CVS Flashcards
What is the mediastinum?
central compartment of thoracic cavities
located between 2 pleural sacs
contains most of thoracic organs
superior mediastinum
extends upwards, ending at the superior thoracic aperture
inferior mediastinum
extends downwards, ending at the diaphragm
further subdivided into anterior, middle and posterior
anterior mediastinum
smallest subdivision of the mediastinum, lies between body of sternum, and the transverse thoracis muscles anteriorly and the pericardium posteriorly
continuous with superior mediastinum at the sternal angle and is limited inferiorly by the diaphragm
consists of sternopericardial ligaments - fibrous bands that pass from pericardium to sternum , fat, lymphatic vessels, lymph nodes and branches of internal thoracic vessels
in infants, contains inferior part of thymus
middle mediastinum
coincides with the pericardium, containing the heart, ascending aorta, pulmonary trunk, SVC, arch of azygos vein, and main bronchi
pericardium
double-walled fibroserous membrane that encloses the heart and the roots of the great vessels, much like the pleura encloses the lungs
pericardial sac
lies posterior to body of sternum and the 2nd-6th costal cartilages at the level of T5-T8 vetrbrae
its tough external fibrous layer - fibrous pericardium - continues with the central tendon of the diaphragm
serous membrane of pericardium
parietal layer of serous pericardium -
visceral layer of serous pericardium
fibrous pericardium
fused with tunica adventitia of the great vessels entering and leaving the heart
attached to the posterior surface of the sternum by sternopericardial ligaments
fused with the central tendon of the diaphragm
protects heart from a sudden overfilling because it’s unyielding and closely related to the great vessels that pierce it superiorly and posteriorly
pericardial cavity
potential space between the opposing layers of the parietal and visceral layers of serous pericardium
normally contains thin film of serous fluid that enables the heart to move and beat in a frictionless environment
epicardium
comprised of visceral layer of serous pericardium
thin external layer of heart wall (mesothelium)
reflects from heart and great vessels to become continuous with the parietal layer of serous pericardium
anterior supply of the pericardium
mainly from pericardiacophrenic artery - branch of internal thoracic artery , which may accompany or parallel the phrenic nerve to the diaphragm
smaller contributions come from musculophrenic artery , terminal branch of internal thoracic artery
venous drainage of the pericardium
pericardiacophrenic veins , tributaries of the brachiocephalic veins (internal thoracic)
variable tributaries of the azygos venous system
nerve supply of pericardium
phrenic nerves (C3-C5) a primary source of sensory fibres ; pain sensations conveyed by these nerves are commonly referred to the skin (C3-C5 dermatomes)of ipsilateral shoulder region vagus nerves (CN X) - function uncertain sympathetic trunks - vasomotor
myocardium
thick middle layer composed of cardiac smooth muscle
endocardium
thin internal layer (endothelium and subendothelial connective tissue) or lining membrane of the heart that also covers its valves
apex of heart
directed anteriorly and to the left and is formed by the inferolateral part of the left ventricle
located posterior to the left 5th intercostal space in adults , usually 9cm from median plane
where sounds of the mitral valve closure are maximal (apex beat) the apex underlies the site where the heartbeat may be auscultated on the thoracic wall
base of the heart
heart’s posterior aspect
formed mainly by the LA, with a lesser contribution by the RA
faces posteriorly toward the bodies of the vertebrae T6-T9 and is seperated from them by the pericardium, oblique pericardial sinus, oesophagus and aorta
extends superiorly to bifurcation of pulmonary trunk and inferiorly to coronary sulcus (groove)
receives pulmonary veins on R and L sides of LA and the SVC and IVC at the superior and inferior ends of the RA
what are the 2 divided parts of the mediastinum
superior and inferior
explain how the superior mediastinum is bordered
superior - thoracic inlet inferior - continuous with inferior mediastinum at level of sternal angle anterior - manubrium of sternum posterior - vertebral bodies of T1-T4 lateral - pleurae of lungs
contents of superior mediastinum
neural, vascular and respiratory structures passing from the adjacent regions of neck and abdomen
what are the 3 main branches of the aortic arch
brachiocephalic artery
