BIOL1711- Muscular System

What three connective tissue layers merge to form tendons

Epimysium, perimysium, and endomysium

Structure and function of tendons

Thick and cord like, attaches the muscle to bone, skin, or another muscle

Origin

The immovable or less movement attachment

Insertion

The movable attachment

In the muscles moving the axial skeleton, what tends to be the more moveable attachment?

The superior attachment, as the superior portion of the body is pulled toward the inferior portion when muscles contract

In the muscles moving the appendicular skeleton, what tends to be the more moveable attachment?

The distal attachment, as the distal attachment moves toward the proximal attachment during muscle contraction

Agonist

Also called the prime mover, is a muscle that contracts to produce a particular movement

Antagonist

A muscle whose actions oppose the agonist.

Synergist

A muscle that assists the agonist in performing its action. Usually most useful at the start of a movement

In muscle naming, what does “rectus” indicate?

The muscle fibre orientation is straight

In muscle naming, what does “oblique” indicate?

The muscle fibre orientation is angled

In muscle naming, what does “orbicularis” indicate?

The muscle fibre orientation is circular

Deltoid

Muscle shape that is triangular

Quadratus

Muscle shape that is rectangular

Trapezius

Muscle shape that is trapezoidal

Longus

Muscle shape that is long

Brevis

Muscle shape that is short

In muscle naming, what does “major” indicate?

It is the lager of the two muscles

In muscle naming, what does “minor” indicate?

It is the small of two muscles

In muscle naming, what does “maximus” indicate?

Largest muscle

In muscle naming, what does “medius” indicate?

Medium sized muscle

In muscle naming, what does “minimus” indicate?

Smallest muscle

Bicep

Muscle has 2 heads

Tricep

Muscle has 3 heads

Quadricep

Muscle has 4 heads

What are most of the facial muscles innervated by?

The seventh cranial nerve

How do facial muscles work?

They generally attach from the subcutaneous layer or skill bones to the skin, and when these muscles contact they pull on the skin causing it to move

Fixators

Muscles that stabilize the origin of the prime mover

What is the muscles of the epicranius?

Occipitofrontalis muscle

What muscle do we see in section B, and what part of this specific muscle is it called

Occipitofrontalis muscle; occipital belly

What muscle do we see in section A, and what part of this specific muscle is it called

Occipitofrontalis muscle; frontal belly

Contraction of frontal belly

Raised eyebrows and wrinkling of forehead, moving the scalp slightly

Contraction of the occipital belly

Retracts the scalp

What connects the occipital and frontal bellies

The epicranial aponeurosis (or galea aponeurotica), a sheet like tendon composed of dense regular connective tissue

Contraction of corrugator supercilii

Draws eyebrows together and forms vertical wrinkled lines around the nose

Corrugator supercilii

Ridged and grooved muscle that sits above the eyebrows

Orbicularis oculi

Circular muscle fibres that surround the eye’s orbit

Contraction of orbicularis oculi

Causes eyelid to close (e.g., blink, wink, squit)

Contraction of the levator palpebrae superioris

Elevates the upper eyelid when you open your eyes

Levator palpebrae superioris

Originates on the lesser wing of the sphenoid and inserts into the upper eyelid

Nasalis

Located on each wing of the nostril

Contraction of nasalis muscle

Elevates corners of nostrils to flare your nose

Orbicularis oris

Muscle fibres that encircle the opening of the mouth

Contraction of orbicularis oris

Closes lips, kissing/puckering of lips, speech

Depressor labii

Pulls the lip inferiorly

Depressor anguli oris

Frown muscle, pulls the corner of the mouth inferiorly

Note: takes more than one muscle to frown

Levator labii superioris

Elevates the upper lip superiorly, like when sneering or snarling

Levator anguli oris

Pulls the corners of the mouth superiorly and laterally

Zygomaticus major and minus

Works with levator anguli oris muscles, draws angle of mouth (corners of the lips) up and out as in smiling or laughing

Risorius

Pulls corners of the lips laterally, like when you make a closed mouth smile

Mentalis

Protrudes the lower lip, like when you pout

Platysma

Origin: clavicular region

Insertion: mandible cheek

Contraction of platysma

Depresses the mandible (like when we chew), and gives a tense neck appearance (if you do not depress the mandible)

Buccinator

Major lateral cheek muscle and compresses the cheek against the teeth when we chew or cheeks to cave in when sucking

Also called the milkshake muscle or trumpeters muscle

Name the extrinsic eye muscles

Four rectus muscles (medial, lateral, inferior, superior) and two oblique muscles (inferior and superior)

Insertion of the extrinsic eye muscles

Sclera (outer white surface of the eye)

Origin and insertion of the four rectus muscles

Origin: common tendinous ring in the orbit/orbit bones

Insertion: Anterior part of the eye

Medial rectus

Pulls the eye medially

Lateral rectus

Pulls the eye laterally

Superior rectus

Pulls the eye superiorly and medially

Inferior rectus

Pulls the eye inferiorly and medially

Origin and insertion of oblique eye muscles

Origin: orbital bones

Insertion: posterolateral part of the sclera of the eye

Inferior oblique

Attaches at the inferior posterior part of the eye. Pulls the back of the eyeball down, but elevates the anterior part of the eye and turns it laterally

Superior oblique

Muscle passes through the trochlea (pulley-like loop) in the anteromedial orbit

Attaches at the superior posterior part of the eye. Pulls the back of the eyeball superiorly, but depresses the anterior part of the eye and turns it laterally

Mastication

Process of chewing

What muscles are involved in mastication?

