Lesson 3 of 7
Objective: SWBAT complete a dissection and identify key structures in the heart.
As the students enter the room they take out their journals and respond to the prompt:
What parts of the heart should we be able to view during today's dissection? What is the function of each of those parts?
I circulate through the room while the students work on their journals. I am reading their writing and checking for their accurate use of terminology as well as accurate descriptions of the function. After the students have had some time to write, I ask for volunteers to share their journals with the class. As a volunteer shares, I have him/her point to the structure they are referring to using a heart model. This helps activate the students' prior knowledge of the topic and serves as a reminder of what the structures look like.
Before taking the students into the lab, I spend extra time reviewing proper procedures with them as well as reviewing the tools they will be using during the dissection. I explain to the students they must be careful not to cut themselves or their group members. I have the students wear aprons, goggles, and gloves when they complete the dissection and I require students with long hair to tie their hair back. These specific rules have been in place throughout the year, so they are not new to the students. I explain to the students that they will primarily be using the scalpel and the probe for this dissection and that the dissection materials should be used only when the specimen is in the dissection pan.
After reviewing the dissection information with the students, I ask them to repeat the rules back to me, sometimes multiple times, to ensure that they understand what they need to do while in the lab. If a student is not following proper procedure in the lab, that student is removed immediately, I have found that this greatly reduces off task behavior, since this is a lab the students look forward to all year.
This video provides an Overview of the materials I use during the heart dissection.
*Dissections are not for everyone, and I do not force my students to complete dissections. Please read my reflection for more information on how I use dissection alternatives with my students.
I place the students into groups of four and have them go into the lab to put on their safety gear. Once the students are seated and quiet, we begin to go over page 1 of the heart dissection. I generally read through each section with the students, use a heart to demonstrate what they need to do as a group, and then move around the room checking to see that they have accomplished the step appropriately.
I begin by explaining how to determine the left from the right side of the heart, as written on the dissection guide. I also point out the apex of the heart. I then give each group a heart. I have one student in each group hold the heart with the apex down, then they pass it to the next student who holds the heart with the apex up, then that student passes the heart to the next person in the group, etc. This is a quick way to get each of the students involved in the dissection from the beginning. I then point out the atria, using the demonstration heart. I tell the students to work within their group to determine which side is the right side of the heart as well as to identify the atria, because I will come around to ask them to identify those structures. I give the students a couple of minutes to collaborate with their group members and then I begin circulating through the room asking the groups to show me the right side of the heart and the atria.
After each group has successfully determined the right side of the heart, I demonstrate how to make the first incision, which will run from the right atrium to the right ventricle, at the apex. I check in with each of the groups and ask them to point out the various structures listed on the dissection guide. I follow the same procedure for the incision on the left side of the heart.
Once the groups have finished the dissection and have identified the necessary structures, they are able to explore the heart on their own. Many times the students will cut the heart in half completely. When they are finished exploring, the students clean up their area and finish answering the questions on page 2 of the heart dissection.
Conducting the dissection and examining the various structures of the heart and reviewing their function addresses the NGSS Cross Cutting Concept of Structure and Function while the review of the role of the heart in the circulatory system as well as the entire body addresses MS-LS1-3.
Near the end of class, I ask the groups to share out some of the structures they viewed and to explain the purpose of the structure. I am looking for the students to be able to describe the atria, the ventricles, the septum, the chordae tendonae, the aorta, and the vena cava. I also ask the students to describe the way the structures looked, as this helps them use visual cues as a reminder.