CARDIOVASCULAR SYSTEM

Replacing hearts -

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Cardiovascular System Functions

The cardiovascular system allows exchange of oxygen and carbon dioxide between blood and tissues

Accomplished by three components:1. Heart – pump blood2. Vessels – transport network; arteries, veins

and capillaries3. Blood – transports dissolved gases, nutrients,

hormones and metabolic wastes

Organization of Cardiovascular System

1. Systemic Circuit – oxygenated blood leaves the heart through the aorta and returns to the heart through systemic veins

2. Pulmonary Circuit– deoxygenated blood leaves the heart through pulmonary arteries and returns to the heart through pulmonary veins

A closed system with two circuits

The Heart…size, shape and location

Muscular organ composed of cardiac muscle

About the size of a closed fist Weighs less than a pound Located within the thoracic cavity Flanked on either side by the lungs

The heart…coverings and wall

Pericardium = double walled sac around the heart Protects the heart and anchors it to

surrounding structures Produces a lubricating fluid to create a

frictionless environment Pericarditis = inflammation of the

pericardium

The heart…coverings and wall

The wall of the heart is composed of three layers:1. Epicardium = continuous with the

pericardium2. Myocardium = thick bundles of cardiac

muscle; the contractile part of the heart3. Endocardium = think sheet of

endothelium that lines the heart chambers

The heart…coverings and wall

Anatomy of the heart

4 chambers Upper chambers = atria = receiving chambers Lower chambers = ventricles = pumping

chambers Left ventricle forms the apex or point of the heart Interventricular septum divides ventricles

Chambers – Anterior View

Left atriumRight

atrium

Right Ventricle

Left Ventricle

Chambers – Posterior View

Left atrium Right atrium

Right Ventricle

Left Ventricle

Chambers – Internal View

Left atriumRight

atrium

Right Ventricle

Left Ventricle

Anatomy of the heart

Heart Valves permit flow of blood in one direction

1. AV valves divide atria and ventricles; prevent backflow of blood into atria when ventricles contract

Bicuspid valve (mitral valve) – between left atria and left ventricle

Tricupsid valve between right atria and right ventricle Chordae Tendinae = tiny white cords that anchor

the valves to the walls of the ventricleLAB RAT…Left Atrium Bicuspid

Right Atrium Tricuspid

AV Valves

Anatomy of the heart

Heart Valves permit flow of blood in one direction

2. Semilunar valves guard the large vessels leaving the ventricles; prevents arterial blood from falling back into the ventricles

Pulmonary semilunar valve Aortic semilunar valve

Semilunar Valves

Anatomy of the heart

Great Vessels of the Heart Superior and inferior vena cava – take

deoxygenated blood from the body to the right atrium

Pulmonary trunk gives rise to Pulmonary arteries (left and right) – take deoxygenated blood from right ventricle to lungs for oxygen

Pulmonary veins (left and right) – takes oxygenated blood from lungs to left atrium

Aorta – takes blood away from left ventricle to rest of body

Anatomy of the heart

Cardiac Circulation Coronary arteries branch from the base of the

aorta and encircle the heart at the junction between the atria and ventricles Compressed when ventricles are contracting and fill

when the ventricles are relaxed Cardiac veins drain the myocardium into the

right atrium

Vessels – Anterior View

Superior vena cava

Inferior vena cava

L. Pulmonary artery

L. Pulmonaryveins

R. Pulmonaryveins

aorta

Pulmonary trunkR. Pulmonary artery

Coronary vessels

Vessels – posterior view

Superior vena cava

Inferior vena cava

R. Pulmonary veins

aortaR. Pulmonary arteryL. Pulmonary

arteryL. Pulmonaryveins

Coronary vessels

When the heart beats

The Right side of the heart Deoxygenated blood flows into heart from vena

cava Right atrium Tricuspid valve Right ventricle Pulmonary semilunar valve Pulmonary artery Lungs (to pick up oxygen)

What’s behind a heartbeat

The Left side of the heart Oxygenated blood flows into heart from lungs via

pulmonary veins Left atrium Bicuspid valve (aka mitral valve) Left ventricle Aortic semilunar valve Aorta Body (to deliver oxygen)

Control of Heart Contraction

General info about cardiac muscle Cardiac muscle cells contract spontaneously

and independently, even if all nervous connections are cut

Muscle cells in different areas of the heart have different rythms Atria cells contract at a faster rate than ventricular

cells An intrinsic control system regulates activity

Intrinsic Control System

Intrinsic conduction system Sinoatrial node (SA node) Atrioventricular node (AV node) Bundle of His Purkinje Fibers

Sinoatrial Node (SA node)

The pacemaker of the heart Located in right atrium SA node sends out electrical impulse Impulse spreads over atria, making them

contract Impulse travels to AV node

Atrioventricular node (AV node) Conducting cell group between atria and

ventricle Carries impulse to bundle of His

Bundle of His

Conducting fibers in septum (divider between left and right sides of the heart

Divides into right and left branches to a network of b ranches in ventricles (Purkinje Fibers)

Purkinje Fibers

Impulse shoots along Purkinje fibers causing ventricles to contract

Electrocardiogram (EKG or ECG) Device used to record the electrical

activity of the heart Systole = contraction phase Diastole = relaxation phase

Baseline of EKG is flatline P = atrial contraction QRS = ventricular contraction T = ventricular relaxation