Grade11 life sciences practical task


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This document shows demonstration of a heart dissection, if the teacher wishes to this practical he/she should moderate the learners so that they don't hurt themselves

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Grade11 life sciences practical task

  1. 1. Grade11 Life sciences Practical taskInstructions1. Read the given reader below and understand it so that you may answer the questionsthat will follow bellow.2. Answer each question’s; don’t leave any question unanswered if you do so you will bepenalised.3. If you didn’t write the work you will get zero and you won’t do the practical in class.4. After the practical you will submit your work in class.5. This practical will also prepare you for the exam that is about to come in NovemberPractical 1: Dissection of a sheep heartHeart Dissection Walk Through :The heart dissection is probably one of the most difficult dissections you will do. Part of thereason it is so difficult to learn is that the heart is not perfectly symmetrical, but it is so close thatit becomes difficult to discern which side you are looking at (dorsal, ventral, left or right). Findingthe vessels is directly related to being able to orient the heart correctly and figuring out whichside you are looking at.The heart is also difficult because the fatty tissue that surrounds the heart can obscure theopenings to the vessels. This means that you really must experience the heart with your handsand feel your way to find the openings. Many people will be squeamish about this, and becausethe heart is slippery, it is easy to drop. Dont be shy with the heart; use your fingers to feel yourway through the dissection.1. Step One: OrientationWhen you first remove your heart from the bag, you will see a lot of fatty tissue surrounding it. Itis usually a waste of time to try to remove this tissue. You may also want to arm yourself withsome kind of markers for the parts you find, colour pencils work great to identify a vessel andyou will see many used to mark openings on the heart.There are a few clues to help you figure out the left and the right side, but often the packagingand preserving process can cause the heart to be misshapen. If you are lucky, the heart will benicely preserved and you will see that the front (ventral) side of the heart has a couple of keyfeatures:1) a large pulmonary trunk(artery) that extends off the top of it2) the flaps of the auricles covering the top of the atria.3) thecurve of the entire front side, whereas the backside is much flatter.
  2. 2. Side of the heart Back of the heartAuricle flap of the heartStep 2: Locate the AortaUse your fingers to probe around the top of the heart. Four major vessels can be found enteringthe heart:the pulmonary trunk (artery),aorta,superior vena cava, and thepulmonary vein.Remember that if you are looking at the back of the heart, then the right and left sides are thesame as your right and left hand.If you find the pulmonary artery, the aorta should be situated a little bit behind it. It may becovered by fat, so use your fingers to poke around until you find the opening. Push your fingerall the way in and you will feel inside of the left ventricle. The left ventricle has a very thickwall, unlike the right ventricle. Insert your finger through the pulmonary artery to feel theright ventricle and you will notice and feel that it is much thinner than the left side of the heart.
  3. 3. With your fingers or probes in the aorta and the pulmonary trunk/artery you should notice thatthey criss-cross each other, with the pulmonary trunk in the front.At this point, you may want to use your colored pencils to mark these vessels so that you dontget them confused when you are searching for the other two openings that top of the heart.Step 3: Locate the VeinsThe two major veins that enter the heart can be found on the backside, as both enter theatria. On the left side, you should be able to find the opening of the pulmonary vein as itenters the left atrium. The superior vena cava enters the right atrium. In many preservedhearts, the heart was cut at these points, so you wont see the vessels themselves, you will justfind the openings. Again, use your fingers to feel around the heart to find the openings. If youvemarked the aorta and pulmonary artery then you wont mistake them for the veins you arelooking for. This picture shows all of the vessels labeled.Sometimes, the aorta still has its branches attached to it. There are three vessels that branchfrom the aorta:
