Maximus Gage
The lesser tubercle is a small, bony projection located at the proximal end of the humerus bone in the upper arm. Despite its size, it is more prominent than the greater tubercle, situated anteriorly and medially. The lesser tubercle plays a crucial role in muscle attachment, specifically providing insertion for the subscapularis muscle, which works to medially or internally rotate the humerus. Additionally, the crest of the lesser tubercle forms the medial lip of the bicipital groove, facilitating the insertion of the teres major and latissimus dorsi muscles. Understanding the anatomy of the lesser tubercle is important for grasping the overall structure and function of the humerus and the surrounding musculature.
| Characteristics | Values |
|---|---|
| Location | The lesser tubercle is situated in front of the humerus and is directed medially and anteriorly. |
| Size | The lesser tubercle is smaller than the greater tubercle. |
| Prominence | The lesser tubercle is more prominent than the greater tubercle. |
| Muscle Attachment | The lesser tubercle provides insertion for the subscapularis muscle, which works to medially or internally rotate the humerus. |
| Additional Muscles | The teres major, latissimus dorsi, and coracobrachialis muscles are also associated with the lesser tubercle. |
| Function | The lesser tubercle, along with the greater tubercle, forms the proximal part of the shaft of the humerus. |
| Anatomy | The lesser tubercle is separated from the greater tubercle by the bicipital groove (intertubercular groove), which lodges the tendon of the biceps brachii muscle. |
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What You'll Learn
The subscapularis muscle
The subscapularis tendon is located approximately 3 to 5 cm beneath the surface, which can make it challenging to examine using ultrasonography. However, a highly penetrative 5 MHz linear applicator can facilitate a detailed examination. The Gerber Lift-off test, also known as Gerber's Test, is a clinical test used to examine the subscapularis muscle for tears. Positive results on the bear-hug and belly press tests also indicate significant tearing of the subscapularis.
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Teres major muscle
The teres major muscle is a thick but somewhat flattened muscle of the upper limb. It is one of the seven scapulohumeral muscles that act around the glenohumeral joint to facilitate shoulder movement. It is sometimes called "lat's little helper" because of its synergistic action with the latissimus dorsi. The teres major is positioned above the latissimus dorsi muscle and assists in the extension and medial rotation of the humerus. The muscle originates on the dorsal surface of the inferior angle and the lower part of the lateral border of the scapula. The fibres of the teres major insert into the medial lip of the intertubercular sulcus of the humerus. The tendon, at its insertion, lies behind that of the latissimus dorsi, from which it is separated by a bursa, the two tendons being, however, united along their lower borders for a short distance.
The teres major muscle is supplied primarily by the lower subscapular nerve and additionally by the thoracodorsal nerve (middle subscapular nerve). These are distal to the upper subscapular nerve. The nerves that innervate teres major consist of fibres from spinal nerves C5-C8. The teres major muscle is vascularised by the thoracodorsal branch of the subscapular artery and the posterior circumflex humeral artery.
The main function of the teres major muscle is to produce movements of the humerus at the glenohumeral joint. By contracting, it pulls the anterior surface of the humerus medially towards the trunk (internal rotation). It can also extend the arm from a flexed position and provides support in the adduction of the shoulder. Along with the pectoralis major and latissimus dorsi muscles, the teres major can pull the trunk superiorly (through adduction) when its humeral attachment is fixed. This is why it is also referred to as the climbing muscle. Additionally, it contributes to the stabilisation of the shoulder joint.
Isolated teres major injuries are rare but are almost exclusively encountered in professional and high-level recreational athletes, particularly baseball pitchers. The main symptom of a teres major tear is a sudden sharp pain in the shoulder, upper arm and armpit. This usually arises if the muscle is not rested and no treatment is carried out. Most cases of teres major injuries heal successfully without surgery. Treatment includes a proper warm-up before exercising, flexibility and strengthening exercises, and avoiding certain exercises that may cause pain.
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Latissimus dorsi muscle
The latissimus dorsi is a large, flat muscle on the back that stretches to the sides, behind the arm, and is partly covered by the trapezius on the back near the midline. The muscle's name in Latin means "broadest [muscle] of the back". The pair of muscles are commonly referred to as "lats", especially among bodybuilders. The latissimus dorsi is responsible for extension, adduction, transverse extension (also known as horizontal abduction or horizontal extension), flexion from an extended position, and (medial) internal rotation of the shoulder joint. It also plays a role in the extension and lateral flexion of the lumbar spine.
