Cardiovascular system Flashcards
What is the cardiovascular system?
organ system responsible for transporting oxygen, carbon dioxide and nutrients etc.
Where does gas exchange occur in the CVS?
capillaries
Components of the CVS
heart, blood vessels, blood, (lymphatic system works in conjunction with CVS)
Components of blood
erythrocytes, leucocytes, platelets, plasma
What is the lymphatic system?
Organ system that transports excess interstitial fluid as lymph before returning it to venous circulation. Key part of immune system.
Description of capillary microcirculation
The high HP at the arteriole end of the capillary forces out blood plasma to form interstitial fluid. As the volume of blood plasma has decreased in the venous end, this causes a lower HP but increases the osmotic pressure. This draws interstitial fluid back into capillaries.
What are the two loops of circulation?
pulmonary and systemic circulation
Outline of pulmonary circulation
deoxygenated blood is transported out of the RV via the pulmonary trunk which bifurcates into the left and right pulmonary arteries. Gas exchange occurs in lungs. 4 pulmonary veins (2 each side) transport oxygenated blood from lungs to the LA.
Outline of systemic circulation
Oxygenated blood is transported from the LV to the body via the aorta. Deoxygenated blood returns to the RA via the SVC and IVC.
What is the mediastinum?
anatomical region in middle of thorax bordered by pleural cavities (contain lungs)
How is the mediastinum divided?
Into the superior and inferior mediastinum. The inferior mediastinum is further divided into the anterior, middle and posterior mediastinum.
Borders of the superior mediastinum
Bordered superiorly by T1 posteriorly and the superior aspect of the manubrium anteriorly. Bordered inferiorly by the sternal angle anteriorly and T4/5 posteriorly.
What structures are found in the superior mediastinum?
Aortic arch and its branches (SCCS), trachea, oesophagus, thymus gland.
Function of thymus gland
Immune system development in childhood after which it atrophies.
Borders of inferior mediastinum
anteriorly extends from sternal angle to diaphragm, posteriorly extends from T5 to T12
Structures found in anterior mediastinum
remnants of thymus, fat
Structures found in middle mediastinum
heart
Contents found in posterior mediastinum
oesophagus and descending aorta
What is the pericardium?
Double-layered membrane that surrounds the heart
Structure of the pericardium
made of 2 layers - outer fibrous layer and inner serous layer (divided into parietal and visceral layers with pericardial cavity between)
Function of fibrous layer of pericardium
dense CT that protects the heart and anchors it to the diaphragm (and prevents over-expansion, can restrict in case of pericardial effusion)
What is pericardial effusion?
Abnormal accumulation of serous fluid in pericardial cavity/space
Structure of serous pericardium
made of a parietal layer that lines inner surface of fibrous pericardium and a visceral layer that adheres to the heart surface. Separated by pericardial space/cavity
Function of pericardial space/cavity
contains lubricating serous fluid that reduces friction during heart beats
Function of superior vena cava
transports deoxygenated blood from head, neck and upper limbs to RA
Function of inferior vena cava
transports deoxygenated blood from below the level of the heart to the RA
Function of pulmonary trunk
carries deoxygenated blood from RV towards lungs and bifurcates into left and right pulmonary arteries
Order of branches from the aortic arch (R->L)
Brachiocephalic trunk (branched into right subclavian and right common carotid artery), left common carotid artery, left subclavian artery. (SCCS)
Which arteries branch from brachiocephalic trunk
Right subclavian artery, right common carotid artery.
What is an auricle?
A muscular pouch that can increase atrial capacity and relieve high atrial pressure during times of stress.
Alternative name for auricle
atrial appendage
Where are auricles found?
Anterior surface of each atria
Which blood vessel transports oxygen rich blood from the mother to the foetus?
Umbilical vein
What happens at the placenta?
Exchange of oxygen and nutrients between foetal and maternal blood
Name of structure used to bypass liver in foetal circulation?
Ductus venosus
Where does 30% of the blood in the umbilical vein enter foetal circulation?
IVC (to RA) as the blood bypasses the liver via the ductus venosus
What is the remnant of the ductus venosus
ligamentum venosum
Where is the ligamentum venosum found?
passes superiorly from porta hepatis to IVC (near caudate lobe)
How does blood bypass the lungs in foetal circulation?
Foramen ovale allows blood to flow from RA to LA (then to LV and systemic circulation. Ductus arteriosus links pulmonary trunk to aorta (for any blood that doesn’t pass though foramen ovale)
What is the foramen ovale?
Opening between the right and left atria that allows oxygenated blood to bypass lungs and enter the systemic circulation (RA -> LA -> LV -> aorta)
What is the remnant of the foramen ovale?
fossa ovalis
What is the ductus arteriosus?
