ch. 9 shoulder girdle

if the humerus does up 30 degrees, how much has the scapula moved?

0 degrees

In the resting position, the scapula is located between what ribs?

2nd and 7th

The articulation of the lateral end of the clavicle and superior scapula

Acromioclavicular joint

term commonly used to describe the various amounts of ligament injury at the AC joint. In a first-degree sprain, the acromioclavicular ligament

Acromioclavicular separation In a first-degree sprain, the acromioclavicular ligament (see Fig. 9-8) is stretched. In a second-degree sprain, the acromioclavicular ligament is ruptured, and the coracoclavicular ligament (see Fig. 9-8) is stretched. In a third-degree sprain, both the acromioclavicular and coracoclavicular ligaments are ruptured.

understanding synonymous terms

At this joint, protraction and abduction are synonymous terms, as are retraction and adduction. For example, shoulder girdle protraction and retraction is synonymous with scapular abduction and adduction. Scapular rotation is the same as shoulder girdle rotation.

serratus anterior muscle prime mover

Because it has a nearly horizontal line of pull outward, it is a prime mover in scapular protraction.

upper trapezius muscle line of pull and action

Because its line of pull is more vertical (upward) than horizontal (inward), it is a prime mover in scapular elevation and upward rotation and is only an assisting mover in scapular retraction.

account for the most frequently broken bone in children. They usually result from a fall on the lateral aspect of the shoulder or on the outstretched hand. The clavicle usually breaks in its midportion.

Clavicular fractures

Innervation of Trapezius

Cranial nerve XI (accessory nerve) C3, C4 (sensory)

Levator scapula innervation

Dorsal scapular C3, C4, C5

Rhomboids innervation

Dorsal scapular C5

When two or more muscles pull in different directions to create a combined action

Force couple

The shoulder joint consisting of the articular surfaces of the humeral head and glenoid fossa of the scapula

Glenohumeral joint

A ring of fibrocartilage that lines the lip of the glenoid cavity

Glenoid labrum

The compression of structures caused by narrowing of the space surrounding them or encroachment of tissue into the space

Impingement

Identify the muscles that form the force couples responsible for upward rotation of the scapula of the shoulder girdle.

In the case of the shoulder girdle, the upper trapezius muscle pulls up, the lower trapezius muscle pulls down, and the lower fibers of the serratus anterior muscle pull outward in a horizontal direction. The net effect is that the scapula rotates upward

type of joint and motion of AC joint

It is a plane-shaped synovial joint that allows a gliding motion to occur, contributing toward movement in three planes of motion

lower trapezius muscle line of pull and action

Its diagonal line of pull is more downward (vertical) than inward (horizontal), making it a prime mover in depression and upward rotation of the scapula and only an assisting mover in retraction.

middle trapezius muscle

Its line of pull is horizontal, which makes it very effective at scapular retraction. Because the line of pull passes just above the axis for upward rotation, its role in scapular upward rotation is only assistive.

Serratus anterior innervation

Long thoracic C5, C6, C7

Pectoralis minor innervation

Medial pectoral C8, T1

Occurs when the distal segment is fixed or stable and the muscle pulls the origin toward insertion

Reverse muscle action

The tendinous insertions of the subscapularis, infraspinatus, teres minor and supraspinatus muscles on the tubercles of the humerus

Rotator cuff

Elevation of the arm in the plane of the scapula

Scaption

Approximately 30 degrees forward of the frontal plane

Scapular plane

occurs when the scapula moves away from the posterior midline

Scapular protraction (scapular abduction)

Movement of the inferior angle of the scapula posteriorly

Scapular tilt

occurs when the shoulder joint goes into hyperextension.

Scapular tilt The superior end of the scapula tilts anteriorly, and the inferior end tilts posteriorly. Examples of these combined motions are the "windup" or prerelease phase of a softball pitch, a bowling delivery, or a racing dive in swimming.

the posterior lateral movement of the vertebral border of the scapula in the transverse plane. In other words, the vertebral border of the scapula moves away from the rib cage.

Scapular winging Winging of the scapula (posterior view). This person's right serratus anterior muscle is paralyzed. When pushing against the wall with both hands, the right scapula rises away from the rib cage, standing out like a small wing.

A term used to describe the ratio of normal motion between the glenohumeral and scapulothoracic joints

Scapulohumeral rhythm

a concept that further describes the movement relationship between the shoulder girdle and the shoulder joint.

Scapulohumeral rhythm The first 30 degrees of shoulder joint motion is pure shoulder joint motion. However, after that, for every 2 degrees of shoulder flexion or abduction that occurs, the scapula must upwardly rotate 1 degree. This 2:1 ratio is known as scapulohumeral rhythm. after the first 30 degrees, the scapula will need to lift/move in order to allow the full range of motion. for every 2 degrees the arm goes up at the glenohumeral joint, there is one degree at the scapulothoracic joint

The articulation of the anterior surface of the scapula against the posterior ribs

Scapulothoracic joint

A ring of bony articulations consisting of the acromioclavicular joints, sternoclavicular joints, and scapulothoracic joints

Shoulder girdle

term often used to discuss the activities of the scapula and clavicle and, to a lesser degree, the sternum and ribs.

Shoulder girdle

The articulation of the medial end of the clavicle and lateral sternum

Sternoclavicular joint

Identify the muscles that form the force couples responsible for downward rotation of the scapula of the shoulder girdle.

The combined effects of the pectoralis minor muscle pulling down, the rhomboid muscles pulling in, and the levator scapula muscle pulling up is downward rotation of the scapula

The shoulder girdle and glenohumeral joints combined

The shoulder complex

this joint consists of the scapula and humerus. what is it called and what are the motions?