The latissimus dorsi is an extrinsic back muscle and belongs to the superficial layer of the extrinsic back muscles, along with the levator scapulae, trapezius, and rhomboid muscles. It is supplied predominantly by the thoracodorsal artery, a continuation of the subscapular artery, which is a branch of the third part of the axillary artery. The muscle also receives blood supply from the dorsal perforating branches of the inferior three posterior intercostal arteries and the superior three lumbar arteries. The thoracodorsal nerve, a branch of the posterior cord of the brachial plexus (C6 to C8, with C7 predominant), provides innervation to the latissimus dorsi.
The latissimus dorsi works together with the teres major and pectoralis major muscles to perform actions of the upper extremity. These muscles adduct, medially rotate, and extend the arm at the glenohumeral joint. The latissimus dorsi also assist in depression of the arm with the other two muscles. It adducts, extends, and internally rotates the shoulder. The muscle is also active in moving the trunk forward and upward when the upper extremities are fixed overhead, as in climbing or performing a chin-up.
The latissimus dorsi is a potential source of muscle for breast reconstruction surgery after mastectomy or to correct pectoral hypoplastic defects such as Poland's syndrome. Tightness in this muscle can cause chronic shoulder and back pain. Training the latissimus dorsi can provide benefits for everyday movement and life, not just for bodybuilders.
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Biceps brachii muscle
The biceps brachii muscle, or simply "biceps", is a large, thick muscle on the upper arm's ventral portion. The muscle is composed of two heads: a short head and a long head. The short head is sometimes referred to as "caput breve", while the long head is also called "caput longum". The short head originates from the apex of the coracoid process of the scapula, while the long head originates from the supraglenoid tubercle of the scapula.
The biceps brachii is one of the chief muscles of the arm. Its origin at the scapula and its insertion into the radius mean it can act on both the shoulder joint and the elbow joint, allowing it to participate in a few movements of the arm. In the shoulder joint, the long head pulls the arm away from the trunk (abduction) and turns it inwards (inward rotation), while the short head pulls the arm back towards the trunk (adduction). When both heads contract simultaneously, it leads to an arm bend (flexion). In the elbow joint, the muscle bends the forearm (flexion) and rotates it outwards (supination). The supination is most powerful in a flexed elbow.
The biceps brachii is involved in various tasks such as lifting, sports involving throwing and racket use, and gesturing. As a result, biceps tendinopathy is a common condition seen in this muscle, often caused by muscle overuse, trauma, or repetitive activity. One example is the "popeye deformity", common in baseball pitchers, which arises from a ruptured long head tendon due to chronic wear and tear. Consequently, the muscle forms a ball at the anterior mid-arm.
The biceps brachii muscle is supplied by the musculocutaneous nerve (C5-C7), a branch of the brachial plexus. The primary arterial blood supply for the biceps brachii muscle comes from the muscular branches of the brachial artery.
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Coracobrachialis muscle
The coracobrachialis muscle is a slender muscle located in the upper medial part of the arm, within the anterior compartment of the arm. It is not one of the most prominent arm muscles and does not play a significant role in moving the arm. However, it can become tight from certain activities and can be a hidden source of shoulder or arm pain.
The coracobrachialis muscle originates from the deep surface of the coracoid process of the scapula and inserts onto the middle of the medial aspect of the body of the humerus. It is innervated by the musculocutaneous nerve, which arises from the anterior division of the upper trunk (C5-C7). The nerve runs from the shoulder down the arm and can refer pain from one area to another. The muscle is perforated by the musculocutaneous nerve, which also supplies the biceps brachii and brachialis muscles.
The main function of the coracobrachialis muscle is to produce flexion and adduction of the arm at the shoulder joint. It helps to bend the arm and pull it towards the trunk. It also assists in internal rotation, bringing the arms inward towards the body, and provides stability to the shoulder by holding the upper arm bone within the shoulder socket during rotation.
The coracobrachialis muscle can be strained or injured by overuse, particularly in athletes and individuals with jobs involving repetitive tasks. Symptoms of overuse or injury include pain in the arm and shoulder, radiating down to the back of the hand. In severe cases, the musculocutaneous nerve can become trapped, causing disturbances in sensation to the skin on the forearm. However, rupture of the coracobrachialis muscle is extremely rare and typically only occurs due to direct trauma or indirect forces.
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Frequently asked questions
The subscapularis muscle attaches to the lesser tubercle. The teres major and latissimus dorsi muscles attach to the crest of the lesser tubercle.
The subscapularis muscle works to medially, or internally, rotate the humerus.
The lesser tubercle is situated in front of the humerus and is directed medially and anteriorly.
