midterm physio Flashcards
weight of heart
300 grams
rate of heart
70 >100,000/day, >35 million/year
where is heart located?
mediastinum
What is heart bordered by?
right and left parietal pleurae, sternum, spine, and diaphragm
what fraction of the heart lies left of the midline?
2/3
Apex
lower point of heart (pointy) lies on diaphragm at approx. 5th intercostal space
Base of heart
upper border of heart (broad)
Length of heart
approx 5 in. long
Pericardial sac
wraps around heart and roots of great vessels
Fibrous pericardium
tough, nonelastic outer layer, attached by fibrous bands to sternum, central tendon of diaphragm, spine
Serous pericardium (parietal)
lines fibrous pericardium
Serous pericardium (visceral epicardium)
adheres to heart surface
Pericardial cavity space
lubricated-protects against friction as heart beats
how many mL of serous fluid does the pericardial cavity have?
8-10 mL
What is pericardial effusion?
abnormal build up of fluid —-> cardiac tamponade
How do you treat cardiac tamponade?
Cardiocentesis
how many layers does the heart wall have?
3
Epicardium
outermost layer of heart wall. Made up of epithelial cells
What is the main cornary vessels on the heart surface?
epicardium
Myocardium
muscular middle layer. About 3 times thicker on left. Muscles attach to valvular rings
What is the myocardium responsible for?
ejecting blood
Endocardium
inner layer, serous membrane, lines surface of heart chambers
Septum
wall seperating R and L side of heart.
What are the 2 different septums on the heart?
atrial septum and ventricular septum (upper 1/4 is membranes and lower 1/3 is muscle in vent septum)
Right heart function
collects all venous return and propels it into the pulmonary circulation
Left heart function
collect blood returning from pulmonary circulation and propels it into systemic circulation
Right and Left atria
thinner walls than ventricles. most serve as resevoirs for ventricles. seperated by right and left interatrial septum
Right atrium receives blood from what?
superior vena cava, inferior vena cava, coronary sinus and Thebesian veings
Where does the superior vena cava get blood from?
arms and head
Where does the inferior vena cava get blood from?
abdomen and legs
Coronary sinus
very poorly oxygenated blood, comes from coronary circulation
Thebesian veins
venous return from heart muscle that doesnt go to coronary sinus
Left atrium receives blood from how many pulmonary veins?
4
Right and Left ventricles
thicker walls than atria. R. vent 4-5mm and L. vent 12-15 mm. In newborn walls are approx equal
Right ventricle
receives deoxygenated blood from RA, propels blood into pulmonary circulation. generates low pressures
Left ventricle
receives oxygenated blood from LA. and some deoxygenated blood from Thebesian veins and propels blood into systemic circulation
Heart valves
mechanical devices that permit flow in only one direction
AV valves
seperate atria from ventricles
Tricuspid valve
3 leaflets, on right side of heart
Mitral (bidcuspid)
2 leaflets; on left side of heart. thicker and stronger than tricuspid
papillary muscles
arise from endocardial surface. Attach to chordae tendineae
Chordae tendineae
attach to AV valves
Papillary muscles and chordae tendineae are know as what?
anchors
valves open and close how?
passively
Vavles open during what?
diastole (relax)
Vavles close during what?
ventricular systole
AV valves are what?
leakproof
S1
sound of AV valves closing, lubb sound. may also impact of heart against chest wall.
Semilunar valves
each has 3 half moons, dont have papillary muscles, open with vent. contraction, close during diastole, allow undirectional flow from vents. to arteries
S2
sound of semilunar valves closing. dupp sound
Valvular insufficiency
imperfect closing —> causes a leak (regurgitation)
Prolapse
usually due to a torn papillary muscle or chordae
Stenosis
narrowing of valve, due to infection, congenital; leads to backpressure
Damage to cornary arteries can impair what?
myocardial function and electrical conduction
What is the normal coronary blood flow?
225 mL/min (4-5% of CO)
At rest venous PO2 of heart is?
2-30mmHg
CvO2 of heart is what?
8-9 vol % therefor, O2 extraction is very high, and not much extraction reserve if inc. metabolism.
Coronary arteries originate where?
at root of aorta
Inlets
sinus of valsalva; just above aortic cusps.
RCA
rises from anterior sinus of valsalva. passes around AV groove and splits into 2 branches (posterior descending and marginal)
Anastomoses are what?
connections; a good thing
LCA
rises from posterior sinus of Valsalva.
lefts main coronary artery has what 2 branches?
left anterior descending which passes down AV groove and Circumflex which passes posteriorly
Blockages in LCA is called what by doctors?
Widow Maker
Coronary blood flow
most of blood flow is during diastole. Most of coronary venous return is to right atrium
Intra Aortic Balloon Pump
balloon goes up aorta, during diastole it inflates and pumps blood back to coronary artery
As VO2 increases what happens?
coronary arteries dilate
Sympathetic nervous system
Fight or Flight. coronary arteries dilate (Beta effect).
Parasympathetic nervous system
Rest and Digest. coronary arteries indirectly cause constriction
+ chronotropic effect
inc HR
- chronotropic effect
dec HR
- inotropic effect
dec. force of contraction
+ inotropic effect
inc force of contraction
Heart disease of all types cause what number of deaths in US
1/4
Atherosclerosis (ASHD)
systemic disease, most common cause of CAD
Pathology of ASHD
cholesterol deposits under arterial intima, (CRP) ; which is an inflamm. agent that actively pulls cholesterol and macrophages from blood in arterial wall. Areas of deposit are invaded by fibrous tissue and may become calcified.
Plaques can do what?
impede blood flow
Acute coronary occlusion
usually preceded by serious ASHD
Pathology of Acute coronary occlusion
plaque enlarges and breaks wall of intima. blood platelets adhere to rough surfaces therefor a clot is formed and grows until it occludes artery (thrombus) or it breaks and moves downstream (embolus), or arterial spasm (not common)
Angina pectoris
chest pain due to myocardial ischemia. usually a result of ASHD. O2 demand exceeds blood flow to muscles.
Angina pectoris usually occurs when?
with exercise, or emotional distress
Angina pectoris is frequently relieved by what?
rest
Other treatments for angina pectoris
Beta blockers, O2, nitroglycerin
Acute Myocardial infarction (AMI)
occlusion of coronary artery –>muscle death
Symptoms of AMI
(10% of MI’s are silent) chest pain (crushing; may radiate to arm, jaw back), sweating, SOB, pale, nausea, pain may not be relieved by nitro.
Treatment of AMI
rest, O2 (only if evidence of hypoxia), morphine for pain, hypothermia, anti arrhythmics if needed, diuretics if in CHF, thrombolytics, aspirin, angioplasty (stent, laser balloon), coronary artery bypass graft
Morbidity/Mortality of AMI due to?
arrhythmias, dec CO, congestive heart failure, rupture of infacted area