Sinus
# Sinus

Sinus may refer to:

## History

* a sac in front of body worn into a toga, in the typical style of wearing it

## Anatomy

* Sinus (anatomy), a sac or cavity in any organ or tissue
   * Paranasal sinuses, air cavities in the cranial bones, especially those near the nose, including:
      * Maxillary sinus, is the largest of the paranasal sinuses, under the eyes, in the maxillary bones
      * Frontal sinus, superior to the eyes, in the frontal bone, which forms the hard part of the forehead
      * Ethmoid sinus, formed from several discrete air cells within the ethmoid bone between the eyes and under the nose
      * Sphenoidal sinus, in the sphenoid bone at the center of the skull base under the pituitary gland
   * Anal sinuses, the furrows which separate the columns in the rectum
   * Dural venous sinuses, venous channels found between layers of dura mater in the brain
* Sinus (botany), a space or indentation, usually on a leaf

### Heart

* Sinus node, a structure in the superior part of the right atrium
* Sinus rhythm, normal beating on an ECG
* Coronary sinus, a vein collecting blood from the heart
* Sinus venosus, a cavity in the heart of embryos
* Sinus venarum, a part of the wall of the right atrium in adults, developed from the sinus venosus

## Other uses

* Sinus (Chalcidice), a town of ancient Chalcidice, Greece
* Sinus, gulf or bay in Latin, used in numerous toponyms in ancient writing (e.g., Sinus Magnus, Sinus Flanaticus, etc.)
* Sine, a trigonometric math function (Latin sinus)
