THE CARDIOVASCULAR SYSTEM

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THE CARDIOVASCULAR SYSTEM
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Size, Shape and Position

• Located in mediastinum, between lungs
• Base - broad superior portion of heart
• Apex - inferior end, tapers to point
• 3.5 in. wide at base, weighs 10 oz

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Heart structure

• The human heart is divided into four chambers.
  The upper chambers (atria) are separated from the
  lower chambers (ventricles) by valves.
• The heart is further divided into left and right
  halves by walls. The wall separating the atria
  is the interatrial septum.
• The ventricles are separated by the
  interventricular septum.

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Purpose

• The hearts function is to serve as a circulation
  pump. It actually circulates blood through two
  circuits in series The Systemic and the
  Pulmonary circuits.

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Major vessels of the Heart

• Superior vena cava and inferior vena cava
• Empty into RA from systemic circulation
• Aorta
• Carries blood from LV into systemic circ.
• Pulmonary trunk
• From RV to pulmonary arteries to lungs
• Pulmonary veins
• From lungs to LA

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Heart valves

• Tricuspid valve separates R. atrium from R.
  ventricle
• Pulmonary valve separates RV from pulmonary
  trunk (artery)
• Bicuspid (mitral) valve separates L. atrium
  from L. ventricle
• Aortic valve separates LV from Aorta

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Why are valves important?

• They are essential in maintaining blood flow in
  the proper direction
• Valves close after the chamber preceding it
  empties, preventing backflow.
• Improperly functioning valves can lead to blood
  regurgitating into previous chamber, which can be
  harmful if significant.

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External Anatomy-Anterior View
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Posterior view
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• The heart is contained within a sac called the
  pericardium
• Protects the heart and improves function
• Composed of two layers

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Pericardial layers

• Fibrous pericardium
• Outermost portion of sac
• Limits movement of heart and protects it
• Attaches to diaphragm and sternum

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Pericardium contd

• Serous pericardium
• Composed of two layers which form a space
• One layer attaches to inner lining of fibrous
  pericardium other layer covers the heart (also
  called epicardium)
• Space is filled with pericardial fluid (approx 30
  ml, or one fl. Oz.) acts as lubricant to aid in
  heart motion

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Heart Wall

• Epicardium
• membrane covers heart
• Myocardium
• thick muscular layer
• Endocardium
• smooth inner lining

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Pericardium and Heart Wall
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Anatomy of the Heart
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Blood flow

• Right atrium-tricuspid valve-right
  ventricle-pulmonary valve pulmonary trunk
  pulmonary arteries - lungs
• Lungs pulmonary veins - left atrium mitral
  (bicuspid) valve left ventricle aortic valve
  aorta systemic circulation superior or
  inferior vena cava right atrium.

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Blood flow cycle
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• Vessels that carry blood away from the heart are
  always arteries
• Vessels that carry blood towards the heart are
  always veins

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