Circulatory System Flashcards
Label the sternum and thoracic skeleton
Sternum: Manubrium Body Manubriosternal joint Xiphoid process
Thoracic Skeleton: Clavicle Scapula Sternum True ribs (1-7) False ribs (8-10) Floating ribs (11, 12) Costal cartilages Thoracic vertebrae Diaphragm
The chest cavity is divided into…
Median partition - mediastinum
Lateral pleura & lungs
The mediastinum extends to…
Root of neck above
Diaphragm below
Sternum anteriorly
Vertebral column Posteriorly
What are the subdivisions of the mediastinum?
Superior, inferior, anterior, middle and posterior
What is the pericardium?
Pericardium is a fibro-serous sac that encloses the heart and the roots of the great vessels
The heart lies within the pericardium in the mediastinum
Functions to;
restrict excessive movements of the heart as a whole
serve as a lubricated container in which the different parts of the heart can contract
What is fibrous pericardium?
Strong, fibrous layer
Firmly attached below to the central tendon of the diaphragm
Fuses with outer coats of great blood vessels that pass through it
Attached in front to sternum by sternopericardial ligaments
What is serious pericardium?
Two layers Parietal lines the fibrous pericardium Visceral closely covers heart (epicardium) Space between called pericardial cavity Contains pericardial fluid; lubricant
Why is LV thicker than RV?
Greater force required to pump blood through the body than to the lungs, so muscular wall of left ventricle is thicker than the right
What separates the four heart chambers?
Inter-atrial, interventricular and atrioventricular septa separate the four chambers of the heart
Label the heart structure
SVC- superior vena cava
IVC- inferior vena cava
What are the features of the right atrium?
Forms right border of heart
Receives blood through the SVC, IVC and coronary sinus
Coronary sinus returns blood from the walls of the heart itself
Label the right atrium
Crisla terminalis Musculi pectinati Fossa ovale Atroventricular orifice Right auricle
What are the features of the right ventricle?
Blood entering from right atrium moves in a horizontal and anterior direction
Outflow tract: pulmonary trunk
Pulmonary trunk closed by pulmonary valve–3 semilunar cusps
Label the right ventricle
Chordae tendinae
Tricuspid valve
Trabeculae carnae (including papillary muscles)
What are the features of the left atrium?
Forms most of base of heart
Blood enters X4 pulmonary veins
Anterior half is continuous with left auricle–No equivalent to the crista terminalis
Depression on interatrial septum is the valve of the foramen ovale
Blood moves into left ventricle via atrioventricular orifice–Guarded by the mitral valve
Label the left atrium
Left auricle
4 pulmonary veins
Foramen ovale
Mitral valve
What are the features of the left ventricle? Label the structure
Blood flows into the aortic vestibule
Guarded by the aortic valve
Similar in structure to pulmonary valve
As blood recoils after ventricular contraction, and fills the aortic sinuses formed by the cusps, it is forced into coronary arteries
What is the cardiac silhouette?
Cardiac silhouette refers to the outline of the heart as seen on frontal and lateral chest radiographs
The size and shape of the cardiac silhouette provide useful clues for underlying disease
From the frontal projection, the cardiac silhouette can be divided into right and left borders:
the right border is formed by the right atrium
the superior vena cava entering superiorly and the inferior vena cava often seen at its lower margin
the left border is formed by the left ventricle and left atrial appendage/auricle
the pulmonary artery, aortopulmonary window and aortic notch extend superiorly
Describe the pulmonary trunk
Arises slightly anterior to aortic orifice
Ascends posteriorly and to the left, lying anterior and to left of ascending aorta
Divides into left and right
Left: inferior to aortic arch
Right: posterior to ascending aorta and SVC
What are the features of the aorta?
Ascending within pericardial sac
Enters superior mediastinum = arch
Arch lies behind manubrium sterni, in front of trachea
Arches upwards and backwards
Becomes continuous with descending aorta
Aortic arch branches:
Brachiocephalic trunk (divides into right subclavian and right common carotid
Left common carotid
Left subclavian
What are the two parts of the vena cava?
Superior Vena Cava
Inferior half within pericardial sac
Inferior Vena Cava
Passes through diaphragm at T8 and enters fibrous pericardium
What are auscultation points and what can you hear from them?
Cardiac auscultation enables heart sounds to be listened to using a stethoscope for cardiac assessment
Normal heart sounds (lub-dub) are produced by the closure of the valves during a contraction
Valve sounds travel through the surrounding structures of the thoracic wall
Placement of the stethoscope differs from the position of the valve being examined (downstream from flow of blood)
Palpation of the ribs is used to determine which level a stethoscope needs to be placed
What is it called if a heart sound differs due to turbulent blood flow?
