Review Session

Anatomy

Of Back and Thorax

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 verte-brae. Which of the following spinal nerves may be damaged?(A) Fourth cervical and fourth thoracic nerves(B) Fifth cervical and fi fth thoracic nerves(C) Fourth cervical and fi fth thoracic nerves(D) Fifth cervical and fourth thoracic nerves(E) Third cervical and fourth thoracic nerves

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 fi fth cervical nerve passes between the fourth and fi fth cervical vertebrae, and the fourth thoracic nerve runs between the fourth and fi fth thoracic vertebrae.

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

Levator scapulae

Transverse processes of the upper 3 or 4 cervical vertebrae

Superior part of the medial border of the scapulaDorsal Scapular Nerve(C3-4)/Artery

Attachment

Rhomboids

Rhomboid major Spinous processes of the T2 to T5 vertebrae

Medial border of the scapula

Rhomboid minor Nuchal ligaments and spinous processes of C7–T1

Medial border of scapulaDorsal Scapular Nerve(C5)/Artery

• 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. 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

• The body of the T3 vertebra articulates with the head of the third and fourth ribs.

• The body of vertebra T4 articulates with the heads of the fourth and fifth 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. 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

• Failure of a portion of the neural tube to close, or reopening • Neural tube defects account for most CNS malformations • Causes: • Both genetic and environmental• Overall recurrence rate for a neural tube defect in subsequent

pregnancies: 4% - 5%. • Folate deficiency during the initial weeks of gestation (affect cell

division during critical periods) • Antenatal diagnosis: is based on imaging and the

screening of maternal blood samples for elevation of α-fetoprotein.

• Types:1. Encephalocele2. Spina bifida3. Myelomeningocele4. Anencephaly

NEURAL TUBE DEFECTS

Encephalocele

• Encephalocele is a diverticulum of malformed CNS tissue extending through a defect in the cranium.

• It most often occurs in the occipital region or in the posterior fossa

Spina bifida• A.k.a Spinal dysraphism

- severe malformation with a flattened, disorganized segment of spinal cord, associated with an overlying meningeal outpouching

• spina bifida occulta - asymptomatic bony defect

SPINA

BIFIDA

Myelomeningocele• a.k.a

meningomyelocele - extension of CNS tissue through a defect in the vertebral column;

• most common location - lumbosacral region

Anencephaly

• Malformation of the anterior end of the neural tube, with absence of the brain and calvarium

• Frog-like appearance of baby

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

• 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.

Peripheral Nervous System: Spinal Nerve

Dorsal rootlets

Ventral rootlets

Dorsal root

Dorsal root ganglion

Dorsal ramus

Ventral root

Ventral ramus

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The deep back muscles are grouped into superficial, intermediate, and deep layers according to their relationship to the surface.

Superficial Layer of Intrinsic Back Muscles

The splenius muscles are thick and flat and lie on the lateral and posterior aspects of the neck, covering the vertical muscles somewhat like a bandage, which explains their name (L. splenion = bandage).

Intermediate Layer of Intrinsic Back Muscles

The massive erector spinae is the chief extensor of the vertebral column and is divided into three columns: The iliocostalis forms the lateral column, the longissimus forms the intermediate column, and the spinalis forms the medial column.

Each column is divided regionally into three parts according to the superior attachments (e.g., iliocostalis lumborum, iliocostalis thoracis, and iliocostalis cervicis).

Deep Layer of Intrinsic Back Muscles

Deep to the erector spinae is an obliquely disposed group of much shorter muscles called the transversospinal muscle group (transversospinalis), consisting of the semispinalis, multifidus, and rotatores.

These muscles originate from transverse processes of vertebrae and pass to spinous processes of more superior vertebrae.

They occupy the trench between the transverse and the spinous processes and are attached to these processes, the laminae between them, and the ligaments linking them together.

Peripheral Nervous System: Somatic NS

Dorsal rami:● motor and sensory innervation to epaxial muscles and overlying skin● strictly segmental

Exception: Greater occipital n. (C2 dorsal ramus; pure sensory)

Example: Iliocostalis

C5-L3 myotomes

C5-L3 dorsal rami

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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

• 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 fi brous tissue and fi brocartilage surrounding and retaining the nucleus pulposus of the intervertebral disk, which lies anterior to the spinal cord.

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

• The filum terminale (internum) is an inferior extension of the pia mater from the tip of the conus medullaris.

• The denticulate ligament is a lateral extension of the pia mater

• The coccygeal ligament, which is also called the fi lum 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.

After an automobile accident, a back

muscle that forms the boundaries of the tri-

angle of auscultation and the lumbar trian-

gle 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

• The levator scapulae, rhomboid minor, and splenius capitis muscles do not form boundaries of these two triangles.

