Position in the upper limb skeleton
The free part of the upper limb (pars libera membri superioris) is anatomically divided into three key segments:
- Arm (brachium) — its bony framework consists exclusively of the humerus (humerus).
- Forearm (antebrachium) — here the skeleton is represented by two bones: the ulna (ulna) and radius (radius).
- Hand (manus) — formed by multiple carpal, metacarpal, and phalangeal bones (ossa manus).
Like a typical long tubular bone, the humerus has a central part — the diaphysis (shaft), and two thickened ends: the proximal (closest to the trunk) and the distal (furthest from the trunk) epiphysis.
Proximal epiphysis
The upper end of the bone participates in the formation of the shoulder joint. It features a smooth, hemispherical head of humerus (caput humeri), which serves as an articular surface for articulation with the scapula.
Just along the edge of the articular surface of the head runs a narrow groove — the anatomical neck (collum anatomicum), corresponding to the metaphyseal zone. Lateral to it are two prominences for muscle attachment:
- Lesser tubercle (tuberculum minus) — directed medially.
- Greater tubercle (tuberculum majus) — occupies a lateral position.
Extending downward from each of the tubercles are respective crests: the crest of the greater tubercle (crista tuberculi majoris) and the crest of the lesser tubercle (crista tuberculi minoris). The space between these elevations forms the intertubercular sulcus (sulcus intertubercularis).
Slightly below the tubercles, the bone narrows noticeably. This site is called the surgical neck (collum chirurgicum) — it is here that fractures most commonly occur.
Shaft of humerus
The diaphysis, or shaft of the humerus (corpus humeri), has a cylindrical shape in its upper part and becomes triangular inferiorly. Three surfaces are clearly distinguishable on it:
- Posterior surface (facies posterior)
- Anteromedial surface (facies anteromedialis)
- Anterolateral surface (facies anterolateralis)
In the middle third of the anterolateral surface lies the rough deltoid tuberosity (tuberositas deltoidea). Below this tuberosity, spiraling around the bone, runs the radial groove (sulcus nervi radialis), which lodges the corresponding nerve.
Distal epiphysis
The lower end of the bone is widened and forms the condyle of humerus (condylus humeri), covered with articular cartilage for articulation with the forearm bones. The condyle consists of two parts:
- Laterally located is the spherical capitulum of humerus (capitulum humeri) — for articulation with the radius.
- Medially lies the cylindrical trochlea of humerus (trochlea humeri) — for the ulna.
Flanking the condyle are the epicondyles — medial (epicondylus medialis) and lateral (epicondylus lateralis). Extending upward from them along the diaphysis are the respective crests (crista epicondyli medialis et lateralis). On the posterior aspect of the medial epicondyle, the sulcus for ulnar nerve (sulcus nervi ulnaris) is clearly visible.
To ensure a full range of motion in the elbow joint, special depressions are provided on the distal epiphysis:
- Anteriorly above the capitulum — the radial fossa (fossa radialis).
- Anteriorly above the trochlea — the coronoid fossa (fossa coronoidea).
- Posteriorly, above the condyle — the extensive and deep olecranon fossa (fossa olecrani).
Determining bone side (right or left)
During practical anatomy classes, it is important to be able to quickly determine whether a bone belongs to the right or left side of the body. The following algorithm is used for this:
- Up/Down: orient the bone so that the proximal epiphysis with the rounded head is at the top, and the distal epiphysis (with the condyle) is at the bottom.
- Front/Back: locate the deep olecranon fossa on the lower epiphysis — it is always located on the posterior surface. The smaller radial and coronoid fossae must face forward.
- Lateral/Medial: the head of the humerus (caput humeri), lesser tubercle, trochlea of the condyle, and larger medial epicondyle always point medially (toward the torso). The greater tubercle, deltoid tuberosity, and capitulum face laterally (outward).
Briefly: answers to topical questions
Which muscles attach to the greater tubercle of the humerus?
The tendons of three rotator muscles of the shoulder joint attach to the greater tubercle of the humerus.
- Supraspinatus muscle (m. supraspinatus) — attaches to the upper part of the tubercle.
- Infraspinatus muscle (m. infraspinatus) — attaches inferior to the supraspinatus muscle.
- Teres minor muscle (m. teres minor) — attaches inferior to the infraspinatus muscle.
What passes through the intertubercular sulcus of the humerus?
The tendon of the long head of the biceps brachii passes through the intertubercular sulcus of the humerus, located between the greater and lesser tubercles; sources also indicate the intertubercular synovial sheath.
- Tendon of the long head of the biceps brachii (tendo m. bicipitis brachii, caput longum) — located in the intertubercular sulcus.
- Intertubercular synovial sheath (vagina mucosum intertubercularis) — indicated in the topography of the shoulder joint.
Which fossae are located on the distal epiphysis of the humerus and which processes enter them during movements?
Three fossae are located on the distal epiphysis of the humerus.
- Coronoid fossa (fossa coronoidea) — located anteriorly above the trochlea; it accommodates the coronoid process of the ulna during flexion in the elbow joint.
- Radial fossa (fossa radialis) — located anteriorly above the capitulum; intended for the head of the radius during flexion.
- Olecranon fossa (fossa olecrani) — located posteriorly above the trochlea.
Which nerve can be damaged in a fracture of the surgical neck of the humerus?
The axillary nerve can be damaged in a fracture of the surgical neck of the humerus.
- Axillary nerve (n. axillaris) — winds around the surgical neck posteriorly, exiting through the quadrangular space.
Its injury occurs due to entrapment by bone fragments or compression within the callus, which leads to paresis of the deltoid muscle and the inability to abduct the arm to the horizontal level.
Which blood vessels run in the radial groove along with the nerve of the same name?
The deep artery of the arm and its accompanying veins run in the radial groove (humeral muscular canal) along with the radial nerve.
- Deep artery of the arm (a. profunda brachii) — a major branch of the brachial artery that spirally winds around the posterior surface of the bone.
- Accompanying veins (vv. profundae brachii) run together with the artery and nerve.
Which borders (margo) are distinguished on the shaft of the humerus?
Three borders are distinguished on the shaft of the humerus, giving its distal part a triangular shape.
- Anterior border (margo anterior).
- Medial border (margo medialis) — inferiorly, it is a continuation of the medial supracondylar ridge.
- Lateral border (margo lateralis) — inferiorly, it is a continuation of the lateral supracondylar ridge.
To avoid confusing the fossae on the distal epiphysis, remember the rule "fossae anteriorly, depression posteriorly": two small fossae (radial and coronoid) face anteriorly, while one deep fossa (olecranon fossa) faces strictly posteriorly.
Class and exam questions
Why did the surgical neck get its name?
The surgical neck is the constriction of the bone immediately below the tubercles of the proximal epiphysis. It received its name because the bone is thinnest at this site, and fractures requiring trauma surgeon intervention most frequently occur here.
With which bones does the humerus articulate?
By its proximal epiphysis (head), it articulates with the scapula. By its distal epiphysis, it connects with the two bones of the forearm: the capitulum articulates with the radius, and the trochlea articulates with the ulna.
Which nerves can be injured in fractures of the humerus?
According to the structure of the bone, two important nerves run in close proximity to it: the radial nerve (in the spiral groove on the diaphysis) and the ulnar nerve (in the groove on the posterior surface of the medial epicondyle).
What else to study on this topic
- Orientation of the surfaces of the humeral shaft
- Detailed structure of the humeral condyle
- Nerve grooves and their topography
- Differences between the anatomical and surgical necks
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