WEEK 2
INGESTION, DIGESTION, EXCRETION
SEPTEMBER 20-24, 2004
Learning objectives:
1. Be able to identify all of the external features, digestive organs, and excretory structures of the
fetal pig.
2. Become familiar with the functions of each of these anatomical parts.
3. Determine the gender of your pig, and all of the external features that distinguish males and
females.
4. Learn the structures that are involved in swallowing food and the function of each of these
structures in this process.
5. Identify some of the tissues that make up the esophagus, pancreas, and small intestine.
6. Compare the anatomy and function of the digestive systems in three animal groups: Vertebrata
(pig), Arthropoda (crayfish), and Annelida (earthworm).
Discussion questions:
1. What is the phylum of the pig? How does the body plan of the pig differ from the body plans of
the earthworm and the crayfish? How is it similar?
2. Why is the digestive system divided into so many different compartments? That is, why can’t
digestion be completed in a single structure?
3. Explain the following statement: “Food doesn’t really enter your body until it is absorbed by
your intestinal epithelia.”
4. When you ingest a meal, what ends up in feces and what ends up in urine?
5. What is the primary function of the excretory system?
6. What is the primary function of the digestive system?
Readings:
Fetal Pig Dissection Guide (available at the bookstore), Ch. 1, 4, and 7.
Campbell et al. 6th edition, pp. 857-868, and 939-951.
fall 2004, Lab 2-1
LAB OVERVIEW
The Big Picture:
Last week you dissected an earthworm (Phylum Annelida) and a
crayfish (Phylum Arthropoda). This week you will begin dissecting a fetal
pig (Phylum Chordata, Subphylum Vertebrata). You will have a chance
to compare the body plans and the digestive systems of these three
animal taxa.
Before lab
Main part of lab
During lab
Assignment for this lab
Today is the first weekly pre-lab quiz.
To prepare, attend recitation lecture and read:
 lab handout
 Chapters 1, 4, and 7 in dissection manual
 Assigned textbook pages
With a partner, begin dissecting a fetal pig. Follow your dissection
manual, and do a careful study of the external anatomy (Ch. 1)
followed by dissection of the digestive (Ch. 4) and excretory systems
(Ch. 7).

Using your notes, sketches, and worksheets from last week,
complete Worksheet 1 comparing body plans and digestive
systems across three animal groups.

Examine prepared slides of esophagus and small intestine and
complete Worksheet 2.
Hand in your two worksheets, including your written answers to the
questions, at the beginning of lab next week. (You can use the reverse
side of the worksheets to write your answers). For this lab and all
labs, be sure to review material periodically in anticipation of the lab
practical midterm. Your graded worksheets will be an excellent tool
for this review.
fall 2004, Lab 2-2
BACKGROUND READING
This lab exercise will examine the digestive and excretory systems of animals. You will use the fetal
pig as a model system for three reasons: (1) it shares many anatomical features with other mammals,
(2) it is relatively inexpensive, and (3) it is abundant. When female pigs are killed for human
consumption, fetuses are either thrown out or sold to biological supply companies. Barnard
purchased your fetal pigs from one such biological supply company.
As you do the fetal pig dissection, follow the pages in the chapters cited below in A Dissection Guide
& Atlas to the Fetal Pig, by D.G. Smith and M.P. Schenk. You are responsible for the information
presented in chapters 1 (external anatomy), 4 (digestive system), and 7 (excretory system only). Use
the photos and discussion presented in each of these chapters to guide you through your dissection.
Further, use the keys provided below to determine the structures for which you are responsible.
A word of caution before you begin
You will use the same fetal pig in this and next week’s lab. The success of next week’s exercise will
depend to a large extent on how carefully you work today. If you destroy the animal’s delicate
organs, you will have a lot of trouble recognizing them next week. Remember, the practical exam in
this course will require you to identify many of these anatomical structures by eye. Work carefully,
as though you were a surgeon, so as to preserve each structure’s original appearance.
