ANATOMY AND PHYSIOLOGY Flashcards
What are the 5 surfaces of the heart?
Base
Diaphragmatic (inferior)
Sternocostal (anterior)
Left pulmonary surface
Right pulmonary surface
What are the 4 heart chambers and what are their functions?
Right atrium and ventricle - recieve deoxygenated blood from systemic veins and pumps it to the lungs
Left atrium and ventricle - recieve oxygenated blood from the lungs and pumps it to the systemic vessels
What separates the left and right sides of the heart?
Interatrial and interventricular septa
What separates the atria and ventricles?
Atrioventricular septa
What prevents backward prolapse of the cusps of the valves?
Chordae tendinae (fibrous cords that connect the papillary muscles of the ventricular wall to the atrioventricular valves)
What are the 2 sets of valves?
Atrioventricular (prevent back flow from ventricles to atria) and semilunar (prevent back flow from the great vessels into ventricles)
What are the 2 atrioventricular valves and describe their structure?
Right atrioventricular valve - tricuspid valve - has 3 cusps which are anterior, septal and posterior
Left atrioventricular valve - bicuspid valve - has 2 cusps which are anterior and posterior
LAB RAT
What are the 2 semilunar valves and describe their structure?
The pulmonary semilunar valve - between right ventricle and opening of pulmonary trunk - has 2 semilunar cusps (anterior, left and right)
The aortic semilunar valve - between left ventricle and opening of aorta - has 3 semilunar cusps (left, right and posterior)
Outline the blood flow through the heart?
The right atrium receives deoxygenated blood from the superior and inferior venae cavae and coronary sinus
The right atrium contracts pushing blood through the right atrioventricular valve into the right ventricle. The right ventricle then contracts passing the blood into the pulmonary trunk via the pulmonary valve to reach the lungs
In the lungs, the blood gets oxygenated then moves back into the heart entering the left atrium through the pulmonary veins.
The left atrium contracts and pushes the blood into the left ventricle through the left atrioventricular valve.
The left ventricle pushes oxygenated blood through the aortic semilunar valve into the aorta, from which blood is distributed throughout the body.
What supplies the heart with oxygenated blood?
The left and right coronary arteries
Where do the coronary arteries arise from?
Aortic sinuses at the beginning of the ascending aorta
What collects venous blood from the heart?
The middle, posterior and small cardiac veins
What are the great vessels of the heart?
Aorta
Pulmonary artery
Pulmonary vein
Superior vena cava
Inferior vena cava
What are the major branches of the aorta?
Brachiocephalic trunk
Left common carotid artery
Left subclavian artery
Whats the weight of a normal heart in males and females?
Males - 310g
Females - 255g
What are the 3 layers of the heart wall?
Epicardium - outer layer formed by the visceral layer of the serous pericardium
Myocardium - contains the excitable tissue and conducting system
Endocardium
Which coronary artery carries 80% of the flow to the heart muscles?
Left main coronary artery
What are the branches of the left coronary artery and what do they supply?
Left anterior descending - its diagonal branches supply the interventricular septum and both ventricles
Circumflex coronary artery - typically gives rise to the left marginal artery and other small arteries. Supplies blood to the lateral and posterior portions of the left ventricle and left atrium
What are the branches of the right coronary artery?
Anterior branches - Conal artery, sinus node branch, anterior atrial branch, anterior ventricular branch
Marginal branches - right acute marginal branch
Inferior branches - atrioventricular nodal branch, posterior descending artery, posterolateral branch
What does the right marginal atrery supply?
Lateral portion of right ventricle and apex
What does the posterior descending artery supply?
Inferior aspect of the heart
What does the right coronary aretry supply?
Right atrium and ventricle
Where do most coronary veins coalesce?
Coronary sinus (runs in the left posterior atrioventricular groove and opens into the right atrium)
What are thebesian veins?
