ANA 303 Spinal Cord

Question 1

The spinal cord is located________and extends from _______ to __________?

Where does it occupy?

Answer 1

The spinal cord is located within the vertebral canal and extends from the foramen magnum
(medullary spinal junction) to the first or second lumbar vertebra.

It occupies the upper two thirds of the vertebral
column. The rest of the cord is occupied by cauda equina

Question 2

The conical-shaped caudal end of the spinal
cord, known as the_____________

Answer 2

conus medullaris

Question 3

What is the filum terminale internum?

Answer 3

A thin filament enclosed in pia and consisting of glial cells, ependymal cells, and astrocytes emerges from the conus medullaris. This filament is called the filum terminale internum.

Question 3

What is the filum terminale externum?

Answer 3

At this level, a caudal thin extension
of the spinal dura, called the coccygeal ligament (filum terminale externum) surrounds the filum terminale.

Question 4

What anchors the spinal cord?

Answer 4

Filum terminale

Question 5

Why is it that in an adult, the spinal cord occupies only the upper two-thirds of the vertebral column?

Answer 5

The spinal cord occupies the whole length of the vertebral canal up to the third month of fetal life. Then it lengthens at a slower rate than the vertebral column

Question 6

What is the cauda equina?

Answer 6

The lumbosacral nerve roots surround the filum terminale and form a cluster that resembles the tail of a horse and that is called the cauda equina

Question 7

What is the lumbar cistern?

Answer 7

The subarachnoid space is the widest from the caudal end, L1. of the spinal cord to S2 and contains no CNS structures except the filum terminale and the nerve roots of cauda equina. This space is known as the lumbar cistern

Question 8

Clinical significance of lumbar cistern

Answer 8

Because of this anatomic feature, this space is most suitable for the withdrawal of cerebrospinal fluid (CSF) by lumbar puncture. The site for performing a lumbar puncture changes with age in childhood. For example, in children, the caudal end of the spinal
cord is usually located at the third lumbar vertebra (L3); therefore, the needle for lumbar puncture is inserted at the L4–L5 level

Question 9

How many segments does the spinal cord have?

Answer 9

31

Question 10

How many pairs of nerves does the spinal cord have? How many does each segment have?

Answer 10

31 pairs

Cervical 8 pairs
Thoracic 12 pairs
Lumbar 5 pairs
Sacral 5 pairs
Caudal 1 pairs

Question 11

At each level, the spinal nerves exit through the ____________

Answer 11

intervertebral foramina

Question 12

Each spinal nerve consists of a______________

Answer 12

dorsal root (containing afferent fibers) and a ventral root (containing efferent fibers).

Question 13

Function of the dorsal root ganglion

Answer 13

The spinal ganglion (dorsal root ganglion) is located within the intervertebral foramen and contains the neurons that give rise to afferent fibres entering dorsal horn of the spinal cord.

Question 14

The dorsal and ventral roots are joined distal to the spinal ganglion and form the___________

Answer 14

common spinal nerve

Question 14

Describe the cervical enlargement

Answer 14

The nerve roots emerging from this enlargement form the brachial plexus and innervate the upper extremities.

Question 14

Describe the lumbar enlargement

Answer 14

The lumbar plexus (comprising the nerve roots from L1–L4) and sacral plexus ( consisting of nerve roots from L4–S2) emerge from the lumbar enlargement. The lumbar
plexus innervates the lower extremities.

Question 15

The sacral spinal nerves contain and innervate____________

Answer 15

The sacral spinal nerves emerging from the conus medullaris contain parasympathetic fibres and motor fibres innervating the bladder
and its sphincters, respectively.

Question 16

Describe the internal structure of the spinal cord with reference to the matter

Answer 16

The inner core of the spinal cord is formed by grey matter, and it is surrounded by white matter at the periphery consisting of ascending and descending bundles of myelinated and unmyelinated axons that are called tracts or fasciculi.

A tiny central canal filled with CSF at its center.
Surrounding the canal is a single layer of cells, the ependymal layer.

