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The humerus is the bone that forms the upper arm and joins it to the shoulder and forearm. It serves as an attachment to 13 muscles that contribute to the movement of the hand and elbow, and the function of the upper limb. The muscles that attach to the humerus include the supraspinatus, infraspinatus, teres minor, subscapularis, deltoid, triceps brachii, coracobrachialis, brachialis, and brachioradialis. These muscles work together to provide stability, coordination, and a wide range of movements to the upper limb. The humerus also plays a crucial role in transmitting the forces generated by these muscles, facilitating forearm movements, and providing support for soft tissues such as tendons and ligaments.
| Characteristics | Values |
|---|---|
| Number of muscles attached | 13 |
| Muscle attachments | Supraspinatus, infraspinatus, teres minor, subscapularis, deltoid, brachialis, brachioradialis, triceps brachii, anconeus, coracobrachialis, pronator teres, supinator, pectoralis major |
| Muscle groups | Scapulohumeral muscles, anterior compartment muscles, posterior compartment muscles, flexor group, extensor group |
| Function | Coordinated actions of the upper limb, transmission of forces, flexion and extension of the forearm, overall dexterity of the upper limb |
| Nerve supply | Axillary nerve, musculocutaneous nerve, median nerve, ulnar nerve, radial nerve |
| Blood supply | Axillary artery, brachial artery, profunda brachii artery, peri-osteal arteries, nutrient arteries |
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What You'll Learn
- Supraspinatus, infraspinatus, and teres minor muscles attach to the greater tubercle
- Subscapularis muscle attaches to the lesser tubercle
- Teres major attaches to the medial lip of the intertubercular sulcus
- Pectoralis major attaches to the lateral lip of the intertubercular sulcus
- Latissimus dorsi attaches between teres major and pectoralis major
Supraspinatus, infraspinatus, and teres minor muscles attach to the greater tubercle
The supraspinatus, infraspinatus, and teres minor muscles all play a crucial role in the coordinated actions and functionality of the upper limb. These muscles arise from the posterior scapula and insert onto the greater tubercle of the humerus, with the exception of the lower fibres of the teres minor, which insert just below the greater tubercle. Together, they form part of the rotator cuff, a group of four muscles that stabilise the glenohumeral joint.
The supraspinatus muscle is responsible for the first 15 degrees of arm abduction. It is also one of the rotator cuff muscles that can tear, either through acute injury or as a chronic tear over time. Acute tears usually result from falling on an outstretched arm or attempting to lift something heavy. Chronic tears are often secondary to tendinitis or shoulder impingement syndrome.
The infraspinatus muscle originates inferior to the spine of the scapula in the infraspinous fossa of the scapula (shoulder blade). Its tendon inserts into the greater tubercle of the humerus, along with the tendon of the teres minor muscle. The infraspinatus muscle aids in lateral or external rotation of the arm at the shoulder, working together with the teres minor to pull the greater tubercle posteriorly and produce external rotation.
The teres minor muscle arises from the posterior surface of the scapula, directly adjacent to the upper part of its lateral border. It is the smaller of the two "teres muscles", with the teres major being the other. The superior fibres of the teres minor culminate in a tendon that inserts onto the greater tubercle of the humerus. The teres minor is deep to the deltoid muscle, with its medial surface partially covered by the trapezius muscle. It shares its innervation with the deltoid muscle, supplied by the axillary nerve.
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Subscapularis muscle attaches to the lesser tubercle
The subscapularis muscle is a large, powerful, and triangle-shaped muscle. It is the largest and most powerful of the rotator cuff muscles, contributing to internal rotation strength, shoulder adduction and abduction, and active stabilization of the glenohumeral joint. The subscapularis muscle is the only medial, or internal, rotator of all the rotator cuff muscles. It is a multipennate muscle that arises from the anterior surface of the scapula and inserts on the lesser tuberosity, or lesser tubercle, of the humerus.
