Segments of the free upper limb
The free part of the upper limb (pars libera membri superioris) is anatomically divided into three consecutive segments.
- The proximal segment is the arm (brachium), the skeleton of which is represented by the humerus. It is important to remember anatomical terminology: the arm is the segment from the shoulder to the elbow joint, whereas the area above is called the shoulder girdle.
- The middle segment is the forearm (antebrachium), extending from the elbow joint to the wrist. It is formed by the radius and ulna.
- The distal segment is the hand (manus), consisting of the carpal bones, metacarpal bones, and phalanges of the fingers.
Blood from the bones, joints, and muscles of these segments is drained by deep veins, which are venae comitantes (vv. comitantes) accompanying the arteries (two veins per one artery).
Anatomy of the humerus
The humerus (humerus) is divided into the proximal end, diaphysis, and distal end.
In the proximal part, there is the head of the humerus, followed by the anatomical neck. Lower down lies the surgical neck. At the same level, the greater and lesser tubercles project, with the intertubercular sulcus running between them.
The diaphysis (shaft of the humerus) contains the deltoid tuberosity and the radial groove.
The distal end is represented by the condyle of the humerus, which includes the capitulum and the trochlea. Three fossae are located in this region: the olecranon fossa, coronoid fossa, and radial fossa. The lateral and medial epicondyles are located on the sides. The groove for the ulnar nerve runs along the medial epicondyle.
Bones of the Forearm
The skeleton of the forearm consists of two bones, each having its own articular surfaces and processes.
The radius (radius) at its proximal end features a head with an articular facet and articular circumference, as well as a neck. The shaft exhibits an interosseous border and the radial tuberosity. The distal end includes the styloid process, ulnar notch, and carpal articular surface.
The ulna (ulna) in its proximal part features the olecranon and coronoid processes, as well as the trochlear notch. The radial notch and ulnar tuberosity are also located here. At the distal end (head of the ulna), there is an articular circumference and a styloid process.
Skeleton of the hand
The bones of the hand (ossa manus) are divided into three groups:
- Carpal bones: arranged in two rows. The proximal row includes the scaphoid, lunate, triquetrum, and pisiform bones. The distal row consists of the trapezium, trapezoid, capitate, and hamate bones.
- Metacarpal bones: each of them has a base, body, and head.
- Phalanges of the hand: proximal, middle, and distal phalanges are distinguished. Their structure also includes a base, body, and head.
Venous drainage from the upper limb
Deep veins (vv. profundae membri superioris) drain blood from the bones, muscles, and joints.
Superficial and deep palmar venous arches are formed in the hand. The deep arch (arcus venosus palmaris profundus) receives paired palmar metacarpal veins and small vessels from the carpal bones and ligaments.
In the forearm, the veins continue into the ulnar (vv. ulnares) and radial (vv. radiales) veins, which merge in the cubital fossa into the brachial veins (vv. brachiales). The main collector of the upper limb is the axillary vein (v. axillaris), located from the lower border of the pectoralis major muscle (m. pectoralis major) to the 1st rib.
Class and exam questions
What is the anatomical difference between the arm (brachium) and the shoulder girdle?
In anatomy, the arm (brachium) is the segment of the upper limb from the shoulder joint to the elbow joint, with the humerus as its bony framework. The region located above the arm is called the shoulder girdle (nadplechye).
What anatomical structures are located at the distal end of the humerus?
It contains the condyle (including the trochlea and capitulum), lateral and medial epicondyles, as well as three fossae: olecranon, coronoid, and radial. The groove for the ulnar nerve runs on the medial epicondyle.
What parts does each bone of the digits of the hand consist of?
Each phalanx of the hand, like the metacarpal bones, has three main anatomical parts: the base, body, and head.
Where does blood drain from the bones and deep structures of the upper limb?
Blood from the bones and joints is collected by deep venae comitantes. In the forearm, these are the ulnar and radial veins, which merge into the brachial veins and then empty into the axillary vein—the main collector of the limb.
What else to study on this topic
- Superficial veins of the forearm: variations of the course of the median antebrachial vein (v. mediana antebrachii) and its branches
- Anastomoses of the deep palmar venous arch with the veins of the dorsal hand
- Topography of the axillary vein (v. axillaris) and its main tributaries
- Connection of the superficial veins (v. cephalica and v. basilica) with the deep venous arches
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