HTMS SELF ASSESSMENT ANATOMY (BACK) POOLS

BACK

Vertebral Column

I. General Characteristics

II. Typical Vertebra

III. Intervertebral Disks

IV. Regional Characteristics of Vertebrae

V. Ligaments of the Vertebral Column

VI. Vertebral Venous System

Soft Tissues of the Back

I. Superficial Tissues

II. Deep Tissues

III. Suboccipital Area

Spinal Cord and Associated Structures

I. Spinal Cord

II. Spinal Nerves

III. Meninges

IV. Structures Associated with the Spinal Cord

V. Dermatome, Myotome, and Sclerotome

VI. Development of Back Structures

1. During an outbreak of meningitis at a local college, a 20-year-old student presents to a

hospital emergency department complaining of headache, fever, chills, and stiff neck.

On examination, it appears that he may have meningitis and needs a lumbar puncture or

a spinal tap. Cerebrospinal fluid (CSF) is normally withdrawn from which of the following

spaces?

(A) Epidural space

(B) Subdural space

(C) Space between the spinal cord and the pia mater

(D) Subarachnoid space

(E) Space between the arachnoid and dura maters

2. A 23-year-old jockey falls from her horse and complains of headache, backache, and weakness. Radiologic examination would reveal blood in which of the following spaces if the internal vertebral venous plexus was ruptured?

(A) Space deep to the pia mater

(B) Space between the arachnoid and dura maters

(C) Subdural space

(D) Epidural space

(E) Subarachnoid space

3. A 42-year-old woman with metastatic breast cancer is known to have tumors in the intervertebral foramina between the fourth and fifth cervical vertebrae and between the fourth and fifth thoracic vertebrae. Which of the following spinal nerves may be damaged?

(A) Fourth cervical and fourth thoracic nerves

(B) Fifth cervical and fifth thoracic nerves

(C) Fourth cervical and fifth thoracic nerves

(D) Fifth cervical and fourth thoracic nerves

(E) Third cervical and fourth thoracic nerves

4. A 39-year-old woman with headaches presents to her primary care physician with a possible herniated disk. Her magnetic resonance imaging (MRI) scan reveals that the posterolateral protrusion of the intervertebral disk between L4 and L5 vertebrae would most likely affect nerve roots of which of the following spinal nerves?

(A) Third lumbar nerve

(B) Fourth lumbar nerve

(C) Fifth lumbar nerve

(D) First sacral nerve

(E) Second sacral nerve

5. A 57-year-old woman comes into her physician’s office complaining of fever, nausea,

vomiting, and the worst headache of her life. Tests and physical examination suggest

hydrocephalus (widening ventricles) resulting from a decrease in the absorption of cerebrospinal fluid (CSF). A decrease of flow in the CSF through which of the following structures would be responsible for these findings?

(A) Choroid plexus

(B) Vertebral venous plexus

(C) Arachnoid villi

(D) Internal jugular vein

(E) Subarachnoid trabeculae

6. After a 26-year-old man’s car was broadsided by a large truck, he is brought to the emergency department with multiple fractures of the transverse processes of the cervical and upper thoracic vertebrae. Which of the following muscles might be affected?

(A) Trapezius

(B) Levator scapulae

(C) Rhomboid major

(D) Serratus posterior superior

(E) Rectus capitis posterior major

7. A 27-year-old mountain climber falls from a steep rock wall and is brought to the emergency department. His physical examination and computed tomography (CT) scan reveal dislocation fracture of the upper thoracic vertebrae. The fractured body of the T4 vertebra articulates with which of the following parts of the ribs?

(A) Head of the third rib

(B) Neck of the fourth rib

(C) Tubercle of the fourth rib

(D) Head of the fifth rib

(E) Tubercle of the fifth rib

8. A young toddler presents to her pediatrician with rather new onset of bowel and bladder

dysfunction and loss of the lower limb function. Her mother had not taken enough folic acid (to the point of a deficiency) during her pregnancy. On examination, the child has protrusion of the spinal cord and meninges and is diagnosed with which of the following conditions?

