Digestive System

For GC 1135 – General College – Murray Jensen


Overview – Introduction


The primary function of the digestive system is to take “food” and transform it into a form that can be absorbed by the blood.  There are two key terms here:  transform and absorb.  There are two major types of transformations (or, types of digestion) in the digestive system: physical digestion and chemical digestion.  Physical digestion is the process of transforming large particles, such as a whole carrot, into smaller particles, small particles of carrots.  Chewing is the best example of physical digestion- taking large particles and breaking down via teeth and chewing (the technical term for chewing is mastication (think of the masseter muscle)).  The key event in physical digestion is increasing the surface area of the food so as to quicken the second form of digestion – chemical digestion.  Chemical digestion is the processes of taking large molecules, such as proteins and starch, and transforming them into smaller particles, such as amino acids and monosaccharides (you should know what these are.). A key items in chemical transformations is enzymes – protein particles that help facilitate chemical reactions. 


The second key term mention above is absorption.  Absorption is the process of particles moving across the walls of the digestive system and into the blood – such as monosaccharides and amino acids moving from the digestive system into the blood.  It’s important to note that the digestive system has NOTHING to do with changing food into ATP or energy– that’s the job of the cells.  The digestive system takes food and transforms it into particles that can be absorbed into the blood – that’s about it .. except of the additional functions mentioned on the first page of the chapter in your book. 


Basic Anatomy:

The digestive system can be divided into two parts: a tube for the food to slide through (called either the gastro intestinal (GI) tract, or the alimentary canal) and then the glands that secrete “stuff” into the tract.  “Stuff” is usually either enzymes or other things that aid in digestion.  You have probably heard of most parts of the alimentary canal: here they are listed in order from proximal to distal:

Mouth (oral cavity) - pharynx – esophagus – stomach – small intestine – large intestine


Each of the above items can be further divided into more specific regions, but the above list is a good start.  In total, the tract is about 30 feet long, with the small intestine being the longest single segment.  (Of course “30 feet” is just an average – different books will have different numbers, and different people will have different lengths.)   Another rather strange point, but very important to physiology, is that the contents of the alimentary canal are technically “outside” the body.  Small particles, such as amino acids and monosaccharides, are able to move from the outside to the inside of the body when they move across the walls the digestive system and into the blood.


Major glands for the digestive system include: salivary glands, liver (largest gland in the body), and pancreas.


Use your text book to answer the following questions: (Digestive system chapter)


1.  List the five functions of the digestive system.




2.  What is the function and location of the peritoneum?  Does “food” go through it?



3.  What is mastication? 



4.  Where can you find the following: bolus, chyme, and feces. 



5.  What is peristalsis (peristaltic waves?)  Question: can you drink water standing on your head?  How does the water move from your mouth to your stomach – gravity?


6.  What are the three parts of the small intestine?  (list from proximal to distal – in reference to the mouth or stomach)


7   What is the location and function of a villus? 


8.  Make a drawing of the large intestine and label the following parts: ascending, transverse, descending, and sigmoid colon, rectum and anal canal.


9.  Make a drawing of the entire digestive system and label the following parts:  mouth, pharynx, esophagus, stomach, duodenum, jejunum, ileum, colon (name the specific parts of the colon.)  Web Anatomy has several exercises that can help you with learning the gross anatomy of the digestive system. 


Important: Make a drawing of the large intestine (colon) and label the following parts: ascending colon, transverse colon, descending colon, Sigmoid colon, and rectum.


Again, web anatomy can help – Digestive System



10.  Where do the following glands connect to the alimentary canal?  Liver, pancreas, and salivary glands.


11.  What is the function and location of the following enzymes?  What glands produce them?


Salivary amylase


Bile salts (not really an enzyme – it’s more of a “soap”)

Pancreatic amylase

Pancreatic lipase.


12.  Use Figure 16.23 (page 477) to answer the following questions?

- Where in the digestive system does carbohydrate digestive begin?  What enzyme is involved?



- Where in the digestive system does protein digestion begin?  What enzymes is involved


- Where in the digestive system does lipid digestion begin?  What enzyme is involved? ?  (Remember, is bile a real enzyme?)



13.  Figure 16.28 (page 483) – in what part of the digestive system do you find the highest quantity of water absorption?  (Clue: villus)




Now you will have to use the Internet:  (This is very quick)

Go to this web site and surf around a bit.  Answer the following questions based on information from this web site



(There will probably be a link on the “weekly schedule / Oi!” page.


One “teaspoon” will represent how many grams or sugar?


List the following soda pops from “highest sugar” to “lowest sugar” contents.

1.  Mountain Dew

2.  Orange Slice

3.  Pepsi

4.  Coke


Key questions:  How many grams of extra sugar (such as the sugar in soda pop) is recommended maximum per day?  (RDI:   Recommended Daily Intake)  


If you drink one can of Mountain Dew, how much more “extra sugar” should you have in one day to reach your “recommended daily intake?”




A few example questions you might see on the next test:


Which of the following list the correct order of the colon?

A)  transverse colon, ascending colon, descending colon, Sigmoid colon, rectum

B)  descending colon, ascending colon, transverse colon, Sigmoid colon, rectum

C)  ascending colon, transverse colon, descending colon, Sigmoid colon, rectum

D)  rectum, ascending colon, transverse colon, descending colon, Sigmoid colon

E)  none of the above are correct


After the stomach, the correct sequence for the segments of the small intestine are

A.   duodenum, ileum, jejunum. 

B.   duodenum, jejunum, ileum. 

C.   jejunum, duodenum, ileum. 

D.   jejunum, ileum, duodenum. 


HOMEWORK:  Answer the following questions:  1.  Where can you find bolus, chyme and feces (locations within the GI Tract).  2.  What is the primary function of the Digestive System?  3.  What is the largest section of the GI Track?  How does this relate to question #2?  4.  What is the function of salivary amylase, pepsin, and pancreatic lipase? - where are they found?  what do they do?  5.  Where do you find villi (villus)?  What is its function?  7. List the parts of the GI track in correct order.  8.  Are the liver, gall bladder, and pancreas a part of the GI Track?  Are they parts of the Digestive System?  Explain.