Ap2 Final Study Guide - Chapter 13 Part 1

Front 1

Meninges

Back 1

- 3 protective, connective tissue coverings that encircle the spinal cord and brain

- From superficial to deep, they are :

1. dura mater

2. arachnoid mater

3. pia mater

Front 2

Spinal Meninges

Back 2

- Surround the spinal cord and are continuous with the cranial meninges, which encircle the brain

- All 3 spinal meninges cover the spinal nerves up to the point where they exit the spinal column through the intervertebral foramina

Front 3

The spinal cord is also protected by ________

Back 3

- A cushion of fat and connective tissue located in the epidural space, a space between the dura mater and the wall of the vertebral canal)

Front 4

Meningeal Layers : Dura Mater 1

Back 4

- The most superficial of the 3 spinal meninges

- A thick, strong layer composed of dense, irregular connective tissue

Front 5

Meningeal Layers : Dura Mater 2

Back 5

- Forms a sac from the level of the foramen magnum in the occipital bone, where it is continuous w/ the meningeal dura mater of the brain, to the 2nd sacral vertebra

- Continuous w/ the epineurium, the outer covering of spinal and cranial nerves

Front 6

Meningeal Layers : Arachnoid Mater 1

Back 6

- This layer, the middle of the meningeal membranes, is a thin, avascular covering composed of cells and thin, loosely arranged collagen and elastic fibers

- It is called the arachnoid mater b/c of its spider's web arrangement of delicate collagen fibers and some elastic fibers

Front 7

Meningeal Layers : Arachnoid Mater 2

Back 7

- It is deep to the dura mater and is continuous through the foramen magnum with the arachnoid mater of the brain

- Between the dura mater and the arachnoid mater is a thin subdural space, which contains interstitial fluid

Front 8

Meningeal Layers : Pia Mater 1

Back 8

- This innermost meninx is a thin transparent connective tissue layer that adheres to the surface of the spinal cord and brain

- Consists of thin squamous to cuboidal cells w/in interlacing bundles of collagen fibers and some fine elastic fibers

Front 9

Meningeal Layers : Pia Mater 2

Back 9

- W/in the pia mater are many blood vessels that supply oxygen and nutrients to the spinal cord

- Triangular-shaped membranous extensions of the pia mater, called denticulate ligaments, suspend the spinal cord in the middle of its dural sheath

Front 10

Meningeal Layers : Pia Mater 3

Back 10

- Denticulate ligaments are thickenings of the pia mater

- They project laterally and fuse w/ the arachnoid mater and inner surface of the dura mater between the anterior and posterior nerve roots of spinal nerves on either side

Front 11

Meningeal Layers : Pia Mater 4

Back 11

- Extending along the entire length of the spinal cord, the denticulate ligaments protect the spinal cord against sudden displacement that could result in shock

- Between the arachnoid mater and pia mater is a space, the subarachnoid space, which contains shock-absorbing cerebrospinal fluid

Front 12

Spinal Cord 1

Back 12

- Located w/in the vertebral canal of the vertebral column

- The vertebral foramina of all the vertebrae, stacked one on top of the other, form the vertebral canal

- The surrounding vertebrae provide a sturdy shelter for the enclosed spinal cord

- The vertebral ligaments, meninges, and cerebro. fluid provide additional protection

Front 13

Spinal Cord 2

Back 13

- Roughly oval in shape, being flattened slightly anteriorly and poteriorly

- In adults, it extends from the medulla oblongata, the inferior part of the brain, to the superior border of the 2nd lumbar vertebra

Front 14

Spinal Cord 3

Back 14

- In newborn infants, it extends to the 3rd or 4th lumbar vertebra. During early childhood, both the spinal cord and vertebral column grow longer as part of overall body growth

- Elongation of the spinal cord stops around age 4 or 5, but growth of the vertebral column continues

Front 15

Spinal Cord 4

Back 15

- The length ranges from 42-45 cm

- Its diameter is about 2 cm in the midthoracic region, somewhat larger in the lower cervical and midlumbar regions, and smallest at the inferior tip

Front 16

When the spinal cord is viewed externally, two conspicuous enlargements can be seen.