(A) Spina bifida occulta

(B) Meningocele

(C) Meningomyelocele

(D) Myeloschisis

(E) Syringomyelocele

9. A 34-year-old woman crashes into a tree during a skiing lesson and is brought to a hospital with multiple injuries that impinge the dorsal primary rami of several spinal nerves. Such lesions could affect which of the following muscles?

(A) Rhomboid major

(B) Levator scapulae

(C) Serratus posterior superior

(D) Iliocostalis

(E) Latissimus dorsi

10. During a domestic dispute, a 16-year-old boy receives a deep stab wound around the superior angle of the scapula near the medial border, which injures both the dorsal scapular and spinal accessory nerves. Such an injury could result in paralysis or weakness of which of the following muscles?

(A) Trapezius and serratus posterior superior

(B) Rhomboid major and trapezius

(C) Rhomboid minor and latissimus dorsi

(D) Splenius cervicis and sternocleidomastoid

(E) Levator scapulae and erector spinae

11. An elderly man at a nursing home is known to have degenerative brain disease. When cerebrospinal fluid (CSF) is withdrawn by lumbar puncture for further examination, which of the following structures is most likely penetrated by the needle?

(A) Pia mater

(B) Filum terminale externum

(C) Posterior longitudinal ligament

(D) Ligamentum flavum

(E) Annulus fibrosus

12. A 27-year-old stuntman is thrown out of his vehicle prematurely when the car used for a particular scene speeds out of control. His spinal cord is crushed at the level of the fourth

lumbar spinal segment. Which of the following structures would most likely be spared from

destruction?

(A) Dorsal horn

(B) Ventral horn

(C) Lateral horn

(D) Gray matter

(E) Pia mater

13. A 24-year-old woman comes to a hospital to deliver her baby. Her obstetrician uses a caudal anesthesia during labor and childbirth to block the spinal nerves in the epidural space. Local anesthetic agents are most likely injected via which of the following openings?

(A) Intervertebral foramen

(B) Sacral hiatus

(C) Vertebral canal

(D) Dorsal sacral foramen

(E) Ventral sacral foramen

14. In a freak hunting accident, a 17-year-old boy was shot with an arrow that penetrated into his suboccipital triangle, injuring the suboccipital nerve between the vertebral artery and the posterior arch of the atlas. Which of the following muscles would be unaffected by such a lesion?

(A) Rectus capitis posterior major

(B) Semispinalis capitis

(C) Splenius capitis

(D) Obliquus capitis superior

(E) Obliquus capitis inferior

15. A 26-year-old heavyweight boxer was punched on his mandible, resulting in a slight

subluxation (dislocation) of the atlantoaxial joint. The consequence of the injury was

decreased range of motion at that joint. What movement would be most affected?

(A) Extension

(B) Flexion

(C) Abduction

(D) Adduction

(E) Rotation

16. A crush injury of the vertebral column can cause the spinal cord to swell. Which structure would be trapped between the dura and the vertebral body by the swelling spinal cord?

(A) Anterior longitudinal ligament

(B) Alar ligament

(C) Posterior longitudinal ligament

(D) Cruciform ligament

(E) Ligamentum nuchae

17. A 44-year-old woman comes to her physician and complains of headache and backache.

On examination, she is found to have fluid accumulated in the spinal epidural space because of damage to blood vessels or meninges. Which of the following structures is most likely ruptured?

(A) Vertebral artery

(B) Vertebral vein

(C) External vertebral venous plexus

(D) Internal vertebral venous plexus

(E) Lumbar cistern

18. A 69-year-old man has an abnormally increased curvature of the thoracic vertebral

column. Which of the following conditions is the most likely diagnosis?

(A) Lordosis

(B) Spina bifida occulta

(C) Meningocele

(D) Meningomyelocele

(E) Kyphosis

19. During a snowstorm, a 52-year-old man is brought to the emergency department after a

multiple car accident. Which of the following conditions is produced by a force that drives the trunk forward while the head lags behind in a rear-end automobile collision?

