To my opinion they are blood vessels. Although judging from a single snapshot can be tricky sometimes, I believe that the second picture is definetely a large vessel (most probably an artery) that has been cut longitudinal. Along the vessel (arterial) wall you can see some tranversly located nuclei from the smooth muscle cells. You can also see two branches of the artery, steming towards the right (the second one downwards is more clearly seen). The free (empty white) space around the artery is the Virchow-Robins perivascular space. This picture is of normal structure.
The first picture also looks like a large vessel to me, that has been cut obligue.
In terms of other vascular structures, you may find a capillary in the first picture at the lower-center part of the picture (longitudinal cut). There are also 2 capillaries in the second picture (one longitudinal and the other transversly cut).
Lastly, the endothelial cells are never flat in the tissue. They are flat only in vitro.
To my opinion they are blood vessels. Although judging from a single snapshot can be tricky sometimes, I believe that the second picture is definetely a large vessel (most probably an artery) that has been cut longitudinal. Along the vessel (arterial) wall you can see some tranversly located nuclei from the smooth muscle cells. You can also see two branches of the artery, steming towards the right (the second one downwards is more clearly seen). The free (empty white) space around the artery is the Virchow-Robins perivascular space. This picture is of normal structure.
The first picture also looks like a large vessel to me, that has been cut obligue.
In terms of other vascular structures, you may find a capillary in the first picture at the lower-center part of the picture (longitudinal cut). There are also 2 capillaries in the second picture (one longitudinal and the other transversly cut).
Lastly, the endothelial cells are never flat in the tissue. They are flat only in vitro.
I agree with blood vessels... although in my experience this artifactual staining can happen if the animal is perfused too rapidly - causing vascular rupture.
I agree with blood vessels because of poor perfusion, and suggest you to repeat your experiment; this time you will try to perfuse well and follow with H&E staining, I think you will see less blood cells.