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DIGESTIVE SYSTEM Study Guide
Chapter 14 Marieb text
* = page number in Marieb textbook
Overview
1) List the organs of the alimentary canal in order from beginning to end. *412
Oral cavity  pharynx  esophagus stomach  small intestine  large intestine
2) What are the 6 major functions of the gastrointestinal tract? Briefly define each. *424-425
Ingestion: taking food into oral cavity
Propulsion: movement of food from one organ to next
Chemical digestion: breaking down food with enzymes
Mechanical digestion: breaking down food physically (ex: teeth, muscle layers in stomach)
Absorption: taking nutrients into blood
Defecation: removal of materials cannot digest
3) Name the 4 tissue layers of the GI tract from innermost to outermost, and describe the function of each.
*415-417
Mucosa: produces mucus to reduce friction
Submucosa: contains blood & nerves
Muscularis externa: layers of smooth muscle for peristalsis
Serosa: protection of organs to prevent friction
4) What is peristalsis? *424, 427
Alternating contraction and relaxation of smooth muscles to move food down digestive tract
Structure and Functions
5) What is the function of the epiglottis during swallowing? *427
Covers the airway so food doesn’t get down respiratory tract
6) Which organ of the digestive system is the longest? Why is this (what processes happen here)? *418
Small intestine
Lots of digestion and 90% of absorption happens here!
7) What is the function of the mucus secreted by glands in the stomach and small intestine? *418
To prevent friction so food can move down the digestive tract
And
*protects organs against acidic gastric juices
8) What are the three portions of the stomach? In what portion does the most digestive activity occur? *417
Fundus, body, pylorus
*most digestion happens in funnel shaped PYLORUS
9) Why does the stomach wall have 3 layers of muscle (instead of 2)? *418, 429
There are 3 layers of smooth muscle for mechanical digestion in the stomach
10) Why is the esophagus lined with stratified squamous epithelium (instead of simple columnar like the other
gastrointestinal organs)? *415
Layers of cells help to protect esophagus & prevent friction
11) Food enters the stomach from the esophagus through which valve? *416, 417
Cardioesophageal valve
12) Food enters the small intestine from the stomach through which valve? *416, 417
Pyloric valve
13) Food enters the large intestine from the small intestine through which valve? *418, 420
ileocecal valve
14) What is the location and function of the greater omentum? *418
“lacy apron” that hangs down from the greater curvature of the stomach over the intestines
15) What is the mesentery? *417
Membrane of the small intestine that connects it together and to the posterior abdominal wall
16) What are villi, where are they found, and what is their function? *419
Finger-like projections that increase the surface area of the small intestine for 90% of ABSORPTION
17) What is the first section of the small intestine, where most enzymatic secretions enter called? *418
duodenum
18) What are the major functions of the large intestine? *419-420
Water absorption
Materials that can’t be digested are defecated
19) How did the large intestine get its name and what is the major absorptive function of the large intestine?
*419
Larger in diameter
Absorbs water
20) Name at least 4 accessory organs of the digestive system and briefly describe their functions. *421-422
Liver: makes bile that breaks down fats
Gallbladder: stores bile
Pancreas: makes enzymes that break down all
organic molecule groups
Salivary glands: enzymes that break down fats and
carbohydrates
Chemical Digestion
21) What is the difference between mechanical and chemical digestion? Which organ begins both processes?
*424
Mechanical digestion is physical breakdown of food
Chemical digestion is breakdown by enzymes
Both start in ORAL CAVITY
22) What is the function of bile? Which organ produces it and which organ stores it? *421
Bile breaks down fats
Made in liver
Stored in gallbladder
23) Name the specific organ locations and enzymes (amylase, lipase, pepsin) involved in the digestion of *426
a. Carbohydrates
b. Lipids
c. Proteins
Salivary amylase (oral cavity) breaks down carbohydrates
Salivary lipase (oral cavity) breaks down fats
Pepsin in the stomach breaks down proteins
24) The stomach produces hydrochloric acid (HCl) – what is its function in digestion? *429
Activates enzymes
25) What is chyme? *418
Semi-fluid contents of the stomach – which is gastric juices mixed with food
26) What organic compound groups do secretions from the pancreas break down? What section of the small
intestine do these pancreatic secretions enter? *421
The pancreas secretes enzymes that break down all of the organic molecule groups (carbohydrates, lipids,
proteins).
