Shoulder, Back

Question 1

retract the scapula:

what 3 muscles do this?

what innervates them?

Answer 1

• 3 muscles retract the scapula: the levator scapulae, the rhomboid major, and the rhomboid minor.
  
  • The levator scapulae also helps elevate the scapula (hence the name).
• All innervated by the dorsal scapular nerve (C5)

Question 2

elevate the scapula:

What muscle? Innervated by what nerve?

Answer 2

• Levator scapulae elevates the scapula (also retracts scapula)
• Innervated by dorsal scapular nerve

Question 3

protract the scapula:

what muscle does this? What happens when can’t?

Answer 3

• serratus anterior = a protractor of the scapula
  
  • Innervated by long thoracic nerve. When lesioned, muscle is paralyzed, get winged scapula.

Question 4

what’s interesting about pectoralis major muscle?

Answer 4

• The pectoralis major muscle is the only muscle of the body innervated by all five spinal cord segments of the brachial plexus (insignificant but cool)
  
  • Innervated by both the medial pectoral nerve (C8 & T1) and the lateral pectoral nerve (C5-C7)

Question 5

latissumus dorsi

• innervation?
• actions?

Answer 5

• Innervated by thoracodorsal nerve (C6-C8)
• 3 actions:
  
  • Adducts the arm at the shoulder (glenohumeral) joint.
  • Medially rotates the arm at the shoulder (glenohumeral) joint.
  • Extends the arm at the shoulder (glenohumeral) joint.

Question 6

subscapularis muscle:

what does it do, and what two nerves innervate it?

Answer 6

• Medial rotator of arm at the shoulder
• Innervated by both the lower subscapular nerve and the upper subscapular nerve (C5,6, collateral nerves from posterior cord)
  
  • (The upper subscapular nerve only does that. Lower subscapular also innervates teres major.)

Question 7

rotator cuff:

What is it? What innervates it?

Answer 7

• The rotator cuff is a group of 4 muscles (SITS) that come together as tendons to form a covering around the head of the humerus.
• The rotator cuff attaches the humerus to the shoulder blade and helps to lift and rotate your arm.
  
  • The supraspinatus does first 15* of abduction, and the other three do rotation (SITS-AEEI)
• 3 of the 4 rotator cuff muscles are innervated by collateral nerves
  
  • The supraspinatus and infraspinatus are innervated by the suprascapular nerve.
  • The subscapularis is innervated by the upper and lower subscapular nerves.
  • The only rotator cuff muscle not innervated by a collateral nerve is the teres minor, which is innervated by the axillary nerve (a terminal nerve).
• Mnemonic: SITS-AEEI

Question 8

what are the 4 rotator cuff muscles

Answer 8

• Supraspinatus – Abduction
• Infraspinatus – External rotation
• Teres minor – External rotation
• Subscapularis – Internal rotation

Question 9

abduction of the arm

• What does first 15*?
• What takes over after?

Answer 9

• First 15* = supraspinatus (part of rotator cuff)
• Then deltoid takes over

Question 10

divisions of vertebral column

Answer 10

Question 11

how many vertebrae?

how many spinal nerves?

Answer 11

• 33 vertebrae, 31 spinal nerves

Question 12

where do cervical spinal nerves exit?

where do thoracic, lumbar, sacral, coccygeal spinal nerves exit?

Answer 12

• cervical exit above
• thoracic, lumbar, sacral, coccygeal exit below

Question 13

landmarks of vertebral column:

• conas medullaris
• cauda equina
• meninges
• filumn terminale

Answer 13

• conus medullaris = tapered end of the spinal cord, consisting of the sacral and coccygeal spinal cord segments. At L2.
• cauda equina = horse’s tail = the roots of the spinal nerves for the lower lumbar, sacral, and coccygeal spinal regions run together
• meninges = protective covering lining the inside of the spinal column, terminates at S2 and is anchored by the filum terminale to the first coccygeal vertebra.
• filum terminale = derivative from the meninges, anchors to coccygeal vertebra

Question 14

describe these vertebral structures

Answer 14

• Vertebrae are composed of:
  
  • vertebral body = weightbearing part of the bone
  • vertebral arch = contains various processes for articulating with other vertebrae and allowing muscles to move the vertebrae.
    
