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Flashcards in The Back - RR Deck (173):
1

What is important to remember about zygapophysial (facet) joints?

They are synovial joints that may develop osteoarthritis with age and trauma.

2

How are the intervertebral foramina formed?

They are formed between inferior and superior vertebral notches in pedicles of adjacent vertebrae - transmit spinal nerves and related blood vessels.

3

What may be caused by compressing the spinal nerve in intervertebral foramen?

Radiculopathy

4

What is important to remember about intervertebral foramina?

Any space-occupying lesion in an intervertebral foramen may compress the spinal nerve or its roots and produce back pain that may radiate into an extremity.
+ Motor fibers may be involved --> loss of strength.

5

How many are the total vertebrae?

33:
7C
12T
5L
5S
4 coccygeal

6

What are the three main features of a typical cervical vertebra?

1. Spinous processes allow neck extension because they are short.
2. Articular processes with nearly horizontal facets allow relatively free movement in all directions at the expense of stability.
3. Transverse foramen in each transverse process allows passage of vertebral artery and vein.

7

What is important to keep in mind about the vertebral artery?

Vertebral artery ascends transverse foramina of vertebrae C1-6.

8

What are the two main features of atlas?

1. Midline anterior tubercle on anterior arch and posterior tubercle on posterior arch.
2. Sulcus for vertebral artery on posterior arch on each side.

9

What is important to keep in mind about the dens of the axis?

May be congenitally absent or fail to fuse with the body of the axis.

10

Has atlas a body?

No

11

Has atlas a spinous process?

No - just tubercle on posterior arch.

12

How do we characterize the transverse processes of atlas?

Long and stout - transverse foramen.

13

What is special about the body of axis?

Dens projects superiorly from its body.

14

Has axis spinous process?

A short, often bifid one.

15

Describe the transverse processes of axis.

Short, transverse foramen.

16

Describe the bodies of C3-C6?

Small and broad transversely.

17

What is the vertebra prominens?

C7, because of its long spinous process, which helps counting the vertebrae.

18

What is special about the transverse foramina of C7?

Small and do not contain vertebral artery.

19

Why the cervical vertebrae are prone to dislocation?

Because articular surfaces lie in nearly horizontal plane and are less stable.
Although the spinal cord may be compressed, it may escape injury because of the large vertebral canal.

20

What is important to keep in mind about dislocations in the cervical spine?

Dislocations without fracture occur only in the cervical spine.

21

What happens in Klippel-Feil syndrome?

Failure of segmentation of cervical vertebrae --> congenital fusion --> short, stiff neck.

22

What characterizes the articular processes of thoracic vertebrae?

They are oriented to favor lateral bending and rotation, although range of movement is limited by the rib cage + thin intervertebral discs + overlapping spinous processes.

23

What may be produced by traumatic injury to the thoracic vertebrae?

Dislocation with fracture because articular facet joints are arranged vertically.

24

An aneurysm of the descending aorta may do what to the bodies of T5-8?

It may erode the bodies of T5-8 on the left side.

25

What is special about T1 and T10-12?

They have a complete facet for the head of the rib.

26

What is spondylolysis?

A fracture of the pars interarticularis that may cause spondylolisthesis.

27

What is the target group of spondylolysis?

In L5 commonly in young adolescent athletes involved in sports that require repeated spinal hyperextension.

28

What is the characteristic radiographic image of spondylolysis?

Scottie dog

29

Where is spondylolisthesis common?

In L5/S1 - often secondary to bilateral pars interarticularis fractures.

30

What are the problems with spondylolisthesis?

Alignment of the vertebral column is compromised - the cauda equina may be affected.
May encounter difficulty during childbirth because of the resulting narrowd pelvic inlet.

31

How can neurogenic claudication occur?

Degenerative diseases in the lumbar spine and ligamenta flava may cause narrowing of the spinal canal (spinal stenosis) --> pain on walking or standing, that is relieved by bending forward or sitting.

32

What are the articulations of the sacrum?

