BIOL 1215 - Lab 7 Rat and Quail (2020 Summer) PDF

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2020 Summer

LABORATORY EXERCISE 7 VERTEBRATES: THE RAT VS. THE QUAIL

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OBJECTIVES

The objectives of this laboratory are: 1. To become familiar with the structure and functions of organ systems in the rat and the quail. 2. To understand the basic functional and anatomical similarities and differences between mammals and birds in terms of the organs and systems studied. 3. To learn and practice dissection techniques.

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INTRODUCTION

The next laboratory exercise will acquaint you with some of the major organ systems of two vertebrate animals. You will learn how to dissect and examine a number of the organs and glands belonging to each system. You will learn how to dissect and compare the anatomy of a representative of the Class Mammalia (the rat) and a representative of the Subclass Aves (the quail). You will be working in groups of four. Two students will dissect the rat and the other two will dissect the quail. We will provide you with a pair of gloves, goggles and dissecting equipment. Even though you will only dissect one animal, you are responsible for knowing the anatomy of both animals and the reproductive anatomy of both sexes for each animal. For this lab, you must be able to identify and know the functions of all the organs and body parts highlighted in bold in the lab manual. If you are not familiar with these terms, use your textbook and other resources to review this material prior to attending the lab. After you have finished your dissection, you will teach the other group about your animal. Make sure to do the following: o Make the required identifications of organs and tissues. o Compare these organs with the structures of the other animal. o See the demonstration dissections, charts, photo dissection guides and reference materials on the side display benches and at your tables. Before beginning your dissection, observe the demonstration dissections, charts, photo dissection guides and reference materials on the side display benches and at your tables.

III

DISSECTION TECHNIQUES

A short video will be shown at the beginning of the lab (also available on D2L) that shows a preview of your dissection and the techniques you will use, although we strongly recommend watching and reviewing the dissection videos before attending lab. The objective of a good dissection is to reveal organs without damaging them or altering their position in the body. Do not remove any organs from your animals, and be careful to leave all blood vessels intact so that you may study them later in the lab. Freshly-killed frozen rats and quails are supplied to eliminate exposure to potentially toxic fumes from preserved specimens.

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2020 Summer After the dissection, the specimens are donated to OWL (Orphaned Wildlife Rehabilitation Society - http://www.owlrehab.org/) to feed injured birds of prey. To start your dissection, you will not be using a scalpel. You will instead be using dissecting scissors. When using the scissors, keep the blunt end down and hold the scissors at a shallow angle to your specimen. Do not dig in when you begin your cut. Your blunt probes and forceps are used to point with and to tease apart mesenteries, and to examine organs without damaging them. Each member of your group should have a chance to practice dissection techniques, so take turns doing the work. Upon completion of your dissection and identification of structures, ask one of your instructors to check your work. IV

ANATOMICAL ORIENTATION AND TERMINOLOGY

In a four-legged animal, the following terminology is used to describe the location and position of body parts (see Figure 7.1): • • • • • •

Dorsal: toward or along the animal’s back Ventral: toward or along the animal’s belly Anterior: the front of the animal Posterior: rear of the animal Lateral: toward the animal’s side Medial: toward the animal’s middle

dorsal posterior

anterior

ventral

Figure 7.1 Anatomical Orientation of a Rat

*If you are dissecting the rat → proceed to V Rat Dissection (7-3). *If you are dissecting the quail → proceed to VI Quail Dissection (7-11)

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2020 Summer

V

RAT DISSECTION

Put on the gloves provided and obtain a rat and a plastic bag for disposal and place it in a dissecting pan, ventral side up. Massage the rat gently to help it lay flat instead of rolling to one side. Once you have started your dissection, you should continue until it is complete and you have cleaned up before viewing any slides or material on the side benches.

1. The Digestive System What is the general function of the digestive system? ____________________________________________________________________________ Using scissors, cut through the skin (not the muscle attached to the skin) from the anus to the chin. Using a blunt probe and your fingers, loosen the skin on either side of the neck, head and lower jaw. Cut from the corners of the mouth to the point of articulation of skull and jaw using your scissors. Cut through the jaw bone towards the ears. Open the mouth and examine the teeth and tongue. What types of teeth do rats have? What shape are the molars? Are they narrow or wide? Is the top surface sharp or fairly flat? __________________________________________________________________________ From the dentition alone, would you conclude that the rat is omnivorous, herbivorous, or carnivorous? Explain why. ____________________________________________________________________________ ____________________________________________________________________________ Probe the roof of the mouth to locate the hard palate and the soft palate behind it. Using scissors make a mid-ventral incision through the muscle layer from the pelvis to the sternum (breastbone). Then make a lateral incision posterior to the rib cage and anterior to the hind limbs on each side. Turn back the muscle flaps to expose the viscera (internal organs of the body cavity) in the abdominal cavity. The abdominal cavity is separated from the thoracic cavity by the diaphragm. Posterior to the diaphragm is the liver; note its deep red colour. The liver has many important functions. List three different major functions of the liver. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ The liver is made of several lobes; lift them to expose the stomach. Trace the path of food starting at the esophagus, leading into the stomach, and the cardiac sphincter at the junction of the esophagus and stomach. The anterior half of the stomach is transparent, and is called the cardiac portion. The posterior half is pink and is called the pyloric portion.

