Layered structure and bony relief
The anatomy of the dorsum of the hand is largely determined by the position of the first metacarpal bone. It is positioned at an angle to the others, creating the widest intermetacarpal space and a prominent interdigital fold. In the first intermetacarpal space, the muscular relief is clearly visualized — the bulk of the first dorsal interosseous muscle (m. interosseus dorsalis I).
Layer characteristics:
- Skin: very thin and mobile. Hair follicles and sebaceous glands are present. The clinical significance of this feature is the potential for furuncle development.
- Subcutaneous tissue: has a loose structure. This is a common site for the accumulation of edema fluid. It is important to remember that even in deep inflammatory processes of the palm, edema often manifests precisely on the dorsal surface.
Superficial vessels and nerves
A dense venous network with numerous anastomoses lies within the subcutaneous tissue. This includes the dorsal digital venous arches (arcus venosi digitales) and intercapillary veins (vv. intercapitulares). The main superficial trunks form from this network and are accompanied by nerves at the border with the dorsal wrist region:
- On the radial side, the cephalic vein (v. cephalica) originates. It is accompanied by the superficial branch of the radial nerve (ramus superficialis n. radialis), which innervates the lateral part of the dorsum of the hand.
- On the ulnar side, the basilic vein (v. basilica) is formed. Running alongside it is the dorsal branch of the ulnar nerve (ramus dorsalis manus n. ulnaris), which provides innervation to the medial part.
The terminal branches of the nerves on the hand are the dorsal digital nerves (nn. digitales dorsales).
Arterial blood supply
Blood supply to the dorsum of the hand is provided by the radial artery and the dorsal carpal network.
Radial artery (a. radialis) Emerging from the anatomical snuffbox, the artery lies in the first intermetacarpal space directly on the first dorsal interosseous muscle. Here, it gives off an important branch — the first dorsal metacarpal artery (a. metacarpalis dorsalis prima). This branch gives rise to three smaller arteries supplying the I and II digits and serves as an independent source of blood supply to the thumb (independent of the superficial arch). Afterward, the main trunk of the radial artery pierces the muscle, enters the palm, and participates in the formation of the deep palmar arterial arch. Additionally, the dorsal carpal branch (ramus carpeus dorsalis) arises from the radial artery.
Dorsal carpal network (rete carpale dorsale) It gives rise to the dorsal metacarpal arteries (aa. metacarpales dorsales), which course into the second, third, and fourth intermetacarpal spaces. At the base of the fingers, each of them divides into dorsal digital arteries (aa. digitales dorsales).
Extensor tendons
Tendons (tendines mm. extensorum) pass from the forearm region onto the hand beneath a specialized retinaculum — the extensor retinaculum (retinaculum mm. extensorum). They can be categorized by their areas of insertion:
- To the thumb: tendons of the extensor pollicis longus and extensor pollicis brevis (tendo m. extensoris pollicis longi and tendo m. extensoris pollicis brevis).
- To the radial side of the wrist: tendons of the extensor carpi radialis longus and brevis (tendo m. extensoris carpi radialis longi and brevis).
- To the digits (II–V): tendons of the extensor digitorum communis (tendines m. extensoris digitorum communis) and the tendon of the extensor indicis proprius (tendo m. extensoris indicis proprii).
- To the ulnar side of the wrist: tendon of the extensor carpi ulnaris (tendo m. extensoris carpi ulnaris).
Briefly: answers to topical questions
Which nerves provide sensory innervation to the skin of the dorsum of the hand?
Sensory innervation of the skin of the dorsum of the hand is provided by branches of the radial, ulnar, and median nerves.
- Superficial branch of the radial nerve (ramus superficialis n. radialis) — innervates the lateral part of the dorsum of the hand, the skin of digits I, II, and the radial side of digit III.
- Dorsal branch of the ulnar nerve (ramus dorsalis n. ulnaris) — innervates the medial part of the dorsum of the hand, the skin of digits V, IV, and the ulnar side of digit III.
- Median nerve (n. medianus) — innervates the distal phalanges of digits I, II, III, and the radial half of digit IV on the dorsal side.
The terminal branches on the digits are the dorsal digital nerves (nn. digitales dorsales).
What fascial spaces and fascial compartments are distinguished on the dorsum of the hand?
Two main spaces are distinguished on the dorsum of the hand, arranged in layers:
- Subcutaneous tissue — loose, almost devoid of fat; contains the venous network and branches of the superficial branches of the radial and ulnar nerves.
- Dorsal subaponeurotic space — located between the fascia of the hand (fascia dorsalis manus) and the deep fascia; laterally bounded by the attachment sites of the hand fascia to the II and V metacarpal bones. It contains the extensor tendons of the digits.
Which extensor tendons pass to digits II through V?
The tendons of the common and proper extensors pass to digits II through V on the dorsum of the hand.
- Extensor digitorum tendons (tendines m. extensoris digitorum communis) — course to all digits except the thumb (digits II to V).
- Extensor indicis tendon (tendo m. extensoris indicis proprii) — courses to digit II.
- Extensor digiti minimi tendon (tendo m. extensoris digiti minimi) — runs to digit V and joins the tendon of the common extensor.
The presence of proper extensors provides independent movement for the index finger and little finger.
Which arteries participate in the formation of the dorsal carpal network (rete carpale dorsale)?
The dorsal carpal network (rete carpale dorsale) is formed by branches of the major forearm arteries that anastomose with one another:
- Dorsal carpal branch of the radial artery (ramus carpeus dorsalis a. radialis) — arises from the radial artery in the anatomical snuffbox.
- Dorsal carpal branch of the ulnar artery (ramus carpalis dorsalis a. ulnaris) — pierces the fascia of the hand and enters the subcutaneous tissue of the dorsal wrist.
- Anterior interosseous artery (a. interossea anterior) — passes into the posterior compartment through an opening in the interosseous membrane and also participates in the formation of this network.
The radial nerve travels alongside the cephalic vein, while the ulnar nerve travels alongside the basilic vein.
Class and exam questions
Where is the projection of the metacarpophalangeal joint space located?
The joint space is projected 8–10 mm distal to the metacarpal heads.
Why is edema often visible on the dorsum of the hand during palmar inflammation?
This is due to the layered structure: the subcutaneous tissue of the dorsum of the hand is very loose, which is why edema fluid easily accumulates here.
Which vessel is an independent source of blood supply to the thumb?
The first dorsal metacarpal artery (a. metacarpalis dorsalis prima), which branches off from the radial artery in the first intermetacarpal space.
What else to study on this topic
- Anatomical snuffbox: boundaries and contents
- Formation of the deep palmar arterial arch
- Topography of the extensor retinaculum (retinaculum mm. extensorum)
- Dorsal carpal network (rete carpale dorsale): origins of formation
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