Post on 28-Dec-2015
transcript
Heart Anatomy
Size, Location, and Orientation Enclosed in the mediastinum Base (posteriorsuperior
portion) and Apex (inferioranterior portion)
Heart Anatomy Coverings
Pericardium protects the heart anchors the heart to
surrounding structures such as the diaphragm and the great vessels
prevents overfilling of the heart with blood
Heart AnatomyCoverings
pericardial cavity contains a film of serous fluid
pericarditis: inflammation of the pericardium which may lead to adhesions between the layers or the buildup of fluid in the pericardial cavity (cardiac tamponade)
Heart Anatomy Heart Wall
Epicardium Myocardium
bulk of the heart consisting mainly of cardiac muscle
Heart Anatomy Heart Wall
Endocardium simple squamous
epithelium and a thin CT layer that lines the heart chambers and valves and is continuous with the endothelial lining of the blood vessels
Heart Anatomy Chambers
Atria Features
small, thin-walled chambers Functions
receiving chambers for blood returning to the heart from the circulation
push the blood into the adjacent ventricles.
Heart Anatomy Chambers
Atria Receive blood from
right side Superior and Inferior Vena
Cava Coronary Sinus (draining the
myocardium) left side Pulmonary Veins
Heart Anatomy Chambers
Ventricles Features
make up most of the mass of the heart
the walls of the left ventricle are 3X thicker than those of the right
Heart Anatomy Chambers
Ventricles Functions
discharging chambers of the heart propel blood to Pulmonary Trunk (right
ventricle), Aorta (left ventricle)
Heart Anatomy Pathway of Blood Through the
Heart Pulmonary Circuit
functions strictly as gas exchange
the right side of the heart is the pulmonary circuit pump
this is a short, low-pressure circuit
Heart Anatomy Pathway of Blood Through the
HeartSystemic Circuit
o functions as both gas and nutrient exchange
o the left side of the heart is the systemic circuit pump
o this is a long, high-resistance pathway through the entire body
Heart Anatomy Heart Valves
These enforce the one-way flow of blood through the heart
The valves open and close in response to differences in blood pressure on their two sides
Heart Anatomy Heart Valves
Atrioventricular Valves the valves close when the
ventricular pressure increases and forces blood against the valve flaps
Tricuspid (right side) Bicuspid (Mitral) (left side)
Heart Anatomy Heart Valves
Semilunar Valves located between the ventricles
and the large arteries these open when the pressure
produced by the contracting ventricle exceeds that in the artery and close when the arterial pressure exceeds the pressure produced by the relaxing ventricle
Pulmonary (right side) Aortic (left side)
Coronary Circulation Coronary Arteries
the coronary arteries arise from the base of the aorta and actively deliver blood only when the heart is relaxed
the heart is 0.5% of body weight and receives 5% of the body's blood supply (most to the left ventricle)
Coronary Circulation Coronary Arteries
left main coronary artery left anterior descending artery:
serves the interventricular septum and anterior walls of both ventricles
circumflex artery: serves the left atrium and posterior wall of the left ventricle
Coronary Circulation Coronary Arteries
Right main coronary artery posterior descending artery: serves
the posterior walls of both ventricles
marginal artery: lateral wall of the right side of the heart
Cardiac Veins follow arteries and join at the Coronary Sinus which empties blood into the right atrium
Heart Physiology Electrical Events
Intrinsic Conduction System of the Heart the ability of cardiac muscle to
depolarize and contract is intrinsic (no nervous stimulation is required)
nerve impulses can alter the basic rhythm of heart activity set by intrinsic factors
Heart Physiology Electrical Events
Action Potential Generated by Autorhythmic Cells Sequence of Excitation
o Sinoatrial Node o Atrioventricular Node o Atrioventricular Bundle
(bundle of His) o Bundle Branches o Purkinje Fibers
Heart Physiology Electrical Events
Extrinsic Innervation of the Heart fibers of autonomic nervous
system accelerate or inhibit the basic rate of heartbeat set by the intrinsic conduction system
Heart Physiology Electrical Events
Electrocardiography electrical currents generated
and transmitted through the heart spread throughout the body and can be monitored
the graphic recording of electrical changes during heart activity is called an electrocardiogram (ECG or EKG)
Heart Physiology
Electrical Events Electrocardiography
the ECG consists of series of three waves o P Wave: atrial depolarization
starting at the SA node o QRS Complex: ventricular
depolarization
Heart Physiology Electrical Events
Electrocardiographyo P-R (P-Q) interval: time from
the beginning of atrial excitation to the beginning of ventricular excitation and includes the contraction of the atria and the passage of the depolarization wave through the rest of the conduction system
Heart Physiology Electrical Events
ElectrocardiographyoT Wave: ventricular repolarization oQ-T interval: time from the
beginning of the ventricular depolarization through their repolarization and includes the contraction of the ventricles
Heart Physiology Mechanical Events: The Cardiac Cycle
Terms Systole: contraction period of
heart activity Diastole: relaxation period of
heart activity
Heart Physiology Mechanical Events: The Cardiac Cycle
Cardiac Cycle o pressure in the heart is low and the
blood is returning passively (70% of ventricle filling occurs)
o atria depolarize (P wave) and contract and force the remaining 30% of the blood into the ventricles
o the atria relax and remain in diastole through the rest of the cycle
Heart Physiology Mechanical Events: The Cardiac Cycle
o the ventricles depolarize (QRS complex)
o ventricles begin their contraction o ventricular pressure rises rapidly
and the AV valves close o as ventricular pressure rises above
arterial pressure the semilunar valves open and the ventricles empty during the ventricular ejection phase
Heart Physiology Mechanical Events: The Cardiac Cycle
o ventricular systole ends with the repolarization of the ventricles (T wave)
o ventricles relax and ventricular pressure drops
o semilunar valves close o the atria have been filling with blood
since ventricular systole and when the atrial pressure exceeds the ventricular pressure the AV valves open ventricular filling begins again
Heart Physiology Cardiac Output
General cardiac output is the amount of
blood pumped out by each ventricle in 1 minute and is the product of heart rate (HR) and stroke volume (SV)
stroke volume is the volume of blood pumped out by one ventricle with each beat and is the difference between end diastolic volume (EDV) and the end systolic volume (ESV)
Heart Physiology Cardiac Output
Regulation of Stroke Volume Preload: Degree of Stretch
affected by the EDV and operates intrinsically
Frank Starling Law of the Heart: The greater the degree of stretch of cardiac muscle fibers the greater the force of contraction and the greater the stoke volume
Heart Physiology Cardiac Output
resting cardiac fibers are normally shorter than the optimal length and stretching them (increasing EDV) produces dramatic increases in contractile force
anything that increases the volume or speed of venous return (slow heart rate or exercise) increases EDV which increases the force of contraction which increases stroke volume
Heart Physiology Cardiac Output
Contractility affects the ESV and are
extrinsic factors that increase the contractile strength of heart muscle
many chemicals enhance contractility (positive inotropic agents)
Heart Physiology Cardiac Output
Afterload: Back Pressure affects the ESV the pressure exerted on the
aortic (80 mm Hg) and pulmonary (20 mm Hg) valves by arterial blood
important in people with hypertension where ESV is increased and stroke volume is reduced