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2020 Summer Feel with your probe/fingers. Which portion is the most muscular? ____________________________________________________________________________

What function do the two portions have? Cardiac portion: _______________________________________________________________ Pyloric portion: ________________________________________________________________ Where is the pyloric sphincter? ____________________________________________________________________________ What is its function? ____________________________________________________________________________ Notice the elongated, dark coloured spleen posterior to the stomach. The spleen removes both foreign material and worn out blood cells from the blood. The small intestine is divided into three regions: duodenum, jejunum, and ileum. Spread the folds of the small intestine and note the fragile membranes called the mesentery. Examine the blood vessels in the mesentery. What is the major function of these particular blood vessels? ____________________________________________________________________________ ____________________________________________________________________________

The mammal liver produces bile, which emulsifies fat. In many mammals, bile is stored in the gall bladder. Rats lack a gall bladder but still produce bile. Why do you think the rat lacks a gall bladder? ___________________________________________________________________________ ___________________________________________________________________________ Find the pancreas, located in the mesentery posterior to the junction of the small intestine and the stomach. This red coloured collection of tissue is a critical accessory gland of the digestive system. What is the function of the pancreas? ___________________________________________________________________________ ___________________________________________________________________________ Vertebrate glands come in two types: exocrine and endocrine. What is an exocrine gland? ____________________________________________________________________________ ____________________________________________________________________________ What is an endocrine gland? ____________________________________________________________________________ ____________________________________________________________________________ 7-4

2020 Summer Is the pancreas an exocrine gland, an endocrine gland, or both? Explain. ____________________________________________________________________________ ____________________________________________________________________________ The cecum is a large thin-walled sac between the small intestine and the large intestine (colon). The cecum varies in size between different animals. In the rat, the cecum contains bacteria. What is the function of the bacteria found in the cecum? What is the purpose of the enzyme they produce? ____________________________________________________________________________ ____________________________________________________________________________

Would you expect the cecum of a carnivore to be larger or smaller than the rat’s? Explain. ____________________________________________________________________________ ____________________________________________________________________________ Trace the path of the large intestine (colon) from the cecum to the rectum and anus. What is the function of the large intestine? ____________________________________________________________________________ ____________________________________________________________________________

2. The Respiratory System What is the general function of the respiratory system? ____________________________________________________________________________ What is the difference between external respiration and internal respiration? ____________________________________________________________________________ The lungs on your rat are enclosed in pleural membranes. The respiratory movements that draw air in and out of the lungs are produced by the coordinated action of the intercostal muscles and the diaphragm. Open the rat's mouth and identify the epiglottis and glottis, which are very deep down the throat. If you haven’t already cut through the jaw bone towards the ears to find these two structures, do so now. The epiglottis is a tiny flap of tissue. After the epiglottis is found, slip a blunt probe into the glottis and gently push it down the trachea. If you have not already done so, tease apart the tissues to find the rat’s trachea.

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2020 Summer Does the trachea lie dorsal or ventral to the esophagus? ____________________________________________________________________________

Why do the cartilage rings not completely encircle the trachea? ___________________________________________________________________________

Draw the path of air through the mammalian respiratory system

Examine the slides of mammalian lung tissue under low, medium and high power. Observe bronchioles and alveoli (where gas exchange occurs)

Figure 7.2 The mammal lung 3. The Reproductive System You are responsible for both the male and female reproductive systems in both animals. Remember to view the anatomy of both sexes in the dissections of other groups on your lab bench. What is the general function of the reproductive system? ____________________________________________________________________________ ____________________________________________________________________________

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2020 Summer Male In a male embryo, the testes are found in the same area of the abdomen as the ovaries are in the female. The testes eventually migrate through an opening in the abdominal muscle wall into a sac of skin called the scrotum (scrotal sac). These openings remain open in the adult rat or human, and the testes may be withdrawn into the abdominal cavity in cases of extreme cold. See Figure 7.4 Cut through the skin on the mid-ventral surface of the scrotum to expose the testes. Find the epididymis and vas deferens, which joins the urethra. Follow one vas deferens to where it loops over the ureters and then goes behind the urinary bladder. The vas deferens receives fluid from both seminal vesicles and prostate. Move the bladder to one side and look for the entrance of the vas deferens into the urethra, just below the bladder. The urethra enters the penis. The penis of the rat contains a bone called the baculum. This bone is absent in humans but is found in many other placental mammals. It is believed to provide mechanical support during copulation.

