FN 225: Nutrition
Tamberly Powell, M.S., R.D.
Health Professions Division
Lane Community College
Eugene, Oregon
LECTURE 2B: Chapter 3: The Human Body: Are we really what we eat?


Diet Analysis This Week

Test next week (Week 3)
  • The exam is DUE THURSDAY of Week 3, but it will become available on Tuesday of Week 3.  The exam will be worth 50 points, and will consist of 49 multiple choice questions. You will take Exam 1 just like submitting study questions, but you won't have the questions and answers in front of you.  You will be timed.  You are expected to take this exam, by yourself, not with a partner.  You can use your book, and your notes. You will have 90 minutes to take it.  Make sure you take it at a time you will not be interrupted.  If you have to take it late, please contact me BEFORE the exam date.  Late exams must be taken in the instructional testing center (located in center building where bookstore use to be) where you are only allowed one 3x5 note card.
  • Be sure to take the Review Quiz this week (Week 2), which is intended to help improve your score on Exam 1.

 

Lecture 2B: Chapter 3


I How the human body is put together and organized

The human body is composed of billions of cells that need energy, water, other nutrients and oxygen to live and thrive.  

Cells are organized into tissues and tissues are grouped to form organs.

During this lecture, I will be comparing The Remarkable Body to The Remarkable Plant since it's plants that give us so much of what we need and we return the favor by giving them some of what they need, carbon dioxide.

As you can see with the illustration below, plants also have organs.

00plantorgans
II Body Systems
  1. Communication Systems (Hormonal and Nervous Systems)
  2. System for Digestion and Absorption
  3. The Parts of Digestion and Absorption
  4. Circulatory System
  5. Storage System
  6. Excretory System    
The overall objective of ALL of these body systems (human AND plant) is to help cells work so our body (or a plant's body) can survive and reproduce.

1.    Communication Systems (Hormonal (also referred to as endocrine) and Nervous Systems)

Hormones are chemical messengers secreted by one part of the body into the blood to tell another group of cells to do something.

For example, the hormone insulin is secreted by the pancreas when it perceives that blood sugar has risen.  

The insulin goes into blood where it travels to cells everywhere and tells the cells to take in sugar.

Our text says that "the nervous system receives and integrates information from sensory receptors all over the body--sight, hearing, touch, smell, taste and others--which communicate to the brain the state of both the outer and  inner worlds".
01vinepotato

Plants also have something like our nervous system which receives information and communicates.  Consider vines.  When the vine above realized that something was nearby that it could climb to get more access to the sun, within hours it had sent out something that could hook around that post.

Plants also have various responses to light.  The flowers of the 4 o'clock plant shown below

4:00 pm


7:30 pm

I saw the illustration below in Newsweek.

 
2.    System for Digestion and Absorption  

The overall function of this system is to get nutrients from food to cells.

From looking at the below diagram, you should be able to label where the pancreas would be in the diagram in your lecture outline.
 


Click on the following link to see a digestion animation.  There is more detail than you need to know for this class presented, but the video gives a nice overview of how food moves through the digestive tract and how the organs participate in digestion.  There will be more information on this as well later in your lecture outline.


3. THE PARTS OF DIGESTION AND ABSORPTION: Mechanical & Chemical
a.    Mechanical Aspects of Digestion. Examples:
chewing
swallowing
stomach churning
peristalsis-
a series of organized, wave-like muscle contractions that occur throughout the digestive tract and move food from one end to the other.

 

Mechanical aspects of digestion makes PHYSICAL changes to food.


b.    Chemicals that help in digestion but do NOT break apart nutrients (in other words no chemical changes are being made to the nutrients)-

i. hydrochloric acid-
What?-
acid made by the stomach

Why?
among other functions, it uncoils protein from food, making them easier to chemically be broken down.

ii. sodium bicarbonate-
What?
alkaline (basic as opposed to acidic) substance made by the pancreas

Why?
helps to neutralize the stomach acids in the chyme (the partially digested mass of food that is forced into the small intestine from the stomach)

 iii. bile-
What?
alkaline fluid made by the liver and stored in the gall bladder (the gallbladder is illustrated below in green). The gall bladder secretes bile into the small intestine when fat is present.
Why?
Emulsifies fat in chyme, which allows the fat to be divided into tiny drops that are more easily broken apart during digestion.  This is a physical change NOT a chemical change.  Bile is increasing the surface area of fat so enzymes have an easier time in chemically breaking down the fat. It would be similar to using dish soap to break up cooking grease on a pan. Below is a video demonstrating this process.  In the video the green soap (illustrating bile) is referred to as washing liquid.

 


Here is the link to the above video:  http://youtu.be/VQrtYap84zA
c.    Chemicals that DO cause nutrients to be broken apart (in other words a chemical    change is taking place): Enzymes.
Enzymes help break down and at other times they also help build.  Enzymes speed up or facilitate chemical reactions that would occur anyway.  Because of enzymes, they happen much faster.

An enzyme's name is often the same as the chemical they affect, except the enzyme name ends in "ase".  So the enzyme that breaks apart sucrose (table sugar) is sucrase.

The main chemical reaction during digestion is hydrolysis.
 
