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The Cardiovascular System

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Cheryl Stover

on 27 February 2013

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Transcript of The Cardiovascular System

A closed system of the heart and blood vessels
The heart pumps blood
Blood vessels allow blood to circulate to all parts of the body
The function of the cardiovascular system is to deliver oxygen and nutrients and to remove carbon dioxide and other waste products Fibrous pericardium is loose and superficial
Serous membrane is deep to the fibrous pericardium and composed of two layers
-Visceral pericardium: next to heart; also known as the epicardium
-Parietal pericardium: outside layer that lines the inner surface of the fibrous pericardium
Serous fluid fills the space between the layers of pericardium Epicardium: visceral layer of serous pericardium
Myocardium : cardiac muscle layer is the bulk of the heart
Endocardium: chamber lining & valves
Four chambers
-Receiving chambers: Right atrium & Left atrium
 Ventricles
-Discharging chambers: Right ventricle & Left ventricle
Heart valves
Allow blood to flow in only one direction
Four valves
Atrioventricular valves – between atria and ventricles
Bicuspid valve (left)
Tricuspid valve (right)
Semilunar valves between ventricle and artery
Pulmonary semilunar valve
Aortic semilunar valve
Allow blood to flow in only one direction to prevent backflow
Four valves
Atrioventricular (AV) valves—between atria and ventricles
Bicuspid (mitral) valve (left side of heart)
Tricuspid valve (right side of heart)
Semilunar valves—between ventricle and artery
Pulmonary semilunar valve
Aortic semilunar valve
AV valves
Anchored in place by chordae tendineae (“heart strings”)
Open during heart relaxation and closed during ventricular contraction
Semilunar valves
Closed during heart relaxation but open during ventricular contraction
Notice these valves operate opposite of one another to force a one-way path of blood through the heart
Heart murmurs are most often caused by defective heart valves.
A valve may be unable to close completely.
This leads to regurgitation, which is blood leaking backward through the valve when it should be closed
-Leaves left ventricle
Pulmonary arteries
-Leave right ventricle
Superior and inferior venae cavae
-Enter right atrium
Pulmonary veins (four)
-Enter left atrium
Transport blood to the tissues and back
Carry blood away from the heart
Exchanges between tissues and blood
Capillary beds
Return blood toward the heart
Veins Cells fire spontaneously, act as pacemaker and form conduction system for the heart
SA node
cluster of cells in wall of Rt. Atria  begins heart activity that spreads to both atria  excitation spreads to AV node
AV node
in atrial septum, transmits signal to bundle of His
AV bundle of His 
the connection between atria and ventricles divides into
Bundle branches &
Purkinje fibers
large diameter fibers that conduct signals quickly At 75 beats/min, one cycle requires 0.8 sec.
systole (contraction) and diastole (relaxation) of both atria, plus the systole and diastole of both ventricles
Stroke volume (SV)
the volume ejected per beat from each ventricle, about 70ml
 BP is affected by age, weight, time of day, exercise, body position, emotional state
CO is the amount of blood pumped out of the left ventricle per minute
PR is peripheral resistance
the amount of friction blood encounters as it flows through vessels
Narrowing of blood vessels and increased blood volume increases PR
BP = CO x PR
Neural factors
Autonomic nervous system adjustments (sympathetic division)
Renal factors
Regulation by altering blood volume
Renin—hormonal control
Heat has a vasodilating effect
Cold has a vasoconstricting effect
Various substances can cause increases or decreases Heart
Physiology The Cardiovascular System The Heart: Coverings Pericardium Fibrous Pericardium Parietal Pericardium Visceral Pericardium (epicardium) Myocardium Endocardium Layers of Heart Wall Circulatory System Cardiac Cycle The Heart: Internal Anatomy The Heart: Associated Great Vessels Heart Murmur The Heart: Valve Function Aorta Pulmonary
Trunk Pulmonary
Artery Pulmonary
Artery Superior
Cava Brachiocephalic
Artery L. Common
Artery L. Subclavian
