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The Digestive The Digestive SystemSystemSNC2DSNC2D
The Digestive TractThe Digestive Tract
The digestive system consists of the The digestive system consists of the digestive digestive tracttract, a series of hollow organs which may be , a series of hollow organs which may be thought of as a long twisting tube connecting thought of as a long twisting tube connecting the mouth to the anus, and other organs that the mouth to the anus, and other organs that produce or store chemicals that help break produce or store chemicals that help break down or absorb food.down or absorb food.
Those Other OrgansThose Other Organs
The other organs include the The other organs include the liver and the pancreas, and liver and the pancreas, and the chemicals they produce the chemicals they produce reach the intestine through reach the intestine through small tubes called ducts.small tubes called ducts.
Those Other OrgansThose Other Organs
The other organs include the The other organs include the liver and the pancreas, and liver and the pancreas, and the chemicals they produce the chemicals they produce reach the intestine through reach the intestine through small tubes called ducts. small tubes called ducts. The chemical produced by The chemical produced by the liver is called the liver is called bilebile, and it , and it may be stored in the may be stored in the gallbladder between meals.gallbladder between meals.
The MouthThe Mouth
Digestion begins in the mouth where an Digestion begins in the mouth where an enzymeenzyme (a chemical that speeds up other (a chemical that speeds up other chemical reactions) in the saliva produced chemical reactions) in the saliva produced by the salivary glands start to break down by the salivary glands start to break down those carbohydrates known as starches.those carbohydrates known as starches.
PeristalsisPeristalsis
Once the food is swallowed, it Once the food is swallowed, it is moved through the is moved through the digestive tract by digestive tract by peristalsisperistalsis, , involuntary muscle involuntary muscle contractions triggered by the contractions triggered by the nervous system.nervous system.
To The StomachTo The Stomach
Food travels down the esophagus to the Food travels down the esophagus to the stomach. Between the esophagus and the stomach. Between the esophagus and the stomach there is a muscle called the lower stomach there is a muscle called the lower esophageal sphincter, which opens to let food esophageal sphincter, which opens to let food pass through.pass through.
To The StomachTo The Stomach
Food travels down the esophagus to the Food travels down the esophagus to the stomach. Between the esophagus and the stomach. Between the esophagus and the stomach there is a muscle called the lower stomach there is a muscle called the lower esophageal sphincter, which opens to let food esophageal sphincter, which opens to let food pass through. If it opens when it shouldn’t, you pass through. If it opens when it shouldn’t, you get acid reflux get acid reflux
(heartburn).(heartburn).
In the StomachIn the Stomach
Glands in the stomach lining produce Glands in the stomach lining produce stomach acid and an enzyme to break stomach acid and an enzyme to break down proteins. A thick layer of mucus down proteins. A thick layer of mucus helps protect the lining of the stomach helps protect the lining of the stomach from its own acids.from its own acids.
Bacterial infections can thin the mucus so that the stomach eats away at its own lining: this is an ulcer.
In the StomachIn the Stomach
Glands in the stomach lining produce Glands in the stomach lining produce stomach acid and an enzyme to break stomach acid and an enzyme to break down proteins. A thick layer of mucus down proteins. A thick layer of mucus helps protect the lining of the stomach helps protect the lining of the stomach from its own acids.from its own acids.
In the StomachIn the Stomach
Glands in the stomach lining produce Glands in the stomach lining produce stomach acid and an enzyme to break stomach acid and an enzyme to break down proteins. A thick layer of mucus helps down proteins. A thick layer of mucus helps protect the lining of the stomach from its protect the lining of the stomach from its own acids.own acids.
Muscle action of the stomach mixes the food Muscle action of the stomach mixes the food with the digestive juices, and this mixture is with the digestive juices, and this mixture is then emptied into the small intestine then emptied into the small intestine through the through the pyloric sphincterpyloric sphincter..
The IntestinesThe Intestines
The first part of the small The first part of the small intestine, where the intestine, where the chemicals produced by the chemicals produced by the other organs enter the other organs enter the digestive process, is called digestive process, is called the the duodenumduodenum. Here, the . Here, the bile produced by the liver bile produced by the liver dissolves fat.dissolves fat.
The IntestinesThe Intestines
The small intestine is folded into fingerlike The small intestine is folded into fingerlike projections called projections called villivilli. This folding increases . This folding increases the surface area of the small intestine through the surface area of the small intestine through which food molecules are absorbed into the which food molecules are absorbed into the bloodstream.bloodstream.
The IntestinesThe Intestines
The large intestine, or The large intestine, or coloncolon, does not break , does not break down food but absorbs water and some down food but absorbs water and some nutrients before what remains of the food is nutrients before what remains of the food is removed from the body as waste.removed from the body as waste.
The IntestinesThe Intestines
The large intestine, or The large intestine, or coloncolon, does not break , does not break down food but absorbs water and some down food but absorbs water and some nutrients before what remains of the food is nutrients before what remains of the food is removed from the body as waste.removed from the body as waste.
Note that the waste will Note that the waste will
also include some cells also include some cells
shed by the digestive shed by the digestive
system itself.system itself.
The Body’s DefencesThe Body’s Defences
The digestive system’s first defence The digestive system’s first defence against contaminants is vomiting, which against contaminants is vomiting, which can forcibly remove contents from the can forcibly remove contents from the middle of the small intestine and up.middle of the small intestine and up.
Really, you don’t want any images here.
Very Limited DefencesVery Limited Defences
There is really nothing else to prevent There is really nothing else to prevent contaminants from being absorbed into contaminants from being absorbed into the bloodstream although the liver can the bloodstream although the liver can help filter the blood.help filter the blood.