Key Takeaways
- The heart has four chambers: two atria (receive blood) and two ventricles (pump blood)
- Blood flows: body → right atrium → right ventricle → lungs → left atrium → left ventricle → body
- Pulmonary arteries carry deoxygenated blood; pulmonary veins carry oxygenated blood
- The SA node is the heart's pacemaker; it initiates each heartbeat
- Systole = contraction (higher pressure); Diastole = relaxation (lower pressure)
The Cardiovascular System
The cardiovascular system is one of the most heavily tested topics on the TEAS Science section. Understanding heart anatomy, blood flow, and circulation is essential for nursing practice.
Heart Anatomy
The heart is a four-chambered muscular organ that pumps blood throughout the body.
| Chamber | Location | Function | Blood Type |
|---|---|---|---|
| Right Atrium | Upper right | Receives deoxygenated blood from body | Deoxygenated |
| Right Ventricle | Lower right | Pumps blood to lungs | Deoxygenated |
| Left Atrium | Upper left | Receives oxygenated blood from lungs | Oxygenated |
| Left Ventricle | Lower left | Pumps blood to body (strongest chamber) | Oxygenated |
Heart Valves
Valves prevent backflow of blood:
| Valve | Location | Connects |
|---|---|---|
| Tricuspid | Right side | Right atrium → Right ventricle |
| Pulmonary | Right side | Right ventricle → Pulmonary artery |
| Mitral (Bicuspid) | Left side | Left atrium → Left ventricle |
| Aortic | Left side | Left ventricle → Aorta |
Memory tip: "Tri" before you "Bi" (Tricuspid on right, Bicuspid/Mitral on left)
Blood Flow Through the Heart
Step-by-step pathway:
- Deoxygenated blood enters right atrium via superior/inferior vena cava
- Passes through tricuspid valve into right ventricle
- Pumped through pulmonary valve into pulmonary arteries
- Blood goes to lungs for gas exchange (picks up O₂, releases CO₂)
- Oxygenated blood returns via pulmonary veins to left atrium
- Passes through mitral valve into left ventricle
- Pumped through aortic valve into aorta
- Distributed to the body via systemic circulation
Two Circulations
| Circuit | Path | Function |
|---|---|---|
| Pulmonary | Heart → Lungs → Heart | Gas exchange |
| Systemic | Heart → Body → Heart | Deliver O₂, remove CO₂ |
Key Distinction:
- Pulmonary arteries carry deoxygenated blood (only arteries that do)
- Pulmonary veins carry oxygenated blood (only veins that do)
Cardiac Cycle
The cardiac cycle includes contraction and relaxation phases:
| Phase | Action | Valves |
|---|---|---|
| Systole | Ventricles contract | AV valves closed, semilunar open |
| Diastole | Ventricles relax | AV valves open, semilunar closed |
Cardiac Conduction System
The electrical pathway that coordinates heartbeats:
- SA Node (Sinoatrial) - "Pacemaker," initiates impulse
- AV Node (Atrioventricular) - Delays signal briefly
- Bundle of His - Carries impulse to ventricles
- Bundle Branches - Left and right branches
- Purkinje Fibers - Distribute impulse throughout ventricles
Blood Vessels
| Type | Function | Characteristics |
|---|---|---|
| Arteries | Carry blood away from heart | Thick walls, high pressure, elastic |
| Arterioles | Small arteries | Regulate blood flow |
| Capillaries | Exchange site | One cell thick, allow diffusion |
| Venules | Small veins | Collect from capillaries |
| Veins | Return blood to heart | Thinner walls, valves prevent backflow |
Blood Pressure
Blood pressure = force of blood against arterial walls
- Systolic (top number): Pressure during ventricular contraction
- Diastolic (bottom number): Pressure during ventricular relaxation
Normal: 120/80 mmHg
Key Cardiovascular Terms
| Term | Definition |
|---|---|
| Cardiac output | Volume of blood pumped per minute |
| Stroke volume | Volume pumped per heartbeat |
| Heart rate | Beats per minute |
| Bradycardia | Slow heart rate (< 60 bpm) |
| Tachycardia | Fast heart rate (> 100 bpm) |
Which chamber of the heart pumps oxygenated blood to the body?
Which blood vessels carry oxygenated blood?
Which structure initiates the electrical impulse for each heartbeat?