Lecture 12: Axial Muscles

A comprehensive set of vocabulary flashcards covering major axial muscles, their innervation, locations, and primary actions as discussed in the 11/20/19 lecture.

Axial muscles

Muscles whose origins and insertions lie on the axial skeleton and that support the head, spine, breathing, swallowing, and protection of thoracic–abdominopelvic organs.

Facial nerve (CN VII)

Cranial nerve that innervates most muscles of facial expression.

Epicranius

Bipartite muscle with frontalis and occipitalis bellies that raises eyebrows and wrinkles scalp skin.

Frontalis

Anterior belly of epicranius that elevates eyebrows and wrinkles forehead.

Occipitalis

Posterior belly of epicranius that pulls scalp posteriorly.

Orbicularis oculi

Circular muscle around the eye responsible for closing eyelids; blinking and squinting.

Corrugator supercilii

Draws eyebrows medially and downward, creating vertical forehead wrinkles (frowning muscle).

Orbicularis oris

Encircles mouth; closes and puckers lips (kissing muscle).

Buccinator

Compresses cheek, keeps food between teeth, aids suckling and wind-instrument playing.

Depressor labii

Pulls lower lip downward (pouting).

Levator labii

Raises upper lip (shows upper teeth, snarling).

Risorius

Draws corner of mouth laterally (smiling/grimacing).

Zygomaticus major

Elevates and draws angle of mouth laterally (main smiling muscle).

Zygomaticus minor

Elevates upper lip to assist smiling or showing teeth.

Platysma

Thin neck muscle that tenses skin of neck and depresses mandible.

Extrinsic eye muscles

Six sclera-attached muscles controlling eyeball position.

Medial rectus

Pulls eye medially.

Lateral rectus

Pulls eye laterally.

Inferior rectus

Pulls eye downward.

Superior rectus

Pulls eye upward.

Inferior oblique

Elevates eye and turns it laterally.

Superior oblique

Depresses eye and turns it laterally.

Intrinsic eye muscles

Internal ocular muscles that adjust lens and pupil for focusing.

Muscles of mastication

Temporalis, masseter, medial & lateral pterygoids; all innervated by mandibular branch of trigeminal nerve (CN V3).

Temporalis

Elevates and retracts mandible.

Masseter

Elevates and protracts mandible; prime jaw closer.

Medial pterygoid

Protracts mandible; produces side-to-side grinding.

Lateral pterygoid

Protracts mandible; aids side-to-side grinding.

Genioglossus

Extrinsic tongue muscle that protracts (sticks out) tongue.

Styloglossus

Elevates and retracts tongue.

Hyoglossus

Depresses and retracts tongue.

Palatoglossus

Elevates posterior tongue; part of soft palate.

Pharyngeal constrictors (superior, middle, inferior)

Sequentially contracting muscles that initiate swallowing by moving food bolus through pharynx.

Suprahyoid muscles

Digastric, stylohyoid, mylohyoid, geniohyoid; elevate hyoid during swallowing.

Infrahyoid muscles

Omohyoid, sternohyoid, sternothyroid, thyrohyoid; depress hyoid during swallowing.

Sternocleidomastoid

Anterior-lateral neck muscle that flexes head and rotates it to opposite side.

Scalenes

Lateral neck muscles aiding neck flexion and assisting inhalation by elevating ribs 1–2.

Pectoralis major

Large chest muscle that flexes, adducts, and medially rotates humerus.

Pectoralis minor

Draws scapula forward and downward; accessory muscle of respiration.

Subclavius

Small muscle stabilizing and depressing clavicle.

Serratus anterior

Protracts and rotates scapula; “boxer’s muscle.”

Intercostal muscles

External and internal layers between ribs that assist diaphragm in breathing.

Diaphragm

Dome-shaped muscle forming thoracic floor; prime mover of inspiration by flattening to enlarge thoracic cavity.

Trapezius

Large superficial back muscle elevating, retracting, and rotating scapula.

Latissimus dorsi

Broad back muscle extending, adducting, and medially rotating humerus.

Erector spinae (Sacrospinalis)

Iliocostalis, longissimus, spinalis group that extends and laterally flexes vertebral column.

Quadratus lumborum

Deep back muscle that laterally flexes spine and stabilizes 12th rib during breathing.

Rectus abdominis

Anterior abdominal muscle divided by linea alba; flexes trunk and compresses abdomen.

Linea alba

Midline fibrous raphe separating right and left rectus abdominis.

External oblique

Superficial lateral abdominal muscle aiding trunk rotation and compression.

Internal oblique

Middle lateral abdominal layer; functions similarly to external oblique but with opposite fiber direction.

Transverse abdominis

Deepest abdominal wall muscle; compresses abdominal contents.

Coccygeus

Pelvic floor muscle supporting pelvic organs and flexing coccyx.

Levator ani

Primary pelvic diaphragm muscle (pubococcygeus, iliococcygeus) that supports pelvic viscera and maintains continence.

External anal sphincter

Voluntary skeletal muscle surrounding anus that closes anal canal.