Lewis/Life - Teaching Techniques

Chapter 35 - Teaching Techniques

A. General Tips
** See the General Tips notes in Chapter 30 of this Instructor's Manual.
You might wish to copy and distribute to your students the Overview of Chapter Objectives flowchart found at the beginning of this Instructor's Manual Chapter.
B. Possible Approaches to the Chapter
Understand the chapter well yourself. You might consider starting with a pre-test of the human system. Many high schools do stress circulatory components and your students may have a decent understanding of this topic.
I have included a number of challenge points in the sections below. Use these or other challenge ideas to spark additional interest in the circulatory system. This is an especially valid idea if your class does have a fairly solid foundation in basic circulatory concepts.
C. Hints Related to Specific Chapter Topics
- I. Note the mention of diffusion in the legend to Figure 35.1. Keep in mind that diffusion, or a tendency toward equilibrium, is the background reason why we have circulatory systems. Large organisms are too big for effective or efficient diffusion to take place.
- I.A. To discuss the differences between the open and the closed circulatory systems, I suggest you compare Figures 35.2a and 35.2b. Some students will have the mistaken idea that an open system is somehow disorganized, that blood is flowing every which way. The spaces found in the open system are quite specific. These spaces vary with the given species. There is also a tendency to think of an open system as rather inefficient. If this system were really inefficient, we wouldn't be in the present "Age of Insects!"
  Remind the students that just because a system is closed, it doesn't mean that nothing enters or leaves. Obviously gases, nutrients, and wastes all enter and leave. The point is that the system has a continuous blood vessel pathway.
  Stress the sequence: Heart->artery->arteriole-> capillary->venule->vein->heart. This sequence is valid for both pulmonary and systemic circulation.
  You may have a student who wants to argue whether annelids have five hearts, ten hearts, or one heart divided into several separate chambers. It is all a matter of semantics.
- I.B. Relate respiratory pigments to the meaning of respiration found in Unit 2.
- I.C. Figure 35.3 is good for explaining the basic concept of the vertebrate circulatory systems. Relate this to Figure 35.2b. The three chambered heart is not shown in Figure 35.3. If your students have any questions, challenge them to find out why the three chambered heart actually is a very efficient mechanism for the amphibians and reptiles.
  The crocodilians actually have a four chambered heart with a shunt between the left and right ventricles. The functionality of this foramen Panizzae depends on the environment.
- II.A. Blood typing is mentioned on pages 273 and 796 of the text.
- II.A.2.b. Note that leukemias is a plural word because there are several types of leukemia. There are specific problems connected with each of the leukemias.
  When the white blood cells die and death from infection occurs shortly thereafter, the source of the bacteria is often the normal flora. Many of these organisms are opportunistic.
- II.A.2.c. The vesicles in the megakaryocyte are formed from the Golgi apparatus.
  Some students have mistakenly learned that platelets are "mini-cells." This is not true. Another misconception is that the platelets come from an "exploded cell." The platelets are the result of packets that "bud off" from the megakaryocyte. There is no explosion.
- II.B.4. As a challenge, ask the students to look up the origin of the sinoatrial node.
  Ask why the name of the atrioventricular node makes sense.
  Note the reference to Figure 35.14. The question is how much of it you are going to teach. This topic doesn't "skim over" very well. I suggest you make a decision about how much you want your students to be responsible for.
- II.C.2. When you discuss the capillaries, note the reference to Figure 35.18. Point out that the little strips of tissue around some of the capillaries are tiny smooth muscle cells. These cells regulate the blood flow from the thoroughfares into the particular capillaries.
- II.C.3. Point out the venous valves and ask why good muscle tone aids circulation.
- II.E. If you do not cover blood pressure in the lab, bring a sphygmomanometer to lecture to demonstrate exactly what is happening when a person's blood pressure is taken.
- III. This is an interesting section but you will have to make a decision on how much of it you would like to teach. Some of your students will have trouble with this material. Refer to your course objectives.
- IV. The lymphatic system is sometimes thought of as the forgotten system. Elephantiasis is mentioned but this is not the only interesting disease involving the lymphatic system.