Gross Anatomy II: Week 3 Lecture Notes
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Questions and Answers

Which nerve supplies the flexor digitorum profundus?

  • Radial nerve
  • Musculocutaneous nerve
  • Median nerve
  • Ulnar nerve (correct)

    • What is the main action of the flexor pollicis longus?

  • Extends the metacarpophalangeal and interphalangeal joints of the thumb
  • Flexes the metacarpophalangeal and interphalangeal joints of the thumb (correct)
  • Rotates the forearm
  • Abducts the thumb

    • What is the origin of the ulnar artery?

  • Radial artery
  • Brachial artery (correct)
  • Axillary artery
  • Median artery

    • Which muscle has a bony attachment to the distal anteriomedial ulna?

    <p>Pronator quadratus</p> Signup and view all the answers

    What is the nerve supply to the flexor digitorum profundus?

    <p>Median nerve and ulnar nerve</p> Signup and view all the answers

    Which artery supplies the flexor pollicis longus?

    <p>Anterior interosseous artery</p> Signup and view all the answers

    What is the action of the pronator quadratus?

    <p>Pronates the forearm</p> Signup and view all the answers

    What is the relationship between the ulnar artery and the ulnar nerve in the lower forearm?

    <p>The ulnar nerve is medial to the ulnar artery</p> Signup and view all the answers

    Which nerve supplies the muscles of the anterior compartment of the forearm?

    <p>All of the above</p> Signup and view all the answers

    What is the location of the extensor retinaculum?

    <p>Wrist region</p> Signup and view all the answers

    What is the content of the anatomical snuffbox?

    <p>All of the above</p> Signup and view all the answers

    Which vein is located in the superficial compartment of the forearm?

    <p>All of the above</p> Signup and view all the answers

    What is the action of the muscles of the anterior compartment of the forearm?

    <p>All of the above</p> Signup and view all the answers

    What is the termination of the superficial veins of the forearm?

    <p>Axillary vein</p> Signup and view all the answers

    What is the boundary of the carpal tunnel?

    <p>All of the above</p> Signup and view all the answers

    What is the course of the radial nerve in the anterior compartment of the forearm?

    <p>Passes between the brachioradialis and the extensor carpi radialis longus</p> Signup and view all the answers

    Which nerve is responsible for the innervation of the flexor carpi radialis muscle?

    <p>Median nerve</p> Signup and view all the answers

    What is the function of the pronator teres muscle?

    <p>Pronation of the forearm</p> Signup and view all the answers

    Which of the following muscles is absent in about 15% of the population?

    <p>Palmaris longus</p> Signup and view all the answers

    Which nerve passes between the two heads of the flexor carpi ulnaris muscle as it enters the anterior compartment of the forearm?

    <p>Ulnar nerve</p> Signup and view all the answers

    What is the function of the flexor carpi ulnaris muscle?

    <p>Flexion of the wrist and adduction of the hand</p> Signup and view all the answers

    Which of the following veins is frequently used for venipuncture?

    <p>Median cubital vein</p> Signup and view all the answers

    What is the function of the interosseous membrane?

    <p>Division of the forearm into anterior and posterior compartments</p> Signup and view all the answers

    Which nerve is responsible for the innervation of the flexor digitorum superficialis muscle?

    <p>Median nerve</p> Signup and view all the answers

    What is the origin of the ulnar head of the pronator teres muscle?

    <p>Medial aspect of the coronoid process of the ulna</p> Signup and view all the answers

    Which of the following muscles is located in the superficial layer of the anterior compartment of the forearm?

    <p>Pronator teres</p> Signup and view all the answers

    What is the location of the radial artery in the upper forearm?

    <p>Superficial to pronator teres</p> Signup and view all the answers

    What is the origin of the superficial palmar branch of the radial artery?

    <p>Just above the wrist</p> Signup and view all the answers

    Which of the following nerves accompanies the radial artery in the middle part of the forearm?

