THE DEEP MUSCLES OF THE BACK 



397 



The Lumbodorsal Fascia (fascia lumbodorsalis; lumbar aponeurosis and vertebral 

 fascia). The lumbodorsal fascia is a deep investing membrane which covers the 

 deep muscles of the back of the trunk. Above, it passes in front of the Serratus 

 posterior superior and is continuous with a similar investing layer on the back of 

 the neck the nuchal fascia. 



In the thoracic region the lumbodorsal fascia is a thin fibrous lamina which 

 serves to bind down the Extensor muscles of the vertebral column and to separate 

 them from the muscles connecting the vertebral column to the upper extremity. 

 It contains both longitudinal and transverse fibers, and is attached, medially, to 

 the spinous processes of the thoracic vertebra? ; laterally to the angles of the ribs. 



In the lumbar region the fascia (lumbar aponeurosis} is in two layers, anterior 

 and posterior (Figs. 388, 409). The posterior layer is attached to the spinous 

 processes of the lumbar and sacral vertebrae and to the supraspinal ligament; the 

 anterior layer is attached, medially, to the tips of the transverse processes of the 

 lumbar vertebrae and to the intertransverse ligaments, below, to the iliolumbar 

 ligament, and above, to the lumbocostal ligament. The two layers unite at the 

 lateral margin of the Sacrospinalis, to form the tendon of origin of the Transversus 

 abdominis. The aponeurosis of origin of the Serratus posterior inferior and the 

 Latissimus dorsi are intimately blended with the lumbodorsal fascia. 



sObliquus exiernus 

 sObliquus internus 

 Transversus 



Fascia on 

 Quad. Lumb. 



Lumbodorsall Anierior 

 fascia 



Fia. 388. Diagram of a transverse section of the posterior abdominal wall, to show the disposition of the 



lumbodorsal fascia. 



The Splenius capitis (Fig. 409) arises from the lower half of the ligamentum 

 nuchse, from the spinous process of the seventh cervical vertebra, and from the 

 spinous processes of the upper three or four thoracic vertebrae. The fibers of 

 the muscle are directed upward and lateral ward and are inserted, under cover of 

 the Sternocleidomastoideus, into the mastoid process of the temporal bone, and 

 into the rough surface on the occipital bone just below the lateral third of the 

 superior nuchal line. 



The Splenius cervicis (Splenius colli) (Fig. 409) arises by a narrow tendinous 

 band from the spinous processes of the third to the sixth thoracic vertebrae; it is 

 inserted, by tendinous fasciculi, into the posterior tubercles of the transverse 

 processes of the upper two or three cervical vertebrae. 



Variations. The origin is frequently moved up or down one or two vertebrae. Accessory slips 

 are occasionally found. 



Nerves. The Splenii are supplied by the lateral branches of the posterior divisions of the 

 middle and lower cervical nerves. 



Actions. The Splenii of the two sides, acting together, draw the head directly backward, 

 assisting the Trapezius and Semispinalis capitis; acting separately, they draw the head to one 

 side, and slightly rotate it, turning the face to the same side. They also assist in supporting the 

 head in the erect position. 



The Sacrospinalis (Erector spince) (Fig. 389), and its prolongations in the 

 thoracic and cervical regions, lie in the groove on the side of the vertebral column. 



