Ch.11 - Muscles

95 to remember! Assume Agonist if not stated otherwise. L = Location, A= Action, O = origin, I = Insertion, PM = Prime Mover (more specific than agonist)

How does reversing muscle action work?

Muscles can’t undo their own actions, only other muscles can. Muscles on opposite sides will oft have opposite functions. Likewise, if muscles are in different compartments, they’ll usually have different functions.

Ex: Pectoral Major Dorsi will flex, Latissimus Dorsi will extend

Difference between prime mover and agonist

All prime movers are agonists, but not all agonists are prime movers. Prime movers will be the main muscle and there’s usually only ONE dominant muscle. There can be multiple agonists for a single movement.

Ex: Agonists ~ Biceps Brachii, Brachialis, brachioradialis VS PM ~ Biceps Brachii

Corrugator Supercilii

L = Above eyebrows, deep to orbicularis oculi

A = draws eyebrows in, frowning

Orbicularis Oculi

L = full circle in orbital region

A = closes eyes

Zygomaticus (major + minor)

L = from zygomatic bone to mouth 

A= corners of lips UP and LATERAL, :) 

Risorius

L = looks like small muscle going from masseter → oris

A = synergist to zygomaticus :)

Depressor Anguli Oris 

L = below mouth, on the sides of chin

A = antagonist to zygomaticus, draws lips laterally, :(

Orbicular Oris

L =surrounds oral cavity

A = closes mouth

Orbicularis

full circle

Oris

relating to the mouth

Buccinator 

L = wall of the cheek

A= compresses cheeks, to whistle or suckle

Platysma

L = spans from mandible to clavicle

A = tenses neck muscles

Masseter

O = Zygomatic Bone + Arch 

I = Mandible

A = PM ; Jaw closure, mastication

Temporalis

O = = temporal fossa

I = Mandible

A = jaw closure, mastication

Medial/Lateral Pterygoid:

L = deep, can’t be seen on model

A = grinding food, side-to-side chewing

Brevis

short

Pharyngeal* constrictor muscles  

*Pharynx = throat

A = contract sequentially downward to swallow

Muscles of Mastication (ID 5):

Masseter, Temporalis, Medial Pterygoid, Lateral Pterygoid, Pharyngeal Constrictor

Sternocleidomastoid

*Sternum, Clavicle, Mastoid (zygomatic bone)

O = manubrium + clavicle

I = mastoid process + occipital bone

A = flexes laterally, PM: head flexion

Scalenes

O = vertebrae

I = ribs 1+2

A = Synergist for inhalation/inspiration, helps w breathing

Intrinsic Muscles of the back [ID 5]:

L = deep in back

A = extend trunk, vertebrae/spine

Includes: [Iliocostalis, Longissimus, Spinalis], Splenius, Semispinalis (deep)

Splenius 

L = deeper than the trapezius

A = antagonist to sternocleidomastoid, extends head

Erector Spinae:

L = L → M, Iliocostalis, Longissimus, Spinalis

A = same as intrinsic muscles of the back

I love spaghetti!

Quadratus Lumborum

L = deep in posterior wall

A= flex vertebral column

External Intercostals:

L: w/in rib cage and most superficial; going diff. direction than other intercostals

A = synergist to diaphragm; lifts ribcage for inhalation

Internal Intercostals

L = w/in rib cage and deeper; going diff. direction than other intercostals 

A = synergist to inner intercostals, aids expiration

Diaphragm

L = between thoracic vertebrae and top of lumbar vertebrae

A = PM for inspiration

Semispinalis

L = NOT part of the Erector Spinae, deep neck muscle

A = extends trunk, vertebrae/spine

Deep muscles of the thorax (ID 3):

External Intercostals, Internal Intercostals, Diaphragm

Muscles of the Abdominal Wall (4):

External Oblique, Internal Oblique, Transversus abdominis, Rectus Abdominis 

*No bony attachment

Muscles of the face (ID 8): 

Corrugator Supercilii, Orbicularis Oculi, Zygomaticus, Risorius, Depressor Anguli Oris, Orbicularis Oris, Buccinator, Platysma

Anterolateral Neck Muscles (ID 2):

Sternocleidomastoid and Scalenes

Rotator Cuff:

• teres minor

• supraspinatus

• infraspinatus 

• subscapularis

(!) NOT THE TERES MAJOR, EVEN IF TERES MINOR HAS SOME O AND I 

External Oblique:

L = found infroolaterally and supromedially

A = antagonist to vertebral spine; flex vertebral column + compress wall

Posterior View of RC:

Infraspinatus:

O - infraspinous fossa

I = greater tubercle

Supraspinatus:

O - supraspinous fossa

I = lesser tubercle

Teres Minor

O - pectoral girdle

I = humerus

(!) All subscapularis shares I w/ supraspinatus