Shoulders and Upper Arm muscles

Exercise 6 – Shoulder and Upper Arm

Part A: Features of the Shoulder and Upper Arm

• Muscle Group of Upper Back

  • The muscle group of the upper back that originates on cervical vertebra 7 and thoracic vertebrae 1-5 and acts to adduct the scapula is the rhomboideus group.

• Articulation Features of the Humerus

  • A rounded process of a bone located at an articulation site is called a head.

  • This feature of the humerus rests in a depression known as the glenoid cavity or fossa of the scapula.

• Muscles of the Shoulder

  • The muscle of the shoulder that originates on the posterior surface of the scapula above the spine is the supraspinatus. It acts to abduct the upper arm.

• Spine of the Scapula

  • The spine of the scapula forms a large lateral projection termed the acromion process.

• Muscles Acting on the Scapula

  • The muscle of the upper back and neck that originates on the occipital bone and the cervical and thoracic vertebrae, which functions to shrug the shoulders and rotate the scapula, is the trapezius.

• Features of the Scapula

  • The feature on the anterior, lateral region of the scapula is called the coracoid process.

• Chest Muscle Function

  • The muscle of the chest that originates on the first 8-9 ribs and acts to rotate the scapula forward is the serratus anterior.

• Clavicle Anatomy

  • The medial end of the clavicle is referred to as the sternal end, while the lateral end is called the acromial end.

• Elevation of the Scapula

  • The muscle of the upper back and neck that inserts on the superior border of the scapula and elevates the scapula is the levator scapulae.

• Borders of the Scapula

  • The lateral border of the scapula is known as the axillary border, and the medial border is termed the vertebral border.

• Deep Chest Muscle

  • The deep muscle of the chest that originates on ribs 3-5 and inserts on the coracoid process of the scapula is the pectoralis minor. It acts to depress and protract the scapula.

• Humerus Characteristics

  • The raised area in the middle of the diaphysis of the humerus is called the deltoid tuberosity.

• Shoulder Muscles

  • The muscle of the shoulder which originates on the clavicle and scapula and acts to abduct, flex, and extend the upper arm is the deltoid.

• Tubercle Features on Humerus

  • Small, knob-like processes on bones known as tubercles are found on the humerus just distal to the neck and are referred to as the greater and lesser tubercles.

Additional Features of Scapula and Motion

• Scapular Fossa

  • The subscapular fossa is located on the anterior surface of the scapula.

  • The supraspinous fossa and the infraspinous fossa are present on the posterior surface of the scapula.

• Superficial Chest Muscle

  • The superficial muscle of the chest that inserts on the intertubercular groove of the humerus and adducts the upper arm is called the pectoralis major. It also acts to flex and medially rotate the humerus.

• Circumduction Motion

  • Moving a body part such that its end follows a circular path is termed circumduction.

  • This motion is possible only at condylar and ball and socket joints.

• Large Muscle of the Back

  • The large muscle of the back which inserts on the intertubercular groove of the humerus and acts to extend and adduct the upper arm is the latissimus dorsi. It also medially rotates the humerus.

• Classification of Humerus

  • When classified according to shape, the humerus is categorized as a long bone.

• Infraspinatus Muscle

  • The muscle of the shoulder that originates on the posterior surface of the scapula below the spine is called the infraspinatus. It acts to laterally rotate the upper arm.

• Movement Motions

  • Moving a body part away from the midline of the body is termed abduction.

  • Moving that body part back toward the midline is known as adduction.

  • This motion occurs at the ball and socket joint formed between the humerus and scapula.

• Medial Rotation of Upper Arm

  • The muscle that originates on the anterior surface of the scapula and acts to medially rotate the upper arm is the subscapularis.

• Rotational Muscle Insertion

  • All muscles that rotate the upper arm laterally insert on the greater tubercle.

  • All muscles that rotate the upper arm medially insert either on the lesser tubercle or on the intertubercular groove.

  • The teres minor muscle inserts on the greater tubercle. It acts to laterally rotate and adduct the upper arm.

  • The teres major muscle inserts on the lesser tubercle. It acts to extend, adduct, and medially rotate the upper arm.