Major Skeletal Muscles of Trunk and Upper Limbs Chapter 6 Lecture 4

Extend and adduct humerus Latissimus Dorsi Extend and adduct humerus The latissimus dorsi is a large muscle in the back. It is often referred to as a lat. *It has origins on the vertebrae, ilium ribs and scapula. *The insertion is on the humerus. When it contracts it moves the humerus. *It can extend, adduct and rotate the arm medially. This is the main muscle used in movement such as pounding a nail with a hammer.

Deltoid Abducts humerus The deltoid covers the shoulder and has the shape of a delta. *It has origins on the scapula and clavicle. *The deltoid inserts on the deltoid tuberosity of the humerus. *Contraction of the deltoid will adduct the arm. If only the anterior fibers of the muscle contract it will flex the arm. Contraction of the posterior fibers will extend the arm.

Adducts and flexes humerus Pectoralis Major Adducts and flexes humerus The pectoralis major is a large muscle in the pectoral region of the body. *It has origins on the clavicle and sternum. *The insertion is on the greater tubercle of the humerus. *Contraction of the pectoralis major will flex the arm. It will also adduct and rotate the arm medially. The pectoralis major is used in movements such a climbing, throwing and doing pushups.

Biceps Brachii Flexes Elbow and supinates forearm “Turns a corkscrew and pulls the cork” The biceps brachii is located on the anterior side of the upper arm. It is often just called the biceps. There is a biceps femoris in the leg we will study shortly. *The biceps has two origins. One origin is on the corocoid process and the other on the Glenoid cavity of the scapula. The “bi” in biceps refers to the two origins. *It inserts on the radial tuberosity. *Contraction of the biceps will cause flexing at the elbow joint.

Triceps Brachii Extends Elbow The triceps is on the back of the upper arm. *It has three origins. Two origins are on the back of the humerus and one on the scapula. *The triceps inserts on the olecranon. *Movement of the triceps will extend the elbow joint.  

Flexes vertebral column Most Superficial Rectus Abdominus Flexes vertebral column Most Superficial Rectus abdominus is a long muscle in the abdomen. *The muscle originates on the pubis. *It inserts on the xiphoid process of the sternum and also on cartilage of the ribs. *When rectus abdominus contracts it will flex the abdomen.  

Flexes and rotates vertebral column Superficial and lateral External Oblique Flexes and rotates vertebral column Superficial and lateral Another muscle in the abdomen is the external oblique. It has muscle fibers that run in an oblique direction across the abdomen. *Contraction of the external oblique will compress the abdomen.

Internal Intercostals Depress ribs when exhale Deep The internal intercostals are also located between the ribs. *They will depress the ribs.

External Intercostals Elevate ribs when inhale Deep There are two groups of muscles that run between the ribs. The first are the external intercostals. *They will elevate the ribs.

Erector spinae Back extension

Inspiration Found below lungs Diaphragm Inspiration Found below lungs This is an inferior view of the diaphragm. This muscle separates the abdominal cavity from the thoracic cavity. *When it contracts it will cause inspiration.

Forearm Muscles Flexor carpi radialis—Flexes wrist Extensor carpi—Extends wrist Flexor digitorum—Flexes fingers Extensor digitorum—Extends fingers There are several muscles in the forearm that have important movements. *The flexor carpi are used to flex the wrist. *Extensor carpi extend the wrist. *Flexor digitorum flexes the fingers. *Extensor digitorum extends the fingers. *The pronator pronates. *A supinator muscle will supinate.