Figure 7.3 Male Mammalian Reproductive System This work is licensed under Creative Commons Attribution-Non-Commercial-ShareAlike 4.0 License it is attributed to Biology Corner and the original version can be found at https://www.biologycorner.com/worksheets/rat_urogenital.html no changes were made.

What are the major functions of the epididymis? ____________________________________________________________________________ What is the function of the vas deferens? ____________________________________________________________________________

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2020 Summer Locate the seminal vesicles and prostate gland. What do they produce? ____________________________________________________________________________ ____________________________________________________________________________ List the structures that sperm passes through, from the testis to the penis and outside. ____________________________________________________________________________ ____________________________________________________________________________ Vasectomy is a method of male birth control. Explain how this surgery results in sterility. ____________________________________________________________________________ ____________________________________________________________________________ You will examine slides of testes after your dissection is complete. Testes Slide Testes are made up of many fine convoluted tubes called seminiferous tubules. The large rounded cells at the outer edge are diploid cells that have not gone through meiosis. They are called primary spermatocytes. Closest to the interior space, or lumen, are immature sperm, called spermatids. Between the primary spermatocytes and the spermatids are cells in different stages of meiosis, called secondary spermatocytes. Examine the slide of mammalian testes with the low, medium and high power objective lenses.

Figure 7.4 Mammalian Testes

Sketch a portion of what you see using the 4x and 40x objective lenses.

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2020 Summer Between the seminiferous tubules are groups of cells called interstitial cells. What is their function? ____________________________________________________________________________ ____________________________________________________________________________

Are these cells part of the endocrine or exocrine system? How can you tell? ____________________________________________________________________________ ____________________________________________________________________________

Indicate the interstitial cells on your previous drawing.

Female The uterus is divided into two uterine horns, like the arms of a "Y". Find the uterine horns on the rat. Why does the female rat need a Y shaped uterus? ____________________________________________________________________________ Can you think of other animals that would have the same shape of uterus? ____________________________________________________________________________

Figure 7.5 Female Mammalian Reproductive System This work is licensed under Creative Commons Attribution-Non-Commercial-ShareAlike 4.0 License it is attributed to Biology Corner and the original version can be found at https://www.biologycorner.com/worksheets/rat_urogenital.html no changes were made.

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2020 Summer On the uterus, it is often possible to see placental scars in each horn (or arm) left by the implantation of the embryos. These are small black dots inside the uterus. Counting the number of placental scars estimates the female’s reproductive success. The end of each uterine horn narrows into a small tube called the oviduct. At the other end of the oviduct, a small flared opening called the infundibulum lies adjacent to the ovary. When ovulation occurs, an egg erupts through the surface of the ovary and is pulled into the infundibulum via ciliary current within the oviduct. Describe the passage of an unfertilized egg from an ovary to the vagina. ____________________________________________________________________________ ____________________________________________________________________________

You will examine slides of ovaries after your dissection is complete Ovary Slide Examine a cross-section of rat ovary under low power. Eggs (ova) develop in sacs called follicles. Find a primary follicle, represented by a small sac with a large cell in the middle. A partially mature follicle is larger, has some fluid within the sac, and is called a secondary follicle. Mature follicles consist of a large sac containing fluid and a small egg. See Figure 7.6, and use the chart of the Female Reproductive System on display to identify these structures.

PRIMARY FOLLICLE

OVULATION: OVUM ERUPTING FROM MATURE FOLLICLE.

Figure 7.6 Mammalian Ovary What hormone does the mature follicle produce before ovulation? ____________________________________________________________________________ Identify a mature follicle. What happens to a mature follicle after ovulation? ____________________________________________________________________________ ____________________________________________________________________________

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2020 Summer What hormones does the corpus luteum produce? ____________________________________________________________________________ Sketch a primary and a mature follicle from the ovary slide as seen at 4x or 10x.

VI

QUAIL DISSECTION

Obtain a quail and a plastic disposal bag and before beginning the dissection, study the external anatomy of the quail. Examine the animal carefully. Once you have started your dissection, you should continue until it is complete and you have cleaned up before viewing any slides or material on the side benches. Notice that the quail’s body is quite compact. Since birds stand on two feet, balance is incredibly important. This is achieved through positioning the majority of its body weight directly over its feet. What external features are unique to birds? ____________________________________________________________________________ ____________________________________________________________________________ How are the external structures of birds adapted for flight? ____________________________________________________________________________ ____________________________________________________________________________ Birds are also different from mammals in that they have hollow or pneumatized bones

Figure 7.7 Bird Bone

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2020 Summer This is...