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Vertebrate Digestive System
Chapter 8

1)    Define nutrition, nutrient and roughage.

2)    What is a carbohydrate, a lipid, and a protein.

3)    Identify the essential nutrients of a well balance diet, food sources of each and the role each nutrient plays in the body.

4)    Define digestion, explain the two types of digesting, chemical and mechanical.

5)    Describe the chemical and mechanical breakdown of food in the mouth.

6)    What is an enzyme?  List the 6 factors that characterize enzyme action.

7)    Define peristalsis.  Describe the events that occur during swallowing.

8)    Describe the stomach, and the chemical and mechanical breakdown of food that occurs here.

9)    Describe the small intestine.  What chemical and mechanical digestion occurs there?

10)    Discuss the involvement of the pancreas, liver and gallbladder in digestion.

11)    Explain how absorption occurs in the small intestine.

12)    Describe the large intestine and explain its three functions.

Chapter 35

13)    Compare the structure of the digestive system of mammal with that of another vertebrate such as a bird.

Answers
1) Nutrition is the process by which organisms obtain food and use it to perform life activities. (page 124)

        Nutrients are substances that can be used in metabolism.  Nutrients provide energy, ie. food. (page 124)

        Roughage is all food that is indigestible.  Fibre is roughage.  (page 124)

2) Carbohydrates are compound of carbon, oxygen, and hydrogen.  Carbohydrates are sugars, ie glucose. (glossary)

        Lipids are commonly known as fats, oils, and waxes.

        Proteins are compounds that consist of a chain one or more amino acids.  Proteins are used in MANY things in body development and maintanence.  Proteins are used in muscle tissue.

3) SEE TABLE 8-1 p. 125
 
Nutrient Functions Sources
Carbohydrates (sugar and starch) Supply energy for body functions Simple sugar: fruit, sweets
Starch: bread, cereals, potatoes, corn, spaghetti
Fats and Oils Supply energy; storage form of fuel in the body Margarine, butter, bacon, cooking oils, fat in meat, nuts
Proteins Growth and repair of body tissue; can supply energy only in cases of severe malnutrition, not common in Canada Meat, milk, fish, eggs, beans, peas
Water Solvent in which reactions take place; transports materials Tap water, other drinks, foods, is also a product of metabolism
Minerals:

Calcium
 

Phosphorus
 

Iron
 

Iodine

Body building; regulation of metabolism

Makes up bones and teeth; needed for normal muscle activity and blood clotting

Crucial for cell respiration ATP, makes up bones

Part of hemoglobin, hemoglobin carries oxygen in the blood

Part of thyroid hormone

Meats, milk, vegetables, fruits

Milk and dairy products, leafy vegetables, fruits

Milk and dairy products, leafy vegetables, fruits

Liver, red meat, eggs, green leafy vegetables

Sea food, iodized table salt

Vitamins:
 

A

D
 
 

C
 

B

Many serve as coenzymes in metabolic reactions.  Prevent deficiency diseases.

Growth, night vision

Strong teeth and bones, prevents rickets.  Rickets is caused from weak bones.

Keeps body tissues healthy.  Prevents scurvy

Coenzymes in cellular metabolism

Varied diet of the following
 

Fruits and vegetables

Eggs, meat, milk
 
 

Citrus fruits, tomatoes
 

Liver, eggs, milk, enriched bread, cereals

4) Digestion is the process by which food molecules are broken down.  Mechanical digestion is the cutting, chewing, grinding, crushing food into smaller pieces to increase the surface area for the chemical digestion step.  Chemical digestion is the breaking down of food molecules into smaller molecules by way of enzymes. (page 128)

5) In the mouth, food is mechanically digested by the teeth chewing and grinding.  Food is then chemically digested using enzymes in the syliva, such as amylase, which breaks down starch. (page 134)

6) An enzyme is a protein that acts as a catalyst, increasing the rate of a specific biological reaction.  Enzymes are not used up, therefore they can be reused time and time again.  (glossary of terms)

7) Peristalsis is the movement of food down the digestive tube aided by muscle contraction in the muscular walls of the alimentary canal.  The muscles in front of the food relax, while the muscles behind the food contract, pushing the food down.
When food is sufficiently chewed, it is pushed to the back of the throat (pharynx, see fig 8-9 page 136) by the tounge.  This activates a swallowing reflex that forces the food into the esophagus.  In order for the food to reach the stomach the epiglottis must close to block off the path to the lungs.  (page 137)

8) The stomach is a thick-walled, muscular sac that is coated with mucus.  Here food is mechanically broken down by the contractions of the muscular stomach walls.  Gastric juice is secreted by glands in the stomach walls for chemical digestion.   (page 136-137)

9) The small intestine is a coiled tube 6.5 metres long and 2.5 centimetres in diametre.  Digestive enzymes are secreted here.  It is called chyme, which is a mixture of bile from the liver, pancreatic juice from the pancreas, and intestinal juice from glands in the wall of the intestine.  Paristaltic movements mix the chyme with the food and also mechanically break down some of the food. (page138)

10) The pancreas secretes pancreatic juice, a digestive enzyme.  The liver creates bile, and stores it in the liver.  (page 138)

11) The small intestine can absorb any wanted molecules from the digestive track.  The small intestine has lots of surface area.  There are folds on the walls, the walls are covered with many finger called villi (see fig 8-10 page 139), on each villi are microvilli.  Absorbtion involves both diffusion and active transport.

12) The large intestine is a 1.5 metres long and 6 centimetres in diametre tube where no digestion occurs.  The large intestine reabsorbs water.  About three quartres of the water is absorbed.  The large intestine also absorbs vitamins, as well as pushing out any wastes such as cellulose, bacteria, bile, and mucus.  (page 140-141)

13) Birds have a higher metabolic rate than mammals, therefore require more food.  They also have more parts to their digestive tract than do mammals.  The food goes in the mouth (obviously), mixed with saliva, passed down the esophagus to the crop, where it is stored and softened.  From the crop it travels to the stomach part by part.  The first part of the stomach is the proventriculus where it is met with digestive enzymes.  Next it goes to the gizzard, which is the second part of the stomach.  The gizzard thick walled, muscular organ that may contain many small stones.  In the gizzard food is thoroughly mixed with gastric juices.  Next food goes to the intestine where digestion and reabsorption are completed.  Undigested food enters the rectum and leaves the body.  (page 622)

In short, the bird has an area where food is stored and softened, and it also has two parts to its stomach.

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