Back 16

- The superior enlargement, the cervical enlargement, extends from the 4th cervical vertebra (C4) to the 1st thoracic vertebra (T1)

- Nerves to and from the upper limbs arise from the cervical enlargement

Front 17

The inferior enlargement,

Back 17

- Called the lumbar enlargement, extends from the 9th to the 12th thoracic vertebra

- Nerves to and from the lower limbs arise from the lumbar enlargement

Front 18

Inferior to the lumbar enlargement, the spinal cord terminates as a tapering, conical structure called _________

Back 18

- The conus medullaris, which ends at the level of the intervertebral disc between the 1st and 2nd lumbar vertebra in adults

- Arising from the conus medullaris is the filum terminale, an extension of the pia mater that extends inferiorly and fuses w/ the arachnoid mater and dura mater and anchors the spinal cord to the coccyx

Front 19

Roots

Back 19

- Two bundles of axons that connect each spinal nerve to a segment of the spinal cord by even smaller bundles of axons called rootlets

Front 20

Posterior (Dorsal) Root

Back 20

- And rootlets contain only sensory axons, which conduct nerve impulses from sensory receptors in the skin, muscles, and internal organs into the CNS

- Each posterior root has a swelling, the posterior (dorsal) root ganglion, which contains the cell bodies of sensory neurons

Front 21

Anterior (Ventral) Root

Back 21

- And rootlets contain axons of motor neurons, which conduct nerve impulses from the CNS to effectors (muscles and glands)

Front 22

The roots of these lower spinal nerves (lumbar, sacral, coccygeal) angle inferiorly alongside the filum terminale in the vertebral canal like wisps of hair.

Back 22

- Accordingly, the roots of these nerves are collectively named the cauda equina, meaning "horse's tail"

Front 23

A transverse section of the spinal cord reveals regions of white matter that surround an inner core of gray matter. The white matter of the spinal cord consists primarily of bundles of myelinated axons of neurons.

Back 23

- 2 grooves penetrate the white matter of the spinal cord and divide it into right and left sides

- The anterior median fissure is a wide groove on the anterior (ventral) side

- The posterior median sulcus is a narrow furrow on the posterior (dorsal) side

Front 24

The white matter of the spinal cord is shaped like the letter H or a butterfly; it consists of dendrites and cell bodies of neurons, unmyelinated axons, and neuroglia.

Back 24

- The gray commissure forms the crossbar of the H

- In the center of the gray commissure is a small space called the central canal; it extends the entire length of the spinal cord and is filled w/ cerebrospinal fluid

Front 25

At its superior end, the central canal is continuous with ________

Back 25

- The 4th ventricle (a space that contains cerebrospinal fluid) in the medulla oblongata of the brain

- Anterior to the gray commissure is the anterior (ventral) white commissure, which connects the white matter of the right and left sides of the spinal cord

Front 26

In the gray matter of the spinal cord and brain, clusters of neuronal cell bodies form functional groups called _________

Back 26

- Nuclei

- Sensory nuclei receive input from receptors via sensory neurons, and motor nuclei provide output to effector tissues via motor neurons

- The gray matter on each side of the spinal cord is subdivided into regions called horns

Front 27

Posterior (Dorsal) Gray Horns

Back 27

- Contain cell bodies and axons of interneurons as well as axons of incoming sensory neurons

- Recall that cell bodies of sensory neurons are located in the posterior (dorsal) root ganglion of a spinal nerve

Front 28

Anterior (Ventral) Gray Horns

Back 28

- Contain somatic motor nuclei, which are clusters of cell bodies of somatic motor neurons that provide nerve impulses for contraction of skeletal muscles

Front 29

Between the posterior and anterior gray horns are ______

Back 29

- The lateral gray horns, which are present only in the thoracic and upper lumbar segments of the spinal cord

- Contain autonomic motor nuclei, which are clusters of cell bodies of autonomic motor neurons that regulate the activity of cardiac muscle, smooth muscle, and glands

Front 30

As spinal nerves branch from the spinal cord, they pass laterally to exit the vertebral canal through the intervertebral foramina between adjacent vertebra.

Back 30

- B/c the spinal cord is shorter than the vert. column, nerves that arise from the lumbar, sacral, and coccygeal regions of the spinal cord do not leave the vertebral column at the same level they exit the cord