Cranail Iliohypogastric T13

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Roots

Shoulder Dislocation Phrenic Nerve

Anterior root Posterior root

Supraclavicular nerve

Branch to brachial plexus Phrenic nerve

Brachial Plexus And Phrenic Nerve
Segmental branch Hypoglossal nerve (XII) Lesser occipital nerve Great auricular nerve Transverse cervical nerve

Anterior root Posterior root

Ansa cervicalis

Supraclavicular nerve

Branch to brachial plexus Phrenic nerve

Figure 13.14 The Cervical Plexus.

Aphren = diaphragm

Saladin: Anatomy & I 13. The Spinal Cord, Spinal I Text I © The McGraw-Hill

Physiology: The Unity of Nerves, and Somatic Companies, 2003

Form and Function, Third Reflexes Edition

498 Part Three Integration and Control

Table 13.4 The Brachial Plexus

The brachial plexus (figs. 13.15 and 13.16) is formed by the ventral rami of nerves C4 to T2. It passes over the first rib into the axilla and innervates the upper limb and some muscles of the neck and shoulder. It gives rise to nerves for cutaneous sensation, muscle contraction, and proprioception from the joints and muscles.

The subdivisions of this plexus are called roots, trunks, divisions, and cords (color-coded in figure 13.15). The five roots are the ventral rami of nerves C5 to T1, which provide most of the fibers to this plexus (C4 and T2 contribute partially). The five roots unite to form the upper, middle, and lower trunks. Each trunk divides into an anterior and posterior division, and finally the six divisions merge to form three large fiber bundles—the posterior, medial, and lateral cords.

Axillary Nerve

Composition: Motor and somatosensory

Origin: Posterior cord of brachial plexus

Sensory innervation: Skin of lateral shoulder and arm; shoulder joint

Motor innervation: Deltoid and teres minor

Radial Nerve

Composition: Motor and somatosensory Origin: Posterior cord of brachial plexus

Sensory innervation: Skin of posterior aspect of arm, forearm, and wrist; joints of elbow, wrist, and hand Motor innervation: Muscles of posterior arm and forearm: triceps brachii, supinator, anconeus, brachioradialis, extensor carpi radialis brevis, extensor carpi radialis longus, and extensor carpi ulnaris

Trunks

□ Anterior divisions

□ Posterior divisions

C5 flv I

C5 flv I

Elbow Joint Innervation

Medial cord

Figure 13.15 The Brachial Plexus.

Dorsal Scapular Nerve

Medial cord

Dorsal scapular nerve Long thoracic nerve Suprascapular nerve Subclavian nerve Posterior cord Axillary nerve Subscapular nerve Thoracodorsal nerve Radial nerve Lateral cord

Musculocutaneous nerve Medial and lateral pectoral nerves Median nerve Ulnar nerve

Medial cutaneous antebrachial nerve Medial brachial cutaneous nerve

Lateral Antebrachial Cutaneous

Clavicle Lateral cord Posterior cord Medial cord Axillary nerve Scapula

Musculocutaneous nerve

Median nerve Humerus Radial nerve Ulna

Ulnar nerve

Median nerve

Radial nerve Radius

Superficial branch of ulnar nerve

Digital branch of median nerve

Digital branch of ulnar nerve

Figure 13.15 The Brachial Plexus.

Saladin: Anatomy & I 13. The Spinal Cord, Spinal I Text

Physiology: The Unity of Nerves, and Somatic

Form and Function, Third Reflexes Edition

Chapter 13 The Spinal Cord, Spinal Nerves, and Somatic Reflexes 499

Chapter 13 The Spinal Cord, Spinal Nerves, and Somatic Reflexes 499

Musculocutaneous Nerve

Composition: Motor and somatosensory

Origin: Lateral cord of brachial plexus

Sensory innervation: Skin of lateral aspect of forearm

Motor innervation: Muscles of anterior arm: coracobrachial, biceps brachii, and brachialis Median Nerve

Composition: Motor and somatosensory Origin: Medial cord of brachial plexus

Sensory innervation: Skin of lateral two-thirds of hand, joints of hand

Motor innervation: Flexors of anterior forearm; thenar muscles; first and second lumbricals

Ulnar Nerve

Composition: Motor and somatosensory

Origin: Medial cord of brachial plexus

Sensory innervation: Skin of medial part of hand; joints of hand

Motor innervation: Flexor carpi ulnaris, flexor digitorum profundus, adductor pollicis, hypothenar muscles, interosseous muscles, and third and fourth lumbricals

Figure 13.16 Photograph of the Brachial Plexus. Anterior view of the right shoulder, also showing three of the cranial nerves, the sympathetic trunk, and the phrenic nerve (a branch of the cervical plexus). Most of the other structures resembling nerves in this photograph are blood vessels. (a. = artery; m. = muscle; n. = nerve.)