    • The arch originates from the body with two short pedicles, which each give off a transverse process that serves as an attachment point for muscles and—in the case of thoracic vertebrae—ribs.
    • The pedicles also give off laminae, which fuse in the midline to form a spinous process, another attachment point for muscles.
• Between the vertebral body and arch is the spinal canal, which contains the spinal cord, surrounded by meninges.
• superior and inferior articular processes connect to the vertebrae above and below, respectively, at zygapophyseal or facet joints (make back flexible)

Question 15

What connects vertebral bodies?

What is that structure made of?

Answer 15

• intervertebral discs
  
  • composed of rings of fibrocartilage (annulus fibrosus) surrounding a somewhat gelatinous center (nucleus pulposus, the only postnatal remnant of the notochord).

Question 16

which joints connect vertebral arches?

Answer 16

• The vertebral arches are connected by zygapophyseal aka facet joints.

Question 17

through what space do spinal nerves leave the vertebral column?

Answer 17

• intervertebral aka neural foramina
  
  • Enclosed between the superior and inferior vertebral notches of adjacent vertebrae

Question 18

how do cervical, thoracic, and lumbar vertebra look different?

Answer 18

• Cervical vertebrae
  
  • ​Have openings in their transverse processes called foramina transversaria that transmit the vertebral arteries, a major source of cerebral blood flow.
  • Have bifid (two-pronged) spinous processes, allowing for more attachment points for muscles to provide a larger and more precise range of motion in the neck
• Thoracic vertebrae
  
  • ​interdigitate with ribs; the end of the transverse process articulates with the tubercle of a rib.
• lumbar vertebrae
  
  • have very large vertebral bodies because they have the largest load of weight to support.
  • The load is transmitted across the sacroiliac joints to the pelvic bones, and down through bilateral femurs. Thus, once the responsibility of weight-bearing has been transmitted, the sacrum gets progressively narrower and the coccyx tapers down to nearly nothing.

Question 19

match statement with the type of vertebra:

• Openings in their transverse processes
• Large, wide vertebral bodies
• Bones articulating with their transverse processes
• Fusion with adjacent vertebrae

Answer 19

• Openings in their transverse processes –> cervical
• Large, wide vertebral bodies –> lumbar
• Bones articulating with their transverse processes –> thoracic
• Fusion with adjacent vertebrae –> sacrococcygeal

Question 20

what’s special about the atlas and axis vertebrae?

Answer 20

The top two vertebrae have additional special modifications:

• Atlas = C1
  
  • Just an anterior and posterior arch, NO vertebral body
  • Creates atlanto-occiptal“YES” joint with occipital bone of skull –> permits nodding
• Axis = C2
  
  • Has a body and the dens aka “odontoid process”, provides an axis of rotation.
    
    • Can think of it as a misplaced vertebral body of C1 that got stuck onto C2
  • the atlantoaxial aka “NO” joint, because it permits shaking-of-one’s-head-type motion.

Question 21

sacrum

• Which vertebrae and nerves?
• Why do the vertebrae get narrower?
• Where do nerves exit?

Answer 21

• S1-S5
• Narrow as transfer weight through sacroiliac joints
• the ventral and dorsal rami exit separately from the sacrum through anterior and posterior sacral foramina
  
  • (In contrast to the cervical, thoracic, and lumbar regions where a spinal nerve exits each intervertebral foramina)

Question 22

herniated intervertebral disc

• If L4-5 disc herniates, which nerve roots will be affected? L5-S1?

Answer 22

• relatively common in the lumbar region because it has the greatest weight-support role.
• When a disc herniates,the nucleus pulposus that protrudes posterolaterally.
• The lower spinal nerve is affected (in ex, L5, and S1)
  
  • for all but cervical vertebra, the spinal nerves exit below

Question 23

erector spinae muscles

• what are they? (3)
• action?
• what are they innervated by?

Answer 23

• Deep back muscles that act to extend vertebral column (superficial within deep muscles)
• I Love Spaghetti (lateral to medial)
  
  • iliocostalis
  • longissimus
  • spinalis
• innervated by dorsal rami of spinal nerves, which don’t have names

Question 24

transversospinalis muscles

• where?
• action?

Answer 24

• deepest layer of deep back muscles
• Small muscles that obliquely connect between
  
  • name bc they’re between the transverse/spinous processes of adjacent vertebrae.
• These muscles can also contribute to extension of the vertebral column, and are also rotators of the vertebrae, for a twisting motion.
• Don’t need to know their names (semispinalis, multifidus, levatores costarum, rotatores, and intertransversarius muscles)

Question 25

which bones form the pectoral girdle?

