B3.085 Heart and Mediastinum Flashcards
pericardium
the sac of connective tissues that encloses the heart and first portion of the great vessels
2 parts that makes up the pericardium
fibrous
serous
2 anatomical regions of serous pericardium
visceral - on heart itself (epicardium)
parietal - forms the inner surface of the wall of the pericardial sac
fibrous pericardium
tough
indistensible
outer portion
fuses with adventitia of great arteria and veins 2-4 cm above the heart
can grow slowly to accommodate an enlarging heart
adventitia
outermost connective tissue
serous pericardium
closed sac covers heart (visceral) and inner surface of fibrous pericardium (parietal)
when do the visceral and parietal layers of serous pericardium become continuous?
at roots of great vessels
form a closed cavity
how much fluid is in the pericardial cavity?
20 (15-50) mL
what is the purpose of fluid in the cavity?
heart can move freely as it beats in a very low friction environment
prevent rubbing against other structures
where is pericardial fluid produced?
visceral pericardium
an ultrafiltrate of plasma
pericardial sinuses
transverse
oblique
transverse pericardial sinus location
passageway between R and L sides of pericardial cavity
anterior to SVC
posterior to ascending aorta and pulm trunk
superior to pulm veins and left atrium
oblique pericardial sinus location
blind pocket
dorsal to L atrium
formed by pericardial reflections surrounding the pulm veins and SVC and IVC
most dependent (lowest) portion of the pericardial sac when a patient lies supine
oblique pericardial sinus
leaking bypasses may result in extra fluid here post surgery
cardiac tamponade
compression of heart due to rapid accumulation of fluid in the pericardial sac
prevents chambers from expanding fully
limits ability to pump blood
what amt of fluid can cause elevated intrapericardial pressures?
80 mL
if slowly progressive, can reach 2 L in extreme cases
classic indications of cardiac tamponade
jugular venous distention
distant heart sounds
hypotension with dyspnea
where can you see jugular venous distention?
external jugular vein on top of sternocleidomastoid muscle
why can you see JVD?
no valves within the vein
ultimate connection to right atrium
blood can get backed up
pericardiocentesis
removal of excess fluid from pericardial sac
18G spinal tap needle
20-80 cc syringe
performed with US guidance
where do you place the needle in pericardiocentesis
just to the left of the xiphoid process
angled 45 deg
pointing towards medial edge of left scapula
pericarditis
inflammation of the pericardial sac lining due to viral or bacterial infections
pain associated with pericarditis
remains substernal some referred pain to back and shoulders rarely radiates down arm worsens when lying down (opposite of MI pain) worsens when inhaling deeply
why does pain worsen when laying down or breathing?
flattening of diaphragm elongates sac causing it to rub against heart
what is pericardial rub
serous layer of pericardium becomes rough (secondarily due to viral infections)
friction and vibrations may occur
specific for acute pericarditis
how does pericardial rub sound
squeaky leather
scratchy, grating
left lower sternum border
louder with forced expiration
what supplies blood to the pericardium
pericardiophrenic artery and vein
runs with phrenic nerve on external surface of fibrous pericardium
what innervates the pericardium
phrenic nerve
diastole
heart fills with blood
systole
heart contracts and pumps blood
S1 sound
closing of atrioventricular valves (simultaneously)
beginning of systole
S2 sound
closing of aortic and pulmonary valves
beginning of diastole
base of heart
posterior aspect
largely the left atrium and a narrow portion of the right atrium
apex of heart
blunt descending projection of left ventricle
diaphragmatic surface of heart
formed by left ventricle and a narrow portion of the right ventricle
sternocostal surface of heart
right atrium and right ventricle
narrow portion of left ventricle
obtuse margin
left margin
rounded left side
left ventral and small extent of left auricle
acute margin
inferior border
where sternocostal and diaphragmatic surfaces meet
formed by right ventricle
right margin
superior vena cava
right atrium
inferior vena cava
coronary culcus
separates atria from ventricles
where to listen to heart valves
A-aortic P-pulmonary T-tricuspid M-mitral L to R across chest
aortic valve auscultation area
right of sternum
2nd intercostal space
