Structure and Function of Structure and Function of the Heartthe Heart

Pathophysiology Pathophysiology

October 11, 2004October 11, 2004

Heart FactsHeart Facts

Put your hand on your heart. Did you place Put your hand on your heart. Did you place your hand on the left side of your chest? your hand on the left side of your chest? Many people do, but the heart is actually Many people do, but the heart is actually located almost in the center of the chest, located almost in the center of the chest, between the lungs. It's tipped slightly so between the lungs. It's tipped slightly so that a part of it sticks out and taps against that a part of it sticks out and taps against the left side of the chest, which is what the left side of the chest, which is what makes it seem as though it is located there.makes it seem as though it is located there.

Your heart beats about 100,000 times Your heart beats about 100,000 times in one day and about 35 million times in one day and about 35 million times in a year. During an average lifetime, in a year. During an average lifetime, the human heart will beat more than the human heart will beat more than 2.5 billion times. 2.5 billion times.

The aorta, the largest artery in the The aorta, the largest artery in the body, is almost the diameter of a body, is almost the diameter of a garden hose. Capillaries, on the other garden hose. Capillaries, on the other hand, are so small that it takes ten of hand, are so small that it takes ten of them to equal the thickness of a them to equal the thickness of a human hair.human hair.

Your body has about 5.6 liters (6 quarts) of Your body has about 5.6 liters (6 quarts) of blood. This 5.6 liters of blood circulates blood. This 5.6 liters of blood circulates through the body three times every through the body three times every minute. In one day, the blood travels a minute. In one day, the blood travels a total of 19,000 km (12,000 miles)--that's total of 19,000 km (12,000 miles)--that's four times the distance across the US from four times the distance across the US from coast to coast.coast to coast.

lub-DUB, lub-DUB, lub-DUB. Sound lub-DUB, lub-DUB, lub-DUB. Sound familiar? If you listen to your heart beat, familiar? If you listen to your heart beat, you'll hear two sounds. These "lub" and you'll hear two sounds. These "lub" and "DUB" sounds are made by the heart "DUB" sounds are made by the heart valves as they open and close. valves as they open and close.

Heart AnatomyHeart Anatomy

Location: mediastinumLocation: mediastinum

Surrounded by: pericardial sacSurrounded by: pericardial sac

Composed of: cardiac muscleComposed of: cardiac muscle Epicardium contains lubricating fluid to Epicardium contains lubricating fluid to

faciliate heart movementfaciliate heart movement Mycardium is the cardiac muscleMycardium is the cardiac muscle Endocardium is the inner layer that forms heart Endocardium is the inner layer that forms heart

valvesvalves

External StructureExternal Structure

Four chambers:Four chambers: 2 Upper: Atria2 Upper: Atria

Blood enters the heartBlood enters the heart 2 Lower: Ventricles2 Lower: Ventricles

Blood leaves the heartBlood leaves the heart

Two halves Two halves separated by the separated by the septumseptum

Internal StructureInternal Structure

Atrioventricular (AV) Atrioventricular (AV) valves separate the valves separate the atria and ventriclesatria and ventricles Right: tricuspidRight: tricuspid Left: mitral (bicuspid)Left: mitral (bicuspid)

Semilunar valves at Semilunar valves at the exits of the the exits of the aorta and pulmonary aorta and pulmonary arteryartery

Blood Flow (Right side)Blood Flow (Right side)

Deoxygenated blood enters through Deoxygenated blood enters through the VENA CAVAEthe VENA CAVAE

Passes through the RIGHT ATRIUMPasses through the RIGHT ATRIUM It then passes through the TRICUSPID It then passes through the TRICUSPID

VALVE and enters the RIGHT VALVE and enters the RIGHT VENTRICLEVENTRICLE

It leaves the heart through the It leaves the heart through the PULUMONARY ARTERIES where it goes PULUMONARY ARTERIES where it goes to the lungs to pick up OXYGENto the lungs to pick up OXYGEN

Blood Flow (Left side)Blood Flow (Left side)

Oxygen rich blood enters the heart Oxygen rich blood enters the heart through the PULMONARY VEINSthrough the PULMONARY VEINS

It passes through the LEFT ATRIUMIt passes through the LEFT ATRIUM It moves through the MITRAL VALVE It moves through the MITRAL VALVE

and enters the LEFT VENTRICLEand enters the LEFT VENTRICLE It will leave the heart through the It will leave the heart through the

AORTA to deliver oxygen rich blood to AORTA to deliver oxygen rich blood to the bodythe body

Conduction SystemConduction System

Electrical impulses from your Electrical impulses from your heart muscle cause it to beat heart muscle cause it to beat (contract). (contract).

This electrical signal begins in This electrical signal begins in the the sinoatrial (SA) nodesinoatrial (SA) node, , located at the top of the right located at the top of the right atrium. The SA node is atrium. The SA node is sometimes called the heart's sometimes called the heart's ""natural pacemakernatural pacemaker." ."

When an electrical impulse is When an electrical impulse is released from this natural released from this natural pacemaker, it causes the pacemaker, it causes the atria atria to contract. to contract.

The signal then passes through The signal then passes through the the atrioventricular (AV) atrioventricular (AV) nodenode. The AV node checks the . The AV node checks the signal and sends it through the signal and sends it through the muscle fibers of the ventricles, muscle fibers of the ventricles, causing them to contract.causing them to contract.

The Heartbeat – Two pumping The Heartbeat – Two pumping ActionAction

When the SA Node When the SA Node causes the atria to causes the atria to contract, blood is contract, blood is pushed through the pushed through the tricuspid and mitral tricuspid and mitral valves into the resting valves into the resting ventricles. ventricles.

This part of the two-This part of the two-part pumping phase part pumping phase (the longer of the two) (the longer of the two) is called the is called the diastolediastole. .

The second part of the The second part of the pumping phase begins pumping phase begins when the ventricles when the ventricles are full of blood. The are full of blood. The electrical signals from electrical signals from the SA node travel the SA node travel along a pathway of along a pathway of cells to the ventricles, cells to the ventricles, causing them to causing them to contract. This is called contract. This is called systolesystole. .