The shoulder joint, also called the glenohumeral joint, consists of the scapula and humerus. The motions of the shoulder joint are flexion, extension and hyperextension, abduction and adduction, medial and lateral rotation, and horizontal abduction and adduction.

five muscles primarily responsible for moving the scapula

Trapezius Levator scapula Rhomboids Serratus anterior Pectoralis minor

Movement of the vertebral border of the scapula posteriorly

Winging

Reverse muscle action during crutch walking with hands bearing weight on crutch handles to prevent scapula and rib cage from depressing. The pectoralis minor (A) is pulling up on the rib cage while the lower trapezius (B) pulls up on the vertebral column and pelvis to elevate the body, allowing it to swing through the crutches.

With the shoulder girdle stabilized, the lower trapezius and pectoralis minor can reverse their actions and assist in elevating the trunk. This is particularly useful during crutch walking. With the crutches planted on the floor and the hands bearing weight on the crutches, the scapula becomes stabilized, preventing the lower trapezius and pectoralis minor from depressing the scapula when they contract. Instead, their origins move the body upward toward the scapula, thus raising the body as it swings through the crutches

connects the acromion process of the scapula and the lateral (acromial) end of the clavicle.

acromioclavicular (AC) joint

serves as a shock absorber in the SC joint

articular disk

where does motion occur during elevation and depression of the SC joint

between the clavicle and disk

What does the musculocutaneous nerve innervate?

biceps, brachialis

what makes up the shoulder girdle

clavicle and scapula

Movement of the vertebral border of the scapula medially and inferiorly

downward rotation

combined motions for retraction

downward rotation, depression, adduction

motions of the SC joint

elevation and depression in the frontal plane as well as protraction and retraction in the transverse plane, and rotation occurs along the longitudinal axis of the bone (the clavicle spins on the sternum). Basically, the clavicle moves while the sternum remains stationary.

motions of the shoulder girdle

elevation and depression, protraction and retraction, and upward and downward rotation

The sternoclavicular and acromioclavicular joints allow shoulder girdle motions, including

elevation and depression, protraction and retraction, and upward and downward rotation.

True motions of scapula

elevation, depression, adduction, abduction

shoulder girdle innervation

fairly high off the spinal cord from a variety of sources proximal to the terminal nerves of the brachial plexus.

defined as muscles pulling in different directions to accomplish the same motion

force couple

what part of the trapezus is only the prime mover?

middle

where does motion occur during protraction and retraction on SC joint

motion occurs between the disk and the sternum.

levator scapula muscle prime mover for

named for its function of scapular elevation

rhomboids prime mover

prime mover in retraction and elevation rhomboids rotate the scapula downward.

All three parts of the trapezius muscle work together (synergists) to

retract the scapula.

The actions of the shoulder girdle muscles have been described as moving the insertion toward the origin. However, if the insertion is stabilized, the origin will move. This is called what?

reverse muscle action It allows some of the shoulder girdle muscles to have assistive roles in other joints, primarily the head and neck.

what makes up the shoulder joint

scapula and humerus

what makes up the shoulder complex

scapula, clavicle, sternum, humerus, rib cage, and includes the sternoclavicular joint, acromioclavicular joint, glenohumeral joint, and scapulothoracic articulation. in other words- it includes the shoulder girdle (scapula and clavicle) and the shoulder joint (scapula and humerus)

occurs when the scapula moves inferiorly

scapular depression

the return to the resting anatomical position from the upwardly rotated position.

scapular downward rotation

occurs when the scapula moves in a superior direction

scapular elevation

occurs when the scapula moves back toward the posterior midline.

scapular retraction (scapular adduction)

the inferior angle of the scapula rotates up and away from the vertebral column

scapular upward rotation

not a joint in the pure sense of the word as there is no direct union between the bones, and there is no joint capsule. It consists of the slightly concave anterior surface of the scapula resting on the convex posterior aspect of the rib cage. provides motion necessary for normal function of the scapula.

scapulothoracic articulation

formed by the articulation between the manubrium of the sternum and the medial (sternal) end of the clavicle.

sternoclavicular (SC) joint

The three major ligaments supporting SC joint

sternoclavicular, costoclavicular, and interclavicular ligaments

Rotator Cuff Muscles (SITS)

supraspinatus, infraspinatus, teres minor, subscapularis

convex/concave rule on SC joint during shoulder girdle elevation and depression & During protraction and retraction

the convex surface of the clavicle slides inferiorly and superiorly on the concave manubrium as the clavicle's lateral end moves up and down, respectively. This motion occurs between the clavicle and the disk. the concave portion of the clavicle slides anteriorly and posteriorly on the convex costal cartilage, respectively as the clavicle's lateral end moves forward and backward. This motion occurs between the disk and the sternum.

Scapular motion during upward rotation.

the inferior angle of the scapula rotates up and away from the vertebral column

large, superficial muscle that appears diamond-shaped when looking at both right and left sides. Anatomically it is one muscle, but functionally, it is usually divided into three parts: upper, middle, and lower. The reason for this separation is that there are three different lines of pull (upward, inward, downward) resulting in different muscle actions.

trapezius muscle

prime motions of AC joint

upward and downward rotation in the plane of the scapula The AC joint can also contribute toward scapular tilt in the sagittal plane, and when present, scapular winging in the transverse plane.

Movement of the vertebral border of the scapula laterally and superiorly

upward rotation

combined motions for protraction

upward rotation, elevation, abduction