Smallest cardiac veins
The small valveless veins in the walls of the 4 heart chambers that are responsible for venous return of 10% of coronary blood supply
Where is the heart found?
In the middle mediastinum
Where are the pulmonary arteries found?
Receive deoxygenated blood from the right ventricle and deliver it to th lungs
They begin as the pulmonary trunk which is separated from the right ventricle by the pulmonary valve
At level T5-T6 the pulmonary trunk splits into the right and left pulmonary arteries. Each of these then split into 2 and supply blood to the right and left lung respectively
Right pulmonary artery is thicker and longer than left
Where are pulmonary veins found and what are their function?
They receive oxygenated blood from the lungs and deliver it to th left side of the heart to be pumped around the body
There are 4 with one superior and one inferior for each lung
They enter the pericardium to drain into the superior left atrium on the posterior surface
Superior pulmonary veins return blood from upper lobes of lung and inferior veins from lower lobes
What is the oblique sinus?
an inverted J-shaped reflection of the venae cavae and pulmonary veins
It lies behind the atria and in between left and right pulmonary veins.
What is the transverse sinus?
the tunnel-shaped passage posterior to the aorta and pulmonary trunk and anterior to the superior vena cava
What is the superior sinus?
anterior to the ascending aorta and the pulmonary trunk
What are the 3 pericardial sinuses?
Impressions in the pericardial sac
?Superior, oblique and transverse
Where does the apex of the heart point to?
Anterior-inferior direction
What are the sulci of the heart?
The grooves on the surface of the heart formed by the chambers of the heart
Coronary sulcus (runs transversely around the heart and represents the wall dividing the atria from the ventricles)
Anterior and posterior interventricular sulci (runs vertically on their respective sides of the heart and represent the interventricular septum)
Where does the right atrium recieve its deoxygenated blood fron?
Superior and inferior vena cava and coronary veins
What are the 2 parts of the interior surface of the right atrium?
Sinus venarum
Atrium proper
What separates the sinus venarum and atrium proper?
Crista terminalis (muscular ridge)
Where is the sinus venarum? Where does it receive blood from? Where is it embryologically derived from?
located posterior to the crista terminalis. This part receives blood from the superior and inferior vena cavae. It has smooth walls and is derived from the embryonic sinus venosus.
Where is the atrium proper? Where does it receive blood from? Where is it embryologically derived from?
located anterior to the crista terminalis, and includes the right auricle. It is derived from the primitive atrium, and has rough, muscular walls formed by pectinate muscles.
What is the fossa ovalis?
The small oval-shaped depression in the septal wall in the right atrium that is the remnant of the foreamen oval in the foetal heart
Where does the left atrium recieve blood from?
The 4 pulmonary veins
What is the left auricle?
Aka the left atrial appendage
A flag of heart wall on the anterior surface of the left atrium of the heart. It’s a small, conical-shaped chamber that collects blood from the veins and directs it to the ventricles
It increases the capacity of the atrium
What can the interior surface of the left atrium be divided into?
Inflow portion
Outflow portion
Where does the inflow portion of the left atrium receive blood from? What is its embryological origin?
Receives blood from pulmonary veins
Internal surface is smooth
Derived from pulmonary veins themselves
Where does the outflow portion of the left atrium receive blood from? What is its embryological origin?
Located anterior and included left auricle
Lined by pectiate muscles
Derived from embryonic atrium
What are the 2 separate portions of the right ventricle?
Inflow portion
Outflow portion aka conus arteriosus
What separates the inflow and outflow portion of the right ventricle?
Supraventricular crest
What is found in the inflow portion of the right ventricle?
Trabeculae carnae (irregular muscular elevateions)
What are the 3 types of trabeculae carnae?
