Last week we asked you to identify the pigment (orange arrows) and elliptical material (black arrows) in this image.
This tissue is from a foal which was born dead. The pigment is meconium – the faeces passed by a foetus when it is in the uterus. The elliptical material are scrolled skin cells, called squames, which are shed by the foetus during pregnancy. They are refractile, as can be seen in the next image of the same area of lung using polarised light.
The pink feathery material is protein rich fluid (amniotic fluid). These findings are consistent with aspiration of amniotic fluid by the foal because of distress, drawing meconium, dead skin cells and aminiotic fluid deep into the lungs as it gasps. This might be due to a twisted umbilical cord, for example.