(A) Scoliosis

(B) Hangman fracture

(C) Meningomyelocele

(D) Whiplash injury

(E) Herniated disk

20. A 37-year-old man is brought to the emergency department with a crushed second

cervical vertebra (axis) that he suffered after a stack of pallets fell on him at work. Which of the following structures would be intact after the accident?

(A) Alar ligament

(B) Apical ligament

(C) Semispinalis cervicis muscle

(D) Rectus capitis posterior minor

(E) Obliquus capitis inferior

21. A middle-aged coal miner injures his back after an accidental explosion. His magnetic

resonance imaging (MRI) scan reveals that his spinal cord has shifted to the right because the lateral extensions of the pia mater were torn. Function of which of the following structures is most likely impaired?

(A) Filum terminale internum

(B) Coccygeal ligament

(C) Denticulate ligament

(D) Choroid plexus

(E) Tectorial membrane

22. A 25-year-old man with congenital abnormalities at birth has a lesion of the dorsal

scapular nerve, making him unable to adduct his scapula. Which of the following muscles is

most likely paralyzed?

(A) Semispinalis capitis

(B) Rhomboid major

(C) Multifidus

(D) Rotator longus

(E) Iliocostalis

23. After an automobile accident, a back muscle that forms the boundaries of the triangle of

auscultation and the lumbar triangle receives no blood. Which of the following muscles might be ischemic?

(A) Levator scapulae

(B) Rhomboid minor

(C) Latissimus dorsi

(D) Trapezius

(E) Splenius capitis

24. A 38-year-old woman with a long history of shoulder pain is admitted to a hospital for surgery. Which of the following muscles becomes ischemic soon after ligation of the superficial or ascending branch of the transverse cervical artery?

(A) Latissimus dorsi

(B) Multifidus

(C) Trapezius

(D) Rhomboid major

(E) Longissimus capitis

25. A 25-year-old soldier suffers a gunshot wound on the lower part of his back and is unable

to move his legs. A neurologic examination and magnetic resonance imaging (MRI) scan

reveal injury of the cauda equina. Which of the following is most likely damaged?

(A) Dorsal primary rami

(B) Ventral primary rami

(C) Dorsal roots of the thoracic spinal nerves

(D) Ventral roots of the sacral spinal nerves

(E) Lumbar spinal nerves

Questions 26 to 30: Choose the appropriate lettered structure in this magnetic resonance imaging (MRI) scan of the back (see Figure below).

26. When the internal vertebral venous plexus is ruptured, venous blood may spread into

which tissue and space?

27. Dorsal and ventral roots of the lower lumbar and sacral nerves are lacerated. Which

structure is most likely damaged?

28. The spinal cord is crushed at the level of the upper part of the first lumbar vertebra. Which structure is most likely damaged?

29. Which structure may herniate through the annulus fibrosus, thereby impinging on the

roots of the spinal nerve?

30. Cerebrospinal fluid (CSF) is produced by vascular choroid plexuses in the ventricles of

the brain and accumulated in which space?

31. A 48-year-old man goes to his physician because of pain and paresthesia along the lateral aspect of the leg and the dorsum of the foot. The patient’s symptoms suggest impingement of the L5 spinal nerve resulting from a herniated intervertebral disc. The L5 spinal nerve most likely exits between which of

the following vertebrae?

A. L3–L4 vertebrae

B. L4–L5 vertebrae

C. L5–S1 vertebrae

D. S1–S2 vertebrae

32. The muscles of the posterior aspect of the thigh, or hamstring musculature, are responsible for flexing the knee joint. Beginning with the motor neuron cell bodies in the gray matter of the spinal cord, identify the most likely pathway that axons would travel from the spinal cord to the hamstring muscles?

