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What comprises the umbilical cord?
Two umbilical arteries (smaller-deoxygenated) and one umbilical vein (larger-oxygenated).
Where do the two umbilical arteries originate?
Internal iliac arteries.
Where does the umbilical vein flow to, by what mechanism?
Inferior vena cava in liver, bypasses liver by ductus venosus.
How does is oxygenated blood shunted to the fetal brain?
Goes from IVC through foramen ovale into the left atrium -> left ventricle -> carotids -> brain.
How are the lungs bypassed in fetal circulation?
Ductus arteriosus -- shunt from pulmonary trunk to descending aorta (beyond carotid branches).
What makes the umbilical arteries close, what do they become?
- Changes in oxygen tension, thermal and mechanical stimuli
- Medial umbilical ligaments.
How do the umblical vein and ductus venosus close, what do they become?
- Muscle contraction
- Ligamentum teres hepatis
- Ligamentum venosum.
How does the foramen ovale close, what does it become?
- Pressure in left atrium exceed pressure in right atrium
- Fossa ovalis.
What mediates the closing of the ductus arteriosus, what does it become?
- Bradykinin - released from lungs during initial inflation
- Ligamentum arteriosum.
What is the danger of a probe-patent foramen ovale?
Paradox embolism: embolus goes to carotid instead of lungs, after pushing through foramen ovale.
What is the danger of a patent ductus arteriosus?
- Lung overload - left to right shunt
- Indomethacin or other NSAIDs used to treat, surgery as last resort.
Where does formation of vessels begin, at what stage of development?
- Extraembryonic mesoderm
- day 13-15.
What comprises the chorion?
- Cytotrophoblast, syncitiotrophoblast, extraembryonic mesoderm
- Becomes the placenta.
What cells develop into blood vessels and blood cells?
Mesenchymal cells -> angioblasts -> endothelial cells -> blood vessels and cells.
What is most heart failure do to?
Systolic dysfunction: progressive deterioration of myocardial contractile function.
What are the risk factor for diastolic dysfunction?
Older female with DM or HTN.
What is high-output cardiac failure?
Heart failure due to greatly increased metabolic demand for blood in tissue.
What are three mechanisms of adaption to reduced myocardial contractility or increased hemodynamic burden?
- Activation of neurohormonal systems
- Frank-Starling mechanism
- Myocardial structural changes.
What are three neurohormonal adaptive pathways?
- Norepinephrine released by sympathetic nervous system: raises HR, contractility, and vascular resistance
- Activation of renin-angiotensin-aldeosterone system
- Release of ANP.
What does ANP (atrial natriuretic peptide) do?
Vasodilation, naturiuresis, diuresis.
What is the Frank-Starling mechanism, what are the two stages of adaptation?
- Inrcreased heart load (streched fibers) leads to increased force of contraction
- Compensated Heart Failure: Increased contraction is enough to maintain cardiac output
- Decompensated Heart Failure: The heart can no longer propel sufficient blood to meet needs of body.
What are the two types and causes of hypertrophy?
- Concentric hypertrophy: No increase in size of chamber - pressure overload states (HTN, valvular stenosis)
- Eccentric hypertrophy: Volume overload states (valvular regurgitation, abnormal shunts).
What are the four most common causes of Left-sided heart failure?
- Ischemic Heart Disease (IHD)
- Mitral or aortic valve disease
- Primary diseases of the myocardium.
What is the most common cause of right-sided heart failure?
Left-sided heart failure.
What are heart failure cells?
Hemosiderin-containing macrophages in the alveoli.
What is cor pulmonale?
Right-sided heart failure as a result of intrinsic disease of lung parenchyma/vasculature resulting in pulmonary HTN.
What is the tetralogy of Fallot?
- Pulmonary stenosis
- Right heart hypertrophy
- Ventricular septal defect
- Overriding aorta.
What is Eisenmenger syndrome?
Reversal of left to right shunt to right to left shunt, following prolonged shunting that leads to pulmonary HTN.
What is the most common congenital heart defect?
Ventricular septal defect: usually close spontaneously.
What is the most common type of ASD (Atrial septal defect)?
Ostium secundum: the septum secundum fails to grow all the way down and cover the ostium.
What does a Patent ductus arteriosus (PDA) sound like?
Harsh "machinery-like" murmur.
What distinguishes right to left shunts?
Cyanosis at or near the time of birth.
What are two clinical features of long-standing cyanosis?
- Clubbing of fingertips (hypertrophic osteoarthropathy)
What is the most common cause cyanotic congenital heart disease?
Tetralogy of Fallot.
What are the two types of aortic coarctation?
- Preductal (infantile): Usually with PDA, more severe, lower extremity cyanosis
- Postductal (adult): across ligamentum arteriosum, may be asymptomatic.
What collateral circulation develops in postductal coarctation of the aorta?
- Intercostal and internal mammary arteries (enlarged)
- Results in "notching" of the ribs.