After doing some existing background research I am confused as to exactly what, in an unfertilised chicken egg's yolk, offers what we intake as 'Vitamin A' upon eating it.
Plants typically produce caretenoids like beta-carotene, alpha-carotene, or beta-cryptoxanthin which the human body then converts into, if I understand correctly, other compounds like 'retinol' and that is what we make use of after this conversion.
I assume that chickens undergo a similar process of bioassimilating the original, (probably mostly plant-based) sources, into a usable one such as retinol (which I assume makes it way into the egg yolk), but I also read that possibly (Vitamin A applicable) caretenoids are also present in the yolk, not unlike original plant caretenoids.
What chemicals exactly are in a chicken's egg that we metabolise into (or directly intake as) Vitamin A then - can this be demystified? Is there more than one relevant compound in egg yolk, or is it only retinol?