SURFACE AND SURGICAL ANATOMY. 



BY HAROLD J. STILES, F.B.C.S. 



THE HEAD AND NECK. 



THE CRANIUM. 



Scalp. The first and third layers of the scalp, "namely, the skin and the epi- 

 cranius muscle, are firmly united by fibrous processes which pass from the one to 

 the other through the second or subcutaneous fatty layer. Intervening between 

 these three layers and the pericranium is a loose cellular layer which supports the 

 small vessels passing between the scalp proper and pericranium. The thin peri- 

 cranium, although regarded anatomically as periosteum, possesses very limited 

 bone-forming properties ; over the vertex it is readily separated from the skull-cap, 

 except along the lines of the sutures, where it gives off intersutural processes to 

 join the endosteal layer of the dura. 



The free blood-supply of the scalp is for the purpose of nourishing its abundant 

 hair follicles and glands. The main vessels lie in the dense subcutaneous tissue, 

 and are superficial, therefore, to the epicranius (Fig. 1066). The arteries supplying 

 the frontal region are derived from the internal carotid, while those for the remainder 

 of the scalp spring from the external carotid. These two sets of vessels anastomose 

 freely with one another, and freely also across the median plane ; hence the failure 

 of ligature of the external carotid to cure cirsoid aneurysm of the temporal artery. 



"Wounds of the scalp bleed freely, and the vessels are difficult to ligature on account of the 

 adhesion of their walls to the dense subcutaneous tissue. In extensive flap wounds and in 

 diffuse suppuration beneath the epicranius there is little danger of sloughing of the scalp. 

 Abscesses and haemorrhages superficial to the epicranius are usually limited on account of 

 the density of the subcutaneous tissue. Haemorrhage beneath the epicranius is seldom 

 extensive on account of the small size of the vessels, but suppuration in this situation may 

 rapidly undermine the whole muscle and its aponeurosis the galea aponeurotica ; incisions to 

 evacuate the pus should be made early, and parallel to the main vessels of the scalp. Extravasa- 

 tion of blood beneath the pericranium leads to a haematoma which is limited by the sutures. 



The veins of the scalp communicate with the intra-cranial venous sinuses 

 (1) directly through their anastomoses with the large emissary veins, namely, the 

 parietal, which opens into the superior sagittal sinus, and the mastoid and condyloid, 

 which open into the transverse sinus ; (2) through the anastomoses of the frontal 

 and supra-orbital veins with the ophthalmic vein, which opens into the cavernous 

 sinus ; (3) through the veins of the diploe, which connect the veins of the scalp 

 and the pericranium on the one hand with those of the dura mater and the venous 

 sinuses on the other; (4) through small veins which pass from the pericranium 

 through the bones and the intersutural membranes to the dura. It is along these 

 various channels that pyogenic infection may extend, from the scalp and pericranium, 

 through the bone to the dura mater and venous sinuses, and from the latter to the 

 cerebral veins, the pia-arachnoid, and the substance of the brain. More rarely the 

 infection spreads from the cranial cavity along the emissary veins to the scalp. 



The lymph vessels of the anterior part of the scalp join the external maxillary 

 lymph vessels ; those of the temporal and parietal regions open into the pre-auricular 

 and parotid lymph glands, situated in front of and below the ear, and into the 

 post-auricular or mastoid glands, situated upon the insertion of the sterno-mastoid 

 muscle. The lymph vessels of the occipital region open into the occipital glands, 

 which lie. close to the occipital artery where it becomes superficial in the scalp. 



1357 



