Exam 2: Modules 3, 4, and 5 - Head, Neck, Shoulder, Upper Extremity, and Brachial Plexus Anatomy

Comprehensive flashcards covering head and facial expression muscles, mastication muscles, cervical and suboccipital musculature, rotator cuff and scapular biomechanics, arm/forearm compartments, intrinsic hand muscles, brachial plexus anatomy, and upper extremity neurovascular pathways.

What are the two primary functions of the muscles of facial expression?

1) Move the skin and change facial expressions to convey mood; 2) Attach to bone or fascia by pulling on skin.

What are the origin, insertion, and main actions of the frontal belly of the occipitofrontalis?

Origin: Epicranial aponeurosis. Insertion: Skin and subcutaneous tissue of eyebrows and forehead. Main Actions: Elevates eyebrow and wrinkles skin of forehead; protracts scalp (expressing surprise and curiosity).

What are the origin, insertion, and main actions of the occipital belly of the occipitofrontalis?

Origin: Lateral $2/3\text{rds}$ of superior nuchal line. Insertion: Epicranial aponeurosis. Main Actions: Retracts scalp; increases effectiveness of frontal belly.

Identify the muscle highlighted in green and state its origin, insertion, and actions.

Corrugator supercilii. Origin: Medial end of superciliary arch. Insertion: Skin superior to middle of supraorbital margin and superciliary arch. Main Actions: Draws eyebrows medial and inferiorly, creating vertical wrinkles above nose (expressing concern or worry).

Identify the muscle highlighted in green and describe its attachments and main actions.

Procerus. Origin: Fascia covering nasal bone and lateral nasal cartilage. Insertion: Skin of inferior forehead, between eyebrows. Main Actions: Depresses medial end of eyebrow; wrinkles skin over dorsum of nose (expressing disdain or dislike).

Identify the muscle highlighted in green, along with its attachments and main actions.

Nasalis. Origin: Frontal process of maxilla. Insertion: Major alar cartilage; lateral part of skin of upper lip. Main Actions: Depresses ala laterally, dilating anterior nasal aperture ("flaring nostrils"), helps to elevate upper lip.

Identify the muscle highlighted in green and explain how its palpebral and orbital parts differ in action.

Orbicularis oculi. Its main action is closing eyelids: the palpebral part closes the eyelids gently, while the orbital part closes the eyelids tightly (such as in winking).

If a patient presenting with Bell's palsy experiences slow recovery in the orbital part of the orbicularis oculi, which specific function is most likely limited?

Closing eyelid tightly.

Identify the muscle highlighted in green and state its attachments and main actions.

Orbicularis oris. Origin: Medial maxilla and mandible; deep surface of peri-oral skin; angle of mouth. Insertion: Mucous membrane of lips. Main Actions: Tonus closes oral fissure; phasic contraction compresses and protrudes lips (kissing) or resists distension (when blowing).

Identify the muscle highlighted in green and state its attachments and actions.

Buccinator. Origin: Mandible, alveolar process of maxilla and alveolar part of mandible, pterygomandibular raphe. Insertion: Angle of mouth (modiolus); orbicularis oris. Main Actions: Presses cheek against molar teeth; works with tongue to keep food between occlusal surfaces and out of oral vestibule; resists distension (when blowing).

Identify the muscle highlighted in green and state its origin, insertion, and action.

Risorius. Origin: Parotid fascia and buccal skin (highly variable). Insertion: Angle of mouth (modiolus); orbicularis oris. Main Actions: Part of dilators of mouth; depresses labial commissure bilaterally to frown (expressing sadness).

Identify the muscle highlighted in green and differentiate its bilateral vs. unilateral action.

Zygomaticus major. Origin: Lateral aspect of zygomatic bone. Insertion: Angle of mouth (modiolus). Main Actions: Part of dilators of mouth; elevates labial commissure bilaterally to smile (happiness) and unilaterally to sneer (disdain).

Identify the muscle highlighted in green and describe its attachments and emotional expression.