The pancreas releases these enzymes into the duodenum of the small intestine.
Disorders and Diseases
27) What is heartburn? What causes this condition? *429
Heartburn is a condition when the cardioesophageal valve doesn’t close tightly and gastric juices from the
stomach backflow into the esophagus.
28) Briefly describe the following conditions:
a. jaundice *421
Bile pigments in the body cause the tissues to become yellow. This condition is due to blockage of ducts or
liver problems.
b. hepatitis *421
Inflammation of the liver.
c. cirrhosis *421
Chronic inflammatory condition in which the liver is severely damaged. This condition is almost guaranteed
when one drinks alcoholic beverages in excess for many years.
d. ulcers *428
Hole in the mucosa layer of the GI tract. When in the stomach it is called a peptic ulcer.
e. diarrhea and constipation *433
Diarrhea is a condition of watery stools, resulting when food rushes through the large intestine before water
is absorbed.
Constipation may result from lack of fiber in diet. Too much water is absorbed because food residue is in the
large intestine for a longer period of time.
29) *** PIZZA PATHWAY - Trace the pathway of a piece of pizza through the digestive tract.
 Be sure to include all ORGANS and all VALVES. (For now – you can LIST)
 Give the major FUNCTION(S) of each organ in digesting the pizza.
DIGESTIVE PATHWAY CHART
Main Functions of Organ or Name of Valve
Oral Cavity
 Food taken into oral cavity by ingestion
 Mechanical digestion by teeth
 Chemical digestion by enzymes
Pharynx
 Food bolus enters pharynx
 Passageway for both food and air
Esophagus
 This is a “food chute”
 Food moves by propulsion
Valve between Esophagus
and Stomach
 Cardioesophageal valve
Stomach
 Chemical digestion by pepsin
(enzyme that breaks down proteins)
 Mechanical digestion by 3 layers of muscularis externa
Valve between Stomach
and Small Intestine
 Pyloric valve
Small Intestine
 Majority of absorption into blood through villi
Valve between Small and
Large Intestines
 Ileocecal valve
Large Intestine
 Remaining water absorbed
 Feces eliminated through process of defecation
Diagrams to STUDY
A) Overview of Digestive System *413
B) Oral Cavity *414
C) Layers of the Gastrointestinal Tract *415
D) Stomach *416
*Short Answer “Essay” Review Questions – Page 452
Answer the following questions, in complete sentences, in the space provided below.
FOUR Questions: Short Answer Essay Questions #’s 12, #14, #20, and At the Clinic #3.
Short answer # 12)
It is necessary for the stomach contents to be so acidic because hydrochloric acid (HCl) activates enzymes.
For example, it activates pepsin to break down proteins.
The stomach is able to protect itself because the mucosa layer of the digestive tract secretes mucus.
Short answer # 14)
Fatty stools result from absence of bile and/or pancreatic juice because bile is produced in the liver and
stored in the gallbladder and its function is to chemically breakdown fats.
Pancreatic enzymes include lipase which breaks down fats. Pancreatic enzymes can break down all organic
molecule groups.
Short answer # 20)
Most nutrient absorption occurs in the small intestine which is the longest organ of the digestive tract.
About 90% of absorption happens here through the villi.
At the Clinic #3)
Gastric ulcers are holes in the mucosa layer due to acidic gastric juices that contains hydrochloric acid (HCl).
The prescribed medication promotes healing and reduces inflammation. Drugs that inhibit secretion of HCl
(like Zantac) may be prescribed.
Peptic ulcers cab produce serious complications like bleeding in digestive tract, vomiting of blood and blood
in the feces. In severe cases peritonitis or damage to nearby pancreas can result.
Potential causes of ulcers (which can also make existing ulcers worse) are smoking, alcohol, and aspirin.
Aspirin would make the ulcer worse.