Cardiovascular system

• cardiovascular system is a highly complex system that includes the heart and a closed system of blood vessels.
• HEART is a hollow, muscular organ about the size of a closed fist.
• Heart is located between the lungs in the mediastinum, behind and to the left of the sternum.
• Heart spans the area from the second to the fifth intercostal space. Its right border aligns with the right border of the sternum. The left border aligns with the left midclavicular line.
• Precordium - The part of the front of the chest wall that

  overlays the heart and the epigastrium
• Mediastinum - The central compartment of the thoracic cavity surrounded by loose connective tissue, as region that contains a group of structures within the thorax.
• HEART

  Positioned obliquely between the lungs in the

  mediastinum.

  Lies in the pericardial cavity
• The large veins and arteries leading directly to and away from the heart are referred to as the great vessels.
• superior and inferior vena cava return

  blood to the right atrium from the upper

  and lower torso respectively.
• pulmonary artery exits the right

  ventricle, bifurcates, and carries blood to

  the lungs.
• aorta transports oxygenated blood

  from the left ventricle to the body .
• pulmonary veins (two from each lung)

  return oxygenated blood to the left atrium.
• four chambers or cavities:

  two upper chambers: the right and left atria

  two lower chambers: the right and left ventricles
• right and left sides of the heart are

  separated by a partition called the SEPTUM.
• thin-walled atria receive blood returning

  to the heart and pump blood into the

  ventricles.
• thicker-walled ventricles pump blood out

  of the heart. The left ventricle is thicker than

  the right ventricle because the left side of the

  heart has a greater workload.
• Atrium

  • The top chambers of the heart
  • They are the receiving chambers of blood returning from circulation
  • They are smaller since they only push blood to the ventricles “next door”
• Ventricles

  • They are larger and make up most of the mass of the heart
  • They are the lower chambers in the heart
  • They are the discharging chambers that actually pump blood to the body
  • The right pumps to the pulmonary circuit (lungs)
  • The left pumps to the systemic circuit (all body tissue)
• Valves in the heart keep blood flowing in only one direction through the heart. Healthy valves open and close passively as pressure changes within the four heart chambers.
• Valves between the atria and ventricles are called atrioventricular valves and include the tricuspid valve on the right side of the heart and the mitral valve on the left.
• pulmonic valve (between the right ventricle and pulmonary artery) and the aortic valve (between the left ventricle and the aorta) are called semilunar valves.
• Four valves ensure the one-way flow of blood in the heart
• Atrioventricular Valve – valves in between the atria and ventricles

  ▪ Tricuspid Valve

  ▪ Bicuspid (Mitral valve)
• Semilunar Valves - valves of the heart, at the bases of the aorta and the pulmonary artery

  ▪ Pulmonic Semilunar Valves

  ▪ Aortic Semilunar Valves
• The space between the two layers (the pericardial space) contains

  10 to 20 ml of serous fluid, which lubricates and cushions the surface of the heart and prevents friction between the layers as the heart pumps.
• PERICARDIUM is a thin sac with an inner, or visceral, layer that forms the epicardium and an outer, or parietal, layer that protects the heart.
• Parietal Pericardium: secretes a small amount of pericardial fluid that allows for smooth, friction-free movement of the heart
• Epicardium: serous membrane covers the outer surface of the heart
• Walls of the Heart

  Epicardium (outer layer)

  Myocardium (middle layer)

  Endocardium (inner layer)
• Chordae Tendinae

  •Tendinous cords

  •Colloquially known as the heart strings

  •Tendon-resembling fibrous cords of connective tissue that connect the papillary muscles to the tricuspid valve and the bicuspid valve in the heart.
• Coronary System

  •Circulation of blood that supply oxygen to the myocardium

  •Coronary arteries

  •Coronary veins
• Properties of the myocardial cells:

  Rhythmicity – regularity of impulse transmission

  Automaticity – ability to initiate electrical impulses

  Conductivity – ability to transmit electrical impulses from one cell to another

  Contractility – ability to contract in response to the flow of electrical impulse

  Excitability – ability to respond to electrical stimuli
• Cardiac muscle cells have a unique inherent ability. They can spontaneously generate an ELECTRICAL IMPULSE and conduct it through the heart.

  The generation and conduction of electrical impulses by specialized sections of the myocardium regulate the events associated with the filling and emptying of the cardiac chambers. The process is called the CARDIAC CYCLE.
• sinoatrial node (or sinus node) is located on the posterior wall of the right atrium near the junction of the superior and inferior vena cava.
• AV node (atrioventricular node) located in the lower interatrial septum.