A/P II Lab Practical 3

Where in the body is the heart located?

Thoracic Cavity —> Mediastium —> Pericardial Cabity

• Located between lungs, posterior to the sternum, anterior to vertebral column, and superior (above) the diaphragm.

What protective layers cover the heart? List them from outermost to innermost order.

• Pericardium: Epicardium

• Myocardium

• Endocardium

List the composition and role of the epicardium protective heart layer.

• Outermost Layer

• Composition: Adipose CT

• Role: Protection

List the composition and role of the myocardium protective heart layer.

• Middle Layer

• Composition: Muscle Cells

• Role: Contractions

List the composition and role of the endocardium protective heart layer.

• Innermost Layer

• Composition: Connective Tissue

• Role: Lines Inner Chambers

What is the fibrous cardiac skeleton? What roles does it have in heart anatomy/function?

• Def: Interlacing bundles tethered/grouped together by crisscrossing connective tissue fiber…makeup the cardiac skelton.

• Role: Provides needed…

  • Support for Constant Contraction

  • Reinforcement Around Valves

  • Resistance to generate muscle force.

  • Conduction Guidance in Heart Cycle

How many chambers does the human heart have?

Four

What are atria? How many are there in the heart? What is their role?

• Def: Chambers of the heart where blood ENTERS the heart.

• Two Atria

What are ventricles? How many are there in the heart? What is their role?

• Def: Chambers of the heart that contract to pump blood OUT of the heart.

• Two Ventricles

Which chambers carry oxygenated blood? Which chambers carry deoxygenated blood?

• Oxygenated: Left Side

  • Left Atrium

  • Left Ventricle

• Deoxygenated: Right Side

  • Right Atrium

  • Right Ventricle

What is the systemic circuit? Which heart chambers serve the systemic circuit?

• Def: The circuit of blood vessels that goes from heart to organs/tissues to heart.

• Served:

  • Right Atria - low-O2 blood returns from systemic circuit.

  • Left Ventricle - high-O2 blood sent to the systemic circuit.

What is the pulmonary circuit? Which heart chambers serve the pulmonary circuit?

• Def: The circuit of blood vessels that goes from the heart to lungs and heart.

• Note:

  • Veins: High-Oxygen

  • Arteries: Low-Oxygen

• Served:

  • Left Atria - high-O2 blood returns from pulmonary circuit.

  • Right Ventricle - low-O2 blood sent to pulmonary circuit.

What is the coronary circuit? Why is it needed? Which heart chambers connect to the coronary circuit?

• Def: A separate circuit that supplies oxygen to heart muscle tissue.

• It is needed because although the heart is continuously full of blood, cells do not get their oxygen from the chambers.

• Connected To:

  • Left Coronary Artery (leaves Aorta)

  • Right Coronary Artery (leaves Aorta)

  • Coronary Sinus (enters Right Atrium)

Which “great vessels” connect to which chambers?

The great vessels include:

• Ascending Aorta

• Pulmonary Trunk

• Pulmonary Veins

• Superior- & Inferior-Vena Cavas

Connect to:

• Ascending Aorta —> Left Ventricle out to Systemic Circuit.

• Pulmonary Trunk —> Right Ventricle out to Pulmonary Circuit.

• Pulmonary Veins —> Left Atrium; bringing high-O2 blood.

• Superior & Inferior Vena Cava —> Right Atrium; bringing low-O2 blood.

Which heart chamber has the thickest myocardium? Why?

• Left Ventricle

• Because it has to push blood through the larger systemic circuit, ensuring sufficient blood flow to all body tissues.

What is the function of the papillary muscles and the chordae tendineae?

Prevents eversion of AV valves, stopping backward blood flow into atria.

What is the fossa ovalis? What defects can be associated with it?

• Def: A depression or shallow indentation located in the interatrial septum of the heart, specifically in the right atrium.

• Remnant of: Fetal Foramen Ovale

• Defect: Patent Foraemn Ovale

  • When the foramen ovale fails to close properly after birth, leaving a small opening between the right and left atria…persists until adulthood.

What is the ligamentum arteriosum? What is it a remnant of?

• Def: A small, fibrous band of tissue located between the pulmonary artery and the aortic arch in the adult heart. It plays no active role in circulation after birth but is an important remnant of fetal circulation.

• Remanant of: Fetal Ductus Arteriosus

• Defect: Patent Ductus Arteriosus

Which valves open as ventricles contract?

• Aortic Semilunar Valves

• Pulmonary Semilunar Valves

Into what chamber does the following vessel dump its blood: Coronary Sinus

Drains deoxygenated blood from the heart muscle to the right atrium.

