3.3 Axial Muscles

Galea Aponeurotica

Fibrous connective tissue superficial to the cranium, connecting the frontalis and occipitalis muscles

Frontalis Muscle

Superficial to the frontal bone

Action of Frontalis muscle

Pulls the scalp anteriorly, raises the eyebrows, and wrinkles the forehead

Occipitalis Muscle

Superficial to the occipital bone

Action of Occipitalis Muscle

Pulls the scalp posteriorly

Orbicularis Oculi Muscle

Superficial; oculi refers to the area around the eyes

Action of Orbicularis Oculi Muscle

Closes the eyelids

Corrugator Supercilii Muscle

Deep; corrugator means to wrinkle and supercilii means eyebrow

Action of Corrugator Supercilii Muscle

Frowning muscle; wrinkles the eyebrows

Nasalis Muscle

Superficial to the nasal bones

Action of Nasalis Muscle

Flares the nostrils

Procerus Muscle

A small, pyramidal-shaped muscle located in the upper part of the nose and lower forehead

Action of Procerus Muscle

Frowning and wrinkling the skin between the eyebrows

Orbicularis Oris Muscle

Superficial; oris refers to the area around the mouth; attached to the modiolus

Orbicularis Oris Muscle

Closes the mouth; puckers the lips; uniquely developed in humans for speech

Zygomaticus Minor Muscle

Superficial; zygomaticus refers to the cheekbones; minor means small; located medial to the zygomaticus major muscle and lateral to the levator labii superioris muscle

Action of Zygomaticus Minor Muscle

Elevates the upper lip for smiling or sneering

Zygomaticus Major Muscle

Superficial; major means big; located superolateral to the orbicularis oris muscle and attached directly to the modiolus

Action of Zygomaticus Major Muscle

Draws the angle of the mouth upward and laterally for laughing

Risorius Muscle

Superficial to the masseter muscle; lateral to the lips; attached directly to the modiolus

Action of Risorius Muscle

Draws the angle of the mouth laterally for laughing, expressing horror, or disdain

Levator Labii Superioris Muscle

Superficial; levator means to elevate; labii superioris refers to the upper lip; located medial to the zygomaticus minor muscle and attached superomedial to the orbicularis oris muscle

Action of Levator Labii Superioris Muscle

Elevates the upper lip

Depressor Labii Inferioris Muscle

Superficial to the mentalis muscle; depressor means downward movement; located inferolateral to the orbicularis oris muscle and attached to it

Action Depressor Labii Inferioris Muscle

Draws the lower lip downward

Modiolus

A fibrous tissue located superficially on the lateral side of the lips where facial muscles intersect, including the superficial orbicularis oris, risorius, zygomaticus major muscles, and the deep buccinator muscle

Action of Modiolus

Provides stability for mouth movement and facial expression

Buccinator Muscle

Deep to the masseter muscle

Action of Buccinator Muscle

Compresses the cheeks; aids in food positioning for chewing or sucking

Mentalis Muscle

Deep; located in the mental region

Action of Mentalis Muscle

Elevates and wrinkles the skin of the chin; elevates the lower lip as in drinking or pouting

Platysma Muscle

Superficial on the anterolateral side of the neck

Action of Platysma Muscle

Creates a downward sag of the mouth; tenses the skin of the neck

Temporalis Muscle

Superficial to the temporal bone

Action of Temporalis Muscle

Closes the jaw; elevates and pulls back the mandible

Masseter Muscle

Intermediate; deep to the risorius muscle and superficial to the buccinator muscle

Action of Masseter Muscle

Closes the jaw; principal muscle for jaw movement

Levator Labii Superioris Alaeque Nasi (LLSAN) Muscle

The muscle with the longest name in the human body; located superficially on the lateral side of the nose

Action of Levator Labii Superioris Alaeque Nasi (LLSAN) Muscle

Enables you to snarl

Where do all neck muscles insert

hyoid bone

what is the suprahyoid muscle group

Four muscles located superior to the hyoid bone; forms the floor of the oral cavity

what is the action of suprahyoid muscle group

Provides an anchor for the tongue, elevates the hyoid bone, depresses the mandible bone, and moves the larynx (voice box) superiorly during swallowing

what is the digastric anterior belly and posterior belly muscles

superficial; the anterior belly attaches from the internal side of the mandible to the hyoid bone, while the posterior belly attaches from the hyoid bone to the mastoid notch

action of digastric anterior belly and posterior belly muscles

Both bellies elevate the hyoid bone and open the mouth widely, as when ingesting food or yawning

what is the stylohyoid muscle

Superficial; attaches from the hyoid bone to the styloid process of the temporal bone; lies anterior and medial to the digastric posterior belly muscle

action of stylohyoid muscle

Elevates the hyoid bone

what is Mylohyoid Muscle

Intermediate; located deep to the digastric anterior belly muscle and superficial to the geniohyoid muscle; forms the floor of the mouth and spans the mandible from side to side; mylo- refers to molars

action of Mylohyoid Muscle

Elevates the floor of the mouth during the initial stage of swallowing

what is Geniohyoid Muscle

Deep; located deep to the mylohyoid muscle; genio- refers to the chin

action of Geniohyoid Muscle

Depresses the mandible and elevates the hyoid bone

What is the primary action of the infrahyoid muscle group?

Depresses either the hyoid bone or the larynx during swallowing and speaking.

what is the sternohyoid muscle?

Superficial and medial to the omohyoid superior belly muscle; attaches to the hyoid bone and manubrium.

action of the sternohyoid muscle?

Depresses the hyoid bone.

what is the omohyoid muscle group?

