1286 HUMAN ANATOMY. 



and the diaphragm, whilst others communicate with the ninth, eleventh and twelfth 

 cranial and the sympathetic nerves. 



THE CERVICAL PLEXUS. 



I. Superficial Branches. II. Deep Branches. 



A. Ascending branches : D. External branches : 



1. Small occipital 7- Muscular 



2. Great auricular 8. Communicating 



B. Transverse branch : E. Internal branches : 



3. Superficial cervical 9. Muscular 



C. Descending branches : 10. Phrenic 



4. Suprasternal n. Communicating 



5. Supraclavicular 



6. Supraacromial 



I. The superficial branches are purely sensory. They become superficial 

 at the posterior border of the sterno-mastoid, slightly above its middle, and from that 

 point radiate in all directions to reach their cutaneous destinations (Fig. 1087). 



1. The small occipital nerve (n. occipitalis minor) (Fig. 1087) may be either 

 single or double. It originates from the second and third cervical nerves, or from 

 the second only, and passes backward and upward beneath the deep fascia along or 

 overlapping the posterior border of the sterno-mastoid muscle, where it gives off (a) 

 the cervical branches. It pierces the deep fascia at the upper angle of the occipital 

 triangle and breaks up into its terminal branches : (6) the auricular, (<:) the mastoid 

 and (d) the occipital. 



a. The cervical branches are tiny twigs which supply the skin over the upper part of the 

 occipital triangle. 



b. The auricular branch supplies the integument over the cranial aspect of the posterior 

 part of the pinna. 



c. The mastoid branch supplies the scalp overlying and above the mastoid process. 



d. The occipital branch is distributed to the area of scalp of the occiput lying between the 

 mastoid process and the distribution of the great occipital nerve. 



The small occipital communicates with the posterior and great auricular nerves and with 

 the great occipital. 



Variations. The small occipital varies in size and may be so small as to be distributed 

 only to the integument in the neck. In such an event, and usually in case of any deficiency, 

 the unsupplied area receives fibres from the great occipital. It sometimes passes backward 

 instead of upward and pierces the trapezius near the upper border before reaching the scalp. 



2. The great auricular nerve (n. auricularis magnus) (Fig. 1087) is the larg- 

 est of the superficial set and arises, usually with the superficial cervical nerve, from 

 the second and third, from the third alone, or from the third and fourth cervical 

 nerves. Turning over the posterior margin of the sterno-mastoid it ascends toward 

 the ear between the platysma and the deep fascia. Below the ear it gives off a few 

 (a} facial twigs and then terminates by dividing into () auricular and (r) wastoid 

 branches. 



a. The facial twigs pass through the parotid gland and over the angle of the mandible, 

 supplying the integument over the parotid gland and masseter muscle and communicating with 

 the cervico-facial division of the seventh cranial nerve. 



b. The auricular branches (r. anterior) supply mainly the cranial surface of the posterior 

 part of the pinna. One filament passes through the cartilage by means of a cleft between the 

 concha and the antihelix and supplies the outer surface, while a few twigs are distributed to the 

 outer surface of the lobule. The auricular branches inosculate with the small occipital and pos- 

 terior auricular nerves. 



c. The mastoid branch ( r. posterior) is distributed to the skin overlying the mastoid process 

 and the upper part of the sterno-mastoid muscle. It inosculates as does the auricular branch. 



Variation. The mastoid branch may arise independently from the plexus and pass upward 

 to its destination between the small occipital and great auricular nerves. 



