Heart Anatomy and Circulatory System Flashcards

Anatomy of the Human Heart

• The human heart is a complex muscular organ composed of several distinct structures and chambers necessary for blood circulation.

• Major External and Internal Structures:

  • Superior vena cava: The large vein that brings deoxygenated blood from the upper body (head and arms) to the heart.

  • Inferior vena cava: The large vein that carries deoxygenated blood from the lower part of the body to the heart.

  • Aorta: The primary artery that carries oxygenated blood from the left ventricle to the rest of the body.

  • Pulmonary artery: The vessel that transports deoxygenated blood from the right ventricle to the lungs.

  • Pulmonary veins: The vessels that carry oxygenated blood from the lungs back to the left atrium of the heart.

  • Right atrium: The upper right chamber that receives deoxygenated blood.

  • Left atrium: The upper left chamber that receives oxygenated blood.

  • Right ventricle: The lower right chamber responsible for pumping deoxygenated blood to the lungs.

  • Left ventricle: The lower left chamber responsible for pumping oxygenated blood to the entire body.

  • Tricuspid valve: The valve located between the right atrium and the right ventricle.

  • Mitral (bicuspid) valve: The valve located between the left atrium and the left ventricle.

  • Septum: A thick muscular wall that separates the left side of the heart from the right side.

  • Apex: The bottom, pointed end of the heart.

Functional Comparison of Heart Chambers (Table $4.3$)

• The heart comprises $4$ chambers: $2$ upper chambers (Atria) and $2$ lower chambers (Ventricles).

• Septum Functions:

  • Separates the left side of the heart from the right side.

  • Prevents the blood on either side of the heart from mixing.

• Right Side Characteristics:

  • Right Atrium:

    • Features thin walls.

    • Blood arrives from the body via the vena cava and empties into the right ventricle.

    • The blood is low in oxygen ($O_2$) and high in carbon dioxide ($CO_2$) because it is returning from the body.

  • Right Ventricle:

    • Consists of muscular walls to pump blood out of the heart toward the lungs.

    • Pumps deoxygenated blood out of the heart to the lungs via the pulmonary artery.

• Left Side Characteristics:

  • Left Atrium:

    • Features thin walls.

    • Blood arrives from the lungs via the pulmonary vein.

    • The blood is high in oxygen ($O_2$) and low in carbon dioxide ($CO_2$) because it is coming directly from the lungs.

  • Left Ventricle:

    • Possesses very muscular walls that are significantly thicker than the right ventricle.

    • This thickness is required to pump blood out of the heart to the entire body.

    • Pumps oxygenated blood out of the heart to the rest of the body via the aorta.

Pathways of Blood Flow

• The right side of the heart is dedicated to pumping deoxygenated blood.

• The left side of the heart is dedicated to pumping oxygenated blood.

• Pathway of Deoxygenated Blood (Right Side):

  • Deoxygenated blood from head and body \rightarrow Vena Cava \rightarrow Right Atrium \rightarrow Right Ventricle \rightarrow Pulmonary Artery \right arrow Lungs.

• Pathway of Oxygenated Blood (Left Side):

  • Oxygenated blood from Lungs \rightarrow Pulmonary Vein \rightarrow Left Atrium \rightarrow Left Ventricle \rightarrow Aorta \rightarrow Body.

The Double Circulatory System in Humans

• Humans possess a double circulatory system, meaning blood makes $2$ complete circuits in the body.

• Components of Double Circulation:

  • Pulmonary Circulation: The right side of the heart pumps deoxygenated blood from the body to the lungs.

  • Systemic Circulation: The left side of the heart pumps oxygenated blood from the lungs all around the body.

• Necessity of a Double Circulatory System:

  • Blood loses pressure when it passes through organs.

  • In a hypothetical single circulatory system (heart \rightarrow lungs \rightarrow body), the blood pressure would drop too low to effectively reach the entire body.

  • With double circulation, blood returning from the lungs goes back to the heart first. This allows the heart to repressurize the blood, providing enough pressure to circulate it through the systemic circuit to the body.

Structure and Function of Blood Vessels

• There are $3$ primary types of blood vessels in the human circulatory system: arteries, veins, and capillaries.

• Arteries:

  • Function: Transports blood from the heart to the organs.

  • Structure: Thick outer wall, a small lumen (internal space), and a thick layer of muscle and elastic fibers.

  • Properties: Elastic walls, no valves, and contains blood at very high pressure.

• Veins:

  • Function: Transports blood from the organs back to the heart.

  • Structure: Fairly thin outer wall, a large lumen, and a thin layer of muscle and elastic fibers.

  • Properties: Less elastic walls compared to arteries and contains valves to prevent the backflow of blood.

  • Blood Pressure: Blood is at very low pressure.

• Capillaries:

  • Function: Carries blood to organs where gas exchange occurs.

  • Structure: Very narrow lumen with a wall made of a single ($1$) layer of cells.

  • Properties: Inelastic walls and no valves.

  • Blood Pressure: Blood is at low pressure.

Comparative Summary of Blood Vessels