Transcript Cardiac A&P

Heart & Neck Vessels—A&P
Taylor, ch 25
Jensen ch 17
Anatomy of the Heart
Coronary Arteries
Coronary Circulation
• Coronary arteries are first branches of aorta
at sinuses of Valsalva.
• Provides blood supply to heart during
diastole (during resting phase or in between
beats).
• Has left and right coronary branches
Left Coronary Artery
• 2 branches:
– Left circumflex—goes to left atrium, lateral
and posterior ventricles
– Left anterior descending (“widow maker”)—
goes to anterior and apex of LV, anterior
septum, bundle of His, right and left bundle
branches
Right Coronary Artery & Venous
Drainage
• Goes to RA, RV, SA and AV nodes,
posterior and septum
• Venous drainage is done by coronary
sinus, cardiac veins, and thesbian veins
Physiology of the Heart
Blood Flow
• Realize that blood flow within the heart is
bilateral
• Following one deoxygenated RBC:
– From body—IVC—RA—tricuspic valve—
RV—pulmonic valve—pulmonary artery—
lungs—pulmonary vein—LA—mitral valve—
LV—aortic valve—aorta—to body
Direction of Blood Flow
Cardiac Cycle
• Systole—ventricular contraction—corresponds to
“lub” sound which is closure of AV valves. This
is the S1 part of cycle.
• Diastole—relaxation phase and atrial contraction-corresponds to “dub” sound which is closure of
semilunar valves. This is the S2 part of cycle.
• S3 is aortic valve closing just before pulmonic
So…to put it together….
• Blood from the vena cava and pulmonary artery
flows into both atria when ventricles are relaxed
and AV (tricuspid and mitral) valves are open.
• Atria have higher pressure than ventricles so blood
pours into ventricles (passive filling).
• When 75% of blood is in ventricles, other 25% is
pushed in by “atrial kick” (active filling).
• When ventricles are full, the stretch on the
chordae tendinae cause the AV valves to snap shut
causing the first heart sound (S1).
And then………
• Pressure in ventricles is greater than pressure in
great vessels (pulmonary artery and aorta) so…
• Milliseconds later, the semilunar valves (pulmonic
and aortic) open, and the ventricles contract.
• Blood is forced thru the great vessels.
• When pressure is low in ventricles, semilunar
valves snap shut, causing the second heart sound
(S2).
Preload & Afterload
• Preload—amount of
stretch in ventricles at
end of diastole
• Afterload—resistance
in great vessels against
which ventricles must
pump blood into
circulation
Cardiac Output
• Cardiac output = Stroke Volume x Heart Rate
• Stroke volume 70 mL/beat; 4-7 L/min; exercise 20
mL/min. SV is determined by preload, afterload,
and contractility
• Starling’s Law—greater the stretch, the stronger
the contraction
• Heart rate is controlled by ANS, CNS, and
baroreceptors in heart
• Ejection fraction is % of blood ejected by
ventricles in one contraction
Chemical Conduction
• Contraction depends on exchange of ions
across the myocardial cell membrane—
Na+, K+, Ca++
• Polarization—cell is ready to contract with
ions in place
• Depolarization—ventricular contraction
• Repolarization—resting phase during which
ions are moving back to polarization state
Cardiac Conduction
• Depolarization causes the myocardium to
contract
• Sodium ions enter cells altering
permeability of cell membrane to calcium
• Calcium enters cells and is released from
intracellular stores
• Repolarization occurs as cells return to
baseline or resting state resulting in
relaxation of muscle
Conduction Pathway
Conduction and the ECG
Conduction & the ECG
ECG Interpretation
• P wave represents atrial depolarization
• QRS complex represents ventricular
depolarization
• T wave represents ventricular
repolarization
• U wave may represent repolarization
of Purkinje fibers. May also be seen in
hypokalemia, hypertension, or heart
disease
• PR interval normal range is 0.12-0.20
seconds
• ST segment is identified as isoelectric, or
above or below isoelectric line
• QT interval normal range is 0.32-0.40
seconds
• TP interval is isoelectric period
• PP interval signifies atrial rhythm and rate
• RR interval signifies ventricular rate and
rhythm
Neck Vessels
• Carotid artery:
–
–
–
–
–
Transports blood to brain
2nd branch of aorta
Pulsations are visible
Palpated between thyroid cartilage and SCM
Coincides with apical pulse
Neck Vessels cont’d
• Jugular veins:
– Drain head and neck
– Return blood to heart via superior vena cava
(SVC)
– Internal is visible in sternal notch in supine
position
– External may be visible superior to clavicle, but
is difficult to see unless pt is in heart failure
Developmental Differences:
Fetal Circulation Review
• 3 anatomical differences from adult :
– Foramen ovale—closes within 1 hr after birth
– Ductus arteriosus—closes within 12-15 hrs
– Ductus venosus
• Blood flow differences:
– Returning blood enters RA—60% goes thru foramen
ovale to LA to LV, then to aorta
– 40% goes to RV into PA, but only 10% goes to lungs.
30% goes to aorta
Differences: Infants and
Children
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PMI at 4th ICS, MCL until 7 yrs of age
Sinus arrhythmia throughout childhood
Split S2
Faster pulse: 160 to 90
Lower BP: 70/40 to 110/70
Differences: Older Adults
• SBP increases 40 mm d/t arterial wall
changes causing slight enlargement of LV.
No change in DBP.
• More likely to have arrhythmias, murmurs,
extra sounds, bruits, activity intolerance,
atypical MI sx, and orthostatic BP
Cultural Differences
• All CV risk factors are higher among
Blacks and Hispanics and lower in Asians
and Pacific Islanders.
• Incidence of HD is higher in both male and
female African Americans than in other
groups and Latino women have higher
incidence than white women.