Lecture 1: Introduction Flashcards
what is contained in the thoracic cavity
ribs
sternum
T/S vertebrae
Heart
lungs
upper abdominal organs
what is contained in the mediastinum
all thoracic viscera except lungs
heart
cardiac vasculature
esophagus
trachea
thymus
thoracic duct/lymph structures
phrenic nerve
cardiac neural structures
contents can shift around
location of mediastinum
between lung pleurae
basic anatomy/location of heart
size of closed fist
apex at 5th intercostal space of midclavicular line
3 tissue layers of heart
pericardium = outer layer/ “sac”
myocardium = muscular layer
endocardium = inner layer “lining”
describe the pericardium
triple walled sac that contains heart
layers:
- fibrous pericardium = outermost; anchored to diaphragm
- parietal layer = provides lubrication
- visceral layer (epicardium) = contains coronary vessels on heart surface
pericardium has 10-20mL pericardial fluid within pericardial cavity that decreases friction throughout cardiac cycle
describe the myocardium
heart muscle
various thickness in different chambers
describe the endocardium
inner lining of heart
simple squamous endothelium
valves and chordae tendinae
contains electrical components
function of right atria
receives deoxygenated blood from venae cave
function of left atria
receives oxygenated blood from pulmonary veins
thicker walls to accommodate for higher pressure of blood coming from pulmonary circulation
describe atria in general
separated by interatrial septum
contain auricles to increase available capacity as needed
pectinate muscles contribute to strength of atrial contractions
right ventricle function
receives deoxygenated blood from R atria via tricuspid valve
sends blood to lungs via pulmonary valve and arteries
left ventricle function
receives oxygenated blood from L atrium via mitral valve
sends blood to body via aortic valve and aorta
general structure of heart valves
unidirectional flow
leaflets attached to papillary muscles via chordae tendinae
function of atrioventricular valves
prevents back flow during ventricular contraction
AV valves = tricuspid and mitral (bicuspid)
function of semilunar valves
prevent back flow during ventricular relaxation
SL valves = pulmonary and aortic
when do coronary arteries receive blood
during ventricular relaxation while aortic valve is closed
branches of L coronary artery and where those branches supply blood to
L anterior descending = anterior L ventricle, anterior 2/3 IV septum, and small part of R ventricle
Circumflex = L atrium, posterolateral L ventricle, SA node (40%), and Bundle of His
branches of L anterior descending artery (widow maker)
diagonal
septal branches
endocardial
branches of cirfumflex artery
posterior L ventricular
L obtuse marginal
branches of R coronary artery
R marginal artery
R posterior descending
where does R coronary artery supply
R atrium
SA node (60%)
AV node
where does the R marginal artery supply blood
Lateral R ventricle
where does the R posterior descending artery supply blood
inferior L ventricle
posterior 1/3 IV septum
what is coronary dominance
designates the coronary artery system that is responsible for majority of the posterior L ventricular circulation
R dominant (most common) = R coronary aa gives off posterior descending aa
L dominant = circumflex gives off posterior descending aa
superior vs inferior vena cava collect venous blood from
superior = upper body and head
inferior = lower body and trunk
where do coronary arteries arise from
off aortic sinus of Valsalva
aortic arch gives off what
3 arteries that supply BUE and head
descending aorta bifurcates into
B iliac arteries
descending aorta = highest BP in body
list the path of blood flow starting with the venae cavae
venae cava
R atrium
tricuspid valve
R ventricle
Pulmonary valve
pulmonary artery
lungs
pulmonary veins
L atrium
mitral valve
L ventricle
Aortic valve
aorta
systemic circulation
compare/contrast arteries vs veins
arteries
- oxygenated blood away from heart
- thicker walls
veins
- deoxygenated blood to heart
- thinner walls
- large diameter
- valves prevent back flow
capillaries = O2/CO2/nutrient exchange
describe the layers of blood vessels
tunica intima = inner layer; epithelial cells
tunica media = smooth mm
tunica adventitia/externa = outer layer; collagen and elastin
describe the cell makeup of the myocardium
cardiac myocytes = connected mechanically and electrically
sarcomeres have actin and myosin filaments for contractility (force of contraction correlated with Ca++ available for binding)
very high # mitochondria (50% myocardial mass); high ATP production
describe the physiology behind contractions in the heart
Na-K pump maintains AP and keeps more Na outside cell and more K inside
Ca binds to myocardial filaments to induce contraction
sarcoplasmic reticulum absorbs Ca and causes relaxation
increase in Ca = increase contractility = higher HR
myoglobin stores O2 during diastole and releases O2 during systole
characteristics of myocardium
automaticity = pacemaker abiltiity
conductivity = conducts impulses to one another
contractility = shorter or longer
irritability = contract on their own and/or send impulses without first being stimulated from another source
