Gross Anatomy: Shoulder Muscles, Back Musculature, and Spinal Column & Joints

Comprehensive review flashcards covering shoulder muscles, extrinsic and intrinsic back musculature, joints, vertebral column kinematics, ligaments, and spinal nerve anatomy.

What are the three main functional muscle blocks of the shoulder?

1. Thoracoscapular muscles (originate on thorax, neck, and head; insert on scapula and clavicle; move scapula on thorax)
2. Thoracohumeral muscles (originate on thorax; insert on humerus; move humerus at GHJ)
3. Scapulohumeral muscles (originate on scapula and clavicle; insert on humerus; move humerus at GHJ)

What are the attachment and actions of pectoralis minor on the scapula?

Insertion: Coracoid process of the scapula Actions: Protraction and depression of the scapula (fixes the scapula on the body wall)

What are the attachment, innervation, and primary actions of the serratus anterior?

Insertion: Medial border of the scapula Innervation: Long thoracic nerve Actions: Protraction and upward rotation of the scapula (fixes the scapula on the body wall, working in synergy with the trapezius)

What condition and nerve deficit is demonstrated by the scapular abnormal protrusion shown here?

Winged scapula caused by damage to the long thoracic nerve, leading to paralysis of the serratus anterior muscle.

What are the insertion and humeral actions of pectoralis major?

Insertion: Intertubercular groove of the humerus Actions: Adduction, internal rotation, and flexion of the humerus at the glenohumeral joint

What are the insertion and humeral actions of latissimus dorsi?

Insertion: Intertubercular groove of the humerus Actions: Adduction, internal rotation, and extension of the humerus at the glenohumeral joint

What are the origins, insertion, and innervation of the deltoid muscle?

Origins: Clavicle, scapular spine, and acromion process Insertion: Deltoid tuberosity of the humerus Innervation: Axillary nerve

What are the actions associated with the anterior, middle, and posterior parts of the deltoid?

Anterior (A): Flexion and internal rotation Middle (M): Abduction of the humerus (after the initial $15^\circ$) Posterior (P): Extension and external rotation

How are the motor and sensory functions of the axillary nerve clinically evaluated?

Motor test: Have the patient abduct the arm past $15^\circ$ Sensory test: Touch the skin over the lateral shoulder patch

What are the attachments, actions, and innervation of teres major?

Origin: Lateral border of the scapula Insertion: Intertubercular groove of the humerus Actions: Adduction and internal rotation of the glenohumeral joint Innervation: Lower subscapular nerve

Which four muscles comprise the rotator cuff (SITS) and what is their primary function?

Supraspinatus, Infraspinatus, Teres minor, and Subscapularis. Primary function: Stabilize the glenohumeral joint by holding the head of the humerus in the glenoid fossa.

What are the origin, insertion, action, and innervation of supraspinatus?

Origin: Supraspinous fossa Insertion: Greater tubercle of the humerus Action: Abduction of the glenohumeral joint for the initial $15^\circ$ Innervation: Suprascapular nerve

What are the origin, insertion, action, and innervation of infraspinatus?

Origin: Infraspinous fossa Insertion: Greater tubercle of the humerus Action: External rotation of the glenohumeral joint Innervation: Suprascapular nerve

What are the origin, insertion, action, and innervation of teres minor?

Origin: Lateral border of the scapula Insertion: Greater tubercle of the humerus Action: External rotation of the glenohumeral joint Innervation: Axillary nerve

What are the origin, insertion, actions, and innervation of subscapularis?

Origin: Subscapular fossa Insertion: Lesser tubercle of the humerus Actions: Internal rotation and adduction of the glenohumeral joint Innervation: Upper and lower subscapular nerves

Which five muscles produce internal (medial) rotation of the glenohumeral joint, and what are their nerves?

1. Subscapularis (upper and lower subscapular nn.)
2. Teres major (lower subscapular n.)
3. Deltoid (axillary n.)
4. Pectoralis major (medial and lateral pectoral nn.)
5. Latissimus dorsi (thoracodorsal n.)

What are the borders and contents of the quadrangular space?

Borders: Teres minor, teres major, humerus, and long head of triceps brachii Contents: Axillary nerve and posterior circumflex humeral artery and vein

What are the borders and contents of the triangular space?

