Heart Flashcards
Where is the heart?
Rests in mediastinum, on diaphragm near centre of thoracic cavity
How much of the heart is left of the midline?
2/3 of the weight
Apex of heart
Pointed end formed by tip of left ventricle rests on diaphragm
Base of heart
Posterior aspect formed by atria
How many heart beats per day?
100,000– 35 mil per year
How many litres of blood are pumped per minute?`
5L
Pericardium
Membrane that surrounds and protects heart
2 layers of the pericardium
Fibrous pericardium
Serous Pericardium
Fibrous Pericardium
Superficial layer, dense irregular connective tissue provides protection and anchors heart to mediastinum
Serous Pericardium
Thinner layer forms double layer around heart
2 layers of serous pericardium
Parietal layer on outside
Visceral layer adhered to heart
Pericardial Cavity
Space between parietal and visceral layer that is filled with pericardial fluid
How many layers of the heart wall?
3
Epicardium
Outer layer of the heart composed of 2 tissue layers
2 Tissue layers of the epicardium
Outer layer is the visceral layer of pericardium
Inner layer is delicate fibroelastic and elastic tissue
Myocardium
Middle layer of heart made of cardiac muscle. Responsible for pumping
What is the largest layer of the heart?
Myocardium
Endocardium
Inner layer made of endothelium overlying a thin layer of connective tissue
What connected cardiac muscle fibers?
Intercalated discs containing desmosomes and gap junctions
Cardiac Muscle
Shorter, less round and with more large mitochondria than skeletal muscle
Atria
Two upper chambers recieve blood from veins
Ventricles
Two lower chambers eject blood through arteries
Pulmonary Pump
Weaker pump consisting of right atrium and right ventricle moves deoxygenated blood through lungs
Systemic Pump
Stronger pump made of left atrium and left ventricle. Circulates oxygenated blood
Auricle
Wrinkled pouch on anterior side of atrium increases capacity to hold more blood
Sulci
Grooves on surface containing coronary blood vessels and fat mark external boundary between two chambers
Coronary Sulcus
Encircles most of heart and marks boundary atria and ventricles
Anterior/ Posterior Interventricular Sulcus
Shallow groove is boundary between left and right ventricles
3 veins that right atrium recieves from?
Superior vena cava
Inferior vena cava
Coronary Sinus
Pectinate muscles
Form parallel ridges on anterior side of right atrium
Interatrial Septum
Thin partition between right and left atria
Fossa Ovalis
Opening on interatrial septum that directs blood to left atrium to bypass fetal lungs
Tricuspid Valve
Passes blood from right artium to left atrium
Trabeculae Carnae
Ridges formed by bundles of cardiac muscle fibers
Chordae Tendineae
Cords connected to cusps of tricuspid valve
Papillary Muscles
Cone shaped trabeculae carnae connected to chordae tendineae
Interventricular Septum
Partition between right and left ventricles
Pulmonary Valve
Blood passes from right ventricle into pulmonary trunk
Pulmonary Trunk
Large vessel divides into right and left pulmonary arteries which carry blood to lungs
How many veins does the left atrium receive from?
4 pulmonary veins
Bicuspid Valve
Blood passes from left atrium into left ventricle
What is the thickest heart chamber?
Left ventricle
Aortic Valve
Blood passes from left ventricle into ascending aorta
Fibrous skeleton
Four dense connective tissue rings surrounding chambers
What are the four rings of the fibrous skeleton?
Pulmonary
Aortic
Right atrioventricular
Left atrioventricular
Valves
Contract and push blood into a ventricle or out of the heart into an artery
Atrioventricular Valves
Between atrium and ventricles. Open and cusps project into ventricle
When does blood move in an AV valve?
When the pressure in the atrium is higher than in the ventricle
Semilunar Valves
Aortic and pulmonary valves made of 3 half moon cusps
Function of SL valve
Eject blood into arteries and prevent backflow into ventricles
When does blood move in an SL valve?
When the pressure is higher in the ventricle than in the artery
What happens when ventricles contract?
Pressure builds in chambers and valves open
Systemic Circulation
Oxygenated blood flows from left ventricle trough aorta to all organs and return through right atrium
Order of vessels in systemic circulation
Aorta
Systemic arteries
Arterioles
Systemic capillaries
Venules
Carry deoxygenated blood away from tissues
Pulmonary Circulation
Deoxygenated blood flows from right ventricle, to the lungs, and returns to left atrium
Order of vessels in pulmonary circulation
Right ventricle
Pulmonary trunk
Pulmonary artery
Pulmonary capillaries
Coronary Circulation
Hearts blood supply through vessels that pierce myocardium
Coronary Arteries
Branch from ascending aorta and supply heart with oxygenated blood when heart is relaxed
Left coronary artery
Inferior to left auricle. Divides into interventricular and circumflex branches
Anterior Interventricular Branch
Branch of left coronary artery in anterior interventricular sulcus supplies both ventricles
Circumflex branch
Branch of left coronary artery in coronary sulcus that supplies left ventricle and left atrium
Right Coronary artery
Supplies small branches to right atrium. Inferior to right auricle and divides into posterior interventricular and marginal branches
Posterior Interventricular Branch
Follows posterior interventricular sulcus and supplies both ventricles
Marginal Branch
Along margin of the heart and supplies right ventricle
Anastomoses
Artery connection provide collateral circulation if passage become blocked
Coronary Veins
Deoxygenated blood drains into vascular sinus
Coronary sinus
Empties into right atrium
Great cardiac vein
In anterior interventricular sulcus which drains ventricles and left atrium
Middle cardiac vein
In posterior interventricular sulcus and drains ventricles
Small cardiac vein
In coronary sulcus and drains right atrium and right ventricle
Anterior cardiac veins
Drains right ventricle and opens directly into right atrium
Autorhythmic Cells
Repeatedly and rhythmically generate action potentials even when outside body
Cardiac Conduction system
Delivers action potentials and stimulates chambers to contract in coordination
Sequence of Cardiac conduction system
Sinoarterial node Atrioventricular node Atrioventricular bundle Right/ left bundle branches Purkinje Fibers
Sinoarterial Node
Makes two atria contract at the same time
Atrioventricular Node
Action potential slows and delay alows atria to empty blood into vesicles
Where is the only site that action potentials can conduct from atria to ventricles?
Bundle of His
Electrocardiogram
Composite of action potentials produced by nodal and contractile cells
Cardiac Cycle
Events of one heart beat
Which chambers contract first?
Atria
Systole
Contraction phase of a heart chamber
Diastole
Phase of relaxation
Sequence of Cardiac Cycle
Relaxation period
Atrial Systole
Ventricular Systole
Relaxation Period
all chambers are in diastole. Ventricle pressure drops and blood rushes back towards ventricles.
What valves are open during Atrial Systole?
AV valves
Membrane Potential
Membrane of excitable cells have a difference in electrical potential on either side
Polarized
Negative ions build up cytosol and positive ions build up in extracellular fluid
Depolarization
Reduction in membrane potential when inside becomes less negative than resting membrane potential
Action potential
Decrease and reverse resting potential and restore it to resting state
Sequence of waves in heart beat
P
QRS
T
P wave
Spread of depolarization from SA node to atria followed by atrial contraction
QRS wave
Spread of depolarization through ventricles followed by contraction
T wave
Indicated ventricle repolarization