Zygomaticus minor. Origin: Anterior aspect of zygomatic bone. Insertion: Skin of upper lip. Main Actions: Part of dilators of mouth; retracts (elevates) and/or everts upper lip; deepens nasolabial sulcus (showing sadness).

Identify the muscle highlighted in green and state its origin and actions.

Levator labii superioris. Origin: Infra-orbital margin (maxilla). Insertion: Skin of upper lip. Main Actions: Part of dilators of mouth; retracts (elevates) and/or everts upper lip; deepens nasolabial sulcus (showing sadness).

Identify the muscle highlighted in green and state its origin, insertion, and action.

Levator anguli oris. Origin: Infra-orbital maxilla (canine fossa). Insertion: Angle of mouth (modiolus). Main Actions: Part of dilators of mouth; widens oral fissure (grinning or grimacing).

Identify the muscle highlighted in green and state its origin and actions.

Depressor labii inferioris. Origin: Platysma and anterolateral body of mandible. Insertion: Skin of lower lip. Main Actions: Part of dilators of mouth; retracts (depresses) and/or everts lower lip.

Identify the muscle highlighted in green and state its attachments and actions.

Depressor anguli oris. Origin: Anterolateral base of mandible. Insertion: Angle of mouth (modiolus). Main Actions: Part of dilators of mouth; depresses labial commissure bilaterally to frown (sadness).

Identify the muscle highlighted in green and state its origin, insertion, and action.

Mentalis. Origin: Body of mandible (anterior roots of inferior incisors). Insertion: Skin of chin (mentolabial sulcus). Main Actions: Elevates and protrudes lower lip; elevates skin of chin (showing doubt).

Identify the superficial neck muscle highlighted in green and state its attachments and actions.

Platysma. Origin: Subcutaneous tissue of infraclavicular and supraclavicular regions. Insertion: Base of mandible; skin of cheek and lower lip; angle of mouth; orbicularis oris. Main Actions: Depresses mandible (against resistance); tenses skin of inferior face and neck (conveying tension and stress).

Which cranial nerve provides motor innervation to all the muscles of facial expression?

Facial nerve ($CN\ VII$).

Which nerve innervates all muscles of mastication?

Trigeminal nerve ($CN\ V$), mandibular branch.

Identify the muscle of mastication highlighted in green and describe its attachments and actions.

Temporalis. Attachments: Triangular muscle with broad attachment to floor of temporal fossa and deep surface of temporal fascia. Actions: Elevates mandible, closing jaws; posterior, more horizontal fibers are primary retractors of mandible (and causes ipsilateral lateral deviation).

Identify the muscle of mastication highlighted in green and state its attachments and actions.

Masseter. Attachments: Quadrate muscle attaching to inferior border and medial surface of maxillary process. Actions: Elevates mandible, closing jaws; superficial fibers make limited contribution to protrusion of mandible.

Identify the muscle of mastication highlighted in green and state its bilateral and unilateral actions.

Lateral pterygoid. Actions: Bilaterally protracts mandible and depresses chin; unilaterally swings jaws toward contralateral side; alternate unilateral contraction produces lateral chewing.

What are the two anatomical attachments of the medial pterygoid muscle?

1) Medial surface of lateral pterygoid plate and pyramidal process of palatine bone; 2) Tuberosity of maxilla.

What three muscles of mastication elevate the mandible (mnemonic "MMT")?

1) Masseter; 2) Medial pterygoid; 3) Temporalis.

Which muscle of mastication is responsible for depressing the mandible?

Lateral pterygoid.

Which two muscles of mastication produce protrusion of the mandible?

Medial pterygoid and lateral pterygoid (with limited contribution from superficial masseter fibers).

A patient presents with left-sided craniofacial pain that is reproduced with lateral deviation of the mandible to the left. Which muscle is most likely involved?

Left temporalis (the temporalis produces ipsilateral lateral deviation).

How are the anterior muscles of the neck classified by functional group (agonist, stabilizer, proprioceptor)?

Agonist: Sternocleidomastoid, Scalene (anterior, middle, posterior). Stabilizer: Longus Capitis, Longus Colli. Proprioceptor: Rectus Capitis Anterior, Rectus Capitis Lateralis.