1. Lumbosacral joint (L5)
2. Sacroiliac joints

33

How many foramina does the sacrum have?

4 pairs anterior for anterior rami + the same for posterior rami of spinal nerves S1-S4.
Also sacral canal contains dural sac down to the lower border of S2.

34

Where is the sacral hiatus?

In place of spine and laminae of S5 (sometimes S4) with sacral cornua located laterally.

35

What is the importance of sacral cornua?

They are landmarks for caudal epidural anesthesia.

36

Between which two vertebrae isn't an intervertebral disc?

C1/C2 (also sacrum, coccyx).

37

What is the component of the intervertebral disc?

Hyaline cartilage

38

What are the two main functions of intervertebral discs?

1. Considerable flexibility of the column.
2. Shock absorbers.

39

What are the features of anulus fibrosus?

1. Fibrocartilaginous portion of disc surrounding nucleus pulposus - thinner posteriorly.
2. Firmly attached to anterior and posterior longitudinal ligaments.

40

What are the features of nucleus pulposus?

1. Incompressible gelatinous center of intervertebral disc located closer to its posterior surface.
2. Produces shock-absorbing quality of disc.
3. Loses water temporarily during daily activities and permanently with age --> Gradually becomes replaces by fibrocartilage.

41

What causes a herniated intervertebral disc?

Rupture of nucleus pulposus through the anulus fibrosus.

42

Where do herniated discs usually occur?

1. L4/L5 or L5/S1
2. C5/C6, C6/C7 (in younger than 50)

43

What nerve root will be affect in a L4/L5 herniation?

L5 nerve root.

44

What are the facet joints (zygapophysial/zygapophyseal)?

Synovial joints between superior and inferior articular facets of adjacent vertebrae --> Provide varying amounts of flexion, extension, rotation, or lateral bending depending on vertebral level.

45

What is a possible complication of osteoarthritis of facet joints?

Osteophytes may impinge on an adjacent spinal nerve, causing severe pain.

46

How can lumbar zygapophysial joints be denervated?

By surgical or percutaneous radiofrequency neurotomy (percutaneous rhizolysis) to relieve lower back pain.
--> Each joint is innervated by medial branches of two adjacent posterior rami - BOTH branches must be sectioned.

47

What is an important role of the posterior longitudinal ligament?

Because its presence reinforces the intervertebral disc in the posterior midline --> reduces the incidence of disc herniations that may compress the spinal cord and cauda equina.

48

What is the whiplash (cervical extension strain)?

Forceful hyperextension of the cervical spine that stretches the anterior longitudinal ligament and adjacent structures.

49

What may cause a whiplash?

Rear-end automobile collisions.

50

What are the symptoms of whiplash?

1. Neck pain
2. Headache
3. Pain + Numbness radiating into the upper extremities

51

Mention briefly the major features of the atlantooccipital joint?

1. Paired synovial joint between the occipital condyle and superior articular facet of atlas
2. Allows flexion/extension of head (nodding "yes") and some lateral flexion but no rotation.
3. Posterior atlantooccipital membrane penetrated by vertebral artery and suboccipital nerve.

52

Mention the major features of atlantoaxial joint.

1. Paired lateral atlantoaxial joints and median atlantoaxial joint with dens held against anterior arch of atlas by transverse ligament of atlas.
2. Allows rotation of head (shaking head "no") but no flexion, extension, or lateral bending.

53

What is the main complication of atlantoaxial dislocation or subluxation (partial dislocation)?

May injure the spinal cord and medulla.

54

When does subluxation occur?

After rupture of the transverse ligament of the atlas.

55

What conditions are associated with rupture of the transverse ligament of atlas?

1. Congenital weakness
2. Trauma
3. Rheumatoid arthritis
4. Down syndrome --> 15-20% have weak of ABSENT transverse ligament.

56

What must be done for subluxation due to rupture of the transverse ligament of the atlas to be apparent on a lateral x-ray?

The spine must be flexed.

57

Mention the main ligaments of the vertebral column.

