sigmoid sulcus

{{Short description|Fold in the back of the temporal bone}}

{{Infobox bone

| Name = Sigmoid sulcus

| Latin = sulcus sinus sigmoidei ossis temporalis

| Image = Gray138.png

| Caption = Left temporal bone. Inner surface. (Sigmoid sulcus visible at center left.)

| Image2 = Gray193.png

| Caption2 = Base of the skull. Upper surface. (Sigmoid sulcus not labeled, but is visible near mastoid foramen.)

}}

The inner surface of the mastoid portion of the temporal bone presents a deep, curved groove, the sigmoid sulcus, which lodges part of the transverse sinus; in it may be seen the opening of the mastoid foramen.