Gross Anatomy II - Week 3 Lecture Notes.pdf

Gross Anatomy II Home Upper Extremity Nerve Innervati… Week 14 Lecture Notes Week 3 Lecture Notes https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM...

Gross Anatomy II Home Upper Extremity Nerve Innervati… Week 14 Lecture Notes Week 3 Lecture Notes https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 1 of 27 :  The Forearm Objectives 1. Name the nerves that give sensory innervation to the skin of the forearm and describe their distribution 2. Name the superficial and deep veins of the forearm and indicated their location and termination 3. Describe the boundaries of the carpal tunnel and list its contents 4. Describe the origin, insertion, action and nerve supply of the muscles of the anterior compartment of the forearm 5. Describe the origin, course, anatomical relations and branches of the ulnar and radial arteries in the anterior compartment of the forearm 6. Describe the course, anatomical relations and branches of the median and ulnar nerves in the anterior compartment of the forearm 7. Discuss common disorders affecting the structures of the anterior compartment of the forearm 8. Describe the location of the extensor retinaculum and the contents of the osteofibrous compartments (tunnels) under it 9. Describe the origin, insertion, action and nerve supply of the muscles of the posterior compartment of the forearm 10. Describe the boundaries, floor and contents of the anatomical snuffbox 11. Describe the course and distribution of the superficial and deep branches of the radial nerve 12. Describe the blood supply of the posterior compartment of the forearm\ 13. Discuss common disorders affecting the structures of the posterior compartment of the forearm https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 2 of 27 :  Cutaneous Innervation of the Forearm (Figure 3.1) lateral cutaneous nerve of forearm (lateral antebrachial cutaneous nerve). branch of musculocutaneous nerve medial cutaneous nerve of forearm (medial antebrachial cutaneous nerve). branch of medial cord of brachial plexus posterior cutaneous nerve of forearm (posterior antebrachial cutaneous nerve). branch of radial nerve https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 3 of 27 :  Figure 3.1: Cutaneous Innervation of the Forearm Superficial Veins of the Forearm cephalic vein (lateral) basilic vein (medial median cubital vein frequently used for venipuncture: lies superficial to cubital fossa (in superficial fascia) runs superiorly and medially from cephalic vein to basilic vein median antebrachial vein: ascends along anterior midline of forearm and drains into median cubital vein https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 4 of 27 :  Compartments of the Forearm (Figure 3.2) forearm is enclosed in a sheath of deep fascia (antebrachial fascia) interosseous membrane: thin, strong fibrous membrane that attaches to interosseous borders of radius and ulna (connects radius and ulna and gives attachment to deep forearm muscles) interosseous membrane, radius and ulna divide forearm into anterior and posterior compartments, which are surrounded by antebrachial fascia each compartment has its own muscles, nerves and blood vessels anterior compartment contains flexor and pronator muscles posterior compartment contains extensor and supinator muscles https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 5 of 27 :  Figure 3.2: Compartments of the forearm The Anterior Compartment of the Forearm Muscles of the Anterior Compartment: Superficial Layer Pronator Teres https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 6 of 27 :  Pronator Teres Bony Attachments: 1: humeral head: medial epicondyle and adjacent medial supracondylar ridge ulnar head: medial aspect of coronoid process 2: Midpoint of the lateral radius Innervation: Median nerve (C6, C7) Arterial supply: Ulnar artery Action: Pronates the forearm Important Relationships: The median nerve passes between two heads as it leaves cubital fossa (possible site of compression) Palmaris Longus (Note: Absent in about 15% of the population; Can be bilaterally or unilaterally absent) Bony Attachments: 1: Common flexor tendon on the humerus 2: Palmar aponeurosis, & flexor retinaculum Innervation: Median nerve (C7, C8) Arterial supply: Ulnar artery Action: Flexes the wrist Flexor Carpi Radialis Bony Attachments: 1: Common flexor tendon of humerus 2: Base of 2nd metacarpal Innervation: Median nerve (C6, C7) Arterial supply: Ulnar artery Action: Flexes the wrist, abducts the hand https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 7 of 27 :  Action: Flexes the wrist, abducts the hand Flexor Carpi Ulnaris Bony Attachments: 1 humeral head: medial epicondyle of humerus (common flexor tendon) ulnar head: medial aspect of olecranon and posterior border of ulnar shaft 2: Pisiform, hook