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Wednesday, October 08, 2008

Which of the following statements about Diploic Veins is not true

Question 6
Which of the following statements about Diploic Veins is not true
a)      They are seen in Cranial Bones
b)      They arelined by single layer endothelium supported by elastic tissue
c)      They do not have valvesc. valveless
d)      They develop at 8th Week of Intrauterine Life
d) They develop at 8th Week of Intrauterine Life
Gray’s Anatomy 38th Edition Page 1581
Diploic veins occupy channels in the diploë of some cranial bones and are devoid of valves. They are large, with dilatations at irregular intervals; their thin walls are merely endothelium supported by elastic tissue. Radiographically they may appear as relatively transparent bands 3 or 4 mm wide. Absent at birth, they begin to develop with the diploë at about 2 years.
Self Explanatory
The diploic veins communicate with meningeal veins, dural sinuses and pericranial veins. Recognizably regular channels are:
Ä     Frontal diploic vein, emerging from bone in the supraorbital foramen to join the supraorbital vein
Ä     Anterior temporal (parietal) diploic vein, confined chiefly to the frontal bone, which pierces the greater wing of the sphenoid to end in the sphenoparietal sinus or anterior deep temporal vein
Ä     Posterior temporal (parietal) diploic vein, in the parietal bones, descending to the parietal mastoid angle to join the transverse sinus through a foramen at the angle or mastoid foramen
Ä     Occipital diploic vein, the largest, confined to the occipital bone, opening into occipital veins or the transverse sinus near the confluence of sinuses or into an occipital emissary vein.
In the cranial bones, the layers of compact tissue are familiarly known as the tables of the skull; the outer one is thick and tough; the inner is thin, dense, and brittle, and hence is termed the vitreous table. The intervening cancellous tissue is called the diploë, and this, in certain regions of the skull, becomes absorbed so as to leave spaces filled with air (air-sinuses) between the two tables.

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