Anterior Forearm Flashcards
The head of the radius articulates with the radial notch of the ulna and is held in position by the annular ligament. Also, it articulates with the capitulum of the humerus.
The interosseous membrane connects the radius and the ulna.
The olecranon process articulates with the trochlea of the humerus.
Both the ulna and radius have a styloid process at their distal ends, with the styloid process of the radius extending more distally than that of the ulna.
At its distal end the radius articulates with the scaphoid and lunate carpal bones, while the ulna is separated from the carpal bones by an articular disc.
The medial cutaneous nerve of the forearm arises from the medial cord of the brachial plexus.
The lateral cutaneous nerve of the forearm is a sensory nerve and a continuation of the musculocutaneous nerve that supplied the flexor muscles of the arm.
The medial cutaneous nerve of the forearm arises from the medial cord of the brachial plexus.
The lateral cutaneous nerve of the forearm is a sensory nerve and a continuation of the musculocutaneous nerve that supplied the flexor muscles of the arm.
Brachioradialis
Origin: lateral supracondylar ridge of the humerus
Innsertion: radius, proximal to the styloid process.
Innervation: radial nerve proximally. The radial nerve divides into a superficial and deep branch immediately after piercing the lateral intermuscular septum. The superficial branch is sensory and continues distally beneath the brachioradialis muscle, while the deep branch of the radial nerve pierces the supinator muscle and supplies motor fibers to extensor muscles of the forearm.
The flexor retinaculum is a thickening of the deep fascia of the forearm and serves to hold the flexor muscles in the carpal tunnel.
Carpal tunnel – palmar and transverse carpel ligament
Name the five muscles originate from the medial epicondyle (superficial group) and the nerves that innervated each one.
Four of these muscles are supplied by the median nerve. Only the flexor carpi ulnaris is supplied by the ulnar nerve.
The five muscles of the superficial group all have an origin from the medial epicondyle.
- The pronator teres takes origin from the medial epicondyle of the humerus (humeral head) as well as from the ulna (ulnar head). The muscle attaches distally on the radius and serves to pronate (and flex) the forearm.
- The flexor carpi radialis continues distally to attach to the base of the 2nd metacarpal.
- The palmaris longus attaches distally to the palmar aponeurosis.
- The f_lexor carpi ulnaris_ attaches distally to the base of the 5th metacarpal.
- The flexor digitorum superficialis is sometimes placed in an intermediate layer because it is below the other muscles. It takes origin from the medial epicondyle, the coronoid process of the ulna, and the radius. It inserts on the middle phalange of the medial four digits (fingers).
Only the tendons (four) of the flexor digitorum superficialis pass through the carpal tunnel.
The palmaris longus is absent in about 14% of individuals – see whether you have a palmaris longus.
The median nerve passes between the tendon of the flexor carpi radialis and the palmaris longus.
The median nerve passes through the carpal tunnel with the tendons of the flexor digitorum superficialis.
Flexor digitorum profundus takes origin from the proximal portions of the anterior surface of the ulna and interosseous membrane. The tendons of the muscle pass through the carpal tunnel and hand to insert on the distal phalanx of the digits 2 – 5. The median nerve (anterior interosseous nerve) innervates that portion of the muscle that sends its tendons to the 2nd and 3rd digits, while the ulnar nerve innervates that portion of the muscle terminating on the distal phalanx of the 4th and 5th digits.
The flexor pollicis longus takes origin from the anterior radial surface and adjacent interosseous membrane and attaches distally on the terminal phalanx of the thumb.
The pronator quadratus attaches the distal radius and ulna, and serves to pronate the radius. Both the FPL and pronator quadratus are innervated by the median nerve.
The flexor pollicis longus takes origin from the anterior surface of the radius. Its tendon passes through the carpal tunnel to insert on the base of the distal phalanx of the thumb. It is innervated by the anterior interosseous nerve, a branch of the median nerve.
The pronator quadratus is located in the distal forearm and is attached to the ulna and radius. Like the other deep muscles, it is innervated by the anterior interosseous nerve, a branch of the median nerve.
Pronator syndrome
Compression of the median nerve by the pronator teres muscle is called pronator syndrome. The onset of symptoms is usually after repetitive elbow motions such as chopping wood, sculling, and cleaning fish. Clinically, pronator syndrome presents as a chronic aching sensation localized to the forearm with pain occasionally radiating into the elbow.
Note that the median nerve passes between the two heads of origin of the pronator teres, and may become compressed by hypertrophy of the muscle, causing pain in the proximal forearm.
The ulnar nerve is located deep to the flexor carpi ulnaris and innervates one and one-hlf muscles in the forearm – the flexor carpi ulnaris and the ulnar (medial half) of the flexor digitorum profundus.
The brachial artery divides in the cubital fossa into the ulnar and radial arteries. The radial artery goes to the radial side and runs under the brachioradialis with the superficial branch of the radial nerve. It is present in the region of the wrist lateral to the tendon of flexor carpi radialis. It is a common site for taking the pulse.
The ulnar branch of the brachial artery passes posteriorly to go deep to the superficial muscles of the forearm. A number of branches arise from the artery, a major one being the common interosseous artery. The ulnar artery passes between the superficial and deep muscles to join the ulnar nerve as they pass distally to enter the palm of the hand. The common interosseous artery divides into an anterior and posterior interosseous artery. The anterior interosseous artery joins the anterior interosseous nerve and passes distally between the flexor digitorum profundus and the flexor pollicis longus. The posterior interosseous artery passes above the interosseous membrane to supply blood to the posterior compartment (extensor compartment) of the forearm.
The posterior interosseous artery enters the posterior compartment of the forearm between the supinator and abductor pollicis longus muscles.