A. Ventral horn, ventral root, ventral ramus

B. Ventral horn, ventral root, dorsal ramus

C. Lateral horn, ventral root, ventral ramus

D. Lateral horn, dorsal root, dorsal ramus

E. Dorsal horn, dorsal root, ventral ramus

F. Dorsal horn, dorsal root, dorsal ramus

3. A 27-year-old man is brought to the emergency department after being involved in an automobile accident. Radiographic imaging studies indicate that he has sustained a fracture of the L1 vertebral arch and has a partially dislocated bone fragment impinging upon the underlying spinal cord. Which spinal cord level is most likely compressed by this bone fragment?

A. C1

B. L2

C. S3

D. T4

4. A 50-year-old man is diagnosed with flaccid paralysis limited to the right arm, without pain or paresthesias. No sensory deficits are noted. Laboratory studies reveal that the patient is infected with West Nile virus. The target that the virus has infected resulting in this patient’s symptoms is most likely the

A. Ventral horn of spinal cord gray matter

B. Ventral rami of spinal nerves

C. Dorsal horn of spinal cord gray matter

D. Dorsal rami of spinal nerves

5. A 6-year-old boy is stung by a wasp between his shoulder blades. Identify the pain sensation pathway the axons would travel to course from the skin of his back to the spinal cord.

A. Ventral horn, dorsal root, dorsal ramus

B. Ventral horn, dorsal root, ventral ramus

C. Ventral horn, ventral root, dorsal ramus

D. Ventral horn, ventral root, ventral ramus

E. Dorsal ramus, dorsal root, dorsal horn

F. Dorsal ramus, dorsal root, ventral horn

G. Dorsal ramus, ventral root, ventral horn

H. Dorsal ramus, ventral root, dorsal horn

6. Which of the following paired muscles of the back is primarily responsible for extension of the vertebral column?

A. Iliocostalis

B. Latissimus dorsi

C. Levator costarum

D. Rhomboid major and minor

E. Trapezius

7. A 44-year-old woman is suspected of having meningitis. To confirm the diagnosis, a lumbar puncture is ordered to collect a sample of the cerebrospinal fluid (CSF). Identify the last layer of tissue the needle will traverse in this procedure before reaching CSF.

A. Arachnoid mater

B. Dura mater

C. Ligamentum flavum

D. Pia mater

E. Skin

Answers with explanation

1. The Answer is D. Cerebrospinal fluid (CSF) is found in the subarachnoid space, which is a wide interval between the arachnoid layer and the pia mater. The epidural space contains the internal vertebral venous plexus and epidural fat. The subdural space between the arachnoid and the dura contains a little fluid to moisten the meningeal surface. The pia mater closely covers the spinal cord and enmeshes blood vessels on the surfaces of the spinal cord. Thus, the space between the spinal cord and the pia is a potential space.

2. The Answer is D. The space between the vertebral canal and the dura mater is the epidural

space, which contains the internal vertebral venous plexus. The spinal cord and blood vessels lie deep to the pia mater. The space between the arachnoid and dura maters is the subdural space, which contains a film of fluid. The subarachnoid space contains cerebrospinal fluid (CSF).

3. The Answer is D. All cervical spinal nerves exit through the intervertebral foramina above the corresponding vertebrae, except the eighth cervical nerves, which run inferior to the seventh cervical vertebra. All other spinal nerves exit the intervertebral foramina below the corresponding vertebrae. Therefore, the fifth cervical nerve passes between the fourth and fifth cervical vertebrae, and the fourth thoracic nerve runs between the fourth and fifth thoracic vertebrae.

4. The Answer is C. A posterolateral herniation of the intervertebral disk at disk level L 4 to L5 Affects the fifth lumbar nerve root but rarely affects the fourth lumbar nerve root because of a progressive descending obliquity of the fourth and fifth lumbar nerve roots. The first seven cervical nerves exit above the corresponding vertebra, and the eighth cervical nerve exits below the seventh cervical vertebra because there are eight cervical nerves but only seven cervical vertebrae. The rest of the spinal nerves exit below their corresponding vertebrae.