Borders: Teres minor, teres major, and long head of triceps brachii Contents: Circumflex scapular artery and vein

A patient suffers a blockage in the dorsal scapular artery. Which muscles are most likely affected?

Rhomboid major, rhomboid minor, and levator scapulae (which receive blood supply from the deep branch of the transverse cervical artery / dorsal scapular artery).

How are the muscles of the back classified into functional layers, and what are their motor targets?

1. Superficial group (extrinsic): Move the upper extremity
2. Middle group (extrinsic): Move the thoracic cage
3. Deep group (intrinsic): Move the vertebral column

What nerve innervates the superficial back muscles?

Branches of the brachial plexus (ventral rami), EXCEPT the trapezius, which is innervated by the spinal accessory nerve (CN XI).

What are the attachments of the trapezius muscle?

Origin: Occipital bone, nuchal ligament, and vertebral spinous processes Insertion: Spine of the scapula, acromion process, and distal clavicle

What ligament is depicted here, what are its bony attachments, and what is its primary function?

Nuchal ligament; attaches to the external occipital protuberance, cervical spinous processes, and vertebra prominens ($\text{C7}$); serves as an origin for the trapezius and prevents hyperflexion of the neck.

What actions does the trapezius exert on the scapula and the head/neck?

On scapula: Elevation, depression, retraction, and upward (lateral) rotation On head/neck: Unilateral lateral flexion (ear to shoulder) and bilateral extension (bending head posteriorly)

What are the origins and innervation of the latissimus dorsi?

Origins: Middle and lower vertebral spinous processes, iliac crest, and thoracolumbar fascia/lumbar aponeurosis Innervation: Thoracodorsal nerve

What are the attachments, innervation, and actions of the rhomboid major and minor?

Origin: Vertebral spinous processes (lower C and upper T) Insertion: Vertebral (medial) border of the scapula Innervation: Dorsal scapular nerve Actions: Elevation, retraction, and downward rotation of the scapula

What are the attachments, innervation, and actions of levator scapulae?

Origin: Transverse processes of upper cervical vertebrae Insertion: Superior angle of the scapula Innervation: Dorsal scapular nerve Actions: Elevation and downward rotation of the scapula

What anatomical space is being auscultated with a stethoscope in this image?

The triangle of auscultation (a thinning of musculature on the back ideal for listening to thoracic sounds).

What are the locations and actions of the middle back muscles (serratus posterior superior and inferior)?

Serratus posterior superior: Deep to rhomboids; originates on spinous processes, inserts on ribs, and elevates upper ribs. Serratus posterior inferior: Deep to latissimus dorsi; originates on spinous processes, inserts on ribs, and depresses lower ribs.

What nerve branch innervates the deep (intrinsic) muscles of the back?

Dorsal rami of spinal nerves.

What are the attachments and actions of the splenius muscles (superficial layer of deep back muscles)?

Splenius capitis and cervicis. Origin: Spinous processes of lower C and upper T vertebrae Insertions: Mastoid process (capitis) and upper C transverse processes (cervicis) Actions: Bilateral extension of the neck; unilateral ipsilateral lateral flexion and rotation

What are the three columns of the erector spinae group from lateral to medial, and their actions?

From lateral to medial: Iliocostalis, Longissimus, and Spinalis. Common origin: Iliac crest, sacrum, and lumbar fascia. Actions: Bilateral extension of the vertebral column; unilateral ipsilateral lateral flexion and rotation.

What muscles comprise the transversospinalis group, and what are their primary actions?

Multifidus and Semispinalis (including semispinalis capitis, cervicis, and thoracis). Actions: Bilateral extension of the vertebral column; unilateral ipsilateral lateral flexion; and contralateral rotation (pulls spinous processes toward transverse processes).

What are the primary vs. secondary vertebral curvatures of the adult spine?

Primary curvatures: Kyphoses (concave toward the front / anteriorly) - Thoracic and Sacral (born with 1 kyphosis). Secondary curvatures: Lordoses (concave toward the back / posteriorly) - Cervical and Lumbar.

What abnormal spinal curvature is illustrated in this diagram?

Scoliosis (an abnormal lateral curvature of the spinal column).

What are the three structural classifications of joints in the human body?

