Heart Lab

Laboratory Exercise

We will explore and discover by delving into the intricacies of the human circulatory system. Our primary objective is to provide you with a hands-on experience that will deepen your understanding of the human body and its vital functions.

The focus of this lab session will be on the dissection of a fetal pig, which serves as an excellent model for studying human anatomy. By dissecting the thoracic cavity of the fetal pig, we will gain valuable insights into the structure and function of the heart. The heart is the central organ of the circulatory system, responsible for pumping blood and delivering essential oxygen and nutrients throughout the body.

The dissection process will involve careful and precise steps to expose the thoracic cavity and remove the heart. We will explore the external and internal structures of the heart, including the chambers, valves, and major blood vessels. By observing and examining these structures firsthand, you will develop a deep appreciation for the remarkable complexity and interconnectedness of the human cardiovascular system.

In addition to the dissection, we will also learn how to conduct an electrocardiography (ECG) to analyze the electrical activity of our own hearts. ECG is a non-invasive technique that records the electrical signals generated by the heart, providing valuable information about its rhythm and function. Through this practical exercise, you will gain insight into the diagnostic capabilities of ECG and how it is used in clinical settings.

By the end of this laboratory session, you will have acquired a comprehensive understanding of the structure and function of the human heart, as well as practical skills in dissection and ECG analysis. These skills and knowledge will serve as a solid foundation for further exploration in the field of human anatomy and physiology.

Objective

·         To gain valuable insights into the external and internal structures of the heart, including the chambers, valves, and major blood vessels.

·         To develop an appreciation for the complexity and interconnectedness of the human cardiovascular system through firsthand observation and examination of the heart's structures.

·         To learn and practice the careful and precise steps involved in the dissection process to expose the thoracic cavity and remove the heart.

·         To understand the role of the heart as the central organ of the circulatory system, responsible for pumping blood and delivering oxygen and nutrients throughout the body.

·         To learn how to conduct electrocardiography (ECG) and analyze the electrical activity of our own hearts.

Materials

·         Fetal pig (preserved)

·         Dissection tools (scissors, forceps, scalpel)

·         PPE

·         Dissection tray

·         ECG machine

·         Electrodes

·         Disposable wipes

Precautions

·         Ensure proper disposal of fetal pig and other biohazardous materials.

·         Follow safety guidelines and wear appropriate personal protective equipment (PPE) at all times.

·         Handle dissection tools carefully to prevent injury.

·         Clean and sanitize the work area before and after the dissection.

·         Maintain a respectful and professional attitude during the dissection.

Fetal Pig Dissection

1.       Prepare the work area

a.   Place the fetal pig in the dissection tray.

b.   Secure the pig using pins through its limbs.

c.        Put on gloves, goggles, and lab coats.

d.   Ensure all necessary dissection tools are available.

2.       Opening the thoracic cavity

a.   Locate the pig's sternum (breastbone) in the middle of the thoracic region.

b.   Using the scalpel, make an incision through the skin along the midline of the thorax.

c.        Make lateral incisions from the midline incision towards the limbs, creating flaps of skin.

d.   Reflect the flaps of skin to expose the underlying muscles.

3.       Cutting open the thoracic cage

a.   Identify the ribs extending from the sternum.

b.   Use the scissors to carefully cut through the ribs bilaterally, allowing access to the thoracic cavity.

c.        Set aside the cut ribs for later examination if desired.

4.       Removing the heart

a.   Locate the heart within the thoracic cavity, suspended by connective tissue and blood vessels.

b.   Identify the major vessels connected to the heart (e.g., aorta, pulmonary arteries, vena cavae).

c.        Using the scissors, carefully cut the vessels connecting the heart, one by one, ensuring minimal damage to the heart itself. Making sure the cuts are far enough way to observe each vessel attached to the heart after the heart is removed from the thoracic cavity.

d.   Gently lift the heart from the thoracic cavity and place it in a separate dissection tray.