Phrenic Nerve Innervation

Figure 13.16 Photograph of the Brachial Plexus. Anterior view of the right shoulder, also showing three of the cranial nerves, the sympathetic trunk, and the phrenic nerve (a branch of the cervical plexus). Most of the other structures resembling nerves in this photograph are blood vessels. (a. = artery; m. = muscle; n. = nerve.)

Saladin: Anatomy & Physiology: The Unity of Form and Function, Third Edition

Table 13.5 The Lumbar Plexus

The lumbar plexus (fig. 13.17) is formed from the ventral rami of nerves L1 to L4 and some fibers from T12. With only five roots and two divisions, it is less complex than the brachial plexus.

Iliohypogastric Nerve

Femoral Nerve

Composition: Motor and somatosensory Sensory innervation: Skin of anterior abdominal wall Motor innervation: Internal and external obliques and transversus abdominis

Ilioinguinal Nerve

Composition: Motor and somatosensory

Sensory innervation: Skin of anterior and lateral thigh; medial leg and foot Motor innervation: Anterior muscles of thigh and extensors of leg; iliacus, psoas major, pectineus, quadriceps femoris, and sartorius

Saphenous (sah-FEE-nus) Nerve

Composition: Motor and somatosensory

Sensory innervation: Skin of upper medial thigh; male scrotum and root of penis; female labia majora Motor innervation: Joins iliohypogastric nerve and innervates the same muscles

Genitofemoral Nerve

Composition: Somatosensory

Sensory innervation: Skin of medial aspect of leg and foot; knee joint

Obturator Nerve

Composition: Somatosensory

Sensory innervation: Skin of middle anterior thigh; male scrotum and cremaster muscle; female labia majora

Lateral Femoral Cutaneous Nerve

Composition: Motor and somatosensory

Sensory innervation: Skin of superior medial thigh; hip and knee joints Motor innervation: Adductor muscles of leg: external obturator, pectineus, adductor longus, adductor brevis, adductor magnus, and gracilis

Composition: Somatosensory

Sensory innervation: Skin of lateral aspect of thigh

U Roots

U Anterior divisions U Posterior divisions

U Anterior divisions U Posterior divisions

Cremaster Muscle Knee

Figure 13.17 The Lumbar Plexus.

Anterior view

Iliohypogastric nerve Ilioinguinal nerve Genitofemoral nerve Lateral femoral cutaneous nerve Femoral nerve

Saphenous nerve Obturator nerve Lumbosacral trunk

I I From lumbar plexus From sacral plexus

Os coxae Sacrum Femoral nerve - Pudendal nerve Sciatic nerve Femur

Tibial nerve Common fibular nerve

Superficial fibular nerve

Deep fibular nerve

Fibula

Tibia

Tibial nerve

Medial plantar nerve Lateral plantar nerve

Posterior view

Figure 13.17 The Lumbar Plexus.

I I From lumbar plexus From sacral plexus

Os coxae Sacrum Femoral nerve - Pudendal nerve Sciatic nerve Femur

Posterior view

Saladin: Anatomy & I 13. The Spinal Cord, Spinal I Text I © The McGraw-Hill

Physiology: The Unity of Nerves, and Somatic Companies, 2003

Form and Function, Third Reflexes Edition

Chapter 13 The Spinal Cord, Spinal Nerves, and Somatic Reflexes 501

Table 13.6 The Sacral and Coccygeal Plexuses

The sacral plexus is formed from the ventral rami of nerves L4, L5, and S1 to S4. It has six roots and anterior and posterior divisions. Since it is connected to the lumbar plexus by fibers that run through the lumbosacral trunk, the two plexuses are sometimes referred to collectively as the lumbosacral plexus. The coccygeal plexus is a tiny plexus formed from the ventral rami of S4, S5, and Co (fig. 13.18).

The tibial and common fibular nerves listed in this table travel together through a connective tissue sheath; they are referred to collectively as the sciatic (sy-AT-ic) nerve. The sciatic nerve passes through the greater sciatic notch of the pelvis, extends for the length of the thigh, and ends at the popliteal fossa. Here, the tibial and common fibular nerves diverge and follow their separate paths into the leg. The sciatic nerve is a common focus of injury and pain.

