Sample chapter selective anatomy prep manual for undergraduates 1e by vishram singh to order call sms at 91 8527622422
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  • 1. Nerves of the Upper Limb Enumerate 5 main nerves that supply the upper limb. These are: Axillary nerve Musculocutaneous nerve Radial nerve Median nerve Ulnar nerve Describe the axillary nerve in brief and discuss its applied anatomy. C5 AXILLA The axillary nerve is the branch of posterior cord of brachial plexus (Fig. 7.1). Root Value Ventral rami of C5 and C6. C6 Shoulder joint SCAPULAR REGION Posterior branch Anterior branch Course and Relations Pseudoganglion Deltoid The axillary (or circumflex) nerve arises Nerve to teres muscle minor from the posterior cord of brachial plexus Skin over lower Upper lateral posterior to 3rd part of axillary artery. It half of deltoid cutaneous nerve passes posteriorly through the quadrangular of arm to skin over space. Here it lies below the capsule of the the lower half shoulder joint. As it is about to pass behind of the deltoid the surgical neck of humerus, it terminates Fig. 7.1 Axillary nerve and its main branches. by dividing into anterior and posterior branches. The anterior branch (along with posterior circumflex artery) runs deep to deltoid muscle and supplies deltoid muscle and skin over it. The posterior branch supplies posterior part of deltoid and teres minor muscles. It pierces deep fascia to become upper lateral cutaneous nerve of arm. Branches Muscular To deltoid and teres minor. Nerves to teres minor possesses pseudoganglion. Chapter-07.indd 57 11/7/2013 3:43:24 PM
  • 2. 58 Selective Anatomy Prep Manual for Undergraduates Cutaneous Upper lateral cutaneous nerve of arm Sensory innervation of skin over the lower half of deltoid Applied Anatomy The damage of axillary nerve in inferior dislocation of the shoulder joint and fracture of surgical neck of humerus will result into: Loss of rounded contour of shoulder Prominence of greater tubercle of humerus Loss of cutaneous sensations over lower half of deltoid “regimental badge area of sensory loss” Give a brief account of musculocutaneous nerve. See p. 28. Describe the radial nerve under the following headings: (a) Root value, (b) Origin, course, and relations, (c) Branches and distribution, and (d) Applied anatomy. The radial nerve is the thickest and largest nerve of the upper limb (Fig. 7.2). Root Value Ventral rami of C5, C6, C7, C8, and T1. Section I UPPER LIMB Origin, Course, and Relations It arises from the posterior cord of brachial plexus in axilla behind the 3rd part of the axillary artery. It is the thickest and largest branch of the brachial plexus. It courses successively through 3 regions: axilla, radial groove on the back of arm, and front of forearm. On the front of forearm, it ends by dividing into superficial and deep terminal branches. The course and relations of radial nerve in 3 regions traversed by it are as follows: Axilla In the axilla, the radial nerve lies against the muscles forming the posterior wall of axilla, i.e., subscapularis, teres major, and latissimus dorsi. Then it passes through the lower triangular space between teres major, long head of triceps brachii, and shaft of humerus. In axilla, it gives two muscular branches to supply long and medial heads of triceps and one cutaneous branch (posterior cutaneous nerve of arm). Radial groove The radial nerve from axilla, enters into the radial groove through the lower triangular space, where it lies between the long and medial heads of triceps brachii along with profunda brachii artery. It leaves the radial groove by piercing the lateral intermuscular septum. In the radial groove, it gives 3 muscular branches to supply long and medial heads of triceps and anconeus and 2 cutaneous branches, viz., lower lateral cutaneous nerve of arm and posterior cutaneous nerve of forearm. Front of arm The radial nerve enters the lower anterolateral part of the front of arm and lies between brachialis on the medial side and brachioradialis and extensor carpi radialis longus on the lateral side. It supplies all these muscles. Forearm The radial nerve enters the cubital fossa where in front of lateral epicondyle it ends by dividing into two terminal branches: (a) superficial terminal branch (superficial radial nerve) and (b) deep terminal branch (posterior interosseous nerve). Chapter-07.indd 58 11/7/2013 3:43:24 PM
