Download Lab 06 - Blood Vessel Anatomy

Week 06 Lab
Blood Vessel Anatomy
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Identify the major arteries and veins of the feline cardiovascular system.
Compare the blood vessels of the cat with those of the human.
Compare and contrast arteries and veins microscopically.
In this lab, you will dissect the cardiovascular system of the cat and identify the major arteries and veins. In
our cats, the arteries have been filled with red latex and the veins with blue latex. Because this exercise
complements the study of the human circulatory system, be sure to note differences between the blood
vessels of the cat and those of humans.
ACTIVITY 1: Getting Ready
In Lab:
1. Clear the lab bench except for one set of directions and the review sheet for the first lab exam. The
review sheet lists what you need to know for the exam.
2. Go to the side table and select the following dissection tools:
❍ scissors
❍ scalpel
❍ forceps
❍ several blunt probes
3. Select goggles from the sterilizing cabinet and gloves from the side table. Only students who plan to
touch the cat need to wear gloves. You should all wear goggles.
4. Obtain a cat in a sealed plastic bag and a large metal dissecting pan.
5. Cut off a corner of the plastic bag and drain the excess fluid into the bucket near the sink.
6. Remove the cat from the bag and put it on the tray, ventral side up.
7. Discard the bag in the regular trash. You will be given a new bag to store the cat.
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ACTIVITY 2: Opening the Ventral Cavity
In Lab:
1. Using the sharp point of the scissors, cut into the cat’s skin and underlying
musculature starting just above the pubic bone at the midline of the body. See
the accompanying figure on the right.
2. Cut along the midsagittal line to the diaphragm. Make lateral cuts at the point of
incision and just below the diaphragm so you can open up the abdominopelvic
cavity.
3. Continue the cut up through the thorax, angling toward the right or left to avoid
the cat’s sternum. Above the sternum return the cut to the midline. Cut high up
into the area under the cat’s jaw.
4. Make lateral cuts just above the diaphragm to open up the thoracic cavity.
ACTIVITY 3: Initial Organ Identification
In Lab:
1. In the thoracic cavity, you should be able to identify:
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thymus gland (large mass of tissue on the
anterior trachea and heart)
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trachea
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esophagus (deep to the trachea)
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lungs
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heart
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diaphragm
2. In the abdominopelvic cavity, you should be
able to identify:
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greater omentum (fatty covering on the
abdominal organs; do NOT remove this,
just push it aside)
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liver (large organ just below the diaphragm)
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stomach (to the left of the liver)
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small intestine (small diameter)
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large intestine (large diameter)
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spleen (large lymphatic system organ
usually to the left and a bit below the
stomach)
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ACTIVITY 4: Blood Vessels of the Cat
In Lab:
1. Using a blunt probe, push aside connective tissue to identify the right and left common carotid arteries
running parallel to the trachea.
2. Identify the small internal jugular veins next to the common carotid arteries. This is not present in some
cats.
3. Identify the large white vagus nerves that run along the common carotid arteries
4. Remove the pericardium from the heart and identify the aorta and the pulmonary trunk.
5. Follow the aorta and locate the large brachiocephalic artery and the left subclavian artery.
6. Pushing aside connective tissue, locate the three major branches of the brachiocephalic artery: the right
subclavian artery and the right and left common carotid arteries.
7. Push the lungs aside on the left and move connective tissue aside to see the aortic arch and the
descending thoracic aorta
8. Identify the precava or superior vena cava and postcava or inferior vena cava on the right side of the
heart.
9. The postcava travels through the diaphragm into the abdominal cavity. Follow the precava until it
branches to form the right and left brachiocephalic veins.
10. Follow a brachiocephalic vein to the branch of the large external jugular vein and the subclavian vein.
11. In the abdominal cavity, push aside the intestines and, using the blunt probe, dissect out the postcava
and the abdominal aorta. Notice the branches on both carrying blood from and to the viscera.
12. Continue the dissection to reveal the external and internal iliac arteries and the common, external, and
internal iliac veins.
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ACTIVITY 5: Cleaning Up
When you are finished:
1. Make sure that you don’t have any dissecting tools on the cat tray. Wash and dry the tools, and put them
back in the tool tray. DO NOT LEAVE TOOLS IN THE WASH BASIN OR BY THE SINK.
2. Close up the cat to prevent the internal organs from drying out. We will use these cats several more
times throughout the semester, so we need it to last.
3. Discard any cat waste in the large biohazard bin in the prep room. Only put biological waste in this bin;
no gloves or paper towels! (They go in the regular trash.)
4. Slide the cat and its tray into a fresh storage bag. Use a tag tie to close up the bag and put your group’s
names or initials on the tag. Return your cat to our lab’s cat cart.
5. Use the disinfectant spray to clean your lab bench. Paper towels go in the regular trash.
6. Wash your hands at the back sink.
ACTIVITY 6: Blood Vessel Histology
The walls of the body's blood vessels have three layers. The tunica externa is a layer of connective tissue that
anchors the vessel to surrounding tissues. Collagen and elastic fibers give this layer strength and flexibility.
The tunica media is a layer of smooth muscle tissue. In the tunica media of arteries are elastic fibers that
allow the vessels to stretch and recoil in response to blood pressure changes. Veins have fewer elastic fibers;
collagen fibers in the tunica media provide strength. Lining the inside of the vessels is the third layer, the
tunica intima, a thin layer of simple squamous epithelium called endothelium. In arteries, the luminal
surface of the endothelium has a thick, dark-staining internal elastic membrane.
Because blood pressure is much higher in arteries than in veins and also because the pressure fluctuates
more in arteries than in veins, the walls of arteries are thicker than those of veins. Notice how the artery
cross section in the micrograph of Figure 1 is round and thick walled, whereas the adjacent vein is
irregularly shaped and thin walled. In a slide preparation, the tunica intima of an artery may appear pleated
because the vessel wall has recoiled due to a loss of pressure. In reality, the luminal surface is smooth and
the vessel can expand and shrink to regulate blood flow.
Veins have a thinner wall than arteries. The walls of a vein collapse if the vessel is emptied of blood. Blood
pressure is low in veins; and to prevent backflow, the peripheral veins have valves that keep blood flowing in
one direction, toward the heart.
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In Lab:
1. Place the artery/vein slide on the microscope stage and locate the artery and vein at low magnification.
Most slide preparations have one artery, an adjacent vein, and a nerve. The blood vessels are hollow and
most likely have blood cells in the lumen. The nerve appears as a round, solid structure.
2. Increase the magnification to high and compare each arterial layer with its venous counterpart.
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