1. Fibrous joints (collagen fibers bind bones; no joint cavity)
2. Cartilaginous joints (cartilage binds bones; no joint cavity)
3. Synovial joints (joint cavity separates bones; held by an external joint capsule)

What specific type of fibrous joint is illustrated by the ligamentous connection between the distal tibia and fibula?

Syndesmosis (a fibrous joint held together by a ligament where fibrous tissue is longer than in sutures).

What type of fibrous joint is shown here anchoring a tooth root in its alveolar socket?

Gomphosis (a 'peg in socket' fibrous joint where the periodontal ligament holds the tooth in the alveolar socket).

What type of cartilaginous joint is depicted in both the intervertebral disc and pubic symphysis?

Symphysis (plural: symphyses; a cartilaginous joint where bones are united by fibrocartilage).

How do synchondroses differ structurally from symphyses?

Synchondroses unite bones with hyaline cartilage (e.g., epiphyseal plates, first sternocostal joint). Symphyses unite bones with fibrocartilage (e.g., intervertebral discs, pubic symphysis).

What are the essential structural components of a synovial joint?

1. Joint capsule (composed of an outer fibrous capsule and inner synovial membrane)
2. Articular cartilage (hyaline cartilage covering bone ends)
3. Joint cavity
4. Synovial fluid (secreted by the synovial membrane)

What are the two major parts of an intervertebral (IV) disc?

1. Anulus fibrosus: Outer ring of fibrocartilage arranged in concentric circular layers
2. Nucleus pulposus: Central elastic, semifluid, cartilage-like ball

Where are the anterior and posterior longitudinal ligaments located, and during which movement is each pulled tightest?

Anterior longitudinal ligament: Runs longitudinally along the anterior aspect of vertebral bodies; pulled tightest during extension. Posterior longitudinal ligament: Runs along the posterior aspect of vertebral bodies inside the vertebral canal; pulled tightest during flexion.

What are zygapophyseal joints and interspinous joints?

Zygapophyseal joints: Synovial joints between superior and inferior articular facets (zygapophyses) of adjacent vertebrae. Interspinous joints: Fibrous syndesmoses connecting adjacent spinous processes.

What head movements occur at the atlanto-occipital vs. atlanto-axial joints?

Atlanto-occipital joints (between occipital condyles and C1 atlas): 'YES' movement (flexion/extension of the head). Atlanto-axial joints (between C1 atlas and C2 axis): 'NO' movement (rotation of the head).

What characterizes the ligamentum flavum, and why is it named 'flavum'?

The ligamentum flavum connects the laminae of adjacent vertebrae; it contains high amounts of elastic fibers that give it a distinctive yellow appearance ('flavum' = yellow).

How do the orientations of zygapophyseal articular facets differ across cervical, thoracic, and lumbar regions?

Cervical facets face superiorly/inferiorly: Allow flexion/extension, lateral flexion, and rotation. Thoracic facets face posteriorly/anteriorly: Allow rotation; restrict flexion/extension and lateral flexion. Lumbar facets face medially/laterally: Restrict rotation, flexion/extension, and lateral flexion.

What are the two types of costal joints, and what ligament stabilizes the head of the rib?

Costovertebral joint (head of rib articulating with vertebral bodies) and Costotransverse joint (tubercle of rib articulating with transverse process); both are synovial joints. The radiate ligament strengthens and stabilizes the costovertebral joint at the head of the rib.

What is the pathological mechanism of a herniated ('slipped') disc, and why does it typically occur during lumbar hyperflexion?

Bending at the waist under a heavy load causes compression that forces the nucleus pulposus posteriorly through the anulus fibrosus, impinging exiting spinal nerves.

How many total pairs of spinal nerves are present in humans, broken down by region?

31 total pairs:

• 8 cervical pairs
• 12 thoracic pairs
• 5 lumbar pairs
• 5 sacral pairs
• 1 coccygeal pair

At what vertebral level does the adult spinal cord typically terminate, and what structures continue inferiorly?

The spinal cord ends as the conus medullaris at approximately the $\text{L2}$ vertebral level; it continues inferiorly as the cauda equina and filum terminale.

What are the functional destinations of dorsal rami versus ventral rami of spinal nerves?

Dorsal rami: Supply motor innervation to intrinsic (deep) back muscles and sensory innervation to the skin of the back. Ventral rami: Form plexuses and supply the upper and lower limbs and the anterolateral body wall.