Into what chamber does the following vessel dump its blood: Superior- & Inferior Vena Cava

• SVC: Returns deoxygenated blood from the upper body to the right atrium.

• IVC: returns deoxygenated blood from the lower body to the right atrium.

Into what chamber does the following vessel dump its blood: Pulmonary Veins

Carry oxygenated blood from the lungs to the left atrium.

Into what chamber does the following vessel dump its blood: Pulmonary Arteries

Carries deoxygenated blood from the right ventricle to the lung.

Into what chamber does the following vessel dump its blood: Aorta

Carries oxygenated blood from the left ventricle to the body.

Into what chamber does the following vessel dump its blood: Coronary Arteries

Supplies oxygenated blood to the heart muscle.

Which coronary artery usually gives rise to nodal arteries that supply both the SA and AV nodes?

Right Coronary Artery—-contains pacemaker cells that trigger APs (trigger heartbeat).

To what vessel do all of the coronary veins return blood? Where does this vessel empty the blood?

• Coronary Sinus

• Empties blood into the right atrium of the heart.

What is the intrinsic cardiac conduction network?

The intrinsic cardiac conduction network is a specialized network of cells that conduct action potentials throughout the heart to ensure coordinated contraction.

Describe how action potentials control the cardiac cycle as they move through this network.

• SA Node: The SA node generates an action potential, which spreads through the atria, causing atrial contraction (P wave in ECG).

• AV Node: After a brief delay at the AV node, the action potential moves down the Bundle of His to the ventricles, causing ventricular contraction (QRS complex).

• AV Bundle & Purkinje Fibers: These structures rapidly transmit the action potential throughout the ventricles, ensuring coordinated contraction and efficient pumping.

Define: Pacemaker Cells

Specialized cardiac muscle cells that depolarize without external stimulation and help regulate the heart's rhythm. The primary pacemaker cells are located in the SA node.

Describe how ECG/EKG waves “match-up” with action potential moving through the heart.

• P wave: Corresponds to atrial depolarization, which is triggered by the action potential originating in the SA node.

• QRS Complex: Represents ventricular depolarization, caused by the action potential traveling through the Bundle of His and Purkinje fibers.

• T wave: Reflects ventricular repolarization, as the ventricles recover from the action potential.

Describe how ECG/EKG waves correlate with contraction/relaxation events of the cardiac cycle.

• P Wave: Atrial Contraction (Atrial Systole)

• QRS Complex: Ventricular Contraction (Ventricular Systole)

• T Wave: Ventricular Relaxation (Ventricular Diastole)

Define: Arrhythmia

An irregular heartbeat due to damage of intrinsic cardiac conduction network/pacemakers.

Define: Tachycardia

When a heart beats too fast.

Define: Bradycardia

When a heart beats too slow.

Define: Fibrillation

When a heart is out-of-sync; results in disorganized heartbeat (chaotic ECG/EKG).

Define: Heart Rate

The number of beats/minute.

Define: Stroke Volume

The volume of blood pumped out by one ventricle with each beat.

*Each ventricle pumps out about 70 mL of blood with each beat, which is about 60% of the blood in the ventricle.

Define: Cardiac Output

The volume of blood pumped out by each ventricle in one minute.

*CO (ml/min) = HR (beats/min) x SV (ml/beat)

Define: Preload

The degree of which cardiac muscle cells are stretched before they contract.

*Higher Preload = Higher Stroke Volume

Define: Afterload

The pressure that the ventricles must overcome to eject blood; 80 mmHg in aorta and 10 mmHg in pulmonary trunk.

What is systolic blood pressure? What is diastolic blood pressure?

• Systolic Pressure: the highest pressure in the arteries during ventricular systole.

• Diastolic Pressure: the pressure in the arteries during diastole; the lower value when taking blood pressure.

What causes heart sounds?

Valves Closing

What is the bainbridge reflex? When does it happen?

• Def: When blood increases (due to an increase in the venous return), stretch receptors in atria walls are stimulated, resulting in sensory signals being sent to the medulla oblongata…this leads to motor output being sent back to the heart, increasing heart rate.

• Occurs: After Childbirth

  • Extra blood is put into mothers circulation, increasing pressure in and stretching vena cava, which activate sretch receptors in atria. This leads to sensory signals being sent to the medulla oblongata, increasing heart rate and decreasing pressure in vena cava; heart rate returns to normal after atrial pressure decreases (extra blood is released through urine).