Activity #8:

Spinal Cord, Spinal Nerves,

& Sensory Organs

Chapters 16 & 19 – McKinley et al., Human Anatomy, 4e.

Objectives:

• Identify structures in the gross anatomy of the spinal cord on both models and cadavers or wet specimens.

• Identify structures in the cross section of the spinal cord on classroom models.

• Identify the nerve plexuses and specific nerves from each.

• Identify structures from the human eye on models.

• Dissect a cow eye and identify the structures listed.

• Identify structures of the ear on classroom models.

• Histology: Observe and identify structures in a histology slide of the cochlea.

1Compilation: Lisa Radmall

Spinal Cord: Gross Anatomy

2

• Cervical enlargement

• Thoracic region

• Lumbar enlargement

• Conus medullaris

• Cauda equina

• Filum terminale

• Spinal Nerves

• Cervical (C1-C8)

• Thoracic (T1-T12)

• Lumbar (L1-L5)

• Sacral (S1-S5)

• Coccygeal (Co1)

• Denticulate Ligaments

Fig. 16.1

Spinal Cord: Cross Section

3

Spinal Cord: Cross Section

4

Spinal Cord: Meninges & Spaces

5Fig. 16.2a

Spinal Cord: Meninges & Spaces

6

Subdural space

Arachnoid mater

Spinal Nerves: Plexuses

7

• All ventral rami except T2-T12 form interlacing nerve networks called plexuses.

• Major nerve plexuses are found in the cervical, brachial, lumbar, and sacral regions of the spinal cord.

• Each resulting branch of a plexus contains fibers from several spinal nerves.

• Thoracic spinal nerves T2-T12 do not form a plexus; branch to intercostal nerves.

• You will be responsible to know the listed nerves and (only) the muscles they innervate from your muscle anatomy labs.

Spinal Nerves: Cervical Plexus

8Fig. 16.8

Phrenic Nerve – Innervation of Diaphragm

9

Spinal Nerves: Brachial Plexus

10Fig. 16.9a

Spinal Nerves: Brachial Plexus

11

• Axillary nerve

• Median nerve (center of “M”)

• Musculotaneous nerve (lateral on “M”)

• Radial nerve

• Ulnar nerve (medial on “M”)

• Long thoracic nerve

• Medial pectoral nerve

• Lateral pectoral nerve

Fig. 16.9c

Brachial Plexus – Axillary Nerve

12

• Axillary nerve

• Innervation

• Deltoid

• Teres minor

Table 16.4

Brachial Plexus – Median Nerve

13

• Median nerve (center of “M”)

• Innervation: Anterior forearm muscles

• Pronator teres

• Flexor capri radialis

• Palmaris longus

• Flexor digitorum superficialis

• Flexor digitorum profundus

• Flexor pollicis longus

Table 16.4

Brachial Plexus – Musculocutaneous Nerve

14

• Musculotaneous nerve (lateral on “M”)

• Innervation

• Biceps brachii (both heads)

• Brachialis

Table 16.4

Brachial Plexus – Radial Nerve

15

• Radial nerve

• Innervation: Posterior arm muscles

• Triceps brachii (3 heads)

• Innervation: Posterior forearm muscles

• Brachioradialis

• Supinator

• Extensor carpi radialis

• Extensor carpi ulnaris

• Extensor digitorum

• Extensor pollicis longus

• Extensor pollicis brevis

• Abductor pollicis longus

Table 16.4

Brachial Plexus – Ulnar Nerve

16

• Ulnar nerve (medial on “M”)