    <p>Superficial branch of the radial nerve</p> Signup and view all the answers

    What is the function of the radial recurrent artery?

    <p>To participate in the arterial anastomosis around the elbow joint</p> Signup and view all the answers

    What is the location of the radial vein in the forearm?

    <p>Accompanying the radial artery</p> Signup and view all the answers

    What is the connection between the radial and ulnar veins in the cubital fossa?

    <p>They join to form two brachial veins</p> Signup and view all the answers

    What is the location of the median nerve in the forearm?

    <p>Between flexor digitorum superficialis and flexor digitorum profundus</p> Signup and view all the answers

    What is the origin of the anterior interosseous nerve?

    <p>From the median nerve as it emerges from pronator teres</p> Signup and view all the answers

    What is the function of the palmar branch of the median nerve?

    <p>To supply the skin of the central, depressed area of the palm of the hand</p> Signup and view all the answers

    What is the path of the median nerve in the hand?

    <p>It emerges from underneath flexor digitorum superficialis and enters the hand through the carpal tunnel</p> Signup and view all the answers

    What is the primary action of the Extensor Digiti Minimi muscle?

    <p>Extensions of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints of the 5th digit</p> Signup and view all the answers

    Which nerve provides innervation to the Extensor Pollicis Brevis muscle?

    <p>Radial nerve</p> Signup and view all the answers

    What is the primary function of the Anconeus muscle?

    <p>Assists in extension of the elbow joint</p> Signup and view all the answers

    Which compartment of the forearm contains the Extensor Pollicis Longus muscle?

    <p>Posterior compartment</p> Signup and view all the answers

    What is the primary blood supply to the posterior compartment of the forearm?

    <p>Posterior interosseous artery</p> Signup and view all the answers

    Which muscle is associated with the 3rd compartment of the extensor retinaculum?

    <p>Extensor Pollicis Longus</p> Signup and view all the answers

    What is the boundary of the anatomical snuffbox on the medial side?

    <p>Tendon of Extensor Pollicis Longus</p> Signup and view all the answers

    Which nerve supplies the Supinator muscle?

    <p>Radial nerve</p> Signup and view all the answers

    What is the primary action of the Extensor Carpi Radialis Brevis muscle?

    <p>Extends the wrist and radially deviates the hand</p> Signup and view all the answers

    What is the origin of the Anconeus muscle?

    <p>Lateral epicondyle of the humerus</p> Signup and view all the answers

    The flexor digitorum profundus flexes the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints.

    <p>True</p> Signup and view all the answers

    The ulnar artery supplies blood to the flexor pollicis longus muscle.

    <p>True</p> Signup and view all the answers

    The pronator quadratus muscle pronates the hand.

    <p>False</p> Signup and view all the answers

    The median nerve supplies the flexor digitorum profundus muscle.

    <p>False</p> Signup and view all the answers

    The ulnar artery arises from the brachial artery in the cubital fossa.

    <p>True</p> Signup and view all the answers

    The flexor pollicis longus muscle flexes the interphalangeal joint of the thumb.

    <p>True</p> Signup and view all the answers

    The tendon of flexor carpi ulnaris is lateral to the ulnar artery in the lower forearm.

    <p>False</p> Signup and view all the answers

    The pronator quadratus muscle has a bony attachment to the interosseous membrane.

    <p>False</p> Signup and view all the answers

    The ulnar artery is responsible for the blood supply of the anterior compartment of the forearm.

    <p>True</p> Signup and view all the answers

    The median nerve is responsible for the innervation of the muscles of the posterior compartment of the forearm.

    <p>False</p> Signup and view all the answers

    The radial nerve is responsible for the innervation of the extensor carpi radialis brevis muscle.

    <p>True</p> Signup and view all the answers

    The pronator teres muscle has a bony attachment to the medial epicondyle of the humerus.

    <p>True</p> Signup and view all the answers

    The flexor digitorum profundus muscle is innervated by the radial nerve.

