Copyright © 2010 Pearson Education, Inc. Marieb Chapter 13: Part B

Copyright © 2010 Pearson Education, Inc. Cranial Nerves Twelve pairs of nerves associated with the brain Most are mixed in function; two pairs are purely sensory Each nerve is identified by a number (I through XII) and a name “On occasion, our trusty truck acts funny—very good vehicle anyhow”

Copyright © 2010 Pearson Education, Inc. Figure 13.6 Cervical nerves C 1 – C 8 Thoracic nerves T 1 – T 12 Lumbar nerves L 1 – L 5 Sacral nerves S 1 – S 5 Coccygeal nerve Co 1 Cervical plexus Intercostal nerves Cervical enlargement Lumbar enlargement Cauda equina Brachial plexus Lumbar plexus Sacral plexus Spinal Nerves

Copyright © 2010 Pearson Education, Inc. Spinal Nerves: Roots Each spinal nerve connects to the spinal cord via two roots Ventral root Motor fibers from the ventral horn motor neurons to skeletal muscles Dorsal root Sensory fibers

Copyright © 2010 Pearson Education, Inc. Spinal Nerves: Rami All ventral rami except T 2 –T 12 form plexuses (cervical, brachial, lumbar, and sacral) The back is innervated by dorsal rami via several branches Ventral rami of T 2 –T 12 form intercostal nerves; supply muscles of the ribs and abdominal wall

Copyright © 2010 Pearson Education, Inc. Figure 13.7 (b) Dorsal ramus Ventral ramus Intercostal nerve Spinal nerve Rami communicantes Dorsal root ganglion Dorsal root Ventral root Sympathetic trunk ganglion Sternum (b) Cross section of thorax showing the main roots and branches of a spinal nerve. Branches of intercostal nerve Lateral cutaneous Anterior cutaneous No Plexuses Here!

Copyright © 2010 Pearson Education, Inc. What is a Plexus?

Copyright © 2010 Pearson Education, Inc. Why Do Plexuses Exist?

Copyright © 2010 Pearson Education, Inc. Cervical Plexus Formed by ventral rami of C 1 –C 4 Innervates skin and muscles of the neck, ear, back of head, and shoulders Major motor and sensory nerve of the diaphragm (receives fibers from C 3 –C 5 )

Copyright © 2010 Pearson Education, Inc. Figure 13.8 Hypoglossal nerve (XII) C1C1 C2C2 C3C3 C4C4 C5C5 Segmental branches Lesser occipital nerve Greater auricular nerve Ansa cervicalis Phrenic nerve Supraclavicular nerves Accessory nerve (XI) Transverse cervical nerve Ventral rami: Ventral rami

Copyright © 2010 Pearson Education, Inc. Brachial Plexus Formed by ventral rami of C 5 –C 8 and T 1 (and often C 4 and T 2 ) It gives rise to the nerves that innervate the upper limb

Copyright © 2010 Pearson Education, Inc. Figure 13.9 (a) Upper Middle Trunks Lower Roots (ventral rami): Upper subscapular Lower subscapular Thoracodorsal Medial cutaneous nerves of the arm and forearm Long thoracic Medial pectoral Lateral pectoral Nerve to subclavius Suprascapular Dorsal scapular Posterior divisions Anterior divisions Lateral Posterior Cords Medial Axillary Musculo- cutaneous Radial Median Ulnar Posterior divisions Trunks Roots C4C4 C5C5 C6C6 C7C7 C8C8 T1T1 (a) Roots (rami C 5 – T 1 ), trunks, divisions, and cords

Copyright © 2010 Pearson Education, Inc. Figure 13.9 (d) Anterior divisions (d) Flowchart summarizing relationships within the brachial plexus Major terminal branches (peripheral nerves) CordsDivisionsTrunks Roots (ventral rami) Musculocutaneous Median Ulnar Radial Axillary Anterior Posterior Anterior Posterior Anterior Upper Middle Lower Lateral Medial Posterior divisions TrunksRoots C5C5 C6C6 C7C7 C8C8 T1T1