5.       Examining the heart

a.   Observe the external structures of the heart, including its size, shape, and major blood vessels.

b.   Identify the four chambers of the heart (atria and ventricles) and the major valves (atrioventricular and semilunar).

c.        Make a frontal plane incision in the heart, starting from the apex and extending towards the base. DO NOT cut through the base, leave the base attached like the spine of a book.

d.   Observe and examine the internal structures of the heart, including the chambers, valves, and papillary muscles.

    i.      Identify the auricles, the atria, the ventricles, the tricuspid, the bicuspid, the semilunars, the chordae tendineae, and papillary muscles.   Use these structures as a guide for your drawing below.

e.   Take notes, draw diagrams, or take photographs as needed for further analysis and study.

6.       Clean-up and disposal

a.   Dispose of the fetal pig, rib bones, and other dissected tissues in a biohazard waste container.

b.   Clean and sanitize the dissection tray and tools thoroughly.

7.       Draw a dissected heart below showing all chambers, valves, and other structures (labeled), with arrows indicating the pathway of blood.

Conducting Electrocardiography (ECG)

1.       Preparation

a.   Ensure that the ECG machine is set up and calibrated according to the manufacturer's instructions.

b.   Attach the electrodes to the ECG machine, ensuring proper placement and connection.

c.        Apply a small amount of conductive gel (if required) to the electrodes for better contact.

2.       Electrode Placement

a.   Expose both of their antebrachium (forearms), where the ECG electrodes will be placed.

b.   Clean the skin on the forearm with a disposable wipe to remove any oils or dirt.

c.        Attach the electrodes in the following positions:

                                                               i.      Place the positive electrode (red lead) on the inside of the left forearm, approximately 5 cm below the antecubital fossa.

                                                             ii.      Place the negative electrode (green lead) on the inside of the right forearm, approximately 5 cm below the antecubital fossa.

                                                            iii.      Place the reference electrode (black lead) on the inside of the right wrist, just above the base of the thumb.

3.       ECG Recording

a.   Remain still and relaxed with their arms resting on the bench during the recording.  Make sure the cords are not crossing and the area is clear of devices.

b.   Start the ECG machine and ensure a clear signal is being received.

c.        Begin the recording and allow the machine to capture the ECG waveform for a specified duration (e.g., 10 seconds).

d.   Repeat the experiment to collect two sets of data per student, to ensure reliable data.

4.       Analysis and Interpretation

a.   Stop the ECG recording and review the trace on the machine or transfer the data to a computer for further analysis.

b.   Use graph paper or digital software to analyze the ECG waveform and measure relevant parameters such as heart rate, P-wave, QRS complex, and T-wave.

c.        Compare the findings with normal ECG patterns and discuss any deviations or abnormalities observed.

d.   Record the results on the tables below.

5.       Repeat steps 3 and 4, replace resting with the following tests

a.   Repeat the procedure after the student walked for 5 minutes.

b.   Repeat the procedure after the student ran/exercised for 5 minutes.

6.       Dispose of any used disposable wipes and properly store the ECG machine and electrodes according to the manufacturer's instructions.

a.   Clean and sanitize the work area, ensuring proper disposal of any biohazardous waste.

7.       Complete the table and compare results.  Complete the table by using descriptions of the ECG waves (i.e. P wave was shorter than running, QRS were closer than rest, T wave was tall, etc..)

8.       Use the R peak as a reference point and calculate the heart rate (HR).  Count the number of R peaks within 10 seconds and multiply that number by 6 to equal heart beats per minute.
Collect and compare two student’s data.

Review Questions

1.       What is the average resting heart rate of an adult human?
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2.       What is the function of the heart's valves?
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3.       How does exercise affect the heart rate?
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4.       How do heart diseases, such as coronary artery disease, affect the heart's ability to pump blood effectively?
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5.       Why is maintaining a healthy diet important for heart health?
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6.       Describe daily routines that focus on the importance of regular exercise for heart health.
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7.       What are the four chambers of the heart?
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8.       How does the heart generate its own electrical impulses?
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9.       What is an electrocardiogram (ECG) used for?
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10.    How do blood vessels and the circulatory system work together with the heart to deliver oxygen and nutrients to cells throughout the body?
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