ANATOMICAL STRUCTURES YOU SHOULD BE ABLE TO IDENTIFY:
Chapter 1: External Anatomy
Eyes
Ears
Nares
Vibrissae
Digits
Umbilical Cord
Mammary Papillae
Anus
Urogenital Opening
Genital Papilla
Scrotal Sacs
Chapter 4: Digestive System
Teeth
Hard Palate
Soft Palate
Nasopharynx
Glottis
Epiglottis
Tongue
Papillae
Esophagus
Stomach
Liver
Gallbladder
Common Bile Duct
Pancreas
Small intestine
Large intestine
Ileum
Anus
Chapter 7: Excretory system
Kidney (cortex, medulla, renal pelvis)
Nephron
Ureter
Urinary bladder
Urethra
Urogenital opening
fall 2004, Lab 2-3
Name______________________________Day/Time/Instructor______________________________
BC Bio 2003
Fall 2004
LAB 2, WORKSHEET 1: COMPARISON OF THREE ANIMAL GROUPS
COMPARATIVE ANATOMY OF INVERTEBRATES AND VERTEBRATES
Comparative Anatomy Invertebrates & Vertebrates – Digestive Systems
One-way
or twoway?
Number of
chambers?
Arthropoda
What is
organism’s
diet?
Noteworthy specializations
completed during last week’s lab
Annelida
Chordata
(Vertebrate
= Pig)
Consider the ratio of digestive system length to body length. For which group is the ratio
largest? What reasons can you give for variation in this ratio? (answer on an attached
sheet with your name on it; ½ page maximum)
Comparative Anatomy of Invertebrates & Vertebrates – Body Plans
Symmetry
Arthropoda
Annelida
Tissue grade
Coelom
completed during last week’s lab
Chordata
(Vertebrate
= Pig)
fall 2004, Lab 2-4
Development
BC Bio 2003
Fall 2003
LAB 2, WORKSHEET 1: COMPARISON OF THREE ANIMAL GROUPS
Arthropoda
(Crayfish)
Comparative Anatomy of Invertebrates and Vertebrates
Major Tissue or Organ Systems
Repetition or
specialization of
body parts?
Annelida
(Earthworm)
completed during last
week’s lab
System for
movement and
support?
Organs for gas
exchange?
Organs for
circulating O2?
Cephalization;
nerve cord
position?
Hermaphrodite or
separate m/f?
fall 2004, Lab 2-5
Chordata
(Vertebrate=pig)
PLEASE CLEAN UP ALL DISSECTION MATERIALS BEFORE
GETTING OUT A MICROSCOPE TO CONTINUE LAB
HISTOLOGY SLIDES
During this lab and those of the next two weeks, we will be examining several mammalian organs at
the tissue level. Initially, this may seem somewhat confusing, but you will see that there are general
patterns based on only four types: (1) epithelial tissue, (2) connective tissue, (3) muscle tissue, and
(4) nervous tissue.
Today, you will examine prepared slides showing two different structures in the mammalian digestive
system, the esophagus and the small intestine. Many structures can be delineated and named, but you
should focus on two. First, understanding the structure and function of the innermost layer lining the
lumen of the gut. This will introduce you to some of the variation in epithelial tissue. You should
also examine the structure of the muscle tissue surrounding the gut and how it is involved in
peristalsis.
Make the required sketches and answer the questions on Worksheet 2, which is at the beginning of
lab next week.
fall 2004, Lab 2-6
Esophagus
The esophagus connects the oral cavity to the stomach, transporting substances that may be quite
challenging to living tissue (e.g., hot liquid, crusty bread, fish bones).
The inner lining of the esophagus must resist abrasion; it does not digest or absorb. It is a very thick
protective layer composed of stratified squamous epithelial cells (E).
