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Introduction to Nerves

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  • 1. Upper Limb I Introduction to Integument and Nerves; Superficial Muscles of the Back Dr. Art Dalley August 1722, 20042 (8:00 am) Moore & Dalley: Clinically-Oriented Anatomy, 4th ed. (COA4): pp. 4-14; 38-45; 668-669; 690-695; 679-685; 717-720 Sauerland: Grant’s Dissector, 12th ed.: pp. XIII-XVIII; 132-135; 185-188 Agur & DalleyAgur: Grant’s Atlas of Anatomy, 110th ed. (GA101): Figs. 1.18, 4.27, 4.40, 4.48-4.49, 4.51, 23, 270-271; 2Table 6.4 (p. 496), 6.4, 77; 296;6.6-6.7, 6.10, 6.29-6.30 418; 422-423; 442-443 Clemente: Anatomy: A Regional Atlas, 4th ed.: Figs. 13-15, 35-36, 623-629; 634 Dalley: Netter Atlas of Human Anatomy (book)/Interactive Atlas (CD-ROM), 2nd Ed. (and Clinical Atlas, Version 2.0 ): Plates 511; 148-149; 155b; 156a; 178-9; 160; 163; 166; 392-3, 395A, 448-452, 487, 510 (C99, C504, C510); 3rd ed (book)., Plates 153-154; 162B-163A, 186-7; 167; 173; 403-4; 407A; 462-6; 504, 528 Rohen, Yokochi & Lütjen-Drecoll: Color Atlas of Anatomy, 54th ed.: 18-2019, 21209-2140, 2182-2194, 224-6, 386, 38878 As a result of attending the audiovisual presentations, reading/viewing the textbook, atlas, and notes, and participating in the laboratory experience, VSM I students should understand and be able to: 1. Define, locate/recognize and describe the features, organization and function of the integument, subcutaneous tissue and deep fascia. Demonstrate that knowledge in the laboratory dissection by properly • reflecting skin ● cleaning muscles • cleaning muscles • locating superficial vessels and cutaneous nerves and stripping arteries. 2. Define and explain the anatomical basis/clinical significance of the following features of the skin, subcutaneous tissue and deep fascia: • cleavage (tension) lines (of Langer) • variations with regard to: • anatomical region • ● gender • race • ● nutritional state • fascial compartaments, with regard to: • function ● • innervation • musculovenous pump • physical findings (fulfillment of this part may await Introduction to N.S./Autonomic N.S.): • pallor, rubor, calor, dolor (incl. uding referred pain) 3. Define/distinguish: • nerve, nerve fiber, cell body, ganglion, nucleus, vasa nervorum 4. Differentiate: • central nervous system vs. peripheral nervous system • motor (efferent) vs. sensory (afferent) innervation, and basic motor effects and sensory modalities • cranial nerves vs. spinal nerves • somatic (parietal) vs. visceral innervation 5. Describe the formation and pattern of branching of the simple spinal nerve; explain the anatomical basis/clinical significance of the following: • Dermatomes • Cutaneous anesthesia 1
  • 2. • Motor paralysis (palsy) • Paresthesia 6. On the cadaver, identify and demonstrate: • the relationships, attachments, and nerve(s) supplying the superficial muscles of the back. By observing their attachments and the disposition of their muscle fibers, predict the action of the muscles. • the superficial veins and cutaneous nerves of the upper limb 2
  • 3. Introduction to The Integumentary System and Fascia I. Skin (COA4 Fig. I.6 on Page 13; Netter Plate 511 [in 2nd . ed. only]) --largest and the most superficial of our organs --medical specialty dedicated to the study of the skin = dermatology A. General functions: containment, protection (against abrasion, infection, U.V. radiation, dehydration), sensation, thermoregulation, vitamin D production B. Layers: 1. epidermis a. transparent, avascular layer 2. dermis a. structures occurring within the dermis --sweat glands, hair follicles & arrector pili muscles C. Cleavage (tension) lines (of Langer): (COA4 Fig. I.7 on page 14)) 1. anatomical basis -- predominant direction of collagen bundles 2. general direction of lines in various regions of body -- parallel skin creases; transverse in neck & trunk, longitudinal in limbs between joints 3. clinical significance --incisions or lacerations parallel to lines generally gape less widely and tend to heal with less scar formation D. Specializations: hair, nails I. Subcutaneous Tissue (“superficial fascia”, “tela subcutanea”) (COA4 Fig I.6; Netter Pl. 511) E. Composition, characteristics 1. skin ligaments (L., retinacula cutis) 2. subcutaneous bursae F. Regional, sexual, racial and nutritional variations in placement and thickness G. Reflection of skin and superficial fascia in dissection II. Deep fascia (Netter Plates 448-9, 487, 510462-3, 504, 528; GA11 Fig. 6.10) A. Composition, appearance, modifications 3