Question 17

What is a funiculus?

Answer 17

A bundle containing one or more tracts or fasciculi is called a funiculus

Question 18

What are the 3 funiculi?

Answer 18

In each half of the spinal cord, there are
three funiculi: (1) the dorsal (posterior) funiculus, which is located between the dorsal horn and a midline structure called the dorsal (posterior) median septum;

(2) the lateral funiculus, which is located between the sites where the dorsal roots enter and ventral roots exit from the spinal cord; and

(3) the ventral (anterior) funiculus, which is located between the anterior (ventral) median fissure and the site where the ventral roots exit

Question 19

The anterior white commissure,
consisting of____________and located___________

Answer 19

decussating axons of nerve cells, is located
ventral to the gray commissure

Question 19

The two sides of the gray matter are connected by a band of gray matter called the _____________

Answer 19

gray commissure (lamina X).

Question 20

Where is the central canal located

Answer 20

in the grey commissure

Question 21

The general senses are classified as follows:

Answer 21

* Exteroception: Sensations perceived by the body, arising from the external world and including touch, pressure, vibration, pain, thermal sensation, itch, tickle, etc. * Proprioception: Sensations perceived by the body, generated by the own tissues and include perception of posture, joint position and movement, muscle contraction and stretch. * Interoception: Sensations perceived by the body, arising from the internal world and including sensations

Question 22

The ascending pathways are generally functional in

Answer 22

Fine/discriminitive touch Proprioception (kinaesthesia) Vibration

Question 23

What are the ascending tracts of the spinal cord in the posterior/ dorsal column (medial leminiscus) ? What are their functions?

Answer 23

Fasciculus gracilis (tract of Goll) Transmit signals from the lower limb (below T6) Fasciculus cuneatus (tract of Burdach) Transmit signals from the upper limb (above T6) Both are responsible for: Fine touch Vibration Proprioception Fasciculus gracilis and cuneatus pass directly to the ipsilateral posterior white column and ascend without synapse till they reach the brainstem. They synapse on the nuclei gracilis and cuneatus in the medulla oblongata

Question 24

What are the tracts under the anterolateral spinothalamic tracts? What are their functions?

Answer 24

Anterior spinothalamic tract: responsible for crude touch and pressure Lateral spinothalamic tract: pain and temperature They enter the spinal cord and travel for a segment or two in the posterolateral tract of Lissauer then synapse in lamina I, Il and IV. After synapse, fibers from the second-order neurons cross to the opposite side in the white and grey commissures and travel rostrally. The anterolateral system shows somatotopic organization. Sensation from lower parts of the body travel laterally while sensation from upper parts travel medially, Second-order neurons synapse in the ventral posterolateral and intralaminar thalamic nuclei, Third-order neurons send axons that pass through internal capsule to the somatosensory cortex.

Question 25

What are the tracts under the spinocerebellar pathways? What are their functions?

Answer 25

Divided into two tracts *DORSAL Spinocerebellar tract* This tract carries unconscious proprioception from **individual muscles** of the lower limb up to the cerebellum They Convey proprioception and deep pressure from the muscles to the cerebellum, The First-order neurons synapse on Clarke's column. Fibers from the second-order neurons enter the ipsilateral lateral white funiculus. Fibers from the second-order neurons ascend join the inferior cerebellar peduncle and terminate in the cerebellar cortex. Sensory fibers from sacral and lower lumbar travel rostrally until they meet and synapse on the Clarke's column *VENTRAL Spinocerebellar tract* This tract carries unconscious proprioception from ** the lower limb as a whole** up to the cerebellum Has the same function of the posterior spinocerebellar tract in addition to sensation from the skin. Axons synapse on Clarke's column and most of the second-order neurons decussate and ascend to enter the cerebellum via the superior cerebellar peduncle.

Question 26

Which tracts carry conscious and which carry unconscious information?

