Rat Dissection Lab Guide

Name__________________________________Date__________Period __________ àààà Pre-Lab work: On the rat diagram below locate, number and identify as many anatomic landmarks, regions, directions, planes, sections and cavities as possible. Use the locator numbers on the rat diagram and write the corresponding anatomical term next to the locator number in the table provided for your choice like the example provided. Feel free to modify the drawing to suit your needs. Use extra paper if needed. Be creative! Locator Anatomical Term

1 mentis 2 3 4 5 6 7 8 9

10 11 12 13 14 15 16 17 18 19 20 21 22 23 34 25 26 27 28 29 30 31 32 33 34 35

1

Rat Dissection Lab Guide

Name__________________________________Date__________Period __________ The rat is a vertebrate, which means that many aspects of its structural organization are common with all other vertebrates, including man. Some scientists interpret the similarity of structures among related organisms as evidence for common ancestry others interpret this as evidence for a common design and thus a common designer. In a way, studying the rat is like studying a human. As the leading theme of this lab, ask yourself: for every structure observed in the rat, there is an equivalent structure in your own body - what is the structure and where is it located. As the second leading theme, pay particular attention to the relationships among organs and groups of organs. Structural parts are not "just there" in random locations. Their specific layout within the body contributes to making certain functions possible. Therefore, for every structure seen, you should determine the following:

• What organ system it belongs to? • How it is connected with other components? • What is the organ or structures general function? • What is the organ or structures specific function (if applicable)?

The specimen you will receive is a preserved double-injected specimen. Double injected refers to the arteries being filled with a red latex, and the veins being filled with blue latex. You will notice various incisions on the external surface of the rat where the latex was injected. àààà Pre-Lab work: Read the lab guide that follows. When you see a blank… (a)_____________________... following an anatomical term choose an easier to understand “replacement term” and use it to “fill in the blank”.

Rat Background Information:

Specimen Classification (complete the classification) Kingdom (a)______________ Phylum (b)______________ Subphylum (c)______________ Class (d)______________ Order Rodentia Family Muridae Weight: 10-17 oz Genus Rattus Length: 12-18 in species norvegicus Litter Size: 6-12 babies Habitat: Countryside during the warm months, buildings about 18 inches underground. Diet: seeds, nuts, vegetation, animal carcasses, berries, fruits, other animal's offspring, eggs, and trash. The common rat’s body shape is chubby, and the tail is never longer than the body and head combined, and the rat’s whiskers are sensitive to touch. The rat species comes from Southeast Asian Islands, India, Central Asia, and China before the ice age. àààà Dissection and Exploration Procedure: Dissecting tools will be used to open the body cavity of the rat and observe the structures. Keep in mind that dissecting does not mean "to cut up"; in fact, it means, "to expose to view". Careful dissecting techniques will be needed to observe all the structures and their connections to other structures. You will not need to use a scalpel. Contrary to popular belief, a scalpel is not the best tool for dissection. Scissors serve better because the point of the scissors can be pointed upwards to prevent damaging organs underneath. Always raise structures to be cut with your forceps or probes before cutting, so that you can see exactly what is underneath and where the incision should be made. Never cut more than is absolutely necessary to expose a part.