A vessel connecting the pulmonary trunk to the aorta, allowing blood to bypass the lungs and enter systemic circulation.
Why are the lungs bypassed in foetal circulation?
They are not yet fully developed - filled with fluid and not yet involved in gas exchange.
Function of umbilical artery
carry deoxygenated blood and waste products away from the foetus to the placenta for exchange with mother’s blood.
After birth, which structures from foetal circulation are sealed?
Ductus venosus, foramen ovale, ductus arteriosus.
Name of thick, muscular layer of heart wall
myocardium
Function of myocardium
thick, muscular layer that contracts and relaxes to pump and receive blood
What is the myocardium composed of?
cardiac muscle cells (cardiomyocytes)
Name of innermost layer of heart wall
endocardium
What is the endocardium?
the innermost layer of the heart wall. It is thin (single layer of endothelial cells) and has a smooth lining.
Function of endocardium
reduces friction and prevents blood clot formation
Name of irregular muscular projections on the inner surface of ventricles
trabeculae carnae
Where are trabeculae carnae found?
Inner surface of ventricles
What layer of the heart contains coronary arteries and veins?
epicardium (visceral layer of serous pericardium) - outermost layer of heart wall before cavity
Which heart layer makes up the epicardium?
Visceral layer of serous pericardium - outermost layer of heart wall
Function of coronary arteries
supply oxygenated blood to the heart muscle from the aortic sinus.
Function of coronary veins
transport deoxygenated blood from the heart muscles into the RA (mainly via coronary sinus)
What are the aortic sinuses?
3 widenings/dilations of the blood vessel wall above the aortic valve
Where to the left and right coronary arteries arise from?
the left and right aortic sinuses (2/3)
Where an external pacemaker typically placed?
Right auricle / appendage (close to SAN)
Name of muscle in inner atrial wall
Pectinate muscles / musculi pectinate
Function of pectinate muscles
Allows the atria to stretch and increase its volume when filling with blood
Function of coronary sinus
drains deoxygenated blood from the coronary veins into the RA
Location of pulmonary valve
base of pulmonary trunk between the RV and the pulmonary trunk. Anterior portion of heart
How many cusps/leaflets does the pulmonary valve have?
3
Where is the aortic valve located?
Between the LV and aorta (middle/anterior of heart)
How many cusps/leaflets does the aortic valve have?
3
Function of pulmonary valve
prevents backflow into RV
What is the infundibulum of the RV?
(aka conus arteriosus) is a smooth walled funnel shaped part of the RV leading towards the pulmonary valve (no trabeculae)
Name of the AV valve between the RA and RV
tricuspid valve (3 leaflets)
Name of the AV valve between the LA and LV
Mitral / bicuspid valve (2 leaflets/cusps)
Where are the AV valves positioned in the heart in comparison to the SL (semilunar valves)?
AV valves are more posteriorly situated in comparison to the SL valves which are more anterior in the heart.
What are the chordae tendineae?
String-like structures that anchor the cusps of the tricuspid and bicuspid valves to papillary muscles in the ventricular wall
Function of chordae tendineae
Help valve closure and prevent the inversion of the valve cusps into the atria during ventricular systole.
What are papillary muscles?
Cone-like muscles found in the ventricles that anchor chordae tendineae to the ventricular walls.
Function of papillary muscles
contract to tighten chordae tendineae inorder to stabilise AV valves during ventricular systole.
Branches of the left coronary artery
Anterior interventricular artery / left anterior descending (LAD) artery and the circumflex artery.
What is the name of the groove in which the anterior interventricular artery / left anterior descending artery runs along?
Anterior interventricular groove (anterior part of interventricular sulcus)
Function of the anterior interventricular / left anterior descending artery
Supplies oxygenated blood to the anterior walls of both ventricles and most of the interventricular septum
What is the pulmonary sinus?
Widening / dilation of wall at the base of the pulmonary trunk near the pulmonary valve
Function of the pulmonary sinus
Prevents the cusps of the pulmonary valve adhering to the wall of the pulmonary trunk.
Function of circumflex artery
Supplies blood to the LA and lateral and posterior walls of LV
Name of the venous structure that empties deoxygenated blood from the heart into the RA
Coronary sinus
Where is the coronary sinus found?
In the posterior heart entering at the RA
Which ventricular wall is thicker?
LV wall about 3 times thicker than RV wall
What is the interventricular septum?
Thick muscular wall separating the RV and LV
Branches of the right coronary artery
marginal artery and posterior interventricular artery
Function of the marginal artery
Supplies oxygenated blood to the RV wall
Function of posterior interventricular artery
supplies the posterior of the heart
Function of the right coronary artery
Supplies oxygenated blood to the RA, RV, conducting system (SAN and AVN), and part of the interventricular septum.
Along which sulcus does the posterior interventricular artery run?
