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How long is the vertebral canal in an adult?
extends from the foramen magnum to L2 vertebra
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How long is the vertebral canal in a smal child?
extends to L3 vertebra
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How long is the vertebral canal in a 3-month old fetus?
extends to the coccyx
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Which grows faster, the vertebral column or the spinal cord?
vertebral column
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What is the length of the spinal cord in the adult?
18 inches (45cm)
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Name the enlargements of the spinal cord?
cervical enlargement and lumbar enlargement
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What is the purpose of the cervical enlargement?
provide origin for nerves to upper extremity (has larger anterior horns)
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What is the purpose of the lumbar enlargement?
provides origin for nerves to lower extremity
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What type of neurons originate in the ventral (anterior) horn of the spinal cord?
motor neurons
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How many types of nerve rootlets are there?
2
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How do nerve rootlets get their name?
named according to their relative positions
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What are the 2 types of nerve rootlets?
- dorsal (posterior) rootlets
- ventral (anterior) rootlets
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The dorsal rootlets form:
dorsal nerve root
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The ventral rootlets form:
ventral nerve root
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The dorsal and ventral nerve roots merge to form:
spinal N
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conus medularis=
- the end of the spinal cord
- termination of spinal cord
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cauda equina:
collection of nerve roots streaming inferiorly below the conus medularis
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Where is the pia mater located?
- it is the most intimate covering of the spinal cord
- forms outer layer of spinal cord
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filum terminale
formed by pia mater at inferior limit of spinal cord
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denticulate ligaments
lateral extensions of pia mater which attach to inner surface of dura mater
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What is the function of denticulate ligaments?
anchor spinal cord to the dura mater
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How many layers of tissue does the arachnoid membrane have?
2
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What is the texture of the outer layer of the arachnoid membrane?
smooth
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Where is the outer layer of the arachnoid membrane?
in physical contact with the dura mater
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Describe the inner layer of the arachnoid membrane:
gives rise to fibers that pass to the pia mater, thereby transversing the subarachnoid space
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Where does the arachnoid membrane extend to?
the level of S2 vertebra
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Where is the subarachnoid space?
between the arachnoid membrane and pia mater
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What is the subarachnoid space filled with?
cerebrospinal fluid (CSF)
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Where can a needle be inserted to gain a sample of CSF?
between L4/L5 or L5/S1 vertebra
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What is the length of the subarachnoid space?
- extends from the cranial cavity to level of S2 vertebra
- continuous with cranial subarachnoid space
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How far does the dura mater extend?
- continuous with cranial dura mater
- extends to level of S2 vertebra
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What is the dura mater composed of?
tough collangenous tissue
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Is there a subdural space?
- in pathological situations the dura mater can be separated from the arachnoid membrane by fluid or tumor tissue
- subdural space is normally a "potential space" --since the dura mater is normally in contact with the arachnoid membrane no space is present
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How far does the subdural space extend?
to the level of S2 vertebra
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How far does the epidural space extend?
from foramen magnum to sacrum (sacral canal)
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Where is the epidural space located?
between spinal dura mater and vertebral canal
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What is contained in the epidural space?
blood vessels (internal vertebral venous plexus), fat, fatty connective tissue
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What is the epidural space good for?
- regional anesthesia such as an "epidural"
- NN absorb and relieves pain
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How many spinal nerves are there?
31 pairs
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How many cervical spinal nerves?
8
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How many thoracic spinal nerves?
12
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How many lumbar spinal nerves?
5
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How many sacral spinal nerves?
5
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How many coccygeal spinal nerves?
1
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One pair of spinal nerves corresponds to...
one spinal cord level, from which it originates
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What is a dermatome?
an area of skin innervated by one pair of spinal nerves
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What forms the anterior spinal artery?
union of two anterior spinal branches of the two vertebral AA
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How far does the anterior spinal artery descend?
to the conus medullaris
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Posterior spinal arteries (L/R) are branches of:
vertebral arteries
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Which is smaller? posterior spinal arteries or anterior spinal artery?
posterior spinal arteries
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How do segmental spinal arteries enter the vertebral canal?
intervertebral foramen
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The cervical branches of the segmental spinal arteries orginate from:
vertebral arteries, thyrocervical trunk and costocervical trunk
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Where do the thoracic branches of the segmental spinal arteries come from?
posterior intercostal arteries
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Where do the lumbar branches of the segmental spinal arteries come from?
lumbar arteries
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What do the segmental arteries supply?
- vertebrae
- intervertebral discs
- contents of epidural space
- dura mater
- spinal cord
- contents of vertebral canal
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Which side of the body is the Artery of Adamkiewicz on?
Left
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What is the Artery of Adamkiewicz also known by?
greater anterior medullary A
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What does the artery of Adamkiewicz do?
reinforces circulation to lumbar enlargement of spinal cord
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What artery does the artery of Adamkiewicz anastomosis with?
anterior spinal A
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Where does the artery of Adamkiewicz come from?
thoracic aorta
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Where does the spinal cord drain blood to?
a venous plexus (network) on the surface of the spinal cord
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Where is the spinal venous plexus located?
in the subarachnoid space
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What do the surface venous plexus connect to?
internal vertebral plexus
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Where are internal vertebral plexus located?
epidural space
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Where do the internal vertebral plexus drain to?
intervertebral veins
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Where do the intervertebral veins drain?
to the external vertebral plexus
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Where are the external vertebral plexus?
surrounds vertebral column
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External vertebral plexus receive blood from:
internal venous plexus
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Do the vertebral venous plexuses hae functional valves?
NO
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What does it mean for the vertebral venous plexuses to have no functional valves?
blood can flow in any direction as influenced by gravity
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What are included in Batson's veins?
- external and internal vertebral venous plexuses
- connects cranial cavity with venous plexuses in the pelvic cavity
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Since there are no valves in the vertebral plexuses, what could happen with metastatic cells originating in the pelvic region?
They can travel to the cranial cavity where secondary malignant tumors can develop
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What is the dorsal root ganglion?
collection of nerve cell bodies in the PNS
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The dorsal nerve root of the spinal cord has what kind of neurons?
sensory/afferent
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The ventral nerve root of the spinal cord has what kind of neurons?
motor/efferent
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The dorsal and ventral primary rami have what kind of neurons?
both sensory and motor
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Soma
skin, skeletal muscle, and bone
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afferent neurons
sensory from soma TO spinal cord
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Efferent neurons
motor FROM spinal cord to skeletal muscles
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General Somatic Afferent detects:
touch, pressure, pain, and temperature
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In the General Somatic Afferent, information goes to:
spinal cord and then brain
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General Somatic Efferent information goes to:
skeletal muscles
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