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Hand: Anatomy

Hand: Anatomy

The hand constitutes the distal part of the upper limb and provides the fine, precise movements needed in activities of daily living. It consists of 5 metacarpal bones and 14 phalanges, as well as numerous muscles innervated by the median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion and ulnar nerves. The muscles of the hand are classified as extrinsic ( forearm Forearm The forearm is the region of the upper limb between the elbow and the wrist. The term "forearm" is used in anatomy to distinguish this area from the arm, a term that is commonly used to describe the entire upper limb. The forearm consists of 2 long bones (the radius and the ulna), the interosseous membrane, and multiple arteries, nerves, and muscles. Forearm: Anatomy-based) or intrinsic (hand-based) depending on the location of the muscle belly. These muscles are also grouped by area or type: thenar, hypothenar, lumbricals, and interossei.

Last updated: 15 Mar, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Contents

Bones of the Hand

The bones of the hand consist of the following:

  • Metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy
    • There are 5 metacarpal bones corresponding to each of the fingers.
    • The proximal portion is called the base.
    • The middle portion is called the shaft.
    • The distal portion is called the head.
  • Phalanges 
    • Digits 2–5 have 3 phalanges: proximal, middle, and distal.
    • The 1st digit or the thumb only has 2 phalanges: proximal and distal.
  • Hand anterior view

    Anterior view of the hand and carpus, featuring the carpal bones Carpal bones The eight bones of the wrist: scaphoid bone; lunate bone; triquetrum bone; pisiform bone; trapezium bone; trapezoid bone; capitate bone; and hamate bone. Carpal Tunnel Syndrome, metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy, and phalanges

    Image by BioDigital, edited by Lecturio
  • Hand posterior view

    Posterior view of the hand and carpus, featuring the carpal bones Carpal bones The eight bones of the wrist: scaphoid bone; lunate bone; triquetrum bone; pisiform bone; trapezium bone; trapezoid bone; capitate bone; and hamate bone. Carpal Tunnel Syndrome, metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy, and phalanges

    Image by BioDigital, edited by Lecturio

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5:09
Hand – Bones and Surface Anatomy of Upper Limb
8:48
Wrist and Hand

Joints of the Hand

The joints of the hand and fingers consist of:

  • Metacarpal-phalangeal joints, connecting the metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy to the fingers
  • Interphalangeal joints, the hinge joints between the phalanges of the fingers
Table: Joints of the hand
Type Components Function Clinical relevance
Interphalangeal Hinge joint
  • Between the phalanges of each digit
  • Proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints
  • The thumb has an interphalangeal (IP) joint.
Metacarpophalangeal Thumb: hinge joint Head of the 1st metacarpal and the proximal end of the proximal phalanx Affected early by rheumatoid arthritis Rheumatoid arthritis Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Rheumatoid Arthritis
2nd–5th digits: ellipsoid joints Heads of the 2nd–5th metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy and the proximal end of the proximal phalanges
Joints of the digits

Joints of the digits, featuring the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints

Image by BioDigital, edited by Lecturio

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3:04
Joints of Digits – Joints of Upper Limb

Intrinsic Muscles of the Hand

The muscles of the hand are divided into 2 groups based on muscle belly location:

  1. Extrinsic: Muscle bellies are in the forearm Forearm The forearm is the region of the upper limb between the elbow and the wrist. The term “forearm” is used in anatomy to distinguish this area from the arm, a term that is commonly used to describe the entire upper limb. The forearm consists of 2 long bones (the radius and the ulna), the interosseous membrane, and multiple arteries, nerves, and muscles. Forearm: Anatomy; they provide strength and grip. (See the following section.)
  2. Intrinsic: Muscle bellies are within the hand and are responsible for fine movement of the fingers.
    • Thenar muscles: 
      • Form the thenar eminence
      • Responsible for multiple motions of the thumb
      • All innervated by the median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve (except for the adductor pollicis, which is innervated by the ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy)
    • Hypothenar muscles: 
      • Form the hypothenar eminence
      • Responsible for multiple motions of the 5th digit (“little finger”)
      • All innervated by the ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy
    • Lumbricals: 
      • Link the flexor and extensor tendons of the fingers
      • Flex the MCP joints and contribute to the extension Extension Examination of the Upper Limbs of the interphalangeal joints
      • Lumbricals I and II (lateral side of the hand) are innervated by the median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve.
      • Lumbricals III and IV (medial side of the hand) are innervated by the ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy.
    • Interossei: 
      • 4 dorsal interossei abduct the 2nd–5th fingers.
      • 3 palmar interossei adduct the 2nd–5th fingers.
      • Are innervated by the ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy
Anterior view of the right hand, featuring the palm, thenar and hypothenar muscles

Anterior view of the right hand, featuring the palm, thenar, and hypothenar muscles making up the thenar and hypothenar eminences, and the palmar aponeurosis

Image by BioDigital, edited by Lecturio.

Thenar muscles

Muscle Origin Insertion Innervation Function
Opponens pollicis Flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy and trapezium Lateral side of the 1st metacarpal bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types Recurrent branch of median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve (C8) Opposes thumb
Abductor pollicis brevis Flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy and tubercles of scaphoid and trapezium Lateral side of proximal phalanx of 1st digit
  • Abducts thumb
  • Supports the opposition
Flexor pollicis brevis Flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy and trapezium
  • Superficial head: median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve
  • Deep head: deep branch of ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy (C8, T1)
 Flexes thumb
Adductor pollicis
  • Oblique head: base of 2nd–3rd metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy and capitate
  • Transverse head: palmar surface of 3rd metacarpal
 Medial side of proximal phalanx of thumb Deep branch of ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy (C8) Adducts thumb
Thenar muscles in hand

Thenar muscles of hand

Image by Lecturio.
  • Thenar muscles 1

    Thenar muscles, featuring the deepest muscles: adductor pollicis and opponens pollicis

    Image by BioDigital, edited by Lecturio.
  • Thenar muscles 3

    Thenar muscles, featuring the intermediate muscle: flexor pollicis brevis

    Image by BioDigital, edited by Lecturio
  • Thenar muscles in the hand

    Thenar muscles, featuring the most superficial muscle: abductor pollicis brevis

    Image by BioDigital, edited by Lecturio

Hypothenar muscles

Muscle Origin Insertion Innervation Function
Palmaris brevis Flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy and palmar aponeurosis Skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions of the hypothenar eminence Ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy Strengthens palmar grip by wrinkling the skin Skin The skin, also referred to as the integumentary system, is the largest organ of the body. The skin is primarily composed of the epidermis (outer layer) and dermis (deep layer). The epidermis is primarily composed of keratinocytes that undergo rapid turnover, while the dermis contains dense layers of connective tissue. Skin: Structure and Functions of the ulnar palm
Abductor digiti minimi Pisiform and flexor carpi ulnaris Flexor carpi ulnaris Forearm: Anatomy Medial side of proximal phalanx of the 5th digit Deep branch of ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy (T1) Abducts the 5th digit
Flexor digiti minimi brevis Hook of hamate and flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy Flexes proximal phalanx of the 5th digit
Opponens digiti minimi Medial border of 5th metacarpal Opposes the 5th digit
Hypothenar muscles hand

Hypothenar muscles

Image by Lecturio.
  • Hypothenar muscles

    Hypothenar muscles, featuring the deepest muscle: opponens digiti minimi

    Image by BioDigital, edited by Lecturio.
  • Hypothenar muscles

    Hypothenar muscles, featuring the intermediate muscles: flexor digiti minimi brevis and abductor digiti minimi

    Image by BioDigital, edited by Lecturio.
  • Hypothenar muscles

    Hypothenar muscles, featuring the most superficial muscle: palmaris brevis

    Image by BioDigital, edited by Lecturio.

