Heart and Circulation

Heart as Pumps

• The heart can be viewed as a pair of pumps with attached pipes.
• The diagram appears complex initially but simplifies with labeling.

Chambers of the Heart

• The right atrium receives blood, which then flows into the right ventricle.
• The left atrium and left ventricle are the chambers on the other side of the heart.

Pulmonary Circulation

• Right Ventricle: The starting point of our journey.
• Pulmonary Trunk: Blood exits the right ventricle and passes through a valve into the pulmonary trunk, represented as a single tube.
• Pulmonary Arteries: The pulmonary trunk splits into left and right pulmonary arteries.
  • Arteries carry blood away from the heart.
  • There are two pulmonary arteries: left and right.
• Lungs: Blood travels through the pulmonary arteries to the lungs.
  • Diagrammatically, the lungs are represented as discrete units (though not anatomically accurate).
• Pulmonary Veins: Blood exits the lungs via pulmonary veins.
  • There can be multiple pulmonary veins from each lung, not just one.
• Left Atrium: Pulmonary veins drain oxygenated blood into the left atrium.
• Pulmonary Circulation: The circuit from the right ventricle to the lungs and back to the left atrium.
• Deoxygenated blood flows from the right ventricle through the pulmonary trunk and arteries into the lungs.
• In the lungs, blood mixes with capillaries and gains oxygen.
• Oxygenated blood returns via the pulmonary veins to the left atrium.

Systemic Circulation

• Left Ventricle: The starting point for systemic circulation.
• Blood flows from the left ventricle to the rest of the body, including the brain, liver, bones, and toes.
• Aorta: Blood exits the left ventricle through the aorta, a large vessel that branches to supply the body.
• Blood travels to the body's tissues and organs, delivering oxygen.
• Vena Cavae: Deoxygenated blood returns to the right atrium via the superior and inferior vena cavae.
  • Superior vena cava: Drains the upper body.
  • Inferior vena cava: Drains the lower body.
• Systemic Circulation: Circuit from the left ventricle to the body and back to the right atrium.
• Organs use oxygen from the blood, and deoxygenated blood returns to the right atrium.

Two Circuits

• Pulmonary circulation relies on the right ventricle as the pump.
• Systemic circulation relies on the left ventricle as the pump.

Blood Supply to Specific Tissues

• The body generally receives oxygenated blood from the left ventricle.

Red Blood Cells (RBCs)

• Red blood cells carry oxygen to the body.
• RBCs do not have mitochondria.
• Mitochondria are organelles that use oxygen.
• $No Mitochondria \implies Not Using Oxygen$
• Red blood cells also lack a nucleus.
• They are specialized for oxygen transport, essentially bags of hemoglobin.
• RBCs do not need oxygen; they transport it.

Heart

• The heart receives oxygenated blood via the systemic circulation.
• Coronary Vessels: Supply blood to the heart.
  • Coronary arteries and veins.
• Coronary vessels branch off the aorta.
• Veins drain directly into the right atrium.
  • Not into the inferior or superior vena cava.

Lungs

• Lungs receive oxygen from the systemic circulation via bronchial arteries.
• Bronchial arteries supply oxygenated blood to the lungs.
• Bronchial vessels include both arteries and veins.
• Veins from the right lung drain into systemic circulation.
• Mixing of blood occurs in the lungs.
• Pulmonary arteries carry blood, and bronchial arteries carry blood; these mix in the capillaries.
• Most blood returns via pulmonary veins.
• The lungs receive blood from both systemic and pulmonary circulations.
• Mixing of blood from both circulations occurs in the lungs.