    <p>False</p> Signup and view all the answers

    The anatomical snuffbox is located on the medial aspect of the wrist.

    <p>False</p> Signup and view all the answers

    The superficial veins of the forearm terminate in the cephalic and basilic veins.

    <p>True</p> Signup and view all the answers

    The extensor retinaculum is located in the posterior compartment of the forearm.

    <p>False</p> Signup and view all the answers

    The radial nerve is responsible for the innervation of the pronator teres muscle.

    <p>False</p> Signup and view all the answers

    The interosseous membrane attaches to the interosseous borders of the humerus and ulna.

    <p>False</p> Signup and view all the answers

    The median cubital vein is frequently used for venipuncture.

    <p>True</p> Signup and view all the answers

    The posterior compartment of the forearm contains flexor and pronator muscles.

    <p>False</p> Signup and view all the answers

    The lateral cutaneous nerve of the forearm is a branch of the radial nerve.

    <p>True</p> Signup and view all the answers

    The ulnar artery lies medial to the ulnar nerve along most of its course.

    <p>False</p> Signup and view all the answers

    The flexor carpi radialis muscle is absent in about 15% of the population.

    <p>False</p> Signup and view all the answers

    The posterior interosseous artery anastomoses with the terminal part of the anterior interosseous artery.

    <p>False</p> Signup and view all the answers

    The common interosseous artery is a long branch that originates from the distal part of the ulnar artery.

    <p>False</p> Signup and view all the answers

    The ulnar nerve passes between the two heads of the flexor carpi radialis muscle as it enters the anterior compartment of the forearm.

    <p>False</p> Signup and view all the answers

    The radial nerve is responsible for the innervation of the extensor muscles of the forearm.

    <p>False</p> Signup and view all the answers

    The palmar and dorsal carpal branches of the ulnar artery anastomose with the corresponding branches of the radial artery.

    <p>True</p> Signup and view all the answers

    The superficial veins of the forearm drain into the cubital fossa.

    <p>True</p> Signup and view all the answers

    The ulnar artery enters the hand posterior to the flexor retinaculum.

    <p>False</p> Signup and view all the answers

    The anterior interosseous artery runs posteriorly on the anterior aspect of the interosseous membrane.

    <p>False</p> Signup and view all the answers

    The interosseous membrane divides the forearm into anterior and posterior compartments.

    <p>True</p> Signup and view all the answers

    The posterior interosseous artery passes anteriorly between the ulna and radius.

    <p>False</p> Signup and view all the answers

    The ulnar artery forms the superficial palmar arch in the hand.

    <p>True</p> Signup and view all the answers

    The flexor carpi ulnaris muscle is supplied by the radial nerve.

    <p>False</p> Signup and view all the answers

    The ulnar nerve passes between the humeral and ulnar heads of the flexor digitorum profundus.

    <p>False</p> Signup and view all the answers

    The flexor retinaculum is a strong fibrous band on the posterior aspect of the wrist.

    <p>False</p> Signup and view all the answers

    The median nerve is compressed in the carpal tunnel, causing carpal tunnel syndrome.

    <p>True</p> Signup and view all the answers

    The extensor carpi radialis brevis muscle is innervated by the radial nerve.

    <p>True</p> Signup and view all the answers

    The ulnar artery is lateral to the ulnar nerve in the upper forearm.

    <p>True</p> Signup and view all the answers

    The extensor digitorum muscle extends the proximal interphalangeal and distal interphalangeal joints of the 2nd-5th digits.

    <p>True</p> Signup and view all the answers

    The posterior compartment of the forearm contains the extensor retinaculum.

    <p>True</p> Signup and view all the answers

    The flexor pollicis longus muscle has its own synovial sheath in the carpal tunnel.

    <p>True</p> Signup and view all the answers

    The extensor carpi ulnaris muscle is innervated by the posterior interosseous nerve.

