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Upper Limb Organization: Embryology, Innervation, and Muscles

This article explores the embryology, innervation, and muscles of the upper limb. It covers the development of the limb, the innervation of different muscle compartments, and the muscles of the arm, forearm, and hand.

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Upper Limb Organization: Embryology, Innervation, and Muscles

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  1. d-etre.blogspot.com Organization of the Upper Limb Audrone Biknevicius, Ph.D. Dept. Biomedical Sciences, OU HCOM at Dublin Clinical Anatomy Immersion 2014

  2. “Anatomical Tool-Kit” www2.warwick.ac.uk www.medicinenet.com www.telegraph.co.uk virtuallaboratory.colorado.edu www.cedars-sinai.edu

  3. Week 7 Week 5 RULE #1 Limbs are outgrowths of the ventral body wall that undergo distal growth and differentiation… and rotation [More detailed limb embryology in MS course]

  4. The upper limbs are innervated by : • Dorsal rami of spinal nn. • Ventral rami of spinal nn.

  5. DEVELOPMENTAL/EVOLUTIONARY BASIS Primitive Pectoral Limb Developmentally-dorsal limb mm. Stern Essential of Gross Anatomy Developmentally-ventral limb mm.

  6. DEVELOPMENTAL/EVOLUTIONARY BASIS • 90◦ lateral rotation (forearm mm. undergo incomplete rotation) • Limb adduction Stern Essential of Gross Anatomy

  7. RULE #2A: Ventral vs. dorsal limb mm. Developmentally-dorsal muscles: • Lie posterior to the long bones in anatomical position (* exceptions) * Developmentally-ventral muscles: • Lie anterior to the long bones in anatomical position Stern Essential of Gross Anatomy

  8. Anterior Upper Limb Muscle Compartments Humerus ARM Posterior Anterior FOREARM Radius Ulnar Posterior Anterior Stern Essential of Gross Anatomy HAND 5th metacarpal

  9. Anterior Humerus ARM Posterior Some posterior compartment mm. are found on the anterolateral aspect of the forearm (*brachioradialis, supinator) * Anterior FOREARM Radius Ulnar Posterior Anterior Stern Essential of Gross Anatomy No posterior compartment in the hand HAND 5th metacarpal

  10. Spinal nerve Dorsal primary ramus Ventral primary ramus (C5-T1) RULE #2B: Innervation of anterior vs. posterior compartment mm. Anterior division Posterior division Stern Essential of Gross Anatomy limb axis

  11. “Roots of BP” (=ventral rami) C5 C6 Trunks C7 U Divisions C8 M Cord Lat L T1 Post Med Anterior (ventral) division Posterior (dorsal) division Brachial Plexus (right side; simplified) “Randy Travis Drinks Cold Beer” TerminalBranches Stern Essential of Gross Anatomy

  12. “Roots of BP” (=ventral rami) C5 C6 Trunks C7 U Divisions C8 M Cord Lat L T1 Post Med Anterior (ventral) division Posterior (dorsal) division Brachial Plexus (right side; simplified) TerminalBranches Musculocutaneous n. Median n. Radial n. Stern Essential of Gross Anatomy Ulnar n.

  13. Anterior Musculocutaneous n. MOTOR INNERVATION Muscle Compartments of the Upper Limb Humerus Radial n. Posterior Anterior Median n. & Ulnar n. Radius Ulna Radial n. Posterior Ulnar n. & Median n. Stern Essential of Gross Anatomy Anterior 5th metacarpal Posterior

  14. Musculocutaneous Nerve (arm) All mm. in anterior (flexor) compartment of arm MRI of arm • Biceps brachii m. • Brachialis m. • Brachial a. • Humerus. • Triceps brachii m. www.med.umich.edu http://emedicine.medscape.com/article/1877731-overview#aw2aab6b3

  15. Radial Nerve (arm) All mm. in posterior (extensor) compartment of arm Radial nerve BB B TMed TLat TLong http://emedicine.medscape.com/article/1877731-overview#aw2aab6b3

  16. The brachialis m. is innervated by which division of the brachial plexus: : • Anterior division • Posterior division www.aokainc.com

  17. The brachialis m. is innervated by: • Median n. • Musculocutaneous n. • Radial n. • Ulnar n. www.aokainc.com

  18. The triceps brachii m. is innervated by: • Musculocutaneous n. • Radial n.

  19. Radial Nerve (forearm) All mm. in posterior (extensor) compartment of forearm Also * brachioradialis and supinator mm. * http://emedicine.medscape.com/article/1877731-overview#aw2aab6b3

  20. Ulnar Nerve (forearm) • Limited mm. in anterior (flexor) compartment of forearm: • Flexor carpi ulnaris • Flexor digitorumprofundus(medial ½) Med 1/2 http://emedicine.medscape.com/article/1877731-overview#aw2aab6b3

  21. Median Nerve (forearm) • All anterior (flexor) compartment mm. of forearm except: • Flexor carpi ulnaris m. • Flexor digitorumprofundus m. (med ½) en.wikipedia.org http://emedicine.medscape.com/article/1877731-overview#aw2aab6b3

  22. RULE #2C www.acacpt.com

  23. The extensor digitorum m. lies in the posterior compartment, originates on the lateral epicondyle, and is innervated by: Lateral epicondyle • Median n. • Musculocutaneous n. • Radial n. • Ulnar n. Extensor digitorum m.

