(anatomy) A muscle arising from the transverse processes of the fourth to sixth cervical vertebrae, inserting on the outer surface of the second rib, and functioning to raise the second rib and to bend and slightly rotate the neck.

(anatomy) An artery that arises by the terminal forking of the basilar artery where it forms the posterior portion of the circle of Willis and passes on to supply the lower surfaces of the temporal and occipital lobes.

(anatomy) Either of two arteries that occur one on each side of the circle of Willis and connect an internal carotid artery with a posterior cerebral artery.

(anatomy) An artery that usually branches from the vertebral artery below its junction with the contralateral vertebral artery to form the basilar artery and that supplies much of the medulla oblongata, the inferior portion of the cerebellum, and part of the floor of the fourth ventricle.

(anatomy) Either of two arteries of which one arises from a vertebral artery on each side below the level at which the corresponding branch of the anterior spinal artery arises and which descend on the posterior lateral surface of the spinal cord along a line passing close to the entrance of the dorsal roots to the spinal cord.

(anatomy) A branch of the maxillary artery that supplies the upper molar and bicuspid teeth.

(anatomy) A small branch of the external carotid artery that supplies or gives off branches supplying the back of the ear and the adjacent region of the scalp, the middle ear, tympanic membrane, and mastoid cells.

(anatomy) Either of usually two arteries of which one arises from the ophthalmic artery on each side of the optic nerve, passes forward along the optic nerve accompanying the short posterior ciliary arteries, pierces the sclera passing forward on the same side of the eyeball between the sclera and the choroid to the ciliary muscle, and at the junction of the ciliary process and the iris divides into upper and lower branches which anastomose with the branches of the contralateral artery to form a ring of arteries around the iris.

(anatomy) Any of 6 to 10 arteries that arise from the ophthalmic artery or its branches, pass to the posterior part of the eyeball while surrounding the optic nerve, and enter or divide into branches entering the sclera to supply the choroid and the ciliary processes.

(anatomy) Synonym of choana.