CVS task 5

• • The right atrium (RA) receives deoxygenated blood from three major venous structures:
  • Superior Vena Cava (SVC)
  • Drains blood from the upper body, including the head, neck, upper limbs, and thorax
  • No associated valve at its entry into the RA
  • Inferior Vena Cava (IVC)
  • Drains blood from the lower body, including the abdomen, pelvis, and lower limbs
  • Contains a rudimentary valve called the Eustachian valve, which is non-functional in adults
  • Coronary Sinus
  • Collects deoxygenated blood from the myocardium (heart muscle)
  • Has a small Thebesian valve at its opening into the RA

  
• • Right AV Valve → Tricuspid Valve
  • Located between the Right Atrium (RA) and Right Ventricle (RV)
  • Prevents backflow of blood into the right atrium during ventricular contraction
  • Left AV Valve → Mitral (Bicuspid) Valve
  • Located between the Left Atrium (LA) and Left Ventricle (LV)
  • Also prevents backflow, ensuring unidirectional blood flow from the left atrium to the left ventricle

  
• • The coronary sinus receives blood from the coronary veins, which drain the heart muscle (myocardium)
  • The deoxygenated blood collected here originates from the heart itself and is returned to the right atrium for reoxygenation in the lungs

  
• • Deoxygenated blood is transported from the right ventricle (RV) to the lungs via the pulmonary arteries
  • This occurs through two major vessels:
  • Right Pulmonary Artery – carries blood to the right lung.
  • Left Pulmonary Artery – carries blood to the left lung.

  
• • The Pulmonary Valve (Pulmonary Semilunar Valve) regulates blood flow from the right ventricle into the pulmonary trunk, which then divides into the right and left pulmonary arteries
  • This valve prevents backflow of blood into the right ventricle after contraction

  
• • Oxygenated blood returns from the lungs to the left atrium via the pulmonary veins.
  • There are 4 pulmonary veins:

  1. Right Superior Pulmonary Vein – drains oxygenated blood from the right upper lung.
  2. Right Inferior Pulmonary Vein – drains oxygenated blood from the right lower lung.
  3. Left Superior Pulmonary Vein – drains oxygenated blood from the left upper lung.
  4. Left Inferior Pulmonary Vein – drains oxygenated blood from the left lower lung.

  
• • During systole (ventricular contraction), the left ventricle ejects oxygenated blood into the aorta, which is the largest artery in the body.
  • The ascending aorta receives this blood and distributes it through the systemic circulation.

  
• • The Aortic Valve (Aortic Semilunar Valve) controls blood flow from the left ventricle into the aorta.
  • It prevents backflow of blood into the left ventricle after systole, ensuring one-way circulation.

  
• Chordae Tendineae (Heart Strings)

  • Structure:
  • Thin, fibrous, tendon like cords made of collagen and elastin fibres
  • Connect the atrioventricular valves (tricuspid and mitral/bicuspid) to the papillary muscles in the ventricles
  • Function:
  • Prevent the atrioventricular valves from inverting (prolapsing) into the atria during ventricular contraction (systole)
  • Ensure that blood flows in one direction, preventing regurgitation into the atria

  A) Chordae Tendineae

  
• Papillary Muscles

  • Structure:
  • Small, cone shaped muscles located in the ventricular walls
  • Attach to the chordae tendineae at their tips
  • Function:
  • Contract during ventricular systole to tighten the chordae tendineae, stabilizing the atrioventricular valves
  • Help prevent valve prolapse and ensure proper closure

  A) Papillary Muscles