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Posts Tagged ‘where does bronchial veins drain ?’

One casual question in my class led to this search for an anatomical mystery. When we were discussing  why left atrial oxygen saturation never reaches 100 % ? ,  it was attributed to desaturated  bronchial venous blood  draining  into pulmonary vein.

How does this bronchial vein enter pulmonary venous circulation ? How many bronchial veins are there ? What  anatomical plane it runs   ?

Surprisingly, even in this hi-tech era of academic excess, literature is sparse for this basic anatomical question. It is reported (In Greys anatomy ? ) Bronchial veins are two in number and both drain to Azygos and Hemiazygos veins (systemic) rather than pulmonary veins.

So is our assumption wrong ?

May not be.We realise these are only two visible and named bronchial veins .It is learnt they  probably carry only about 13 %  of bronchial  venous blood to systemic venous circuit.

bronchial venous drainage bronchial circulation

Image showing right and left bronchial veins draining to Azygos and hemiazygos veins.

 

It is assumed , remaining  87 % of  bronchial  venous blood drains to pulmonary  venous  circuit in an invisible  fashion (By unnamed twigs ?) desaturating  the LA blood by about one percent from 100 to 99 %. This is our current understanding. I haven’t come across any specific human  research that quantifies the bronchial venous channels and it saturation . It’s gratifying  to find one study specifically looked answer this question  in sheep study .(Charan H.B  et all Reference 1 )

 

where does bronchial vein drain drainage circulation pulmonary vein saturation

True physiological bronchial venous drainage seems to be  different from anatomical bronchial venous circuits .

 

Clinical implication of bronchial venous circulation.

In physiology it may not be important . However bronchial circulation (both arterial and venous)  can take many anatomical tracts when pulmonary micro vascular bed is structurally and functionally altered as in  COPD,   , pulmonary atresia  with aorto-pulmonary collaterals , congenital left to right shunts,post Fontan  circulation pulmonary AV malformations,lung tumors  etc .

Hemoptysis in acute pulmonary  venous hypertension is thought to be due to rupture of these bronchial veins as elevated pulmonary venous pressure reflect into bronchial veins  (As in mitral stenois and other conditions. )  This again would vouch for bronchial veins draining to pulmonary veins.

Final message

As on today , it can be concluded bronchial vein drainage goes both systemic and pulmonary venous circuit.Bulk of them appear to end in  pulmonary veins though clear anatomical evidence is lacking.

Post-ample

Exploring human anatomy appear a  grossly unfinished agenda even today, especially the micro and histo-anatomy. Teachers of basic sciences  should impress upon youngsters entering the medical school to pursue translational  research relevant to specific clinical  problems.

Students  may contact   <drsvenkatesans@yahoo.co.in> for specific areas of clinical cardiac anatomy topics that still requires answers.

Reference

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