left common carotid artery
left subclavian artery
what does the brachiocephalic artery supply
right side of head and neck and the right upper limb
what does LCC supply
left side of head and neck
what does left subclavian artery supply
left upper limb
which tributaries of SVC are located in superior mediastinum
brachiocephalic veins
left superior intercostal vein
supreme intercostal vein
azygos vein
what do brachiocephalic veins do
drain blood from upper body
what does left superior intercostal vein do
collects blood from left 2nd and 3rd intercostal vein - drains it into left brachiocephalic vein
what does supreme intercostal vein do
drains vein from first intercostal space directly into the brachiocephalic veins
what does azygos vein do
receives blood from right posterior intercostal veins
left intercostal veins drain first into hemiazygos and accessory hemiazygos veins
what 2 paths does vagus nerve take in superior mediastinum
right vagus nerve
left vagus nerve
what does right vagus nerve do
runs parallel to trachea and passes posteriorly to the SVC and right primary bronchus
what does left vagus nerve do
enters between LCC and Lsubclavian arteries
descends anteriorly to the aortic arch, before travelling posterior to the left bronchus
what are the roots of the phrenic nerve
C3-C5
at what vertebral level is mediastinum divided into superior and inferior
T4
what forms the posterior border of the superior mediastinum
vertebral bodies T1-T4
what is the largest artery in the body
aorta
what does aorta carry
oxygenated blood (pumped by LHS of heart) to the rest of the body
what branches from ascending aorta and where does the ascending aorta lie
lies within the pericardium
coronary arteries branch from it
what do pulmonary arteries carry
deoxygenated blood from RV and deliver to the lungs for gas exchange to take place
what do the arteries begin as and how is it separated from RV
pulmonary trunk
separated by pulmonary valve
at what vertebral level does the pulmonary trunk split into R & L
T5-T6
how many branches do the R & L pulmonary arteries divide into and what do they supply?
divide/bifurcate into 2
supply each lobe of the lung
what do the pulmonary veins carry
receive oxygenated blood from the lungs, delivering it to LHS side of heart to be pumped back around the body
how many pulmonary veins are there?
4 - one superior and inferior for each lung
where can the oblique pericardial sinus be found
within the pericardium, between right and left veins
where is the inferior left pulmonary vein
hilum of lung
where is right inferior pulmonary vein founf
runs posteriorly to the SVC and the RA
what does the SVC carry
receives deoxygenated blood from the upper body (superior to diaphragm, excluding lungs and heart), delivering it to the RA
how is SVC formed?
merging of brachiocephalic veins, which travel inferiorly through thoracic region until they drain into the superior portion of the RA at rib3
what does IVC carry
receives deoxygenated blood from the lower body (all structures inferior to the diaphragm), delivering it back to the heart
how is IVC formed
in the pelvis by the common iliac veins joining together
passes through diaphragm, entering pericardium at the level of T8
drains into inferior portion of RA
what are the 5 surfaces of the heart
anterior (sternocostal) - RV posterior (base) - LA inferior (diaphragmatic) - L&RVs right pulmonary - RV left pulmonary - LV
what are the 4 borders of the heart
right border - RA
inferior border - LV and RV
left border - LV and some LA
superior border - R&LA and great vessels
what are sulci
grooves on the surface of heart
what is the coronary sulcus (atrioventricular)
runs transversely around the heart - represents the wall dividing the atria from the ventricles
contains important vasculatures such as RCoronaryA
what is anterior and posterior interventricular sulci
running vertically on their respective sides of the heart
represent the wall separating the ventricles
what are the pericardial sinuses
oblique pericardial sinus - posterior surface of heart
transverse pericardial sinus - superiorly on heart, can be used in coronary artery bypass grafting
summary of sequence of events during one full contraction of the heart muscle
an excitation signal is created by the sinoatrial node
wave of excitation spreads across atria, causing them to contract
upon reaching the AV node, signal is delayed
then conducted into the bundle of His, down interventricular septum
bundle of His and the Purkinje fibres spread the wave impulses along the ventricles, causing them to contract
