Cardiovascular System

Heart

Introduction of Cardiovascular Sytem  1.

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Consists of; Blood Heart Blood Vessels

Location of Heart  Heart lies between the lungs in the mediastinum.

Location of Heart  Two-thirds of its mass is to the left of the midline

Location of Heart  Precordium – The area of the chest anterior to the heart

Location of Heart  Lies between the vertebral column and the sternum

Structure and Function of Heart 1.

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Pericardium Layers of the Heart Wall

Pericardium  The heart is enclosed and held in place by the pericardium

Pericardium  1.

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Consists of; Fibrous pericardium (outer) Serous pericardium (inner)

Pericardium  Fibrous pericardium – anchors the heart in the mediastinum

Pericardium  1.

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Serous pericardium composed of; Parietal layer Visceral layer

Pericardium  Pericardial cavity – a space between the parietal and visceral layers filled with pericardial fluid

Layer of the Heart 1.

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Epicardium Myocardium Endocardium

Epicardium  Consists of the visceral layer of pericardium and connective tissue (adipose)

Myocardium  Composed of cardiac muscle

Myocardium  The cells are branched, involuntary, and have one nucleus

Myocardium  The cells are connected by intercalated discs, which have gap junctions that allow ions to flow in between cells during depolarization

Endocardium  Lines the chambers and covers the connective tissue in the heart valves

Endocardium  It consists of endothelium

Chambers of the Heart 1.

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Right Atrium Right Ventricle Left Atrium Left Ventricle

Chambers of the Heart  On the surface of the heart are

auricles and sulci

Chambers of the Heart  Auricles – small pouches on the anterior surface of each atrium

Chambers of the Heart  Sulci – Are grooves that contain coronary arteries and fat and separate the chambers

Right Atrium  1.

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The right atrium receives systemic venous blood from; Superior Vena Cava Inferior Vena Cava Coronary sinus

Right Atrium  The atrium receives blood low in O2 and high in CO2

Right Atrium  Interatrial septum - separates the right and left atria

Right Atrium  Fossa ovalis – an oval depression in the interatrial septum; it is a remnant of the foramen ovale

Right Atrium  Tricuspid Valve – Blood passes from the right atrium into the right ventricle through here

Right Ventricle  Forms most of the anterior surface of the heart

Right Ventricle  Pulmonary semilunar valve - Blood passes from the right ventricle to the pulmonary trunk via this valve

Left Atrium  Receives pulmonary venous blood from the pulmonary veins which is rich in oxygen and low in CO2

Left Atrium  Mitral Valve – Blood passes from the left atrium to the left ventricle via this valve

Left Ventricle  Thickest and strongest chamber

Left Ventricle  Forms the apex of the heart

Left Ventricle  Blood passes from the left ventricle through the aortic valve into the aorta

Left Ventricle  During fetal life the ductus arteriosus shunts blood from the pulmonary trunk into the aorta

Left Ventricle  At birth the ductus arteriosus closes and becomes the ligamentum arteriosum

Left Ventricle  The left ventricle is separted from the right ventricle by the interventricular septum

Myocardial Thickness and Function  The atria walls are thin because they only pump blood to the nearby ventricles

Myocardial Thickness and Function  The ventricle wall are thicker because they pump blood greater distances

Myocardial Thickness and Function  The right ventricle walls are thinner than the left because they pump blood to the nearby lungs

Myocardial Thickness and Function  The left ventricle walls are thicker because they pump blood through the body

Function of Heart Valves  Valves open and close in response to pressure changes as the heart contracts and relaxes

Myocardial Thickness and Function  1.

2.

Two types of valves; Atrioventricular Valves Semilunar

Atrioventricular Valves 1.

2.

Tricuspid (right side) Mitral or bicuspid (left side)

Atrioventricular Valves  AV valves prevent blood flow from the ventricles back into the atria

Atrioventricular Valves  Back flow is prevented by the contraction of papillary muscles and tightening the chordae tendinae

Semilunar Valves  SL valves allow ejection of blood from the heart into the pulmonary arteries and aorta

Semilunar Valves  Prevent back flow into the ventricles

Circulation of Blood 1.

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Systemic Pulmonary Coronary

Systemic Circulation  The left side of the heart pumps oxygenated blood from the left ventricle into the ascending aorta.

Systemic Circulation  The coronary arteries arise off of the ascending aorta

Pulmonary Circulation  The right side of the heart receives deoxygenated blood from the body.

Pulmonary Circulation  The right side of the heart pumps blood from the right ventricle and sends it into the lungs via the pulmonary artery

Circulation of Blood  Right atrium receives blood from the superior and inferior vena cava

Circulation of Blood  The Left atrium receives blood from the pulmonary veins

Coronary Circulation  It delivers oxygenated blood and nutrients to and removes CO2 and wastes from the myocardium

Coronary Circulation  The

left and right coronary arteries

branch from the ascending aorta and carry oxygenated blood

Coronary Circulation  1.

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Left coronary artery branches into the; Left anterior descending artery Circumflex artery

Coronary Circulation  1.

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Right coronary artery branches into; Marginal artery Posterior descending artery

Coronary Circulation  Deoxygenated blood returns to the right atrium through the coronary sinus

Histology of Cardiac Muscle  In comparison to skeletal muscle fibers, cardiac muscle fibers are involuntary, shorter in length, larger in diameter, and squarish rather than circular in transverse section.