How are the posterior muscles of the neck classified by functional group (agonist, intermediate, stabilizer, proprioceptor)?

Agonist: Splenius (cervicis, capitis). Intermediate: Semispinalis, Erector spinae (iliocostalis, longissimus, spinalis). Stabilizer: Multifidus. Proprioceptor: Interspinalis, Intertransversarius, Suboccipitals.

What are the boundaries, floor, and roof of the suboccipital region?

Superomedial boundary: Rectus capitis posterior major. Superolateral boundary: Obliquus capitis superior. Inferolateral boundary: Obliquus capitis inferior. Floor: Atlanto-occipital (AO) membrane and posterior arch of $C1$ (atlas). Roof: Semispinalis capitis.

What nerve supplies all the suboccipital muscles (rectus capitis posterior major and minor, obliquus capitis superior and inferior)?

Suboccipital nerve (posterior ramus of $C1$ spinal nerve).

What is the nerve supply and bilateral vs. unilateral action of the sternocleidomastoid (SCM)?

Nerve Supply: Spinal accessory nerve ($CN\ XI$), $C3$ and $C4$ nerves (pain and proprioception). Unilateral: Tilts head to same side and rotates head so face turns superiorly to opposite side. Bilateral: Extends neck at atlanto-occipital joints, flexes cervical vertebrae so chin approaches manubrium, or extends cervical vertebrae moving chin forward while keeping head level.

What are the distal rib attachments and main actions of the anterior, middle, and posterior scalenes?

Anterior and middle scalenes attach to the 1st rib; posterior scalene attaches to the 2nd rib. Main actions: Flex the neck laterally; elevate the 1st or 2nd rib during forced inspiration.

What are the three columns of the erector spinae, and what are their bilateral and unilateral actions?

Three columns: Iliocostalis, longissimus, and spinalis. Bilateral action: Extend vertebral column and head (controlling movement via eccentric contraction as the back flexes). Unilateral action: Laterally flex the vertebral column.

What is the nerve supply and primary action of the multifidus muscle?

Nerve Supply: Posterior rami of spinal nerves. Main action: Stabilizes vertebrae during local movements of the vertebral column.

What nerve innervates the trapezius muscle, and what are its actions with the scapula fixed?

Nerve supply: Spinal accessory nerve ($CN\ XI$). With scapula fixed: Bilateral contraction contributes to extension of the neck; unilateral contraction contributes to ipsilateral lateral flexion and contralateral rotation of the neck.

What are the attachments, nerve supply, and action of the serratus anterior?

Proximal: Lateral parts of 1st-8th ribs. Distal: Anterior surface of medial border of scapula. Nerve supply: Long thoracic nerve. Main actions: Protracts scapula and rotates it upward; stabilizes scapula against thoracic wall.

What are the attachments, innervation, and action of the latissimus dorsi?

Proximal: Spinous processes of inferior 6 thoracic vertebrae, thoracolumbar fascia, iliac crest, inferior 3-4 ribs. Distal: Floor of intertubercular sulcus of humerus. Nerve supply: Thoracodorsal nerve. Main actions: Extends, adducts, and medially rotates humerus.

What four muscles make up the rotator cuff, and what are their respective innervations?

1) Supraspinatus (suprascapular nerve); 2) Infraspinatus (suprascapular nerve); 3) Teres minor (axillary nerve); 4) Subscapularis (upper and lower subscapular nerves).

What mechanical effect do rotator cuff muscles have at the glenohumeral joint during shoulder abduction?

They promote compression between the humeral head and glenoid fossa to reduce superior translation of the humeral head.

Which combination of scapular motions is required for full overhead reaching?

Upward rotation, posterior tilt, and internal rotation.

Which three muscles compose the anterior compartment of the arm, and what is their primary innervation?

Biceps brachii, brachialis, and coracobrachialis. Primary innervation is the musculocutaneous nerve (brachialis also receives a contribution from the radial nerve).

What are the three heads of the triceps brachii muscle, and what nerve innervates them?