Rat Dissection Lab Guide

Name__________________________________Date__________Period __________ 1. Obtain the rat, along with a pair of scissors that you will use to cut the skin, a pair of tweezers, and several dissecting needles. Place the rat on the dissection tray, dorsal (e)______________ side down, ventral (f)______________side up. Extend and pin the palms all four feet of your specimen to the dissection tray lining. Examine your rat and notice if it is a male or female. 2. Using the scissors, pinch a piece of the rat’s anterior (g)______________ integument (h)______________, just above the vagina/scrotum/anus so that you can cut a small hole, piercing just the skin and not the abdominal (i)______________, muscles. 3. Next, make a medial (j)________________ cut starting in the superior (k)________________ direction toward the sternum (l)________________ making sure you DO NOT cut into the underling muscles or ventral body cavity (m)____________________. Once you have a small hole through the skin you can begin using a dissecting needle to separate the connective tissues, between the abdominal muscles and the dermis (n)______________. [While you are separating the integument from the muscle, you do not have to be gentle with the rat, the stomach muscle is stronger than you would think, and you can be pretty rough with this.] 4. At the superior (o)________________end and inferior (p)________________ ends of the superficial (q)________________, medial cut made in step two, cut laterally (r)________________ to the proximal joint (s)________________ of each limb. Pull the skin back as you are making your lateral (t)________________cuts. If you see brown you are cutting muscle and should start the cut over. Pull the fur/epidermis/dermis down to about 2/3 of the way to the spine on both sides and pin it down with needles and examine the muscles. [After you have separated the rat’s integument from the ventral abdominal and thoracic (u)________________ muscles, with the two flaps of skin opening up the middle of the rat, pin down the skin with the dissection needles. This will make it easier to work on the inner workings of the rat.] 5. Next, cutting along the midsagittal plane again, cut through the first and second layers of the abdominal muscles through the umbilicus (v)________________ using scissors, with the tips pointed up. Continue your cut through the medial rib cage up to the larynx (w)________________. [Fold the muscle out, just as you did the skin, and use the dissection needles to hold back the skin, and the muscle. You might need to wash out the inside of the rat with a little water. There will probably be dried up blood and other fluids that will just wash right out with little hassle.] 6. Now you should be able to see all the internal organs of the pelvic (x)________________, abdominal and thoracic cavities. Examine the contents of each cavity, exploring with the blunt nosed probe. From the superior end of your last cut identify the esophagus, heart, rt. & lf. lung, the diaphragm, ((y)________________ cavity), peritoneum, the mesenteries, the liver, the stomach, the pancreas, gall bladder, the spleen, the small intestine, the kidneys, the colon ((z)________________ cavity) and the rectum ((a’)________________ cavity). At first, try to identify as many organs as possible while making as few cuts as possible. Make believe you are doing a surgery of a living and beloved pet to remove a tumor near the right kidney! 12

1 HINT: To better view all of the internal organs, you can cut the organs from the body to see them better. If you do, first, slowly and carefully cutting the liver and stomach from the diaphragm. Then cut down along the spine (pulling up the organs as you cut, being careful to not cut the organs apart) watching that you don't cut the kidneys. Finish the cut by cutting off at the bottom of the intestine/rectum before the anus. Examine and have fun!

Rat Dissection Lab Guide

Name__________________________________Date__________Period __________

Rat Anatomy Checklist: Throughout the course of the investigation, you will need to stop and have your instructor check your progress. At each checkpoint, you should have the box initialed by your instructor to ensure adequate progress. You will turn this sheet in at the end of the investigation.

[Initials________] 1. Rat pinned, superficial integument incision made and muscles exposed. [Initials ________] 2. Abdominal muscle and rib cage incision made and muscle flaps are pinned back exposing the internal organs of the ventral body cavities. [Initials ________] 3. Remove and pin down complete alimentary canal ()___________________ in one piece. Stretch it out and make a drawing of it below with all parts labeled. Show the length of each part in centimeters. [Initials ________] 4. Open the stomach, small and large intestines and compare and contrast the contents. Describe their contents. [Initials________] 5. Find, expose and identify a kidney. Open the stomach and small intestines and compare and contrast the contents describe their contents [Initials________] 6. Make a drawing of the heart and lungs; label the heart’s chambers and rt. and lf. Lung. [Initials________] 7. Find, expose and identify the subclavian (b’)__________________, axillary (c’)_________________and carotid (d’)__________________________arteries. [Initials________] 9. Find, expose and identify the iliac (e’)____________________and femoral (f’)__________________arteries. [Initials________] 10. Find, expose and identify the organs of a system of your choice other than the digestive system. àààà [Initials________] 11. Pre-Lab Research ~ Find, expose and identify the structure in the rat’s digestive system that makes it different than from that of humans?

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Lab Day

0 pts Student did not stay on task (wrote notes, did other class homework etc). Lab partners did most of the work and clean up, engaged in horseplay

1 pts Student was engaged in the laboratory most of the time, failure to clean up station, quit too early, minor goofing around

2 pts Student was engaged in laboratory, did fair share of work, stayed on task

Day 1

Day 2

(Optional)

2 If you want to do some pre-lab study on basic rat anatomy visit http://www.utm.edu/%7Erirwin/RatAnat.htm

Rat Dissection Lab Guide

Name__________________________________Date__________Period __________

Day 3