Middle Mediastinum Flashcards
what is the central compartment of the thoracic cavity?
mediastinum
what structures create the boundaries of the superior mediastinum?
superior thoracic aperture to the level of the sternal angle
what are the components of the inferior mediastinum?
anterior, middle, and posterior mediastinum
what is found within the middle mediastinum?
heart, great vessels
what is the pericardium?
double-walled fibroserous sac that surrounds the heart
what are the two layers of the pericardium?
fibrous, serous
what are the two ligaments that help support the fibrous pericardium?
pericardiacophrenic (attaches to diaphragm), sternopericardial (attaches to thoracic cage)
what is the structure of the serous pericardium?
parietal layer, pericardial cavity, visceral layer (aka epicardium)
how are the sinuses of the pericardium formed?
reflections of the visceral layer of serous pericardium
part of the pericardium that extends between the SVC/IVC and between the four pulmonary veins
oblique pericardial sinus
venous drainage of the pericardium goes through which vessel?
pericardiacophrenic vein
what are the nerves that innervate the pericardium?
phrenic nerve (pain), vagus nerve, sympathetic trunk
what are the walls, from external to internal, of the heart?
epicardium, myocardium, endocardium
made up of right/left atria and right/left ventricles, the heart is a four-chambered what?
muscle pump
what is the structure called that is made up of fibrous rings of dense connective tissue that are associated with the openings between heart chambers?
fibrous skeleton
what is the posterior aspect of the of the heart called?
base
what forms the base of the heart? where does it face? what separates it from the skeleton?
left atrium (small contribution from right atrium)
faces T6-9 vertebral bodies
separates by aorta, esophagus, pericardial sac
the base of the heart receives what venous blood from which structure?
pulmonary veins
what forms the apex of the heart? where does it lie?
inferolateral part of left ventricle
posterior to left 5th intercostal space (adults)
what occurs in the apex of the heart, which is the palpable impulse of the heart?
apex beat
what chambers of the heart make up the anterior/sternocostal surface?
right ventricle, some left ventricle
what chambers of the heart make up the diaphragmatic/inferior surface?
left ventricle, some right ventricle
what chambers of the heart make up the pulmonary/left surface? what component of the heart lies within this space?
left ventricle
cardiac notch
what chambers of the heart make up the right border?
right atrium
what chambers of the heart make up the inferior border?
right ventricle, some left ventricle
what chambers of the heart make up the left border?
left ventricle (and left auricle)
what chambers of the heart make up the superior border?
right atrium, left atrium (right auricle, left auricle)
the left atrium receives what vessels from the venous system?
right and left pulmonary veins
where do you listen to heart auscultation to determine valve function?
downstream
what is the reference landmark for heart auscultation?
sternal angle
where do you listen to the aortic valuve?
2nd intercostal space to right of sternum
where do you listen to the pulmonary valve?
2nd intercostal space to left of sternum
where do you listen to the tricuspid valve?
5th intercostal space to left of sternum
where do you listen to the mitral valve?
apex beat
where is there high pressure and low pressure in the circulatory system?
high pressure = systemic circulation
low pressure = pulmonary circulation
what % of people are right coronary artery dominant? what % of people are left coronary artery dominant?
right - 2/3
left - 1/3
where does the right coronary artery arise from? where does it run through and what does it supply?
right aortic sinus
runs in AV sulcus to supply right atrium
what are the branches of the right coronary artery?
SA nodal branch, right marginal branch, AV nodal branch, posterior interventricular branch
what is supplied by the right marginal branch?
right border, right ventricle
what is supplied by the posterior interventricular branch?
left ventricle, right ventricle, posterior 1/3 of IV septum
what, as a whole, does the right coronary artery supply?
right atrium, most of right ventricle, diaphragmatic surface of left ventricle, part of AV septum, SA in 60% of people, AV node in 80% of people
where does the left coronary artery arise from? where does it lie and what does it supply?
left aortic sinus
lies in coronary groove to supply left atrium
what are the branches of the left coronary artery?
SA nodal branch, anterior interventricular branch, circumflex branch
what is supplied by the anterior interventricular branch? what branch does it give off and what does that supply?
left ventricle, right ventricle, anterior 2/3 of IV septum
lateral/diagonal branch supplied left ventricle
what is supplied by the circumflex branch? what does it branch into and what does that supply?
left atrium, left ventricle
left marginal artery supplied left ventricle
what, as a whole, does the left coronary artery supply?
left atrium, most of left ventricle, part of right ventricle, most of IV septum, SA node (40% of people), AS node (20% of people)
where do coronary arteries lie on the heart?
epicardium
coronary arteries send what to the heart muscle?
intramuscular branches
a plexus of what lines the chambers of the heart?
subendocardial arteries
what are subendocardial arteries susceptible to during ventricular contraction?
compression
in the heart, an anastomosis can occur between what structures?
intramuscular branches, subendocardial arteries
what artery is known as the ‘widow maker’?
left coronary artery
cessation of blood flow to the myocardium, known as a heart attack
myocardial infarction
what are two ways to aid blood flow following a MI?
stent, bypass graft
where does venous drainage empty into?
coronary artery or right atrium
what are the two main veins responsible for venous drainage of the heart?
coronary sinus, anterior cardiac veins
what is the path of venous drainage to the coronary sinus?
left marginal artery - left posterior interventricular vein - small cardiac vein - middle cardiac vein - great cardiac vein - coronary sinus
what is the route of lymphatic drainage of the heart?
from subepicardial lymphatic plexus to tracheobronchial lymph nodes
heart is a two pump system - what is the right side responsible for?
pulmonary circulation
heart is a two pump system - what is the left side responsible for?
systemic circulation
what occurs during diastole?
atrial contraction, AV valve opens, ventricular relaxation and filling
what is the pressure like in the ventricle during diastole?
