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Physiology - Cardiovascular System

Cardiovascular System

Definition: a powerful pump (heart) with series of tubes (blood vessels) supplying oxygen and nutrients to body cells and remove wastes

Heart Location

  • Within mediastinum
  • Bordered laterally by lungs
  • Anterior to vertebral column
  • Posterior by sternum

Heart Structure

  • Approx. 14 cm long and 9 cm wide
  • Base: attaches to large blood vessels below second rib
  • Apex: distal endpoint left at the 5th intercostals space

Covering and Walls of Heart (From outer to inner)

Fibrous Pericardium

Parietal Pericardium

Pericardial Cavity

Visceral Pericardium (Epicardium)



Pericardium: membrane that encloses heart and proximal ends of large blood vessels

            Fibrous: outer layer, made of dense connective tissue

            Parietal: middle layer

            Visceral: inner layer also known as epicardium

            Pericardial sac: parietal pericardium and fibrous pericardium

Pericardial cavity: space between visceral and partial, with serous fluid to reduce friction of these membranes

Epicardium: outer wall of the heart, reduces friction, consists of: connective tissue, epithelium, adipose tissue, coronary arteries and cardiac veins

Myocardium: middle wall of heart, consists of cardiac muscles, separated by connective tissue, blood capillaries, lymph capillaries, nerve fibers. Pumps blood of heart.

Endocardium: inner wall of the heart, consists of epithelium, connective tissue, elastic ad callogenous fibers, blood vessels and Purkinje fibers.

Flow of Blood:


Superior and inferior vena cava, coronary sinus


Right atria: receives blood from superior and inferior vena cava (ie. From body cells), coronary sinus


Tricuspid valve: opening between right atrium and right ventricle. Prevents blood from moving from right ventricle into right atrium during ventricular contraction


Right ventricle


Pulmonary valve: entrance to pulmonary trunk. Prevents blood from moving from pulmonary trunk into right ventricle during ventricular relaxation


Pulmonary trunk


Pulmonary arteries


Alveolar capillaries: exchange carbon dioxide and oxygen with alveoli


Pulmonary vein


Left atria


Bicuspid (mitral) valve: opening between left atrium and left ventricle. Prevents blood from moving from left ventricle into left atrium during ventricular contraction


Left ventricle


Aortic valve: 3 cusps, entrance to aorta. Prevents blood from moving from aorta into left ventricle during ventricular relaxation


Aorta: very large artery


Systemic capillaries: exchange carbon dioxide and oxygen with tissue cells

  • atrioventricular (AV) valve: bicuspid and tricuspid valves ensuring one-way blood flow between atria and ventricles
  • semilunar valve: aortic and pulmonary valve

Atria vs Ventricles

Atria: 2 chambers at the top of heart, have thin walls, receive blood returning to heart

Ventricles: lower 2 chambers of the heart, thicker walls (left thicker than right), receive blood from atria, contract to force blood out of heart

Septum: divides the atrium and ventricle from left and right


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