Anatomical partitioning has been found in the human biceps brachii, extensor carpi radialis longus and flexor carpi radialis muscles. The purpose of this study was to determine if the human extensor carpi ulnaris, flexor carpi ulnaris and flexor digitorum profundus are anatomically partitioned. Evidence for or against anatomical partitioning was obtained by observation of the architectural and innervation characteristics of each of the investigated muscles. Twelve samples (11 were used for extensor carpi ulnaris) of each specific muscle type were harvested from perfused human cadavers. The architectural characteristics of tendinous boundaries, muscle fiber direction, and muscle fiber angle magnitude were observed, measured and documented. Microdissection technique was used to investigate the primary nerve branching pattern throughout each muscle. A primary nerve branch to a specific muscle region indicated possible partitioning by innervation. The extensor carpi ulnaris was found to have a variable number of primary nerve branches. The extensor carpi ulnaris may have four partitions by innervation alone or three congruent partitions by innervation and muscle fiber architecture. The nerve to the flexor carpi ulnaris clearly innervates two architectural partitions within the muscle. The innervation pattern to the flexor carpi ulnaris is congruent with muscle fiber architecture characteristics indicating consistent anatomical partitioning within the flexor carpi ulnaris. Two muscle nerves innervate the flexor digitorum profundus with branches innervating the medial and lateral regions of the muscle. Up to eight architectural partitions were found in a medial-to-lateral direction.

1.
Bodine, S.C., R.R. Roy, D.A. Meadows, R.F. Zernicke, R.D. Sacks, M. Fournier, V.R. Edgerton (1982) Architectural, histochemical, and contractile characteristics of a unique biarticular muscle: The cat semitendinosus. J Neurophysiol 48/1: 192–201.
2.
Bremner, F.D., J.R. Baker, J.A. Stephens (1991) Effect of task on the degree of synchronization of intrinsic hand muscle motor units in man. J Neurophysiol 66: 2072–2083.
3.
Chanaud, C.M., C.A. Pratt, G.E. Loeb (1991) Functionally complex muscles of the cat hindlimb. Exp Brain Res 85: 300–313.
4.
Cope, T.C., A.J. Sokoloff, B.D. Clark (1996) The size principle of motor unit recruitment: Extent of its applicability; in Stuart, D.G., P.A. Pierce (eds): Motor Control VII. Tucson, West Press, pp 99–104.
5.
Eldred, E., M. Ounjian, R.R. Roy, V.R. Edgerton (1993) Tapering of the intrafascicular endings of muscle fibers and its implications to relay of force. Anat Rec 236: 390–398.
6.
English, A.W., W.D. Letbetter (1982) Anatomy and innervation patterns of cat lateral gastrocnemius and plantaris muscles. Am J Anat 164: 67–77.
7.
English, A.W., O.I. Weeks (1987) An anatomical and functional analysis of cat biceps femoris and semitendinosus muscles. J Morphol 191: 161–175.
8.
English, A.W., S.L. Wolf, R.L. Segal (1993) Compartmentalization of muscles and their motor nuclei: The partitioning hypothesis. Phys Ther 73: 857–867.
9.
Fritz, N., M. Illert, S. De La Motte, P. Reeh, P. Saggau (1989) Pattern of monosynaptic Ia connections in the cat forelimb. J Physiol 419: 321–351.
10.
Fritz, N., C. Schmidt, T. Yamaguchi (1992) Biomechanical organization of single motor units in two multi-tendoned muscles of the cat distal forelimb. Exp Brain Res 88: 411–421.
11.
Gans, C. (1982) Fiber architecture and muscle function. Exerc Sport Sci Rev 10: 160–207.
12.
Goldspink, G. (1977) Design of muscles in relation to locomotion; in Alexander, R.M., G. Goldspink (eds): Mechanics and Energetics of Animal Locomotion. London, Chapman & Hall, pp 1–22.
13.
Henneman, E., L.M. Mendell (1981) Functional organization of motoneuron pool and its inputs; in Brooks, V.B. (ed): Handbook of Physiology, vol 2: The Nervous System: Motor Control. Bethesda, American Physiology Society, pp 423–507.
14.
Herring, S.W., A.F. Grimm, B.R. Grimm (1979) Functional heterogeneity in a multipennate muscle. Am J Anat 154: 563–576.
15.
Hoffer, J.A., G.E. Loeb, N. Sugano, W.B. Marks, M.J. O’Donovan, C.A. Pratt (1987) Cat hindlimb motoneurons during locomotion. III. Functional segregation in sartorius. J Neurophysiol 57: 554–562.
16.
