Chapter 11, Section 1

Meninges and Ventricles

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introduction

A nucleus (sing. nucleus) refers to a group of cell bodies within the CNS

e.g. dentate nucleus

A tract is a group of axons within the CNSe.g. corticospinal tract

A ganglion is a group of cell bodies within the PNSe.g. dorsal root ganglion

A nerve is a group of axons, along with their protective sheaths in the PNS

e.g. sciatic nerve

The central nervous system (CNS) consists of the brain and spinal cord

The peripheral nervous system (PNS) consists of cranial and spinal nerves

meningesThe meninges is a three-layered membrane that surrounds the brain and spinal cord.

1. Dura Mater “tough mother”• Tough outer layer of meninges• Dense connective tissue with many blood vessels and nerves• Forms dural sinuses that drain venous blood from the brain.

2. Arachnoid Mater “spider-web like”• Subarachnoid space

• Space between arachnoid and pia mater filled with Cerebral Spinal Fluid (CSF)

3. Pia Mater “gentle mother”• Thin membrane with many nerves and blood vessels• Membrane is attached to surface of brain and spinal cord.

Figure 11.1 Meninges (a) membranes called meninges enclose the brain and spinal cord. (b) the meninges include three layers: dura mater, arachnoid mater, and pia mater. Note the dural sinus formed by the dura mater.

Figure 11.1 Meninges (a) membranes called meninges enclose the brain and spinal cord. (b) the meninges include three layers: dura mater, arachnoid mater, and pia mater. Note the dural sinus formed by the dura mater.

Figure 11.2 Meninges of the spinal cord.

(a)three layers of the meninges . (b)a small space (epidural space) fills the space between

the dura mater and the vertebra.

VENTRICLES

Interconnected cavities, called ventricles lie within the cerebral hemispheres and the brainstem.

Ventricles are continuous with the central canal of the spinal cord and are filled with Cerebrospinal Fluid (CSF).

4 Ventricles:2 Lateral ventricles

1st ventricle is in left cerebral hemisphere2nd ventricle is in the right cerebral hemisphere Lateral ventricles are connected by interventricular foramina.

Third ventricleSurrounds the diencephalonCerebral aqueduct connects 3rd and 4th ventricles

Fourth ventricleWithin brainstem, just anterior to cerebellum

Figure 11.3 Ventricles in the brain. (a) anterior view. (b) lateral view.

Cerebrospinal FluidCSF is secreted by specialized capillaries called Choroid Plexuses• CSF complete surrounds brain and spinal cord

• Ependymal cells regulate the composition of CSF

• CSF functions as a nutritive and protective fluid.

Figure 10.4 (a) choroid plexuses in ventricle walls secrete CSF.

The fluid circulates through

ventricles and central canal.

Spinal TapThe spinal cord ends near the 2nd Lumbar vertebra, but the arachnoid and dura maters continue to the 2nd Sacral vertebra.

Thecal Sac –

space beyond spinal cord filled with CSF.

Spinal taps (lumbar punctures) and spinal blocks are usually given below the 4th lumbar vertebra to access the CSF without puncturing the spinal cord.

End of section 1, chapter 11