Forearm | |
---|---|
Details | |
Identifiers | |
Latin | antebrachium |
MeSH | D005542 |
TA98 | A01.1.00.024 |
TA2 | 146 |
FMA | 9663 |
Anatomical terminology |
The forearm is the region of the upper limb between the elbow and the wrist. [1] The term forearm is used in anatomy to distinguish it from the arm, a word which is used to describe the entire appendage of the upper limb, but which in anatomy, technically, means only the region of the upper arm, whereas the lower "arm" is called the forearm. It is homologous to the region of the leg that lies between the knee and the ankle joints, the crus.
The forearm contains two long bones, the radius and the ulna, [2] forming the two radioulnar joints. The interosseous membrane connects these bones. Ultimately, the forearm is covered by skin, the anterior surface usually being less hairy than the posterior surface.
The forearm contains many muscles, including the flexors and extensors of the wrist, flexors and extensors of the digits, a flexor of the elbow (brachioradialis), and pronators and supinators that turn the hand to face down or upwards, respectively. In cross-section, the forearm can be divided into two fascial compartments. The posterior compartment contains the extensors of the hands, which are supplied by the radial nerve. The anterior compartment contains the flexors and is mainly supplied by the median nerve. The flexor muscles are more massive than the extensors because they work against gravity and act as anti-gravity muscles. The ulnar nerve also runs the length of the forearm. [3]
The radial and ulnar arteries and their branches supply the blood to the forearm. These usually run on the anterior face of the radius and ulna down the whole forearm. The main superficial veins of the forearm are the cephalic, median antebrachial and the basilic vein. These veins can be used for cannularisation or venipuncture, although the cubital fossa is a preferred site for getting blood.
The bones of the forearm are the radius (located on the lateral side) and the ulna (located on the medial side)
Proximally, the head of the radius articulates with the capitulum of the humerus and the radial notch of the ulna at the elbow. The articulation between the radius and the ulna at the elbow is known as the proximal radioulnar joint.
Distally, it articulates with the ulna again at the distal radioulnar joint. It forms part of the wrist joint by articulating with the scaphoid at its lateral aspect and with the lunate at its medial aspect.
Proximally, the trochlear notch of the ulna articulates with the trochlea of the humerus and the radial notch articulates with the head of the radius at the elbow. [4]
Distally it forms part of the distal radioulnar joint and also articulates with the wrist. [5]
Compartment | Level | Muscle | E/I | Nerve |
---|---|---|---|---|
Anterior | superficial | flexor carpi radialis | E | median |
Anterior | superficial | palmaris longus | E | median |
Anterior | superficial | flexor carpi ulnaris | E | ulnar |
Anterior | superficial | pronator teres | I | median |
Anterior | superficial (or intermediate) | flexor digitorum superficialis (sublimis) | E | median |
Anterior | deep | flexor digitorum profundus | E | ulnar + median |
Anterior | deep | flexor pollicis longus | E | median |
Anterior | deep | pronator quadratus | I | median |
Posterior | (see below) | brachioradialis | I | radial |
Posterior | superficial | extensor carpi radialis longus | E | radial |
Posterior | superficial | extensor carpi radialis brevis | E | radial |
Posterior | intermediate | extensor digitorum (communis) | E | radial |
Posterior | intermediate | extensor digiti minimi (proprius) | E | radial |
Posterior | superficial | extensor carpi ulnaris | E | radial |
Posterior | deep | abductor pollicis longus | E | radial |
Posterior | deep | extensor pollicis brevis | E | radial |
Posterior | deep | extensor pollicis longus | E | radial |
Posterior | deep | extensor indicis (proprius) | E | radial |
Posterior | deep | supinator | I | radial |
Posterior | deep | anconeus | I | radial |
The forearm can be brought closer to the upper arm (flexed) and brought away from the upper arm (extended) due to movement at the elbow. The forearm can also be rotated so that the palm of the hand rotates inwards (pronated) and rotated back so that the palm rotates outwards (supinated) due to movement at the elbow and the distal radioulnar joint. [5]
A fracture of the forearm can be classified as to whether it involves only the ulna (ulnar fracture), only the radius (radius fracture), or both radioulnar fracture.
For treatment of children with torus fractures of the forearm splinting appears to work better than casting. [7] Genetically determined disorders like hereditary multiple exostoses can lead to hand and forearm deformities. Hereditary multiple exostoses is due growth disturbance of the epiphyses of the radius and ulna, the two bones of the forearm. [8]
The carpal bones are the eight small bones that make up the wrist (carpus) that connects the hand to the forearm. The term "carpus" and "carpal" is derived from the Latin carpus and the Greek καρπός (karpós), meaning "wrist". In human anatomy, the main role of the carpal bones is to articulate with the radial and ulnar heads to form a highly mobile condyloid joint, to provide attachments for thenar and hypothenar muscles, and to form part of the rigid carpal tunnel which allows the median nerve and tendons of the anterior forearm muscles to be transmitted to the hand and fingers.
The ulna or ulnar bone is a long bone in the forearm stretching from the elbow to the wrist. It is on the same side of the forearm as the little finger, running parallel to the radius, the forearm's other long bone. Longer and thinner than the radius, the ulna is considered to be the smaller long bone of the lower arm. The corresponding bone in the lower leg is the fibula.