Four paired muscles: the temporalis, masseter, medial and lateral pterygoids

Temporalis

Origin: parietal bone

Insertion: mandible

Elevates and retracts the mandible

Masseter

Origin: zygomatic bone

Insertion: mandible

Elevates and retracts the mandible, most powerful and important chewing muscle

Pterygoids

Origin: pterygoid processes of the sphenoid bone

Insertion: mandible

Protract the mandible and move it from side to side during chewing

Muscles of tongue movement

3 paired muscles: genioglossus, hyoglossus, styloglossus

Genioglossus

Protracts the tongue, used when we stick our tongue out

Styloglossus

Elevate and retract the tongue

Hyoglossus

Depress and retract the tongue

Suprahyoid muscles

Muscles of the anterior neck that are superior to the hyoid bone. Associated with the floor of the mouth and elevates the hyoid bone during swallowing and speaking

Includes the digastric, stylohyoid, mylohyoid, and geniohyoid

Infrahyoid muscles

Muscles of the anterior neck that are inferior to the hyoid bone, depresses hyoid bone and the larynx after swallowing.

Includes the thyrohoid, sternothyroid, sternohyoid, and omohyoid

Sternocleidomastoid muscle

Origin: sternum and clavicle

Insertion: temporal bone (mastoid process)

Are located on either side of the neck (anterior neck muscle). Bilateral contraction (contraction of both muscles) causes head/neck flexion, unilateral (contraction of one muscle) contraction laterally flexes the neck and rotates the face in opposite direction

What is the sternocleidomastoid the prime mover of?

Head flexion

What are synergists to head flexion, and therefore the sternocleidomastoid muscle

Suprahyoid and infrahyoid muscles

Scalenes muscles

Anterior neck muscle. 3 muscles (anterior, middle, and posterior). Work with sternocleidomastoid to laterally flex the neck, and elevate the second and first rib during inspiration

Splenius capitis and cervicis

Posterior neck muscles. Prime mover of head extension, and antagonist to sternocleidomastoid muscle.

Semispinalis capitis

Synergist to sternocleidomastoid in terms of head rotation. Pulls from the back on the turning side of the head.

Erector spinae muscles

Iliocostalis muscles, longissimus muscles, and spinalis muscles

All function to extend the vertebral column during bilateral contraction, as well as lateral flexion during unilateral contraction. Muscle fibres run vertically.

Iliocostalis muscles

Most lateral located, attached to the iliac crest and ribs

Longissimus muscles

In between the other two erector spinae muscles, attached to the transverse processes of the vertebrae

Spinalis muscles

Most medially located, attach to spinous processes of the vertebrae

Quiet breathing

Normal, relaxed breathing that happens automatically without conscious thought while at rest.

Forced breathing

Deeper, faster, or harder breathing that occurs during exercise, singing, or physical exertion

What is the most important muscle associated with breathing?

Diaphragm

Muscles of quiet breathing

External intercostals and the diaphragm

Where do the muscle fibres of the diaphragm converge toward?

Central tendon

Quiet inspiration

Diaphragm contracts and central tendon is pulled inferiorly, external intercostals contract

Leads to expansion of the chest wall and lungs, as well as the expansion of the ribs, and sternum moves upward and outward

External intercostals

Origin: inferior surface of the superior rib

Insertion: superior surface of the inferior rib

Action: pulls each rib upwards to increase ribcage

Quiet expiration

Diaphragm relaxes and central tendon is pulled back up, external intercostals relax

Leads to contraction of the chest cavity and lungs, the rib cage gets smaller, and the ribs and sternum depresses

Forced inspiration

External intercostals contract more forcefully, the scalenes contract and elevate the first and second ribs, and the sternocleidomastoid muscles contact to move the sternum anteriorly.

On the posterior side, serratus posterior superior elevates the ribs 2-5 to increase the lateral dimensions of the thoracic cavity

Forced expiration

External intercostals relax, internal intercostals depress the ribs, transcersus thoracic depresses ribs 2-6, serratus posterior inferior depresses ribs 8-12, and abdominal muscles contract pulling rib cage inferiorly and compress the abdominal cavity forcing the diaphragm into a higher dome position

Internal intercostals

Origin: superior surface of the inferior rib

Insertion: inferior surface of the superior rib

Action: pulls each rib down to decrease ribcage

Serratus posterior superior

Origin: C7-T3 vertebrae

Insertion: ribs 2-5

Action: elevates posterior ribs during forced inhalation

Serratus posterior inferior

Origin: T11-L2 vertebrae

Insertion: Ribs 8-12

Action: depresses posterior ribs during forced exhalation

What muscles reinforce the anterolateral wall of the abdomen

External oblique, internal oblique, transverse abdominis, and rectus abdominis

External oblique

Superficial, muscle fibres run inferomedially, located right above the iliac crest

Rotates and flexes the spine