Answer 26

Conscious: Posterior column (fasciculus graciclis and cuneatus) Anterolateral spinothalamic tracts (anterior and lateral) Unconscious: Spinocerebellar tracts (anterior and posterior)

Question 27

What are the upper limb equivalents of the Spinocerebellar tracts (anterior and posterior)?

Answer 27

PST - cuneocerebellar tract AST - rostralspinocerebellar tract these carry proprioceptive info of the upper limb and neck to the cerebellum

Question 28

The descending pathways are generally functional in

Answer 28

response to sensory information

Question 29

The types of descending pathways

Answer 29

Pyramidal and extra-pyramidal tracts

Question 30

Why are they called pyramidal tracts

Answer 30

they pass through the medullary pyramids

Question 31

What are the pyramidal tracts? What are their functions?

Answer 31

Corticospinal tracts: Lateral Corticospinal tracts Anterior Corticospinal tracts They convey voluntary skilled movements

Question 32

What are the extra-pyramidal tracts? What are their functions?

Answer 32

Rubrospinal tract: facilitatory to flexors of the upper limb Tectospinal tract: involved in the coordination of head and movement with vision Medial reticulospinal tract (ponto): facilitates voluntary muscle contraction and an increase in muscle tone Lateral reticulospinal tract (medullary): inhibits voluntary movement, reduces muscle tone and plays a role in automatic breathing Vestibulospinal tract: helps control balance and posture

Question 33

Average length of SpinaI Cord in males and females

Answer 33

Average length of SpinaI Cord is 45 cm in Adult Males and, 42-43 cm in Adult Females

Question 34

Average Weight of Spinal cord

Answer 34

30-35 grams

Question 35

Average Length of Vertebral column

Answer 35

70 cm

Question 36

The spinal cord is enlarged at the cervical and lumbosacral parts to give the origin to the

Answer 36

brachial and lumbosacral plexuses, respectively.

Question 37

What is the anterior median fissure and posterior middle sulcus

Answer 37

The anterior median fissure is a deep longitudinal fissure in the anterior surface. The posterior median sulcus is a shallow sulcus in the posterior surface, It contains the posterior median septum (pia mater).

Question 38

What is the posterolateral and anterolateral sulcus?

Answer 38

The posterolateral sulcus is the entry site for the posterior root (sensory) fibers. The anterolateral Sulcus is the exit site for the anterior root (motor) fibers.

Question 39

What is the filum terminale?

Answer 39

Filum terminale is a prolongation of the pia mater from the apex of the conus medullaris to the posterior surface of the coccyx

Question 40

Describe the formation of the lumbar cistern

Answer 40

The subarachnoid space at the level of the cauda equina enlarges to form the lumbar cistern (site for lumbar puncture and spinal anesthesia).

Question 41

The pia mater attaches to the vertebral column laterally by the_____________

Answer 41

denticulate ligament

Question 42

Describe the grey matter (Grey commissure, Nuclei horns etc.)

Answer 42

They Composed of neuronal cell bodies, dendrites, initial parts of axons, and glial cells. Divided into dorsal (posterior) and ventral (anterior) horns (H shape in cross sections), The grey commissure connects the anterior and posterior horns. It contains the central canal. The dorsal horn receives sensory information while the ventral horn projects motor commands. The small lateral grey horn lie in the thoracic and upper lumbar segments. It functions as sympathetic synapse area. The posterior grey horn has four nerve groups: 1. Substantia gelatinosa group (lamina Il) 2 Nucleus proprius group (laminae Ill & IV) 3. Nucleus dorsal is group (Clarke's column lamina Vll) 4. Visceral afferent nucleus The substantia gelatinosa is located in the apex of the posterior grey horn throughout the spinal cord. It receives afferents conveying pain, touch, and temperature. The nucleus proprius is located anterior to the substantia gelatinosa throughout the spinal cord. It receives afferents conveying proprioception, two-point discrimination, and vibration from the posterior column. Clarke's column is situated at the base of the posterior grey horn from the lower cervical to the middle lumbar segment. It receives proprioceptive input (mainly muscle and tendon spindles). The visceral afferent nucleus lies lateral to the Clarke's column from the first thoracic to the third lumbar segment, It receives visceral afferent information

