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26 Cards in this Set
- Front
- Back
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Whatroles do the cardinal veins play in early embryogenesis? |
- Constitutethe main venous drainage system of the embryo. - Two veins,anterior and posterior draining the cranial and caudal parts of embryo. +form common cardinal veins: return poorly oxygenated blood from the body ofembryo to the heart. |
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What venous structures inthe adult derive from the cardinal veins? |
- Anterior veins form the adultsderivatives : +The left brachiocephalic vein. +The superior vena cava. - Posterior veins form the adultsderivatives : +Azygos vein. +The common iliac veins. |
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When is the CVS in the embryo developping? |
The cardiovascular system (CVS) is the first system tofunction in the embryo due to metabolic demands The early development of the CVS is necessary since thegrowing embryo cannot satisfy its nutrition demands bydiffusion alone Heart begins to beat at 22-23 days after fertilisation Primordial heart and vascular system appear in middle ofthird week of embryonic development |
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Three paired veins drain into the tubular heart at 4 weeks: |
- Vitelline, umbilical and common cardinal veins. |
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The vitelline veins |
- drain away de-oxygenated blood from the yolk sac toward the embryonic heart. - leaving the yolk sac enter thesinus venosus of primordial heart - The right vein will persist and formhepatic veins within the developing liver. - The hepatic portal vein develops from their network around the developingduodenum |
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Three vitelline arteriesremain in adult: |
celiac trunk (foregut) Superior mesenteric artery (midgut) Inferior mesenteric artery (hindgut) |
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The umbilical veins |
- carry oxygenated blood from primordial placenta (chorionic sac) to the embryonic heart. - Right vein and cranial part of left vein (between liver and primordialheart) degenerate. - Left vein becomes single vein that carries O2rich blood fromplacenta to embryonic heart. - connects to the inferiorvena cava via a shunt in the liver called theductus venosus |
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The common cardinal veins |
- drain de-oxygenated blood away from the embryo tissue to the heart |
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Explain the fate of Umbilical Arteries: |
Umbilical arteries passthrough umbilical cord tojoin vessels of chorion(outermost membrane) Carry oxygen poor fetalblood to placenta (thevillous part of the chorion) Proximal parts becomeinternal iliac arteries Distal part become medialumbilical ligaments |
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Divided into rightand left atria by formation, modification and fusion of the two septa: |
the septum primun and septum secundum |
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Describe the Septumprimun: |
- Grows towards the fusing endocardial cushions from the roof of the primordial atrium, partially dividing theatrium into right and left halves. - Gives rise to foramen primun allowing shunting of oxygenated blood fromright to left. Disappear by apoptosis and form another opening foramen secundum ensuring theshunt of oxygenated blood. |
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Septum secundum: |
- Grows from the muscular ventrocranial wall of the atrium, adjacent to theright of the septum primun. - Grows during the fifth and sixth weeks,gradually overlapping the foramensecundum. - Forms incomplete partition between the atria: the oval foramen. |
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How does the partitioningof the atria occur? |
1. Divided into right and left atria by formation,modification and fusion of the two septa, theseptum primun and septum secundum. 2. Before birth: Oval foramen: allows most of the oxygenated blood entering the right atrium from the IVC to pass into the left atrium.It prevents the passageof blood in the opposite direction. 3. After birth: Oval foramen: closes due to higher pressure in the left atrium than in the right atrium. 3 months the valve fuses with the septum secundum, forming the oval fossa. |
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Describe how the pulmonarytrunk and aorta develop from the truncus arteriosus. |
