550 HUMAN ANATOMY. 



3. Rectus Capitis Anticus Minor. 



Attachments. — The rectus capitis anticus minor (m. rectus capitis anterior) 

 is a short, flat muscle which arises from the anterior surface of the lateral mass of 

 the atlas and is directed obliquely upward and medially to be inserted into the 

 basilar portion of the occipital bone, immediately behind the insertion of the longus 

 capitis. 



Nerve-Supply. — By the first cervical (suboccipital) nerve. 



Action. — To flex the head. 



PRACTICAL CONSIDERATIONS : THE NECK. 



The skin of the front and sides of the neck is thin and movable. The platysma 

 myoides is closely connected to it by the thin superficial fascia. The edges of wounds 

 transverse to the fibres of that muscle are therefore often inverted. 



In the region of the nape of the neck the skin is thicker and much more closely 

 adherent to the deep fascia; it is poorly supplied with blood ; hair-follicles and 

 sebaceous glands are numerous ; it is frequently exposed to minor traumatisms and 

 to changes of surface heat, and is often at a lower temperature than the parts 

 immediately above, which are covered with hair, or than those directly below, which 

 are protected by clothing; the nerve-supply is abundant. For these reasons furun- 

 cles and carbuncles are of common occurrence and are apt to be exceptionally painful. 



The subcutaneous ecchymosis which follows fracture through the posterior cerebral 

 fossa first appears anterior to the tip of the mastoid and spreads upward and back- 

 ward on a curved line ; the blood is prevented from reaching the surface more 

 directly by the cervical fascia, and therefore goes laterally in the intermuscular 

 spaces, being directed towards the mastoid tip by the posterior auricular artery. 



In the submaxillary region the looseness of the skin makes it available for 

 plastic operations on the cheeks and mouth. In the submental region the accu- 

 mulation of subcutaneous adipose tissue seen in stout persons gives rise to the 

 so-called " double chin." In both the latter regions (covered by the beard in men) 

 furuncles and sebaceous cysts are common. 



The surgical relations of the fascia of the neck can best be understood by refer- 

 ence to a horizontal section at the level of the seventh cervical vertebra (Fig. 545). 



The superficial layer (a, a') will then be seen to envelop the entire neck. Pos- 

 teriorly it is attached between the external occipital protuberance and the seventh 

 cervical spinous process to the ligamentum nuchae ; anteriorly it is interlaced with 

 the same layer of fascia from the other side of the neck ; superiorly between the 

 external occipital protuberance and the middle of the chin it is attached on each side 

 to the superior curved line of the occipital bone, the mastoid, the zygoma, and the 

 lower jaw ; inferiorly between the seventh spine and the suprasternal notch it is 

 attached on each side to the spine of the scapula, the acromion, the clavicle, and the 

 upper edge of the sternum. After splitting to enclose the trapezius and covering in 

 the posterior triangle, this fascia divides again at the hinder border of the sterno- 

 cleido-mastoid. The superficial layer continues over the surface of that muscle, 

 covers in the anterior triangle, and blends with its fellow of the opposite side. 



From its under surface, after reaching the sterno-mastoid, the deeper layer gives 

 off from behind forward (<^) a process — prevertebral fascia — which begins near the 

 posterior border of the sterno-mastoid, passes in front of the scalenus anticus, the 

 phrenic nerve, the sympathetic nerve, and the longus colli muscle, and behind the 

 great vessels, the pneumogastric nerve, and the oesophagus to the front of the base 

 of the skull and the bodies of the cervical vertebrae. In the mid-line this descends 

 behind the gullet into the thorax. At the sides of the neck it helps to form the pos- 

 terior wall of the carotid sheath, spreads out over the scalene muscles, and passes 

 down in front of the subclavian vessels and the brachial plexus, until it dips beneath 

 the clavicle. It is then ajij^lied closely to the under surface of the costo-coracoid 

 membrane and splits to become the sheath of the axillary vessels. A second process 

 (r), leaving the sterno-mastoid more anteriorly, aids in forming the anterior wall of 

 the carotid sheath, and joins the preceding layer just internal to the vessels. It is 