Posterior interventricular sulcus
What are septal defects?
Abnormal openings / holes in the interatrial and/or interventricular septum.
Name of condition where there is a hole in the interatrial septum
atrial septal defects
Name of condition where there is a hole in the interventricular septum
ventricular septal defect
Name of condition in which there is a hole both in the interatrial and interventricular septum?
Atrioventricular septal defect
Consequence of atrial / ventricular septal defects
Smaller hole may close themselves. Larger holes can compromise the heart and lungs due to an increased BP
Why is an atrioventricular septal defect a more serious condition?
Blood continually shunts between the atria and ventricles leading to inefficient pumping of blood to the body. Requires surgery
Symptoms of an atrioventricular septal defect
breathing difficulty, racing heart, weak pulse, cyanosed, tire easily
Cause of atrial septal defect (ASD)
incomplete closure of the foramen ovale (used to bypass pulmonary circulation in foetus)
Effect of larger ASD
Hypertrophy of the RA and RV as blood flows from the LA into the RA down the pressure gradient. This increases the blood volume in the right side of the heart so the RA and RV must work harder to accommodate extra blood. .
Which direction does blood flow in an atrial septal defect (ASD) / ventricular septal defect (VSD)?
From the left side to the right (left side is at a higher pressure)
Effect of ventricular septal defect (VSD)
Blood flows from the LV into the RV causing hypertrophy of the RV and pulmonary hypertension as there is an increased blood flow to the lungs.
Name of the 4 heart valves
tricuspid, pulmonary, bicuspid/mitral and aortic valve
What is the cause of the “lub” sound of the heart beat?
The closure of the AV valves during ventricular systole (forcing blood against AV valve cusps)
What is the cause of the “dub” sound of the heart beat?
Closure of SL valves during ventricular diastole
Which is louder, the “lub” or the “dub”?
Lub is louder than dub
Which structures assist in AV valve closure and prevent inversion of the cusps into the atria?
papillary muscles contracting and chordae tendineae tightening (not present in SL valves)
How do SL valves close?
During ventricular diastole, there is a slight backflow of blood in the arteries which fills the half-moon shaped cusps of the SL valves, forcing them to close.
How are coronary arteries filled?
The slight backflow of blood in the aorta during ventricular systole fills the aortic sinuses where the coronary arteries arise from.
Clinical condition that can affect hear valves
infective endocarditis
What is infective endocarditis?
An infection of the endocardium (inner lining of heart) which typically involves heart valves.
Most common form of infective endocarditis
subacute bacterial endocarditis (SBE)
Which valves are most commonly affected by infective endocarditis?
Rheumatic valves, congenitally abnormal valves, prosthetic valves.
What is rheumatic heart disease?
Condition where heart valves are permanently damaged by rhematic fever
What is rheumatic fever?
inflammatory disease that can affect many CTS especially in the heart (can lead to rheumatic heart disease)
Examples of organisms that can cause infective endocarditis
streptococcus viridans / staphylococcus aureus
Oral infection that can cause infective endocarditis
dental abscess (or any procedure that allows bacteria to enter bloodstream)
Symptoms of infective endocarditis
heart murmur, fever, fatigue, weight loss or more severe complications like an embolism (blood clot) or heart failure.
What would cause a heart murmur in infective endocarditis?
Valvular vegetations (growth of infected material on valves) which can cause stenosis or regurgitation.
Stenosis definition
narrowing of valve
Regurgitation definition
backward flow of blood due to valve dysfunction
Which coronary arteries anastomose?
posterior interventricular artery (from R coronary artery) anastomoses with anterior interventricular (LAD) artery.
Tributaries of the coronary sinus
great cardiac vein, middle cardiac vein and small cardiac vein
Which coronary vein bypasses the coronary sinus and drains directly into the RA?
Anterior cardiac veins
Function of great cardiac vein
drains areas supplied by the left coronary artery
Function of middle cardiac vein
drains posterior interventricular region into coronary sinus
Function of small cardiac vein
Drains deoxygenated blood from the right side of the heart into the coronary sinus
What are end arteries?
Arteries that only supply oxygenated blood to a specific portion of tissue
Example of end arteries
coronary arteries
What is coronary artery disease (CAD)?
Condition where coronary arteries are narrowed due to the build up of plaque. This creates a reduced blood flow (ischaemia) to the heart.
What is ischaemia?
Reduced blood supply to part of the body.
What can ischaemia of the heart / coronary artery disease result in?
development of collateral circulation and angina pectoris
What is collateral circulation?
The growth of new blood vessels to pass around an area of reduced blood supply e.g. coronary artery disease. These vessels can rupture.
What is angina pectoris?
chest pain related to CAD
What may result if coronary artery disease is left untreated?
