Part 3

• Epaxial groups


  Dorsal to the transverse process of the vertebrae
• Epaxial muscles


  • Extensor of the vertebral column
• Hypaxial groups


  Ventral to the transverse processes, include those of the abdominal and thoracic walls
• Iliocostalis lumborum


  • Arises from the wing of the ilium in common with the longissimus lumborum and inserts on the transverse processes of the lumbar vertebrae and the last four or five ribs
  • In the lumbar region, this muscle is fused with the longissimus lumborum. The thoracolumbar fascia covers these muscles
• Iliocostalis thoracis


  • A long, narrow muscle mass extending from the 12th rib to the transverse process of the 7th cervical vertebra
  • Individual components of the muscle extend between and overlap the ribs
• Longissimus thoracis et lumborum


  • Its fibers run craniolaterally
  • Arises from the crest and medial surface of the wing of ilium, and by means of an aponeurosis, from the supraspinous ligament and the spines of the lumbar and thoracic vertebrae

  
• Longissimus cervicis


  • The cranial continuation of longissimus muscle into the neck
  • Consists of four fascicles so arranged that the caudal fascicles partially cover those that lie directly cranioventral to them
• Longissimus capitis


  • Distinct muscle medial to the longissimus cervisis and splenius muscles
  • It extends from the first three thoracic vertebrae to the mastoid part of the temporal bone
• Splenius


  • A rather large muscle on the dorsolateral surface of the neck, deep to the rhomboideus capitits and the serratus dorsalis cranialis
  • Its fibers extend in a slightly cranioventral direction from the third thoracic vertebrae to the skull

  
• Semispinalis capitis


  • A member of the cervical portion of the transversospinalis group. It lies deep to the splenius and extends from the thoracic vertebrae to the head
  • It consists of two muscles, the dorsal biventer cervicis (arises from the thoracis vertebra and inserts on the caudal surface of the skull) and the ventral complexus (arises from the cervical vertebra and inserts itself to the nuchal crest)
• Longus capitis


  • Lies on the lateral and ventral surfaces of the cervical vertebrae, lateral to the longus colli
  • It arises from the transeverse processes of the cervical vertebrae and inserts on the muscular tubercle on the ventral surface of the basioccipital bone of the skull

  
• Longus colli


  • Covers the ventral surfaces of the vertebral bodies from the sixth thoracic vertebra cranially to the atlas
  • It consists of many overlapping fascicles that attach to the vertebral bodies or the transverse processes. The most cranial cervical bundles attach to the atlas
• Scalenus


  • Lies ventral to the origin of the serratus ventralis
  • It attaches to the first few ribs and the transverse processes of the cervical vertebrae and is divided into several slips
• Serratus ventralis


  • Is a large, fan-shaped muscle with an extensive origin on the neck and trunk
  • Its insertion on the serrated face of the scapula
• Serratus dorsalis


  • Arises by a broad aponeurosis from the tendinous raphe of the neck and from the thoracic and lumbar spines and inserts on the proximal portions of the ribs
  • It consists of two portions: the serratus dorsalis cranialis and the serratus dorsalis caudalis
• External intercostal muscles


  • In respiration by drawing the ribs together
  • 12 on each side
  • Their fibers run caudoventrally from the caudal border of one rib to the cranial border of the rib behind
  • Their ventral border is near the costochondral junction
• Internal intercostal muscles


  • Their fibers run cranioventrally from the cranial border of one rib to the caudal border of the rub in front of it
  • Medial to most of the internal intercostal muscles is the pleura
  • It attaches to the muscles and ribs by the endothoracic fascia
  • The internal intercostal muscles extend the whole distance of the intercostal spaces
• External abdominal oblique


  • Covers the ventral half of the lateral thoracic wall and the lateral part of the abdominal wall
  • The costal part arises from the last ribs
  • The lumbar part arises from the last rib and from the thoracolumbar fascia
  • The fibers of the muscle run caudoventrally
  • In the ventral abdominal wall, these muscles forms a wide aponeurosis that inserts on the linea alba and the cranial pubic ligament
• Internal abdominal oblique


  • Arises from the superficial leaf of the thoracolumbar fascia caudal to the last rib, in common with the lumbar part of the external abdominal oblique, and from the tuber coxae and adjacent portion of the inguinal ligament
  • Its fibers run cranioventrally
• Transverse abdominis


  • Medial to the internal abdominal oblique and the rectus abdominis
  • Its fibers run transversely
  • The muscle arises dorsally from the medial surfaces of the last four or five ribs and from the transverse processes of all the lumbar vertebrae by means of the deep leaf of the thoracolumbar fascia

  
• Rectus abdominis


  • Extends from the pubis, where it forms the prepubic tendon, to the sternum
  • It flexes the thoracolumbar part of the vertebral column