of hamate, and proximal 5th metacarpal Innervation: Ulnar nerve Arterial supply: Ulnar artery Action: Flexes the wrist, adducts the hand Important Relationships: ulnar nerve passes between two heads as it enters anterior compartment of forearm (cubital tunnel) https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 8 of 27 :  https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 9 of 27 :  Intermediate Layer Flexor Digitorum Superficialis Bony Attachments: 1: Common flexor tendon, coronoid process of the ulna 2: Middle phalanges of 2nd to 5th digits In lower forearm, muscle belly gives rise to 4 tendons (for medial 4 digits), which enter hand through carpal tunnel (in distal forearm and carpal tunnel tendons for ring and middle fingers are superficial to tendons for index and little fingers). At. the level of proximal phalanges, tendons divide into 2 slips to allow passage of corresponding tendons of flexor digitorum profundus, then the two slips then attach to sides of middle phalanges of medial 4 digits. Innervation: Median nerve (C7, C8, T1) Arterial supply: Ulnar artery Action: Flexes the metacarpophalangeal and proximal interphalangeal joints Important Relationships: In lab, the median nerve can be located in between flexor digitorum superficialis and flexor digitorum profundus. Typically, it will be adhered to the underside of the muscle belly during dissection. https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 10 of 27 :  https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 11 of 27 :  Deep Layer Flexor Digitorum Profundus Bony Attachments: https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 12 of 27 :  1: Interosseous membrane and proximal posteromedial ulna 2: Distal phalanx of 2nd-5th digits in lower forearm, muscle belly gives rise to 4 tendons (for medial 4 digits), which enter hand through carpal tunnel. The tendons of flexor digitorum profundus pass between 2 slips of corresponding tendons of flexor digitorum superficialis, and then insert into bases of distal phalanges of medial 4 digits. Innervation: Dual Innervation - Median nerve for digits 2 & 3 (C8, T1), 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: 1: Interosseous membrane and (anterior) radius 2: The tendon will pass through the carpal tunnel and insert into the base 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: 1: Distal anteriomedial ulna 2: Distal anterior radius Innervation: Median nerve (C6, C7) Arterial supply: Anterior Interosseous artery Action: Pronates the forearm https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 13 of 27 :  Action: Pronates the forearm Arteries and Veins of the Anterior Compartment Ulnar Artery It begins in cubital fossa (terminal branch of brachial artery). It then leaves the cubital fossa by passing deep to ulnar head of pronator teres, which separates it from median nerve. In the upper forearm, it is deeply located and passes deep to superficial and intermediate muscles of anterior compartment. In the lower forearm, it is more superficial. The tendon of flexor carpi ulnaris and the ulnar nerve are medial to ulnar artery and tendons of flexor digitorum superficialis are lateral to ulnar artery. Along most of its course, it is accompanied by ulnar nerve (nerve lies medial to artery). It enters the palm of hand anterior (superficial) to flexor retinaculum with ulnar nerve and ends in the hand by forming the superficial palmar arch. https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 14 of 27 :  Branches of the Ulnar Artery: muscular branches- supply neighboring muscles along its course anterior and posterior ulnar recurrent arteries- participate in arterial anastomosis around elbow joint common interosseous artery- short branch that originates from proximal part of ulnar artery and divides into anterior and posterior interosseous arteries anterior interosseous artery-runs inferiorly, on anterior aspect of interosseous membrane, with anterior interosseous nerve. At proximal border of pronator quadratus pierces interosseous membrane and enters posterior compartment of forearm, and then anastomoses with terminal part of posterior interosseous artery posterior interosseous artery- passes posteriorly, between ulna and radius, and above superior border of interosseous membrane, to enter posterior compartment of forearm palmar and dorsal carpal branches- anastomose with corresponding branches of radial artery and supply wrist. (We will discuss these when the hand is discussed) https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 15 of 27 :  Radial Artery begins in cubital fossa (terminal branch of brachial artery) in upper forearm is covered by brachioradialis and passes superficial to pronator teres close to its insertion in lower forearm, it is superficial and lies between tendon of brachioradialis (lateral to