CHAPTER 41

Chapter Goals:

1. Understand the structure and function of the human digestive system.

2. Define a nutrient and correctly assign the three functions of nutrients to the five classes of nutrients. Know the five classes of nutrients and the 3 categories of uses.

3. Describe the four stages of food processing in animals.

Reading assignment:

Entire chapter

Important Figures:

10-12a, 14, just the "Stomach" part of 15, 19, 20

Guide Questions/statements:

What are nutrients?

What is an essential nutrient?
Compare and contrast the old food pyramid to the new Harvard food pyramid.

How do calories used versus calories eaten relate to weight gain or loss.

Which nutrient has the most calories per gram?

What is BMR and how does it contribute to calorie usage?

Know the difference between a carnivore, an herbivore and an omnivore.

What are the advantages of: 1) sac guts over intracellular digestion, and 2) tube guts over sac guts?
What are the 4 stages of food processing?

For the mouth, stomach, small intestine and large intestine, you should be able to match which of the four stages occurs in each place. Distinguish between chemical and mechanical digestion and remember that more than one function can happen in a place.
Know the structure & main fx of the different parts of the mouth, esophagus, stomach, small intestine and large intestine. (Don't bother trying to memorize all of the enzymes and secretions - but know the main function/s of each section.)

Can you swallow food while standing on your head? Why?

What are the functions of saliva?

What are two functions of the acidic environment of the stomach?

What is acid chyme?

Which is the most basic (highest pH) part of the digestive tract? Why?

What is the main nutrient digested in the stomach?

Where does the majority of digestion take place?

Where does the majority of absorption take place?

How do the folds, villi and microvilli in the small intestine relate to absorption?

What is absorbed in the large intestine?

How can prolonged antibiotic use result in a vitamin K definiciency?
Understand that digestion, release of enzymes, acid, bicarbonate, etc., are controlled by negative feedback loops involving hormones & the nervous system.

Summary of the structure/function of the human digestive system

Mouth

Mechanical & chemical breakdown of food
Saliva - bacteria-killing NZ, & antibodies
- lube food for swallowing
- enzymes start to break down starch

Esophagus

Muscular tube propels food from the mouth to the stomach using peristalsis

Stomach

Mechanical/chemical breakdown
Acidic & pepsin = acid and enzyme digestion of proteins
Absorbs water, drugs and alcohol directly into bloodstream
Slowly releases acid chyme into small intestine

Small Intestine

Chemical breakdown with enzymes from liver, pancreas, gallbladder
Villi & microvilli = large surface area for absorption

Large Intestine

Colon = most of large intestine
-Water is absorbed
-Compact undigested bits into feces
-Bacteria synth B12, thiamine, riboflavin, & K
Rectum – feces stored until elimination

Five categories of nutrients (an essential nutrient is one that you can't make, you must get it from your diet)

Lipids

Carbohydrates

Proteins

Vitamins

Minerals

Main uses of nutrients

Energy - lipids (9C/g), carbs (4C/g), pros (4C/g, last resort for energy)

Builidng blocks - lipids, carbs, pros, minerals

Aids to metabolic reactions - mineral, vitamins

USDA Food Pyramid and Steps to a Healthier You