pulmonary valve auscultation area
left of sternum
2nd intercostal space
tricuspid valve auscultation area
left of sternum
4th or 5th intercostal space
mitral valve auscultation area
left side at 5th intercostal space
midclavicular line
clinical relevance of fibrous skeleton of heart
if it becomes stretched, heart valves often fail
50% of aortic valve insufficiency is due to aortic root (skeleton) dilation
right atrium walls
larger and thicker than left atrium
1-4 mm
sinus venarum of right atrium
smooth region derived from incorporation of right horn of sinus venosus
auricle of right atrium
R. atrial appendage
corresponds to primitive atrium of embryonic heart, contains pectinate muscles
pectinate muscles of right atrium
ridges of myocardium
only in atrium, not ventricles
crista terminalis of right atrium
junction of rough pectinate muscles vs smooth interior of the sinus venarum
fossa ovalis of right atrium
marks site of embryonic foramen ovale through which blood passes from right atrium to left atrium before birth
opening of coronary sinus
site of venous blood return that has passed through cardiac muscle
valve of inferior vena cava
in embryonic heart, directs blood from IVC through foramen ovale and into left atrium
SVC
large superior opening in the sinus venarum that brings poorly oxygenated blood from the head and upper limbs
IVC
large inferior opening in the sinus venarum that brings poorly oxygenated blood from the abdomen and lower limbs
right atrioventricular orifice
site of blood flow out of right atrium into right ventricle
right ventricle wall thickness
4-8 mm
right atrium volume
75-80 mL
right ventricle volume
120 +20 mL
cusps of tricuspid valve
anterior, posterior, and septal cusps
leaves of the AV valve
trabeculae carnae
irregular muscular elevations on the inner wall of the ventricle
papillary muscles
anterior, posterior, and septal in RV
according to location of their bases off the walls of the ventricle
variable in number
chordae tendineae
fibrous strands connecting papillary muscles to cusps of AV valves
septomarginal trabecula
trabecula carnea that conveys right branch of AV bundle to anterior papillary muscle
conus arteriosus
smooth walled outflow tract to pulmonary trunk
separated from ventricle proper by supraventricular crest
pulmonary valve
allows blood to exit the right ventricle and into the pulm trunk past the 3 semilunar cusps
left atrium volume
55-65 mL
left atrium location in body
posterior chamber
anterior to esophagus
pulmonary valves
2 right and 2 left pulm veins carry oxygenated blood into the L atrium
smooth walled part of LA
derived from incorporation of pulm veins
fossa ovale of LA
slight depression in the interatrial wall
rough walled part of LA
derived from embryonic atrium; contains pectinate muscles
left atrial appendage/auricle
often closed in patients w atrial fibrillation due to concern about clot formation
AV orifice
blood exits into the L ventricle through the mitral valve
watchman device
closes left atrial appendage
patients w atrial fibrillation on blood thinners
left ventricle volume
125 + 15 mL
left ventricle wall thickness
8-14 mm
2-3x thicker than RV
mitral valve cusps
anterior and posterior cusps of the AV valve
trabeculae carneae of LV
irregular muscular elevations on inner wall of the vetricle
papillary muscles in LV
only anterior and posterior papillary muscles
chordae tendineae in LV
fibrous strands connecting papillary muscles to each cusp of the mitral valve
aortic valve
allows blood to exit the LV past the 3 semilunar cusps of the aortic valve
leads to the ascending aorta
function of papillary muscles and chorda tendineae
restrict valve cusp movement during ventricular systole
prevent blood from regurgitating back into atrial chamber
papillary muscle rupture
can happen as a complication of MI
leads to AV dysfunction
regurgitation can present as a diastolic murmur
cause of left ventricular hypertrophy
chronic hypertension or aortic valve stenosis (pressure overloads)
effect of volume overloading
aortic or mitral valve regurgitation = LV hypertrophy and chamber enlargement
result of aortic valve insufficiency
blood regurgitation
what is mitral valve prolapse
mitral valve everts into the left atrium when the left ventricle contracts during systole
result of mitral valve prolapse
common and often benign
can develop into mitral valve regurgitation —chest pain, cardiac arrhythmia, SOB
why is mitral valve prolapse more common than tricuspid valve prolapse?