Hoffman, P., M. Illert, E. Wiedemann (1986) EMG patterns of cat forelimb muscles during target reaching and food taking movements. Neurosci Lett Suppl 26: S215.
17.
Letbetter, W.D. (1974) Influence of intramuscular nerve branching on motor unit organization in medial gastrocnemius muscle. Anat Rec 178: 402.
18.
Letbetter, W.D., A.W. English (1981) The relationship between peripheral intramuscular ‘compartments’ and spatial arrangement of biceps femoris and semitendinosus motor nuclei in the cat lumbar spinal cord. Soc Neurosci Abstr 7: 557.
19.
Liddel, E.G.T., C.S. Sherrington (1925) Recruitment and some other factors of reflex inhibition. Proc R Soc Lond B Biol Sci 97: 488–518.
20.
Lieber, R.L., B.M. Fazeli, M.J. Botte (1990) Architecture of selected wrist flexor and extensor muscles. J Hand Surg 15/2: 244–250.
21.
Lieber, R.L., M.D. Jacobson, B.M. Fazeli, R.A. Abrams, M.J. Botte (1992) Architecture of selected muscles of the arm and forearm: Anatomy and implications for tendon transfer. J Hand Surg 17/5: 787–798.
22.
Loeb, G.E. (1985) Motoneurone task groups: Coping with kinematic heterogeneity. J Exp Biol 115: 137–146.
23.
Loeb, G.E. (1990) The functional organization of muscles, motor units, and tasks; in Binder, M.D., L.M. Mendell (eds): The Segmental Motor System. New York, Oxford University Press, pp 23–35.
24.
McIntosh, J.S., M. Ringqvist, E.M. Schmidt (1985) Fiber type composition of monkey forearm muscle. Anat Rec 211: 403–409.
25.
McMahon, T., T. Pianta, L. Couch, S. Wolf, R. Segal, L. Mason, T. Craft, A. English, P. Catlin (1991) Normalized electromyographic activity in the human extensor carpi radialis longus and flexor carpi muscles: Differential activity; in Anderson, P.A., D.J. Hobart, J.V. Danoff (eds): Electromyographical Kinesiology: Proceedings of the 8th Congress of the International Society of Electrophysiological Kinesiology. Amsterdam, Excerpta Medica, pp 39–42.
26.
Powell, P.L., R.R. Roy, P. Kanim, M.A. Bello, V.R. Edgerton (1984) Predictability of skeletal muscle tension from architectural determinations in guinea pig hindlimbs. J Appl Physiol 57: 1715–1721.
27.
Richmond, F.J.R., V.C. Abrahams (1975) Morphology and enzyme histochemistry of dorsal muscles of the cat neck. J Neurophysiol 38: 1312–1321.
28.
Richmond, F.J.R., D.R.R. MacGillis, D.A. Scott (1985) Muscle-fiber compartmentalization in cat splenius muscles. J Neurophysiol 53: 868–885.
29.
Riek, S., P. Bawa (1992) Recruitment of motor units in human forearm extensors. J Neurophysiol 68/1: 100–108.
30.
Sacks, R.D., R.R. Roy (1982) Architecture of the hind limb muscles of the cat: Functional significance. J Morphol 173: 185–195.
31.
Schieber, M.H. (1993) Electromyographic evidence of two functional subdivisions in the rhesus monkey’s flexor digitorum profundus. Exp Brain Res 95: 251–260.
32.
Segal, R.L., S.L. Wolf, M.J. De Camp, M.T. Chopp, A.W. English (1991) Anatomical partitioning of three multiarticular human muscles. Acta Anat 142: 261–266.
33.
Serlin, D.M., M.H. Schieber (1993) Morphologic regions of the multitendoned extrinsic finger muscles in the monkey forearm. Acta Anat 146: 255–266.
34.
Stuart, D.G., T.M. Hamm, S. Vanden Noven (1988) Partitioning of the monosynaptic Ia EPSP connections with motor neurons according to neuromuscular topography: Generality and functional implications. Prog Neurobiol 30/5: 437–447.
35.
Triolo, R., R. Nathan, Y. Handa, M. Keith, R.R. Betz, S. Carroll, C. Kantor (1996) Challenges to clinical deployment of upper limb neuroprostheses. J Rehabil Res Dev 33/2: 111–122.
36.
Trotter, J.A. (1993) Functional morphology of force transmission in skeletal muscles. Acta Anat 146: 205–222.
37.
Warwick, R., P.L. Williams (1973) Gray’s Anatomy, ed 35 (British). Philadelphia, Saunders, 1973.
Copyright / Drug Dosage / Disclaimer
Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher.
Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug.
Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.
You do not currently have access to this content.