describe the function of the sympathetic portion of the cardiac plexus
increase HR
increase contractility
coronary aa vasodilation
describe the function of the parasympathetic portion of the cardiac plexus
decrease HR
decrease contractility
SA node controlled by R vagus
AV node controlled by L vagus
describe the 3 sympathetic cardiac receptors
Adrenergic (alpha 1) = causes peripheral vasoconstriction (increase SVR); epi and norepi
beta 1 = cause increased HR and SV
beta 2 = cause pulmonary and peripheral vasodilation (decrease SVR)
describe the parasympathetic cardiac receptor
muscarinic = decrease HR
acetylcholine
purpose/conduction of the SA node
“pacemaker”
60-100 bpm pace
in R atrium near superior vena cava
action of cardiac receptors
a1 = vasoconstriction = increased systemic vascular resistance
b1 = increase HR and SV = increase CO
b2 = vasodilation = decreased SVR
purpose of AV node
“gate keeper”
40-60 bpm internal pace
between intertribal and intraventricular septum
describe the path of electrical conduction of the heart
SA node generates AP
impulse to R and L atrium and mm contracts
impulse to AV node; slows due to Ca++; ventricles fill
impulse to Bundle of His in intraventricular septum
impulse to R and L bundle branches; depolarizes ventricles and causes ventricular contraction
to Purkinje fibers where electrical activity spreads from endocardium to epicardium
what is a cardiac cycle
one cycle of atrial and ventricular contraction
systole = contract
diastole = relax
list the phases of systole/diastole and what is happening with each
atrial systole = blood ejected to ventricles
atrial diastole = atra relaxed; prepare for next fill cycle
early ventricular systole = AV valves close, but not enough pressure to open SL valves
late ventricular systole = SL valves open and blood is ejected
early ventricular diastole = drop in pressure closes SL valves
late ventricular diastole = all chambers closed; passive ventricular filling
normal sounds of heart
S1 “lub” = closure of AV valve in early ventricular systole; peak of R wave
S2 “dub” = closure of SL valves; termination of ventricular systole and start of ventricular diastole; end of T wave
P wave indicates what
atrial contraction
PR segment indicates
ventricular filling
QRS complex indicates
ventricular contraction
ST segment indicates
plateau phase of ventricular relaxation
T wave indicates
ventricular relaxation
what is stroke volume
volume of blood ejected per contraction
what is cardiac output
volume of blood ejected from L ventricle per minute
4-6 L/min
equation for cardiac output
CO = HR x SV
factors that affect cardiac output
preload = how full is the tank
contractility = how good is the squeeze
afterload = how loose is the vasculature
preload
degree to which heart mm can stretch before contraction
correlated to end diastolic volume (EDV) - max amount of blood returning to heart
directly proportional to stroke volume; more blood that returns to the heart the greater volume that can leave
what is frank starling law
states that greater volume of blood is ejected when a greater volume returns
if myocardial fibers are too stretched or shortened, contraction strength is decreased
contractility
ability of ventricles to contract to send blood to lungs and periphery
increase in HR = increase contractility
in HR > 120 there is an increase in Ca++ resulting in stronger contraction
reflected by ejection fraction
what is ejection fraction
best indicator for cardiac function
ratio of volume of blood ejected vs volume received prior to contraction
some blood must remain in ventricles to maintain certain degree of stretch
what is after load
force that resists contraction
pressure within the arterial system during systole
expressed as systemic vascular resistance (SVR) or total peripheral resistance (TPR)
increase in after load = decrease in stroke volume and decrease in cardiac output
what is cardiac index
measure of how well heart is functioning
more individualized than cardiac output or ejection fraction
correlates blood volume pumped by heart to body surface area
normal is 2.5-4.0 L/min/m^2
if CI falls below 2.2 pt is likely in cardiogenic shock
describe how venous return works
venous pressure <arterial pressure
distal venous pressure > proximal
these things allow for gradient of blood flow back to heart
during inhalation, increased abdominal pressure creates vacuum in thoracic cavity pulling blood back to heart
what does the oxyhemoglobin dissociation curve show
relationship between amount of O2 bound to Hgb
ability of RBCs to release O2 to tissues that need it most
what is relevant about SpO2 of 90%
90% = PaO2 of 60mmHg
this is the minimum O2 concentration needed to prevent ischemia in tissue
what does a L shift on the oxyhemoglobin dissociation curve indicate
Hgb holds onto O2 since tissues don’t need it
more O2 bound to Hgb
lower partial pressure O2
lower temp and mm work
higher blood pH (less acidic)
what does a R shift on the oxyhemoglobin dissociation curve indicate
releases O2 to tissues that need it more
less O2 bound to Hgb
naturally happens during exercise
higher temp and mm work
lower blood pH (more acidic)