left ventricle contracts at higher pressure to pump blood throughout the body than the right ventricle which only needs to pump blood to the lungs
discuss the development of aorta and pulmonary trunks from a single outflow track
aorta ends up slightly posterior and has a posterior cusp
pulmonary trunk ends up anterior and has an anterior cusp
both have L and R cusps
when is blood flow into coronary arteries the greatest
during diastole
opposite of most arteries in the body
max blood flow when cardiac tissue is most capable of receiving blood
bicuspid aortic valve
most common congenital heart anomaly
1-2% of pop
males 2x more affected
if calcification occurs, more likely to cause aortic valve stenosis than a normal tricuspid aortic valve
result of stenosis of aortic valve
excessive turbulence
long term can cause ascending aortic aneurysmal
right coronary artery
origin: right aortic sinus
distribution: right atrium, SA and AV nodes, posterior portion in IV septum
artery to sinoatrial node
present in 60% of pop
origin: right coronary artery
distribution: SA node and pulm trunk
right marginal artery
origin: right coronary artery
distribution: right ventricle and apex
post interventricular (posterior descending)
origin: right coronary artery
distribution: right and left ventricles and IV septum
AV node artery
origin: right coronary artery (80% of the time)
distribution: AV node
left coronary artery
origin: left aortic sinus
distribution: left atrium and ventricle, IV septum, AV bundle, and AV node (20% of the time)
artery to sinoatrial node
present in 40% of population
origin: left coronary artery
distribution: SA node and left atrium
artery to IV (left anterior descending)
origin: left coronary artery
distribution: right and left ventricles, IV septum
lateral diagonal branch
origin: LAD
distribution: left ventricle (anterior)
circumflex
origin: left coronary artery
distribution: left atrium and ventricle
distribution: left atrium and ventricle
left marginal
origin: left circumflex
distribution: left border of left ventricle
what does the right coronary artery supply?
RA most of RV diaphragmatic surface of LV posterior 1/3 of AV septum SA node in 60% of people AV node in 80% of people
what does the left coronary artery supply?
LA most of LV anterior 2/3 of AV septum AV bundles SA node in 40% of people AV node in 20% of people
right dominant distribution
80% of people
posterior IV artery arises from right coronary artery
left dominant distribution
10% of population
circumflex gives off posterior IV artery
balanced distribution
10% of population
both R and L coronary arteries supple the posterior IV artery
3 most common sites of artery occlusion on the heart
- 40-50% LAD, widowmaker
- 30-40% right coronary
- 15-20% left circumflex
coronary artery bypass surgery
CABG
bypass of coronary artery blockage
most typical format of CABG
distal end of internal thoracic artery is attached to existing coronary artery distal (downstream) of blockage
additional arteries or veins used in CABG
radial artery from arm
great saphenous vein from leg
attached to ascending aorta and distal to blockage
cardiac veins
most blood passed through the coronary arteries returns to the venous circulatory system at the RA through either the coronary sinus (most) or by anterior cardiac veins
coronary sinus
direct continuation of great cardiac vein
lies in posterior part of coronary sulcus and opens into RA
receives all cardiac veins except anterior cardiac veins and smallest cardiac veins
great cardiac vein
beside anterior IV artery
middle cardiac vein
alongside posterior IV artery
small cardiac vein
along acute margin of RV
parallels right marginal artery
anterior cardiac veins
2 or 3 small veins that drain sternocostal surface of RV directly into RA
what is the SA node
initates heartbeats
collection of specialized cardiac cells
where is the SA node
right atrial wall at superior end of sulcus terminalis near SVC
rate of contraction of SA node
stimulated by sympathetic cardiac nerves
