Chapter 24 Reading Questions
The Digestive System

Let's experience Allen Ginsberg's "A Supermarket In California" as a chapter overview

What thoughts I have of you tonight, Walt Whitman, for I walked down the side streets under the trees with a headache self-conscious looking at the full moon.
In my hungry fatigue, and shopping for images, I went into the neon fruit supermarket dreaming of your enumerations!
What peaches and what penumbras! Whole families shopping at night! Aisles full of husbands! Wives in the avocadoes, babies in the tomatoes! and you, Garcia Lorea, what were you doing down by the watermelons?
I saw you, Walt Whitman, childless, lonely old grubber, poking among the meats in the refrigerator and eyeing the grocery boys.
I heard you asking questions of each: Who killed the pork chops? What price bananas? Are you my Angel?
I wandered in and out of the brilliant stacks of cans following you and followed in my imagination by the store detective.
We strode down the open corridors together in our solitary fancy tasting artichokes, possessing every frozen delicacy, and never passing the cashier.

(Allen Ginsberg is a poet of the 60's who actually coined the term "flower power". His outrageous poetry imitates the lengthy and sensitive style of Walt Whitman.)

Part 1: Mechanical and chemical digestion
    A. Histology of the digestive tract
    B. Structures of the oral cavity
   

1. We are lucky in America to have well stocked supermarkets. This food is not in a form suitable to maintain the body. This is the work of the digestive system. To start this chapter, compare mechanical and chemical digestion.

2. Compare the structure and the function of the four layers of the digestive tract.
Your digestive system is a 26 foot long tube, yes, you are a tube within a tube.
The walls of this tube are made up of four layers:

1. the mucosa
2. the submucosa
3. the muscularis
4. the serosa

Match these layers with the descriptions below:

____________________________ This layer contains epithelial tissue and an
underlying supporting connective tissue called the lamina propria.
____________________________ This layer contains an inner circular and an
outer longitudinal layer of smooth muscle
____________________________ This layer is also known as the visceral peritoneum.
____________________________ This layer extends beyond the organs to form
the mesentery, and greater omentum.
____________________________ This is the supporting layer containing glands,
nerves, blood, and lymphatic vessels.

3. List three extensions of the peritoneum.

1. ________________________________________
2. ________________________________________
3. ________________________________________

4. Identify the three sets of salivary glands and their position in the head.

A. Identify the largest salivary gland._____________________________
B. Identify the salivary gland that becomes infected with the mumps virus.
    ______________________________________________________
C. Identify the salivary gland that is found on the posterior floor of the mouth.                               
     ______________________________________________________
D. Identify the salivary gland under the tongue that secretes mostly mucus.
    _______________________________________________________

5. The mouth begins the digestion of watermelons, tomatoes, peaches, and frozen delicacies. Open wide and say Aah! While you are at this, label the oral cavity with the following:

lingual frenulum
hard palate
vestibule
palatine tonsil
uvula
soft palate
tongue
fauces
Wharton's duct
teeth

6. List the contents and functions of saliva. A Russian physiologist named Ivan Petrovich Pavlov studied salivation in dogs and found this to be a conditioned reflex. (My golden retriever never would have made Pavlov's experiment successful as she is always salivating.) You secrete up to 1500 mls of saliva a day. Explain why there is a continuous production and not a conditioned reflex in man.

__________________________________________________________________________________________________________________________

As you read the section on the contents of saliva, list them below and describe their functions.

7. Let's study the name, number, time of eruption, and function of the pearls in your oral
cavity that must last a lifetime. Fill in the columns with the appropriate information below.

(Did you feel wiser when your wisdom teeth permanently erupted?)

8. At birth your mouth was germ free, within a few days microorganisms established
themselves in the warm, moist, dark folds of the oral cavity. From that time on, the
alternate wetting and drying on the surfaces of the teeth causes solidification and
attachment of debris called dental plaque. The next step in this process is dental caries.
Describe the process of tooth decay.
________________________________________________________ ________________________________________________________ ________________________________________________________ ________________________________________________________
(If you an remove rust from a nail with coca cola, imagine what happens to the enamel of your teeth.)