Copyright © 2010 Pearson Education, Inc. Brachial Plexus: Nerves Musculocutaneous—innervates the biceps brachii and brachialis and skin of lateral forearm Median—innervates the skin, most flexors and pronators in the forearm, and some intrinsic muscles of the hand Ulnar—supplies the flexor carpi ulnaris, part of the flexor digitorum profundus, most intrinsic muscles of the hand, and skin of medial aspect of hand Radial—innervates essentially all extensor muscles, supinators, and posterior skin of limb

Copyright © 2010 Pearson Education, Inc. Figure 13.9 (c) Median nerve Musculocutaneous nerve Radial nerve Humerus Ulna Ulnar nerve Median nerve Radius Radial nerve (superficial branch) Superficial branch of ulnar nerve Dorsal branch of ulnar nerve Digital branch of ulnar nerve Muscular branch Digital branch (c) The major nerves of the upper limb Axillary nerve Anterior divisions Posterior divisions TrunksRoots

Copyright © 2010 Pearson Education, Inc. Lumbar Plexus Arises from L 1 –L 4 Innervates the thigh, abdominal wall, and psoas muscle Femoral nerve—innervates quadriceps and skin of anterior thigh and medial surface of leg

Copyright © 2010 Pearson Education, Inc. Figure (a) Ventral rami and major branches of the lumbar plexus Iliohypogastric L1L1 L2L2 L3L3 L4L4 L5L5 Ilioinguinal Genitofemoral Lateral femoral cutaneous Obturator Femoral Lumbosacral trunk Lateral femoral cutaneous Anterior femoral cutaneous Saphenous Obturator Iliohypogastric Ilioinguinal Femoral Ventral rami Ventral rami: (b) Distribution of the major nerves from the lumbar plexus to the lower limb

Copyright © 2010 Pearson Education, Inc. Sacral Plexus Arises from L 4 –S 4 Serves the buttock, lower limb, pelvic structures, and perineum Sciatic nerve Longest and thickest nerve of the body Innervates the hamstring muscles, adductor magnus, and most muscles in the leg and foot Composed of two nerves: tibial and common fibular

Copyright © 2010 Pearson Education, Inc. Figure (a) Superior gluteal Lumbosacral trunk Inferior gluteal Common fibular Tibial Posterior femoral cutaneous Pudendal Sciatic Ventral rami and major branches of the sacral plexus L4L4 L5L5 S1S1 S2S2 S3S3 S4S4 S5S5 Co 1 Ventral rami Ventral rami:

Copyright © 2010 Pearson Education, Inc. Figure (b) Superior gluteal Inferior gluteal Common fibular Deep fibular Superficial fibular Plantar branches Tibial Sural (cut) Posterior femoral cutaneous Pudendal Sciatic (b) Distribution of the major nerves from the sacral plexus to the lower limb

Copyright © 2010 Pearson Education, Inc. Innervation of Skin Dermatome: the area of skin innervated by the cutaneous branches of a single spinal nerve All spinal nerves except C 1 participate in dermatomes Most dermatomes overlap, so destruction of a single spinal nerve will not cause complete numbness

Copyright © 2010 Pearson Education, Inc. Figure C2 C3 C4 C5 T1 T2 T3 T4 T5 C6 C8 C7 C6 T6 T7 T8 T9 T10 T11 T12 L1 S2 S3 L1 L2 L3 L4 L5 L2 L3 L4 L5 S1 C5 C6 C8 T2 C5 C6 S1 Anterior view C2 C3 C4 C5 C6 C7 C8 C7 T1 T2 T3 T4 T5 T6 T7 T8 T9 T10 T11 T12 L1 L2 L3 S1 (b) Posterior view L5 S2 S1 S3 S2S1S2 S4 S5 L5 L4 L5 L4 C6 C5 L4 L3 L2 L1 L4