Meninges of the Spinal Cord

The spinal cord and brain are enclosed in three fibrous membranes called meninges (meh-NIN-jeez)—singular, meninx2 (MEN-inks). These membranes separate the soft tissue of the central nervous system from the bones of the vertebrae and skull. From superficial to deep, they are the dura mater, arachnoid mater, and pia mater.

2menin = membrane

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

13. The Spinal Cord, Spinal Nerves, and Somatic Reflexes

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Chapter 13 The Spinal Cord, Spinal Nerves, and Somatic Reflexes 483

Cervical enlargement

Lumbar-enlargement

Medullary -cone

Cauda equina -

Coccygeal -ligament n

Cervical spinal nerves

Dura mater-

and arachnoid mater

Thoracic spinal nerves

Lumbar spinal nerves

Sacral spinal nerves

Figure 1S.1 The Spinal Cord, Dorsal Aspect.

The dura mater3 (DOO-ruh MAH-tur) forms a loose-fitting sleeve called the dural sheath around the spinal cord. It is a tough collagenous membrane with a thickness and texture similar to a rubber kitchen glove. The space between the sheath and vertebral bone, called the epidural space, is occupied by blood vessels, adipose tissue, and loose connective tissue (fig. 13.2a). Anesthetics are sometimes introduced to this space to block pain signals during childbirth or surgery; this procedure is called epidural anesthesia.

The arachnoid4 (ah-RACK-noyd) mater adheres to the dural sheath. It consists of a simple squamous epithelium, the arachnoid membrane, adhering to the inside of the dura, and a loose mesh of collagenous and elastic fibers spanning the gap between the arachnoid membrane and the pia mater. This gap, called the subarachnoid space, is filled with cere-brospinal fluid (CSF), a clear liquid discussed in chapter 14.

The pia5 (PEE-uh) mater is a delicate, translucent membrane that closely follows the contours of the spinal cord. It continues beyond the medullary cone as a fibrous

4arachn = spider, spider web + oid = resembling spia = tender, soft

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

Form and Function, Third Reflexes Edition

484 Part Three Integration and Control

Denticulate Ligament

Fat in epidural space Dural sheath Arachnoid mater

Subarachnoid space

Spinal cord Denticulate ligament

Spinal nerve

Pia mater Bone of vertebra

Posterior median sulcus Dorsal horn Gray commissure

Lateral column

Lateral horn Ventral horn Anterior median fissure

Epidural Space Anatomy

Spinal nerve

Ventral root of spinal nerve

Ventral column

Figure 13.2 Cross Section of the Thoracic Spinal Cord. (a) Relationship to the vertebra, meninges, and spinal nerve. (b) Anatomy of the spinal cord itself.

Lateral horn Ventral horn Anterior median fissure

Central canal Dorsal column

Dorsal root of spinal nerve

Dorsal root ganglion

Spinal nerve

Ventral root of spinal nerve

Ventral column

Figure 13.2 Cross Section of the Thoracic Spinal Cord. (a) Relationship to the vertebra, meninges, and spinal nerve. (b) Anatomy of the spinal cord itself.

strand, the terminal filum, forming part of the coccygeal ligament that anchors the cord to vertebra L2. At regular intervals along the cord, extensions of the pia called denticulate ligaments extend through the arachnoid to the dura, anchoring the cord and preventing side-to-side movements.

Insight 13.1 Clinical Application

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