  • 4. 1. intermuscular septa, extensor & flexor retinacula 2. aponeuroses 3. tendon sheaths, pulleys and muscular trochleae B. Fascial (functional) compartments of the limbs, muscular sheaths, intermuscular septa (Netter Plate 487; 504, GA11 Fig. 6.10) -- role in relationship to the "musculovenous pump" (COA4 Fig. I.21 on Page 36) C. Sheaths of neurovascular bundles Introduction to Nerves The Nervous System: --can be divided into: (COA4 Fig. I.24 on Page 40) • Central Nervous System (CNS) – brain – spinal Cordcord • Peripheral Nervous System (PNS) (GA11 Figs, 4.40, 4.51; Netter 153-154)) – nerves (a collection of axons) – ganglia (a collection of nerve cell bodies outside the CNS) -- is composed primarily of: • Neurons --cell bodies --axons = nerve fibers Nerves: (COA4 Fig. I.27 on Page 42) Bundles of nerve fibers (axons) outside the central nervous system, plus: • connective tissue to bind them • blood vessels (vasa nervorum) to supply them Classification of Nerves: 1 1. Exit from bony encasement of CNS -- cranial vs. spinal nerve 2. Function of the majority of contained fibers 1 -- motor (efferent) vs. sensory (afferent) nerves 3. Derivation from single or multiple spinal cord segments 4
  • 5. -- segmental vs. peripheral nerves 4. Destination of contained fibers 1 -- somatic (or parietal) vs. visceral (or splanchnic) nerves [Looking at the first two of these:] 1. Exit from bony encasement of CNS: Cranial vs. spinal nerves Cranial nerves: (COA4 Table 9.1 on Pages 1084-85; Netter Plate 112; GA11 p. 796) • Exit cranial cavity via openings (foramina) in cranium (skull) • 12 pairs • I.D.Identified by name, Roman numeral, or both • All but one arise from brain • Purely sensory, purely motor, or mixed Spinal nerves: (COA4 Fig. I.27 on Page 42, Netter Plates 148-149A153-154A; GA11 4.40 & 4.51) • Exit from the vertebral column (spine) • Identified.D. by a letter (region) and a number (sequence) • All arise from the spinal cord • 31 pairs: 8 Cervical (C1 - C8) 12 Thoracic (T1 - T12) 5 Lumbar (L1 - L5) 5 Sacral (S1 - S5) 1 Coccygeal (Co) 2. Function of the majority of the contained fibers: Sensory vs. motor nerves Example of a sensory nerve: any cutaneous nerve (e.g., supraclavicular nn.) Example of a motor nerve: nerve to quadratus femorius Neither are purely sensory or motor! Composition of a simple spinal nerve (e.g., T2 – L1) (GA110 Fig. 1.1820; Netter Plates 166, 241173, 250)  arises by means of posterior and anterior roots: 5
  • 6. A. Posterior roots of spinal nerves: • Afferent (sensory) only • Pseuodounipolar (unipolar) neurons • Cell body in a spinal sensory (posterior root) ganglion • Single process divides into: • peripheral process -- extends to sensory nerve terminal • central process -- enters CNS ALL SENSORY FIBERS WHICH ARE EVER PART OF A SPINAL NERVE HAVE THEIR CELL BODIES LOCATED IN THE SPINAL SENSORY (POSTERIOR ROOT) GANGLIA OF SPINAL NERVES B. Anterior roots of spinal nerves: • Efferent efferent (motor) only • bi- (multi-) polar neurons • cell has a receiving end(s) = dendrite(s) • cell has a sending end = axon • cell body lies within CNS The posterior and anterior roots are the only site where the functional components (afferent and efferent fibers) of spinal nerves are separable.  Almost as soon as the roots unite to form the (mixed: motor and sensory) spinal nerve, it divides into two major branches (rami): (1) posterior (primary) ramus (2) anterior (primary) ramus NOTE: the posterior and anterior rami are parietal in distribution. They serve the neck, body wall and limbs and the skin thereon including that of the back of the head; except for “communicating branches” which connect the initial part of the anterior rami with the sympathetic trunks, the posterior and anterior rami do not distribute to the viscera of the body cavities and head or to the face. A. Posterior (Primary) Ramus (GA110 Fig. 1.1820; Netter Plates 156A, 166, 241)163A; 173, 250) turn sharply posteriorly around the vertebral column, soon to divide into: o a lateral branch and 6