‘normal’ (right side is 0-1 mmHg)
what occurs during systole?
AV valves close, ventricular contraction, semilunar valves open, semilunar valves close
what is occuring during the first heart sound?
AV valve closure
what is occuring during the second heart sound?
Semilunar valve closure
what is the phase called when the semilunar valves open?
ejection phase
during the isovolumic contraction of the ventricles, what happens to volume and pressure?
volume stays constant
pressure is increased (right ventricle 25 mmHg, left ventricle 120 mmHg)
during the isovolumetric relaxation in the ventricles, what happens to volume and pressure?
volume increases
pressure decreases
what is diastasis?
middle stage of diastole where there is atrial contraction and slow ventricular filling
when does the refilling of the ventricles begin? what is this phase called?
when the atria has less blood than the ventricles
rapid filling phase
what is the typical volume of cardiac output? maximum volume of cardiac output?
5-6 L blood/min
13 L blood/min
how does cardiac output increase?
increased work of heart
how do you calculate cardiac output?
heart rate * stroke volume
what is a limiting factor of heart rate?
age
how to calculate estimated maximum heart rate?
220 - age
what is stroke volume?
quantity of blood expelled with each contraction
what determines stroke volume?
preload, afterload, contractility
what is preload?
amount of tension on ventricle before contraction
what is afterload?
load against which the muscle contracts
what is the Frank-Starling Law?
if venous return increases, the stroke volume will increase by the same amount (CO = venous return)
what determines preload?
distensibility (dilation) of cardiac muscle, venous return
what effects venous return?
sympathetic stimulation of heart, sympathetic stimulation of large central veins, sympathetic stimulation of arterioles
what effect does sympathetic stimulation of heart cause?
increases contractility of myocardium
what effect does sympathetic stimulation of large central veins cause?
constriction of veins to maintain central venous pressure
what effect does sympathetic stimulation of arterioles cause?
diversion of blood from inactive tissues
how to calculate contractility?
force * velocity of contraction
what is beneficial about increased contractility?
offset problems with handling venous return or raised systemic arterial pressure
what determines afterload?
compliance/elasticity of vessels, systemic/mean arterial pressure
are large vessels more or less compliant than small vessels?
more
compliance can be affected by smooth muscle tone in what vessels?
arterioles
how do you calculate systemic/mean arterial pressure?
cardiac output * total peripheral resistance
how to estimate MAP?
(diastolic pressure + pulse pressure) / 3
what is pulse pressure?
systolic pressure - diastolic pressure
what blood pressure-related condition decreases stroke volume?
hypertension (HBP)
what is the minimum MAP needed for adequate tissue perfusion?
60 mmHG
what effects MAP?
local metabolic needs, vasoactive substances, central nervous system
what happens to arterioles when more energy is needed? what happens to arterioles when less energy is needed?
arteriole dilation
arteriole constriction
what vasoactive substances affect MAP?
epinephrine, angiotensin, ADH
what role does the central nervous system play in affecting MAP?
SNS stimulations arteriole contraction
what is the conducting system of the heart?
SA node (pacemaker) - AV node - AV bundle (right and left branches) - subendocardial branches (aka purkinje fibers)
what is the innervation of the heart?
cardiac plexuses
what does the sympathetic nervous system do to the heart?
increase heart rate, increase force, dilate coronary arteries
what does the parasympathetic nervous system do to the heart?
decrease heart rate, decrease force, constrict coronary arteries
how do the cardiac muscle depolarize?
in sequence (rhymically)
what is the rhythmicity and conduction rate of SA nodal cells?
highest rhythmicity
slowest conduction rate
where are transitional cells located? what is their rhythmicity and conduction rate?
in nodes and conducting system
slow rhythmicity, fast conduction rate
what is the rhythmicity and conduction rate of Purkinje cells?
slow rhythmicity
fast conduction rate
typical cardiac muscle cells can conduct an impulse - however, they do not do what unless a pathologic situation occurs?
independent rhythms
what are the effects of the sympathetic nervous system on the cardiac plexus?
increase heart rate, impulse conduction, contraction force
what are the effects of the parasympathetic nervous system on the cardiac plexus?
decrease heart rate, reduce force of contraction, constrict coronary arteries
where are parasympathetic presynaptic fibers from in the cardiac plexus?
vagus nerve
where are parasympathetic postsynaptic neurons from in the cardiac plexus?
atrial wall
where are sympathetic presynaptic fibers from in the cardiac plexus?
upper 5 or 6 thoracic spinal cord segments
where are sympathetic postsynaptic fibers from in the cardiac plexus?
cervical and superior thoracic sympathetic chain to SA and AV nodes
where is referred cardiac pain? what is another name for this condition?
substernal and left pectoral region into left medial upper limb
angina
what is referred cardiac pain (angina) caused by?
visceral afferent fibers in sympathetic nerves
angina is pain as being perceived to be where?
in the superficial part of the body
visceral afferent fibers in sympathetic nerves interact with somatic afferent neurons where?
same lower cervical segments of the spinal cord