1. Supraspinous
2. Interspinous
3. Anterior longitudinal
4. Posterior longitudinal
5. Ligamentum flavum

58

What is the attachment and the role of supraspinous ligament?

Attach: connects tips of spinous processes.
Role: Limits flexion of vertebral column - expanded in cervical region as ligamentum nuchae.

59

What is the attachment and the role of interspinous ligament?

Attach: connects spinous processes of adjacent vertebrae.
Role: Limits flexion of vertebral column.

60

What is the attachment and the role of anterior longitudinal ligament?

Attach: Anterior surface of vertebral bodies and intervertebral discs.
Role: Limits extension of vertebral column - supports anulus fibrosus and may be strained or torn in whiplash.

61

What is the attachment and the role of posterior longitudinal ligament?

Attach: Posterior surface of vertebral bodies and intervertebral discs and lies within vertebral canal.
Role: Limits flexion of the vertebral column - supports anulus fibrosus and directs herniation of intervertebral discs posterolaterally.

62

What is the attachment and the role of ligamentum flavum?

Attach: Paired ligament that connects laminae of adjacent vertebrae.
Role: Limits flexion of vertebral column - yellowish due to elastic tissue.

63

What are the main features of uncovertebral joints (of Luschka)?

1. Jointlike structures that can develop postnatally in cervical spine between lips of bodies of adjacent vertebrae.
2.Osteophyte formation --> may cause neck pain.

64

What is the cruciate ligament?

Consists of:
1. Transverse ligament of atlas
2. Superior longitudinal band
3. Inferior longitudinal band

65

Mention the 4 main craniocervical ligaments.

1. Tectorial membrane
2. Apical membrane
3. Alar ligament
4. Cruciate ligament

66

What is the attachment and the role of tectorial membrane?

Attach: Continuation of posterior longitudinal ligament from body of axis to anterior margin of foramen magnum.
Role: Cover dens and transverse ligament of atlas posteriorly.

67

What is the attachment of apical ligament?

Attach: Extends from apex of dens to anterior margin of foramen magnum.

68

What is the attachment and the role of alar ligament?

Attach: Stout paired ligament connecting side of dens to medial aspect of occipital condyle.
Role: Limits rotation at atlantoaxial joints.

69

What is the attachment and the role of cruciate ligament?

Attach: Expansion of transverse ligament of atlas.
Role: Bind dens tightly against anterior arch of atlas.

70

What is scoliosis?

ANY LATERAL curvature of spine.

71

What are the main types of scoliosis?

May be:
1. Thoracic
2. Lumbar
3. Thoracolumbar
Designated right or left according to convex side of major curve.
Also:
1. Nonstructural (reversible)
2. Structural (irreversible - idiopathic or neuropathic)

72

What is the MC form of scoliosis?

Idiopathic right thoracic scoliosis in adolescent females.
Additional spinal curves that place the eyes in a horizontal plane may develop to compensate.

73

What is the explanation of the rib hump that appears on the convex side during forward bending in structural scoliosis?

It is due to posterior displacement of ribs from vertebral rotation.

74

How can congenital scoliosis result?

1. Failure of one side of the vertebral body to form (hemivertebra).
2. Asymmetric fusion of vertebrae.

75

What is kyphosis?

Abnormal curvature that is convex posteriorly.

76

In what target group is kyphosis of the thoracic spine common?

In postmenopausal women.

77

What is Scheuermann's disease?

An adolescent form of kyphosis --> results from disturbances in hyaline cartilage growth plates of thoracic vertebral bodies.

78

Can kyphosis occur together with scoliosis?

Yes - Kyphoscoliosis.

79

What is lordosis?

Abnormal curvature that is convex anteriorly.

80

When do we normally see lordosis?

During pregnancy - normal compensation of lumbar spine.

81

What other condition is associated with lordosis?

Obesity in both males and females.

82

Describe briefly the development of the vertebral column.

1. Mesenchymal cells from sclerotome of somites form condensations around the neural tube and notochord.
2. Condensation and proliferation of caudal half of one sclerotome join cranial half of next sclerotome to form a vertebral body.