The humerus is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a rounded head, a narrow neck, and two short processes. The body is cylindrical in its upper portion, and more prismatic below. The lower extremity consists of 2 epicondyles, 2 processes, and 3 fossae. As well as its true anatomical neck, the constriction below the greater and lesser tubercles of the humerus is referred to as its surgical neck due to its tendency to fracture, thus often becoming the focus of surgeons.
The brachioradialis is a muscle of the forearm that flexes the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm. It is attached to the distal styloid process of the radius by way of the brachioradialis tendon, and to the lateral supracondylar ridge of the humerus.
The radial nerve is a nerve in the human body that supplies the posterior portion of the upper limb. It innervates the medial and lateral heads of the triceps brachii muscle of the arm, as well as all 12 muscles in the posterior osteofascial compartment of the forearm and the associated joints and overlying skin.
The median nerve is a nerve in humans and other animals in the upper limb. It is one of the five main nerves originating from the brachial plexus.
In human anatomy, the wrist is variously defined as (1) the carpus or carpal bones, the complex of eight bones forming the proximal skeletal segment of the hand; (2) the wrist joint or radiocarpal joint, the joint between the radius and the carpus and; (3) the anatomical region surrounding the carpus including the distal parts of the bones of the forearm and the proximal parts of the metacarpus or five metacarpal bones and the series of joints between these bones, thus referred to as wrist joints. This region also includes the carpal tunnel, the anatomical snuff box, bracelet lines, the flexor retinaculum, and the extensor retinaculum.
The radius or radial bone is one of the two large bones of the forearm, the other being the ulna. It extends from the lateral side of the elbow to the thumb side of the wrist and runs parallel to the ulna. The ulna is longer than the radius, but the radius is thicker. The radius is a long bone, prism-shaped and slightly curved longitudinally.
The upper limbs or upper extremities are the forelimbs of an upright-postured tetrapod vertebrate, extending from the scapulae and clavicles down to and including the digits, including all the musculatures and ligaments involved with the shoulder, elbow, wrist and knuckle joints. In humans, each upper limb is divided into the shoulder, arm, elbow, forearm, wrist and hand, and is primarily used for climbing, lifting and manipulating objects. In anatomy, just as arm refers to the upper arm, leg refers to the lower leg.
In human anatomy, the extensor pollicis longus muscle (EPL) is a skeletal muscle located dorsally on the forearm. It is much larger than the extensor pollicis brevis, the origin of which it partly covers and acts to stretch the thumb together with this muscle.
The posterior interosseous nerve is a nerve in the forearm. It is the continuation of the deep branch of the radial nerve, after this has crossed the supinator muscle. It is considerably diminished in size compared to the deep branch of the radial nerve. The nerve fibers originate from cervical segments C7 and C8 in the spinal column.
The Galeazzi fracture is a fracture of the distal third of the radius with dislocation of the distal radioulnar joint. It classically involves an isolated fracture of the junction of the distal third and middle third of the radius with associated subluxation or dislocation of the distal radio-ulnar joint; the injury disrupts the forearm axis joint.
Madelung's deformity is usually characterized by malformed wrists and wrist bones and is often associated with Léri-Weill dyschondrosteosis. It can be bilateral or just in the one wrist. It has only been recognized within the past hundred years. Named after Otto Wilhelm Madelung (1846–1926), a German surgeon, who described it in detail, it was noted by others. Guillaume Dupuytren mentioned it in 1834, Auguste Nélaton in 1847, and Joseph-François Malgaigne in 1855.
The anterior interosseous nerve is a branch of the median nerve that supplies the deep muscles on the anterior of the forearm, except the ulnar (medial) half of the flexor digitorum profundus. Its nerve roots come from C8 and T1.
The interosseous membrane of the forearm is a fibrous sheet that connects the interosseous margins of the radius and the ulna. It is the main part of the radio-ulnar syndesmosis, a fibrous joint between the two bones.
The posterior compartment of the forearm contains twelve muscles which primarily extend the wrist and digits. It is separated from the anterior compartment by the interosseous membrane between the radius and ulna.
A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala are often described as having "hands" instead of paws on their front limbs. The raccoon is usually described as having "hands" though opposable thumbs are lacking.
The elbow is the region between the upper arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa, and the lateral and the medial epicondyles of the humerus. The elbow joint is a hinge joint between the arm and the forearm; more specifically between the humerus in the upper arm and the radius and ulna in the forearm which allows the forearm and hand to be moved towards and away from the body. The term elbow is specifically used for humans and other primates, and in other vertebrates it is not used. In those cases, forelimb plus joint is used.
The extrinsic extensor muscles of the hand are located in the back of the forearm and have long tendons connecting them to bones in the hand, where they exert their action. Extrinsic denotes their location outside the hand. Extensor denotes their action which is to extend, or open flat, joints in the hand. They include the extensor carpi radialis longus (ECRL), extensor carpi radialis brevis (ECRB), extensor digitorum (ED), extensor digiti minimi (EDM), extensor carpi ulnaris (ECU), abductor pollicis longus (APL), extensor pollicis brevis (EPB), extensor pollicis longus (EPL), and extensor indicis (EI).
The muscles of the thumb are nine skeletal muscles located in the hand and forearm. The muscles allow for flexion, extension, adduction, abduction and opposition of the thumb. The muscles acting on the thumb can be divided into two groups: The extrinsic hand muscles, with their muscle bellies located in the forearm, and the intrinsic hand muscles, with their muscles bellies located in the hand proper.
{{cite book}}
: CS1 maint: location missing publisher (link)