R. Munozchapuli et Av. Deandres, ANATOMY AND HISTOLOGY OF THE CEPHALIC ARTERIAL COILINGS IN HAMMERHEADSHARKS (GENUS SPHYRNA), Acta Zoologica, 76(4), 1995, pp. 301-305
Hammerhead sharks (genus Sphyrna) show two large arterial ceilings in
a posteroventral hollow of the orbitary cavity. The posterior is made
up of the hyoid artery which, after giving rise to the stapedial arter
y, enters the chondrocranium to originate the internal carotid and the
cerebral arteries. The efferent pseudobranchial artery forms the ante
rior coiling, gives rise to the ophthalmic artery, enters the orbitary
wall and joins the internal carotid artery. The histological sections
of the arterial ceilings showed the scarcity of smooth muscle cells i
n the tunica media as well as an important collagenic and elastic comp
onent in the arterial wall. Several venous vessels percolate through t
he ceilings. A large amount of small (mean diameter = 73 mu m), spheri
c corpuscles were observed in the connective tissue around the ceiling
s. These corpuscles were also present in the palate and under the skin
of the head of these sharks. They are comprised of spirally-arranged
cells around a bundle of collagen fibres. We hypothesize that their as
sociation with the ceilings could suggest some kind of involvement in
detecting pressure changes in the blood supply to the head.