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.
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 / Today is the first weekly pre-lab quiz.To prepare, attend recitation lecture and read:
ü lab handout
ü Chapters 1, 4, and 7 in dissection manual
ü Assigned textbook pages
Main part of lab / 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).
During lab / · 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.
Assignment for this lab / 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.
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
fall 2004, Lab 2-1
Eyes
Ears
Nares
Vibrissae
Digits
Umbilical Cord
Mammary Papillae
Anus
Urogenital Opening
Genital Papilla
Scrotal Sacs
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Chapter 4: Digestive System
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Teeth
Hard Palate
Soft Palate
Nasopharynx
Glottis
Epiglottis
Tongue
Papillae
Esophagus
Stomach
Liver
Gallbladder
Common Bile Duct
Pancreas
Small intestine
Large intestine
Ileum
Anus
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Chapter 7: Excretory system
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Kidney (cortex, medulla, renal pelvis)
Nephron
Ureter
Urinary bladder
Urethra
Urogenital opening
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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 SystemsOne-way
or two-way? / Number of chambers? / What is organism’s diet? / Noteworthy specializations
Arthropoda / 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 PlansSymmetry
/ Tissue grade / Coelom / DevelopmentArthropoda / completed during last week’s lab
Annelida
Chordata (Vertebrate = Pig)
fall 2004, Lab 2-1
BC Bio 2003 Fall 2003
LAB 2, WORKSHEET 1: COMPARISON OF THREE ANIMAL GROUPS
Comparative Anatomy of Invertebrates and VertebratesMajor Tissue or Organ Systems / Arthropoda
(Crayfish) / Annelida
(Earthworm) / Chordata
(Vertebrate=pig)
Repetition or specialization of body parts? / 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?
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.
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).
fall 2004, Lab 2-1
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.[*]
Name______Day/Time/Instructor______
BC Bio 2003 Fall 2003
LAB 2, WORKSHEET 2: ESOPHAGUS AND SMALL INTESTINE HISTOLOGY
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?
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:
v Complete and turn in your worksheets to your instructor.
v 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.
v 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 2-1
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[*] Images are from Wheater’s Functional Histology (Barbara Young and John W. Heath, 2000, Churchill Livingston, Edinburgh).