Digestive enzymes begin breakdown of Digestive enzymes begin breakdown of carbohydrates into smaller moleculescarbohydrates into smaller molecules
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Your Mouth
Teeth Teeth
Anchored in jaw bonesAnchored in jaw bonesProtected by mineralized enamelProtected by mineralized enamelUsed to cut, tear, and crush food into Used to cut, tear, and crush food into
smaller fragmentssmaller fragments
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Tooth
Saliva Saliva
Secreted by salivary glands in mouth Secreted by salivary glands in mouth to moisten food and make it easier to to moisten food and make it easier to chewchew
Controlled by nervous systemControlled by nervous systemBegins chemical digestionBegins chemical digestion
Enzyme amylase breaks down starches Enzyme amylase breaks down starches and releases sugarsand releases sugars
Lysozyme fights infection by digesting Lysozyme fights infection by digesting bacteria that may enter mouth with foodbacteria that may enter mouth with food
Esophagus Esophagus
Food (called a bolus) from mouth is Food (called a bolus) from mouth is swallowed (forced from mouth into swallowed (forced from mouth into esophagus by combined action of tongue esophagus by combined action of tongue and throat muscles)and throat muscles)
Bolus moved through esophagus by Bolus moved through esophagus by contractions (peristalsis) of smooth contractions (peristalsis) of smooth muscles to the stomachmuscles to the stomach
Cardiac sphincter at the bottom of Cardiac sphincter at the bottom of esophagus prevents food in stomach from esophagus prevents food in stomach from moving back into esophagusmoving back into esophagus
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Peristalsis
StomachStomach
Muscular sac that continues Muscular sac that continues mechanical and chemical digestionmechanical and chemical digestion
Three layers of smooth muscle Three layers of smooth muscle thoroughly churn and mix food to thoroughly churn and mix food to help with digestionhelp with digestion
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Stomach
Chemical digestion in Chemical digestion in stomachstomach
Glands in the stomach lining release Glands in the stomach lining release lubricants (to protect the stomach lubricants (to protect the stomach wall), hydrochloric acid (HCl), and wall), hydrochloric acid (HCl), and pepsin (enzyme)pepsin (enzyme)
Pepsin is activated by HCl to begin Pepsin is activated by HCl to begin protein digestion to break protein protein digestion to break protein into smaller pieces or amino acidsinto smaller pieces or amino acids
Other enzymes are denatured by HCl Other enzymes are denatured by HCl and stop carbohydrate digestionand stop carbohydrate digestion
Mechanical digestion in the Mechanical digestion in the stomachstomach
Stomach muscles contract to churn Stomach muscles contract to churn and mix stomach contentsand mix stomach contents
This makes chymeThis makes chymeAfter 1-2 hours the pyloric sphincter After 1-2 hours the pyloric sphincter
opens so chyme can pass into the opens so chyme can pass into the small intestinesmall intestine
Small intestineSmall intestine
Chyme enters the first part of the Chyme enters the first part of the small intestine called the duodenum small intestine called the duodenum
Digestive enzymes and fluids from Digestive enzymes and fluids from the pancreas and liver also enter at the pancreas and liver also enter at the duodenumthe duodenum
Most chemical digestion and Most chemical digestion and absorption of nutrients occurs in the absorption of nutrients occurs in the small intestinesmall intestine
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Pancreas & Liver
Effects of digestive enzymesEffects of digestive enzymes
Salivary amylase Salivary amylase (mouth)(mouth)
Pepsin (stomach)Pepsin (stomach)
Amylase (sm. Int. Amylase (sm. Int. from pancreas)from pancreas)
Trypsin (sm. Int. Trypsin (sm. Int. from pancreas) from pancreas)
Lipase (sm. Int. Lipase (sm. Int. from pancreas)from pancreas)
Breaks down starch Breaks down starch and disaccharidesand disaccharides
Breaks down Breaks down proteins into large proteins into large peptidespeptides
Continues Continues breakdown of starchbreakdown of starch
Continues Continues breakdown of breakdown of proteinprotein
Breaks down fatBreaks down fat
Effects of digestive enzymesEffects of digestive enzymes
Maltase, sucrase, Maltase, sucrase, lactase (sm. Int.)lactase (sm. Int.)
Peptidase (sm. Int.)Peptidase (sm. Int.)
Breaks down Breaks down remaining remaining disaccharides into disaccharides into single sugarssingle sugars
Breaks down Breaks down dipeptides into dipeptides into amino acidsamino acids
Accessory structures of Accessory structures of digestiondigestion
Pancreas (behind the stomach) has 3 Pancreas (behind the stomach) has 3 rolesrolesReleases hormones to regulate blood sugar Releases hormones to regulate blood sugar
levelslevelsReleases enzymes that break down Releases enzymes that break down
carbohydrates, proteins, lipids, nucleic acidscarbohydrates, proteins, lipids, nucleic acidsProduces sodium bicarbonate that Produces sodium bicarbonate that
neutralizes stomach acids so the enzymes neutralizes stomach acids so the enzymes can function (without neutralization, can function (without neutralization, enzymes denature and don’t function enzymes denature and don’t function properly)properly)
Accessory structures cont.Accessory structures cont.
Liver-(above and to the left of the Liver-(above and to the left of the stomach) produces bile loaded with stomach) produces bile loaded with lipids and saltslipids and salts
Bile dissolves fats in fatty foodsBile dissolves fats in fatty foodsBile is stored in the gallbladderBile is stored in the gallbladder
Absorption in the small Absorption in the small intestineintestine
Last 2 parts of the small intestine are the Last 2 parts of the small intestine are the jejunum and ileum, together are 6 meters jejunum and ileum, together are 6 meters longlong
When chyme enters these it is a mixture of When chyme enters these it is a mixture of medium and small nutrient molecules medium and small nutrient molecules (most chemical digestion is competed in (most chemical digestion is competed in the duodenum)the duodenum)
Lining of the small intestine is covered with Lining of the small intestine is covered with villi (fingerlike projections) each of which is villi (fingerlike projections) each of which is covered with microvilli, both are needed to covered with microvilli, both are needed to increase the surface area for absorptionincrease the surface area for absorption
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Villi
Absorption in the small int. Absorption in the small int. cont.cont.
Cells of small intestine absorb nutrientsCells of small intestine absorb nutrients Products of carbohydrate and protein Products of carbohydrate and protein
digestion are absorbed into capillaries in digestion are absorbed into capillaries in villi villi
Undigested fat and fatty acids are Undigested fat and fatty acids are absorbed by lymph vesselsabsorbed by lymph vessels
When food leaves small intestine and When food leaves small intestine and enters the large intestine it is nutrient free enters the large intestine it is nutrient free and contains only water, cellulose, and and contains only water, cellulose, and undigestible substancesundigestible substances
The large intestineThe large intestine
Also called the colonAlso called the colonPrimary function is to remove water Primary function is to remove water
from undigestible materialfrom undigestible materialWater is absorbed quickly through the Water is absorbed quickly through the
wall of the colonwall of the colonColonies of bacteria produce useable Colonies of bacteria produce useable
compounds such as vitamin Kcompounds such as vitamin KConcentrated waste that remains Concentrated waste that remains
passes through the rectum to be passes through the rectum to be excretedexcreted
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