CHAPTER 12THE CARDIOVASCULAR
SYSTEM: THE HEART
PAGES 388 - 411
LOCATION & GENERAL FEATURES OF THE HEART
TWO CIRCUIT CIRCULATORY SYSTEM
DIVISIONS OF THE HEART
FOUR CHAMBERS Right Atrium
Receives blood from the systemic circuit
Left Atrium Receives blood from
the pulmonary circuit
FOUR CHAMBERS Right Ventricle
Ejects blood into the pulmonary circuit
Left Ventricle Ejects blood into the
systemic circuit
FOUR VALVES – ATRIOVENTRICULAR VALVES
Right Atrioventricular Valve (AV) Tricuspid Valve
Left Atrioventricular Valve (AV) Bicuspid Valve and
Mitral Valve
FOUR VALVES – SEMILUNAR VALVES Pulmonary valve
Guards entrance to the pulmonary trunk
Aortic Valve Guards entrance to
the aorta
FLOW OF BLOOD
MAJOR VEINS AND ARTERIES AROUND THE HEART
• Arteries carry blood AWAY from the heart
• Veins allow blood to VISIT the heart
MAJOR VEINS AND ARTERIES ON THE HEART
Coronary Circulation – Supplies blood to the muscle tissue of the heart
ARTERIES
Elastic artery: Large, resilient vessels. pulmonary trunk and aorta
Muscular artery: Medium-sized arteries. They distribute blood to skeletal muscles and internal organs. external carotid artery of the neck
Arteriole: Smallest of arteries. Lead into capillaries
VEINS
Large veins: Largest of the veins. Superior and Inferior Vena Cava
Medium-sized veins: Medium sized veins. Pulmonary veins
Venules: the smallest type of vein. Lead into cappilaries
CAPILLARIES
Exchange of molecules between blood and interstitial fluid.
FLOW OF BLOOD THROUGH HEART
TISSUES OF THE HEART
THE HEART WALL Pericardium
Outermost layer Serous membrane
Myocardium Middle layer Thick muscle layer
Endocardium Inner lining of pumping
chambers Continuous with endothelium
CARDIAC MUSCLE Depend on oxygen to obtain energy
Abundant in mitochondria In contact with several other cardiac muscles
Intercalated disks – interlocking membranes of adjacent cells Desmosomes Gap junctions
CONNECTIVE TISSUE Wrap around each cardiac muscle cell and
tie together adjacent cells.
Provide support for cardiac muscle fibers
Add strength and prevent overexpansion of the heart
Help the heart return to normal shape after contractions
CHORDAE TENDINEAE Cord-like tendons that connect the papillary
muscles to the tricuspid valve and mitral valve
Connected to Papillary Muscle. Cone shaped projections on the inner surface of
the ventricle Contraction of papillary
muscles tenses the chordae tendineae and prevents the backflow of blood into the right and left atrium.
WHY DO YOU THINK THE LEFT VENTRICLE HAS THE LARGEST AMOUNT OF MUSCLE??
ELECTRICAL ACTIVITY OF THE HEART
THE HEARTBEAT
The entire heart – atria and ventricles – contracts in a coordinated manner so that blood flows in the correct direction at the proper time.
Two Types of Cardiac Muscle Cells Involved Contractile cells – contractions that propel blood Specialized noncontractile muscle cells – control and
coordinate the activities of the contractile cells in the heart Part of the conducting system
THE CONDUCTING SYSTEM A network of specialized
cardiac muscle cells that initiates and distributes electrical impulses. Nodal Cells
Located at the sinoatrial and atrioventricular nodes
Responsible for establishing the rate of cardiac contraction.
Coupled to one another causing a coordinated contraction when an action potential is initiated.
Conducting Cells Include the Atrioventricular Bundle,
bundle branches, and purkinje fibers
Responsible for distributing the contraction
THE CONDUCTING SYSTEM CONT.
Pacemaker Cells – Depolarize rapidly, generating 70 – 80 action potentials per minute (bpm) Located in the sinoatrial node
Atriventricular (AV) Bundle – (the bundle of His) extend along the interventricular septum before dividing into left and right ventricles
Purkinje Fibers – Convey the impulses to the contractile cells of the ventricle muscles.
THE ELECTROCARDIOGRAM
A machine that records the electrical events occurring in the heart.
Each time the heart beats a wave of depolarization radiates through the atria, reaches the AV node, travels down the interventricular septum to the apex, turns, and spreads though the ventricular muscles towards the base of the heart.
THE CARDIAC CYCLE
THE CARDIAC CYCLE
The peiod between the start of one heartbeat and the start of the next is a single cardiac cycle.
Includes a period of contraction - systole The chambers contract squeezing blood into an
adjacent chamber or arterial trunk
Includes a period of relaxation – diastole When the chambers fill with blood and prepares
for the start of the next cardiac cycle.
HEART DYNAMICS Refers to movements and forces generated during
cardiac contractions. Each time the heart beats, two ventricles eject equal
amounts of blood
Stroke volume - is the amount ejected by a ventricle during a single beat Stroke volume varies beat to beat so physicians are
often more interested in cardiac output
Cardiac output - is the amount of blood pumped by each ventricle in 1 minute Provides indication of blood flow through peripheral
tissues; without adequate blood flow, homeostasis cannot be maintained
FACTORS CONTROLLING CARDIAC OUTPUT
The major factors that regulate cardiac output often affect both heart rate and stroke volume
Primary factors include: Blood volume reflexes Autonomic innervation hormones
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