    <p>True</p> Signup and view all the answers

    Study Notes

    Forearm Anatomy

    Cutaneous Innervation of the Forearm

    • Lateral cutaneous nerve of forearm (lateral antebrachial cutaneous nerve) is a branch of the musculocutaneous nerve.
    • Medial cutaneous nerve of forearm (medial antebrachial cutaneous nerve) is a branch of the medial cord of the brachial plexus.
    • Posterior cutaneous nerve of forearm (posterior antebrachial cutaneous nerve) is a branch of the radial nerve.

    Superficial Veins of the Forearm

    • Cephalic vein (lateral) and basilic vein (medial) are the two main superficial veins.
    • Median cubital vein is a communicating vein that connects the cephalic and basilic veins.
    • Median antebrachial vein is a superficial vein that drains into the median cubital vein.

    Compartments of the Forearm

    • The forearm is divided into anterior and posterior compartments by the interosseous membrane.
    • The anterior compartment contains flexor and pronator muscles, while the posterior compartment contains extensor and supinator muscles.

    Anterior Compartment of the Forearm

    • Muscles of the anterior compartment:
      • Superficial layer: Pronator teres, Palmaris longus, Flexor carpi radialis, and Flexor carpi ulnaris.
      • Intermediate layer: Flexor digitorum superficialis, Flexor pollicis longus, and Pronator quadratus.
    • Innervation and arterial supply of each muscle:
      • Pronator teres: Median nerve (C6, C7), Ulnar artery.
      • Palmaris longus: Median nerve (C7, C8), Ulnar artery.
      • Flexor carpi radialis: Median nerve (C6, C7), Ulnar artery.
      • Flexor carpi ulnaris: Ulnar nerve, Ulnar artery.
      • Flexor digitorum superficialis: Median nerve (C8, T1) for digits 2 & 3, Ulnar nerve for digits 4 & 5, Ulnar artery and Anterior interosseous artery.
      • Flexor pollicis longus: Median nerve (C8, T1), Anterior Interosseous artery.
      • Pronator quadratus: Median nerve (C6, C7), Anterior Interosseous artery.

    Arteries and Veins of the Anterior Compartment

    • Ulnar artery:
      • Begins in the cubital fossa.
      • Passes deep to the ulnar head of the pronator teres.
      • In the upper forearm, it is deeply located and passes deep to the superficial and intermediate muscles.
      • In the lower forearm, it is more superficial.
    • Radial artery:
      • Begins in the cubital fossa.
      • In the upper forearm, it is covered by the brachioradialis and passes superficial to the pronator teres.
      • In the lower forearm, it is superficial and lies between the tendon of brachioradialis and the tendon of flexor carpi radialis.
    • Deep veins of the forearm:
      • Radial and ulnar arteries are accompanied by two veins each (radial and ulnar veins or venae comitantes).
      • There are numerous connections between the two radial veins and between the two ulnar veins.

    Nerves of the Anterior Compartment

    • Median nerve:

      • Exits the cubital fossa by passing between the humeral and ulnar heads of the pronator teres.
      • Descends in the forearm between the flexor digitorum superficialis and flexor digitorum profundus.
      • Enters the hand by passing through the carpal tunnel.
      • Branches:
        • Muscular branches: supply pronator teres, flexor carpi radialis, palmaris longus, and flexor digitorum superficialis.
        • Articular branch: to the elbow joint.
        • Palmar branch: supplies the skin of the central, depressed area of the palm of the hand.
        • Anterior interosseous nerve: supplies the anterior surface of the carpus.### Posterior Compartment of Forearm

    • Extensor Digitorum Communis

      • Arterial supply: Radial artery
      • Action: Extends the wrist, abducts the hand

    • Extensor Digiti Minimi

      • Bony attachments: Common extensor tendon on humerus, extensor digitorum tendon of the 5th digit and extensor expansion
      • Innervation: Radial nerve (C7, C8)
      • Arterial supply: Interosseous artery
      • Action: Extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the 5th digit