5. The Answer is C. Cerebrospinal fluid (CSF) is absorbed into the venous system primarily

through the arachnoid villi projecting into the cranial dural venous sinuses, particularly the

superior sagittal sinus. CSF is produced by the choroid plexuses of the ventricles of the brain and is circulated in the subarachnoid space, in which subarachnoid trabeculae are also found. The vertebral venous plexus and internal jugular vein are not involved in the absorption of CSF.

6. The Answer is B. The levator scapulae arise from the transverse processes of the upper cervical vertebrae and inserts on the medial border of the scapula. The other muscles are attached to the spinous processes of the vertebrae.

7. The Answer is D. The body of vertebra T4 articulates with the heads of the fourth and fifth ribs. The body of the T3 vertebra articulates with the head of the third and fourth ribs. The neck of a rib does not articulate with any part of the vertebra. The transverse process of the vertebra articulates with the tubercle of the corresponding rib. Therefore, the transverse process of vertebra T4 articulates with the tubercle of the fourth rib.

8. The Answer is C. Meningomyelocele is protrusion of the meninges and spinal cord through the unfused arch of the vertebra. A sufficient amount of folic acid during pregnancy is shown to prevent these kinds of neural tube defects. Spina bifida occulta is failure of the vertebral arch to fuse (only bony defect). Meningocele is protrusion of the meninges through the defective vertebral arch. Syringomyelocele is protrusion of the meninges and a pathologic tubular cavity in the spinal cord or brain.

9. The Answer is D. The dorsal primary rami of the spinal nerves innervate the deep muscles of the back, including the iliocostalis. The other muscles are the superficial muscles of the back, which are innervated by the ventral primary rami of the spinal nerves.

10. The Answer is B. The dorsal scapular nerve innervates the levator scapulae and rhomboid muscles, whereas the accessory nerve innervates the trapezius and sternocleidomastoid muscles. The serratus posterior superior is innervated by ventral primary rami of the spinal nerves, whereas the splenius cervicis and erector spinae are innervated by dorsal primary rami of the spinal nerves.

11. The Answer is D. The cerebrospinal fluid (CSF) is located in the subarachnoid space, between the arachnoid layer and the pia mater. In a lumbar puncture, the needle penetrates the skin, fascia, ligamentum flavum, epidural space, dura mater, subdural space, and arachnoid mater. The pia mater forms the internal boundary of the subarachnoid space; thus, it cannot be penetrated by needle. The posterior longitudinal ligament lies anterior to the spinal cord; thus, it is not penetrated by the needle. The filum terminale externum is the downward prolongation of the spinal dura mater from the second sacral vertebra to the dorsum of the coccyx. The annulus fibrosus consists of concentric layers of fibrous tissue and fibrocartilage surrounding and retaining the nucleus pulposus of the intervertebral disk, which lies anterior to the spinal cord.

12. The Answer is C. The lateral horns, which contain sympathetic preganglionic neuron cell bodies, are present between the first thoracic and second lumbar spinal cord levels (T1–L2). The lateral horns of the second, third, and fourth sacral spinal cord levels (S2–S4) contain parasympathetic preganglionic neuron cell bodies. The entire spinal cord is surrounded by the pia mater and has the dorsal horn, ventral horn, and gray matter. Note that the fourth lumbar spinal cord level is not the same as the fourth vertebral level.

13. The Answer is B. Caudal (epidural) anesthesia is used to block the spinal nerves in the epidural space by injecting local anesthetic agents via the sacral hiatus located between the sacral cornua. An intervertebral foramen transmits the dorsal and ventral primary rami of the spinal nerves. The vertebral canal accommodates the spinal cord. Dorsal and ventral sacral foramina transmit the dorsal and ventral primary rami of the sacral nerves.

14. The Answer is C. The splenius capitis is innervated by dorsal primary rami of the middle and lower cervical nerves. The suboccipital nerve (dorsal primary ramus of C1) supplies the muscles of the suboccipital area, including the rectus capitis posterior major, obliquus capitis superior and inferior, and the semispinalis capitis.

