Classification of Muscles and Rotator Cuff

How many muscles of the shoulder are superficial? Name them. What type of movers are they?

3 muscles. Pectoralis major, latissimus dorsi, deltoid. Prime movers.

How many muscles are synergists? How many of those are fixators?

6 muscles. 4 are fixators (aka rotator cuss muscles)

How many muscles make up the shoulder joint? What bone do they all insert on?

9 muscles. The humerus.

Synergist (syn)

Aid or work together with agonist by a)promoting the same movement as agonist or b)reducing undesirable/unnecessary movements that might occur as the prime mover contracts. (moving fingers with wrist stabilized by synergists)

Fixators

Are synergists that immobilize a bone. All of the rotator cuff muscles act as fixators to stabilize the humerus in the shoulder joint. Also some (rhomboids) run from axial skeleton to scapula to immobilize the scapula.

Continued over arm use can cause what?

Impingement, inflammation, and degeneration then tearing of the tendon at humerus attachment site.

Antagonist (ATG)

Muscles that oppose or reverse a particular movement in question. When the PM is active, the ATG is relaxed or stretched. (triceps)

Prime mover or Agonist (PM)

Muscles that provide major force for producing a movement. (bicep=PM for arm flexion) leader

What is the main function of the rotator cuff muscles and tendons?

Reinforce the shoulder joint and serve as fixators, preventing the dislocation of the humerus. Hold head of humerus in glenoid cavity. They also can act as synergists in angular/rotational arm movements.

Where do the rotator cuff muscles originate and insert?

Originate via tendons on scapula, encircle shoulder joint and insert on the humerous via tendons.

Name the four rotator cuff muscles.

Supraspinatus, infraspinatus, subscapularis, teres minor.

Name the synergists muscles that are not rotator cuff muscles

Teres major and Coracobrachialis. (not fixators)

Define rotator cuff

The actual tendons of the shoulder muscles. The tendons form a cuff like structure.

What is the Gelenohumeral Joint

The shoulder joint. Most flexible in body.

What tendon is the most frequent source of pain in the RC? Why?

The supraspinatus muscle tendon because of its position between the head of humerus and overlying acromial process.