Ridges - attached along their entire length from one side to form ridges
Bridges - attached to the ventricle at both ends but free in the middle
Pillars - aka papillary muscles - anchored by their base to ventricles but their apices are attached to chordae tendinae which are attached to 3 tricuspid valve cusps -
Whats the function of papillary muscles?
the papillary muscles ‘pull’ on the chordae tendineae to prevent prolapse of the valve leaflets during ventricular systole.
What is found in the conus arteriosus (outflow portion of right ventricle)? Where is it derived from embryologically?
Located in superior aspect of ventricle
Derived embryologically from bulbus cordis
Smooth walls and no trabeculae carnae
What are the 2 parts of the left ventricle?
Inflow and outflow portion
Whats the inflow portion like in the left ventricle?
The walls of the inflow portion of the left ventricle are lined by trabeculae carneae, as described with the right ventricle. There are two papillary muscles present which attach to the cusps of the mitral valve.
What is the outflow portion of the left ventricle known as? Whats it like? Whats it derived from?
Aortic vestibule
Smooth-walled with no trabeculae carnae
Derived from the embryonic bulbus cordis
What are aortic sinuses?
small openings found within the aorta behind the left and right flaps of the aortic valve. When the heart is relaxed, the back-flow of blood fills these valve pockets, therefore allowing blood to enter the coronary arteries.
Off which coronary artery does the posterior interventricular artery arise from?
80-85% of people - right coronary artery
20-25% of people - left coronary arter
What is the coronary sinus?
The coronary sinus is a large venous structure located on the posterior aspect of the left atrium, coursing within the left atrioventricular groove. The function of the coronary sinus is to drain the venous blood from the majority of the heart.
What are the main tributaries of the coronary sinus?
Great cardiac vein - largest tributary
Small cardiac vein
Middle cardiac vein
Posterior cardiac vein
Where does the great cardiac vein originate and go to?
It originates at the apex of the heart and ascends in the anterior interventricular groove. It then curves to the left and continues onto the posterior surface of the heart. Here, it gradually enlarges to form the coronary sinus.
Where does the small cardiac vein originate and go to?
located on the anterior surface of the heart, in a groove between the right atrium and right ventricle. It travels within this groove onto the posterior surface of the heart, where it empties into the coronary sinus.
Where does the middle cardiac vein originate and go to?
Aka posterior interventricular vein
begins at the apex of the heart and ascends in the posterior interventricular groove to empty into the coronary sinus.
Where does the posterior cardiac vein originate and go to?
located on the posterior surface of the left ventricle. It lies to the left of the middle cardiac vein and empties into the coronary sinus.
What is the pericardium?
a fibro-serous, fluid-filled sack that surrounds the muscular body of the heart and the roots of the great vessels
What are the 2 layers of the pericardium?
Fibrous pericardium - tough, external layer. It’s rigid structure prevents rapid overfilling of the heart
Serous pericardium - thin, internal layer that consists of the outer parietal and internal visceral layer with the pericardial cavity containing a small amount of lubricating serious fluid i between
Whats the function of the serous fluid found in the pericardial cavity?
to minimize the friction generated by the heart as it contracts.
What are the functions of the pericardium?
Fixes the heart in the mediastinum to limit its motion as its attached to the diaphragm, sternum and tunica adventitia of the great vessels
Prevents overfilling of the heart
Lubrication to reduce friction generated by the heart as it moves
Protection from infection e.g. from lungs
What innervates the pericardium?
Phrenic nerve
What is endocardium comprised of?
Loose connective tissue and simple squamous epithelial tissue
What does the subendocardial layer consist of?
A layer of loose fibrous tissue, containing the vessels and nerves of the conducting system of the heart. The purkinje fibres are located in this layer.
What does the myocardium consist of?
cardiac muscle and is an involuntary striated muscle.
What is the subepicardial layer?
The layer between the myocardium and epicardium
What does the epicardium consist of?
Connective tissue and fat
Lined on outer surface by simple squamous epithelial cells
Outline the sequence of electrical events during one full contraction of the heart muscle?