The subscapularis muscle derives its name from its orientation under the scapula: "sub" meaning under, and "scapula" meaning wing bone. It originates at the subscapular fossa and transitions to a tendon, which inserts on the lesser tubercle of the humerus in front of the joint capsule. The muscle internally rotates and adducts the humerus. The bicep tendon lies underneath the subscapularis tendon in the bicipital groove.
The subscapularis muscle is one of four muscles that compose the rotator cuff apparatus. The other three are the supraspinatus, infraspinatus, and teres minor muscles. The rotator cuff muscles act together to stabilize and steer the humeral head within the glenoid cavity during various movements of the upper limb. Each muscle of the rotator cuff also performs its own specific role, and the precise action of the subscapularis is to internally rotate the arm on the shoulder joint.
The subscapularis muscle plays a crucial role in shoulder movement and helps maintain glenohumeral joint stability. It is important to note that the subscapularis muscle and tendon are less likely to tear than other rotator cuff muscles. However, when there is an injury to the muscle or tendon, it can result in weakness in internal rotation.
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Teres major attaches to the medial lip of the intertubercular sulcus
The teres major is a muscle of the upper limb. It attaches to the scapula and the humerus and is one of the seven scapulohumeral muscles. It is a thick but somewhat flattened muscle. The teres major muscle (from Latin 'teres', meaning 'rounded') is positioned above the latissimus dorsi muscle and assists in the extension and medial rotation of the humerus. This muscle is commonly confused as a rotator cuff muscle, but it is not, because it does not attach to the capsule of the shoulder joint, unlike the teres minor muscle, for example. The teres major muscle originates on the dorsal surface of the inferior angle and the lower part of the lateral border of the scapula.
The teres major attaches to the medial lip of the intertubercular sulcus of the humerus. The intertubercular sulcus is an indentation located between the two tubercles. It is sometimes referred to as the bicipital groove. The long tendon of the biceps brachii and an ascending branch of the anterior circumflex humeral artery are located within the sulcus. The sulcus consists of a lateral lip and a medial lip. The tendon of the pectoralis major muscle attaches to the lateral lip (also known as the crest of the greater tubercle), while the teres major tendon attaches to the medial lip. In addition, the tendon of the latissimus dorsi attaches to the posterior aspect.
The teres major is a medial rotator and adductor of the humerus and assists the latissimus dorsi in drawing the previously raised humerus downwards and backwards (extension, but not hyperextension). It also helps stabilise the humeral head in the glenoid cavity. The function of the teres major is to extend, medially rotate and adduct the humerus. It also plays a role in the stabilization of the humeral head. This muscle is not alone in these functions. The latissimus dorsi also aids in medial rotation and adduction of the humerus. These two muscles function synergistically, with electromyographic studies illustrating that the two muscles activate as one muscle unit.
The humerus serves as an attachment to 13 muscles which contribute to the movements of the hand and elbow, and therefore the function of the upper limb. The humerus, as the longest bone in the upper extremity, serves several crucial functions within the musculoskeletal system. These functions are integral to the overall movement and stability of the upper limb. The humeral head articulates with the glenoid fossa of the scapula and forms the glenohumeral joint, a synovial ball and socket joint. This joint allows movement along multiple planes, including internal and external rotation, abduction and adduction, flexion and extension, and is principally determined by the activation of the rotator cuff muscles (teres minor, subscapularis, supraspinatus, infraspinatus), pectoralis major, and deltoid.
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Pectoralis major attaches to the lateral lip of the intertubercular sulcus
The pectoralis major is the superior-most and largest muscle of the anterior chest wall. It is a thick, fan-shaped muscle that lies underneath the breast tissue and forms the anterior wall of the axilla. The pectoralis major arises from parts of the clavicle, sternum, costal cartilages of the true ribs, and the aponeurosis of the abdominal external oblique muscle. It receives dual motor innervation from the medial pectoral nerve and the lateral pectoral nerve. The muscle's primary functions are flexion, adduction, and internal rotation of the humerus.
