Muscles of Axial Skeleton

Functional organization of axial muscles

Head and neck, vertebral column and posterior trunk, respiration, abdominal wall, pelvic floor

Muscles of facial expression

Many attach to skull and subcutaneous tissue; contraction moves the skin

Major muscles of facial expression

Frontalis, occipitalis, orbicularis oculi, orbicularis oris, zygomaticus major, depressor anguli oris, buccinator, platysma

Frontalis

Elevates eyebrows, wrinkles forehead

Occipitalis

Retracts scalp

Orbicularis oculi

Closes eye

Orbicularis oris

Closes and purses lips

Zygomaticus Major

Elevates corner of mouth

Depressor Anguli Oris

Depresses corner of mouth

Buccinator

Compresses cheek

Platysma

Tenses skin of neck, helps depress lower lip

Extrinsic eye muscles

Superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, inferior oblique

Superior Rectus

Elevates eye, moves eye medially (adducts)

Inferior Rectus

Depresses eye, moves eye medially

Medial Rectus

Moves eye medially

Lateral Rectus

Moves eye laterally (abducts)

Superior Oblique

Depresses eye, moves eye laterally

Inferior Oblique

Elevates eye, moves eye laterally

Muscles of mastication

Move mandible at temporomandibular joint (TMJ); temporalis, masseter, medial pterygoid, lateral pterygoid

Temporalis

Elevates and retracts mandible

Masseter

Elevates and protracts mandible

Medial pterygoid

Elevates and protracts mandible, helps produce side to side movement

Lateral pterygoid

Protracts mandible and helps produce side to side movement

Muscles that move tongue

Genioglossus, styloglossus, hyoglossus

Genioglossus

Protracts tongue

Styloglossus

Elevates tongue, retracts tongue

Hyoglossus

Depresses tongue, retracts tongue

Muscles that move the head and neck

Sternocleidomastoid, splenius capitis

Sternocleidomastoid

Unilateral: rotates head to opposite side; bilateral: flexes head/neck

Splenius capitis

Unilateral: Rotates head to same side; bilateral: extends head/neck

Suprahyoid muscles

Generally elevate hyoid; digastric, stylohyoid, mylohyoid, geniohyoid

Infrahyoid muscles

Generally depress hyoid or move thyroid cartilage; sternohyoid, omohyoid, sternothyroid, thyrohyoid

Muscles of vertebral column

Deep muscles support and move the vertebral column; erector spinae, quadratus lumborum

Major functions of vertebral column muscles

Postural support, extension, lateral flexion, rotation by selected muscles

Erector spinae

Large longitudinal muscle group; iliocostalis (most lateral), longissimus (intermediate), spinalis (most medial); collectively extend vertebral column and help maintain posture

Quadratus Lumborum

Bilaterally: extends lumbar vertebral column; unilaterally: laterally flexes vertebral column to side

Muscles of respiration

Breathing depends on changes in thoracic cavity dimensions; diaphragm, scalenes, external intercostals, internal intercostals

Inspiration

Thoracic dimensions increase

Expiration

Thoracic dimensions decrease

Diaphragm

Contracts and flattens; increases in the vertical dimension of thorax; major muscle of inspiration

Scalenes

Elevate ribs 1-2; assist forced inspiration

External intercostals

Elevate ribs, assist inspiration

Internal intercostals

Depress ribs; assist forced expiration

Abdominal wall organization

External oblique, internal oblique, rectus abdominis, transversus abdominis

External oblique

Superficial; fibers run inferomedially; laterally flexes trunk; rotates trunk to opposite side; compresses abdomen

Internal oblique

Deep to external oblique; fibers run superomedially; laterally flexes trunk; rotates trunk to same side; compresses abdomen

Rectus abdominis

Anterior, fibers run vertically; flexes vertebral column

Transversus abdominis

Deepest, fibers run horizontally; helps stabilize abdominal wall; assists forced expiration

ID 1

Frontalis

ID 2

Temporalis

ID 3

Occipitalis

ID 4

Orbicularis oculi

ID 5

Orbicularis oris

ID 1

Zygomaticus major

ID 2

Depressor anguli oris

ID 3

Buccinator

ID 4

Platysma

ID 1

Depressor anguli oris

ID 2

Orbicularis oculi

ID 3

Frontalis

ID 4

Platysma

ID 5

Zygomaticus major

ID 6

Orbicularis oris

ID 1

Superior oblique

ID 2

Superior rectus

ID 3

Lateral rectus

ID 4

Inferior oblique

ID 5

Inferior rectus

ID 1

Superior rectus

ID 2

Superior oblique

ID 3

Lateral rectus

ID 4

Inferior oblique

ID 5

Inferior rectus

ID 6

Medial rectus

ID 1

Temporalis

ID 2

Masseter

ID 1

Temporalis

ID 2

Lateral pterygoid

ID 3

Medial pterygoid

ID 4

Masseter

ID 1

Temporalis

ID 2

Masseter

ID 1

Genioglossus

ID 2

Styloglossus

ID 3

Hyoglossus

Pelvic floor

Made up of pelvic diaphragm; forms muscular floor of the abdominopelvic cavity; supports pelvic viscera; contributes to urinary continence, fecal continence, and reproductive functions

ID 1

Splenius capitis

ID 2

Sternocleidomastoid

ID 1

Erector spinae

ID 2

Iliocostalis

ID 3

Longissimus

ID 4

Spinalis

ID 5

Quadratus lumborum

ID 1

Scalenes

ID 2

Internal intercostals

ID 3

Diaphragm

ID 4

External intercostals

ID 1

Rectus abdominis

ID 2

Tranversus abdominis

ID 3

Internal oblique