Anatomy WK 4/5 (3/4) | Heart & Blood Flow (copy)

Septal Defects Overview

• Patent Foramen Ovale and Patent Ductus Arteriosus are types of septal defects in the heart.

  • These structures typically close shortly after birth.

  • Post-closure, these structures leave behind anatomical remnants.

Anatomical Remnants

• Foramen Ovale:

  • Name for the open hole between the left and right atria.

  • After closure, it forms the Fossa Ovalis.

• Ductus Arteriosus:

  • A vessel that connects the pulmonary artery to the aorta in the fetus.

  • When it closes, it becomes known as the Ligamentum Arteriosum.

  • Note: Don't stress about spelling during exams; if you identify the concept, you are likely correct.

Development and Variation in Heart Anatomy

• Human hearts display anatomical variability; each heart may differ in arrangement and structure.

  • Variation is even greater across species.

  • Mammals have a four-chambered heart, with total separation between the left and right sides, which is a relatively recent evolutionary advancement.

  • Other species like reptiles and amphibians often exhibit three-chambered hearts where blood can mix.

Comparative Anatomy

• Three-chambered hearts:

  • Composed of two ventricles and one atrium; example species: turtles, snakes, and lizards.

  • Allow mixing of oxygenated and deoxygenated blood, affecting efficiency.

  • These species often require less oxygen due to their metabolic rates.

• Crocodilians:

  • Feature a fully separated four-chambered heart similar to mammals.

  • Display unique adaptations, such as two aortas for efficient blood flow regulation in oxygen-deprived environments.

Cardiac Conduction System

• Role of the Nervous System: The heart's rhythm is regulated by a special set of nerves, forming the cardiac conduction system.

  • Begins with the Sinoatrial (SA) Node (the heart's pacemaker) located in the right atrium.

• Pacemaker Function:

  • The SA node generates electrical signals that trigger heartbeats.

  • Rate of signals correlates with heart rate: 60 signals per minute = 60 beats per minute.

Atrial and Ventricular Contraction

• Order of Contraction:

  • The SA node first stimulates atrial contraction, then sends a signal to the Atrioventricular (AV) Node.

  • The AV node generates a stronger signal, leading to ventricular contraction.

• Delay Purpose:

  • The AV node introduces a delay, allowing the atria to finish contracting and filling the ventricles before the ventricles contract.

Pathway of Cardiac Signals

• The signal travels from the AV node down the AV Bundle and divides into Right and Left Bundle Branches leading to Purkinje Fibers.

  • This pathway ensures coordinated contraction, starting from the bottom of the heart, allowing efficient blood ejection into the pulmonary artery and aorta.

Heart Rate Regulation

• Two nervous system components influence SA node activity:

  • Sympathetic Nervous System: Increases heart rate during stress or excitement (fight or flight).

  • Parasympathetic Nervous System: Decreases heart rate, aiding a state of rest and recovery.

Arrhythmias and Tachycardia

• Arrhythmia: Abnormal heart rhythm, with variations in rate or how the electrical signals operate.

• Common types include Atrial Fibrillation (A-Fib):

  • Characterized by disorganized and ineffective atrial contractions.

  • May lead to insufficient blood flow to the ventricles, increasing the risk of clot formation.

Implications of Atrial Fibrillation

• Increased risk of stroke due to potential clot formation in the atria escaping into circulation.

• Treatment options include medications to manage heart rhythm and prevent clots, such as anticoagulants.

• Surgical interventions, like catheter ablation, may be necessary for problematic cases.

Myocardial Infarction (Heart Attack)

• Defined as disruption of blood flow to cardiac muscle, typically caused by blocked coronary arteries.

  • Symptoms include chest pain and may lead to serious heart muscle damage and dysfunction.

• Detection: Use of cardiac biomarkers (troponin, myoglobin, creatine kinase) in the bloodstream.

  • Evaluating these markers helps determine the timing and management of heart attacks.

Interventional Procedures

• Common procedures to treat heart blockages include Angioplasty and Coronary Artery Bypass Grafting (CABG):

  • Angioplasty: A catheter with a balloon and possible stent to open narrowed arteries.

  • CABG: Involves grafting veins or arteries from other body parts to bypass blocked arteries, restoring blood flow.

Importance of Prompt Treatment

• Immediate response to heart attack symptoms or strokes is crucial for minimizing damage and ensuring better patient outcomes.

  • Utilizing timely medical intervention after assessing symptoms can significantly influence recovery.

Blood Flow Dynamics

• Coronary arteries supply blood to the heart muscle, crucial for function and survival; blockage can lead to myocardial infarction (heart attack).

  • Recognizing symptoms, engaging in prompt medical response, and understanding risk factors (post-viral complications) are essential for patient health.