MUSCLES: TRUNK

MUSCLES: TRUNK

1. VERTEBRAL MUSCLES

   • EPAXIAL MUSCLES
     • Found: dorsal to the transverse process of the vertebral column. Attached to: the sacrum, pelvis, vertebrae and ribs Action: extensors of the vertebral column (spine)
   • HYPAXIAL MUSCLES
     • Found: ventral (towards the abdomin wall) to the vertebral column. -not bulky as they don't support- there is alot of intermingling between bundles, so its difficult  to separate. Action: help to bend the neck down and flex the lumbar spine.
   • INTERCOSTAL MUSCLES
     • Found: running between the adjacent ribs Action: helps to form the wall of the thoracic cavity & helps with respiration (inspiration)
     • EXTERNAL
       • Action: draws ribs together during inspiration
     • INTERNAL
       • Action: lie deeply to assist in expiration

2. TRAPEZIUS MUSCLE

   • Origin: Thoracic vertebrae Insertion: Spine of the scapula Action: elevates the shoulder and draws the the forelimb forward

3. BRACHIOCEPHALICUS

   • Origin: Cervical vertebrae and head Insertion: shaft of the humerus  Action: Extends the shoulder joint, drawing the leg forward.

4. LATISSIMUS DORSI

   • Origin: Lumbar vertebrae Insertion: Humerus- medially  Action: Draws the leg backwards & the trunk forwards - one of the main synsarcosis muscles.

5. DIAPHRAGM

   • -The centre is tendinous and has muscle fibres which radiate outwards. - attached to ventral surfaces of the lumbar vertebrae by crura (thickened muscles) - Domed in shape and moves in and out with respiration. - Attaches to the ribs: dorsally- cranial to the costal arch ventrally- at the caudal end of the sternum.
   • POST CAVAL HIATUS
     • AKA HOLE. through which the vena cava passes.
   • OESOPHAGEAL HIATUS
     • AKA HOLE where the oesophagus, the oesophageal vessles and vagal nerves pass to the abdomen 
   • AORTIC HIATUS
     • AKA HOLE  where the aorta, azygous vein and thoracic duct pass.

6. ABDOMINAL MUSCLES

   • when contracted they aid in: -urination  -defecation -parturition -respiration -locomotion  Covered superficially by abdominal fasciae (fibrous tissue) Each muscle ends in a sheet of fasciae called aponeurosis
   • THE ABDOMINAL WALL
     • The four muscles which make up the wall are arranged so that the muscle fibres run in all different directions- providing maximum strength 
     • EXTERNAL ABDOMINAL OBLIQUE
     • INTERNAL ABDOMINAL OBLIQUE
     • TRANSVERSUS ABDOMINUS
     • RECTUS ABDOMINUS
   • LINEA ALBA (WHITE LINE)
     • Strong seam of fibrous tissue that runs down the sternum to pelvis. Formed by the aponeuroses of the abdominal muscles where they meet at the midline.