Answer 25

* **clavicle** - attaches to the manubrium of the sternum, and to the scapula * **scapula** = shoulder blade, suspends the **humerus**

Question 26

what are the important bumps on scapula? what are the two joints?

Answer 26

* Most prominent is the **long spine** across its posterior surface, which projects to form the **acromion** (process). * It is the **acromion that articulates with the clavicle to form the acromioclavicular joint**. * **coracoid process** = the attachment point for the pectoralis minor muscle. * **glenoid fossa** = the “socket” in which the “ball” of the humerus sits to form the **glenohumeral joint**. * Of note, the humeral head is significantly larger than the glenoid fossa in which it sits. We evolved to increase our range of motion in this joint by reducing how much the glenoid fossa surrounds the humeral head—but this comes with decreased stability of the joint, leaving us prone to injuries or dislocations at the glenohumeral joint.

Question 27

What are the movements of scapula? Which muscle contributes to motion on all axes?

Answer 27

* **trapezius** * Depending on which fibers are triggered, the trapezius can cause elevation (upper fibers), retraction (middle fibers), depression (lower fibers) of the scapula, lateral or medial rotation as well * innervated by spinal accessory nerve

Question 28

What is the most important muscle for moving the scapula?

Answer 28

* **trapezius** (superficial layer of back muscles) * large diamond-shaped muscle that inserts onto the spine of the scapula. * its fibers fan out to attach to the spinous processes of the vertebrae. * Depending on which fibers are triggered, the trapezius can cause **elevation** (upper fibers), **retraction** (middle fibers), **depression** (lower fibers) of the scapula, lateral or medial rotation * Innervated by the **spinal accessory nerve**

Question 29

intermediate back muscles - * What are they? * What do they do?

Answer 29

* **rhomboid major, rhomboid minor --\> retractors** and medial rotators * **levator scapulae which --\> elevation** of the scapula, medial rotation. * All three of these muscles are innervated by the **dorsal scapular nerve**.

Question 30

What muscles move the scapula? Innervation? * Elevation * Depression * Protraction * Retraction * Lateral rotation * Medial rotation

Answer 30

* Elevation - levator scapulae, trapezius * Depression - pec minor, trapezius, lat dorsi * Protraction - serratus anterior * Retraction - rhomboid major, rhomboid minor, trapezius * Lateral rotation - serratus anterior, trapezius * Medial rotation - rhomboid major and minor, levator scapulae * **Dorsal scapular nerve - rhomboids, levator scapulae** * Spinal accessory nerve - trapezius * Long thoracic nerve - serratus anterior * Medial pectoral nerve - pec minor

Question 31

which superficial back muscles act on the glenohumeral joint? Actions? Innervation?

Answer 31

* deltoid * **ABduct** arm at shoulder after 15 degrees _(supraspinatus does first 15)_ * **axillary nerve** * latissimus dorsi * **ADductor, extensor, medial rotator** of the humerus at the glenohumeral joint * **thoracodorsal nerve**

Question 32

which muscles of the rotator cuff rotate the humerus?

Answer 32

* **Infraspinatus** = lateral rotator * suprascapular nerve * **Teres minor** = lateral rotator * axillary nerve * **subscapularis** = medial rotator * subscapular nerve * Whereas supraspinatus = an abductor of the humerus at the glenohumeral joint, first 15. * suprascapular nerve * SItS

Question 33

What runs the quadrangular space?

Answer 33

* axillary nerve and posterior humeral circumflex artery * To supply teres minor and deltoid * formed by the borders of the teres minor and major, the lateral head of the triceps brachii, and the humerus

Question 34

movements at glenohumeral joint

Answer 34

Question 35

axial vs. appendicular skeleton

Answer 35

* The clavicle is also part of the appendicular skeleton, but it does connect to the axial skeleton through the sternoclavicular joints.

Question 36

Answer 36

## Footnote The answer is (D). The trapezius receives sensory innervation from the C3 and C4 ventral rami, but its somatic motor innervation is from the (spinal) accessory nerve, cranial nerve XI. (A)The levator scapulae is innervated by the dorsal scapular nerve. (B)The supraspinatus is innervated by the suprascapular nerve. (C)The teres minor is innervated by the axillary nerve. (D)(correct answer) (E)The iliocostalis muscles are innervated by dorsal rami.

