Review of Human Physiology Practicum

IB Biology

Review of Human Physiology Practicum

Rat Dissection

Note – This activity is to be used a review of Human Physiology. Take detailed notes as to the location of structures, and provide detailed drawings or diagrams.

NB – Make sure you where gloves at all times as the preservative can be an irritant. The rats are double injected. This means that coloured dyes have been used to mark the structures, arteries and veins. Exercise caution when cutting through tissues. Cut only where instructed and when to do so. Use the correct tool to make sure you do not damage any other structures. Keep in mind the rat has many muscles and organs that are different. We will try to identify these structures in comparison to the human body.

Your data table will be like a pathological examination. Record all documentation, using correct amounts of digits, and units.

Apparatus

blunt probe, scissors, scalpel, needle probe, forceps, dissecting tray, dissecting pins, magnifying glass. ruler, dissecting microscope.

Part 1 – External Examination

1.  Put the rat on its back. Straighten the tail. Measure your rat. By examining the lower abdomen with the blunt probe, identify your rat as male or female.

2.  Take measurements of ears, limbs and girth.

Part 2 – Skinning and Incision

1.  Find the small opening on the midventral surface of the neck. At this opening, insert the point of the scissors between the skin and muscle. Make incisions following the diagram below.

2.  Using the blunt probe and your fingers, separate the skin from the underlying muscle.

3.  Using the dissecting pins, flay the skin out to the sides and pin to the dissecting tray with the pins. Retain the skin to wrap the rat to be used later.

Part 3 – Musculature and Skeletal System

1.  Take one of the upper limbs and identify the biceps brachii. Identify its origin and insertion.

2.  Take muscle and make a cross section cut, exposing the humerus. Look at the cross section of the muscle, using a magnifying glass.

3.  Cut a small piece of the muscle in cross section and take it to the microscopes available. Look at the structure under high power.

4.  Expose the humerus, taking care to not disturb the structures along the bone. Identify the artery and vein and the nerve. Measure the size of the humerus.

5.  Identify the tendon of the biceps and find a joint at the “elbow”. Identify a ligament. If you need to clean around the joint, do so.

Part 4 – The Digestive System

1.  Making shallow incisions with the scalpel use the forceps to peel the superficial abdominal muscles. These can be cut and put aside.

2.  Find the “v” in the rib cage. Pulling with the forceps, use the scissors and cut down to the anus. Make lateral cuts to make flaps of skin. Pin these back.

3.  Identify the stomach, small intestine, large intestine, colon, liver, pancreas and mesenteric veins. You can carefully pull the small intestine to the side to see other structures clearly, using the forceps and blunt probe. The caecum in the rat is quite large compared to a human.

4.  Measure the length of the small intestine, and with of the liver. Why does the rat have a large liver.

Part 5 – Cardiovascular System

1.  Insert your scissors under the rib cage. Taking care to not cut the underlying structures, pull up and cut through the rib cage, trying not to damage the diaphragm.

2.  Make a cut up to the neck, through the clavicle. Crack the ribs by pushing back. The ribs should crack at the spinal column.

3.  Identify the lungs, heart, thymus, diaphragm and trachea. Remove the lungs and thymus.

4.  Cut further up to the oral cavity and peel back the tissues and muscles. Identify the aorta, vena cava, and major veins and arteries. Remove and dissect the heart. Identify the four chambers.

5.  Carefully remove the digestive organs, leaving the kidneys intact. Identify the esophagus and the aorta and vena cava.

Part 6 – Excretory System and Genital system (Urinogenital)

1.  Find the kidneys, ureter and bladder. Take a kidney, remove it and make a cross-sectional cut. Observe.

2.  From the bladder, find the reproductive organs. Identify them.

Clean up

Put all removed organs into the carcass. Fold over the skin and place in a garbage bag. Take your tray to the sink and wash using the disinfectant provided. Wash the utensils using the same disinfectant. Dry.

Make sure your report contains all the necessary information.