Lumbrical muscles

Muscle Origin Insertion Innervation Function
Lumbricals (I–II) Lateral 2 tendons of flexor digitorum profundus Flexor digitorum profundus Forearm: Anatomy Lateral surfaces of extensor expansions of the 2nd–5th digits Median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve (T1) Flex metacarpophalangeal and extend interphalangeal joints of 2nd–5th digits
Lumbricals (III–IV) Medial 2 tendons of flexor digitorum profundus Flexor digitorum profundus Forearm: Anatomy Deep branch of ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy (T1)
Lumbricals muscles

Lumbrical muscles

Image by BioDigital, edited by Lecturio

Interossei muscles

Muscle Origin Insertion Innervation Function
Dorsal interossei (4 muscles) Radial and ulnar side of each pair of consecutive metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy Base of proximal phalanges and extensor expansions (dorsal: 2nd–4th digits; palmar: 2nd, 4th, and 5th digits) Deep branch of ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy (T1) Abduct 2nd–4th digits
Palmar interossei (3 muscles) Sides of the metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy facing midline Adduct 2nd, 4th, and 5th digits
  • Palmar interossei (3 muscles) 2

    Palmar interossei (3 muscles)

    Image by BioDigital, edited by Lecturio
  • Dorsal interossei (4 muscles) 2

    Dorsal interossei (4 muscles)

    Image by BioDigital, edited by Lecturio

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Extrinsic Muscles of the Hand

The extrinsic muscles of the hand have their origin and muscle bellies in the forearm Forearm The forearm is the region of the upper limb between the elbow and the wrist. The term “forearm” is used in anatomy to distinguish this area from the arm, a term that is commonly used to describe the entire upper limb. The forearm consists of 2 long bones (the radius and the ulna), the interosseous membrane, and multiple arteries, nerves, and muscles. Forearm: Anatomy and are divided into flexor (anterior compartment) and extensor (posterior compartment) muscles.

Extensors (enclosed in the extensor retinaculum) Flexors (enclosed in a common synovial sheath)
Superficial Deep Superficial Deep

Extrinsic extensor muscles: superficial layer

Muscle Origin Insertion Innervation Function
Extensor carpi radialis longus Extensor carpi radialis longus Forearm: Anatomy Lateral supracondylar ridge of the humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy Dorsal aspect of base of 2nd metacarpal Radial nerve Radial Nerve A major nerve of the upper extremity. In humans the fibers of the radial nerve originate in the lower cervical and upper thoracic spinal cord (usually C5 to T1), travel via the posterior cord of the brachial plexus, and supply motor innervation to extensor muscles of the arm and cutaneous sensory fibers to extensor regions of the arm and hand. Axilla and Brachial Plexus: Anatomy Abduction Abduction Examination of the Upper Limbs and extension Extension Examination of the Upper Limbs of the wrist (dorsiflexion)
Extensor carpi radialis brevis Extensor carpi radialis brevis Forearm: Anatomy Lateral epicondyle Lateral epicondyle Arm: Anatomy Dorsal aspect of base of 3rd metacarpal
Extensor digitorum Extensor digitorum Forearm: Anatomy Extensor expansion, base of middle and distal phalanges of 2nd–5th digits Posterior interosseous nerve (C7; from deep radial nerve Radial Nerve A major nerve of the upper extremity. In humans the fibers of the radial nerve originate in the lower cervical and upper thoracic spinal cord (usually C5 to T1), travel via the posterior cord of the brachial plexus, and supply motor innervation to extensor muscles of the arm and cutaneous sensory fibers to extensor regions of the arm and hand. Axilla and Brachial Plexus: Anatomy)
  • Extend wrist
  • Extend 2nd–5th digits at metacarpophalangeal and interphalangeal joints (5th digit for EDM)
Extensor digiti minimi Extensor digiti minimi Forearm: Anatomy Extensor expansion, middle and distal phalanges of 5th digit
Extensor carpi ulnaris Extensor carpi ulnaris Forearm: Anatomy Lateral epicondyle Lateral epicondyle Arm: Anatomy of the humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy and posterior surface of ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy Dorsal aspect of base of 5th metacarpal Extends and adducts wrist
Superficial extensor muscles of the hand

Extrinsic extensor muscles of the hand: superficial layer

Image by BioDigital, edited by Lecturio.

