26 THE POCKET ANATOMY 



maxilla(F) angle and inner surface of ramus of inferior 

 maxilla(TA) (Inferior maxillary). [Muscle of mastication; 

 elevates and draws lower jaw forward.] 



On muscle are inferior dental and gustatory nerves, internal 

 maxillary and inferior dental arteries, and internal lateral ligament 

 of jaw. 



SUPERFICIAL CERVICAL REGION. 



Platysma myoides : clavicle and acromion, fascia covering 

 deltoid, pectoralis major, and trapezius(p) Inner fibres. Blend 

 with opposite platysma. Outer fibres. Lower jaw, prolonged 

 to angle of mouth and cheek(p) (Facial). [Feeble depressor 

 of jaw ; moves skin of neck and maintains its contour.] The 

 higher fibres of this muscle form the risorius. 



Sterno-cleido-mastoid : Inner head. Upper and anterior 

 part of ist piece of sternum(T). Outer head. Inner ^ of 

 superior surface clavicle(F) external surface of mastoid pro- 

 cess from base to apex(i), and outer of superior curved line 

 of the occiput(A) (Spinal accessory, Deep branch of 2nd 

 cervical). [(A) Each side acting alone rotates face to opposite 

 shoulder and bends neck to same side ; (B) raises clavicle, 

 and so aids forced inspiration.] 



Forms anterior boundary of posterior, and posterior boundary of 

 anterior triangles of neck. Clavicular origin conceals : anterior 

 scalenus, omo-hyoid. Sternal origin conceals: depressors of 

 hyoid bone, cervical lymphatic glands, great cervical vessels 

 and pneumogastric nerve. Union of two heads conceals : middle 

 scalenus, levator anguli scapulas, cervical plexus. Near in- 

 sertion conceals : splenius, trachelo-mastoid, digastric, occipital 

 artery, part of parotid. 



The deep cervical fascia is attached behind to the superior 

 curved line of the occiput, to the ligamentum nuchae and to 

 the spine of yth cervical vertebra. 



It passes forwards enclosing the trapezius, and then over 

 the posterior triangle as a single layer (where external jugular 

 vein pierces it) until it reaches the posterior border of the 

 sterno-mastoid, where it divides into two layers to enclose 

 that muscle : in this area it is attached below to the clavicle 

 At the anterior border of the sterno-mastoid the two layers 

 again blend together (except for about one inch above the 

 sternum), and passing forwards, over the anterior triangle, it 

 blends with the fascia of opposite side in the middle line. 



Below where the two layers do not blend together, tbe 

 anterior one is attached to the front of the upper part 