Action potential is created by SAN
Wave of excitation spreads across the atria causing them to contract
The signal is delayed once it reaches the AVN
Signal is conducted into the Bundle of His, down the interventricular septum
The Bundle of His and the purkinje fibres spread the wave impulses along the ventricles, causing them to contract
What is the SAN?
A collection of pacemaker cells in the upper wall of the right atrium, at the junction where the superior vena cava enters
They spontaneously generate electrical impulses. The wave of excitation created by the SA node spreads via gap junctions across both atria, resulting in atrial contraction (atrial systole) – with blood moving from the atria into the ventricles.
What determines the rate at which the SAN generates impulses?
The rate at which the SA node generates impulses is influenced by the autonomic nervous system:
Sympathetic nervous system – increases firing rate of the SA node, and thus increases heart rate.
Parasympathetic nervous system – decreases firing rate of the SA node, and thus decreases heart rate.
Where is the atrioventricular node found?
In the atrioventricular septum, near the opening of the coronary sinus
How much does the AVN delay the electrical impulse by and why?
120ms
To ensure atria have enough time to fully eject blood into the ventricules before ventricular systole
Outline the structure of the bundle of His?
It’s a continuation of the specialised tissue of the AVN and descends down the membranous part of the interventricular septum before dividing into the right and left bundle branch
What are purkinje fibres?
Subendocarcial plexus of conduction cells - a network of specialised cells that are abundant with glycogen and have extensive gap junctions - able to rapidly transmit cardiac action potentials from atrioventricular bundle to the myocardium of the ventricles which allows for coordinated ventricular contraction
Outline the cellular basis of myocardial contraction-excitation-contraction coupling?
Myocytes contain bundles of parallel myofibrils. Each myofibril is made up of a series of sarcomeres. Each sarcomere is bound by two transverse Z lines, to each of which is attached a perpendicular filament of the protein actin. The actin filaments from each of the two Z bands overlap with thicker parallel protein filaments known as myosin. Actin and myosin filaments are attached to each other by cross-bridges that contain ATPase, which breaks down ATP to provide the energy for contraction.
Two chains of actin molecules form a helical structure with another molecule, tropomyosin, in the grooves of the actin helix; a further molecule, troponin, is attached to every seven actin molecules. During cardiac contraction, the length of the actin and myosin monofilaments does not change. Rather, the actin filaments slide between the myosin filaments when ATPase splits a high-energy bond of ATP. To supply the ATP, the myocyte has a very high mitochondrial density (35% of the cell volume). As calcium ions bind to troponin C, the activity of troponin I is inhibited, which induces a conformational change in tropomyosin. This event unlocks the active site between actin and myosin, enabling contraction to proceed.
What is starlings law of the heart?
The law states that the stroke volume of the heart increases in response to an increase in the volume of blood in the ventricles, before contraction (the end diastolic volume), when all other factors remain constant. As a larger volume of blood flows into the ventricle, the blood stretches cardiac muscle, leading to an increase in the force of contraction
Outline the cardiac cycle?
atrial systole begins
Isovolumetric contraction
Ventricular contraction (systole first phase)
Ventricular ejection (systole-second phase)
Isovolumetric relaxation
Ventricular diastole
What is Isovolumetric contraction?
causes left ventricular pressure to rise above atrial pressure, which closes the mitral valve and produces the first heart sound. The aortic valve opens at the end of isovolumetric contraction when left ventricular pressure exceeds aortic pressure. aortic and pulmonary valves closed.
What is Isovolumetric relaxation?
When the ventricular pressures drop below the diastolic aortic and pulmonary pressures, the aortic and pulmonary valves close producing the second heart sound. This marks the beginning of diastole.
What is diastolic aortic pressure?
the minimum pressure experienced in the aorta when the heart is relaxing before ejecting blood into the aorta from the left ventricle (approximately 80 mmHg
What is end diastolic volume?