  • 3. Nerves of the Upper Limb 59 C5 C6 C7 C8 T1 AXILLA Posterior cutaneous nerve of arm Triceps (long head) Triceps (medial head) Triceps (lateral head) ARM Posterior cutaneous nerve of forearm Brachialis (small lateral part) Brachioradialis Ext. carpi radialis longus Elbow joint Deep terminal branch (Posterior interosseous nerve) FOREARM Pseudoganglion HAND Ext. carpi radialis brevis Supinator Ext. digitorum Ext. digiti minimi Ext. Carpi ulnaris Abductor pollicis longus Ext. pollicis brevis Ext. indicis Distal radioulnar and wrist joints Superficial terminal branch (Superficial radial nerve) Skin of the lateral side of hand and lateral 3½ digits except their nail-beds Fig. 7.2 Radial nerve and its main branches. Superficial branch (superficial radial nerve) It is regarded as the downward continuation of the trunk of radial nerve. It runs on the lateral side of the front of forearm accompanied by the radial artery in the upper 2/3rd of forearm with radial artery being on its medial side. About 7 cm above the wrist, it curves posteriorly deep to tendon of brachioradialis to reach the anatomical snuff box. Here, it divides into 4 or 5 digital branches, which supply the skin of lateral half of dorsum of hand and lateral 2½ digits till their distal interphalangeal joints. Branches and Distribution Section I UPPER LIMB Deep terminal branch (posterior interosseous nerve) It lies in the lateral part of cubital fossa, where it supplies extensor carpi radialis brevis and supinator muscles. Then it enters into the back of forearm by passing through supinator muscle. Here, it supplies abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus, extensor digitorum, extensor indicis, extensor digiti minimi, and extensor carpi ulnaris. At the back of wrist, it ends in a pseudoganglion, branches of which supply the wrist and distal radioulnar joints. In axilla Muscular branches: Long and medial heads of triceps brachii Cutaneous branches: Posterior cutaneous nerve of arm Chapter-07.indd 59 11/7/2013 3:43:24 PM
  • 4. 60 Selective Anatomy Prep Manual for Undergraduates In radial groove Muscular Lateral head of triceps brachii Medial head of triceps brachii Anconeus Cutaneous Lower lateral cutaneous nerve of arm Posterior cutaneous nerve of forearm Vascular To profunda brachii artery In the arm Muscular Brachioradialis Extensor carpi radialis longus Lateral part of brachialis (proprioceptive) In the forearm Superficial terminal branch: Digital branches to supply the skin of lateral half of dorsum and lateral 3½ digits up to distal interphalangeal (DIP) joints. Deep terminal branch (posterior interosseous nerve): Muscular branches to all the muscles of back of forearm except anconeus, brachioradialis, and extensor carpi radialis longus. Applied Anatomy The effects of injury to the radial nerve, at different levels are given in Table 7.1. Table 7.1 Sites of radial nerve injury and their effects Site Causes Effects Axilla • Crutch palsy (prolonged • Loss of extension of elbow and wrist and use of crutches) digits • Fracture and dislocation of upper end of humerus • Wrist drop (Fig. 7.3) • Loss of supination in extended elbow Radial groove • Fracture midshaft of humerus • Wrongly placed intramuscular injection in radial groove • Wrist drop • Loss of supination in extended elbow Loss of sensations on lateral part of the dorsum of hand and lateral 3½ digits Proximal part of forearm • Fracture of proximal 1/3rd of radius • Compression of radial nerve in radial tunnel • Paralysis of most extensors of wrist and hand but no wrist drop Loss of sensations on the lateral part of dorsum of hand and lateral 3½ digits Section I UPPER LIMB Motor Chapter-07.indd 60 Sensory • Loss of sensations Posterior surface of the lower part of arm Narrow strip on the back of forearm Lateral part of the dorsum of hand and lateral 3½ digits 11/7/2013 3:43:24 PM
  • 5. Nerves of the Upper Limb Give the effects of injury to the posterior interosseous nerve. 61 Sensory loss The posterior interosseous nerve supplies all the muscles on the back of forearm except anconeus, brachioradialis, and extensor carpi radialis longus. The posterior interosseous nerve is commonly injured in fracture or dislocation of the head of radius. Effects Paralysis of all the muscles on the back of forearm except extensor carpi radialis longus, brachioradialis, and anconeus (which are supplied by radial nerve directly). There is no wrist drop because extensor carpi radialis longus being a powerful muscle keeps the wrist joint extended. Fig. 7.3 Wrist drop resulting from radial nerve injury. Describe the median nerve under the following headings: (a) Root value, (b) Course and relations, (c) Branches and distribution, and (d) Applied anatomy. The median nerve is so called because it runs in the median plane of the forearm. Root Value Ventral rami of C5 to C8 and T1 (Fig. 7.4). Course and Relations The median nerve is formed in the axilla by 2 roots—lateral root from lateral cord of brachial plexus and medial root from medial cord of brachial plexus. Then it courses successively through 4 regions: axilla, arm, forearm, and palm of the hand. The medial root crosses the axillary artery to join the lateral root. Axilla In the axilla, the median nerve lies first anterior and then lateral to the axillary artery. Forearm In the forearm, the median nerve passes through cubital fossa lying medial to the