Extrinsic extensor muscles: deep layer

Muscle Origin Insertion Innervation Function
Abductor pollicis longus Abductor pollicis longus Forearm: Anatomy Posterior surface of radius Radius The outer shorter of the two bones of the forearm, lying parallel to the ulna and partially revolving around it. Forearm: Anatomy and ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy, interosseous membrane Interosseous Membrane A sheet of fibrous connective tissue rich in collagen often linking two parallel bony structures forming a syndesmosis type joint. It provides longitudinal stability, tensile strength, and weight distribution/transfer and may allow limited movement in syndesmoses. Forearm: Anatomy Base of 1st metacarpal Posterior interosseous nerve (C7 and C8) from deep radial nerve Radial Nerve A major nerve of the upper extremity. In humans the fibers of the radial nerve originate in the lower cervical and upper thoracic spinal cord (usually C5 to T1), travel via the posterior cord of the brachial plexus, and supply motor innervation to extensor muscles of the arm and cutaneous sensory fibers to extensor regions of the arm and hand. Axilla and Brachial Plexus: Anatomy
Extensor pollicis longus Extensor pollicis longus Forearm: Anatomy Posterior surface of ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy, interosseous membrane Interosseous Membrane A sheet of fibrous connective tissue rich in collagen often linking two parallel bony structures forming a syndesmosis type joint. It provides longitudinal stability, tensile strength, and weight distribution/transfer and may allow limited movement in syndesmoses. Forearm: Anatomy Dorsal surface of distal phalanx of thumb
  • Extend wrist
  • Extend distal (longus) and proximal (brevis) phalanx of thumb at interphalangeal joint
  • Extend metacarpophalangeal and carpometacarpal Carpometacarpal The articulations between the carpal bones and the metacarpal bones. Wrist Joint: Anatomy joints
Extensor pollicis brevis Extensor pollicis brevis Forearm: Anatomy Posterior surface of radius Radius The outer shorter of the two bones of the forearm, lying parallel to the ulna and partially revolving around it. Forearm: Anatomy, interosseous membrane Interosseous Membrane A sheet of fibrous connective tissue rich in collagen often linking two parallel bony structures forming a syndesmosis type joint. It provides longitudinal stability, tensile strength, and weight distribution/transfer and may allow limited movement in syndesmoses. Forearm: Anatomy Dorsal surface of proximal phalanx of thumb
Extensor indicis Extensor indicis Forearm: Anatomy Posterior surface of the ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy Extensor expansion of 2nd finger
Deep extensor muscles of the hand

Extrinsic extensor muscles of the hand: deep layer

Image by BioDigital, edited by Lecturio.

Extrinsic flexor muscles: superficial layer

Muscle Origin Insertion Innervation Function
Flexor carpi radialis Flexor carpi radialis Forearm: Anatomy Medial epicondyle Medial epicondyle Arm: Anatomy of humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy Base of 2nd–3rd metacarpals Metacarpals The five cylindrical bones of the metacarpus, articulating with the carpal bones proximally and the phalanges of fingers distally. Wrist Joint: Anatomy Median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve (C7) Flexes and abducts wrist
Palmaris longus Palmaris longus Forearm: Anatomy Flexor retinaculum Flexor Retinaculum Ankle Joint: Anatomy and palmar aponeurosis Flexes wrist weakly and tenses palmar aponeurosis
Flexor carpi ulnaris Flexor carpi ulnaris Forearm: Anatomy Medial epicondyle Medial epicondyle Arm: Anatomy of the humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy, olecranon Olecranon A prominent projection of the ulna that articulates with the humerus and forms the outer protuberance of the elbow joint. Arm: Anatomy, and posterior ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy Pisiform, hook of hamate, base of 5th metacarpal Ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy (C8) Flexes and adducts wrist
Flexor digitorum superficialis Flexor digitorum superficialis Forearm: Anatomy Medial epicondyle Medial epicondyle Arm: Anatomy of the humerus Humerus Bone in humans and primates extending from the shoulder joint to the elbow joint. Arm: Anatomy, proximal shaft of the radius Radius The outer shorter of the two bones of the forearm, lying parallel to the ulna and partially revolving around it. Forearm: Anatomy Middle phalanges of the medial 4 fingers Median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve (C7)
  • Flexes the proximal interphalangeal joints
  • Assists in flexing the metacarpophalangeal and wrist joints
Extrinsic flexor muscles of the hand - superficial layer