• Innervation

• Flexor carpi ulnaris

• Flexor digitorum profundus

• Most hand muscles

Table 16.4

Brachial Plexus – Long Thoracic Nerve

17

• Long thoracic nerve

• Innervation

• serratus anterior

Brachial Plexus – Pectoral Nerves

18

• Medial pectoral nerve

• Innervation

• Pectoralis Major

• Pectoralis Minor

• Lateral pectoral nerve

• Innervation

• Pectoralis Major

Spinal Nerves: Intercostal Nerves

19

• Intercostal Nerves

• Branch from spinal nerves

• Do NOT form a plexus

• Innervation: intercostal muscles

Fig. 16.7

Spinal Nerves: Lumbar Plexus

20Fig. 16.10

Lumbar Plexus – Femoral Nerve

21

• Femoral nerve

• Innervation: Anterior thigh

muscles

• Illiacus

• Psoas major

• Pectineus

• Sartorius

• Rectus femoris

• Vastus lateralis

• Vastus medialis

• Vastus intermedius

Table 16.5

Lumbar Plexus – Obturator Nerve

22

• Obturator nerve

• Innervation: Medial thigh muscles

• Gracilis

• Adductor longus

• Adductor brevis

• Adductor magnus

• Pectineus

Table 16.5

Spinal Nerves: Sacral Plexus

23Fig. 16.11

Sacral Plexus – Gluteal Nerves

24

• Inferior gluteal nerve

• Innervation

• Gluteus maximus

• Superior gluteal nerve

• Innervation

• Tensor fasciae latae

• Gluteus medius

• Gluteus minimus

Sacral Plexus – Tibial Nerve

25

Sciatic nerve

(branches into tibial and common fibular nerve)

• Tibial nerve

• Innervation: Posterior thigh & leg

muscles

• Biceps femoris long head

• Semitendinosus

• Semimembranosus

• Adductor magnus

• Gastrocnemius

• Soleus

• Popliteus

• Flexor digitorum longus

• Flexor hallicus longus

• Plantar surface of footTable 16.6

Sacral Plexus – Common Fibular Nerve

26

• Common fibular nerve

• Innervation: Biceps femoris (short head)

• Branches into deep and superficial fibular nerve

• Deep fibular nerve

• Innervation: Dorsal surface of foot

• Innervation: Anterior leg muscles

• Tibialis anterior

• Extensor digitorum longus

• Extensor hallicus longus

• Superficial fibular nerve

• Innervation: Lateral compartment

• Fibularis longus

• Fibularis brevis

Table 16.6

27

Extrinsic Eye Muscles - Lateral view

Orbital

fat pad

Palpebra

(eyelid)

28

Extrinsic Eye Muscles - Medial view

Extrinsic Eye Muscles – Innervation & Movement

29

The six (6) extrinsic eye muscles, innervation, and movement of the eye:

1. Inferior Oblique

• (CNIII) elevates and turns eye laterally

2. Inferior Rectus

• (CNIII) pulls eye inferiorly

3. Superior Rectus

• (CNIII) pulls eye superiorly

4. Medial Rectus

• (CNIII) pulls eye medially

5. Lateral Rectus

• (CNVI) pulls eye laterally

6. Superior Oblique

• (CNIV) depresses and turns eye laterally

Accessory Structures of the Eye

30Fig. 19.10

Layers of the Eye Wall

31

• Conjunctiva

• Surrounds most of eye, covers sclera

• Fibrous Tunic (outermost layer)

• Anterior cornea – Transparent and avascular. Nourished by lacrimal fluid.

• Posterior sclera – “White” of eye. Gives shape and protection to eye.

• Vascular Tunic (middle layer)

• Choroid – Capillary network. Supplies nutrients and oxygen to retina.

• Ciliary body & muscles – Smooth muscle & epithelium affect tension on

suspensory ligaments, altering shape of lens.

• Iris – Color of eye. Smooth muscle, controls pupil size & diameter.

• Neural Tunic (innermost layer)

• Retina – Pigmented layer provides vitamin A for photoreceptor cells in

Neural layer.

Layers of the Eye Wall

32

Structures of the Eye

33

Ora serrata

Cavities of the Eye

34Fig. 19.16

Cow Eye: External & Internal Anatomy

35

Sensory Organ: The Ear

36

The ear is composed of three regions: the external ear, located mostly on

the outside of the head, and the middle and inner ear, which are housed

within the petrous portion of the temporal bone

Sensory Organ: The Ear

37Fig. 19.19

Structure of the Middle Ear

38Fig. 19.20

Structure of the Inner Ear

39Fig. 19.21

Structure of the Cochlea and Spiral Organ

40Fig. 19.26

Histology of Cochlea

41

Sensory Organ: The Ear

42Fig. 19.19

Auditory Transduction

43

Image References

44

3- studyblue.com

5-www.slccanatomy.com

6-

9- studyblue.com

17-

18-

24- https://web.duke.edu/anatomy/Lab13-15/lab13images/lab13-step4a.jpg

27-30- http://medical-transcriptionist-reference.blogspot.com/2012/05/eye-muscles.html

https://droualb.faculty.mjc.edu

33- google

43- https://www.youtube.com/watch?v=PeTriGTENoc

Accessory Structures of the Eye

45

Lacrimal caruncle

Nasolacrimal duct

Palpebra

(eyelid)