Artery Pulmonary
Veins Pulmonary
Veins R. Atrium L. Atrium Pulmonary Valve Valve Aortic Tricuspid
Valve Bicuspid
Valve Chordae
Tendinae Chordae
Tendinae Papillary
Muscles Papillary
Muscles Papillary
Muscles L. Ventricle Myocardium Interventricular Septum Inferior
Cava Aorta Types of Blood Vessels
Three layers (tunics)
 Tunic intima
 Tunic media
Smooth muscle
Controlled by sympathetic nervous system
 Tunic externa
Mostly fibrous connective tissue Lumens of veins are larger
Larger veins have valves to prevent backflow
Skeletal muscle “milks” blood in veins toward the heart
Walls of capillaries are only one cell layer thick to allow for exchanges between blood and tissue Most arterial blood is pumped by the heart
Veins use the milking action of muscles to help move blood
Movement of Blood Through Vessels Differences Between Blood Vessels Blood Vessels The Heart Lumen Lumen Artery Vein Tunica Intima Tunica Intima Tunica Media Tunica Media Tunica Externa Tunica Externa Tunica Externa Tunica Intima Lumen Capillary Bed Venule Arteriole Valve Conduction System of Heart
Action potentials of all active cells can be detected and recorded
P wave
atrial depolarization
P to Q interval
conduction time from atrial to ventricular excitation
QRS complex
Ventricular depolarization
T wave
ventricular repolarization
SA node fires spontaneously 90-100 times per minute
AV node fires at 40-50 times per minute
If both nodes are suppressed fibers in ventricles by themselves fire only 20-40 times per minute
Artificial pacemaker needed if pace is too slow
Extra beats forming at other sites are called ectopic pacemakers
 caffeine & nicotine increase activity Rhythm of Conduction System Autorhythmic Cells SA
Node 90-100 AV
Node 40-50 AV Bundle R. Bundle Branch L. Bundle Branch Purkinje Fibers Purkinje Fibers Purkinje Fibers Purkinje Fibers 20-40 Depolarization Depolarization Electrocardiogram---ECG or EKG Cardiac Cycle (1 Hearbeat) Cardiac output (CO)
Amount of blood pumped by each side (ventricle) of the heart in one minute
Stroke volume (SV)
Volume of blood pumped by each ventricle in one contraction (each heartbeat)
Usually remains relatively constant
About 70 mL of blood is pumped out of the left ventricle with each heartbeat
Heart rate (HR)
Typically 75 beats per minute
Cardiac Output(CO) = HR  SV
CO = HR (75 beats/min)  SV (70 mL/beat)
CO = 5250 mL/min
Starling’s law of the heart—the more the cardiac muscle is stretched, the stronger the contraction
Changing heart rate is the most common way to change cardiac output
Normal:60-75 Beats/Minute
Increased heart rate
Sympathetic nervous system
Low blood pressure
Decreased blood volume
Decreased heart rate
Parasympathetic nervous system
High blood pressure or blood volume
The Heart: Regulation of Heart Rate Heart is relaxed
Blood passing through atria and filling ventricles SA node fires and atria contract
Forces more blood into ventricles AV valves open
Semilunar shut AV valves open
Semilunar shut Purkinje fibers fire and ventricles contract
Pressure in ventricles increases
AV valves shut (LUB) AV shut
Semilunar shut Ventricles continue tocontract
Pressure in ventricles increases
Semilunar valves open
Blood ejected (stroke volume) AV shut
Semilunar open Ventricles relax
Pressure in ventricles decreases
Semilunar valves shut (DUP)
As interventricular pressure continues to decrease AV valves open and the cycle starts again AV shut
Semilunar shut The Heart: Cardiac Output Blood Pressure (BP) Measurements by health professionals are made on the pressure in large arteries
Systolic – pressure at the peak of ventricular contraction
Diastolic – pressure when ventricles relax
Pressure in blood vessels decreases as the distance away from the heart increases Blood Pressure: Effects of Factors Human normal range is variable
Below 120 mm hg systolic
Below 80mm hg diastolic
Low systolic (below 110 mm hg)
Often associated with illness
High systolic (above 140 mm hg)
Can be dangerous if it is chronic Variations in Blood Pressure muscles massage veins pressure changes diameter of veins smaller The Structure of the Heart Valves and Blood Flow How the Heart Works Cardiac Output Conduction System How to Read an EKG R. Ventricle Microscopic Anatomy
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