Observe the effects of atherosclerosis on the coronary artery lumen

Transcription

1 Clumps and Bumps: A Look at Atherosclerosis Activity 4B Activity Description This activity features actual photomicrographs of coronary artery disease in young people aged years. Students will observe the image of coronary artery cross sections and use a unit square grid to estimate the amount of open space (), available for blood flow (see Figure 1). They will notice the in some of the blood vessels has been reduced as a result of atherosclerosis. Students will then infer what might happen to the heart muscle supplied by these arteries. This activity will provide student background information for a more in-depth study of the development of atherosclerosis. Objectives Using a unit square grid and photomicrographs of coronary arteries, the student will be able to: Label the parts of a typical artery Observe the effects of atherosclerosis on the coronary artery Infer the effects of atherosclerosis on blood flow Describe what may happen when blood flow to specific parts of the body is restricted Activity Background: Atherosclerosis (ath-er-o-skle-ro-sis) is the hardening and narrowing of arteries. It is a slow, progressive disease that starts in childhood. It is caused by the slow buildup of plaque (plak) inside the walls of our arteries. Arteries are blood vessels that carry oxygen-rich blood away from the heart to other parts of the body. The coronary arteries are small blood vessels that carry oxygen-rich blood to the heart muscle itself, supplying food and oxygen needed to keep our hearts beating. (Note: the pulmonary arteries carry oxygen-poor blood away from the heart to the lungs). 1

2 Plaque is made up of fat, cholesterol, calcium, and other substances found in blood. The presence of oxidized LDL (low density lipoprotein) activates scavenger white blood cells, called macrophages. The macro-phages begin to ingest as much of the oxidized LDL as possible and change into foam cells as a result. The newly formed foam cells begin releasing signals that initiate an immune response in the body. The buildup of plaque inside the walls of an artery narrows the inner diameter of that artery and, in time, may restrict blood flow. Plaque can be hard and stable or soft and unstable. Hard plaque causes artery walls to thicken and harden. Soft plaque is more likely to break away from the walls and enter the bloodstream. This can cause a blood clot that can partially or totally block the flow of blood in the artery. When this happens, the organ supplied by the blocked artery starves for blood and oxygen. The organ s cells may either die or suffer severe damage. Atherosclerosis can affect the arteries of the brain, heart, kidneys, and the arms and legs. As plaque builds up, it can cause serious diseases and complications. These include: Coronary artery disease Angina pectoris Heart attack Sudden death Cerebrovascular disease Transient ischemic attack (TIA) or mini strokes Stroke Peripheral arterial disease When atherosclerosis is in the early stages, the size of plaques in arterial walls can be reduced by eating a healthy diet and exercising regularly. However, once atherosclerosis reaches advanced stages, arteries will be permanently damaged in spite of diet and exercise. Background retrieved and modified from the National Heart Lung and Blood website on April 14, Atherosclerosis_WhatIs.html 2

3 PHOTOMICROGRAPH PAGE Figure 1 Layers of a Typical Artery close-up of Intima Photomicrograph courtesy of PDAY Funded by the National Heart, Lung, and Blood Institute NCT Intima inner layer of endothelial cells embedded in extracellular matrix 2. Adventitia outer most variable layer with dense fibroelastic connective tissue, nutrient vessels, and nerves 3. Media separated from by elastic lamina and has smooth muscle cells, elastic laminae, bundles of collagen fibers, and elastic fibrils all embedded in extracellular matrix 4. Lumen channel through which blood flows 3

4 Figure 2, Labeled Coronary Artery Cross Sections Cross Section 1 Typical Coronary Artery fibrous cap plaque Cross Section 2 Coronary Artery (24 Year Old Female) 4 Photomicrograph courtesy of PDAY Funded by the National Heart, Lung, and Blood Institute NCT

5 Figure 2, Labeled Coronary Artery Cross Sections, continued Cross Section 3 Coronary Artery (15 Year Old Male) fibrous cap plaque fibrous cap plaque Cross Section 4 Coronary Artery (18 Year Old Male) Photomicrograph courtesy of PDAY Funded by the National Heart, Lung, and Blood Institute NCT

6 Activity Materials: (Per student) 1 Copy of Student Data Page 1 Copy of Student Activity Page per group if students work in groups Transparency Marker or Wax Pencil Transparency print of the Unit Square Grid on page 20 or graph paper Activity Management Suggestions Using either a document camera or a projector, show students Figure 1, Layers of a Typical Artery and Figure 2 Labeled Coronary Artery Cross Sections to help them label the parts of the coronary artery pictures. (Both of these figures are found in the Teacher Pages of this activity.) Extensions Students can repeat the procedure using a smaller grid to compare the accuracy of their estimate. Also, students can use ratio and proportion to determine actual size of objects under various magnifications. Activity References Used Makowski, L. & Hotamisligil, G. S. (2004). Fatty acid binding proteins The evolutionary crossroads of inflammatory and metabolic responses. The American Society for Nutritional Sciences Journal of Nutrition, 134, 2464S-2468S. McGill, H.C. & McMahan, A.C. (1998). Determinants of atherosclerosis in the young. American Journal of Cardiology, 82, 30T-36T. McGill, H.C., et.al. (2000). Origin of atherosclerosis in childhood and adolescence. American Journal of Clinical Nutrition, 72, 1307S-15S. McGill, H.C. & McMahan, A.C. (2003). Starting earlier to prevent heart disease. Journal of American Medical Association, 290, McGill, H.C., et.al. (1995). Relation of glycohemoglobin and adiposity to atherosclerosis in youth. Arteriosclerosis, Thrombosis, and Vascular Biology,15, McGill, H.C., et.al. (2002). Obesity accelerates the progressing of coronary atherosclerosis in young men. Circulation, 105, McGill, H.C., et. al. (1997). Effects of serum lipoproteins and smoking onatherosclerosis in young men and women. Arteriosclerosis, Thrombosis,and Vascular Biology, 17,

7 McGill, et.al. (2001). Effects of non lipid risk factors on atherosclerosis in youth with a favorable lipoprotein profile. Circulation, 103, Stary, H.C. (1999). Atlas of atherosclerosis progression and regression. New York: The Parthenon Publishing Group. Websites Used Dorland s Medical Dictionary. (2002). Retrieved April 20, 2005 from Merckmedicus Website: Medline Plus. Retrieved April 20, 3005 from National Institutes of HealthWebsite: Background retrieved April 14, 2005 from National Heart Lung and Blood website: Atherosclerosis_WhatIs.html UTHSCSA Faculty Mentors Dr. Henry McGill, M.D. Professor Emeritus, Department of Pathology The University of Texas Health Science Center at San Antonio Senior Scientist Emeritus Department of Physiology and Medicine Southwest Foundation for Biomedical Research Dr. Alex McMahan, PhD Professor, Department Pathology The University of Texas Health Science Center at San Antonio Dr. Paula Shireman, M.D. Assistant Professor, Department of Surgery The University of Texas Health Science Center at San Antonio Note: All photomicrographs in this activity were provided courtesy of the Pathobiological Determinants of Atherosclerosis in Youth (PDAY) study, funded by the National Heart, Lung, and Blood Institute (NCT ). The PDAY study began in June, 1985 as a multi-center, observational study to characterize the extent of atherosclerosis in aortas and coronary arteries of young people. 7