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Skeletal muscles

attach to bones

Main function of skeletal muscles is

contracting to facilitate movement of our skeletons.

Skeletal muscles are also known as

striated muscles due to their appearances. The cause of this stripy appearance is the bands of Actin and Myosin which form the sarcomere, found within the Myofibrils.

Bands of Actin and Myosin form the


Skeletal muscles are sometimes called

voluntary muscles because we have direct control over them through nervous impulses from our brains sending messages to the muscle.

Skeletal muscles have the ability to

stretch or contract and still return to their original shape.

Smooth muscle is also known as

involuntary muscle due to our inability to control its movements, or unstriated as it does not have the stripy appearance of skeletal muscle.


doesn't have the stripy appearance of skeletal muscle.

*Smooth muscle is found in the walls of hollow organs such as the

*stomach, oesophagus, bronchi, and in the walls of blood vessels.

Smooth muscle is stimulated by

involuntary neurogenic impulses and has slow, rhythmical contractions used in controlling internal organs, (Example: moving food along the oesophagus or constricting blood vessels during vasoconstriction.)

Cardiac muscle is found solely in the

wall of the heart.

Cardiac muscle is similar to

skeletal muscle in that its striated and like smooth muscle because its involuntary (its contractions are not under conscious control). It's a mixed muscle.

A highly specialized muscle is

the cardiac muscle.

*Cardiac muscle is highly resistant to fatigue due to the presence of a large number of

*mitochondria (powerhouse of the cell), myoglobin and a good blood supply allowing continuous aerobic metabolism.

Each cardiac muscle fiber contains hundreds to thousands, cylindrical organelles known as


Myofibrils are bundles of

Actin and Myosin proteins which run the length of the muscle fiber and are important in muscle contraction.

Sarcoplasmic Reticulum

a network of tubules and channels that surround the Myofibril. *In this calcium is stored which is important in muscle contraction.

The main element of muscle contraction is


Ligaments connect

bone to muscle.

Tendons connect

bone to bone

Sliding Filament Theory

each muscle fiber is made up of smaller fibers called myofibrils. These contain even small structures called actin and myosin filaments. These filaments slide in and out between each other to form muscle contracts, hence called the sliding filament theory.


Part of a myofibril. *It is the smallest unit of skeletal muscle that can contract. They repeat themselves over and along the length of the myofibril.

*The smallest unit of skeletal muscle that can contract is the


Ear muscles:

1. Anterior Auricular muscle
2. Superior Auricular muscle.

Anterior Auricular muscle

Origin: from connective tissue of the scalp in front of the ear.
Insertion: runs posteriorly into the anterior part of the ear.
Action: pulls the ear slightly forward.

Superior Auricular muscle

Origin: from connective tissue of the scalp above the ear.
Insertion: runs down and inserts into upper part of ear.
Action: raises the ear.

Scalp muscles:

1. Occipitofrontalis/epicranius. It is a paired muscle. Anterior and posterior fibers connected by fascia (muscular tissue).


Origin: from connective tissue of scalp.
Action: forward movement of scalp as in a frown /squint and backward movement as in surprise.

Neck muscle:

1. Platysma


upper end of fibers attach to inferior border of mandible, near angles of the mouth and skin of the face in that area. End in a flat sheet in the skin of the chest area just below the clavicle.
Action: pulls down corner of the mouth as in a grimace.

Eye muscles:

1. Orbicularis oculi (orbital part and palpebral part)
2. Levator palpebrae superioris muscle
3. Corrugator
4. Procerus

Orbicularis oculi

Has two parts. Part that circles the eye: orbital part
Action: closes the eyelid
Muscles in the eyelid: palpebral part.
Action: contracts skin around the eye

Levator palpebrae superioris muscle

Origin: back of the orbit
Insertion: eyelid
Action: raises the upper eyelid


Origin: bridge of the nose.
Insertion: lateral to the lateral part of eyebrow
Action: pulls the eyebrow medially and down as in a frown.


Origin: bridge of the nose
Insertion: medial end of eyebrow
Action: pull the eyebrow at the medial end down as in a frown or a squint.

Nose muscles:

1. nasalis
2. Levator labii superioris alaeque nasi.


Has two parts. Dilator Naris: pulls down on nostrils, causing them to flare or dilate.
Compressor Naris: closes or compresses nostrils.

Major nose muscle

Levator labii superioris alaeque nasi

Functions of the mouth

influences expression, aids in speech, aids in mastication, holds teeth in alignment

Mouth Muscles:

1. Orbicularis Oris
2. Levator Labii Superioris
3. Zygomatic Minor
4. Zygomatic Major
5. Levator Anguli Oris
6. Depressor Angule Oris
7. Depressor Anguli Oris
8. Mentalis
9. Buccinator

Orbicularis Oris

circles the oral cavity in the lip, attachment at the anterior nasal spine and at the midline above the chin.

Action: to close and compress the lips

Levator Labii Superioris

Origin: beneath the lower rim of the orbit.

Insertion: into fibers of orbicularis oris of the upper lip, midway between the center of the lip and the corner of the mouth (muscle inside a muscle).

Action: elevates the upper lip.

Zygomatic Minor

Origin: zygomatic bone.

Insertion: into orbicularis oris just lateral to the levitator labii superiors.

Action: raises upper lip.

Zygomatic major

Origin: zygomatic bone lateral to zygomaticus minor on the most prominent portion of the cheek.

Insertion: into orbicularis oris at the angle of the mouth.

Action: elevates corners of the mouth in a smile.

Levator Angulii Oris

Origin: from maxilla, just below the infraorbital foramen.

Insertion: blends into orbicularis oris at the corners of the mouth.

Action: pulls angles of the mouth up and toward the midline.

Depressor Labii Inferioris

Origin: area beneath the angles of the mouth, just above the inferior border of the mandible.

Insertion: into orbicularis oris toward the middle of the lower lip.

Action: pulls lower lip down in a pout.

Depressor Angulii Oris

Origin: area beneath the angles of the mouth, just above the inferior border of the mandible.

Insertion: converge in a triangle into orbicularis oris at the angle of the mouth.

Action: pulls the corners of the mouth down.


Origin: anterior surface of the mandible just beneath the lateral incisors.

Insertion: run down, towards midline, cross to meet muscle on the opposite side and insert into the skin of the chin.

Action: pulls the skin up.


Origin: 1. from pterygomandibular raphe (fibrous band) 2. Buccal alveolar bone of the maxillary and mandibular molars

Insertion: orbicularis oris on the corners of the mouth.

Action: on contraction it pulls the corners of the mouth back and compresses the cheek, Chewing food.


Origin: soft tissue near the angle of the mouth.

Insertion: corner of the mouth.

Action: helps to smile.

Buccinator - muscle of mastication

It arises from the outer surfaces of the alveolar processes of the maxilla and mandible, corresponding to the three molar teeth; and behind, from the anterior border of the pterygomandibular raphe.
The fibers converge toward the angle of the mouth, where the central fibers intersect each other, at the Orbicularis oris.

Action: on contraction, it pulls back the angle of the mouth and to flatten the cheek area. This helps in pushing the food back onto the occlusal surfaces of the teeth from the buccal vestibule during chewing.

Most important muscle of mastication is the



Motor innervation is from the buccal branch of the facial nerve facial nerve (cranial nerve VII)
Sensory innervation is from the buccal branch of the Mandibular branch of Trigeminal Nerve.

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