15. The Answer is E. The atlantoaxial joints are synovial joints that consist of two plane joints and one pivot joint and are involved primarily in rotation of the head. Other movements do not occur at this joint.

16. The Answer is C. The posterior longitudinal ligament interconnects the vertebral bodies and intervertebral disks posteriorly and runs anterior to the spinal cord within the vertebral canal. The ligamentum nuchae is formed by supraspinous ligaments that extend from the seventh cervical vertebra to the external occipital protuberance and crest. The anterior longitudinal ligament runs anterior to the vertebral bodies. The alar and cruciform ligaments also lie anterior to the spinal cord.

17. The Answer is D. The internal vertebral venous plexus is located in the spinal epidural space. The vertebral artery and vein occupy the transverse foramina of the upper six cervical vertebrae. The external vertebral venous plexus consists of the anterior part, which lies in front of the vertebral column, and the posterior part, which lies on the vertebral arch. The lumbar cistern is the enlargement of the subarachnoid space between the inferior end of the spinal cord and the inferior end of the subarachnoid space.

18. The Answer is E. Kyphosis (hunchback or humpback) is an abnormally increased thoracic curvature, usually resulting from osteoporosis. Lordosis is an abnormal accentuation of the lumbar curvature. Spina bifida occulta is failure of the vertebral arch to fuse (only bony defect). Meningocele is a protrusion of the meninges through the unfused arch of the vertebra, whereas meningomyelocele is a protrusion of the spinal cord and the meninges.

19. The Answer is D. Whiplash injury of the neck is produced by a force that drives the trunk forward while the head lags behind. Scoliosis is a lateral deviation resulting from unequal growth of the spinal column. Hangman fracture is a fracture of the neural arch through the pedicle of the axis that may occur as a result of hanging or motor vehicle accidents. Meningomyelocele is   a protrusion of the spinal cord and its meninges. A herniated disk compresses the spinal nerve roots when the nucleus pulposus is protruded through the annulus fibrosus.

20. The Answer is D. The rectus capitis posterior minor arises from the posterior tubercle of the atlas and inserts on the occipital bone below the inferior nuchal line. The alar ligament extends from the apex of the dens to the medial side of the occipital bone. The apical ligament extends from the dens of the axis to the anterior aspect of the foramen magnum of the occipital bone. The semispinalis cervicis arises from the transverse processes and inserts on the spinous processes. The obliquus capitis inferior originates from the spine of the axis and inserts on the transverse process of the atlas.

21. The Answer is C. The denticulate ligament is a lateral extension of the pia mater. The filum terminale (internum) is an inferior extension of the pia mater from the tip of the conus medullaris. The coccygeal ligament, which is also called the filum terminale externum or the filum of the dura, extends from the tip of the dural sac to the coccyx. The vascular choroid plexuses produce the cerebrospinal fluid (CSF) in the ventricles of the brain. The tectorial membrane is an upward extension of the posterior longitudinal ligaments from the body of the axis to the basilar part of the occipital bone.

22. The Answer is B. The rhomboid major is a superficial muscle of the back; is innervated by the dorsal scapular nerve, which arises from the ventral primary ramus of the fifth cervical nerve; and adducts the scapula. The semispinalis capitis, multifidus, rotator longus, and iliocostalis muscles are deep muscles of the back, are innervated by dorsal primary rami of the spinal nerves, and have no attachment to the scapula.

23. The Answer is C. The latissimus dorsi forms boundaries of the auscultation and lumbar triangles and receives blood from the thoracodorsal artery. The levator scapulae, rhomboid minor, and splenius capitis muscles do not form boundaries of these two triangles. The trapezius muscle forms a boundary of the auscultation triangle but not the lumbar triangle. The levator scapulae, rhomboid minor, and trapezius muscles receive blood from the transverse cervical artery. The splenius capitis muscle receives blood from the occipital and transverse cervical arteries.