83

How is anulus fibrosus formed?

From mesenchymal cells of sclerotome that fill space between adjacent vertebral bodies as they form.

84

How is nucleus pulposus formed?

It is a remnant of the embryonic notochord --> Persists within each intervertebral disc and undergoes MUCOID DEGENERATION.

85

What are the major congenital abnormalities of the vertebral column and spinal cord?

1. Spina bifida occulta
2. Spina bifida cystica

86

What are the 3 main things to keep in mind about spina bifida occulta?

1. Results from vertabral arch failing to fuse in midline.
2. Frequently occurs at L5 or S1 and may be marked by a tuft of hair and/or pigmented skin.
3. NOT associated with neurological deficit.

87

What is the only way to detect a spina bifida occulta?

Only by x-ray.

88

What happens in spina bifida cystica?

Protrusion of meninges and/or spinal cord through defect in vertebral arches.

89

What is the incidence of spina bifida cystica?

Occurs in about 1/1000 births.

90

How is spina bifida cystica detected?

High levels of AFP in maternal serum or amniotic fluid.

91

What is a possible cause of spina bifida cystica?

May have reduced incidence with vitamin and folic acid supplements before conception.
Or increased incidence with valproic acid during week 4.

92

What is a spinal meningocele?

Protrusion of meninges through a defect in vertebral arches - may be associated with neurological deficits.

93

What is a meningomyelocele?

Protrusion of spinal cord and/or nerve roots in meningeal sac - causes neurological deficits that depend on level and extent of lesion.

94

What are the possible complications of meningomyelocele?

1. If only nerve roots are involved in spina bifida with meningomyelocele --> flaccid paralysis (lower motor neuron).
2. If spinal cord damage --> spastic paralysis (upper motor neuron).
3. Mixed types of paralysis.
4. Hydrocephalus commonly develops due to herniation of the brainstem + cerebellar tonsils through the foramen magnum - Arnold-Chiari malformation.
5. INFECTION of the exposed meninges and spinal cord.

95

Describe briefly the development of the back muscles.

1. Differentiating somites give rise to segmental myotomes --> each myotome splits into the DORSAL epimere and VENTRAL hypomere.
2. Epimere --> epaxial muscles (intrinsic back muscles) --> posterior rami of spinal nerves.
3. Hypomere --> hypaxial muscles --> anterior rami of spinal nerves.
4. Limb muscles --> from hypomere --> migrate into limb buds --> anterior rami.
5. Superficial muscles of the back --> actually muscles of upper limb --> develop from limb bud mesoderm and migrate into back --> carry nerve supply from anterior rami.

96

What is useful to remember about the innervation of back muscles?

Posterior rami --> Intrinsic back muscles.
Anterior rami --> ALL other muscles of trunk and extremities.

97

What is the triangle of auscultation?

Bounded:
Medially --> trapezius
Laterally --> scapula + rhomboid major
Inferiorly --> Latissimus dorsi

98

What is the importance of the triangle of auscultation?

Allows lung sounds to be clearly heard at 6th intercostal space because no muscle intervenes between skin and rib cage when shoulders are pulled forward.

99

What is the thoracolumbar fascia?

1. Forms investing sleeve that encloses intrinsic back muscles by attaching anteriorly to transverse processes of lumbar vertebrae and posteriorly to spinous processes of lumbar and thoracic vertebrae.
2. Fuses with aponeuroses of internal abdominal oblique, transversus abdominis and latissimus dorsi.

100

What are the borders of the suboccipital triangle?

Medially --> rectus capitis posterior major
Inferiorly --> obliquus capitis inferior
Laterally --> obliquus capitis superior muscles

101

What is the course of the vertebral artery?

Branches from subclavian --> ascends through transverse foramina of C1-C6 --> runs transversely across posterior arch of atlas under posterior atlantooccipital membrane.

102

What is the course of the suboccipital nerve?

Posterior ramus of C1 --> passes between vertebral artery and posterior arch of atlas --> supply suboccipital muscles.

