A&P 244 Lab - Heart Anatomy Physiology with EKG

What centrally located area within the thoracic cavity contains the heart and pericardial cavity?

The heart and pericardial cavity are located within the mediastinum, situated between the left and right pleural cavities.

Describe the anatomical landmarks that define the base of the heart.

The base of the heart extends from the inferior border of the second costal cartilage on the left side to the superior border of the third costal cartilage on the right side.

Where is the apex of the heart located in relation to the rib cage and median plane?

The apex of the heart is located in the left fifth intercostal space, positioned to the left of the median plane.

What term describes the surface location near the apex where the heartbeat is most observable?

The point of maximum impulse (PMI) is the location on the body surface near the apex where the heartbeat can be observed.

Distinguish between the two primary parts of the pericardium.

The pericardium consists of an outer fibrous pericardium fused to adjacent structures and an inner serous pericardium that forms a double-layered sac.

What are the two specific layers that comprise the serous pericardium?

The serous pericardium consists of the parietal layer and the visceral layer, the latter of which is also known as the epicardium.

In which specific circuit does the left side of the heart control blood flow to deliver nutrients to all body tissues?

The left side of the heart controls systemic circulation, delivering oxygen and nutrients to cells while removing metabolic wastes.

What is the primary function of the pulmonary circulation controlled by the right side of the heart?

Pulmonary circulation sends blood to the lungs to replenish oxygen stored in red blood cells and release carbon dioxide.

What is the alternative name for the atrioventricular sulcus on the exterior of the heart?

The atrioventricular sulcus is also commonly referred to as the coronary sulcus.

Identify the two main arteries that reside in the anterior interventricular sulcus and the posterior interventricular sulcus respectively.

The anterior interventricular sulcus contains the left anterior descending (LAD) artery, while the posterior interventricular sulcus contains the posterior descending (PD) artery.

Which major vein is located within the anterior interventricular sulcus alongside the LAD artery?

The great cardiac vein is found within the anterior interventricular sulcus.

Which specific vein ascends along the posterior interventricular groove?

The middle cardiac vein ascends along the posterior interventricular groove.

What are the ear-like extensions that cover the atria on the exterior surface of the heart?

Auricles are the flap-like structures that cover the atria on the exterior of the heart.

Identify the fetal remnant that connects the pulmonary trunk to the aortic arch.

The ligamentum arteriosum is the fibrous remnant of fetal circulation connecting the pulmonary trunk and the aortic arch.

What structural depression in the interatrial septum represents the remnant of the fetal foramen ovale?

The fossa ovalis is the depression in the interatrial septum that remains after the foramen ovale closes at birth.

What are the muscle ridges located on the internal walls of the atria?

Pectinate muscles are the muscular ridges found on the internal surfaces of the atria.

What term describes the irregular muscular ridges found on the internal walls of the ventricles?

Trabeculae carneae are the internal muscular ridges located within the ventricles of the heart.

Contrast the cusp counts of the right and left atrioventricular valves.

The right atrioventricular valve (tricuspid) has three cusps, while the left atrioventricular valve (mitral or bicuspid) has two cusps.

What is the function of the chordae tendineae and papillary muscles during ventricular contraction?

They prevent the atrioventricular valve cusps from opening backwards into the atria (prolapse), ensuring a tight seal to prevent regurgitation.

Which valves control the flow of blood from the ventricles into the great arteries?

The semilunar valves, specifically the pulmonary and aortic valves, control the flow of blood into the pulmonary trunk and aorta respectively.

Why is the myocardium of the left ventricle significantly thicker than that of the right ventricle?

The left ventricle must generate enough force to pump blood through the high-resistance systemic circulation, whereas the right ventricle only pumps through the lower-resistance pulmonary circuit.

Which coronary artery exits the aorta and gives rise to the left anterior descending (LAD) and circumflex arteries?

The left coronary artery (LCA) exits the aorta and branches into the LAD and circumflex arteries.

Where does the coronary sinus empty its deoxygenated blood?

The coronary sinus runs along the coronary sulcus on the posterior surface and empties directly into the right atrium.

What term describes the connection formed between the LAD and PD arteries near the apex to provide collateral circulation?

The connection formed between the anterior and posterior interventricular arteries near the apex is called an anastomosis.

Define the physiological terms 'systole' and 'diastole' as they relate to the cardiac cycle.

Systole refers to the phase of contraction of the heart muscle, while diastole refers to the phase of relaxation.