The amount of blood in the ventricles at the end of diastole
What is end systolic volume?
The amount of blood in the ventricles at the end of systole (note its never 0!)
What is stroke volume?
the volume of blood pumped out of the left ventricle of the heart during each systolic cardiac contraction
Cardiac output / HR
Whats normal stroke volume?
50-100ml (average of a 70kg male is 70ml)
What is cardiac output?
The amount of blood ejected by the heart per minute
Whats a normal cardiac output?
5-6L/min at rest
How do you calculate cardiac output?
HR x stroke volume
What is an ejection fraction?
measures the amount of blood the left ventricle of the heart pumps out to your body with each heartbeat.
What is a normal left ventricle ejection fraction?
50-70%
What are the features of Cardiomyocyte?
Striated
Branched
Contain many mitochronidra
Involuntary control
Contains a single, centrally located nucleus
Cell membrane is known as the sarcolemma
Why is it important that cardiac muscle cells are separated by intercalated discs?
Because it allows the cells to contract in unison
What is Poiseuille’s law?
describes laminar flow of an incompressible liquid through a tube and determines that proportional to the fourth power of the pipe’s radius.
Resistance is inversely proportion to the radium to the power of 4 so small changes to vessel diameter have significant impact ions for its flow
What are the primary determinants of stroke volume?
Preload - stretching of cardiomyocytes at the end of diastole.
Myocardial contractility - changes to stroke volume can be brought about through changes to contractility.
Afterload - pressure or load against which the ventricles must contract.
Whats the equation for blood pressure?
Cardiac output x peripheral vascular resistance
What regulates blood pressure?
Atrial stretc
Baroreceptors
RAAS
Where are arterial baroreceptors found?
Aortic arch
Carotid sinus
What are baroreceptors?
a type of mechanoreceptor allowing for the relay of information derived from blood pressure within the autonomic nervous system.
They are nerve endings in the walls of blood vessels and heart that are stimulated by changes in arterial pressure
(Decrease. In arterial bp -> sensed by arterial baroreceptors as decreased stretch -> decreased baroreceptors nerve activity -> increased sympathetic activity -> increased HR, increased heart contraction force + arteriolar vasoconstriction -> increased arterial bp
Whats the difference in physiology between autorhythmic cells and nerve/skeletal muscle cells?
In these cells, the membrane potential slowly drifts until the threshold is reached. This is in contrast to most nerve and skeletal muscle cells, in which membrane potential remains constant unless the cell is stimulated. Through repeated cycles of drifting and firing, these cells rhythmically initiate action potentials.
Outline the action potential of autorhythmic cells?
Phase 4- ‘Funny’ sodium channels (If) open allowing a slow inward flow of Na+ ions into the cell causing depolarisation. Transient (T-type) calcium channels (IcaT) open at -50mv, bringing the membrane closer to threshold. Once the threshold is reached, long-lasting (L-type) voltage-gated calcium channels (IcaL) open.
Phase 0 - The long-lasting (L-type) calcium channels remain open continuing depolarisation.
Phase 3 - Outward potassium channels (Ik) open resulting in repolarisation
Outline the action potential of contractile cells?
Phase 4 - the membrane of contractile cells remains essentially at rest at about -90 mV until excited. Leaky potassium channels (Ik) maintain the cell at resting potential through the outward movement of potassium ions.
Phase 0 - Depolarisation occurs in an adjacent cell and the threshold potential is met. Fast voltage-gated sodium channels (INa) open and sodium ions enter the cell rapidly.
Phase 1- The first stage of repolarisation. Potassium ions leave the cell via transient K+ channels (Ikto).
Phase 2 - Plateau phase. Inward movement of calcium ions via voltage-gated L-type channels (IcaL) prolongs repolarisation.
Phase 3 - Completion of repolarisation. Outward movement of potassium ions (via Ik channels) returns the membrane to its resting potential.