103

What is the course of the greater occipital nerve?

Posterior ramus of C2 --> emerges inferior to obliquus capitis inferior muscle --> ascends to supply overlying muscles and scalp.

104

What is the course of the 3rd occipital nerve?

Posterior ramus of C3 --> supplies scalp over occiput.

105

What is very interesting about individuals with atherosclerotic vertebral artery?

May result in brainstem ischemia during neck rotation.

106

What is the subclavian steal syndrome?

Reversed blood flow through vertebral artery with upper extremity exertion.

107

When does subclavian steal syndrome occur?

When the left subclavian artery or the branchiocephalic trunk is stenosed or occluded proximal to the origin of the vertebral artery.

108

What are the transient neurologic symptoms related to subclavial steal syndrome?

Brainstem and posterior cerebral ischemia --> Dizziness, unsteadiness, visual changes.

109

Where does dura end?

Inferiorly at S2 vertebra.

110

What is the relationship of dura with the epineurium of spinal nerve?

Follows spinal nerve roots and is continuous with epineurium of spinal nerve.

111

Where does adult spinal cord end?

At vertebra L1/L2.

112

Give an overview of arachnoid mater.

1. Delicate intermediate layer applied to inner surface of dura matter
2. Sends fine arachnoid trabeculae across subarachnoid space to pia mater.

113

Give an overview of pia mater?

Fine vascular layer inseparable from surface of spinal cord.

114

What is the Brudzinski's sign, seen in meningitis?

Flexion of the neck of a supine patient will stretch inflamed meninges --> characteristic pain --> elicits possibly involuntary hip and knee flexion that minimizes tension on the meninges.

115

What is Kernig's sign, seen in meningitis?

Similar pain elicited by raising one lower limb while the knee is kept fully extended (straight leg raise).

116

Give an overview of epidural space.

1. Lies between dural sac and walls of vertebral canal.
2. Contains epidural fat and internal vertebral venous plexus.

117

Give an overview of subdural space.

1. Artifact of pathology and not a true space.
2. Formed by physical separation of dura mater from arachnoid mater by hemorrhage (subdural hematoma) or CSF collection (subdural hygroma).

118

Give an overview of subarachnoid space.

1. Lies between the arachnoid mater and pia mater and extends inferiorly to S2 vertebra.
2. Contains CSF that protects spinal cord and removes catabolites from neuronal activity.
3. Below spinal cord forms lumbar cistern --> contains cauda equina.

119

Where is lumbar puncture usually performed?

Between vertebrae L3/L4 or L4/L5.

120

Why do we do a lumbar puncture?

1. To extract CSF
2. To inject anesthetic (spinal block)
3. To inject contrast material

121

Where does the spinal cord ends in infants?

L3 (also in some adults).

122

In what patients is lumbar puncture contraindicated?

In patients with an intracranial mass - check for papilledema (incr. intracranial pressure.

123

What happens in epidural anesthesia?

The needle is placed into the epidural space to inject anesthetic around roots of the lower lumbar and sacral spinal nerves without entering the subarachnoid space. (spinal block: inject into subarachnoid space)

124

What are the denticulate ligaments?

Flattened fibrous bands of pia mater from sides of spinal cord between posterior and anterior nerve rootlets --> Have tooth-like projections that pierce arachnoid mater to anchor spinal cord to dura.

125

What is the filum terminale?

Threadlike inferior extension of pia mater from conus medullaris surrounded by cauda equina in lumbar cistern.
Penetrates arachnoid mater and dura mater to become enclosed by filum of dura - which attaches to coccyx.

126

What is important to keep in mind about denticulate ligaments and filum terminale of pia mater?

Anchor the spinal cord in subarachnoid space.

127

What is the vertebral venous plexus?

Interconnecting system of VALVELESS veins from coccyx to skull that allows blood flow in either direction.

128

Are there any anastomoses of vertebral venous plexus?

YES - with segmental veins at all levels and with dural venous sinuses of cranial cavity.

129

What is the location of the internal vertebral venous plexus?

