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You are watching: The infraspinatus inserts on the ____________ of the humerus.
The rotator cuff is a group of muscles in the shoulder that enable a wide variety of motion while maintaining the security of the glenohumeral joint. The rotator cuff contains the adhering to muscles<1><2><3>:
A valuable mnemonic come remember these muscles is "SITS."
The glenohumeral share is a ball and also socket joint and comprises a huge spherical humeral head and also a little glenoid cavity. This anatomy renders the joint extremely mobile, however, really unstable. Stabilization in the shoulder is detailed collectively through the non-contractile organization of the glenohumeral joint (static stabilizers) such as the capsule, the labrum, the negative intraarticular pressure and also the glenohumeral ligaments; and the contractile tissues (dynamic stabilizers) such as the rotator cuff and the lengthy head of the biceps brachii.
Structure and also Function
The main biomechanical role of the rotator cuff is to stabilize the glenohumeral share by compressing the humeral head against the glenoid. These 4 muscles arise indigenous the scapula and insert right into the humerus. The tendons that the rotator cuff muscle blend through the share capsule and type a musculotendinous collar that surrounds the posterior, superior, and also anterior aspects of the joint, leave the inferior aspect unprotected. This plan is crucial factor because most of the shoulder luxations occur since the humerus slides inferiorly with the unprotected component of the joint. During arm movements, the rotator muscles contract and also prevent the sliding of the head that the humerus, permitting full selection of motion and providing stability.
Additionally, rotator cuff muscles aid in the mobility that the shoulder share by facilitating abduction, medial rotation, and also lateral rotation.
Subscapularis: Medial (internal) rotation of the shoulder
Supraspinatus: abduction of the arm
Necessary for the early 0 to 15 levels of shoulder abduction motion
The deltoid muscle abducts the arm past 15 degrees
Infraspinatus: Lateral (external) rotation of the shoulder
Teres Minor: Lateral (external) rotation the the shoulder
During the physics examination, every muscle deserve to undergo independent evaluation based on the certain movement the each muscle.
Mesoderm gives rise to the muscles and also ligaments in the body.
Blood Supply and also Lymphatics
The vascular supply to the rotator cuff muscle is largely via the suprascapular artery, the subscapular artery, and the posterior circumflex humeral artery.
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The suprascapular artery is a branch the the thyrocervical tribe (a significant branch the the subclavian artery) and also originates at the base of the neck. The enters the posterior scapular region superior to the suprascapular foramen (the nerve passes v the foramen) and also supplies the supraspinatus and infraspinatus muscles.
The subscapular artery is the biggest branch the the axillary artery. It originates native the third component of the axillary artery, complies with the worse margin that the subscapularis muscle, and also then divides right into the circumflex scapular artery and the thoracodorsal artery. It gives vascular supply to the subscapularis muscle.
The posterior circumflex humeral artery originates indigenous the third part of the axillary artery in the axilla. It enters the posterior scapular an ar through the quadrangular space (accompanied by the axillary nerve) and also supplies the teres minor muscle.
All lymphatics indigenous the upper limb drain into lymph nodes in the axilla.
The subscapular nerve (upper and lower branches) innervates the subscapularis muscle.
Originate indigenous the posterior cord of the brachial plexus
C5, C6, C7
The suprascapular nerve innervates the infraspinatus and supraspinatus
Originates from the premium trunk of the brachial plexus
Passes with the suprascapular foramen