brachial artery. It leaves the fossa between the two heads of pronator teres before crossing superficial to the ulnar artery from medial to lateral side and giving its anterior interosseous branch below this. Then it passes deep to fibrous arch of flexor digitorum superficialis. Adheres to deep surface of flexor digitorum superficialis, leaves the muscle, along its lateral border. About 5 cm above the wrist it lies between the tendons of palmaris longus and flexor carpi radialis. It enters the palm through carpal tunnel under the flexor retinaculum, but in front of common synovial sheath enclosing tendons of flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP). Palm In the palm at the distal border of flexor retinaculum, it ends by dividing into lateral and medial terminal branches. Before dividing into terminal branches, the median nerve gives off a recurrent muscular branch from its lateral side. Chapter-07.indd 61 Section I UPPER LIMB Arm In the arm, the median nerve continues to run on the lateral side of brachial artery till the midarm (i.e., insertion of coracobrachialis), where it crosses in front of the brachial artery to lie on its medial side, and then passes anterior to elbow joint to enter into the forearm. 11/7/2013 3:43:24 PM
  • 6. 62 Selective Anatomy Prep Manual for Undergraduates Branches and Distribution (Fig. 7.4) In axilla No branch In Arm Muscular branch to pronator teres In the cubital fossa Muscular branches to: Flexor carpi radialis Palmaris longus Flexor digitorum superficialis In the forearm Anterior interosseous nerve, which supplies: Lateral half of FDP Flexor pollicis longus Pronator quadratus Palmar cutaneous branch to supply lateral 2/3rd of palm C5 C6 C7 C8 AXILLA T1 No branches ARM Section I UPPER LIMB Elbow joint Pronator teres Flexor carpi radialis Anterior interosseous nerve Flexor pollicis longus Flexor digitorum FOREARM profundus (lateral half) Palmaris longus Flexor digitorum superficialis Pronator quadratus Wrist joint Three thenar muscles Palmar cutaneous branch HAND 1st and 2nd lumbricals Palmar digital branches to lateral 3½ digits including their nail-beds Fig. 7.4 Median nerve and its main branches. Chapter-07.indd 62 11/7/2013 3:43:25 PM
  • 7. Nerves of the Upper Limb 63 In the palm Recurrent muscular branch, which supplies muscles of thenar eminence, viz. abductor pollicis brevis, flexor pollicis brevis and opponens pollicis. Lateral terminal branch, which gives off digital nerves to supply both the sides of thumb and radial side of index finger. Note: The digital branch to lateral side of index finger also supplies 1st lumbrical muscle. Medial terminal branch, which gives off digital nerves to supply the adjacent sides of index and middle fingers and adjacent sides of index and little fingers. Note: The digital nerve to adjacent side of middle and ring finger also supplies 2nd lumbrical muscle. N.B. The median nerve in the palm supplies: (a) all thenar muscles, (b) 1st and 2nd lumbricals, (c) skin of the lateral half of palm, and (d) skin of the lateral 3½ fingers including dorsal aspects of their distal phalanges. Applied Anatomy The effects of lesion to the median nerve depends upon the site of lesion (Table 7.2). Table 7.2 Effects of lesions of the median nerve Causes Effects Elbow • Supracondylar fracture of humerus • Entrapment of nerve between the two heads of pronator teres/FDS • Loss of pronation • Benediction deformity of hand (i.e., loss of flexion of PIP and DIP joints of index and middle finger, when one makes fist) • Ape-thumb deformity of hand (ape hand/simian hand deformity), i.e., the thumb lies in position of adduction, lateral rotation, and in line with other digits. It cannot be opposed Wrist • Above the wrist • Suicidal cuts • In carpal tunnel • Compression in carpal tunnel • Ape-thumb deformity of hand (i.e., thumb is adducted and laterally rotated – also see above) • Carpal tunnel syndrome Burning pain or pins and needles (paraesthesia) in lateral 3½ digits on their palmar aspects Wasting of thenar muscles No paraesthesia over the thenar eminence N.B. In case of suicidal cut above wrist, there is sensory loss over the thenar eminence because palmar cutaneous nerve is given just above the flexor retinaculum; but in case of carpal tunnel syndrome there is no sensory loss, over thenar eminence for the same reason. Section I UPPER LIMB Site of lesion Write a short note on carpal tunnel syndrome. It occurs due to compression of median nerve in the carpal tunnel. The carpal tunnel is an osseofibrous tunnel formed by the anterior concavity of the corpus bridged by the flexor retinaculum. This tunnel Chapter-07.indd 63 11/7/2013 3:43:25 PM