Lies in epidural space around dural sac.

130

What is the location of external vertebral venous plexus?

Surrounds outside of vertebral column.

131

What is ESPECIALLY important to keep in mind about the vertebral venous plexus?

Provides a pathway for TUMOR cells to metastasize from pelvic, abdominal, and thoracic viscera to vertebrae, spinal cord, and brain.
Prostate + breast + lung --> spread to brain via this plexus.

ALSO --> Infections of the skin of the back may also spread to dural venous sinuses of the cranial cavity.

132

What is the range of "spinal cord end"?

T12-L3. (Usually ends near the SUPERIOR border of vertebra L2)

133

What is conus medullaris?

The inferior end in which the spinal cord tapers.

134

Which are the spinal arteries?

Comprise one anterior spinal artery and paired posterior spinal arteries - which arise from vertebral arteries or posterior inferior cerebellar arteries.

135

What are the sources of the segmental arteries?

1. Vertebral
2. Ascending cervical
3. Deep cervical
4. Posterior intercostal
5. Lumbar segmental

136

What is the role of segmental arteries?

Supply blood directly to:
1. Spinal nerves
2. Nerve roots
3. Adjacent areas of spinal cord
--> RADICULAR arteries
Also --> segmental medullary arteries --> supplement blood to spinal cord through anastomoses with anterior and posterior spinal arteries.

137

Mention one segmental artery of special importance.

The great (major) anterior segmental medullary artery.

138

From where is great anterior segmental medullary artery arises?

From a lower intercostal or upper lumbar artery.

139

Why is great anterior segmental medullary artery important?

It may supply as much as the inferior 2/3 of the spinal cord.

140

What may loss of flow through the great anterior segmental medullary artery cause?

Paraplegia and sensory loss.

141

How many are the spinal nerves?

31 pairs of nerves - 8C, 12T, 5L, 5S, 1 coccygeal --> attached to corresponding spinal cord segment.

142

How are the spinal nerves numbered?

According to the vertebra above - except in cervical region.

143

How are the spinal nerves formed?

By the union of posterior and anterior root and divide into posterior and anterior rami.

144

Describe briefly the posterior root (dorsal root).

Contains axons of AFFERENT neuron cell bodies located in the posterior root ganglion that carry sensory information from muscle, bone, joints, and skin.
--> Strip of skin it supplies is a DERMOTOME.

145

Describe briefly the anterior root (ventral root) of a spinal nerve.

Contains axons of EFFERENT neuron cell bodies located in the anterior horn gray matter of spinal cord that innervate SKELETAL MUSCLE.

146

Give a definition of ganglion.

Collection of nerve cell bodies outside the CNS.

147

What does the anterior root also contain at T1-L2 level?

Axons of visceral EFFERENT (preganglionic sympathetic) neuron cell bodies located in intermediolateral cell column of spinal cord --> innervate cardiac muscle + smooth muscle + glands.

148

What does the posterior ramus innervate?

Intrinsic back muscles + overlying skin.

149

What does the anterior ramus innervate?

Supplies:
1. Muscles + skin of anterolateral neck/trunk.
2. All muscles + skin of upper and lower extremities.

150

Mention briefly the main functional components of the spinal nerves.

1. General visceral afferent (GVA)
2. General somatic afferent (GSA)
3. General somatic efferent (GSE)
4. General visceral efferent (GVE)

151

How are the somatic plexuses formed?

By mixing nerve fibers from ANTERIOR rami.

152

What are the 4 main somatic nerve plexuses?

Cervical --> C1-C4
Branchial --> C5-L1
Lumbar --> L1-L4
Sacral --> L4-S3

153

What is achieved by the somatic nerve plexuses?

Allow nerve fibers from several spinal cord segments to be distributed in ONE peripheral nerve.

154

Describe briefly the stages of neural tube formation (neurulation).

1. Neural plate (neuroectoderm) --> induced by the notochord + prechordal plate.
2. Developing neural tube --> initially open at both ends (cranial/caudal neuropores).
3. Brain --> Rostral swellings of neural tube after closure of cranial neuropore.
4. Spinal cord --> Caudal neural tube on closure of caudal neuropore.