• The latissimus dorsi forms boundaries of the auscultation and lumbar triangles and receives blood from the thoracodorsal artery.

• 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.

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) Multifi dus(C) Trapezius(D) Rhomboid major(E) Longissimus capitis

• The rhomboid major - deep or descending branch of the transverse cervical artery.

• The multifidus and longissimus capitis - segmental arteries.

• The trapezius - superficial branch of the transverse cervical artery.

• The latissimus dorsi - thoracodorsal artery.

A 35-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

• 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.

• Choose the appropriate lettered structure in this magnetic resonance imaging (MRI) scan of the back

• When the internal vertebral venous plexus is ruptured, venous blood may spread into which tissue and space?

• 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.

• Dorsal and ventral roots of the lower lumbar and sacral nerves are lacerated. Which structure is most likely damaged?

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

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

• 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.

• Which structure may herniate through the annulus fibrosus, thereby impinging on the roots of the spinal nerve?

• 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.

• Cerebrospinal fl uid (CSF) is produced by vascular choroid plexuses in the ventricles of the brain and accumulated in which space?

• 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.

A 43-year-old female patient has been

lying down on the hospital bed for more

than 4 months. Her normal, quiet expiration

is achieved by contraction of which of the

following structures?

(A) Elastic tissue in the lungs and thoracic wall

(B) Serratus posterior superior muscles

(C) Pectoralis minor muscles

(D) Serratus anterior muscles

(E) Diaphragm

• Inspiration:

Forced: the diaphragm; external, internal (interchondral part), and innermost intercostal; sternocleidomastoid; levator costarum; serratus anterior; scalenus; pectoralis major and minor; and serratus posterior superior muscles.

Quiet: results from contraction of the diaphragm

• Expiration

Forced: muscles of the anterior abdominal wall, internal intercostal (costal part) muscles, and serratus posterior inferior muscles.

Quiet: elastic recoil of the lungs

A 17-year-old boy was involved in a gang fight, and a stab wound severed the white rami communicantes at the level of his sixth thoracic vertebra. This injury would result in degeneration of nerve cell bodies in which of the following structures?

(A) Dorsal root ganglion and anterior horn of the spinal cord(B) Sympathetic chain ganglion and dorsal root ganglion(C) Sympathetic chain ganglion and poste-rior horn of the spinal cord(D) Dorsal root ganglion and lateral horn of the spinal cord(E) Anterior and lateral horns of the spinal cord

Sympathetic paravertebral ganglion: bypass, no synapse!

Dorsal horn of spinal cord(synapse on fiber tracts to the brain)

from body wall in spinal nerves

cell bodies

from body cavities in splanchnic nn.

DRG

gray ramus communicans

white ramus communicans

Peripheral Nervous System: Visceral Sensation

52

Rami Communicantes White Rami Communicantes• ■ Contain preganglionic sympathetic GVE

(myelinated) fibers with cell bodies located in the lateral horn (intermediolateral cell column) of the spinal cord and GVA fibers with cell bodies located in the dorsal root ganglia

• ■ connected to spinal nerves only between T1 and L2

Gray Rami Communicantes• ■ Contain postganglionic sympathetic GVE

(unmyelinated) fibers that supply the blood vessels, sweat glands, and arrector pili muscles of hair follicles.

• ■ Are connected to every spinal nerve and contain fibers with cell bodies located in the sympathetic trunk.

• The white rami communicantes contain preganglionic sympathetic GVE fibers and GVA fibers whose cell bodies are located in the lateral horn of the spinal cord and the dorsal root ganglia.

• The sympathetic chain ganglion contains cell bodies of the postganglionic sympathetic nerve fibers.

• The anterior horn of the spinal cord contains cell bodies of the GSE fi bers.

• The dorsal root ganglion contains cell bodies of GSA and GVA fibers.

A 27-year-old cardiac patient with an irregular heartbeat visits her doctor’s office for examination. Where should the physician place the stethoscope to listen to the sound of the mitral valve?

(A) Over the medial end of the second left intercostal space

(B) Over the medial end of the second right intercostal space

(C) In the left fourth intercostal space at the midclavicular line

(D) In the left fifth intercostal space at the midclavicular line

(E) Over the right half of the lower end of the body of the sternum

• Mitral valve - the left fifth intercostal space at the midclavicular line.

• Pulmonary valve the medial end of the second left intercostal space,

• Aortic valve is most audible over the medial end of the second right intercostal space

• Tricuspid valve is most audible over the right half of the lower end of the body of the sternum.

A 37-year-old patient with palpitation was examined by her physician, and one of the diagnostic records included a posterior–anterior chest radiograph. Which of the following comprises the largest portion of the sternocostal surface of the heart seen on the radiograph?