Question 43

Describe the white matter and the funiculi

Answer 43

The white matter of the spinal cord is divided into the following columns (funiculi): 1. Anterior column (between the midline and the anterior nerve roots) 2. Lateral column (between the anterior and posterior nerve roots) 3. Posterior column (between the posterior nerve roots and the midline) It contains nerve axons and neuroglia along with blood vessels. Each column is divided into tracts (fasciculi). These tracts can be ascending, descending, or intersegmental. The nomenclature of the tracts start with the origin and ends with the destination. For example spino____tract. (spinothalamic tracts) for ascending tract. Descending tracts are named ____spinal tract, For example: corticospinal tract.

Question 44

Ascending tracts are also known as__________

Answer 44

somatosensory pathways or systems.

Question 45

Describe the ascending tract

Answer 45

The ascending tracts refer to the neural pathways by which sensory information from the peripheral nerves is transmitted to the cerebral cortex. The Ascending tracts conducts the impulses from the periphery to the Brain through the Spinal cord.

Question 46

Each tract usually consists of three neurons

Answer 46

First-order neuron Second-order neuron Third-order neuron Second-order neurons decussate at different levels. Third-order neurons are usually found in the thalamus These neurons branch to give input to motor neurons and the reticular formation.

Question 47

Afferent axons of the first-order neurons have their cell bodies

Answer 47

in the dorsal root ganglia

Question 48

What are the ascending tracts?

Answer 48

Dorsal Column System Spinocerebellar System Anterolateral (spinothalamic) System

Question 49

Describe second order and third order neurons

Answer 49

Second-order neurons decussate and ascend forming the medial lemniscus to synapse in the ventral posterolateral nucleus of the thalamus. The third-order neurons pass through the internal capsule to reach the somatosensory cortex.

Question 50

Other ascending tracts

Answer 50

Spinotectal tract (visual reflexes), Spinoreticular tract. Spino -olivary tract Visceral sensory tracts.

Question 51

Spinal cord lesions

Answer 51

Lesion of a single posterior root will cause pain in the skin and muscles innervated by that root. Lesion of a single anterior root will cause paralysis to any muscle supplied exclusively by that root. Damage to the anterolateral system will cause contralateral loss of pain, temperature and crude touch below the level of the lesion. Damage to the dorsal column causes ipsilateral disruption of proprioception, pressure and vibration below the level of the lesion.

Question 52

Herpes zoster

Answer 52

Herpes zoster is a viral infection that affects sensory neurons, It is characterized by pain and inflammation with vesicles in the area of distribution of the affected nerve. This infection usually occur in the elderly.

Question 53

Tabes dorsalis

Answer 53

Tabes dorsalis (neurosyphilis) results from the selective destruction to the dorsal roots. This disease affects many sensations and reflexes. It also causes ataxia (impaired balance or coordination) and hypotonia (weak muscle tone).

Question 54

Spinal shock

Answer 54

Spinal shock results from severe injury to the spinal cord, All sensations, reflexes, and motor functions of the spinal cord below the level of the injury will be suppressed as a result. It may last to 24 hours or may extend to 12 weeks

Question 55

Syringomyelia

Answer 55

Syringomyelia is a developmental or acquired abnormality in the central canal usually in the brainstem and cervical spinal cord, It is characterized by cavitation and gliosis of the central part of the affected segment.

Question 56

The ascending pathway is sensory/motor The descending pathway is sensory/motor Which is true

Answer 56

The ascending pathway is sensory The descending pathway is motor

Question 57

Do neurons synapse in the gry or white matter?

Answer 57

grey matter

Question 58

all sensory information enters the spinal cord via the

Answer 58

dorsal horn

Question 59

all motor information leaves the spinal cord via the

Answer 59

ventral horn

Question 60

pathways for pain receptors under the spinothalamic tracts

Answer 60

A delta C fiber