Long head (infraglenoid tubercle), lateral head (posterior humerus superior to radial groove), and medial head (posterior humerus inferior to radial groove). Innervated by the radial nerve.

How are the muscles of the anterior compartment of the forearm divided by layers?

Superficial: Pronator teres, flexor carpi radialis, palmaris longus, flexor carpi ulnaris. Intermediate: Flexor digitorum superficialis. Deep: Flexor digitorum profundus, flexor pollicis longus, pronator quadratus.

Which muscles or parts of muscles in the anterior forearm are innervated by the ulnar nerve rather than the median or anterior interosseous nerve?

Flexor carpi ulnaris and the medial half of flexor digitorum profundus (digits 4 and 5).

Which muscles form the superficial and deep layers of the posterior forearm?

Superficial: Brachioradialis, extensor carpi radialis longus, extensor carpi radialis brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris. Deep: Supinator, abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, extensor indicis.

Which nerve innervates the deep outcropping muscles of the posterior forearm (abductor pollicis longus, extensor pollicis longus, extensor pollicis brevis, extensor indicis)?

Posterior interosseous nerve (continuation of the deep branch of the radial nerve).

What are the four thenar muscles, and which nerves innervate them?

Opponens pollicis, abductor pollicis brevis, flexor pollicis brevis, and adductor pollicis. Innervation: Recurrent branch of the median nerve (opponens pollicis, abductor pollicis brevis, superficial head of flexor pollicis brevis) and deep branch of the ulnar nerve (deep head of flexor pollicis brevis, adductor pollicis).

What are the actions and nerve supplies of the lumbrical muscles in the hand?

Actions: Flex the metacarpophalangeal ($MCP$) joints and extend the interphalangeal ($PIP$ and $DIP$) joints of digits 2-5. Innervation: Median nerve for lumbricals 1 and 2; deep branch of ulnar nerve for lumbricals 3 and 4.

What are the actions and mnemonics for the dorsal and palmar interossei muscles of the hand?

Dorsal interossei: Abduct digits 2-4 ("DAB"). Palmar interossei: Adduct digits 2, 4, and 5 ("PAD"). Both also assist lumbricals in MCP flexion and IP extension; all innervated by the deep branch of the ulnar nerve.

What mnemonic describes the structural sequence of the brachial plexus from proximal to distal?

"Randy Travis Drinks Cold Beer": Roots ($C5-T1$), Trunks (Superior, Middle, Inferior), Divisions (Anterior, Posterior), Cords (Lateral, Posterior, Medial), Branches.

What are the segmental levels, motor targets, and cutaneous territory of the radial nerve?

Segmental levels: $C5, C6, C7, C8$. Motor: Brachialis, triceps brachii, anconeus, brachioradialis, extensor carpi radialis longus and brevis, extensor digitorum, extensor digiti minimi, extensor carpi ulnaris, supinator, extensor indicis, abductor pollicis longus, extensor pollicis brevis, extensor pollicis longus. Cutaneous: Posterior lateral forearm, below axilla area, dorsum of hand (digits 1-3, excluding fingertips).

What are the cervical myotomes from level $C1$ to $T1$?

$C1$: Cervical flexion or rotation; $C2$: Cervical extension; $C3$: Cervical lateral flexion; $C4$: Shoulder shrug; $C5$: Shoulder abduction and elbow flexion; $C6$: Elbow flexion and wrist extension; $C7$: Elbow extension; $C8$: Thumb extension or finger flexion; $T1$: Finger abduction.

What are the dermatome locations and deep tendon reflexes for spinal levels $C5$, $C6$, and $C7$?

$C5$: Lateral shoulder; Biceps reflex. $C6$: Webbing between fingers 1 and 2; Brachioradialis reflex. $C7$: Dorsum of middle finger; Triceps reflex.

How do arterial and venous flows differ in direction, and how does a blockage affect flow in each system?

Arterial: Flows proximal to distal (aorta to hands); a blockage affects blood flow to arteries distal to the blockage. Venous: Flows distal to proximal (arm toward heart); a blockage affects blood flow to all veins proximal (upstream) to the blockage.