Muscle Lab 2
In this lab you will continue your investigation of the muscles of the trunk.
Begin by orienting the body by clicking on the following:
You will see the torso with the skin and arms removed.
Locate the right and left sternocleidomastoid muscles. Notice the sternal and clavicular heads.
Rotate the body 90 degrees to the right. Notice how the sternocleidomastoid originates on the mastoid process of the temporal bone. This muscle is easily visualized on someone. It is a straplike muscle on the side of the neck. It's function is to rotate and flex the head.
Locate the masseter muscle. This muscle is involved in chewing and can be a source of pain in temporomandibular disorders.
Locate the trapezius muscle. Notice there are superior, middle and inferior parts to this muscle.
Locate the serratus anterior muscle. This muscle works to hold the scapula in place. A weakness of the serratus anterior causes winging of the scapula.
Rotate the body to 180 degrees to the right.
Locate the trapezius muscle. Notice how it far it extends inferiorly.
Locate the thoracolumbar fascia just inferior to the trapezius. Locate the latissumus dorsi muscle. Notice how it inserts on the thoracolumbar fascia. The latissumus dorsi extends superiorly to insert on the humerus at the intertubercular groove.
Moving superior locate the ligamentum nuchae. Notice how this structure extends from the occipital bone inferiorly.
Dissect away all 3 divisions of the left and right trapezius muscles.
Locate the rhomboid muscles. Notice there are 2 parts to the rhomboids; the larger rhomboideus major and the smaller rhomboideus minor just superior to it.
Just superior to the rhomboids are the splenius capitus and semispinalis capitus. These work to extend the cervical spine.
Dissect away both parts of the rhomboid muscles.
Here you will see the following muscles that act as spinal extensors:
Longissumus thoracis
Spinalis thoracis
Iliocostalis lumborum
(You will not be responsible for these individual muscles. You are responsible for knowing these as a group called spinal extensors).
Rotate the body back to 0 degrees.
Dissect away both pectoralis major muscles.
Locate the intercostal muscles. There are 2 layers of intercostals: external and internal.
This concludes the lab.