24. The Answer is C. The trapezius receives blood from the superficial branch of the transverse cervical artery. The latissimus dorsi receives blood from the thoracodorsal artery. The rhomboid major receives blood from the deep or descending branch of the transverse cervical artery. The multifidus and longissimus capitis receive blood from the segmental arteries.

25. The Answer is D. The cauda equina is the collection of dorsal and ventral roots of the lower lumbar and sacral spinal nerves below the spinal cord. Dorsal and ventral primary rami and dorsal roots of the thoracic spinal nerves and lumbar spinal nerves do not participate in the formation of the cauda equina.

26. The Answer is E. Epidural fat is shown in the magnetic resonance imaging (MRI) scan. In addition, the internal vertebral venous plexus lies in the epidural space; thus, venous blood from the plexus may spread into epidural fat.

27. The Answer is C. The cauda equina is formed by a great lash of the dorsal and ventral roots of the lumbar and sacral nerves.

28. The Answer is B. The conus medullaris is a conical end of the spinal cord and terminates at the level of the L2 vertebra or the intervertebral disk between L1 and L2 vertebrae. A spinal cord injury at the level of the upper part of the first lumbar vertebra damages the conus medullaris.

29. The Answer is A. The intervertebral disk lies between the bodies of two vertebrae and consists of a central mucoid substance, the nucleus pulposus, and a surrounding fibrous tissue and fibrocartilage, the annulus fibrosus. The nucleus pulposus may herniate through the annulus fibrosus, thereby impinging on the roots of the spinal nerves.

30. The Answer is D. The cerebrospinal fluid (CSF) is found in the lumbar cistern, which is a

subarachnoid space in the lumbar area. CSF is produced by vascular choroid plexuses in the ventricles of the brain, circulated in the subarachnoid space, and filtered into the venous system through the arachnoid villi and arachnoid granulations.

31—C: Spinal nerves in the thoracic and lumbar vertebral region exit the vertebral canal below their associated vertebra. Therefore, the L5 spinal nerve exits below L5, between L5 and S1.

32—A: The ventral horn of the spinal cord gray matter houses motor neuron cell bodies and conveys motor neurons out through the ventral root into the spinal nerve. All muscles of the limbs and body wall are innervated by ventral rami. Although the muscles are present along the posterior aspect of the thigh,

muscles are still innervated by the ventral rami. Dorsal rami innervate the skin of the back and the deep back muscles, such as the erector spinae.

33—C: In an adult, the caudal end of the spinal cord is at the L1–L2 vertebral level. Therefore, a bone fragment from the L1 vertebra would have the potential of touching the caudal end of the spinal cord, not the L1 spinal cord level. C1, L2, and T4 are spinal cord levels superior to the fracture.

34—A: The patient has no sensory deficits and presents with only motor deficits. Therefore, the virus affects the ventral horn of the gray matter because that is the location of the motor neuron cell bodies.

35—E: All skin of the back is segmentally innervated by the dorsal rami branches of spinal nerves. Sensory information is then conducted through the dorsal root into the dorsal horn of the gray mater of the spinal cord.

36—A: The paired iliocostalis muscles, part of the erector spinae musculature, are postural muscles that help to extend the vertebral column and thus keep the spine erect. The latissimus dorsi, rhomboids, and trapezius muscles act primarily on the upper limb. The levator costarum muscles help to elevate the ribs during inspiration but will not extend the vertebral column.

37—A: A lumbar puncture collects cerebrospinal fluid and, therefore, the needle has to enter the subarachnoid space, which is located between the arachnoid and pia mater. Therefore, the last layer of tissue the needle would traverse to enter the subarachnoid space is the arachnoid mater.

Reference: 

1. BRS Gross anatomy.

2. Gross Anatomy: The Big Picture. 

3. High Yield Gross Anatomy.

4. Clinical Anatomy by Regions, Snell. 

5. Grays Anatomy .

6. LAST Anatomy