3.4.2.1 The Heart

• Humans have a double, closed circulatory system
• Pulmonary Circulatory System - right side of heart; carries deoxygenated blood to lungs for gas exchange
• Systematic Circulatory System - left side of heart; returns oxygenated blood to be pumped around the body at high pressures
• Cardiac Muscle - a thick muscular layer that make up the walls of the heart; myogenic; never fatigues as long as there is a supply of glucose & oxygen
• Myogenic - the ability to contract and relax without nervous or hormonal stimulation
• Coronary Arteries

  • Supplies cardiac muscle with oxygenated blood
  • Branches off from aorta
• When the coronary arteries are blocked, cardiac muscle will not recieve oxygen and therefore will be unable to respire causing cells to die (results in a myocardial infraction)
• Four Chambers


  • Right & Left Atrium
  • Right & Left Ventricles

  
• Atria/Atrium


  • Thinner muscular walls (do not need to contract as hard)
  • Elastic walls which can stretch when blood enters
• Ventricles


  • Thicker muscular walls (allows harder contract)
  • Creates higher blood pressure to allow blood flow to longer distances
• Right Ventricle


  • Pumps blood to lungs
  • Low pressure (prevents damage to capillaries)~
  • Allows time for gas exchange
  • Thinner muscular wall compared to LV
• Left Ventricle


  • Pumps blood to body
  • Larger contractions = high pressure
  • Ensures blood reaches all cells
  • Thicker muscular wall compared to RV
• The 4 Main Blood Vessels connected to the Heart

  • Aorta
  • Vena Cava (Superior & Inferior)
  • Pulmonary Artery
  • Pulmonary Vein
• Aorta - connected to left ventricle; carries oxygenated blood to all parts of the body except for the lungs
• Vena Cava - connected to right atrium and brings deoxygenated blood back from tissues of the body except for lungs
• Pulmonary Artery - connected to right ventricle and carries deoxygenated blood to lungs (unusual)
• Pulmonary Vein - connected to left atrium and brings oxygenated blood back from lungs (unusual)
• Two Types of Valves


  • Atrioventricular valves
  • Semi-lunar valves
• Atrioventricular Valves - bicuspid (left), tricuspid (right), between ventricle and atrium [high pressure above forces them...]
• Semi-Lunar Valves - aortic and pulmonary valves; also in veins; ensures blood flows to heart
• Valves

  • Prevents back flow
  • Tough, flexible cusp shaped flaps
  • Open when pressure is high behind valve
• Carry Deoxygenated Blood =

  • Vena Cava
  • Right Atrium
  • Tricuspid Valve
  • Right Ventricle
  • Pulmonary Valve
  • Pulmonary Artery
• Carry Oxygenated Blood =

  • Pulmonary Vein
  • Left Atrium
  • Bicuspid Valve
  • Left Ventricle
  • Aortic Valve
  • Aorta
• Ventricle walls are thicker than atrial walls
• Double Circulatory System

  • Allows high pressure to be maintained
  • Pumps blood twice
• • Single system would have a large SA of lung capillaries and decrease pressure; less oxygenated blood delivered to tissues