❤️ Flashcards
Organization of cardiovascular system
The Pulmonary Circuit
■ Carries blood to and from gas exchange surfaces of the lungs
The Systemic Circuit
■ Carries blood to and from the body
Capillaries
“exchange vessels”
■ Exchange materials between blood and tissues
■ Dissolved gases, nutrients, wastes
4 chambers of the ❤️
■ 2 for each circuit:
■ left and right:
■ ventricles and atria
1) Right atrium:
■ collects blood from systemic circuit
2) Right ventricle:
■ pumps blood to pulmonary circuit
3) Left atrium:
■ collects blood from pulmonary circuit
4) Left ventricle:
■ pumps blood to systemic circuit
Anatomy of the ❤️
■ Located directly behind sternum
■ Great veins and arteries at the base
■ Base leans toward right shoulder
■ Pointed tip is apex
■ Apex points toward left hip
Relation to thoracic cavity
Surrounded by pericardium
■ Between 2 pleural cavities
■ In the mediastinum
Pericardium
2x lining of pericardial cavity
2 layers of pericardium
- Parietal pericardium:
• outer layer
• forms inner layer of pericardial sac (Fibrous pericardium) - Visceral pericardium:
• inner layer of pericardium
Structures of pericardium
■ Pericardial cavity:
■ Is between parietal and visceral layers (Serous pericardium)
■ contains pericardial fluid
■ Pericardial sac (Fibrous pericardium):
■ fibrous tissue
■ Protects, anchors, and prevents overfilling
Cardiac tamponade
■ Fluid from pericarditis related inflammation can build up in the pericardial cavity
■ Can restrict heart movement
3 layers of ❤️ wall
■ Epicardium: outer layer
■ Myocardium: middle layer
■ Endocardium: inner layer
Epicardium
■ Same as the visceral pericardium
■ Covers the heart
Myocardium
■ Muscular wall of the heart
■ Concentric layers of cardiac muscle tissue
■ Atrial myocardium wraps around great vessels
■ 2 divisions of ventricular myocardium
2 divisions of ventricular myocardium
■ Superficial ventricular muscles: surround both ventricles
■ Deep ventricular muscles:
■ surrounds only the left ventricle
■ Makes up the intraventricular septum
3 types of 🩸vessels
■ Arteries: carry blood away from ❤️
■ Veins: carry blood to heart (oxygenation?)
■ Capillaries: networks between arteries and veins
Atrioventricular (AV) Valves
■ Connect right atrium to right ventricle and left atrium to left ventricle
■ Permit blood flow in 1 direction:
■ atria to ventricles
Vena cava
■ Delivers systemic circulation to right atrium
■ Superior vena cava:
■ receives blood from head, neck, upper limbs, and chest
■ Inferior vena cava:
■ receives blood from trunk, and viscera, lower extremities
Coronary sinus
■ Cardiac veins return blood to coronary sinus
■ Coronary sinus opens into right atrium
Pectinate muscles
■ Contain prominent muscular ridges
■ On anterior atrial wall
■ And inner surfaces of right auricle
Right atrioventricular (AV) Valve
■ Also called tricuspid valve
■ Opening from right atrium to right ventricle
■ Has 3 cusps
■ Prevents backflow
Trabeculae carneae
■ Muscular ridges on internal surface of the ❤️s ventricles
■ Includes moderator band (right side only):
■ ridge contains part of conducting system
■ coordinates contractions of cardiac muscle cells
■ May help prevent the heart overstretching
Pulmonary circuit
■ Conus arteriosus (superior right ventricle) leads to pulmonary trunk
■ Pulmonary trunk divides into left and right pulmonary arteries
■ Blood flows from right ventricle to pulmonary trunk through pulmonary valve
■ Pulmonary valve has 3 semilunar cusps
Left ventricle
■ Holds same volume as right ventricle
■ Is larger; muscle is thicker, and more powerful
■ Similar internally to right ventricle, but does not have moderator band
Left ventricle system circulation
■ blood leaves left ventricle through aortic valve into ascending aorta
■ ascending aorta turns (aortic arch) and becomes descending aorta
Left and right ventricle
■ Have significant structural differences
Structure of Left and Right Ventricles
■ Right ventricle wall is thinner, develops less pressure than left ventricle
■ Right ventricle is pouch-shaped, left ventricle is cone-shaped
❤️ valves
■ One-way valves prevent backflow during contraction
Regurgitation
■ Failure of valves
■ Causes backflow of blood into atria
Semilunar valves
■ Pulmonary and aortic tricuspid valves
■ Prevent backflow from pulmonary trunk and aorta into ventricles
■ Have no muscular support
Aortic sinuses
■ At base of ascending aorta
■ Prevent valve cusps from sticking to aorta
■ Origin of right and left coronary arteries
■ Blood can only flow in to coronary arteries in diastole
Carditis
■ An inflammation of the ❤️
■ Can result in valvular heart disease (VHD):
■ From the build up of scar tissue
■ e.g., rheumatic fever
Fibrous skeleton
■ 4 bands around heart valves and bases of pulmonary trunk and aorta