9. Briefly describe mechanical and chemical digestion in the mouth.
__________________________________________________
__________________________________________________
__________________________________________________
__________________________________________________

10. Describe the features of the esophagus. Behind the trachea is a collapsible,
23 cm muscular tube called the esophagus. You may call it the forgotten tube
because every student forgets its position.

    A. Does digestion occur in the esophagus? ______
    B. Identify the function of the esophagus._____________________________________
    C. Explain why food enters the esophagus rather than the larynx.
         _____________________________________________________________
         _____________________________________________________________
    D. The esophagus pierces the muscular diaphragm in an opening called the                 
         _____________________________________________________________.
    (Note: the inguinal canal pierces the abdominal wall, can there be another type of hernia?)
    E. Explain the role of the muscular layers during esophageal swallowing.
         ______________________________________________________
         ______________________________________________________
         ______________________________________________________

11. There are two abnormalities of the gastroesophageal sphincter, achalasia and heartburn.
Choose the one you would like least to have and list the causes and symptoms below.
________________________________________________________________
________________________________________________________________
________________________________________________________________

Part 2: Stomach Anatomy and Function
    A. Gross and microscopic stomach anatomy
    B. Three stages of gastric secretion

12. The stomach digests the pork chops and all that protein. The esophagus empties
its contents into this "food bag." To study the  gross anatomy of the stomach, list the
parts of the stomach in the order in which food passes.

1. ___________________-->
2. ___________________-->
3. ___________________-->
4. ___________________

The stomach is a J-shaped food bag, and is capable of holding your Thanksgiving dinner.
The medial border is called the _________________________________________,
while the lateral border is referred to as the _________________________________.

Attached to the stomach are extensions of the peritoneum called the greater and lesser omentum.
If the greater omentum is attached to the _______________________________, then the
lesser omentum is attached to the ______________________________________.

13. Describe the histology of the stomach mucosa.
    A. The ability of the stomach to distend is due to folds called _________.
    B. The mucosa is lined with _____________________________ cells.
    C. These cells are arranged into microscopic folds which reach down deep into
         the mucosa as structures called ______________________.
    D. At the bottom of these pits are four types of cells. Since food remains in the stomach
         for up to three hours, the secretions of these cells can really work on the food you eat.
         In the table below, list the cells, their secretions. and the functions of the gastric juices they secrete.

14. State two reasons why the stomach does not self digest while it is hydrolyzing proteins into peptides.
        1._______________________________________________________
        2.______________________________________________________                                    

15. Describe the three phases of gastric secretion controlled by the nervous and endocrine system.

A.     The initiation of gastric secretion can be called the  cephalic phase. List the events that         
        occur in this stage.

1.____________________________________________________________
2.____________________________________________________________
3.____________________________________________________________

B.     The continuation of gastric secretions is called the gastric phase. In this phase the hormone          gastrin is secreted.
         List the events that occur in this stage due to gastrin secretion.

1. _________________________________________________________
2. _________________________________________________________
3. _________________________________________________________
4. _________________________________________________________

        Name the factor that inhibits the release of gastrin ______________

C.    Once food enters the small intestine, the gastric secretions are inhibited, this is called                 
        the intestinal phase. A reflex and three hormones secreted by the duodenum are responsible for 
        this phase. Identify these four factors and list their functions below:

16. Perfect Pete has a peptic ulcer. List the three causes.

1. ______________________________________
2. ______________________________________
3. ______________________________________

A drug on the market called Tagamet promotes the healing of ulcers. Tagamet
inhibits HCl secretion that is stimulated by food, histamine, gastrin, caffeine, and insulin.

Focus Question
Explain the relationship between gastric secretions and the three phases,
cephalic, gastric, and intestinal that control the activity of the stomach.