The muscles of the torso extend in several directions. These muscles work together in groups contracting and relaxing to support and propel the torso. These muscles also help maintain posture and aid the spinal muscles when bending, twisting, and in a wide range of other movements, such as breathing, coughing, sneezing, laughing, and sighing..
The sternocleidomastoid muscle is located in the neck. It is a thin, broad muscle that narrows at the center. It originates from two heads, one from the sternum (breastbone) and one from the clavicle (collar bone), and runs upward, inserting into the mastoid (the temporal bone behind the ear). This muscle is used to tilt the head from side to side.
The deltoid muscle is a thick triangular muscle which cups the shoulder joint. It is attached to the clavicle (collar bone) and scapula (shoulder blade) at its upper end, and to the shaft of the humerus (upper arm bone) at its lower end. The muscle is divided into three portions: an anterior (clavicular) portion, and acrominal (middle) portion, and a posterior portion. The posterior portion is located on the back of the shoulder. Almost any movement of your shoulder and upper arm involves the deltoid muscle. The anterior portion is used to raise the arm from the body and to lower it again. The acrominal portion is a powerful abductor and the posterior portion is used to move the arm backward.
The pectoralis major muscle is located at the front of the thoracic cage. It is a thick, fan-shaped muscle and is divided into two parts that begin at the armpit and cover most of the front of the chest. The upper, or clavicular, part is attached to the clavicle (collar bone). The lower, or sternocostal, is attached mainly to the sternum (breast bone) and costal cartilage. This muscle is used when you bring your arms across the chest, raise and lower the arms and to rotate the arms. The clavicular portion will raise the arm, while the sternocostal portion will pull it down.
The serratus anterior (serratus magnus) is a large quadrilateral muscle that curves along the rib cage. The muscle is divided into several bundles, each of which extends along the side and upper border of each rib. The muscle is divided into two portions, and upper and lower portion. The upper portion lies along the upper side of the rib cage and the armpit. The lower portion consists of five or six pointed digitations which create a fan-shaped mass extending from the scapula (shoulder blade). This muscle is used everytime you reach out or push forward with your arms. It also helps raise the shoulder joint when lifting your arm above your head.
The intercostals are long belt-shaped muscles that form thin sheets of muscles weaved between the bones of the rib cage. They are your breathing muscles. As they contract, they pull the ribs up to expand the chest with every breath.
The rectus abdominis is a long, flat, vertical muscle located along the front of the abdomen. It is wide and thin at its point of origin along the crest of the pubic bone (pelvis) and tapers below to insert in the cartilage of the fifth, sixth, and seventh ribs. This muscle is used when you bend forward. It also tenses the abdominal wall and aids in compressing the contents of the abdomen. The muscle is enclosed in a sheath of fascia that holds it in position, but does not restrict its movement during its contractions.
The external oblique is a large, thin sheet of muscle that runs along the side of the torso and partly on the front. The muscle is divided into two portions; and upper thoracic portion and a lower flank portion. The thoracic portion is located along the rib cage. The individual ribs can be seen beneath this muscle when it is relaxed. The lower flank portion is located along the side of the abdomen between the rib cage and the pelvis. Most of this muscle is concealed by fat. The two portions meet at the waist. This muscle is used when you bend forward and twist from side to side.
The internal oblique is a small, thin, deep muscle of the abdomen. It has a quadrilateral form running from the hip bone (crest of the ilium) to the cartilage of the lower ribs (the seventh, eighth, and ninth ribs). This muscle works with the external oblique to help twist the torso.
The transversus abdominis is a broad, flat muscle of the abdomen that is named after the direction of its fibers. The muscle lies just below the internal oblique and spans the area from the pelvis to the six lower ribs and the lumbar region of the spine, where it connects to the lumbar fascia. This muscle assists in breathing.
The pyramidalis is a small, triangular muscle located towards the lower part of the abdomen. It is located just in front of the rectus abdominis muscle.
Other links
for injury info Bone Doctor
Knowledge
Adventure