Heart murmur
What are the 4 auscultation points?
Aortic valve: medial end of the 2nd right intercostal space
Pulmonary valve: medial end of the 2nd left intercostal space
Tricuspid valve: 4th intercostal space at the lower left sternal border
Mitral valve: 5th left intercostal space at the mid-clavicular line
What are the three layers of the heart?
–Endocardium: inner most layer. Lines Cavities and heart valves
–Myocardium: composed of cardiac muscle and responsible for contraction of the heart
–Epicardium: outermost layer of the heart, formed by the visceral layer of the serous pericardium. It is composed of connective tissue and fat
Describe the endocardium
Structurally, the endocardium is comprised of loose connective tissue and simple squamous epithelial tissue
Similar in its composition to the tunica intima which lines the inside of blood vessels
Deep to the endocardium is the subendocardial tissue, which contains loose vascularized connective tissue
Subendocardial tissue also contains nerves as well as Purkinje fibres
In areas where the myocardium is thin (i.e. atria) the endocardium is relatively thicker
In addition to lining the inside of the heart, the endocardium also regulates contractions and aids cardiac embryological development
Describe the myocardium
Like the muscular tunica media, the myocardium is the middle layer of the heart that contains a large quantity of muscle cells
Cardiomyocytes are arranged in a branched, linear manner
This layer is highly vascularized and the cardiomyocytes contain glycogen granules as an additional energy source
What connects cardiac myocytes?
Intercalated discs, forming cardiac syncytium to enable transmission of electrical impulses for contraction
Describe the epicardium
The pericardium is a fibrous double layered connective sheath that encases the heart within the mediastinum
The visceral portion of the serous pericardium (that is in contact with the heart) is called the epicardium
It is a mesothelium derivative that is rich in adipocytes and neurovascular tissue
Describe the cardiac skeleton
Collection of dense, fibrous tissue in the form of four rings which interconnect in a plane between the atria and ventricles
Surround the AV orifices, aortic orifice and opening of pulmonary trunk
Helps maintain integrity of openings and provides attachments for cusps
Separates muscular wall of atria from ventricles, as well as electrically isolating the ventricles
The AV bundle is the single connection between these two groups of myocardium
Cardiac skeleton
Tricuspid valve
Bicuspid (mitral) valve
Semilunar valve structure
Auscultation points
• Aortic valve: medial end of the 2nd right
intercostal space
• Pulmonary valve: medial end of the 2nd left
intercostal space
• Tricuspid valve: 4th intercostal space at the
lower left sternal border
• Mitral valve: 5th left intercostal space at the
mid-clavicular line
What happens in regurgitation?
(leaky valve) • Retrograde flow of blood either from the ventricles, or in the case of the semilunar valves back into the ventricles from the outflow tracks
• Heart has to pump harder, potentially
leading to pathological hypertrophy or
heart failure
• Causes include prolapse (valve leaflets
bulge back into the atrium),damaged
chordae tendineae, rheumatic fever
What happens in valve stenosis?
(narrowing of the valve)
• Main causes are calcification,
congenital defects and rheumatic fever
• Heart must use more force to pump
blood through the hardened valve
leaflets
• May lead to pathological hypertrophy
of the heart chamber
What is atresia?
(congenital)
• Valve doesn’t form properly
• Often means there is a patent foramen
ovale and ductus arteriosus, to allow
blood to reach the lungs via an
alternative route
Valve regurgitation may be a result of damage to which structure?
Chordae tendineae
How does the chordae tendineae attach to ventricular wall?
Papillary muscles
Common causes of valve regurgitation?
Congenital
Stenosis
Endocarditis
Rheumatic fever
Describe the features of foetal circulation
Pulmonary circulation not functional in foetus bc oxygen delivered from placenta through umbilical vein and 2 umbilical arteries wrapped around it.
Umbilical vein bypasses liver through Ductus Venosis and empties into right atrium of heart.
Blood bypasses lungs through 1) Foramen Ovale (right to left side of heart) and blood from right ventricle pumped up through pulmonary trunk and passes through 2) Ductus Arteriosus into aorta.
Ductus Arteriosus: Bypasses lungs just AFTER where 3 branches from aortic arch have branched off- distal to subclavian.
What arteries supply the heart and where do they arise from?
Coronary arteries
• Two: right and left
• Arise from aortic sinuses of the ascending aorta: 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.
Right coronary artery: arises from? Descends where? Does it branch?
