Cardiovascular System — Heart & Blood

Heart anatomy:

4 chambers: Right atrium → Right ventricle → Pulmonary circuit → Left atrium → Left ventricle → Systemic circuit

Right side = deoxygenated blood; Left side = oxygenated blood

Conduction system:

SA node → AV node → Bundle of His → Bundle branches → Purkinje fibers

SA node = natural pacemaker (60–100 bpm)

Cardiac cycle:

Systole — ventricles contract, blood ejected

Diastole — ventricles relax, fill with blood

Blood pressure = systolic/diastolic (120/80 normal)

Blood components:

RBCs (erythrocytes) — carry oxygen via hemoglobin; no nucleus in mature form

WBCs (leukocytes) — immune defense

Platelets (thrombocytes) — clotting

Plasma — water, proteins, nutrients, hormones

Hemoglobin: 4 subunits, each carrying one O₂. Cooperative binding — O₂ saturation follows sigmoid curve. Bohr effect: ↑CO₂ or ↑H⁺ → ↓O₂ affinity → releases O₂ to tissues.

Reference:

Wikipedia: Cardiovascular System

https://en.wikipedia.org/wiki/Cardiovascular_system