Extrinsic flexor muscles of the hand: superficial layer

Image by BioDigital, edited by Lecturio.

Extrinsic flexor muscles: deep layer

Muscle Origin Insertion Innervation Function
Flexor digitorum profundus Flexor digitorum profundus Forearm: Anatomy Proximal end of the ulna Ulna The inner and longer bone of the forearm. Forearm: Anatomy (medial and anterior surfaces) and interosseous membrane Interosseous Membrane A sheet of fibrous connective tissue rich in collagen often linking two parallel bony structures forming a syndesmosis type joint. It provides longitudinal stability, tensile strength, and weight distribution/transfer and may allow limited movement in syndesmoses. Forearm: Anatomy Distal phalanges of the 2nd–5th digits
  • Digits 2 and 3: median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve (C7, C8, T1)
  • Digits 4 and 5: ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy (T1)
Flexor pollicis longus Flexor pollicis longus Forearm: Anatomy Shaft of radius Radius The outer shorter of the two bones of the forearm, lying parallel to the ulna and partially revolving around it. Forearm: Anatomy (anterior surface) and interosseous membrane Interosseous Membrane A sheet of fibrous connective tissue rich in collagen often linking two parallel bony structures forming a syndesmosis type joint. It provides longitudinal stability, tensile strength, and weight distribution/transfer and may allow limited movement in syndesmoses. Forearm: Anatomy Distal phalanx of thumb Anterior interosseous nerve Anterior Interosseous Nerve Supracondylar Fracture (branch of median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion) (C8)
Extrinsic flexor muscles of the hand - deep layer

Extrinsic flexor muscles of the hand: deep layer

Image by BioDigital, edited by Lecturio.

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Movements of the Fingers

Extensor expansion

Also known as the extensor hood, dorsal expansion, dorsal hood, or dorsal aponeurosis of the hand and/or fingers. The extensor expansion comprises the tendons of the extensor muscles of the fingers and how these insert into the phalanges:

  • At the distal end of the metacarpal, these tendons expand and merge to form an aponeurosis (“hood”), which covers:
    • Head of the metacarpal (dorsal and lateral sides)
    • Proximal phalanx (dorsal and lateral sides)
  • At the proximal phalanx, the tendons divide into bands:
    • Lateral bands (2 per finger): pass on either side of the middle phalanx and insert into the distal phalanx, receiving tendons from the lumbricals, extensor indicis Extensor indicis Forearm: Anatomy, and dorsal and palmar interossei muscles
    • Central band (1 per finger): passes down the center of the proximal phalanx to insert into the base of the middle phalanx
    • Retinacular bands (2 per finger): pass obliquely on the lateral sides of the middle phalanx to connect the aponeuroses of palmar and dorsal sides of the finger
Extensor expansion of the digits

Schematic of a finger, featuring the extensor expansion or dorsal aponeurosis and insertion of the tendons of the flexor digitorum muscle

Image by Lecturio.

Flexor pulley system

Comprises the tendons of the flexor muscles of the fingers and how these insert into the phalanges, supported by a system of ligaments:

  • Dorsal_view_of_the_hand(with _muscles)

    Dorsal view of the hand with the intrinsic and extrinsic muscles. The dorsal hood of the ring finger has been removed.

