On the A. malaris of the Common Squirrel Monkey (Saimiri sciureus)

Abstract

Detailed observations were made of the a. malaris in 11 adult common squirrel monkeys (Saimiri sciureus) utilizing the plastic injection method. The malar artery was well-developed in all 21 examples observed and arose medially from the infraorbital artery proximal to the entrance of the infraorbital canal and lateral to the obliquus inferior muscle. The a. malaris passed superomedially outside the periorbita on the orbital surface of the maxilla and curved medially in front of the muscle, where it gave rise to the infraorbital nerve, the periosteal, the inferior oblique muscular and the infraorbital marginal branches. However, these branches arose directly from the infraorbital artery in many cases. The malar artery ascended in the lower eyelid up to the bottom of the lacrimal sac, where it gave rise to the third palpebral branch and the medial inferior palpebral artery. This artery did not anastomose with peripheral branches of the supraorbital artery. The malar artery continued to pass superomedially behind the lacrimal sac and gave off the nasolacrimal canal and the lacrimal sac branches. However, the former arose in common with the latter in many cases. The malar artery finally ascended behind the medial palpebral ligament after giving off the dorsal nasal branch and the medial superior palpebral artery at the superior end of the lacrimal sac. Its main stream formed a strong communication with the dorsal nasal artery of the supraorbital artery. This communication in an arc was characteristic in the common squirrel monkey. The medial inferior and superior palpebral arteries were well-developed in all examples and formed distinct, inferior and superior palpebral arterial arches by anastomosing with the lateral fellows of the lacrimal, respectively. A large arterial ring surrounding the upper tarsus was constructed from the superior palpebral arterial arch, branches of the lateral superior palpebral artery and the palpebral branch of the supraorbital artery.