Question 37

Answer 37

## Footnote The answer is (A). The foramina transversaria transmit the vertebral artery and are a feature of cervical vertebrae. (A)(correct answer) (B)This is predominantly a characteristic of lumbar vertebrae. (C)This is a feature of thoracic vertebrae. (D)There are eight cervical spinal nerves, but only seven cervical vertebrae. The C8 spinal nerve exits the spinal column between the C7 and T1 vertebrae. (E)This is a feature of sacrococcygeal vertebrae.

Question 38

Answer 38

## Footnote The answer is (D). The dorsal scapular nerve innervates the rhomboid major and minor muscles, and the levator scapulae. These are all retractors of the scapula. (A)The deltoid and supraspinatus are the main abductors of the humerus at the glenohumeral joint. They are innervated by the axillary and suprascapular nerves, respectively. (B)The main medial rotator of the humerus at the glenohumeral joint is the subscapularis, innervated by the upper and lower subscapular nerves. The latissimus dorsi and teres major, innervated by the thoracodorsal and lower subscapular nerves, respectively, also assist with medial rotation. (C)The main depressors of the scapula are the lower fibers of the trapezius, innervated by the (spinal) accessory nerve, and the pectoralis minor, innervated by the medial pectoral nerve. The latissimus dorsi also contributes. (D)Vertebral column extension is accomplished by the erector spinae and transversospinalis muscles, which are innervated by dorsal rami (similar name, but not the same thing).

Question 39

Answer 39

## Footnote The answer is (C). **The odontoid process or dens of C2 (the axis) articulates with the anterior arch of C1 (the atlas), forming part of the atlantoaxial joint.** (A)The C1–2 joint is the atlantoaxial joint, not C2–C3. (B)This is the atlanto-occipital joint. (C)(correct answer) (D)The dens (odontoid process) is a feature of C2, and it articulates with the anterior (not posterior) arch of C1. (E)There is no proper intervertebral disc between C1 and C2; the dens replaces the vertebral body of C1 without an intervertebral disc.

Question 40

Answer 40

## Footnote The answer is (E). **The supraspinatus is responsible for initiating abduction to about fifteen degrees.** The reproducible pain during that motion suggest a tear of the supraspinatus, which is a rather common injury. It is often associated with overuse, and may have been brought on in this patient when she picked back up a hobby that required her to keep her upper limb abducted for long periods of time. Supraspinatus tears may also be seen in athletes, trauma situations, and other occupational overuse. (A)The teres major extends, adducts, and medially rotates the humerus at the glenohumeral joint. (B)The teres minor laterally rotates the humerus at the glenohumeral joint. (C)The infraspinatus laterally rotates the humerus at the glenohumeral joint. (D)The subscapularis medially rotates the humerus at the glenohumeral joint. (E)(correct answer)

Question 41

Answer 41

## Footnote The answer is (B). This patient likely has an injury of the long thoracic nerve, which innervates the serratus anterior muscle. This is a major protractor of the scapula, explaining the complaint: it’s hard to reach out to grab objects when protraction is weakened. The clinical story is classic: radical mastectomies require removal of the tail of Spence, which extends into the axilla. The long thoracic nerve runs superficially on the serratus anterior, and is at risk during this surgery. To assess the patient clinically, winging will be observed when the therapist applies a retraction force to the patient. Why? Because the serratus anterior, which should contract to counteract this retraction force, fails to hold the scapula upon the body wall. Thus, while the serratus anterior causes protraction, the best way to assess it is to observe it failing to contract against a counteracting (retraction) force. Difficult question!

Question 42

what are 3 spinal ligaments?

Answer 42

* **Ligamentum Flavum** * In a lumbar puncture off the midline, the needle will traverse a ligamentum flavum instead of the supraspinous and interspinous ligaments and the intralaminar space. * **Anterior Longitudinal Ligament** * **Spondylitis** is an inflammation that results in addi- tional bone growth by osteophytes at the margins of the vertebral bodies. The anterior longitudinal ligament and the sacroiliac joints may undergo calcification. * **Posterior Longitudinal Ligament**

Question 43

* what is the AC joint? * which ligament supports it? * relation to shoulder trauma?

Answer 43

* AC joint = acromioclavicular joint - attach clavicle to acromion of scapula * acromioclavicular ligament * **resists subluxation of the acromion at the acromioclavicular joint**, which could result from shoulder trauma

Question 44

deltoid

Answer 44

* posterior and anterior fibers... so can do flex, exttension, lateral and medial rotation! * most important = abduction of arm beyond 15\*