    Image by BioDigital, edited by Lecturio.
  • Flexor pulley system

    Palmar view of the hand, featuring the insertion of the tendons of the intrinsic and extrinsic muscles: the flexor pulley system. The cruciate and annular Annular Dermatologic Examination ligaments of the index finger have been removed.

    Image by BioDigital, edited by Lecturio.

Vessels of the Hand

Arterial supply

The arterial blood supply of the hand is provided by:

  • Radial artery Radial Artery The direct continuation of the brachial trunk, originating at the bifurcation of the brachial artery opposite the neck of the radius. Its branches may be divided into three groups corresponding to the three regions in which the vessel is situated, the forearm, wrist, and hand. Forearm: Anatomy: palpated immediately lateral to the flexor carpi radialis Flexor carpi radialis Forearm: Anatomy tendon and just proximal to the wrist crease
  • Ulnar artery Ulnar Artery The larger of the two terminal branches of the brachial artery, beginning about one centimeter distal to the bend of the elbow. Like the radial artery, its branches may be divided into three groups corresponding to their locations in the forearm, wrist, and hand. Forearm: Anatomy: palpated anterior medially on the wrist and passes into the hand through Guyon’s canal Guyon’s canal Wrist Joint: Anatomy
  • Together, the radial and ulnar artery Ulnar Artery The larger of the two terminal branches of the brachial artery, beginning about one centimeter distal to the bend of the elbow. Like the radial artery, its branches may be divided into three groups corresponding to their locations in the forearm, wrist, and hand. Forearm: Anatomy form 2 arterial arches:
    • Superficial palmar arch: ulnar artery Ulnar Artery The larger of the two terminal branches of the brachial artery, beginning about one centimeter distal to the bend of the elbow. Like the radial artery, its branches may be divided into three groups corresponding to their locations in the forearm, wrist, and hand. Forearm: Anatomy + superficial palmar branch of the radial
    • Deep palmar arch: radial artery Radial Artery The direct continuation of the brachial trunk, originating at the bifurcation of the brachial artery opposite the neck of the radius. Its branches may be divided into three groups corresponding to the three regions in which the vessel is situated, the forearm, wrist, and hand. Forearm: Anatomy + deep palmar branch of the ulnar
  • Blood supply of the dorsal aspect of the hand

    Blood supply of the dorsal aspect of the hand featuring the basal metacarpal arch

    Image by BioDigital, edited by Lecturio.
  • Blood supply to the palmar aspect of the hand

    Blood supply to the palmar aspect of the hand featuring the superficial and deep palmar arches

    Image by BioDigital, edited by Lecturio.

Venous drainage

The venous drainage of the hand is the origin of the veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology of the upper extremity and begins in the dorsal and palmar venous network of the hand.

  • Cephalic vein originates from the dorsal venous network in the area of the anatomical snuffbox.
  • Basilic vein Basilic vein Arm: Anatomy originates from the ulnar side of the dorsal venous network of the hand.
  • Median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion antebrachial vein originates from the palmar venous network of the hand.
Venous drainage of the hand

Venous drainage of the hand featuring the dorsal venous arch Dorsal venous arch Foot: Anatomy and digital veins Veins Veins are tubular collections of cells, which transport deoxygenated blood and waste from the capillary beds back to the heart. Veins are classified into 3 types: small veins/venules, medium veins, and large veins. Each type contains 3 primary layers: tunica intima, tunica media, and tunica adventitia. Veins: Histology

Image by BioDigital, edited by Lecturio.

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Innervation of the Hand

The innervation of the hand is primarily via the median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion and ulnar nerves, with the radial nerve Radial Nerve A major nerve of the upper extremity. In humans the fibers of the radial nerve originate in the lower cervical and upper thoracic spinal cord (usually C5 to T1), travel via the posterior cord of the brachial plexus, and supply motor innervation to extensor muscles of the arm and cutaneous sensory fibers to extensor regions of the arm and hand. Axilla and Brachial Plexus: Anatomy only contributing a small area of sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation on the radial dorsal aspect of the hand.

