Alec Titan
The human hand is a complex network of bones, muscles, nerves, tendons, ligaments, and blood vessels. The muscles of the hand can be divided into two groups: extrinsic and intrinsic. The extrinsic muscle groups are the long flexors and extensors, located in the forearm. The intrinsic group comprises smaller muscles located within the hand itself. 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. These muscles extend or open flat the joints in the hand. The extensors are connected in a more complex way than the flexors to the dorsum of the fingers. The primary function of the extensors is to straighten out the digits.
| Characteristics | Values |
|---|---|
| Muscle group | Extrinsic |
| Muscle name | Extensor digitorum (ED) |
| Muscle location | Back of the forearm |
| Tendon location | Four tendons that follow each finger |
| Function | Extend or open flat joints in the hand |
| Innervation | Posterior interosseous artery, a branch of the ulnar artery |
| Blood supply | Posterior interosseous nerve, a branch of the radial nerve |
| Muscle belly location | Forearm |
| Muscle type | Long flexors and extensors |
| Muscle movement | Straighten fingers, hand, and wrist |
Explore related products
What You'll Learn
The extrinsic extensor muscles of the hand
The muscles of the hand are skeletal muscles that enable the movement of the hand and fingers. They are divided into two groups: the extrinsic and intrinsic muscle groups. The extrinsic muscle groups are the long flexors and extensors, and they are called extrinsic because the muscle belly is located outside the hand, in the forearm. The extensors are located on the back of the forearm and are connected to the bones in the hand by long tendons. Their function is to extend or open flat the joints in the hand and fingers.
The EPB inserts into the base of the first phalanx of the thumb, extending and abducting the thumb at the carpometacarpal and MCP joints. The EPL inserts on the base of the distal phalanx of the thumb, using the dorsal tubercle on the radius as a fulcrum to assist the EPB. The index finger and little finger have separate extensors, allowing for more independent movement than the other fingers.
The ECU is supplied by the ulnar artery, while the APL, EPB, EPL, EI, ED, and EDM are supplied by the Posterior interosseous artery, a branch of the ulnar artery. The ECRL and ECRB, on the other hand, receive blood from the radial artery and its deep branch, respectively. The remaining extrinsic hand extensors are supplied by the posterior interosseus nerve, another branch of the radial nerve.
Bruising and Torn Muscles: What Does It Mean?
You may want to see also
Explore related products
The role of the lumbrical muscles
The lumbrical muscles are four short intrinsic muscles of the hand located between the metacarpal bones, deep to the palmar fascia. They are called lumbricals because of their worm-like appearance; the Latin word for earthworm is lumbricidae. The lumbricals are unusual in that they do not attach to bone but rather to tendons. They attach proximally to the tendons of the flexor digitorum profundus and distally to the extensor expansions.
The lumbricals have two functions: flexion at the metacarpophalangeal (MCP) joints and extension at the interphalangeal (IP) joints. The MCP joints are at the knuckle, and the lumbricals help to straighten the fingers at these joints. The lumbricals also contribute to interphalangeal joint extension by acting as deflexors of the proximal interphalangeal joint. These combined movements play a role in complex hand movements, such as holding a pen, and contribute to the hand's general dexterity.
The lumbricals are relatively weak muscles, especially when compared to the interosseous muscle, which has a similar function but is considerably stronger. The high number of muscle spindles in the lumbricals suggests that they play an important role in proprioceptive monitoring of the fingers and sensory feedback, which is important for precision pinch movements and precise manipulation of objects.
The lumbrical muscles of the hand are numbered 1-4 from the most radial/lateral to the most ulnar/medial. Each lumbrical muscle originates from one or two adjacent tendons of the flexor digitorum profundus muscle. Lumbricals 1-2 are usually unipennate, meaning their fibres arise obliquely from one tendon, while lumbricals 3-4 are bipennate, arising from two adjacent tendons.
Popliteus Muscle: Where Does It Attach?
You may want to see also
Explore related products
The thenar muscle group
The abductor pollicis brevis is the most superficial muscle of the thenar group. It originates from the tubercles of the scaphoid and trapezium bones, as well as the flexor retinaculum. The muscle fibers extend laterally and distally, ending in a tendon that inserts onto the lateral aspect of the base of the proximal phalanx. The main function of this muscle is the abduction of the thumb at the first carpometacarpal joint, along with its long counterpart, the abductor pollicis longus muscle. The abductor pollicis brevis also assists in the flexion and opposition of the thumb, allowing for the ability to grasp objects.