artery) and tendon of flexor carpi radialis (medial to artery) site for taking radial pulse. in middle part of forearm it is accompanied by superficial branch of radial nerve (nerve lies lateral to artery) winds around lateral aspect of wrist to reach dorsum of hand branches: muscular branches-supply neighboring muscles along its course radial recurrent artery- participates in arterial anastomosis around elbow joint superficial palmar branch (discussed with the hand) - originates just above wrist and enters palm of hand by passing through or superficial to thenar muscles and completes superficial palmar arch on lateral side palmar and dorsal carpal branches (discussed with the hand)- anastomose with corresponding branches of ulnar artery and supply wrist Deep Veins of the Forearm radial and ulnar arteries are accompanied by two veins each (radial and ulnar veins or venae comitantes [accompanying veins] of radial and ulnar arteries) there are numerous connections between two radial veins and between two ulnar veins radial and ulnar veins receive tributaries corresponding to branches of arteries and drain deep tissues of forearm in cubital fossa, radial and ulnar veins join to form two brachial veins (venae comitantes of brachial artery) and are connected to median cubital vein (superficial vein) Nerves of the Anterior Compartment Median Nerve https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 16 of 27 :  Median Nerve exits cubital fossa by passing between humeral and ulnar heads of pronator teres descends in forearm between flexor digitorum superficialis and flexor digitorum profundus just proximal to wrist, it emerges from underneath flexor digitorum superficialis and enters hand by passing through carpal tunnel branches: muscular branches -supply pronator teres, flexor carpi radialis, palmaris longus and flexor digitorum superficialis articular branch to elbow joint palmar branch: originates just proximal to wrist and passes superficial to flexor retinaculum and supplies skin of central, depressed area of palm of hand anterior interosseous nerve: originates from median nerve as it emerges from pronator teres (upper forearm) and runs inferiorly on anterior surface of interosseous membrane with anterior interosseous artery and passes deep to pronator quadratus and ends on anterior surface of carpus. It supplies flexor pollicis longus, pronator quadratus and lateral half of flexor digitorum profundus and gives articular branches to distal radioulnar and wrist joints Ulnar Nerve enters anterior forearm by passing between humeral and ulnar heads of flexor carpi ulnaris (cubital tunnel) along most of its course in forearm, it is accompanied by ulnar artery (artery lies lateral to nerve) in upper forearm is more deeply located (between flexor carpi ulnaris and flexor digitorum profundus) in lower forearm is more superficial and lies between tendon of flexor carpi ulnaris (medial to nerve) and ulnar artery (lateral to nerve) , and it enters palm of hand by passing anterior (superficial) to flexor retinaculum branches: muscular branches - supply flexor carpi ulnaris and medial half of flexor digitorum profundus articular branch to elbow joint palmar branch - passes superficial to flexor retinaculum, and supplies skin on medial part of palm, at base of hypothenar eminence dorsal branch (larger than palmar branch) , curves around ulna (deep to tendon of https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 17 of 27 :  dorsal branch (larger than palmar branch) , curves around ulna (deep to tendon of flexor carpi ulnaris) and supplies skin on medial part of dorsum of hand and dorsal surfaces of medial 2½ (or 1½) digits (digital branches do not extend far beyond proximal interphalangeal joints) anterior to flexor retinaculum, ulnar nerve ends by dividing into superficial and deep terminal branches Flexor Retinaculum (Transverse Carpal Ligament) strong fibrous band on anterior aspect of wrist attaches medially to pisiform and hook of hamate attaches laterally to scaphoid and trapezium transforms anterior, concave surface of carpus into an osteofibrous tunnel (carpal tunnel/canal) and holds median nerve and tendons of long flexor muscles of thumb and fingers (surrounded by their synovial sheaths) compression of median nerve at this level causes carpal tunnel syndrome laterally, it splits into two laminae (superficial and deep) that create a separate tunnel for tendon of flexor carpi radialis (with its synovial sheath) https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 18 of 27 :  Contents of the Carpal Tunnel 4 tendons of flexor digitorum superficialis 4 tendons of flexor digitorum profundus tendon of flexor pollicis longus median nerve tendon of flexor pollicis longus has its own synovial sheath (radial bursa) 4 tendons of flexor digitorum superficialis and 4 tendons of flexor