There is significant muscle tissue involved in the process of peristalsis, waves of muscle contraction
along the length of the esophagus. The inner layer of muscle is arranged in a circular fashion (labeled
CM on the diagram below); the outer layer is arranged longitudinally (labeled LM).
inside of esophagus
Longitudinally
arranged
muscle tissue
(LM)
Circularly
arranged
muscle tissue
(CM)
fall 2004, Lab 2-7
stratified
squamous
epithelial
cells (E)
Small intestine
This organ is actively involved in digesting and absorbing food. At low magnification you should be able
to see that the lining of the intestine facing the lumen of the gut is extensively folded. This gives the
structure an enormous surface area. These projections into the lumen of the gut are called villi (labeled
V). Specialized columnar epithelial cells line the surfaces of these villi, and the cells have many
microscopic microvilli projecting into the lumen of the gut; the entire structure is referred to as the brush
border. The epithelial cells lining the gut secrete enzymes involved in digestion, and some of the final
steps in digestion occur as dissolved sugars are absorbed across the cell membrane.
Since peristalsis continues along the entire length of the gut, you should be able to observe an inner layer
of circularly arranged smooth muscle tissue (CM) and an outer layer of longitudinally arranged smooth
muscle tissue (LM), just as in the esophagus.*
microvillus
(microvilli, plural)
stratified
columnar
epithelial
cells (E)
villus (villi,
plural)
inside of intestine
outside of intestine
Name______________________________Day/Time/Instructor______________________________
BC Bio 2003
Fall 2003
LAB 2, WORKSHEET 2: ESOPHAGUS AND SMALL INTESTINE HISTOLOGY
Longitudinally
arranged
muscle tissue
(LM)
Circularly
arranged
muscle tissue
(CM)
Images are from Wheater’s Functional Histology (Barbara Young and John W. Heath, 2000, Churchill Livingston,
Edinburgh).
*
fall 2004, Lab 2-8
Name __________________________Day/Time/Instructor _________________________________
BC Bio 2003
Fall 2004
LAB 2, WORKSHEET 2: ESOPHAGUS AND SMALL INTESTINE HISTOLOGY
Examine prepared slides of esophagus
and small intestine and draw labeled
sketches in the space provided.
Esophagus
Label the stratified squamous epithelial cells
lining the lumen, as well as the layers of
circularly arranged and longitudinally arranged
smooth muscle (CM and LM).
1. How does the structure of the stratified
squamous epithelial cells related to their
function?
Small Intestine
Your labels should identify the villi and
microvilli as well as the layers of circularly
arranged and longitudinally arranged smooth
muscle (CM and LM).
2. How does the structure of inner layer of the
small intestine relate to organ function?
fall 2004, Lab 2-9
GENERAL END-OF-LAB PROCEDURES
You have now finished your second laboratory exercise. However, you are NOT yet ready to leave the lab. You
won’t be reminded of these things at the end of future labs, but please remember that you will always be responsible
for cleaning up after yourself. Before you go:
 Complete and turn in your worksheets to your instructor.
 Remember that there will soon be another section taught in your lab room. Please return everything to
where you found it so that the next students can carry their labs out as efficiently as possible.
Clean up your lab bench:
o
Return materials to where you got them from during lab.
o
Put any pre-prepared microscope slides you have used back where you found them. NEVER leave
microscope slides on the stage of the microscope.
o
For any microscope slides you have personally prepared, dispose of the slides and coverslips in
the GLASS DISPOSAL BOX (not in the garbage). Do not dispose of pre-prepared slides.
o
Clean the objectives on your microscope with lens cleaner and lens paper ONLY.
o
If other parts of microscope have gotten dirty during use, please clean and dry it appropriately (ask
your instructor if you aren’t sure what to do). If it is not working properly, please notify your lab
instructor so that it can be repaired as soon as possible. Put your microscope away (always with
the scanning objective in place).
o
Dispose of any solutions down the drain (unless specified otherwise). Do not dispose of solids
down the drain; please put them in the trash.
o
Throw away any garbage you have generated. Remember that all dissection waste needs to go in
the BIOHAZARD WASTE containers.
o
Place used glassware in labeled containers.
o
Rinse off your dissection instruments and trays and return them to the appropriate locations.
o
Wipe off your lab bench and push in your chair.
 If you have any questions regarding the lab or other procedures, please feel free to ask your instructor or
Karolin Rafalski or Margaret Olney in the Biology Laboratory Office (Altschul 911, 854-2153).
fall 2004, Lab 2-10