What characteristic of the cardiac conduction system allows the heartbeat to originate spontaneously within the heart?

The heart exhibits automaticity (myogenic property), meaning it is autorhythmic due to spontaneous depolarization enabled by Ca^{++} leakage channels.

Which structure serves as the primary pacemaker of the heart by initiating each heartbeat?

The sinoatrial (SA) node serves as the natural pacemaker of the heart, initiating the heartbeat and setting the heart rate.

How does the fibrous skeleton of the heart contribute to coordinated cardiac contraction?

The fibrous skeleton acts as an electrical insulator, preventing impulses from passing directly from the atria to the ventricles except through the specialized conduction system.

Why is there a 0.10 second delay at the atrioventricular (AV) node?

The delay allows time for the atria to finish contracting and fully fill the ventricles with blood before ventricular systole begins.

Trace the pathway of an electrical signal from the AV bundle to the ventricular muscle.

The signal travels from the AV bundle through the right and left bundle branches in the interventricular septum to the Purkinje fibers, which spread throughout the ventricles.

What is the average resting potential difference produced by the heart's electrochemical impulses?

The average potential difference of the heart's electrochemical impulses is approximately -90 millivolts.

What physiological event does the P wave represent on an EKG?

The P wave represents the depolarization of the atria just prior to atrial contraction.

What does the QRS complex indicate in terms of electrical activity and subsequent mechanical action?

The QRS complex represents ventricular depolarization, which precedes ventricular systole.

Why is atrial diastole (repolarization) not visible as a distinct wave on a standard EKG?

Atrial repolarization occurs during the QRS complex and is obscured by the much larger electrical signal generated by the ventricular muscle mass.

What event is indicated by the appearance of the T wave on an EKG tracing?

The T wave results from ventricular repolarization, which occurs just before ventricular relaxation.

Define tachycardia and bradycardia based on adult heart rate thresholds.

Tachycardia is defined as a heart rate above 100 beats per minute, while bradycardia is a heart rate below 60 beats per minute in adults.

What is the normal duration of the PR interval on an EKG?

The PR interval normally lasts approximately 0.16 second.

A PR interval longer than 0.2 second is typically diagnostic of which condition?

A PR interval exceeding 0.2 second indicates a first-degree atrioventricular (AV) block, signifying reduced conduction between the atria and ventricles.

Describe the electrical relationship between the atria and ventricles in a third-degree (complete) AV block.

In a third-degree AV block, the atria fail to stimulate ventricular depolarization at all, causing the atria and ventricles to fire independently of one another.

What is the normal average duration of a QRS complex, and what does an interval exceeding 0.12 second suggest?

The normal QRS interval is 0.08 to 0.10 second; an interval longer than 0.12 second may indicate a right or left bundle branch block.

What is the typical duration of the QT interval, and how does it respond to changes in heart rate?

The QT interval is normally about 0.3 second and shortens as the heart rate increases.

What occurs during atrial fibrillation that prevents effective blood pumping?

During atrial fibrillation, the electrical activity is uncoordinated, causing the upper chambers to quiver rather than contract effectively.

Why is ventricular fibrillation considered a lethal arrhythmia requiring immediate defibrillation?

Ventricular fibrillation involves uncoordinated contraction of the ventricular muscle, resulting in zero blood being pumped to the body, which leads to death without electrical intervention.

What is a premature ventricular contraction (PVC)?

A PVC is an early, irregular heartbeat caused by an ectopic electrical signal in the ventricles that often goes unnoticed by the patient.

How can heart rate be calculated using the boxes on EKG paper?

Heart rate is determined by counting the squares between QRS complexes, where each large box represents 0.2 seconds and each small box represents 0.04 seconds.

What is the purpose of heart auscultation using a stethoscope?

Auscultation is used to listen for valve abnormalities, such as stenosis or prolapse, which create abnormal sounds and blood turbulence.

Which artery branches off the right coronary artery (RCA) on the anterior surface before the RCA wraps around the back?

The right marginal artery branches off the RCA on the anterior surface of the heart.

Identify the internal wall that separates the two ventricles.

The interventricular septum is the muscular wall that divides the right and left ventricles.

What is the clinical significance of a stenotic heart valve?

A stenotic valve does not open completely, which restricts blood flow and creates turbulence that can be heard as an abnormal heart sound.

What are the three components that make up the heart wall?

The heart wall is composed of the epicardium (visceral pericardium), the myocardium (cardiac muscle), and the endocardium (inner lining).