    • Anconeus

      • Considered by some authors as a muscle of the posterior compartment of the arm
      • Origin: Lateral epicondyle of humerus
      • Insertion: Olecranon and proximal part of posterior surface of shaft of ulna
      • Nerve supply: Radial nerve
      • Action: Assists triceps brachii with extension of forearm at elbow joint, may abduct ulna during pronation of forearm

    Deep Layer

    • Extensor Indicis
      • Bony attachments: Interosseous membrane and distal ulna, extensor digitorum tendon of the 2nd digit and extensor expansion
      • Innervation: Radial nerve (C7, C8)
      • Arterial supply: Interosseous artery
      • Action: Extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the index finger
    • Extensor Pollicis Brevis
      • Bony attachments: Interosseous membrane and distal radius, proximal phalanx of thumb
      • Innervation: Radial nerve
      • Arterial supply: Interosseous artery
      • Action: Extends the metacarpophalangeal joint of the thumb
    • Extensor Pollicis Longus
      • Bony attachments: Interosseous membrane and mid shaft of the ulna, distal phalanx of thumb
      • Innervation: Radial nerve
      • Arterial supply: Interosseous artery
      • Action: Extends the thumb at the interphalangeal joint
    • Supinator
      • Bony attachments: Distal lateral humerus, proximal ulna, radial ligament, proximal lateral radius
      • Innervation: Radial nerve (C7, C8)
      • Arterial supply: Recurrent interosseous artery
      • Action: Supinates the forearm

    Compartments (Tunnels) Under the Extensor Retinaculum

    • 1st compartment: Tendons of abductor pollicis longus and extensor pollicis brevis
    • 2nd compartment: Tendons of extensor carpi radialis longus and extensor carpi radialis brevis
    • 3rd compartment: Tendon of extensor pollicis longus
    • 4th compartment: Tendons of extensor digitorum and extensor indicis
    • 5th compartment: Tendon of extensor digiti minimi
    • 6th compartment: Tendon of extensor carpi ulnaris

    Anatomical Snuffbox

    • Triangular depression on the lateral side of the wrist
    • Bounded laterally by tendons of abductor pollicis longus and extensor pollicis brevis
    • Bounded medially by tendon of extensor pollicis longus
    • Contains styloid process of radius, scaphoid, trapezium, and base of 1st metacarpal
    • Radial artery crosses anatomical snuff box and passes deep to tendons that form its boundaries
    • Superficial fascia over anatomical snuff box contains branches of superficial radial nerve and origin of cephalic vein from dorsal venous arch of hand

    Radial Nerve

    • Divides into superficial and deep terminal branches anterior to lateral epicondyle of humerus
    • Before dividing into its terminal branches, radial nerve supplies three heads of triceps brachii, anconeus, brachioradialis, and extensor carpi radialis longus
    • Also gives off cutaneous branches to arm and forearm
    • Superficial branch of radial nerve:
      • Descends in forearm deep to brachioradialis muscle and lateral to radial artery
      • In distal forearm, it separates from artery and passes posteriorly, under tendon of brachioradialis, to reach posterior surface of wrist
      • Divides into branches that supply skin of lateral part of dorsum of hand and dorsal aspects of lateral 2½ (or 3½) digits
    • Deep branch of radial nerve:
      • Pierces supinator and winds around lateral aspect of radius within supinator to reach posterior compartment of forearm
      • After it emerges from supinator, it is sometimes referred to as posterior interosseous nerve
      • Supplies extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, supinator, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, and extensor indicis
      • Also gives off articular branches to distal radioulnar and wrist joints

    Blood Supply of the Posterior Compartment

    • Posterior interosseous artery:
      • Originates in anterior compartment of forearm from common interosseous artery
      • Passes posteriorly, between ulna and radius, and above superior border of interosseous membrane, to reach posterior compartment
      • Accompanies posterior interosseous nerve in posterior compartment
      • Gives off interosseous recurrent artery - participates in arterial anastomosis around elbow joint
      • Terminal part of anterior interosseous artery pierces interosseous membrane and anastomoses with posterior interosseous artery