The pectoralis major attaches to the lateral lip of the intertubercular sulcus of the humerus. The intertubercular sulcus is an indentation located between the two tubercles of the humerus. It is sometimes referred to as the bicipital groove. The lateral lip of the intertubercular sulcus, also known as the crest of the greater tubercle, serves as the insertion point for the tendon of the pectoralis major muscle.
The relationship between the latissimus dorsi, pectoralis major, and teres major muscles as they insert into the intertubercular sulcus can be remembered using the mnemonic "the lady between two majors". The latissimus dorsi attaches to the floor of the intertubercular sulcus, while the teres major attaches to the medial lip. The deltoid muscle covers the lateral aspect of the greater tubercle, contributing to the normal rounded shape of the shoulder.
The pectoralis major plays a crucial role in the movement and stability of the upper limb. It is involved in flexion, adduction, and medial rotation of the arm at the glenohumeral joint. The muscle's innervation and blood supply make it useful in flap repairs in neck surgery. Additionally, its size and location allow it to provide structural support for soft tissues, such as tendons and ligaments, contributing to the overall stability of the shoulder joint.
The pectoralis major is susceptible to certain conditions, such as intramuscular lipomas, which are rare tumours that may mimic malignant breast tumours. Congenital abnormalities of the pectoralis major can also occur in Poland Syndrome, characterised by the unilateral absence of the muscle.
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Latissimus dorsi attaches between teres major and pectoralis major
The latissimus dorsi is the largest muscle in the upper body. It originates from the lumbar vertebra and pelvis and attaches to the floor of the intertubercular sulcus of the humerus, between the pectoralis major and teres major. The latissimus dorsi tendon inserts under the deltoid on the humerus (upper arm bone), and there may also be a small additional insertion on the scapula (shoulder blade).
The latissimus dorsi is a climbing muscle. With the arms fixed above the head, it raises the trunk upwards with the help of the pectoralis major. It is an important muscle in rowing, swimming, and chopping. It is also active in violent expiration, as it attaches to the ribs. During a cough or sneeze, the muscle can be felt pressing forcibly inward as it acts to compress the thorax and abdomen. The muscle assists in holding the scapula against the thorax during upper limb movements. The attachment of the muscle to the inferior angle of the scapula allows this.
In activities such as walking with crutches, where the humerus becomes the fixed point when standing, the latissimus dorsi pulls the trunk forward relative to the arms, with this action also lifting the pelvis. In people with paralysis of the lower half of the body, the fact that the latissimus dorsi attaches to the pelvis is important. If the latissimus dorsi is short or tight, the back will extend and rotate as the upper extremity is flexed into an overhead position, such as reaching for an object on a high shelf.
The teres major muscle lies superior to the latissimus dorsi, and the adjoining fibres of these two muscles are united but separated by a bursa towards their humeral attachments. As they span the interval between the scapula and proximal humerus, the latissimus dorsi and teres major form the posterior axillary fold. The fold is accentuated when the arm is adducted against resistance. The teres major muscle is located inferior to the teres minor muscle (a rotator cuff muscle), and it has a tendon that inserts on the upper arm near the insertion of the latissimus dorsi and subscapularis. The muscle originates on the inferior angle of the scapula (shoulder blade).
The teres major and pectoralis major muscles are essential for smooth and fluid movements of the upper extremity. The latissimus dorsi, teres major, and pectoralis major work together to adduct, medially rotate, and extend the arm at the glenohumeral joint.
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Frequently asked questions
The humerus serves as an attachment point for 13 muscles, including the supraspinatus, infraspinatus, teres minor, subscapularis, deltoid, triceps brachii, coracobrachialis, brachialis, and brachioradialis.
The muscles attached to the humerus contribute to the movement and stability of the upper limb, including the hand and elbow. They also play a role in transmitting forces generated by the muscles.
The deltoid muscle defines the shoulder contour of the upper limb. The triceps brachii, along with the anconeus, extend the elbow and attach to the posterior side of the humerus. The coracobrachialis, brachialis, and brachioradialis act to flex the elbow. The supraspinatus, infraspinatus, teres minor, and subscapularis form a rotator cuff that stabilizes the glenohumeral joint.