■ Stabilize valves
■ Electrically insulate ventricular cells from atrial cells
Coronary circulation
-Coronary arteries and cardiac veins
-Supplies 🩸 to muscle tissue of heart
Coronary arteries
■ Left and right
■ Originate at aortic sinuses
■ High blood pressure, elastic rebound force blood through coronary arteries between contractions
Right coronary artery
■ Supplies blood to:
■ right side of ❤️
■ portions of both ventricles
■ cells of sinoatrial (SA) and atrioventricular nodes
■ marginal arteries (surface of right ventricle)
■ posterior interventricular artery
Left coronary artery
■ Supplies blood to:
■ left ventricle
■ left atrium
■ interventricular septum
■ 2 main branches:
■ circumflex artery
■ anterior interventricular artery
Arterial anastomoses
■ Interconnect anterior and posterior interventricular arteries
■ Stabilize blood supply to the ❤️
Great cardiac vein
■ drains blood from area of anterior interventricular artery into coronary sinus
Anterior cardiac vein
■ empties into right atrium
Posterior cardiac vein, middle cardiac vein, and small cardiac vein:
■ empty into great cardiac vein or coronary sinus
Cardiac muscle cells
■ Intercalated discs:
■ interconnect cardiac muscle cells
■ secured by desmosomes
■ linked by gap junctions
■ convey force of contraction
■ propagate action potentials
Characteristics of cardiac muscle cells
- Small size
- Single, central nucleus
- Branching inter-connections between cells
- Intercalated discs
Structure of cardiac tissue
■ Cardiac muscle is somewhat striated with light and dark cross bandings
■ The striped or striated pattern is due to:
■ alternating dark, (A bands) and light, (I bands)
Characteristics of cardiocytes
■ Unlike skeletal muscle, cardiac muscle cells (cardiocytes):
■ have an extensive system of short, wide T tubules which are filled with extracellular rich fluid
■ Rely on extracellular Ca2+ for contraction
■ Individual muscle cells:
■ have no triads
■ have SR with no terminal cisternae
■ are aerobic (high in myoglobin, mitochondria)
■ have limited capacity for regeneration
■ terminate in thickened structures known as intercalated discs
Intercalated discs
Are specialized contact points between cardiocytes
Functions of intercalated discs
■ Join cell membranes of (cardiac muscle cell) cardiocytes using gap junctions and desmosomes
■ Maintain structure
■ Enhance molecular and electrical connections
■ Conduct action potentials
Energy source of cardiocytes
■ At rest fatty acids (60%), glucose (35%) and small amounts of lactic acid can be burned AEROBICALLY (as long as sufficient oxygen is available to the muscle) to meet long term ATP needs.
■ ATPs can be used to sustain power stroking
■ Cardiiocites also use creatine kinase to produce ATP
■ During exercize cardiocytes use more lactic acid which is produced by active skeletal muscles
■ It is converted to pyruvic acid by the enzyme Lactate dehydrogenase (LDH)
Coordination of cardiocytes
■ Cardiac muscle cells form Functional Syncytia which means a multi-nucleated mass of cells. These cells are:
■ Mechanically
■ Chemically
■ Electronically Connected
■ Because the myofibrils from adjoining cells are essentially locked together, they all pull together for max. efficiency
■ are arranged into 2 Syncytia
■ an atrial syncytium and
■ a ventricular syncytium
■ separated by a band of connective tissue
❤️beat
■ A single contraction of the heart
■ The entire heart contracts
■ first the atria
■ then the ventricles
2 types of cardiac muscle cells
■ Conducting system:
■ controls and coordinates heartbeat
■ Contractile cells:
■ produce contractions
Conducting system
■ The cardiac cycle begins with action potential at sinus (sinusatrial node(SA))node
■ transmitted through conducting system
■ produces action potentials in cardiac muscle cells (contractile cells)
■ A system of specialized cardiac muscle cells:
■ initiates and distributes electrical impulses that stimulate contraction
■ Automaticity or autorythicity:
■ cardiac muscle tissue contracts automatically (no cns stimuli needed)
Structures of conducting system
■ Sinoatrial (SA) node
■ Atrioventricular (AV) node
■ Conducting cells
Conducting cells
■ Interconnect SA and AV nodes
■ Distribute stimulus through gap junctions in intercalated discs in cardiac muscle
■ In the atrium:
■ internodal pathways
■ In the ventricles:
■ AV bundle and bundle branches
Pacemaker (autohythmic) cells
■ Pacemaker potential (#1)
■ Have unstable resting membrane potentials due to opening of slow Na+ channels
■ Continuously depolarize
■ Never flat line
■ Depolarization (#2)
■ At threshold, Ca2+ channels open
■ Explosive Ca2+ influx produces the rising phase of the action potential
■ Repolarization
■ results from inactivation of Ca2+ channels and opening of voltage-gated K+ channels