(the splitting apart of one molecule into 2 with the help of water & an enzyme)

Here is an animation that demonstrates the Enzyme Action and the Hydrolysis of Sucrose

 

d.   Absorption:

Nutrients get absorbed from the Small Intestine into Villi then into blood or lymph.

What are villi?
tiny finger-like  projections from the surface of the intestinal wall

Why are there villi?
In a December 10, 2007 Newsweek article, Patrick J. Skerrett and W. Allan Walker, an M.D., wrote "The gut is composed of the small and large intestine. Stretched out, it's as long as a school bus. Flatten out the millions of finger-like projections that line its sides and it would easily cover a tennis court."  So the villi greatly increase the surface area for absorption to take place, allowing more nutrients to be absorbed.

Here is a very cool video that shows you some real life images of the digestive tract.  It is very graphic, but amazing.

 

Here is the link to the above video: https://youtu.be/_QYwscALNng

 

I'm very impressed with the wonder that is our body, and wonders are everywhere in the natural world.




Dan Gleason, a retired University of Oregon biology professor and the author of Birds! From the Inside Out wrote the following in a Register-Guard article about chickadees (pictured above):
".... the digestive system of a chickadee changes from season to season, reflected in the change in their diet.

"Chickadees can more easily macerate and digest seeds during the winter when their gizzards are enlarged and well-developed.  Like all birds, chickadees have a two chambered stomach, with the gizzard being the muscular rear portion that thoroughly grinds seeds and hard materials.  The front portion is called the proventriculus.  It secretes digestive enzymes and acids to help digest animal material, such as insects.  As spring approaches and seeds become less available, the gizzard decreases in size and the glandular portion of the stomach enlarges, making insects easier to digest."

"The Ever-Present Chickadee"
The Register-Guard
Home & Garden Monthly
January 24, 2008

 


 
4.    Circulatory System


a.  The heart pumps blood through arteries, capillaries, and veins carrying oxygen and nutrients to the cells and removing carbon dioxide and other wastes.

b.      Blood that passes through the villi picks up water  soluble nutrients like carbohydrates, proteins, minerals, and water soluble vitamins.  

c.       Lymph that passes through the villi picks up fat and fat soluble vitamins and dumps it into the bloodstream near the heart.

d.      Blood leaving the digestive system goes to the liver which can  remove,   change   or store nutrients.  (See illustration below)

e.  Substances the cell needs have now arrived at the cell.

What happens to them now?  

They are used by the cell for energy,
as materials to build what it needs (like muscle tissue from amino acids) or
to otherwise help us function (like to see)

It's in the cells everywhere in the body that energy is released.  It's a common misconception that energy is released in the GI tract.
Plants also have a vascular system of sorts.  Glucose gets transported in phloem and water and minerals travels in xylem. (not on test)

21leafstructure


5.    Storage System

When you eat more than your body needs, what happens to the extra?

b.     Excess sugar and starch can be stored in the liver and muscle as
glycogen.
 
c.    Excess sugar and starch as well as excess fat & protein can be stored as
fat. Note:  This will only happen if total Calories are also in excess.

a.    The large intestine excretes solid waste from food (mostly fiber).

b.    The kidneys excrete wastes filtered from the blood.

c.    The lungs excrete carbon dioxide and other gases.
           
 
REVIEW:

1. Which of these are enzymes? a.  insulin                b.    lactase              c.  bile

Click here if you think insulin is an enzyme.
Click here if you think insulin is a hormone.

Click here if you think lactase is an enzyme.
Click here if you think lactase is a hormone.
Click here if you think lactase is a sugar.

Click here if you think bile is an enzyme.
Click here if you think bile is a hormone.


2. What is the difference between a hormone and an enzyme?

Hormones are chemical messengers and do not break bonds.  Enzymes help break chemical bonds.


The Study Questions for this week refer you to a section of the lecture outline called "Our Ancestor's Diet".  The figure below is another way of picturing the period of time we've been using agriculture to feed ourselves compared to the length of time human beings have been on earth using hunting and gathering to feed ourselves.





The end of Lecture 2B

































INCORRECT.  Insulin is not an enzyme.
Click here to return to Lecture.
















































INCORRECT.  Bile is not an enzyme.  Bile is an emulsifier, which is something that allows fat to be divided into tiny drops that are more easily broken apart.
Click here to return to Lecture.













































INCORRECT.  Lactase is not a hormone.
Click here to return to Lecture.









































CORRECT.  Insulin is a hormone.  It a chemical messenger secreted into the blood when the pancreas perceives that blood sugar has risen.  The blood takes it to cells everywhere telling the cells to let in sugar.
Click here to return to Lecture.







































INCORRECT.  Lactase is not a sugar.  Lactose is a sugar.
Click here to return to Lecture.

















































CORRECT.  Lactase is an enzyme.  It helps break the bonds of lactose.  It helps break one molecule of lactose into one molecule of glucose and one molecule of another sugar (called galactose, which we'll talk about in chapter 4).
Click here to return to Lecture.








































INCORRECT.  Bile is not a hormone.  Bile is an emulsifier, which is something that allows fat to be divided into tiny drops that are more easily broken apart.
Click here to return to Lecture.




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