Superficial and located lateral to the sternohyoid muscle; insert on the hyoid bone, pass under the sternocleidomastoid muscle, then attach to the superior border of the scapula bone; omo- means shoulder

action of omohyoid muscle group

Depresses the hyoid bone

What is the action of the thyrohyoid muscle?

Depresses the hyoid bone and elevates the larynx, as when singing high notes.

what is the thyrohyoid muscle

Deep and medial; located superior to the sternothyroid muscle; attaches to the thyroid cartilage and hyoid bone

what is the sternothyroid muscle

Deep and medial; located inferior to the thyrohyoid muscle; attaches to the manubrium and thyroid cartilage

What is the action of the sternothyroid muscle?

Depresses the larynx and aids in singing low notes.

What is the primary action of the sternocleidomastoid (SCM) muscle?

Prime mover of neck flexion.

what is the sternocleidomastoid muscle?

Superficial; located anterolaterally; attaches to the mastoid process, clavicle bone, and manubrium

What are the scalene muscles responsible for?

Flexing the neck and tilting the head toward the same shoulder.

How are the scalene muscles arranged?

Like a staircase, consisting of anterior, middle, and posterior scalene muscles.

What is the scalene triangle?

A small space in the side of the neck formed between two scalene muscles and the first rib.

What are the borders of the scalene triangle?

Front: Anterior scalene muscle; Back: Lateral/Middle scalene muscle; Bottom: First rib.

What is the function of the scalene triangle?

Important nerves and blood vessels pass through this space to reach the upper limb.

What is the primary function of the intercostal and diaphragm muscles?

They allow the body to perform breathing, moving air in and out of the lungs.

What distinguishes respiration from breathing?

Respiration is the chemical process of utilizing gases in metabolic systems, while breathing is the physical movement of air.

What is the action of the external intercostal muscles?

Elevates the ribcage; aids in inspiration by expanding the thoracic cavity (creating more space)

what is the external intercostal muscles?

Superficial; their fibers slope downward and anteriorly

What is the action of the internal intercostal muscles?

Depresses the ribcage; aids in expiration by compressing the thoracic cavity (creating less space)

what is the internal intercostal muscles?

Intermediate; located deep to the external intercostal muscles but superficial to the innermost intercostal muscles; their fibers slope downward and posteriorly

what is innermost intercostal muscles

Deepest layer of the intercostal muscles; their fibers run in the same direction as the internal intercostal muscles

action of innermost intercostal muscles

Same as the internal intercostal muscles

what is the diaphragm muscle

Dome-shaped muscle that separates the thoracic cavity from the abdominopelvic cavity

action of diaphragm muscle

Muscle contraction flattens the diaphragm to increase lung volume; when the muscle relaxes, it returns to its dome-like shape, which decreases lung volume; principal muscle for inspiration

Rectus Abdominis Muscle

Intermediate and the only medial abdominal muscle; it is completely enclosed by a fibrous fascia called the anterior and posterior rectus sheath, which is why this muscle is considered intermediate (between the sheaths). Rectus means straight. The 'six-pack' appearance is created by tendinous intersections. Its fibers run vertically.

Action of Rectus Abdominis Muscle

Flexes and rotates the lumbar region of the vertebral column; stabilizes the pelvic region during walking.

External Abdominal Oblique Muscle

Superficial and lateral; its fibers run downward and medially. It is attached inferiorly to the cord-like inguinal ligament, which separates it from the pelvic region.

Action of External Abdominal Oblique Muscle

Flexes the vertebral column when contracting simultaneously; maintains posture.

Internal Abdominal Oblique Muscle

Intermediate and lateral; located superficial to the transverse abdominal muscle and deep to the external abdominal oblique muscle. Its fibers run upward and laterally.

Action of Internal Abdominal Oblique Muscle

Same movement as the external abdominal oblique muscle.

Transverse Abdominal Muscle

Deepest and lateral abdominal muscle; its fibers run horizontally.

Action of Transverse Abdominal Muscle

Compresses the abdominal cavity; does not contribute to movement of the vertebral column.

Linea Alba

Median line or border between the right and left rectus abdominis muscles.

Linea Semilunaris

Lateral line or border between the rectus abdominis and external abdominal oblique muscles.

what are externally visible on individuals with well-defined abdominal muscles.

linea alba, linea semilunaris, inguinal ligament, and tendinous intersections

Trapezius Muscle

Superficial and posterior; shaped like a trapezium.

Action of Trapezius Muscle

Extends the neck, stabilizes the scapula, and works with the rhomboid muscles for neck extension.

Splenius Capitis and Cervicis Muscles

Intermediate and posterior; the splenius capitis muscle is located superior to the splenius cervicis muscle. Splenius means bandage or patch, capitis refers to the head, and cervicis refers to the neck region.

Action of Splenius Capitis and Cervicis Muscles

Extends the head.

Semispinalis Capitis and Cervicis Muscles

Deep and posterior; the semispinalis capitis muscle is located superior to the semispinalis cervicis muscle.

Action of Semispinalis Capitis and Cervicis Muscles

Extends and rotates the head.

Rhomboid Major and Minor Muscles

Intermediate muscles; shaped like a rhombus.

Action of Rhomboid Major and Minor Muscles

Stabilize the scapula; work in conjunction with the trapezius muscle for neck extension.

Levator Scapulae Muscle

Attaches to the superior angle and the medial border of the scapula.

Action of Levator Scapulae Muscle

Elevates the scapula.

Erector Spinae Muscle Group

Intermediate to deep group of muscles; consists of three columns arranged from medial to lateral: spinalis, longissimus, and iliocostalis muscles.

Action of Erector Spinae Muscle Group

Principal muscle group for extending the back.

Multifidus Muscle (plural: multifidi)

Deep; originates on vertebrae C4 to L5 and the sacrum.