Muscle Anatomy and Function

These flashcards cover the key muscles of the head, neck, back, thorax, and abdomen, focusing on their identification, functions, and actions.

Orbicularis muscles

Circular muscles around openings.

Orbicularis oculi

Muscle surrounding the eye socket that closes eyelids.

Why does contracting the right external oblique cause a rotation in the left side?

• Origin: ribs (top)

• Insertion: pelvis (bottom)

• 👉 It pulls:

  • ribs down + toward left pelvis

  So your upper body:
  ➡ twists LEFT

  ✔ = contralateral rotation
  

Orbicularis oris

Muscle around the lips that closes lips.

Levator costae

Muscle that elevates the ribs, aiding in inhalation.

Frontalis

Flat muscle covering the forehead that raises eyebrows.

Buccinator

Flat muscle in the cheek wall that keeps food between teeth during chewing.

Masseter

Large rectangular muscle on side of jaw that elevates mandible. Origin: zygomatic arch

Insertion: lateral surface of the mandibular ramus

Temporalis

A large fan-shaped muscle on the side of the skull that elevates and retracts the mandible.

origin: floor of the temporal fossa

Insertion: coronoid process of the mandible

Pterygoid muscles

Deep muscles near the TMJ responsible for jaw protrusion and side-to-side movement.

Extrinsic eye muscles

Muscles controlling eye movement; there are 6, including 4 rectus and 2 oblique.

Rectus muscles

Muscles that run straight from the back of the orbit to the eye.

Oblique muscles

Muscles that run diagonally across the eyeball.

Superior rectus

Muscle that elevates the eye.

Inferior oblique

extorsion (outward rotation), elevation and abduction.

Inferior rectus

Muscle that depresses the eye.

Superior oblique

• Primary action: intorsion

• Secondary: depression

• Tertiary: abduction (helping with lateral movement)

Lateral rectus

Muscle that abducts the eye.

Medial rectus

Muscle that adducts the eye.

Sternocleidomastoid (SCM)

Large diagonal muscle running across the side of the neck.

SCM inerstion and origin

Attaches to sternum, clavicle, and mastoid process.

Bilateral SCM contraction

Flexes the neck (the head is pulled forward)

Unilateral SCM contraction

Two options: contralteral rotation of the head (makes the face move in the opposite direction) or ipsilateral lateral rotation

Contraction of the msucles makes the origin and insertion…

move more closely together

Suprahyoid muscles

Muscles that elevate the hyoid bone.

Stylohyoid

Muscle that runs from the styloid process of the temporal bone to the hyoid bone, assisting in elevating the hyoid during swallowing.

Digrastic

muscle with two muscle bellies that helps to depress the mandible and elevate the hyoid bone.

Infrahyoid muscles

Muscles that depress the hyoid bone.

Scalene muscles

Muscles located on the sides of cervical vertebrae.

Lateral flexion of the scalene muscles

refers to the bending of the neck to the side, facilitating movements such as turning the head.

Bilateral flexion of the scalene muscle

elevates the first and second ribs

Intrinsic back muscles

Deep muscles that stabilize and move the vertebral column.

Erector spinae

The largest intrinsic back muscle group responsible for extending the spine.

Unilateral contraction of the erector spinae

involves lateral flexion and rotation of the vertebral column toward the same side.

Transversospinales

Muscle group stabilizing and rotating vertebrae. Semispinalis, multifidus, rotatores.

Semispinalis

The semispinalis is a muscle of the transversospinales group, primarily responsible for extending and rotating the vertebral column. Capitis, Cervicis, Thoracis

Splenius capitus

is a muscle in the splenius group that extends and rotates the head and neck.

Spinotransversales group

A group of muscles including the splenius capitis and splenius cervicis, responsible for extending and rotating the head and neck.

Splenius cervicus

is a muscle in the splenius group that extends and rotates the head and neck, similar to the splenius capitis.

Multifidus

A muscle of the transversospinales group, the multifidus stabilizes the vertebral column and assists in the rotation and extension of the spine.

Rotatores

The rotatores are a group of muscles within the transversospinales, located between the vertebrae and primarily involved in stabilizing and rotating the spine.

