First Aid Flashcards
Where does fetal erythropoiesis occur?
Yolk sac | 3-8 wks
Liver | 6 wks - birth
Spleen | 10-28 wks
Bone Marrow | 18 wks to adult
What is fetal hemoglobin composed of?
α2 γ2
What is adult hemoglobin composed of?
α2 β2
Why does HbF have a higher affinity for oxygen?
Less avid binding of 2,3-BPG (left shift)
Where in the fetal circulation is there the highest concentration of O2
Umbilical vein
Starting in the umbilical vein, trace the flow of O2
Umbilical vein → Ductus venosus → IVC → RA → foramen ovale → LA → Aorta → Body
In the fetal circulation, deoxygenated blood flowing into the SVC goes where?
RA→ RV → main PA → patent ductus arteriosus → descending aorta
What causes the foramen ovale to close?
1st breath → ↓resistance in pulmonary vasculature → LAP>RAP
What causes the ductus arteriosus to close?
↑O2 (respiration) + ↓ prostaglandins (placental separation)
What drug can be used to close a PDA? To keep it open?
Indomethacin PGE (E1 and E2)
What is the fetal structure that turns into the ligamentum teres hepatis, contained in the falciform ligament
Umbilical vein
What do the umbilical arteries become?
Medial umbilical ligaments
What does the notochord become?
Nucleus pulposus of intervertebral disc
What do the ductus arteriosus and ductus venosus become?
Ligamentum arteriosum and venosum
What does the foramen ovale become?
Fossa ovalis
What does the allantois become
Urachus-median umbilical ligament
What supplies the SA and AV nodes?
RCA
What determines whether a person has Right or Left dominant circulation? Which is more common?
Right-dominant = PDA arises from RCA Left-dominant = PDA arises from LCX 85% = right dominant
When does coronary blood flow peak?
Early Diastole
What symptoms can enlargement of the L atrium cause?
Dysphagia - presses on esophagus
Hoarseness - compression of L recurrent laryngeal n. (CNX)
How do you compensate CO during early exercise? Late exercise?
↑ HR and SV
↑ HR only - SV plateaus
Which phase is decreased w/ ↑ HR?
Diastole - decreased filling time, ↓ preload
What things affect Mean Arterial Pressure (MAP)?
CO * TPR
What things affect Stroke Volume?
SV CAP - SV increases w/
Contractility ↑
Afterload ↓
Preload ↑
How do you increase contractility?
↑ intracellular Ca
- Catecholamines: ↑activity of Ca pump in SR
- ↓extracellular Na: ↓ activity of Na/Ca exchange
- Digitalis: blocks Na/K pump directly - indirectly blocks Na/Ca exchange
Which way does the Na/Ca pump work?
Ca in efflux (leaving) - mostly
Uses Na gradient in
How do you decrease contractility?
- β1-blockade (↓cAMP)
- Non-dihydropyridine Ca channel blockers - diltiazem & verapamil
- HF w/ systolic dysfunction
- Acidosis
- Hypoxia/Hypercapnea
What does preload depend on?
Ventricular EDV - venous tone and circulating blood volume
What class of drugs will decrease preload?
Venodilators - nitroglycerin
What does afterload depend on?
MAP
How does the heart respond to ↑MAP?
LV hypertrophy
Wall tension = (Pr)/(2wall thickness)
What 2 classes of drugs will decrease afterload?
Vasodilators - hydralazine
ACEi/ARBs - ↓preload & afterload
How is ejection fraction calculated? What is a normal EF? When is it decreased?
SV/EDV
Normal ≥ 55%
Systolic HF
What does the starling curve show?
LVEDV x SV (or CO)
That changes in inotropy can cause changes in SV outside of preload
What is R directly proportional to? Inversely proportional?
- Viscosity and vessel length
2. r^4
What accounts for most of the TPR?
Arterioles
What does viscosity depend on? When might it be elevated?
Hematocrit
Polycythemia, hyperproteinemic states (multiple myeloma), aHereditary spherocytosis
When does S3 occur?
Early in diastole - ↑filling pressure
Mitral regurg, CHF, dilated ventricles
Normal in children and pregnant women
When does S4 occur?
End of diastole - atrial kick
High atrial pressure, ventricular hypertrophy
What does the a wave represent?
Atrial contraction
What does the c wave represent?
RV contraction - closed tricuspid valve bulges into atrium
What does the x descent represent?
Atrial relaxation - absent in tricuspid regurg
What does the v wave represent?
↑ RA pressure due to filling against closed TV
What does the y descent represent?
Blood flow from RA to RV
What is normal splitting?
A2 and P2 get farther apart w/ inspiration
↓intrathoracic pressure → ↑RV SV → ↑ RV ejection time → delayed closure of the pulmonic valve
When would you hear wide splitting?
Conditions that delay RV emptying
Pulmonic stenosis, RBB block
When would you hear fixed splitting?
ASD: L→R shunt → ↑RA and RV volumes
Pulmonic closure is delayed regardless of breath
When do you hear paradoxical splitting?
Conditions that delay LV emptying
Aortic stenosis, LBB block
P2 gets closer to A2 on inspiration (paradox)
What murmurs are heard during systole?
A/P stenosis
M/T regurgitation
VSD
What murmurs are heard during diastole?
A/P regurgitation
M/T stenosis
What murmur is holosystolic, high-pitched “blowing”
M/T regurgitation
How could you tell the difference between Mitral and Tricuspid Regurgitation?
Where you hear the murmur
Mitral: enhanced w/ squatting/hand grip (↑TPR)
Tricuspid: enhanced w/ inspiration (↑RA return)
What murmur is a crescendo-decrescendo systolic ejection murmur?
Aortic Stenosis - syncope, angina, dyspnea on exertion
What murmur is a holosystolic, harsh-sounding murmur?
VSD - tricuspid area
enhanced w/ handgrip
What leads show ST elevation in a lateral infarction
I, aVL, V5, V6
What leads show ST elevation in a inferior (RCA) infarction
II, III, avF
Recip: I, aVL
What leads show ST elevation in a anterior (LAD) infarction?
V1-V4
What does a high pitched “blowing” early diastolic decrescendo murmur indicate? What other symptoms are seen?
Aortic Regurgitation
Bounding pulses, head bobbing
What are causes of aortic regurgitation? (4)
Aortic root dilatation, bicuspid aortic valve, endocarditis, rheumatic fever
What does a late systolic crescendo murmur w/ midsystolic click indicate?
Mitral valve prolapse - click due to sudden tensing of chordae tendineae
What does a delayed rumbling, late diastolic murmur, following an opening snap indicate?
Mitral Stenosis
What does a continuous machine-like murmur, loudest at S2 indicate? What can cause this?
PDA
Congenital rubella or prematurity
ANP
Released from atrial myocytes in response to ↑BV and ↑atrial pressure
Vasodilation, ↓Na reabsorption, promotes diuresis (cGMP)
BNP
Released from ventricular myocytes in response to ↑tension
Used to diagnose HF
What baroreceptor responds to both ↑BP and ↓BP?
Carotid sinus (IX) - Aortic arch (X) only responds to ↑BP
Which chemoreceptors respond to ↓PO2, ↓pH and ↑PCO2?
Peripheral chemoreceptors - central don’t respond to PO2