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What structure is responsible for the initial division of the atria?
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.
What is the most common form of Atrial septal defect (ASD)?
The bulbus cordis becomes?
Smooth part of ventricles.
The primitive ventricle becomes?
Trabeculated part of ventricles.
The primitive atrium becomes?
The trabeculated parts of the atria.
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.
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.
What is the most common congenital heart defect?
Ventricular septal defect (VSD) - membranous.
What are two classic signs of a VSD?
- Easy fatigability
- Harsh holosystolic murmur heard at LLSB.
What is the aorticopulmonary septum derived from?
Neural crest cells.
Right to left shunt results in?
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.
What causes transposition of the great vessels?
- Failure of the spiral development of the Aorticopulmonary septum
- Complete right to left shunt
- early cyanosis.
What causes tetralogy of Fallot?
Anterior displacement of AP septum.
What comprises the tetralogy of Fallot?
- Overriding aorta
- pulmonic stenosis
- RV hypertrophy.
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.
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.
What closes the Ductus Arteriosus?
Falling levels of prostaglandins from increased O2 content.
What drug is used to close a patent ductus arteriosus?
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.
What are the two types of coarctation of the aorta?
- Preductal: PDA, Right to left shunt
- Postductal: results in rib notching.
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.
What causes late cyanosis?
- Left to right shunt
- Eisenmenger syndrome.
What is the most commonly occluded coronary artery, second, third?
Where are slow response AP cells found,fast?
What makes phase 0 slower in slow AP cells?
Inward conduction of Ca2+ instead of Na+ in phase 0.
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)
What is EF, what is normal?
- EF= Stroke volume/ End-diastolic volume
- Normal: 55%.
What three things increase Stroke volume (SV)?
- Increased HR
- Increased sympathetic stimulation
- Cardiac glycosides (digoxin).
What conditions can decrease contractility and SV?
- B-blockade, Ca channel blockers
- Heart Failure
- Peripheral nervous system stimulation
- Acidosis, hypoxia, hypercapnia.
Sarcomere length is related to?
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.
What is the site of highest resistance in the CV system?
Plasma - clotting factors (e.g. fibrinogen).
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