Data from: Avian cephalic vascular anatomy, sites of thermal exchange, and the rete ophthalmicum

The general anatomy of avian cephalic blood vessels is well known and
there are published details of their role in physiological
thermoregulation. Unfortunately, the finer details of vascular pathways to
and from sites of thermal exchange are not well known. Additionally, the
role of the rete ophthalmicum (RO), a vascular heat exchanger in the
temporal region, has been investigated in terms of brain temperature
regulation, yet only the arteries have received substantial attention.
Without anatomical details of both the arterial and venous pathways, the
role of blood vessels in physiological thermoregulation is incomplete.
Cephalic vascular anatomy of multiple avian taxa was investigated using a
differential-contrast, dual-vascular injection technique and
high-resolution X-ray microcomputed tomography. Sites of thermal exchange
(oral, nasal, and orbital regions) and the RO were given special attention
due to their known roles in cephalic thermoregulation. Blood vessels to
and from sites of thermal exchange were investigated to detect conserved
vascular patterns and their ability to deliver cooled blood to the RO and
dural venous sinus. Sites of thermal exchange were supplied by arteries
directly and through collateral pathways. Veins were found to offer
multiple pathways that could influence the temperature of neurosensory
tissues, as well as pathways that would bypass neurosensory tissues. These
results question the paradigm that arterial blood from the RO is the
primary method of brain cooling in birds. A shift in the primary role of
the RO from brain cooling to regulating and maintaining the temperature of
the avian eye should be further investigated.