Cardiovascular System Overview

Cardiovascular System

• The cardiovascular system is a closed system composed of the heart and blood vessels
• The heart pumps blood to all parts of the body
• Blood vessels allow blood to circulate throughout the body

Heart Functions

• Delivers oxygen and nutrients
• Removes carbon dioxide and other waste products

Heart Size and Location

• About the size of a fist
• Located in the thoracic cavity
• Medial to the lungs
• Superior to the diaphragm
• Posterior to the sternum
• Pointed apex towards the left hip, base towards the right shoulder
• Located within the mediastinum

Heart Coverings

• Fibrous pericardium: Outer covering, loose and superficial
• Serous pericardium: Inner covering, deep to the fibrous pericardium
  • Parietal pericardium: Outer layer, lines the inner surface of the fibrous pericardium
  • Visceral pericardium: Inner layer, physically attached to the heart, also called epicardium
• Serous fluid fills the cavity between the layers

Heart Wall Layers

• Epicardium (Outer Layer): This is the visceral pericardium
• Myocardium (Middle Layer): Mostly cardiac muscle
• Endocardium (Inner Layer): Simple squamous epithelium, also called endothelium

Heart Anatomy (Chambers)

• Atria: Two upper chambers that receive blood
  • Right atrium
  • Left atrium
• Ventricles: Two lower chambers that discharge blood
  • Right ventricle
  • Left ventricle

Heart Anatomy (Blood Vessels)

• Veins: Carry blood towards the heart
• Arteries: Carry blood away from the heart

Heart: Path of Blood

• Right and left sides act as separate pumps
  • Right side pumps oxygen-poor blood
  • Left side pumps oxygen-rich blood

Heart Anatomy (Large Blood Vessels)

• Superior vena cava
• Inferior vena cava
• Pulmonary trunk
• Right pulmonary artery
• Left pulmonary artery
• Two right pulmonary veins
• Two left pulmonary veins
• Aorta

Blood Circulation

• Pulmonary Circuit: Heart → Lungs → Heart. Includes pulmonary arteries and veins.
  • Purpose: Oxygenate the blood.
• Systemic Circuit: Heart → Body → Heart. Includes venae cavae, and the aorta.
  • Purpose: Supply cells with oxygenated blood.

Heart: Path of Blood (Specific Steps)

1. Oxygen-poor blood flows into the right atrium
2. Blood moves to the right ventricle
3. The right ventricle pumps blood to the pulmonary trunk
4. Blood passes to the lungs to pick up oxygen and unload carbon dioxide
5. Oxygen-rich blood returns to the left atrium
6. Blood moves to the left ventricle
7. The left ventricle pumps blood to the aorta to be distributed throughout the body.
8. Tissues use up oxygen, blood becomes oxygen-poor, and the cycle repeats.

Heart Valves

• Atrioventricular (AV) Valves:
  • Allow blood to flow in one direction (atria to ventricles)
  • Valves open as blood is pumped through
  • Close to prevent blood flow back (backflow)
  • Held in place by chordae tendineae ("heart strings")
  • Two AV valves: Mitral/bicuspid (left side) and Tricuspid (right side)
• Semilunar Valves:
  • Allow blood to flow out of the ventricles
  • Three semilunar valves: Pulmonary (right side) and Aortic (left side)

Heart Operation of AV Valves

• Blood entering atria puts pressure on AV valves, forcing them open
• Ventricles fill with blood
• Atria contract, forcing the rest of the blood into the ventricles
• Ventricles contract, pushing against AV valve flaps; AV valves close
• Chordae tendineae tighten, preventing valve flaps from inverting into atria
• Ventricles relax; pressure decreases; blood flows back from arteries, closing the semilunar valves

Heart Sounds

• Using a stethoscope, two sounds are heard during each cardiac cycle: "lub-dup"
  • "Lub": Closing of the AV valves
  • "Dup": Closing of the semilunar valves

Cardiac Cycle

• Events of one complete heartbeat
  • Atria contract simultaneously
  • Atria relax, ventricles contract
  • Contraction = Systole
  • Relaxation = Diastole

Heart Conduction System

• Heart beats controlled by an intrinsic conduction system, allowing heart muscle cells to contract without nerve impulses
• Special tissue (no where else in body)
  • Sinoatrial node (SA node: pacemaker)
  • Atrioventricular node (AV node)
  • Atrioventricular bundle
  • Bundle branches
  • Purkinje fibers