155

What is myeloschisis (rachischisis)?

An open spinal cord caused by failure of the caudal neuropore to close at the end of week 4.

156

What are the complications of myeloschisis?

Severe neurological deficits are produced + infection is likely.

157

What is anencephaly?

Failure of the cranial neuropore to close on day 25.

158

What are the structures innervated and the location of GSA?

Structures --> Sensory from:
Skin - Muscle - Bone - Joints of body wall - Neck - Extremities.
Loc. --> Posterior root ganglion.

159

What are the structures innervated and the location of GVA?

Sensory from:
Viscera, including circulatory system.
Loc. --> Posterior root ganglion.

160

What are the structures innervated and the location of GSE?

Motor to:
Skeletal muscle developed from somites (lower motor neurons).
Loc. --> Anterior horn gray matter.

161

What are the structures innervated and the location of GVE?

Motor to:
Smooth muscle - Cardiac muscle - Glands.
Loc. --> Sympathetic chain ganglion.

162

What is the function of GSA, GVA, GSE, GVE?

GSA --> Pain - Temperature - Touch - Proprioception receptors.
GVA --> Pain from internal organs may result from stretch - inflammation - spasm - ischemia.
GSE --> Voluntary control of movement.
GVE --> Involuntary - postganglionic sympathetic.

163

From where does the neural crest arise?

From junction of neural tube + surface ectoderm.

164

What does the neural crest form?

1. Dorsal root ganglia
2. Autonomic ganglia
3. Adrenal medulla

165

What is the possible course of the axons of preganglionic neurons of SNS?

Axons may synapse on postganglionic neuron cell body in sympathetic chain ganglion at level of entrance into sympathetic trunk - OR may ascend/descend in sympathetic chain before synapsing in another ganglion
- May pass into splanchnic nerve to reach abdominal prevertebral ganglion to synapse.

166

Where are the postganglionic sympathetic neuron cell BODIES located?

In paravertebral or prevertebral ganglia.

167

What is the course of the postganglionic sympathetic neuron?

1. Axon leaves paravertebral ganglion through gray ramus communicans to join spinal nerve or through visceral branch to join visceral plexus.
2. Axon leaves prevertebral ganglion to join visceral plexus.

168

What is the gray ramus communicans?

1. Connects sympathetic ganglion to its corresponding spinal nerve.
2. Carries post ganglionic sympathetic fibers that end on:
Sweat glands - Vascular smooth muscle - Arrector pili muscles of skin.

169

What is the white ramus communicans?

1. Connects each paravertebral ganglion from T1-L2 levels to corresponding spinal nerve.
2. Carries preganglionic sympathetic fibers to sympathetic trunk for distribution to entire body - including head.
3. Contains preganglionic sympathetic fibers + visceral afferent fibers.

170

What is important to remember about gray and white communicating rami?

White --> connect ONLY spinal nerves T1-L2.
Gray --> connect ALL spinal nerves.

171

What are 2 interesting features of PNS to keep in mind?

1. Innervates visceral structures ONLY and is NOT distributed to body wall or extremities.
2. Innervates ERECTILE TISSUE of genitalia + CORONARY ARTERIES --> BUT NO OTHER BLOOD VESSEL.

172

Give an overview of GVA?

1. Accompany sympathetic and parasympathetic fibers and form afferent limb of autonomic reflex arcs.
2. Follow sympathetic and parasympathetic nerve fibers to CNS - EXCEPT for cranial nerve III.
3. Transverse WHITE, not gray, ramus communicans.
4. Accompanying sympathetic nerve fibers in visceral branches (cardiac or splanchnic nerves) --> carry PAIN from visceral organs to spinal cord (T1-L2).

173

What are the main structures of a typical vertebra?

1. Body
2. Vertebral arch
3. Processes for muscular attachment and articulation with adjacent vertebrae.
4. Vertebral foramen