  • 8. 64 Selective Anatomy Prep Manual for Undergraduates is tightly packed with long flexor tendons of the fingers with their surrounding synovial sheaths and the median nerve. Clinical Features Painful paraesthesia (i.e., burning pain or pins and needles) along the distribution of the median nerve to the palm and lateral 3½ fingers. Weakness and wasting of thenar muscles. No paraesthesia over the skin of thenar eminence because this area of skin is supplied by the palmar cutaneous branch of median nerve, which arises in the forearm proximal to flexor retinaculum. It is more frequent in women than men. Intermittent attacks of pain are more common at night. N.B. The causes of compression of median nerve in carpal tunnel include tenosynovitis and thickening of synovial sheaths of the long flexor tendons, myxedema, arthritic changes in the carpal bones, etc. Describe the ulnar nerve under the following headings: (a) Root value, (b) Course and relations, (c) Branches and distribution, and (d) Applied anatomy. The ulnar nerve is so named because it runs along the ulnar side of the upper limb. Root Value Ventral rami of C8 and T1 (Fig. 7.5). It also gets contribution from ventral ramus of C7. Course and Relations It is the continuation of the medial cord of brachial plexus in the axilla. It courses successively through 4 regions: axilla, arm, forearm, and hand, where it terminates by dividing into superficial and deep branches. The course and relations of ulnar nerve in these regions are as follows: Section I UPPER LIMB Axilla In axilla, the ulnar nerve lies between the axillary vein and axillary artery on a deeper plane, medial to 3rd part of axillary artery. Arm It enters the arm by running downwards on the medial side of the brachial artery in its proximal part. At the midarm (i.e., at the level of insertion of coracobrachialis), it pierces the medial intermuscular septum to enter the back of arm. Here it descends to run in a groove on the back of medial epicondyle of humerus, where it can be palpated. Forearm The ulnar nerve enters the front of forearm by passing between two heads of flexor carpi ulnaris. Here it lies on medial part of flexor digitorum profundus. It is accompanied by the ulnar artery on its lateral side in the lower 2/3rd of forearm. Hand The nerve enters the palm by passing superficial to the flexor retinaculum and medial to ulnar artery. At the distal border of flexor retinaculum, it ends by dividing into superficial and deep terminal branches. Branches and Distribution In axilla and arm No branches In forearm Muscular branches to supply: Chapter-07.indd 64 11/7/2013 3:43:25 PM
  • 9. Nerves of the Upper Limb C8 65 T1 AXILLA No branches ARM Elbow joint Flexor carpi ulnaris Flexor digitorum profundus FOREARM Dorsal cutaneous branch Palmar cutaneous branch Wrist joint HAND Skin of hypothenar eminence ST Muscles of hypothenar eminence DT Palmaris brevis 3rd and 4th lumbricals Skin of the medial side of the dorsum Interossei and adductor pollicis of hand and medial Palmar Joints of 1½ digits aspect of medial hand 1½ digits including their nail-beds Flexor carpi ulnaris Flexor digitorum profundus (medial half) Palmar cutaneous branch: It arises at about midforearm and provides cutaneous innervation to skin of the hypothenar eminence. Dorsal cutaneous branch: It arises about 5 cm above the wrist and gives off dorsal digital nerves to supply sensory innervation to dorsal aspects of the medial 1½ digits excluding their distal phalanges. In hand Superficial terminal branch, which supplies: Palmaris brevis muscle Cutaneous innervation to medial 1/3rd of palm and medial 1½ fingers, including their nail beds. Deep terminal branch, which supplies: Medial two lumbricals Chapter-07.indd 65 Section I UPPER LIMB Fig. 7.5 Ulnar nerve and its main branches (ST = superficial terminal branch, DT = deep terminal branch). 11/7/2013 3:43:25 PM
  • 10. 66 Selective Anatomy Prep Manual for Undergraduates Muscles of hypothenar eminence (abductor digiti minimi, flexor digiti minimi, and opponens digiti minimi) All the interossei (3 palmar and 4 dorsal) Adductor pollicis Applied Anatomy The effects of lesion to the ulnar nerve depend on the site of lesion. The details are given in Table 7.3. Table 7.3 Effects of the ulnar nerve lesions Site of lesion Causes Effects Elbow • Fracture dislocation of the elbow joint • Entrapment of nerve in the cubital tunnel* • Atrophy and flattening of hypothenar muscles • Loss of adduction of thumb • Loss of adduction and abduction of medial 4 digits • Ulnar claw hand • Loss of sensation on medial 1½ digits, both on the dorsum and palm of hand • Loss of sensation on anterior and posterior surfaces of medial 1½ digits including their nail beds Wrist • Cut wounds • Compression by volar carpal ligament • Compression in Guyon’s tunnel Same effects as in lesion at elbow except that there will be no loss of sensation on the medial side of dorsum of hand and posterior surfaces of medial 1½ digits Section I UPPER LIMB *Cubital tunnel: It is formed by a tendinous arch connecting the 2 heads of flexor carpi ulnaris. Chapter-07.indd 66 11/7/2013 3:43:25 PM