Aristotle

Galen of Pergamum and Pneuma Zoticon

DaVinci

WILLIAM HARVEY (1628)

How has the actual anatomy of the heart changed over time?

Open v. Closed Circulatory System

• OPEN• Pro: Simple• Con: Low Efficiency

• CLOSED• Pro: High Efficiency• Con: Complex Needs

Why Are Massive Insects Not Possible?

• Size of organism limited by type of circulatory system• Large organisms cannot survive

with open circulatory system due to limitations of the pumping apparatus

Evolution of The Heart

• Trend towards increased separation of oxygenated and deoxygenated blood• Increased separation of blood

facilitates increased activity, terrestrial lifestyle and homeothermic regulation

The Human Heart At Work

• 72 contractions/min = 2.5 billion/lifetime• 60,000 miles/day• 1.5 million gallons/lifetime• Enough energy expended in a lifetime to drive a pickup truck to the

moon and back

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Orientation of Heart

• Size of fist? Depends upon age and health• Apex of heart (inferior tip) is just

superior to the diaphragm at the lower end of the thoracic cavity• Heart points sinister and 2/3rds

of heart mass is sinister to the midline

Pericardium

• Covers and nourishes the myocardium• Serous fluid-lubricates

heart/reduces friction

Anatomy of the Heart Wall

• Epicardium-Parietal layer of pericardium

• Myocardium – made of intercalated cardiomyocytes

• Endocardium-made of epithelial (skin) cells that prevent blood from sticking to inner wall (clotting)

Myocardial Thickness

• Right Side = thin• Blood only pumping to lungs or

right ventricle

• Left side = thick• Blood pumped to systemic

circulation and extremities

Atria (Auricles)

• Left Atrium• Receives deoxygenated blood

from body via vena cava

• Right Atrium• Receives oxygenated blood from

lungs via pulmonary vein/valve

Ventricles

• Right Ventricle• Receives blood from right atrium

• Left Ventricle• Receives blood from left atrium

Ventricular Septum

• Separates right and left ventricle• Prevents mixing of oxygenated

and deoxygenated blood

Cardiac Valves

• Function: to prevent the backwards flow of blood through coronary circulation

Atrioventricular Valves

• Tricuspid Valve• Separates right atrium from right

ventricle

• Bicuspid (Mitral) Valve• Separates left atrium from left

ventricle

Chordae Tendinae Cordis

• Tendons that open and shut the tricuspid and bicuspid valves• Attached to leaflets (valve flaps)

and anchored to epicardium covering the papillary muscles

Mitral Valve Prolapse

• Chordae tendinae fail to close the leaflets of the bicuspid valve• Blood regurgitates from the left

ventricle back into the left atrium

Semilunar Valves

• Crescent shaped cusps • Lack Chordae Tendinae/Closed by

Blood Pressure Alone• Valves located on structures ejecting

blood away from the heart• Pulmonary Semilunar Valve = right

atrium• Aortic Semilunar = left atrium

Coronary Circulation