Motor Motor Neurons which send impulses peripherally to activate muscles or secretory cells. Nervous System: Histology innervation

Median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve
  • Thenar muscles (except adductor pollicis)
  • Lateral 2 lumbricals of the hand
Ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy Remaining muscles except those supplied by the median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve

Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation

Median Median After arranging the data from loWest to highest, the median is the middle value, separating the lower half from the upper half of the data set. Measures of Central Tendency and Dispersion nerve
  • Radial â…” of the palm
  • Palmar aspect of the thumb, 2nd–3rd fingers, and radial side of the 4th finger
  • Dorsal aspect of the distal phalanges of the thumb, 2nd–3rd fingers, and radial side of the 4th finger
  • Autonomous sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology zone: the tip of the index finger
Ulnar nerve Ulnar Nerve A major nerve of the upper extremity. In humans, the fibers of the ulnar nerve originate in the lower cervical and upper thoracic spinal cord (usually C7 to T1), travel via the medial cord of the brachial plexus, and supply sensory and motor innervation to parts of the hand and forearm. Axilla and Brachial Plexus: Anatomy
  • Ulnar â…“ of the palm
  • Palmar and dorsal aspects of the 5th finger and ulnar side of the 4th finger
  • Autonomous sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology zone: the tip of the 5th finger
Radial nerve Radial Nerve A major nerve of the upper extremity. In humans the fibers of the radial nerve originate in the lower cervical and upper thoracic spinal cord (usually C5 to T1), travel via the posterior cord of the brachial plexus, and supply motor innervation to extensor muscles of the arm and cutaneous sensory fibers to extensor regions of the arm and hand. Axilla and Brachial Plexus: Anatomy
  • Radial â…” of the dorsal aspect of the hand
  • Dorsal aspect of the thumb, 2nd–3rd fingers, and radial side of the 4th finger (except the distal phalanges)
  • Autonomous sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology zone: space between the thumb and index finger on the dorsal aspect of the hand
The innervation of the hand

Sensory Sensory Neurons which conduct nerve impulses to the central nervous system. Nervous System: Histology innervation of the hand

Image by Lecturio.

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Clinical Relevance

The following are common problems associated with the hand:

  • Boxer’s fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures: fracture Fracture A fracture is a disruption of the cortex of any bone and periosteum and is commonly due to mechanical stress after an injury or accident. Open fractures due to trauma can be a medical emergency. Fractures are frequently associated with automobile accidents, workplace injuries, and trauma. Overview of Bone Fractures of the distal portion of the 5th metacarpal bone Bone Bone is a compact type of hardened connective tissue composed of bone cells, membranes, an extracellular mineralized matrix, and central bone marrow. The 2 primary types of bone are compact and spongy. Bones: Structure and Types. Usually due to hitting an object with a closed fist. Symptoms include pain Pain An unpleasant sensation induced by noxious stimuli which are detected by nerve endings of nociceptive neurons. Pain: Types and Pathways and a depressed knuckle. Diagnosis is suspected based on the clinical exam and confirmed by X-rays X-rays X-rays are high-energy particles of electromagnetic radiation used in the medical field for the generation of anatomical images. X-rays are projected through the body of a patient and onto a film, and this technique is called conventional or projectional radiography. X-rays.
  • Rheumatoid arthritis Rheumatoid arthritis Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Rheumatoid Arthritis: a majority of rheumatoid diseases affect Affect The feeling-tone accompaniment of an idea or mental representation. It is the most direct psychic derivative of instinct and the psychic representative of the various bodily changes by means of which instincts manifest themselves. Psychiatric Assessment the hand and finger joints. The synovial proliferation results in skeleton erosion Erosion Partial-thickness loss of the epidermis Generalized and Localized Rashes, destruction of the capsular ligamentous structures, and changes to tendon structure and function. Physical exam of the hand classically presents with ulnar deviation and subluxation Subluxation Radial Head Subluxation (Nursemaid’s Elbow) of the metacarpal phalangeal (MCP) joints, swan neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess deformities of the fingers, and Z deformity Deformity Examination of the Upper Limbs of the thumb.
  • Swan neck Neck The part of a human or animal body connecting the head to the rest of the body. Peritonsillar Abscess deformity Deformity Examination of the Upper Limbs: characterized by flexion Flexion Examination of the Upper Limbs of the DIP joint and hyperextension of the PIP joint. Associated with rheumatoid arthritis Rheumatoid arthritis Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Rheumatoid Arthritis, trauma, and laceration Laceration Torn, ragged, mangled wounds. Blunt Chest Trauma.
  • Boutonniere deformity Boutonniere Deformity Rheumatoid Arthritis: characterized by DIP joint extension Extension Examination of the Upper Limbs and PIP joint flexion Flexion Examination of the Upper Limbs. Secondary to rupture of the central slip of the extensor mechanism over the PIP joint. Associated with trauma (PIP joint dislocation) and rheumatoid arthritis Rheumatoid arthritis Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Rheumatoid Arthritis.
  • Osteoarthritis Osteoarthritis Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Osteoarthritis: a degenerative disorder of the articular cartilage Cartilage Cartilage is a type of connective tissue derived from embryonic mesenchyme that is responsible for structural support, resilience, and the smoothness of physical actions. Perichondrium (connective tissue membrane surrounding cartilage) compensates for the absence of vasculature in cartilage by providing nutrition and support. Cartilage: Histology, subchondral bones, and other joint structures. Osteoarthritis Osteoarthritis Osteoarthritis (OA) is the most common form of arthritis, and is due to cartilage destruction and changes of the subchondral bone. The risk of developing this disorder increases with age, obesity, and repetitive joint use or trauma. Patients develop gradual joint pain, stiffness lasting < 30 minutes, and decreased range of motion. Osteoarthritis is the most common type of joint disease and the leading cause of disability Disability Determination of the degree of a physical, mental, or emotional handicap. The diagnosis is applied to legal qualification for benefits and income under disability insurance and to eligibility for social security and workman’s compensation benefits. ABCDE Assessment in older adults. The main risk factors are family history Family History Adult Health Maintenance, female gender Gender Gender Dysphoria, past trauma to the involved joint, aging, and obesity Obesity Obesity is a condition associated with excess body weight, specifically with the deposition of excessive adipose tissue. Obesity is considered a global epidemic. Major influences come from the western diet and sedentary lifestyles, but the exact mechanisms likely include a mixture of genetic and environmental factors. Obesity.
    • Heberden’s nodes (DIP): usually secondary to primary osteoarthritis Primary Osteoarthritis Osteoarthritis of the DIP joints. Associated with mucous cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change of the DIP joint and nail deformities. May contribute to joint contracture and deformity Deformity Examination of the Upper Limbs.
    • Bouchard’s nodes (PIP): hard, bony outgrowths or gelatinous cysts Cysts Any fluid-filled closed cavity or sac that is lined by an epithelium. Cysts can be of normal, abnormal, non-neoplastic, or neoplastic tissues. Fibrocystic Change on the PIP joints. Less commonly, Bouchard’s nodes may be seen in rheumatoid arthritis Rheumatoid arthritis Rheumatoid arthritis (RA) is a symmetric, inflammatory polyarthritis and chronic, progressive, autoimmune disorder. Presentation occurs most commonly in middle-aged women with joint swelling, pain, and morning stiffness (often in the hands). Rheumatoid Arthritis. May contribute to joint contracture and deformity Deformity Examination of the Upper Limbs.

References

  1. Drake, R.L., Vogl, A.W., & Mitchell, A.W.M. (2014). Gray’s Anatomy for Students (3rd ed.). Philadelphia, PA:  Churchill Livingstone.
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