294 



Muscles of the Back. 



339. Short muscles of the back 



(2"^^ layer 



c), viewed from behind. 



Protiiberantia 

 occipitalis externa 



Processus mastoideiis 



multifidus 



Processus spinosus 



vertebrae 



cervicalis VII 



Costa II 



Processus 



spinosus 



vertebrae 



thoracal is VI 



Costa XI 



Processus spinosus 



vertebrae 



thoracalis XI T 



Pelvis 



Fascia 

 mbodorsalis 

 ut through) 



M. 



multifidus 



^ 



M. multifidus (see also 

 Fig. 337) is the second layer 

 of the muscular mass extending 

 from the procc. transversi to 

 the procc. spinosi ohliquely 

 upward; it lies in the back 

 and neck just below the m. 

 seraispinalis, in the Imnbar 

 region just below the m. longis- 

 siraus dorsi; its fibers bridge 

 over from two to four vertebral 

 bodies . Origins: posterior 

 surface of the sacrum, procc. 

 mamillares and accessorii of 

 the limibar vertebrae, procc. 

 transversi of the thoracic ver- 

 tebrae and procc. articulares of 

 the 1^^ i^^ cervical vertebra. 

 Insertions: procc. spinosi of 

 the lumbar, thoracic and cer- 

 vical vertebrae (with the ex- 

 ception of the atlas). Action: 

 it bends the spinal column back- 

 ward and rotates it toward the 

 opposite side (it bends the 

 lumbar spine backward only, 

 without rotating it). Inner- 

 vation: rami mediales of the 

 rami posteriores of the nn. cer- 

 vieales III VIII, thoracales 

 I XII and lumbales I \. 



The mm. rotatores (see 

 Fig. 340) form the third, deepest 

 layer of the fiber masses going 

 oblitpiely tipward from the 

 procc. transversi to the procc. 

 spinosi; they are completely 

 hidden by the m. multifidus. 

 They consist of single, narrow, 

 thin muscle bands. 



Mm. i-otatoros lougi 

 bridge over one vertebra. 



Mm. rotsitores breves 

 iro tn thi" next vertebra above. 

 Both go to the root of the 

 procc. spinosi or to the arcus 

 vertebrae, are present from the 

 sacrum as far as the 2"d cer- 

 vical vertebra and, below, rim 

 nearly vertically, above, more 

 transversely. Action and 

 i n n e r V a t i 1 1 n : same as for 

 thi' m. multifidus. 



