Category:Sinus

Si"nus, n.; pl. L. Sinus, e. Sinuses. Etym: [l., a bent surface, a Curve, the folds or bosom of a garment, etc., a bay. Cf. Sine, n.]

1. An opening; a hollow; a bending.

2. A bay of the sea; a recess in the shore.

3. (anat. & zoöl.)

Defn: a cavity; a depression. Specifically: (a) a cavity in a bone or other part, either closed or with a narrow Opening. (b) a dilated vessel or canal.

4. (med.)

Defn: a narrow, elongated cavity, in which pus is collected; an Elongated abscess with only a small orifice.

5. (bot.)

Defn: a depression between adjoining lobes.

Note: a sinus may be rounded, as in the leaf of the white oak, or Acute, as in that of the red maple. Pallial sinus. (zoöl.) See under Pallial. -- sinus venosus. Etym: [l., venous dilatation.] (anat.) (a) the Main part of the cavity of the right auricle of the heart in the Higher vertebrates. (b) in the lower vertebrates, a distinct chamber Of the heart formed by the union of the large systematic veins and Opening into the auricle.