    Cutaneous Innervation of the Forearm

    • The lateral cutaneous nerve of the forearm (lateral antebrachial cutaneous nerve) is a branch of the musculocutaneous nerve.
    • The medial cutaneous nerve of the forearm (medial antebrachial cutaneous nerve) is a branch of the medial cord of the brachial plexus.
    • The posterior cutaneous nerve of the forearm (posterior antebrachial cutaneous nerve) is a branch of the radial nerve.

    Superficial Veins of the Forearm

    • The cephalic vein is located laterally.
    • The basilic vein is located medially.
    • The median cubital vein is frequently used for venipuncture and lies superficial to the cubital fossa in the superficial fascia.
    • The median cubital vein runs superiorly and medially from the cephalic vein to the basilic vein.
    • The median antebrachial vein ascends along the anterior midline of the forearm and drains into the median cubital vein.

    Compartments of the Forearm

    • The forearm is enclosed in a sheath of deep fascia (antebrachial fascia).
    • The interosseous membrane is a thin, strong fibrous membrane that attaches to the interosseous borders of the radius and ulna.
    • The interosseous membrane, radius, and ulna divide the forearm into anterior and posterior compartments, which are surrounded by antebrachial fascia.
    • Each compartment has its own muscles, nerves, and blood vessels.
    • The anterior compartment contains flexor and pronator muscles.
    • The posterior compartment contains extensor and supinator muscles.

    Muscles of the Anterior Compartment

    • Pronator Teres
      • Bony attachments: medial epicondyle and adjacent medial supracondylar ridge of the humerus, and medial aspect of the coronoid process of the ulna.
      • Innervation: Median nerve (C6, C7).
      • Arterial supply: Ulnar artery.
      • Action: Pronates the forearm.
      • Important relationships: The median nerve passes between the two heads of the pronator teres as it leaves the cubital fossa (possible site of compression).
    • Palmaris Longus
      • Bony attachments: common flexor tendon on the humerus, palmar aponeurosis, and flexor retinaculum.
      • Innervation: Median nerve (C7, C8).
      • Arterial supply: Ulnar artery.
      • Action: Flexes the wrist.
      • Note: Absent in about 15% of the population.
    • Flexor Carpi Radialis
      • Bony attachments: common flexor tendon on the humerus, base of the 2nd metacarpal.
      • Innervation: Median nerve (C6, C7).
      • Arterial supply: Ulnar artery.
      • Action: Flexes the wrist, abducts the hand.
    • Flexor Carpi Ulnaris
      • Bony attachments: medial epicondyle of the humerus, medial aspect of the olecranon and posterior border of the ulnar shaft, and pisiform, hook of hamate, and proximal 5th metacarpal.
      • Innervation: Ulnar nerve.
      • Arterial supply: Ulnar artery.
      • Action: Flexes the wrist, adducts the hand.
      • Important relationships: The ulnar nerve passes between the two heads of the flexor carpi ulnaris as it enters the anterior compartment of the forearm (cubital tunnel).
    • Flexor Digitorum Superficialis
      • Bony attachments: common flexor tendon, coronoid process of the ulna, and middle phalanges of the 2nd to 5th digits.
      • Innervation: Median nerve (C8, T1) for digits 2 & 3, and Ulnar nerve for digits 4 & 5.
      • Arterial supply: Ulnar artery and Anterior Interosseous artery.
      • Action: Flexes the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints.
    • Flexor Pollicis Longus
      • Bony attachments: interosseous membrane, and anterior radius, and base of the distal phalanx of the thumb.
      • Innervation: Median nerve (C8, T1).
      • Arterial supply: Anterior Interosseous artery.
      • Action: Flexes the metacarpophalangeal and interphalangeal joints of the thumb.
    • Pronator Quadratus
      • Bony attachments: distal anteriomedial ulna, and distal anterior radius.
      • Innervation: Median nerve (C6, C7).
      • Arterial supply: Anterior Interosseous artery.
      • Action: Pronates the forearm.