  4. 4. the brachiocephalic,left common carotid and theleftsubclavian.The majority of the time, these vessels are not visible because the aorta was cut too close to themain part of the heart when the heart was removed from the animal.Step 4: Make the IncisionsNow that you have all of the vessels located and marked, you can now open the heart to viewthe inner chambers. Use the superior vena cava and pulmonary vein as guides for where tocut. You are basically going to be cutting each side of the heart so that you can look inside. Theheart below is marked to show you where the two incisions should be made.Step 5: Viewing the ChambersAt this point it is helpful to have two hands, one to hold the heart apart so you can take a peakinside of it and another to use a probe to locate the specific parts. Your colour pencils you usedto mark the heart in step 2 can also now be used to see where those vessels connect within the
  5. 5. heart. For instance, the aorta pencil can now be seen ending in the left ventricle. You can alsonow see how much thicker the walls of the left ventricle are compared to the right ventricle.The other obvious structures seen within the heart are the chordae tendonae which areattached to papillary muscles. These tendons hold the heart valves in place, sometimes theyare called the "heartstrings". The valves were probably cut when the heart was opened, but ifyou follow the "cords" they should lead you to a thin flap that is the atrioventricular (bicuspid)valve. You can find a similar valve on the right side of the heart (tricuspid).
  6. 6. Close-up of valve with chordae t
  7. 7. 1) Match the terms in Column A with the descriptions in Column B. Place the letter of yourChoice in the space provided. Use your textbook for a reference source if needed.(20)Column A COLUMN BA. Aorta 1. Prevents blood backflow from left ventricleto left atriumB. Aortic Semilunar Valve 2. Transports blood to left lungsC. Bicuspid (mitral) Valve 3. Returns venous blood from coronary systemto right atriumD. Chordae Tendineae 4. Major artery leading from left ventricleE. Inferior Vena Cava 5. Major vein leading into lower right atriumF. Left Atrium 6. Major vein leading into upper right atriumG. Left Pulmonary Artery 7. Prevents blood backflow from aorta to leftventricleH. Left Ventricle 8. Pumps blood to pulmonary arteryI. Myocardium 9. Major artery leading from right ventricleJ. Coronary Arteries 10. Pumps blood to left ventricleK. Coronary Sinus 11. Major veins leading into left atriumL. Papillary Muscles 12. Prevents blood backflow from rightventricle to right atriumM. Pulmonary Artery (trunk) 13. Attach cuspid valve cusps to papillarymusclesN. Pulmonic Semilunar Valve 14. Pumps blood to right ventricleO. Pulmonary Veins 15. Transport blood from aorta to cardiacmusclesP. Right Atrium 16. Anchor sites for the chordae tendineaeQ. Right Ventricle 17. Pumps blood to aortaR. Superior Vena Cava 18. Myocardium that separates the twoventriclesS. Tricuspid Valve 19. Prevents blood backflow from pulmonaryartery to right ventricle.T. Ventricular Septum 20. Muscle wall of the heart2) Draw and label a diagram the structure of the human heart showing the properarrangement or location of EACH of the following structures:A) right and left atria;B) right and left ventricles;C) superior and inferior vena cava;D) pulmonary veins;E) pulmonary artery;F) aorta;G) pulmonic and aortic semilunar valves; and,H) bicuspid/mitral and tricuspid valves.Use arrows to indicate the pathway of blood into, through, and out of the heart you havedrawn. (17)
  8. 8. 3) Respectively, are the pulmonary arteries and pulmonary veins oxygen rich OR oxygenpoor?(2)4) Which chamber of the heart functions as the receiving chamber for pulmonic blood?(1)5) Which chamber of the heart functions as the muscular pump for pulmonic circulation?(1)6) Respectively, are the systemic arteries and systemic veins oxygen rich OR oxygenpoor? (2)7) Which chamber of the heart functions as the receiving chamber for systemic blood?(1)8) Which chamber of the heart functions as the muscular pump for systemic circulation?(1)AUTHENTIC1. opportunity to collaborate2. provide opportunity for the learners to reflect3. it provide the real world relevance4. it ill-defined, requiring learners to define the task and subtask needed to complete theiractivity5. seamlessly integrated with assessment