The equine hypothalamus.
Keywords: hypothalamus, equine, adenohypopysis, pars distalis, neurohypophysis, pars nervosa, pituitary
A cross section of a horse (E. caballus) brain, showing the location of some of the vital structures involved in reproduction. It can be seen that the adenohypophysis "wraps" around the neurohypophysis, in this genus ie. the anterior: pituitary gland (also known as the pars distalis or adenohypophysis) is both anterior and posterior! The posterior pituitary gland (also know as the pars nervosa or neurohypophysis) lies centrally. The greyish area separating these two regions is the pars intermedia.
The pineal gland (a source of melatonin) has been artificially colored black in this image.
It is the pars intermedia that produces propiomelanocortin (POMC), a precursor of Melanocyte Stimulating Hormone (α-MSH) and β-endorphin as well some ACTH. Although most ACTH is produced in the anterior pituitary gland (adenohypophysis) is most often the pars intermedia that is affected pathologically, causing equine Cushing's disease. The pars tuberalis is the small upper portion of the pars distalis (adenohypophysis).
The anatomic origin of these hormones is shown in the image below:
Image size: 984 x 774px. Image of original unlabeled histology: copyright Dr Dianne McFarlane, diannem@okstate.edu
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