decreases when stimulated by parasympathetic cardiac nerves
atrial natriuretic factor/peptide
made by right atrial cardiac cells
affect total blood volume
acts on kidney to increase sodium and water excretion to reduce blood volume
where is the AV node
inferior aspect of the intraatrial septum near the opening of the coronary sinus
artificial cardiac pacemakers
can substitute for SA, AV or AV bundle
generates electrical impulses
implanted under the skin on the anterior chest wall just inferior to the clavicle
leads are threaded through venous system to the site of SA or near apex (to replace AV)
sympathetic innervation of the heart
cervical and thoracic sympathetic ganglia
cell bodies from C4 to T5
parasympathetic innervation of the heart
vagus CN
cranial nerve X
discuss cardiac referred pain
afferent innervation to the heart returns to CNS with sympathetic nerves that innervate upper thoracic wall and medial side of left upper extremity
heart attack pain in men
chest
left arm/shoulder
SOB
heart attack pain in women
chest nausea jaw, neck, back pain left arm.shoulder SOB
thymoma
tumors of the thymus
rarecan grow and affect the trachea, SVC, and occasionally other structures
great veins in superior mediastinum
internal jugular - blood from head and neck
subclavian - blood from arm
brachiocephalic - IJ + S
SVC
left (longer) and right (short, vertical) brachiocephalic veins together
returns to RA
receives arch of the azygos vein
great arteries
aorta
pulmonary arteries
3 parts of the thoracic aorta
- ascending
- arch
- descending
ascending aorta
begins w pericardial sac at the aortic valves and ascends behind sternum to sternal angle
arch of the aorta
lies behind manubrium in front of trachea
descending aorta
begins at sternal angle and descends just anterior to vertebral bodies
where does the trachea bifurcate
sternal angle of Lewis
T4-T5
esophagus
enters superior mediastinum at a position between trachea and vertebral column
passes through diaphragm at T10
3 diaphragm openings
IVC - T8
esophageal hiatus - T10
aortic hiatus - T12
phrenic nerve
arises from C3,4,5
innervate diaphragm
remain anterior to root of lungs in thorax
refer diaphragm pain to neck
cranial nerve X (vagus)
major parasympathetic nerve supplying all thoracic organs and upper 2/3 of abdominal organs
right vagus location
enters superior mediastinum on right side of trachea
passes posterior to the right brachiocephalic vein and IVC
descends along posterior of esophagus
left vagus location
enters superior mediastinum by descending along the left surface of the arch of the aorta
stays posterior to root of the lung
descends along anterior of esophagus
recurrent laryngeal nerves
control voice box in neck
both right and left vagus
right recurrent laryngeal nerve
runs under the right subclavian artery
comes off vagus at T1
left recurrent laryngeal nerve
runs under the arch of the aorta lateral to the ligamentum arteriosus
comes off the vagus at T4-T5
autonomic plexuses of the thorax
cardiac, pulmonary, and esophageal
mixed plexuses that contain both sympathetic and parasympathetic fibers
T1-T5 contribute
thoracic splanchinic nerves
- greater = T5-T9
- lesser = T10-T11
- least = T12
thoracic duct
begins in abdomen as cisterna chili (L1-L2)
receives lymph from both sides of the thoracic cavity and abdominal cavity and both lower limbs
empties into the junction of the left subclavian and left IJ veins
location of thoracic duct
between azygos vein and descending thoracic aorta
anterior to thoracic vertebral bodies
chylothorax
lymph in pleural cavity
>50% come from malignant etiologies
azygos system of veins
drains blood from the thoracic wall
connects to both IVC and SVC
hemizygos
vein on the inferior aspects along the left side of thoracic vertebrae
accessory hemizygos
vein on the superior aspect of the left side of the thoracic vertebrae
pancoast syndrome
apical bronchogenic carcinoma of the lung can impinge on adjacent anatomical structures
-can cause Horners (ptosis, myosis, and anhydrosis)
neurovascular compromise of the arm
