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Questions and Answers
What is the characteristic feature of the musculi pectinati in the right atrial appendage?
What is the characteristic feature of the musculi pectinati in the right atrial appendage?
- They insert into the crista terminalis at an oblique angle.
- They run all the way round the atrio-ventricular junction. (correct)
- They are absent in the right atrial appendage.
- They are confined within the appendage.
What is the typical bronchial anatomy in right isomerism?
What is the typical bronchial anatomy in right isomerism?
- Hyparterial bronchi with three-lobed lungs.
- Eparterial bronchi with three-lobed lungs. (correct)
- Eparterial bronchi with bilobed lungs.
- Hyparterial bronchi with four-lobed lungs.
What is the term used to describe the arrangement of organs in isomerism?
What is the term used to describe the arrangement of organs in isomerism?
- Isomeric situs.
- Situs solitus.
- Visceral heterotaxy. (correct)
- Lateralization.
What is the characteristic feature of the left atrial appendage?
What is the characteristic feature of the left atrial appendage?
What is the spleen anatomy associated with left isomerism?
What is the spleen anatomy associated with left isomerism?
What is a major limitation of the traditional division of complex malformations with jumbled-up bodily organs into 'polysplenia' or 'asplenia' subsets?
What is a major limitation of the traditional division of complex malformations with jumbled-up bodily organs into 'polysplenia' or 'asplenia' subsets?
What is the significance of a ratio between the lengths of the two main bronchi that is less than 1.6?
What is the significance of a ratio between the lengths of the two main bronchi that is less than 1.6?
What is the usual arrangement of the descending aorta and inferior caval vein in the normal atrial situs?
What is the usual arrangement of the descending aorta and inferior caval vein in the normal atrial situs?
What is the significance of discordance between bronchial and atrial situs?
What is the significance of discordance between bronchial and atrial situs?
What is the method of distinction between lateralized and isomeric situs that does not rely on autopsy?
What is the method of distinction between lateralized and isomeric situs that does not rely on autopsy?
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Study Notes
Right Atrial Appendage
- Broad and blunt, extending from the superior vena cava to the inferior vena cava
- Contains parallel trabeculations (musculi pectinati) that run around the atrio-ventricular junction and insert into the crista terminalis at right angles
Left Atrial Appendage
- Narrow and pointed, often resembling a crooked finger
- Musculi pectinati are confined within the appendage, making the left atrial vestibule smooth
Lateralization and Isomerism
- Presence of a morphologically left appendage on one side and a morphologically right appendage on the other constitutes lateralization
- Can be seen in situs solitus or situs inversus
- Isomerism occurs when there is duplication of morphologically right or left structures on each side of the body
- Right isomerism is associated with asplenia, while left isomerism is usually accompanied by polysplenia
Heart and Lung Structure
- In right isomerism, both lungs tend to have three lobes and are fed by eparterial bronchi
- In left isomerism, both lungs tend to be bilobed and have hyparterial bronchi
Diagnosis
- Atrial appendages provide the best guide to isomerism within the heart
- Musculi pectinati encircling both atrio-ventricular junctions indicate right isomerism
- Bilaterally smooth vestibules indicate left isomerism
- A ratio between the lengths of the two main bronchi less than 1.6 indicates isomerism, while a ratio higher than 1.6 indicates lateralization
- Cross-sectional echocardiographic scanning of the descending aorta and inferior caval vein can also accurately infer atrial arrangement
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