  24. “Be specific” thepainsource.com

  25. The flexor carpi radialis m. is in the anterior compartment, attaches to the medial epicondyle, and is innervated by: • Median n. • Radial n. • Ulnar n. www.rad.washington.edu

  26. The flexor digitorum profundus m. is the anterior compartment, attaches to the medial epicondyle, and is innervated by: • Median n. • Median n. & Ulnar n. • Ulnar n. healthfavo.com

  27. The brachioradialis and supinator mm. lie in the anterior aspect of the forearm but attach to the lateral epicondyle of the humerus. They are innervated by: • Median n. • Radial n. • Ulnar n. www.pelhamrehab.com

  28. Median Nerve (hand) • Limited hand mm.: • Thenar mm. • Lateral two lumbricals www.studyblue.com http://emedicine.medscape.com/article/1877731-overview#aw2aab6b3

  29. Ulnar Nerve (hand) cnx.org All hand mm. not innervated by median n. http://emedicine.medscape.com/article/1877731-overview#aw2aab6b3

  30. What about the most proximal muscles of the upper limb? medicine.academic.ru

  31. RULE #2D Developmentally-dorsal muscles: • Lie posterior to the long bones in anatomical position (* exception = brachioradialis, supinator) -or- • Arise from: • scapular blade ossification • vertebral column Developmentally-ventral muscles: • Lie anterior to the long bones in anatomical position -or- • Arise from: • coracoid ossification • sternum and costal cartilages * Stern Essential of Gross Anatomy

  32. Given the attachments of the latissimus dorsi muscle, its innervation will be from which of division of the brachial plexus: • Anterior division • Posterior division blog.corewalking.com

  33. Brachial Plexus (branches) C5 C6 supraspinatus & infraspinatus mm. C7 C8 T1 subscapularis m. latissimus dorsi m. subscapularis & teres major mm. deltoid & teres minor mm. suprascapular n. * ** upper subscapular n. thoracodorsal n. lower subscapular n. Stern Essential of Gross Anatomy axillary n.

  34. Given the attachments of the pectoralis muscles muscle, its innervation will be from which of division of the brachial plexus: • Anterior division • Posterior division www.bnchiro.com

  35. Brachial Plexus (branches) rhomboid mm. dorsal scapular n. C5 C6 suprascapular n. C7 * C8 pectoralis mm. lateral pectoral n. serratus anterior m. T1 musculoskeletal n. long thoracic n. medial n. medial pectoral n. pectoralis mm. ** upper subscapular n. thoracodorsal n. lower subscapular n. axillary n. ulnar n. radial n. Stern Essential of Gross Anatomy

  36. posterior anterior RULE #3 Proximal-to-Distal Rule Upper “roots” of the brachial plexus (C5-6 ventral rami) innervate proximal muscles (shoulder, elbow) Lower “roots” of the brachial plexus (C8-T1 ventral rami) innervate distal muscles (hand) Somatic motor nerve (GSE, with GSA) Cutaneous nerves (GSA, GVE, GVA)

  37. MYOTOME - group of muscles innervated by a single spinal nerve root sciartmag.blogspot.com

  38. Dorsal scapular n. C5 C6 Suprascapular n. C7 * C8 Lateral pectoral n. T1 Musculoskeletal n. Long thoracic n. Medial n. Medial pectoral n. ** Upper & lower subscapular nn. Thoracodorsal n. Axillary n. Ulnar n. Radial n. Brachial Plexus (all branches) Stern Essential of Gross Anatomy * Nerve to subclavius ** Medial brachial & antebrachial cutaneous nn.

  39. posterior anterior RULE #3 • “MIXED FUNCTIONAL MODALITIES” • Most terminal branches of the brachial plexus are mixed fiber nerves: • Somatic motor and somatic sensory (prioprioception) to skeletal mm. • Then, cutaneous innervation with somatic sensory and sympathetics to skin Somatic motor nerve (GSE, with GSA) Cutaneous nerves (GSA, GVE, GVA)

  40. Musculocutaneous n. Tank et al. Lippincott Williams & Wilkins Atlas of Anatomy

  41. Some purely cutaneous brs. of brachial plexus Tank et al. Lippincott Williams & Wilkins Atlas of Anatomy

  42. RULE #5: Dermatome vs. Cutaneous Nerve Distribution Segmental innervation (C5-T1) Dermatomes

  43. Segmental (Dermatome) Innervation of Upper Limb Foerster (1933) – based on clinical findings (used by neurologists) Keegan and Garrett (1948) – based on limb development Moore et al. Essential Clinical Anatomy

  44. Segmental (Dermatome) Innervation of Upper Limb Preaxial: C5-C7 Postaxial: C8-T1 Thumb: C6 3rd Digit: C7 5th Digit: C8 Moore et al. Essential Clinical Anatomy

  45. Dermatomes vs. Cutaneous Nerve Distribution Segmental innervation (C5-T1) Dermatomes Terminal branches Cutaneous nn.

  46. Peripheral (Cutaneous ) Innervation of Upper Limb Moore et al. Essential Clinical Anatomy Anterior Posterior

  47. Test for Peripheral Nerve Sensory Function: Ulnar n. – Tip of 5th digit (little finger) Median n. – Tip of 2nd digit (index finger) Radial n. – Webbing b/w thumb & index finger (dorsum) M U R

  48. C7 M C8 U C6 R

  49. Stretch Reflex Reciprocal inhibition of antagonist muscles apbrwww5.apsu.edu/

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