Cardiac Anatomy and Physiology Notes

Pressures

• PA/PCWP diastolic = LA mean

• LA mean = LV diastolic

• LV systolic = AO systolic

• AO diastolic = LV end-diastolic pressure

Pop Quiz Answers (Pressures)

1. 2-8

2. 15-25

3. 2-12

4. Less than 120

Network of Vessels

• Flowchart shows the path from the right heart to the left, and from the left heart back to the right.

• The capillary mesh bed brings arteries, arterioles, venules, and veins together.

Vessel Functions

• Vessels transport blood to and from the heart throughout the body.

• Arteries, arterioles, and capillaries: deliver oxygen and nutrients to tissues.

• Capillaries, venules, and veins: remove carbon dioxide and waste products from tissues.

Arteries

• Carry blood away from the heart.

• Relatively thick with elasticity.

• Maintain pressure in the system to keep blood flow moving forward.

• High pressure within the systemic circulatory system presents greater resistance to the heart compared to the pulmonary circulatory system.

• Arteries redistribute into smaller vessels called arterioles.

Arterioles

• Redistribute further into tiny vessels, the capillaries.

Capillaries

• Bridge arterioles and venules.

• Tiny vessels that permit the exchange of nutrients, oxygen, waste, and carbon dioxide between the arterial and venous systems.

Venules

• Converge to form larger veins.

Veins

• Carry blood towards the heart.

• Not as thick as arteries and can collapse/expand rapidly.

Pulmonary Circulatory System

• Includes the right heart and all pulmonary vessels.

• Order of flow:

  • Right heart to main pulmonary artery (PA).

  • Main PA bifurcates into left PA (LPA) and right PA (RPA).

  • Branches into smaller pulmonary arteries, arterioles.

  • Pulmonary capillary bed.

  • Venules.

  • Four pulmonary veins back to the left heart.

Systemic Circulatory System

• Includes the left heart and all systemic vessels.

• Order of flow from the left heart:

  • Aorta (AO).

  • Branches into smaller arteries, arterioles.

  • Capillaries.

  • Venules.

  • Veins.

  • Superior vena cava (SVC) and inferior vena cava (IVC) back to the right heart.

Trace a Drop of Blood

• Start in the RA (Right Atrium) through the TV to RV (Right Ventricle) → through the PV (Pulmonary Valve) → PA (Pulmonary Artery) → RPA/LPA (Right/Left Pulmonary Artery) → Arteries → Arterioles → Pulmonary Capillary Bed → Venules → PV (Pulmonary Veins - 4) → LA (Left Atrium) → MV (Mitral Valve) → LV (Left Ventricle) → AOV (Aortic Valve) → AO (Aorta) → Arteries → Arterioles → Capillaries → Venules → Veins → SVC/IVC (Superior/Inferior Vena Cava) → RA (Right Atrium).

Heart Location

• Located in the thoracic cavity.

• Cradled in a cage of bone (sternum and vertebral column), cartilage, and muscle.

• Just to the left of the midline of the mediastinum.

• Above the diaphragm, with the lungs on either side.

• Does not sit squarely in the chest cavity.

Terminology for Understanding Heart Position

• Anterior (Ventral): Front of the body.

• Posterior (Dorsal): Back of the body.

• Superior (Basal): Towards the head, higher, or above.

• Inferior (Diaphragmatic): Towards the feet, below, or lower.

• Medial: Towards the midline.

• Lateral: Away from the midline.

• Proximal: Near the origin.

• Distal: Away from the origin.

Visualizing the Heart in the Chest Cavity

• Base (Top of the Heart):

  • Most superior.

  • Rotates posterior and in a rightward direction.

• Apex (Bottom of the Heart):

  • Most inferior.

  • Rotates anterior and in a leftward direction.

Pop Quiz: Heart Location

What cradles the heart & where is it located?

• The heart is cradled in a cage of bone (sternum, vertebral column), cartilage, and muscle, just left of the midline of the mediastinum, above the diaphragm, with lungs on each side.

Pericardium and Heart Wall

Pericardium

• The heart is encased within the pericardium, a fluid-filled sac.

• Covers the heart and helps prevent infection and trauma.

• Aids in the free pumping motion of the heart.

• It is a loose, double-layered sac.

  • Fibrous pericardium.

  • Serous pericardium.

Fibrous Pericardium

• The outer layer of the pericardium.

Serous Pericardium

• The inner layer of the pericardium.

• Consists of two layers:

  • Parietal layer: Lines the inside of the fibrous pericardium.

  • Visceral layer: Adheres to the outside of the heart (also known as the epicardium, the outermost layer of the heart).

Pericardial Space

• Sits between the visceral and parietal layers and contains clear fluid released by the serous membrane.

• The fluid acts as a lubricant during contraction (systole) and relaxation (diastole) of the heart.

• Normally contains 10-30 ml of fluid.

• In certain disease states, the pericardial space can fill with additional fluid, known as pericardial effusion.

Heart Walls

• The heart wall consists of three layers:

  • Epicardium.

  • Myocardium.

  • Endocardium.

Epicardium

• The outermost layer of the heart wall.

• Covers the surface of the heart and extends to the great vessels.

• Also known as the visceral layer of the serous pericardium.

Myocardium

• The central layer of the heart wall.

• Thick and muscular.

• Composed of striated muscle fibrils that contract.

• This layer is responsible for the heart's pumping action, facilitating the movement of blood throughout the circulatory system.

    Endocardium

• The innermost layer of the heart, it provides a smooth surface for blood flow and reduces friction during the contraction and relaxation of the heart.

• The innermost layer of the heart, providing a smooth lining for the chambers and valves, and playing a crucial role in preventing blood clots.