The tubular heart elongates and develops alternate dilations and constrictions: - The bulbus cordis (composed of truncusarterious, conus arterious, conus cordis). - Ventricle, atrium and sinus venosis. The growth of heart tube results from the addition of cells cardiomyocytes that differentiate to mesoderm at the dorsal wall of the pericardium. The tubular truncuns arterious is continuous cranially with the aortic sac, from which the pharyngeal arch arteries arise. Week 5: Bulbus cordis: results in formation of bulbar ridges (similar in the truncus arteriosus). The bulbar and truncal ridges are derived mainly from the neural crest mesenchyme. Bulbar and truncal ridges undergo 180 degree spiralling = results in formation of a spiral aorticopulmonary septum when the ridge fuse. - This septum divids the bulbus cordis and thetruncus arteriosus into two arterial channels, the aorta and the pulmonary trunk. Because of the spiralling the pulmonary trunk twists around the ascending aorta. |
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Describe how the bloodflow in the fetus changes in the neonate. |
- The fetal cardiovascular system is designed toserve prenatal needs. - Good respiration in the neonatal period (1-28 days) is dependent on normal circulatory changes occurring at birth, whichresults in oxygenation of the blood occurring in the lungs when fetal bloodflow through placenta ceases. - Before birth the lungs do not provide gasexchange and the pulmonary vessels are vasoconstricted. - Highly oxygenated, nutrient rich blood returns under high pressure from the placenta in the umbilical vein. |
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Explain the Neonatal circulation: |
1. At birth, the circulation of blood through the placenta ceases and the infant’s lungs expand and begin to function. 2. Which in turn increase pressure in left atrium due to increase of pulmonary blood flow that closes foramen ovale. 3. Ductus arteriosus constricts at birth to form ligamentum arteriosum. Oxygen is the most important factor in controlling the closure of DA. 4. The umbilical arteries constrict at birth, preventing loss of the neonate’s blood. |
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At birth, the circulation of blood through the placenta ceases and the infant’s lungs expand and begin to function. Explain the major change during this period: |
- Foramen ovale, ductus arteriosus, ductusvenosus and umbilical vessels no longer needed, as soon as the fetus is born. - Ductus venosus constricts and all the bloodentering in the liver passes through the hepatic sinusoids, combined withocclusion of the placental circulation, causes an immediate decrease in bloodpressure in the IVC and right atrium. |
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The umbilical arteries constrict at birth, preventing loss of the neonate’s blood: |
- Distal ends of umbilical arteries become medialumbilical ligaments of bladder. - Proximal ends of umbilical arteries form thesuperior vesical arteries of bladder. - Umbilical vein eventually closes to becomeligamentum teres (round ligament of liver)- - Ductus venosus (passing through liver) becomesligamentum venosum. |
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what is the Atrial septal defect? |
More in female thanmale. - Common form is apatent oval foramen. - Small isolated patentforamen is of hemodynamic significance. - A probe contentforamen: present 25% of people. Can be passed from one atrium to another. Results from incomplete adhesion between the flap like of the oval foramen andthe septum secumdum after the birth. |
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What are the four types of atrial septal defect? |
- Ostium secumdum defect - Endocardial cushion defect with a foramen primum defect. - Sinous venous defect. - Common atrium |
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Give the definition of Persistenttruncus arteriosus: |
- results from failureof the truncal ridges and aorticopulmonary septum to develop normally, and todivide the TA into the aorta and pulmonary trunk. |
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Define: Transpositionof great arteries |
- most common cause ofcyanotic heart disease in neonates. Result from failure of the conus arteriousto develop normally during incorporation of the bulbus cordis into theventricles. |
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Unequaldivision of truncus arteriosus: |
results when the partitioning of the TA superior to the valves is unequal, producing one large great artery and one small one. The aorticopulmonary septum is not aligned with the IV septum, and a VSD results. |
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Aorticstenosis: |
edges of the valvesusually fused to form a dome with a narrow opening. Can be an acquired defect. It causes extra work for the heart and results in hypertrophy (enlargement) ofthe left ventricle and abnormal heart sounds. |
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Aorticatresia: |
band of fibrous tissue inferior to the aortic valve. Results from the persistence of tissue that normally degenerates as the valve forms. |
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Patentductus arteriosus: |
functional closure ofthe PDA occurs soon after birth. |