Intercostal muscles

Muscles located between ribs that aid in breathing.

External intercostals

Muscles that elevate ribs during inhalation.

Internal intercostals

Muscles that depress ribs during exhalation.

Innermost intercostals

Muscles located beneath the internal intercostals that assist with forced exhalation.

Serratus posterior superior

Muscle that elevates ribs.

Serratus posterior inferior

Muscle that depresses ribs.

Abdominal muscles

Muscles responsible for flexing the trunk, compressing the abdomen, and assisting in breathing.

Thoracic diaphragm

The main muscle of breathing that separates the thoracic and abdominal cavities.

Pelvic diaphragm

Muscles that support pelvic organs and form the pelvic floor.

Modiolus

A fibromuscular node at the corner of the mouth where many facial muscles attach.

Facial nerve (CN VII)

Nerve that innervates most facial expression muscles.

Aponeurosis

A flat sheet-like tendon connecting muscles.

Chewing

Another term for mastication.

Temporomandibular joint (TMJ)

Joint that mastication muscles move.

Trigeminal nerve (CN V)

Nerve that innervates mastication muscles.

Iliocostalis

Lateral column of the erector spinae.

Longissimus

Middle column of the erector spinae.

Spinalis

Medial column of the erector spinae.

Splenius

Intrinsic back muscle found in the posterior neck responsible for extending and rotating the neck.

Levator ani

Muscle that along with coccygeus forms the pelvic diaphragm.

Coccygeus

Muscle that supports pelvic organs and completes the pelvic diaphragm.

Food between the teeth

Function of the buccinator during chewing.

Zygomaticus major

Muscle that raises the corners of the mouth (smiling).

Epicranius

Muscle with two bellies connected by an aponeurosis.

Levator palpebrae superioris

Muscle that elevates the upper eyelid.

Occipitalis

Muscle that forms the back of the epicranius.

Lateral flexion

Movement achieved by unilateral contraction of the SCM or intrinsic back muscles.

Bilateral contraction

Result in flexion or extension of the neck or spine.

Muscle architecture

Determines the movement and force a muscle can produce.

Line of action

Direction a muscle pulls between its attachments.

Facial expression muscles

Muscles that move the skin of the face to produce facial expressions.

Hyoid bone

Bone separating suprahyoid and infrahyoid muscles.

Shoulder girdle

Not discussed explicitly, but connects to neck and upper limb muscles.

Fibre direction of external oblique

Fibres run downwards like putting hands in pockets.

Fibre direction of internal oblique

Fibres run upwards and medially.

Fibre direction of transversus abdominis

Fibres run horizontally.

Inspiration

Breathing in, involving several muscles including scalene.

Expiration

Breathing out, primarily involving internal intercostals.

Absence of muscle contraction

Results in relaxation of thoracic cavity during exhalation.

Muscle contraction

Increases pressure in the thoracic cavity.

Facial movement coordination

Function of the modiolus.

Common exam focus

Patterns of shape, position, and fibre direction rather than minute details.

Pelvic support

Function of the pelvic diaphragm muscles.

Transversospinales group

Includes semispinalis, multifidus, and rotatores.

Flex trunk

Main function of abdominal muscles.

Ribs attached by scalenes

Ribs 1 and 2.

Muscles attached to hyoid

Suprahyoid elevate, infrahyoid depress.

Bilateral contraction of the erector spinae

is a mechanism that extends the vertebral column, allowing for upright posture and stability.

Recti vs. Obliques

Difference in muscle alignment affecting eye movement.

Rectus definition

Means straight.

Oblique definition

Means diagonal or angled.

Attachment angles

Influence the movement of oblique muscles.

Muscle innervation

Determines function and control of muscles.

Facial expression coordination

Affected by the modiolus and facial nerve.

Prevention of cheek collapse during chewing

Role of the buccinator.

Facial movements role

Controlled primarily by facial expression muscles.

Muscle group function

Muscles categorized by location and action.

Hyoid elevation

Function of suprahyoid muscles.

Hyoid depression

Function of infrahyoid muscles.