digitorum profundus share the same synovial sheath (common flexor sheath or ulnar bursa) The Posterior Compartment of the Forearm Extensor Retinaculum thickening of deep fascia of forearm that stretches across back of wrist à holds long extensor tendons in position and prevents them from bowstringing as they cross wrist joint https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 19 of 27 :  wrist joint converts grooves on posterior aspects of distal ends of radius and ulna into 6 separate compartments (tunnels) for long extensor tendons (surrounded by synovial sheaths) Muscles of the Posterior Compartment Superficial Layer Extensor Digitorum Bony Attachments: 1: Common extensor tendon of lateral humerus 2: Extensor expansion of 2nd-5th digits Innervation: Radial nerve (C7, C8) Arterial supply: Interosseous artery Action: Extends the metacarpophalangeal, proximal interphalangeal and distal interphalangeal joints of the 2nd-5th digits and extends the wrist Extensor Carpi Ulnaris Bony Attachments: 1: Common extensor tendon on humerus and proximal posterior ulna 2: Proximal medial 5th metacarpal Innervation: Radial nerve (C7, C8) Arterial supply: Ulnar artery Action: Extends the wrist, adducts the hand Extensor Carpi Radialis Longus Bony Attachments: 1: Common extensor tendon on humerus https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 20 of 27 :  2: Dorsum of 2nd metacarpal Innervation: Radial nerve (C6, C7) Arterial supply: Radial artery Action: Extends the wrist, abducts the hand Extensor Carpi Radialis Brevis Bony Attachments: 1: Common extensor tendon of the humerus 2: Dorsum of 3rd metacarpal Innervation: Posterior interosseous n., branch of radial n. (C7, C8) Arterial supply: Radial artery Action: Extends the wrist, abducts the hand Extensor Digiti Minimi Bony Attachments: 1: Common extensor tendon on humerus 2: 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 a muscle of posterior compartment of 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 https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 21 of 27 :  abduct ulna during pronation of forearm Deep Layer Extensor Indicis Bony Attachments: 1: Interosseous membrane and distal ulna 2: 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: 1: Interosseous membrane and distal radius 2: Proximal phalanx of thumb Innervation: Radial nerve Arterial supply: Interosseous artery Action: Extends the metacarpophalangeal joint of the thumb https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 22 of 27 :  Extensor Pollicis Longus Bony Attachments: 1: Interosseous membrane and mid shaft of the ulna 2: Distal phalanx of thumb Innervation: Radial nerve Arterial supply: Interosseous artery Action: Extends the thumb at the interphalangeal joint Supinator Bony Attachments: 1: Distal lateral humerus, proximal ulna, radial ligament 2: Proximal lateral radius Innervation: Radial nerve (C7,C8) Arterial supply: Recurrent interosseous artery Action: Supinates the forearm https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 23 of 27 :  Compartments (Tunnels) Under the Extensor Retinaculum (from lateral to medial) 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 cross section of distal forearm: extensor tunnels https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 24 of 27 :  Anatomical Snuffbox triangular depression on lateral side of wrist (becomes evident when thumb is fully extended) bounded laterally by tendons of abductor pollicis longus and extensor pollicis brevis à bounded medially by tendon of extensor pollicis longus styloid process of radius, scaphoid, trapezium and base of 1st metacarpal are found on its floor (from proximal to distal) radial artery crosses anatomical snuff box and passes deep to tendons that form its boundaries à its pulse can be felt in this location superficial fascia over anatomical snuffbox contains branches of superficial radial nerve and origin of cephalic vein from dorsal venous arch of hand scaphoid fractures (most commonly fractured carpal bone) cause tenderness in anatomical snuffbox on palpation https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 25 of 27 :  https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 26 of 27 :  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, it 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 arter 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 (digital branches do not extend far beyond proximal phalanges) 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, the nerve descends between superficial and deep muscles of posterior compartment of forearm à terminates on posterior aspect of wrist 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 à it 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 https://sites.google.com/view/grossanatomyii/week-3-lecture-notes 5/21/24, 3 58 PM Page 27 of 27 :