Introduction

Year 10 Pre-Diploma Biology

Heart DissectionIntroduction

This lab practical allows you to identify and compare the size, shape and tissue type of the major chambers and vessels of the heart. The goal of the lab is not just to observe anatomy, but to associate structure with function. The heart is a pump for blood that comes into the right atrium, goes out to the lungs through the right ventricle, returns through the left atrium, and leaves again through the left ventricle - a double circulation. Each chamber is separated by valves that prevent the backflow of blood. Try and figure out where the various components are, how each works, especially how the shape, composition, and even texture of each part contribute to its function.

Preliminary Questions

1) What is the heart's surface like? What function do you think this serves?Slippery soft and slimy, to reduce friction on the body when pumping blood.

2) How does the heart muscle itself receive oxygen for respiration?Through the coronary arteries from the lungs.Observation: External AnatomyDO NOT CUT ANYTHING YET!As you follow the instructions and find each structure, label a pin and stick the pin in the structure. I must see all 10 structures before you may continue to the internal structures. 1. Identify the right and left sides of the heart. Look closely and on one side you will see a diagonal line of blood vessels that divide the heart. The half that includes all of the apex (pointed end) of the heart is the left side. Confirm this by squeezing each half of the heart. The left half will feel much firmer and more muscular than the right side.

2. Turn the heart so that the right side is on your right, as if it were in your body. Find the large opening at the top of the heart next to the right auricle (flap of darker tissue on top of the heart). This is the opening to the superior vena cava, which brings blood from the top half of the body (arms and head) to the right atrium. Carefully stick a glass rod down this vessel. You should feel it open into the right atrium. A little down and to the left of the superior vena cava there is another blood vessel opening. This is the inferior vena cava, which also leads to the right atrium, bringing blood from the lower tissues (legs and abdomen). You can also see another blood vessel next to the left auricle. This is a pulmonary vein that brings blood from the lungs into the left atrium.

3. Sticking straight up from the centre of the heart is the most muscular blood vessel you will see. This is the aorta, which takes oxygenated blood from the left ventricle to the rest of the body (the ventricles are the lower chambers of the heart). The aorta branches into more than one artery right after it leaves the heart, so it may have more than one opening on your heart specimen. Look carefully at the openings and you should be able to see that they are connected to each other.

4. Behind and to the left of the aorta there is another large vessel. This is the pulmonary artery which takes blood from the right ventricle to the lungs.

Draw simple, coloured views of the front (ventral) and a back (dorsal) external of the heart.

Ventral View

Dorsal ViewDissection: Internal Anatomy

AortaPulmonary artery

The two vena cava go into the right atrium on the other (dorsal) sideThe pulmonary vein goes into the left atrium on the dorsal side.

Coronary artery and vein

When you need to see inside the right ventricle, cut here.

When you want to open the left ventricle cut here.

1. Insert your dissecting scissors or scalpel into the superior vena cava and make an incision down through the wall of the right atrium and right ventricle. Pull the two sides apart and look for three flaps of membrane. These membranes form the tricuspid valve between the right atrium and the right ventricle. The membranes are connected to flaps of muscle called the papillary muscles by tendons called the chordae tendinae or "heartstrings." This valve allows blood to enter the ventricle from the atrium, but prevents backflow from the ventricle into the atrium.

Make observations and measurements of as many structures as you can, filling in your results table.

2. Insert a glass rod into the pulmonary artery and see it come through to the right ventricle. Make an incision down through this artery and look inside it for three small membranous pockets. These form the pulmonary semi-lunar valves which prevent blood from flowing back into the right ventricle.

3. Insert your dissecting scissors or scalpel into the left auricle at the base of the aorta and make an incision down through the wall of the left atrium and ventricle, as shown by the dotted line in the external heart picture. Locate the mitral valve (or bicuspid valve) between the left atrium and ventricle. This will have two flaps of membrane connected to papillary muscles by tendons.

Make observations and measurements of as many structures as you can, filling in your results table.

4. Insert a glass rod into the aorta and observe where it connects to the left ventricle. Make an incision up through the aorta and examine the inside carefully for three small membranous pockets. These form the aortic semi-lunar valve which prevents blood from flowing back into the left ventricle.

At this point make sure your chart is complete with measurements and observations.

Also, make sure to draw or photograph each view so you can include images in the lab report showing the structures in the table.

Include all other drawings of the internal heart structures here, stating from which side the heart is being seen and labelling all identified structures. Heart Dissection Results Table

Fill out as much of the table below as you can. Some boxes may not be relevant. Observations should include colour, texture, shape, and anything else interesting to you. StructureDiameter (mm)Wall Thickness (mm)Observations

Vena Cava151

Right AtriumCollect blood

Large (Tricuspid) valvePrevent blood from going back into the right atrium, held back by cardiac cords to prevent inversion.

Right VentriclePump blood, less muscular pumps blood a short distance to lungs.

Semi-lunar valvesKeeps blood from falling back into the right ventricle

Pulmonary Artery

Pulmonary Vein

Left AtriumCollect blood

Large (Bicuspid) valvePrevents blood from going back into left atrium, held back by cardiac cords to prevent inversion.

Left VentriclePumping blood, much more muscular to pump blood around the body.

Semi-lunar valvesKeeps blood from falling back into the left ventricle.

Aorta85

Coronary Artery and Vein

Heart Dissection Lab Report

Your lab report should consist of1. A brief Introduction to what you did and what the purpose of the lab was. What was the question you were trying to answer, or what were the goals of the lab? Be sure to specify the animal from which your heart came. 2. A Results section that includes text and drawings/photos of the steps of the dissection. In the photos, label the structures of interest. Each drawing/photo must have a caption. Also include in this section your completed tables of measurements and observations. 3. A Discussion section in which you select one major anatomical feature of the heart, e.g., the tricuspid valve (valve) or the left ventricle (chamber) or the aorta (vessel), and discuss how its function is related to its structure. Features you might include in this description are the shape, the composition and mechanical properties of the tissue, and the texture of any surfaces involved. Provide evidence from your observations, preferably numerical, for everything you claim.

ASSESSMENT

OBJECTIVE E: EXPERIMENTAL INVESTIGATION AND THE SCIENTIFIC PROCESS

Materials

Dissection kit - scissors, scalpel, forceps, etc

Drawing pencils and/or Digital CameraRubber/latex gloves

Dissection guide and results tablePig or sheep Heart

Diagram of heartDissection board

Dissection pinsGlass rod

Year 10 2014-2015 Pre-Diploma Biology Unit 1: CVD, Heart Dissection Guide