(A) Left atrium(B) Right atrium(C) Left ventricle(D) Right ventricle(E) Base of the heart

•The right ventricle forms a large part of the sternocostal surface of the heart. •The left atrium occupies almost the entire posterior surface of the right atrium. •The right atrium occupies the right aspect of the heart. The left ventricle lies at the back of the heart and bulges roundly to the left. •The base of the heart is formed by the atria, which lie mainly behind the ventricles.

The bronchogram of a 45-year-old female smoker shows the presence of a tumor in the eparterial bronchus. Which airway is most likely blocked?

(A) Left superior bronchus

(B) Left inferior bronchus

(C) Right superior bronchus

(D) Right middle bronchus

(E) Right inferior bronchus

The eparterial bronchus is the right superior lobar (secondary) bronchus; all of the other bronchi are hyparterial bronchi.

A 44-year-old man with a stab wound was brought to the emergency department, and a physician found that the patient was suffering from a laceration of his right phrenic nerve. Which of the following conditions has likely occurred?

(A) Injury to only GSE fibers(B) Difficulty in expiration(C) Loss of sensation in the fibrous pericardium

and mediastinal pleura(D) Normal function of the diaphragm(E) Loss of sensation in the costal part of the diaphragm

Superior Mediastinum: Phrenic nerve R. phrenic n. in superior mediastinum…

● lies lateral to R. vagus n.● descends along right side of R. brachiocephalic v. and SVC● is anterior to root of right lung L. phrenic n. in superior mediastinum… lies lateral and superficial to L. vagus n. descends along left side of aortic arch superficial to L. superior intercostal v. is anterior to root of left lung R. + L. phrenic nn….

▪ originate from C3-C5 spinal cord segments

▪ carry…somatic motor fibers (to

diaphragm)post-ganglionic

sympathetic fibers sensory fibers

• The phrenic nerve supplies the pericardium and mediastinal and diaphragmatic (central part) pleura and the diaphragm, an important muscle of inspiration.

• It contains general somatic efferent (GSE), general somatic afferent (GSA), and GVE (post-

ganglionic sympathetic) fibers.

• The costal part of the diaphragm receives GSA fibers from the intercostal nerves.

A 75-year-old patient has been suffering

from lung cancer located near the cardiac

notch, a deep indentation on the lung. Which of

the following lobes is most likely to be excised?

(A) Superior lobe of the right lung

(B) Middle lobe of the right lung

(C) Inferior lobe of the right lung

(D) Superior lobe of the left lung

(E) Inferior lobe of the left lung

Left Lung

Smaller than right lung

Oblique fissure… separates superior and inferior lobes

Superior lobe: largest surface touches upper part of a-l

thoracic wall

apex projects into cervical root

Inferior lobe:● costal surface touches posterior and inferior

thoracic walls

Heart projects into medial surface

Lingula = tongue-like extension of superior lobe on anterior surface

Superior lobe

Oblique fissure

Inferior lobe

Lingula65

• The cardiac notch is a deep indentation of the anterior border of the superior lobe of the left lung. Therefore, the right lung is not involved.

A thoracentesis is performed to aspirate an abnormal accumulation of fluid in a 37-year-old patient with pleural effusion. A needle should be inserted at the midaxillary line between which of the following two ribs so as to avoid puncturing the lung?(A) Ribs 1 and 3(B) Ribs 3 and 5(C) Ribs 5 and 7(D) Ribs 7 and 9(E) Ribs 9 and 11

Pleural Cavities

On either side of mediastinum

Surround the lungs

Borders and extensions:

● superior: extend above rib 1 into root of neck

● inferior: extend to a level just above costal margin

● medial: mediastinum

Parietal pleura

Visceral pleuraPleural cavity

Rib 1

Right lung

Mediastinum Left lung69

• A thoracentesis is performed for aspiration of fluid in the pleural cavity at or posterior to the midaxillary line one or two intercostal spaces below the fl uid level but not below the ninth intercostal space and, therefore, between ribs 7 and 9.

A 75-year-old woman was admitted to a

local hospital, and bronchograms and radio-

graphs revealed a lung carcinoma in her left lung. Which of the following structures or char-

acteristics does the cancerous lung contain?

• (A) Horizontal fissure

• (B) Groove for superior vena cava (SVC)

• (C) Middle lobe

• (D) Lingula

• (E) Larger capacity than the right

Right LungSuperior lobe

Oblique fissure

Lingula72

Left Lung

Superior lobe

Middle lobe

Inferior lobe

Horizontal fissure

Oblique fissure

72

Inferior lobe

The lingula is the tongue-shaped portion of the upper lobe of the left lung. The right lung has a groove for the horizontal fi ssure, superior vena cava (SVC), and middle lobe and has a larger capacity than the left lung.