lab_2_the_heart

Exercise 2: The Heart

• Understanding the heart as a vital organ responsible for pumping blood throughout the body.

The Heart Overview

• Description: The heart is often referred to as "A Pump."

• Primary Functions: Circulate blood to supply oxygen and nutrients while removing waste.

Heart Anatomy (Exterior Overview)

• Base: Superior portion of the heart.

• Apex: Inferior pointed end of the heart.

• Auricles:

  • Right Auricle: Receives deoxygenated blood from the body.

  • Left Auricle: Receives oxygenated blood from the lungs.

• Great Vessels:

  • Located at the base, including the pulmonary trunk, inferior and superior vena cava, and aorta.

• Coronary Vessels: Supply blood to and drain blood from the heart muscle.

• Epicardium: The thin, shiny outer covering of the heart.

Heart Anatomy (Exterior)

• Anterior View:

  • Displays the Aorta, Right Auricle, Right Ventricle, and Left Ventricle.

• Posterior View:

  • Highlights the Right Auricle and other structures like veins and arteries.

Coronary Vessels

• Coronary Arteries:

  • Anterior View:

    • The Left Anterior Descending artery (LAD) branches from the left coronary artery and is significant for supplying blood to the heart muscle.

• Coronary Veins:

  • Drain deoxygenated blood back to the right atrium, crucial for circulation.

  • Includes the Great Cardiac Vein, Middle Cardiac Vein, and Coronary Sinus.

Heart Anatomy (Interior Overview)

• The heart has 4 chambers:

  • 2 superior chambers (Atria)

  • 2 inferior chambers (Ventures)

• Valves:

  • Control blood flow through the heart.

• Papillary Muscles:

  • Projecting muscles in ventricles that help control valve function via chordae tendineae.

• Myocardium:

  • The heart muscle itself.

• Endocardium:

  • Thin, shiny lining of heart chambers.

Heart Valves

• Function: Act as one-way doors to ensure proper blood flow through chambers.

  • Right Atrioventricular (AV) Valve

  • Right Semilunar Valve

  • Left Atrioventricular (Mitral) Valve

  • Left Semilunar Valve

• Note: All valves are tricuspids except for the left AV (Mitral) valve, which is bicuspid.

Dissection Tips

• Orientation regarding anterior/posterior and left/right is critical.

  1. The apex tilts slightly to the left in anterior view.

  2. Ventricular wall thickness differs: left > right.

  3. The coronary sinus is located posteriorly.

Circulation Routes

• Pulmonary Circuit:

  • Starts from the right side of the heart, responsible for refreshing blood via lungs.

• Systemic Circuit:

  • Starts from the left side of the heart, responsible for refreshing tissues throughout the body.

Pulmonary Circulation

• Deoxygenated blood travels from the right heart to the lungs for oxygenation.

• Oxygenated blood returns from the lungs to the left heart.

Systemic Circulation

• Oxygenated blood is pumped from the left side of the heart to the entire body and back to the right heart.

Circulatory Rules & Exceptions

• General Rules:

  • Arteries transport oxygen-rich blood away from the heart.

  • Veins transport oxygen-poor blood towards the heart.

  • Capillaries connect the two systems.

• Exceptions:

  • The pulmonary arteries carry oxygen-poor blood, while pulmonary veins carry oxygen-rich blood.

Fetal Circulation: An Exception

• Umbilical Vein: Transports oxygenated blood from the placenta to the fetus.

• Umbilical Artery: Carries deoxygenated blood from the fetus back to the placenta.

Blood Flow in the Fetal Heart

• Blood flows from the right atrium to the left atrium and into the aorta, bypassing non-functional lungs.

• Structures such as Foramen Ovale and Ductus Arteriosus play critical roles in fetal circulation.

Heart Histology

• Cell Types in Myocardium:

  1. Myocytes: Primary muscle cells.

  2. Autorhythmic: Pacemaker cells that initiate heartbeats.

  3. Fibroblasts: Provide structural support to the heart muscle.

Cardiac Myocytes

• Characteristics:

  • Uninucleated (most), branched, striated, and involuntary.

  • Intercalated discs join adjacent cells, facilitating communication and contraction.