Download Lesson 14

lesson14.notebook
February 26, 2013
Pathway of Food
Review:
1. The mouth ­
essential nutrients
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contains the teeth which help mechanical
digestion and the tongue. ­
mechanical and chemical digestion
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various parts of digestive system/functions
the tongue is made of skeletal tissue and changes shape when it contracts. It is connected to the floor of the mouth by a mucus membrane and is covered by tiny pimple like structures called papillae. ­
the uvula hangs from the roof and prevents excessive food from entering the pharynx. ­
the mouth packages the food and moves it to the esophagus.
Apr 30­2:38 PM
Apr 30­2:41 PM
2. The esophagus ­
is the connecting tube from the mouth to the stomach. ­
It is lined with muscles to move food and mucin which is a lubricant. ­
It transports food to the stomach using muscle contractions called peristalsis
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there is a sphincter muscle at the base of the esophagus which controls food entering the stomach
Apr 12­1:50 PM
Apr 30­2:49 PM
3. The stomach Apr 12­1:53 PM
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is a j shaped, sac like structure containing a third layer (oblique layer) that works to break down food physically and mix it with gastric juices. ­
thus in the stomach there is chemical and mechanical digestion
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It prepares food for the small intestines by breaking it down and exposing it to chemical enzymes
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this creates chyme which is sent to the small intestines for further digestion
Apr 30­2:59 PM
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lesson14.notebook
February 26, 2013
4. The small intestines ­
chyme enters here after it leaves the stomach. ­
It is composed of three parts and is lined with villi and microvilli that help absorption of nutrients.
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nutrients are absorbed here and passed on to the blood stream for distribution around the body ­
any material that is undigested moves to the large intestines where it will exit the body
Apr 12­1:55 PM
Apr 30­3:02 PM
5. The large intestine ­
is divided into separate sections. ­
undigested material is stored here as feces. ­
the feces passes out through the body at the end of the anal canal, referred to as the anus.
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there is a large sphincter which controls the exit of feces
Apr 12­1:59 PM
Apr 30­3:06 PM
Movement of Food Through the Digestive System:
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aided by the physical effect of water which acts as a lubricant to ease the passage of food through the digestive tract
­ also helped by peristalsis, a series of wavelike contractions and relaxations of the longtitudinal and circular muscles that move food
(See page 362, figure 11.8)
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peristalsis occurs in the esophagus and also in the intestines where partially digested food is thoroughly mixed in, this is known as rhythmical segmentation
(See page 363, figure 11.9)
Digestion Video:
Apr 12­2:00 PM
Apr 30­3:14 PM
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lesson14.notebook
February 26, 2013
Chemical Digestion and Enzymes:
Label the Following Diagram:
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digestion is the chemical breakdown of food by hydrolysis
­ hydrolysis is a reaction where bonds between molecules are broken down by the addition of a water molecule
­ the water molecule is added at a point where a link in a complex molecule can be broken
­ the reaction occurs at a slow rate but is immediately sped up by adding enzymes
­ enzymes are biological catalysts that are proteins manufactured in the ribosomes of cells, there are three main types involved with digestion
Apr 30­3:19 PM
(a) Carbohydrases: (b) Lipases: May 1­9:56 AM
Help break down carbohydrates.
Remember:
Help break down fat.
(c) Proteinases: Help break down protein.
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carbohydrates are broken down into starches and sugars
­ many enzymes require specific conditions in order to work( eg. acidic, alkaline or neutral environments)
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proteins are broken down into polypeptides and then amino acids
­ enzymes are adversely affected by temperature and many of them require the presence of ions, vitamins or coenzymes
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fats are broken down into fatty acid and glycerol
EXAMPLES:
Starch + Water
salivary enzyme(amylase)
Maltose (mouth)
Maltose
maltase
Glucose (s. intestine)
May 1­10:01 AM
Apr 13­2:31 PM
Readings:
Pages 359 ­ 365 (see table 11.2 on page 365)
Activity:
Label the diagram
May 1­9:53 AM
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