    Arteries and Veins of the Anterior Compartment

    • Ulnar Artery
      • Begins in the cubital fossa as a terminal branch of the brachial artery.
      • Leaves the cubital fossa by passing deep to the ulnar head of the pronator teres, which separates it from the median nerve.
      • In the upper forearm, it is deeply located and passes deep to the superficial and intermediate muscles of the anterior compartment.
      • In the lower forearm, it is more superficial.
      • The tendon of the flexor carpi ulnaris and the ulnar nerve are medial to the ulnar artery, and the tendons of the flexor digitorum superficialis are lateral to it.
      • Along most of its course, it is accompanied by the ulnar nerve (nerve lies medial to the artery).
      • Enters the palm of the hand anterior (superficial) to the flexor retinaculum with the ulnar nerve and ends in the hand by forming the superficial palmar arch.
    • Branches of the Ulnar Artery
      • Muscular branches: supply neighboring muscles along its course.
      • Anterior and posterior ulnar recurrent arteries: participate in arterial anastomosis around the elbow joint.
      • Common interosseous artery: short branch that originates from the proximal part of the ulnar artery and divides into anterior and posterior interosseous arteries.
      • Palmar and dorsal carpal branches: anastomose with corresponding branches of the radial artery and supply the wrist.
    • Ulnar Nerve
      • Enters the anterior forearm by passing between the humeral and ulnar heads of the flexor carpi ulnaris (cubital tunnel).
      • Along most of its course in the forearm, it is accompanied by the ulnar artery (artery lies lateral to the nerve).
      • In the upper forearm, it is more deeply located (between the flexor carpi ulnaris and flexor digitorum profundus).
      • In the lower forearm, it is more superficial and lies between the tendon of the flexor carpi ulnaris (medial to the nerve) and the ulnar artery (lateral to the nerve).
      • Enters the palm of the hand by passing anterior (superficial) to the flexor retinaculum.

    Flexor Retinaculum (Transverse Carpal Ligament)

    • Strong fibrous band on the anterior aspect of the wrist.
    • Attaches medially to the pisiform and hook of hamate.
    • Attaches laterally to the scaphoid and trapezium.
    • Transforms the anterior, concave surface of the carpus into an osteofibrous tunnel (carpal tunnel/canal) and holds the median nerve and tendons of the long flexor muscles of the thumb and fingers (surrounded by their synovial sheaths).
    • Compression of the median nerve at this level causes carpal tunnel syndrome.

    Contents of the Carpal Tunnel

    • 4 tendons of the flexor digitorum superficialis.
    • 4 tendons of the flexor digitorum profundus.
    • Tendon of the flexor pollicis longus.
    • Median nerve.
    • The tendon of the flexor pollicis longus has its own synovial sheath (radial bursa).
    • The 4 tendons of the flexor digitorum superficialis and 4 tendons of the flexor digitorum profundus share the same synovial sheath (common flexor sheath or ulnar bursa).

    The Posterior Compartment of the Forearm

    • Extensor Retinaculum
      • Thickening of the deep fascia of the forearm that stretches across the back of the wrist.
      • Holds long extensor tendons in position and prevents them from bowstringing as they cross the wrist joint.
      • Converts the grooves on the posterior aspects of the distal ends of the radius and ulna into 6 separate compartments (tunnels) for the long extensor tendons (surrounded by synovial sheaths).

    Muscles of the Posterior Compartment

    • Extensor Digitorum
      • Bony attachments: common extensor tendon on the humerus, and extensor expansion of the 2nd-5th digits.
      • Innervation: Radial nerve (C7

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    Description

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