Anatomy of Atrial Appendages

What is the characteristic feature of the musculi pectinati in the right atrial appendage?

What is the typical bronchial anatomy in right isomerism?

What is the term used to describe the arrangement of organs in isomerism?

What is the characteristic feature of the left atrial appendage?

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 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 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?

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

This quiz covers the structure and characteristics of the right and left atrial appendages, including their shape, trabeculations, and musculi pectinati.