There is no reason why you could not edit the page and also take part in the GA review; however, sometimes it might be simpler not to work on the page. Nevertheless, it is sensible to form a consensus about images, if you are in doubt.   
The diagramme showing hormones (image 2) is probably more suitable for the calcium metabolism page.   
The anatomical diagramme is quite good, and could augment the a high resolution version of File:Gray1177.png.   
Re File:Gray1177.png; this images in the gallery has poor resolution; however the 1918 PD version in Gray's is available at a much better resolution and can be uploaded over the poor quality image.