Bio: Yvonne Nevarez is an 8th grade Chicago Public School Life Science Teacher at Richardson Middle School. Graduate of Saint Xavier's University with a major in Education and a minor in Psychology, Yvonne received her Master's degree in Science Education from the Illinois Institute of Technology.
NARRATIVE: AMAZING TEACHING MOMENT
Lesson: Sheep heart dissection
My lesson was taught to eighth grade students on the structures of the heart. Furthermore, how structure is determined by its function. Students will dissect a sheep’s heart because it is similar to a human’s heart. The heart has four chambers. Two upper chambers named right and left atrium, and two lower chambers named right and left ventricle. The heart has blood vessels that are connected to the heart. Oxygenated blood leaves the left ventricle through the Aortic Valve , and out the Aorta, the largest artery, to provide the entire body’s (head to toe) cells with oxygen. As blood travels through the body’s circulatory system delivering oxygen and nutrients, it picks up waste and carbon dioxide. The blood high in carbon dioxide returns in veins back to the right side of the heart through the Superior and Inferior Vena Cava into the right atrium. Then, this deoxygenated blood leaves the right atrium, passing through the Tricuspid Valve, which closes to keep the blood flowing in one direction into the right ventricle , through the Pulmonic Valve and out the Pulmonary Artery to the lungs to drop off the carbon dioxide for the body to exhale. A fresh supply of oxygen is inhaled and picked up by blood in the Pulmonary Veins to return to the left side of the heart, carrying oxygenated blood into the left atrium, passing through the Mitral Valve, into the left ventricle, and then this cycle will continue incessantly for the entirety of a person’s life.
My students have learned the background information provided above in previous hands-on activities, readings, and videos. This lesson will allow them to see the actual structures of the heart and the effects of it’s functions.
I made sure to state that the importance of ethics in science is to be respectful of its subjects. Furthermore, we would only be making specific incisions and in no way would we be mutilating the heart in any way. Make sure to ask students if anyone is allergic to latex because we will be using latex gloves as we are dissecting the sheep hearts.
After materials are passed out, I begin to ask students a set a questions to check for knowledge recall along with questions that will require making inferences, such as:
- What are the names of the four chambers?
- What are the names of the blood vessels?
- Where does the left side of the heart pump blood to?
- Where does the right side of the heart pump blood to?
- What is purpose of the valves in the heart?
Before the students begin their dissections, they make observations of the heart and record what they see and feel. Many students struggle to identify the floppy looking sacs as the atria and are very surprised that these structures are the right and left atrium. The students, in groups of 4, then begin the dissection. They begin their incisions from the top of the atria all the way to the bottom of the heart through the ventricles. Make sure as a safety measure that only 1 person is using the scissors and holding the heart to make the incision: NO ONE ELSE SHOULD TO AVOID BEING CUT. After incisions are made, students can see the inside of the heart and will be able to compare and contrast the right side of the heart vs. the left side of the heart. At this point they are able to attempt to identify the four chambers, valves, and blood vessels. I will be circulating from table to table to ask students to identify the structures and to ask
- How does the function of each side affect the structure of left side vs. the right side of the heart? What is your evidence?
Students should be able to notice the difference in the thickness of the ventricle walls. The students should be able to identify the left side of the heart as to having thicker ventricle walls because the left side of the heart “works” harder as it has a greater distance to pump oxygenated blood to the entire body. In comparison to the right side of the heart, the right ventricle walls are much thinner because the right side of the heart only pumps deoxygenated blood to the lungs which is a much shorter distance than the entire body.
The students record their findings and return to a whole class discussion, and share their enthusiasm about how different the structures actually look compared to their two-dimensional diagrams they’ve been studying from. What truly made this an amazing lesson was the fact that all the students were engaged, they used vocabulary and actively participated in discussion about the structure and functions of the heart and their observations with an incredible amount of enthusiasm. I was so proud of my students as they were biologists in action making discoveries and reflections!
My amazingSTEM teaching moment is one of my students' favorite lessons every school year. This lesson has ALL the students engaged, participating, questioning, discussing and drawing conclusions. It is wonderful to see all the students smiling and so excited before, during, and after a lesson: this is the lesson that definitely does just that!
Hashtags: #8thgrade #LifeScience #heart, #dissection #getyourhandsdirty, #sheepheartdissection #lambheartdissection
Hashtags: #8thgrade #LifeScience #heart, #dissection #getyourhandsdirty, #sheepheartdissection #lambheartdissection