The forearm of man (and most other Tetrapoda ) consists of two long bones , the ulna ( ulna ) and the radius ( radius ). There is a gap between the two bones ( Spatium interosseum antebrachii ). Both are connected via a belt ( annular ligament radii ) and a solid fibrous plate ( interosseous membrane ) connected to each other.
Two joints are formed between the two forearm bones: the one near the body ( proximal ) and the one remote from the body ( distal ) radial-ulnar joint ( articulatio radioulnaris proximalis and articulatio radioulnaris distalis ). They allow the radius to rotate around the ulna ( pronation and supination ). This turning movement is especially important for complex movements (e.g. climbing, grasping). In mammals with predominantly running movement (e.g. horses , ruminants ), the joint-ulnar joints are regressed and the two bones are fused together (so-called synostosis ).
Muscles and fascia
The muscles of the forearm are divided into two groups according to their location: the muscles that lie on the inside of the loosely hanging arm and thus bend the arm ( flexors ) and the muscles that lie on the outside and stretch the arm ( extensors ). These two groups each consist of two individual layers that go down from the surface of the body.
The forearm fascia ( fascia antebrachii ) separates the individual muscle bellies from one another. In addition, together with the adhesive tape between the two forearm bones ( membrana interossea antebrachii ) , it divides the forearm muscles into a flexor and extensor box . In the area of the wrist, it is reinforced on the back of the hand by transverse fiber strands ( retinaculum extensorum ). This reinforcement serves as a holding device for the extensor tendons. On the palm side, the forearm fascia fuses with the anterior fiber cords ( retinaculum flexorum ), which form the carpal tunnel through which the tendons of the finger flexor muscles run. The biceps brachii muscle provides additional reinforcement of the fascia ( lacertus fibrosus ).
|Superficial layer||Deep layer||Spoke-side (radial) layer||Superficial layer||Deep layer|
|Flexor carpi radialis muscle||Pronator quadratus muscle||Brachioradialis muscle||Extensor carpi ulnaris muscle||Abductor pollicis longus muscle|
|Flexor carpi ulnaris muscle||Flexor pollicis longus muscle||Extensor carpi radialis brevis muscle||Extensor digitorum muscle||Extensor pollicis brevis muscle|
|Flexor digitorum superficialis muscle||Flexor digitorum profundus muscle||Extensor carpi radialis longus muscle||Extensor digiti minimi muscle||Extensor pollicis longus muscle|
|Palmaris longus muscle||Extensor indicis muscle|
|Pronator teres muscle||Supinator muscle|
The forearm receives most of its blood from the upper arm artery ( brachial artery ) coming from the upper arm . This forks in the crook of the elbow into two vascular branches that run to the hand on its spoke side ( arteria radialis ) or ulnar side ( arteria ulnaris ).
The branches of the radial artery in the forearm are
The branches of the ulnar artery in the forearm are
- Arteria recurrens ulnaris anterior and posterior (anterior and posterior recurrent ulnar artery )
Arteria interossea communis (common interosseous artery )
- Arteria interossea anterior (anterior
- Arteria interossea posterior (posterior interosseous artery )
The external vein ( vena cephalica ) on the side of the spokes and the internal vein ( vena basilica ) branch off from the posterior network of the hand . Furthermore, the middle forearm vein ( Vena intermedia antebrachii ) runs on the upper front of the arm. In the crook of the elbow, there is a connection between the outer and inner vein, which is collectively referred to as the middle elbow vein ( Vena mediana cubiti ). This is often used for intravenous injection or to draw blood .
The forearm muscles are innervated primarily by the fibers of the radial, median and ulnar nerves originating from the brachial plexus .
The radial nerve innervates the muscles of the back of the forearm, the extensors and also the skin of parts of the thumb and back of the hand. The median nerve innervates most of the muscles in the flexors and also the skin on the inside of the hand between the thumb and ring finger. The ulnar nerve innervates only the flexor carpi ulnaris muscle and parts of the flexor digitorum profundus muscle and also the skin on the palm and back of the hand between the ring finger and the edge of the hand.
A fracture of the spoke at the end near the hand ( distal radius fracture ) is the most common fracture in the human body at 10 to 25%. Young people are mostly affected by sport and accidents at work or older people by falls. Other fractures of the spoke are the radial shaft fracture , the Galeazzi fracture and the fracture of the radial head . At a fraction of the ulna ( ulnar fracture ) in children is always a Monteggia fracture to think (with dislocation of the radial head combination break). Therefore, not only an X-ray of the fracture area, but always of the entire forearm with an image of the wrist and elbow joint must be made.
Various congenital malformations can occur:
- Radius malalignment in atelosteogenesis , Cornelia de Lange syndrome
- Madelung deformity in dyschondrosteosis Léri Weill
- Radial aplasia in Holt-Oram syndrome
- Radioulnar synostosis in Kampomele dysplasia , Klinefelter syndrome , Williams-Beuren syndrome
- Michael Schünke: Prometheus General Anatomy and Movement System . 2nd Edition. Thieme, Stuttgart, New York 2007.