17 - diploic veins and diploic bones

Recently a question was asked in the DNB june 2008 exam about the diploic bones , which was like this :

q. which of the following is a diploic bone ?

a.zygomatic

b.ethmoid

c. maxilla

d. frontal

answer : d . frontal bone.

The diploic veins are found in the skull, and drain the diploic space. This is found in the bones of the vault of the skull, and is the marrow-containing area of cancellous bone between the inner and outer layers of compact bone.

The diploic veins drain this area to the outside of the skull.

Specific diploic veins

They are usually four in number: one frontal, two parietal, and one occipital. These bones are also called the diploic bones.

• (1) the frontal, which opens into the supraorbital vein and the superior sagittal sinus.

• (2) the anterior temporal, which is confined chiefly to the frontal bone, and opens into the sphenoparietal sinus and into one of the deep temporal veins, through an aperture in the great wing of the sphenoid.

• (3) the posterior temporal, which is situated in the parietal bone, and ends in the transverse sinus, through an aperture at the mastoid angle of the parietal bone or through the mastoid foramen.

• (4) the occipital, the largest of the four, which is confined to the occipital bone, and opens either externally into the occipital vein, or internally into the transverse sinus or into the confluence of the sinuses (torcular Herophili).