Arises from aorta and runs forward
between pulmonary trunk and right
auricle
• Descends almost vertically in the right
atrioventricular groove
• At inferior border continues posteriorly
to anastamose with left coronary artery
• Offers a marginal branch and a
posterior interventricular branch
Label the arteries
The right coronary artery (RCA) branches to form the right marginal artery
(RMA) anteriorly
In 80-85% of individuals, it also branches into the posterior interventricular
artery (PIv) posteriorly.
Left coronary artery: arises from where?
Usually larger than right
Arises from aorta and passes
forward between the
pulmonary trunk and left
auricle
Left coronary artery: branches
The left coronary artery (LCA) initially branches to yield the left anterior descending (LAD), also called the anterior interventricular artery
• The LCA also gives off the left marginal artery (LMA) and the left circumflex artery (Cx)
• In ~20-25% of individuals, the left
circumflex artery contributes to the
posterior interventricular artery (PIv)
Coronary artery distribution: RCA vs LCA
Coronary artery variation:
What is the most common presentation?
RIGHT DOMINANT artery
Right dominant artery variation
Posterior interventricular/descending artery (PDA)
Supplies large portion of posterior wall of left ventricle
Left dominant branch variation
Posterior interventricular arises form the circumflex
Additional variation in relation to SA and AV nodes
- Normally supplied by RCA
- Sometimes vessels from circumflex of LCA
Co-dominant variation
Indicator of left ventricular strength: Left dominance associated with worst prognosis
Coronary artery angiography utilises which peripheral vessel to inject die into the coronary vasculature?
Femoral or radial artery
Why is prognosis of people who are right dominant better than those who are left dominant?
In right coronary circulation, PDA (branching from RCA) serves as a collateral vessel to basal left anterior descending artery via septal perforators -> so patient with proximal left anterior descending coronary artery stenosis has benefit of possibly receiving supply from right coronary artery if they’re right heart dominant
So if someone has blockage on left side of heart, if PDA branching from right, because of collateral vessels that run from it there’s a chance that there will be some supply to structures on left side through RCA
So collateral circulation MAY be enough to bypass blockage in LAD to provide enough oxygenated blood so cardiac muscle can thrive and survive
Why is dominance important in cardiac surgery planning?
In coronary artery bypass grafting- surgeon must knew what vessels are suitable to receive distal anastomosis of venous graft. For occlusion of RCA or LCA the PDS might be chosen if suitable (depends on patency). Venous conduit is then sutured into a portion of RCA that is distal to occlusion
Aortic valve stenosis affects which chamber of the heart?
Left ventricle, can cause LV hypertrophy
Coronary sinus receives what 4 major tributaries?
• Great, middle, small and posterior cardiac veins
• Anterior cardiac veins are very small, draining only the anterior portion of the
right ventricle
Great cardiac vein
- Also known as the anterior interventricular vein
- Largest tributary of the coronary sinus
- Runs from apex to pass around the posterior surface of the heart
- Gradually enlarges to ‘form’ the coronary sinus
Small cardiac vein
• 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
Middle cardiac vein
• Also known as the posterior interventricular vein
• Begins at the apex of the heart and ascends in the posterior interventricular groove
to empty into the coronary sinus
Posterior cardiac vein
- 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
Anterior and smallest cardiac vein: Arise from where and features?
Anterior cardiac veins
- Small; arise on anterior surface of right ventricle
- Cross coronary sulcus and enter anterior wall of right atrium
Smallest cardiac veins (aka thebesian)
-Valve-less
-Drain directly into cardiac chambers; numerous in right atrium and ventricle
Occasionally associated with left atrium
What artery is most commonly occluded?
LAD is the most commonly occluded of
the coronary arteries
• Main supply to interventricular septum
and the bundle branches of the
conducting system
• Infarction of the conduction system
What can happen if right coronary branches are occluded?
Right coronary branches supply SA and
AV nodes; blockage can lead to conduction
abnormalities
Angina vs MI
BOTH SYMPTOMS OF CORONARY ARTERY DISEASE
Angina • Ischaemia but falls short of necrosis • Stable: predictable; after exercise of exertion; pain eases after rest • Unstable: more severe; can happen during resting
MI
• Complete block of an artery due to
embolus
• Usually result of atherosclerosis
• Progressive blockage of a coronary artery
can encourage collateral branching which
can help in the event of an M.I.
CABG (coronary artery bypass graft)
Saphenous vein usually HARVESTED. without mercy
Radial artery occasionally used
Sometimes even internal thoracic artery if you’re feeling spicy enough
Method: site of complete occlusion due to plaque, so new vessel taken from aorta and taken downstream of occlusion to bypass blockage
