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What structure is responsible for the initial division of the atria?
Atrial septum.
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What are the steps of development of the atrial septum?
- Septum primum begins to grow downward towards the atrioventricular septum, closing the ostium primum when it reaches the atrioventricular septum
- Ostium secundum forms as tissue regresses in septum
- Septum secundum grows downward alongside septum primum, covering hole, which becomes foramen ovale.
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What is the most common form of Atrial septal defect (ASD)?
Ostium secundum.
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The bulbus cordis becomes?
Smooth part of ventricles.
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The primitive ventricle becomes?
Trabeculated part of ventricles.
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The primitive atrium becomes?
The trabeculated parts of the atria.
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What are two classic signs of ASD?
- Wide, fixed splitting of S2
- Systolic ejection murmur, heard best in second intercostal space along left sternal border.
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What are the two parts of the interventricular septum?
- Membranous: grows down from AV cushion, obliterating interventricular foramen
- Muscular: grows up from base of primitive ventricle.
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What is the most common congenital heart defect?
Ventricular septal defect (VSD) - membranous.
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What are two classic signs of a VSD?
- Easy fatigability
- Harsh holosystolic murmur heard at LLSB.
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What is the aorticopulmonary septum derived from?
Neural crest cells.
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Right to left shunt results in?
Early cyanosis.
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Persistent truncus arteriosus results from?
- Abnormal migration of neural crest cells, leading to no formation of Aorticopulmonary septum
- Causes right to left shunt and early cyanosis.
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What causes transposition of the great vessels?
- Failure of the spiral development of the Aorticopulmonary septum
- Complete right to left shunt
- early cyanosis.
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What causes tetralogy of Fallot?
Anterior displacement of AP septum.
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What comprises the tetralogy of Fallot?
- Overriding aorta
- pulmonic stenosis
- VSD
- RV hypertrophy.
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Where does fetal erythropoiesis take place?
- Yolk sac wks 3-10
- Liver wks 6-30
- Spleen wks 9-28
- Bone marrow wks 28 - adult
- Young Liver Synthesizes Blood.
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Go through fetal circulation from placenta?
Placenta -> umbilical vein -> ductus venosus -> IVC -> RA -> through Foramen Ovale into LA OR to RV then through Ductus arteriosus into aorta -> systemic circulation -> umbilical arteries branching from Iliac arteries back to placenta.
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What closes the Ductus Arteriosus?
Falling levels of prostaglandins from increased O2 content.
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What drug is used to close a patent ductus arteriosus?
Indomethacin (NSAID).
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What are the post-natal structures of Umbilical vein, umbilical arteries, ductus venosus, ductus arteriosus?
- Umbilical vein: Ligamentum teres hepatis
- Umbilical arteries: Medial umbilical ligaments
- Ductus venosus: Ligamentum venosum
- Ductus arteriosus: ligamentum arteriosum.
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What are the two types of coarctation of the aorta?
- Preductal: PDA, Right to left shunt
- Postductal: results in rib notching.
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What are the 5 conditions leading to Right to left shunts?
- Tetralogy of fallot
- Transposition of great vessels
- Truncus arteriosus
- Total anomalous pulmonary venous return
- Tricuspid atresia.
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What causes late cyanosis?
- Left to right shunt
- Eisenmenger syndrome.
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What is the most commonly occluded coronary artery, second, third?
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Where are slow response AP cells found,fast?
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What makes phase 0 slower in slow AP cells?
Inward conduction of Ca2+ instead of Na+ in phase 0.
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What are the three types of refractory periods?
- Absolute: phase 0 to end of phase 2
- Effective: No conducted AP, slighlty longer than absolute
- Relative: AP can happen with largely increased current, to the end of phase 3)
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What is EF, what is normal?
- EF= Stroke volume/ End-diastolic volume
- Normal: 55%.
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What three things increase Stroke volume (SV)?
- Increased HR
- Increased sympathetic stimulation
- Cardiac glycosides (digoxin).
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What conditions can decrease contractility and SV?
- B-blockade, Ca channel blockers
- Heart Failure
- Peripheral nervous system stimulation
- Acidosis, hypoxia, hypercapnia.
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Sarcomere length is related to?
Preload.
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What are the two ways the body detects changes in Mean arterial pressure (MAP)?
- Baroreceptors: centrally processed, act on autonomic nervous system within minutes
- Kidey: Processed as decreased Extracellular circulating volume, act on Renin-angiotensin-aldosterone system (RAAS), takes longer to take effect.
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What is the site of highest resistance in the CV system?
Arterioles.
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Serum=?
Plasma - clotting factors (e.g. fibrinogen).
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