Anastomising

Curriculum timetabling constraints forced me to give up geography early in my school career, around age 13. Nevertheless, for some reason, this word stuck - probably because it feels so good to speak it - and flashed into my mind when I saw this. I looked it up to make sure my memory of its meaning was correct. I didn't expect that to lead back to newborn infants, but I guess I'm easily led in that direction at the moment. We have had a joyous day beginning with one grandson and ending with another; my cup runneth over

My memory was 'anastomising streams', found in the region where a glacier is melting: multiple channels of water flow away from the melting face, but they weave and divert as they flow through the unstable, stony till deposited by the melted ice. As the channels cross, join and rebranch they interchange water and suspended particles between them. Each of these connections between streams is an 'anastomosis'

But I didn't know it is a more general word, applied in several contexts in biology and in medicine, for two separate networks that have an opening between them. The classic example that is quoted is the 'foramen ovale' - another term from schooldays - the opening between the two upper chambers in the heart that is present in a foetus in the womb, but which normally closes after the child is born. Failure to close properly can cause the condition that is over-dramatically described as a 'hole in the heart'

I think the jury is out on whether this picture really shows anastomising stems. For that to be true, they would need to be fused and interchanging sap. To prove that, I would probably need to employ a saw or secateurs - something our kind B&B hosts might not have appreciated

Tangentially, our clever d-i-l (a doctor) explained to me that foetal haemoglobin and normal haemoglobin are different. One of the jobs of a newborn infant, in addition to closing its foramen ovale, is to break down the foetal haemoglobin and replace it with the mature stuff. You think they are just eating and sleeping, but actually they have a lot of work to do