muscles that act on the axial skeleton

Muscles that

Act on the

Axial Skeletonby Carone Learning

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Muscles that Act on the Axial Skeleton

Axial Skeleton

The axial skeleton is part of the

skeletal system that includes the skull,

ribcage, and vertebral column.

Muscles of the axial skeleton perform

the following functions:

• Facial expressions

• Chewing

• Ventilation

• Control the neck

Axial Skeleton

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The following muscles control facial

expressions:

• Epicranius

• Orbicularis oris

• Buccinator


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Facial Expressions

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Epicranius

The epicranius is actually composed of

two muscles that are separated by the

galea aponeurotica. The galea

aponeurotica is a broad sheath of

connective tissue.

The two muscles that combine to form

the epicranius are:

1. Frontalis

2. Occipitalis


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Frontalis

Frontalis- elevates the eyebrow and

wrinkles the forehead

• Origin: galea aponeurotica

• Insertion: skin of eyebrow


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Occipitalis

Occipitalis- moves scalp backwards

• Origin: occipital bone and mastoid

process of the temporal bone

• Insertion: galea aponeurotica


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Orbicularis Oris

Orbicularis oris- closes the lips, forms

words, and puckers the lips. This is your

kissing muscle!

• Origin: fascia surrounding lips

• Insertion: skin of the lips


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Buccinator

Buccinator- compresses the cheeks.

You use this muscle to suck and blow

air.

• Origin: maxilla and mandible

• Insertion: orbicularis oris


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Mastication

The movements of chewing and biting

are known as mastication.

The muscles that aid with mastication

include:

• Temporalis

• Masseter

• Medial and lateral pterygoid


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Temporalis

Temporalis- closes the mouth by

elevating the mandible

• Origin: temporal fossa of the

zygomatic bone

• Insertion: coronoid process of

mandible


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Masseter

Masseter- closes the mouth by

elevating the mandible. It is superficial

so you can see this muscle as you bite

down.

• Origin: zygomatic arch

• Insertion: lateral ramus of mandible


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Pterygoid

Medial and lateral pterygoid- elevates

and protracts the mandible. They also

move the mandible laterally.

• Origin: sphenoid bone

• Insertion: mandible


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Prime Movers of the Neck

Two prime movers of the neck are:

1. Sternocleidomastoid

2. Splenius capitis


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Sternocleidomastoid

Sternocleidomastoid- runs along the

side of the neck. When one contracts,

the head turns to the opposite side. For

example, if the right sternocleidomastoid

contracts, the head pivots to the left.

When both sides contract, the head is

pulled forward and down.

• Origin: sternum and clavicle

• Insertion: mastoid process of

temporal bone


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Splenius Capitis

Splenius capitis- extends the head. It

also laterally flexes and rotates head at

the same time.

• Origin: inferior half of ligamentum

nuchae (C3-C6) and spinous process

of C7-T3

• Insertion: superior nuchal line of

occipital bone and mastoid process

of temporal bone


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Ventilation

Ventilation, or breathing, is moving air

into and out of the lungs.

Muscles that aid with ventilation include:

• Diaphragm

• External intercostals

• Internal intercostals


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Diaphragm

Diaphragm- pulls the central tendon

inferiorly and increases the vertical

dimensions of the thorax. During

inhalation, or breathing in, the

diaphragm contracts and makes more

room in the chest cavity. During

exhalation, or breathing out, the

diaphragm recoils passively upwards.

• Origin: xiphoid process of the

sternum, costal cartilages of lower

ribs, and lumbar vertebrae

• Insertion: central tendon of the

diaphragm


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External Intercostals

External intercostals- elevates and

draws ribs together during restful

breathing. During inhalation, the external

intercostals move the ribs up and out to

make more room in the chest cavity.

During exhalation, the ribs passively

return to their starting position.

• Origin: inferior border of a rib

• Insertion: superior border of the rib

below


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Internal Intercostals

Internal intercostals- draws the ribs

together and depresses the thorax

during forceful breathing. This occurs

during exercise when your body forces

exhalation.

• Origin: superior border of a rib

• Insertion: inferior border of the rib

above


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Functions

Muscles of the axial skeleton perform

the following functions:

• Facial expressions

• Chewing

• Ventilation

• Control the neck

©Life Art

© Carone Learning

Facial Expressions

The following muscles control facial

expressions:

• Epicranius

• Orbicularis oris

• Buccinator


©Life Art

© Carone Learning

Mastication

The muscles that aid with mastication,

or chewing, include:

• Temporalis

• Masseter

• Medial and lateral pterygoid


©Life Art

© Carone Learning

Prime Movers

Two prime movers of the neck are:

1. Sternocleidomastoid

2. Splenius capitis


©Life Art

© Carone Learning

Ventilation

Muscles that aid with ventilation, or

breathing, include:

• Diaphragm

• External intercostals

• Internal intercostals


©Life Art

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muscles that act on the axial skeleton

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