  • 7. o a medial branch.  Both supply the longitudinal deep (“true”) muscles of the back (vs. the ‘superficial muscles of the back’—actually muscles of the upper limb—supplied by anterior rami)  only one of the two branches will continue to become cutaneous, supplying the skin overlying the deep muscles of the back. • for upper 6 or 7 thoracic spinal nerves, the medial branch becomes cutaneous; (GA110 Fig. 64.29; Netter Plate 163170) • in the lower 5 or 6 thoracic and in the lumbar nerves, the lateral branch becomes cutaneous. • posterior rami of all spinal nerves are essentially similar • remain separate from each other for the most part (i.e., they do not enter plexus formation, retaining separate connections to their “segmental distribution”). B. Anterior (Primary) Ramus (GA110 Fig. 1.1820; Netter Plates 166, 241173, 250) • course around the body wall to supply the anterolateral skin and muscles of the neck and trunk and the skin and muscles of the limbs. • distribution of anterior rami of most spinal nerves is not as straight forward as that of the posterior rami, which remain separate. o Most anterior rami merge and interchange of fibers with adjacent anterior rami, forming plexuses in which identities of contributing nerves are lost. Thus, most anterior rami contribute to peripheral nerves which have pleurisegmental distributions. o The anterior rami of most thoracic nerves, however, remain separate (unisegmental) and can usually be traced by dissection to the muscles and skin that each innervates. Because of the simplicity of their anterior rami, the thoracic nerves are considered by convention to represent “typical” spinal nerves (although, because of their minority status, the label “simple” spinal nerves would seem more appropriate). 7
  • 8. C. Branches of the Anterior Rami of Thoracic Nerves • lateral (cutaneous) br. of the anterior (primary) ramus o becomes cutaneous in anterior axillary line o divides into anterior and posterior divisions • anterior (cutaneous) br. of the anterior (primary) ramus o actually becomes cutaneous in parasternal line o divides into lateral (major) and medial branches Superficial Muscles of the Back The skeletal system consists of two main parts (COA4, p. 15): 1. axial skeleton: bones of head, neck and trunk 2. appendicular skeleton: bones of limbs The superficial back muscles [see Tables 6.2 (COA4, p. 691) or 6.4 (GA11, p. 496) for details]: • extend primarily between thoracic parts of the axial skeleton (thoracic vertebrae and ribs, but also skull, cervical and lumbar vertebrae) and the superior appendicular skeleton (skeleton of the upper limb, including the pectoral girdle). • produce multiple movements at the physiological “scapulothoracic joint” • Superficial posterior thoracoappendicular (extrinsic shoulder) muscles: 1. Trapezius a. trapezoid or diamond shaped b. three functional parts: descending (superior), middle, and ascending (inferior) c. atypical limb muscle innervation (a cranial nerve—Accessory, or CN XI) 2. Latissimus dorsi: a. sheet-like, fan-shaped “climber’s/rower’s muscle” b. aponeurotic (flat tendinous) origin from spinous processes (and iliac crests— actually part of the inferior appendicular skeleton) via thoracolumbar fascia • Deep posterior thoracoappendicular (extrinsic shoulder) muscles: 8
  • 9. 3. Rhomboid major and minor • Separation between them not always distinct • minor = narrow and thick; major = wide and flat • attach to medial border of scapular, at & inferior to level of scapular spine 4. Levator scapulae • attaches to medial border of scapular, superior to level of scapular spine Muscles 2 - 4 above have “typical” limb muscle innervation (derived from the anterior rami of spinal nerves). Neurovascular structures serving trapezius pass superficial to 3 & 4, while those supplying 3 & 4 passes deep to them. 9
  • 10. 3. Rhomboid major and minor • Separation between them not always distinct • minor = narrow and thick; major = wide and flat • attach to medial border of scapular, at & inferior to level of scapular spine 4. Levator scapulae • attaches to medial border of scapular, superior to level of scapular spine Muscles 2 - 4 above have “typical” limb muscle innervation (derived from the anterior rami of spinal nerves). Neurovascular structures serving trapezius pass superficial to 3 & 4, while those supplying 3 & 4 passes deep to them. 9

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