Myocardial infarction (death of heart cells due to lack of blood supply)
What percentage of heart attacks are due to blockages in the anterior interventricular branch (LAD)?
40-50%
What percentage of heart attacks are due to blockages of the right coronary artery?
30-40%
What percentage of heart attacks are due to blockages of the circumflex branch of the LCA?
15-20%
What percentage of heart attacks are due to blockages in the left side of the heart?
up to 70% - worrying because the LCA supplies majority of heart
Why is the anterior interventricular / LAD artery called the widowmaker?
LAD supplies large portion of heart’s blood so a blockage in this artery can lead to a fatal heart attack (MI)
What is a coronary artery bypass?
Surgical procedure involving attachment of healthy blood vessels (grafts) from elsewhere in the body to beyond a coronary artery blockage which restores blood flow to the heart.
Examples of blood vessels used as grafts in coronary artery bypass
saphenous vein (longest vein, in leg), internal mammary/ thoracic artery, radial artery
Why may the internal mammary/thoracic artery be preferred over the saphenous vein in a coronary artery bypass?
Because it is an artery doing an artery’s job.
Function of the heart’s conducting system
ensures synchronised contraction of atria and ventricles for efficient pumping of blood
Where is the sinoatrial node (SAN) located?
right atrium
Function of SAN
generates electrical signals to initiate the heart beat. Acts as the pacemaker (controls heart rate)
Where is the atrioventricular node (AVN) located?
near the interatrial septum
Sequence of the heart conducting system
- SAN generates electrical signals that travel across the atria causing atrial systole.
- The electrical signals gather in the AVN where they transmitted to the bundle of His which splits.
- The signals travel through the left and right bundles in the interventricular septum towards the ventricle walls.
- Purkinje fibres conduct the impulse from the bundles to the ventricular muscle, causing synchronised ventricular systole.
What is the septomarginal trabecula / moderator band?
A thick, muscular structure extending from the interventricular septum to the anterior papillary muscle in the RV.
Function of the septomarginal trabecula / moderator band
Allows a shorter route for electrical impulses to pass from the right interventricular bundle directly to the anterior papillary muscle so it contracts to close the tricuspid valve.
What is atrial fibrillation (AF)?
rapid irregular contraction (quiver) of different parts of the atria
Effect of atrial fibrillation
less efficient blood flow from atria into ventricles. Not immediately life threatening
What is ventricular fibrillation (VF)?
rapid, irregular contraction (quiver) of ventricles
Effect of ventricular fibrillation
blood not pumped through systemic or cardiac circulation. Leads to cardiac arrest
What is the most disorganised form of dysrhythmia?
Ventricular fibrillation (leads to cardiac arrest)
Cardiac arrest vs heart attack
Cardiac arrest due to electrical issue in heart causing loss of consciousness, no breathing, no pulse. Heart attack due to blocked coronary artery (conscious).
What to do if someone has a cardiac arrest?
immediate CPR and defibrillator
Function of arterial system
distribute oxygenated blood from the heart to tissues while maintaining BP
What happens to the arterial walls during systole?
As ventricles pump blood into the arteries, the elastic walls expand.
What happens to the arterial walls during diastole?
Elastic walls recoil to maintain arterial blood pressure for continuous blood flow.
How is blood flow to tissues regulated?
By varying capillary diameter (using precapillary sphincters and arteriole constriction/dilation)
3 histological layers of arterial walls
tunica intima, tunica media, tunica adventitia
What is the tunica intima?
Innermost layer of arterial walls made of endothelium and CT.
Function of tunica intima
has a smooth surface to reduce resistance against blood flow.
What is the tunica media?
Middle layer of arterial walls composed of smooth muscle and elastic fibres.
Function of tunica media
Responsible for vasoconstriction/dilation which regulates blood flow
What is the tunica adventitia?
Outermost layer of the arterial wall composed of CT with collagen an elastic fibres.
Function of tunica adventitia?
structural support and anchors arteries to surrounding tissues
Examples of elastic arteries
aorta, common carotid, subclavian and pulmonary arteries
Examples of muscular arteries
radial, femoral, coronary and cerebral arteries.
What are arterioles?
Terminal branches of arteries supplying the capillary bed
Structural adaptation of elastic arteries
contain abundant elastic fibres in the tunica media
Function of elastic arteries
maintain BP and smooth blood flow (despite pulsatile output from the heart) by expanding and recoiling (lots of elastic fibres)
Function of muscular arteries
Distribute blood to specific organs/regions. Control blood flow by vasoconstriction / vasodilation (SM)
Structural adaptation of muscular arteries
thick tunica media rich in smooth muscle (for vasoconstriction and vasodilation)
Function of arterioles
Regulate blood flow to tissues and systemic BP via their ability to constrict and dilate which alters the resistance to blood flow.