The flexor pollicis brevis is the most medial of the thenar muscles. It arises from two muscle heads, the superficial and deep, which are separated by the tendon of the flexor pollicis longus. The superficial head originates from the flexor retinaculum and the tubercle of the trapezium bone, while the deep head originates from the trapezoid and capitate bones. These heads run side by side in a lateral direction to insert onto the base of the proximal phalanx.
The opponens pollicis is the largest of the thenar muscles and lies underneath the other two. It originates from the tubercle of the trapezium and the associated flexor retinaculum, inserting onto the lateral margin of the first metacarpal. The main function of this muscle is to oppose the thumb by medially rotating and flexing the metacarpal on the trapezium, allowing for the precision pinching and power gripping.
In addition to the three muscles of the thenar group, the adductor pollicis is sometimes described alongside the thenar muscles when discussing thumb movements. It is a short, broad, fan-shaped muscle of the palm that arises from two muscular heads: the oblique and transverse. The adductor pollicis muscle produces strong adduction of the thumb at the first carpometacarpal joint and works together with the thenar muscles to produce the opposition of the thumb.
Vanity Muscles: What They Are and How to Train Them
You may want to see also
Explore related products
The hypothenar muscle group
The hypothenar muscles are the three short muscles of the medial (ulnar) palmar compartment of the hand. They are intrinsic muscles of the hand located within the medial side of the palm. They form a noticeable fleshy prominence on the medial side of the palm called the hypothenar eminence. The hypothenar eminence is a muscular protrusion on the medial side of the palm, at the base of the little finger.
The hypothenar eminence muscles, except for palmaris brevis, are innervated by the deep branch of the ulnar nerve (C8, T1). The function of the palmaris brevis muscle is to tighten the palmar aponeurosis and to contribute to the strength of the grip. It is innervated by the superficial branch of the ulnar nerve (C8, T1). The blood supply for the hypothenar eminence comes mainly from the ulnar artery via the superficial palmar arch.
The hypothenar muscles are similar to the thenar muscles in both name and organisation. The thenar muscle group is found at the base of the thumb, forming the muscle bulk on the thumb side of the hand. It is comprised of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis.
Shin Muscle: Location and Function Explained
You may want to see also
Explore related products
The interossei muscles
The dorsal interossei muscles attach to the extensor expansion of the digits, assisting the lumbricals in producing flexion and extension of the metacarpophalangeal and interphalangeal joints. They also allow us to spread our fingers away from each other. The first dorsal interosseous muscle is the largest and originates from the 1st and 2nd hand bones. It forms the contour between the thumb and index finger when looking at the top of the hand. In addition to pulling the index finger away from the middle finger, it also pulls the thumb towards the index finger, providing strength and stability when pinching.
The palmar interossei muscles are smaller than the dorsal interossei and are situated on the palmar surface of the hand in between the metacarpal bones. They are attached to the index, ring, and little fingers. The main function of the palmar interossei is to adduct the fingers in a longitudinal axis, which means moving the fingers towards the middle finger. Specifically, the 1st palmar interosseous pulls the index finger towards the middle finger, while the 2nd and 3rd pull the ring and little fingers towards the middle finger. Functionally, the palmar interossei are antagonists to the dorsal interossei in the metacarpophalangeal joint.
Both the dorsal and palmar interossei are innervated by the deep branch of the ulnar nerve, derived from roots C8 and T1. The palmar interossei receive arterial blood supply from branches of the deep palmar arch, the princeps pollicis artery, the radialis indicis artery, the palmar metacarpal arteries, and the proximal and distal perforating arteries.
Muscle Contusions: Understanding Bruises and Their Treatment
You may want to see also
Frequently asked questions
The muscles in the hand that help with extension are called extrinsic extensor muscles. They are located in the forearm and have long tendons that connect them to the bones in the hand. These muscles 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 primary function of the extensor muscles is to help extend or straighten the fingers, hand, and wrist.
The intrinsic muscles are smaller muscles located within the hand itself. They are responsible for the fine motor functions of the hand. The intrinsic muscle groups are the thenar (thumb) and hypothenar (little finger) muscles, the interossei muscles, and the lumbrical muscles.
The thenar muscle group is responsible for the fine movements of the thumb. It consists of three muscles: the abductor pollicis brevis, the flexor pollicis brevis, and the opponens pollicis. The opponens pollicis is particularly important as it allows us to bring the thumb away from the fingers so that we can grasp objects.
The hypothenar muscle group consists of three muscles: the abductor digiti minimi, the flexor digiti minimi, and the opponens digiti minimi. These muscles form a muscular protrusion on the medial side of the palm, at the base of the little finger. The abductor digiti minimi allows the little finger to pull away from the ring finger, the flexor digiti minimi allows the little finger to bend at the MCP joint, and the opponens digiti minimi allows us to cup our hands by bringing the little finger towards the thumb.