Superior Gluteal Nerve

Composition: Motor

Motor innervation: Gluteus minimus, gluteus medius, and tensor fasciae latae

Inferior Gluteal Nerve

Composition: Motor

Motor innervation: Gluteus maximus

Nerve to Piriformis

Composition: Motor Motor innervation: Piriformis

Nerve to Quadratus Femoris

Composition: Motor and somatosensory Sensory innervation: Hip joint

Motor innervation: Quadratus femoris and gemellus inferior

Nerve to Internal Obturator

Composition: Motor

Motor innervation: Internal obturator and gemellus superior

Perforating Cutaneous Nerve

Composition: Somatosensory

Sensory innervation: Skin of posterior aspect of buttock

Posterior Cutaneous Nerve

Composition: Somatosensory

Sensory innervation: Skin of lower lateral buttock, anal region, upper posterior thigh, upper calf, scrotum, and labia majora Tibial Nerve

Composition: Motor and somatosensory

Sensory innervation: Skin of posterior leg and sole of foot; knee and foot joints

Motor innervation: Semitendinosus, semimembranosus, long head of biceps femoris, gastrocnemius, soleus, flexor digitorum longus, flexor hallucis longus, tibialis posterior, popliteus, and intrinsic muscles of foot

Saladin: Anatomy & I 13. The Spinal Cord, Spinal I Text I © The McGraw-Hill

Physiology: The Unity of Nerves, and Somatic Companies, 2003

Form and Function, Third Reflexes Edition

502 Part Three Integration and Control

Table 13.6 The Sacral and Coccygeal Plexuses (continued)

Common Fibular (peroneal) Nerve

Composition: Motor and somatosensory

Sensory innervation: Skin of anterior distal one-third of leg, dorsum of foot, and toes I and II; knee joint

Motor innervation: Short head of biceps femoris, fibularis tertius, fibularis brevis, fibularis longus, tibialis anterior, extensor hallucis longus, extensor digitorum longus, and extensor digitorum brevis

Pudendal Nerve

Composition: Motor and somatosensory

Sensory innervation: Skin of penis and scrotum of male; clitoris, labia majora and minora, and lower vagina of female Motor innervation: Muscles of perineum

Coccygeal Nerve

Composition: Motor and somatosensory Sensory innervation: Skin over coccyx Motor innervation: Muscles of pelvic floor

Posterior divisions fiif

Inferior gluteal nerve

S4

v

Ï1

S5

A

Co1

Common fibular nerve

-Tibial nerve

Common fibular nerve

-Tibial nerve

Sciatic nerve

'ij__—i--Posterior cutaneous femoral nerve

'-Internal pudendal nerve

Figure 13.18 The Sacral and Coccygeal Plexuses.

Saladin: Anatomy & I 13. The Spinal Cord, Spinal I Text I © The McGraw-Hill

Physiology: The Unity of Nerves, and Somatic Companies, 2003

Form and Function, Third Reflexes Edition

Chapter 13 The Spinal Cord, Spinal Nerves, and Somatic Reflexes 503

Cutaneous Innervation and Dermatomes

Each spinal nerve except C1 receives sensory input from a specific area of skin called a dermatome.22 A dermatome map (fig. 13.19) is a diagram of the cutaneous regions innervated by each spinal nerve. Such a map is oversimplified, however, because the dermatomes overlap at their edges by as much as 50%. Therefore, severance of one sensory nerve root does not entirely deaden sensation from a dermatome. It is necessary to sever or anesthetize three successive spinal nerves to produce a total loss of sensation from one dermatome. Spinal nerve damage is assessed by testing the dermatomes with pinpricks and noting areas in which the patient has no sensation.

22derma = skin + tome = segment, part

Before You Go On

Answer the following questions to test your understanding of the preceding section:

5. What is meant by the dorsal and ventral roots of a spinal nerve? Which of these is sensory and which is motor?

6. Where are the somas of the dorsal root located? Where are the somas of the ventral root?

7. List the five plexuses of spinal nerves and state where each one is located.

8. State which plexus gives rise to each of the following nerves: axillary, ilioinguinal, obturator, phrenic, pudendal, radial, and sciatic.

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Responses

  • joona
    Where is the antebrachial located?
    9 years ago

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