Histology of Cardiac Muscle  They also exhibit branching

Histology of Cardiac Muscle  Have same arrangement of actin and myosin, and the same bands, zones, and Z discs as skeletal muscles

Cardiac Conduction System  There is an atrial and ventricular network

Cardiac Conduction System  Fibers within the networks are connected by intercalated discs

Cardiac Conduction System  The intercalated discs allow the fibers to work together so that each network serves as a functional unit

Cardiac Conduction System  Cardiac muscle cells are autorhythmic cells because they are self-excitable.

Cardiac Conduction System  They repeatedly generate spontaneous action potentials that then trigger heart contraction

Cardiac Conduction System  1.

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The components of this system are; Sinoatrial node (SA) Atrioventricular node (AV) Bundle of His Right and Left Bundle branches Purkinje fibers

Cardiac Conduction System  SA node is the pacemaker

Cardiac Conduction System  From the SA node, a cardiac action potential travels throughout the atrial muscle and down to the AV node

Cardiac Conduction System  At the AV node the impulse is delayed (about 0.1sec)

Cardiac Conduction System  This gives the atria time to completely contract before ventricular contraction begins

Cardiac Conduction System  It then passes through the Bundle of His, Right and Left Bundle Branches, and the Purkinje fibers, resulting in ventricular contraction

Cardiac Cycle  1.

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Consists of; Systole (contraction) and Diastole (relaxation) of both atria Systole and Diastole of both ventricles

Atrial Diastole  The atria are relaxed

Atrial Diastole  They receive blood from three veins

Atrial Diastole  The A-V valves are open, allowing for 70% of ventricular filling. The ventricles are therefore also in diastole.

Atrial Systole  The SA node then fires; after this electrical event, atrial systole begins (a mechanical event)

Atrial Systole  Atrial contraction accounts for 30% of ventricular filling

Ventricular Systole  Shortly after the beginning of ventricular depolarization, ventricular systole begins

Ventricular Systole  The ventricles contract. The ventricular pressure becomes higher than atrial pressures, causing the AV valves to close.

Ventricular Systole  The SL valves open when the ventricular pressure becomes higher than aortic (pulmonary arterial) pressure.

Ventricular Systole  Then blood is ejected into the aorta and pulmonary trunk.

Ventricular Diastole  Begins when the ventricles relax

Ventricular Diastole  Ventricular pressures drop below arterial pressures, causing the SL valves to close

Ventricular Diastole  The ventricular pressures continue to drop below atrial pressures, causing the AV valves to open

Auscultation  Listening to sounds within the body with a stethoscope

Auscultation  The first heart sound (lubb) is created by the closing of the AV valves soon after ventricular systole begins

Auscultation  The second heart sound (dupp) represents the closing of the SL valves close to the end of the ventricular systole.

Cardiac Output  The volume of blood ejected from the left ventricle (or the right ventricle) into the aorta (or pulmonary trunk) each minute.

Cardiac Output  Cardiac Output = Stroke volume X Heart Rate

Cardiac Output  Stroke volume – the volume of blood ejected by the ventricle with each contraction

Cardiac Output  Stroke Volume = End Diastolic Volume (130ml) – End Systolic Volume (60ml)

Cardiac Output  Heart Rate – number of beats per minute

Regulation of Heart Rate  Sympathetics impulses increase heart rate and force of contraction

Regulation of Heart Rate  Parasympathetic impulses decrease heart rate

Tachycardia  Heart Rate over 100 beats/min

Bradycardia  Heart Rate below 60 beats/min

Fibrillation  Prolonged tachycardia

Exercise And The Heart  Sustained exercise increases oxygen demand in muscles

Exercise And The Heart  Resting cardiac output 5.25 Liters/minute

Exercise And The Heart  In sedentary people CO may go up to 22 liters/minute

Exercise And The Heart  In trained athletes CO may go up to 40 liters/minute

Exercise And The Heart  Sedentary people increase their CO during exercise by an increase in HR and SV

Exercise And The Heart  Sedentary people   Increase in HR more dramatic Stroke volume only goes up by 10-35%

Exercise And The Heart  For a given activity, sedentary people’s maximum HR will be higher than in a trained athlete

Exercise And The Heart  Trained athletes increase their CO during exercise by an increase in HR and SV

Exercise And The Heart  Trained Athletes   Increase in SV more dramatic than HR Their SV goes up to 60%

Exercise And The Heart  Athletes have larger stroke volumes due to longer filling time

Electrocardiogram (ECG or EKG)  Records the electrical currents of the body generated by the heart

Electrocardiogram (ECG or EKG)  P= depolarization of the atria

Electrocardiogram (ECG or EKG)  QRS= depolarization of the ventricles (repolarization of atria, but don’t see)

Electrocardiogram (ECG or EKG)  T= ventricles repolarization

Electrocardiogram (ECG or EKG)  PR interval= between beginning of atrial depolarization and ventrical depolarization

Electrocardiogram (ECG or EKG)  ST segment= ventricle contraction

Electrocardiogram (ECG or EKG)  QT interval = ventricle depolarization through ventricle repolarization