• ipsilateral — muscle acts on the same side
• contralateral rotation — muscles acts to opposite side
Myology — the study of muscles
Muscles make up half of body’s weight.
3 types of muscles:
Skeletal - cover bones to make them move
Smooth - found internally. Lining of digestive tract, uterus, blood vessels. To propel stuff
through those tracts.
Cardiac - found only in heart.
Three types of muscles are specialized to form one very specific job — to take the chemical
energy of ATP and to convert it into the mechanical energy of motion.
1) Movement is the biggest function of muscles — move individual body parts, move body
contents, serves in communication (speaking, non-verbal communication via facial
expressions).
2) Stability — muscles help us to maintain an upright posture, maintain stability in our joints,
prevent us from falling or collapsing.
3) Control opening or closing of body passages. Example: controls opening or closing of our
mouth. Opening or closing eye. Internally, sphincter muscles of digestive tract help us to
regulate the passages of food particles.
4) Heat production. Muscles provide us with up to 85% of our body’s heat, so essential role
in maintaining the body’s metabolism.
Muscles generally attach to our bones by way of tendons. There’s basically a gap between the
muscle and the bones. Tendons (very thick connective tissue) bridge that gap. Most skeletal
muscles are attached to different bones on each end.
When the muscle contracts, it moves one bone relative to the other. So when we identify these
attachment points we call the stationary (non-moving) bone/attachment the origin. The
attachment to the moving bone is called the insertion.
Innervation — a muscle’s nerve supply. Without a nerve supply, a muscle cannot contract.
Two divisions — head-and-neck division + appendicular division. Muscles are innervated by 2
groups of nerves. Generally, the spinal nerves that exit via the vertebral column will innervate
skeletal muscles below the neck (like arms and legs). Cranial nerves arise from the brainstem
and generally innervate muscles of the head and neck.
Facial expression muscles: 10 muscles innervated by cranial or facial nerve VII:
• Frontalis (2) — cover portion of forehead, action: elevate eyebrow (draw scalp forward), Also
, wrinkles skin of forehead
• Occipitalis: (2) — covers occipital bone, retracts the scalp
• Orbicularis Oculi — circular muscle surrounding eyes, sphincter of eyelid, opening and
closing eyelid, blinking, squinting
• Orbicularis Oris — circular muscle around mouth; close lips, protrude lips forward,
presses lips against teeth
• Zygomaticus Major — laughing muscle, located in cheek region. Draw angle of mouth
upward and laterally. So if we look to identify our zygomaticus major.
• Depressor Labii Inferioris — located inferior to lips, will draw lower lips down and
laterally. Actions: help in chewing, and also expression of doubt.
• Levator Labii Superioris — located superior to lips (next to nose). Action is to
elevate and “evert” the lips in a sad or sneering-type expression.
• Buccinator (deep to masseter) — a chewing muscle. Compress cheek against teeth
so food stays where it needs to be when chewing.
• Mentalis — “mental” refers to the chin area, so this the muscle is found on the very tip of
the chin. Elevates and protrudes lower lip. For drinking, speaking, pouting expression,
wrinkles chin. On diagrams, always shown as a cut muscle since it is a superficial muscle
and need to show other muscles deep to it. (Very inferior on chin)
• Platysma — a large fan-like muscle covers the anterior surface of our neck. It works
to draw the lower lip down and the angle of the mouth downward in some expressions
like horror or surprise. Very superficial muscle.
TONGUE: Extrinsic tongue muscle group:
• Styloglossus — draw tongue upward and posteriorly. To help in chewing and
swallowing. Also for speech, in communication. Innervation is hypoglossal nerve.
• Hypoglossal Nerve: Cranial nerve located off of the brainstem. Innervates muscles of
the head-and-neck region.
• Hyoglossus — depresses tongue. When we swallow, we need tongue to move down, so
this muscle works to perform do that so food can be moved into the esophagus as we
swallow.
Innervation: hypoglossal nerve
MASTICATION muscles (chewing muscles):
• Temporalis — located above ear on lateral skull over temporalis bone. Elevate and
retract mandible (lower jawbone), and also lateral and medial movements (side to
side).
• Innervation — mandibular branch of the trigeminal nerve. (Trigeminal nerve is CNV)
• Masseter: elevates mandible, meaning to close mouth or bring lower jawbone up so the lips
meet. Also plays small role in lateral and medial movement of the mandible (move jaw left
and right). Also protraction and retraction (lower jaw forward and backward). All important in
chewing.
• Innervation — mandibular branch of the trigeminal nerve, CNV
NECK MUSCLES — innervated some by cranial, but mostly SPINAL nerves
• contralateral rotation — muscles acts to opposite side
Myology — the study of muscles
Muscles make up half of body’s weight.
3 types of muscles:
Skeletal - cover bones to make them move
Smooth - found internally. Lining of digestive tract, uterus, blood vessels. To propel stuff
through those tracts.
Cardiac - found only in heart.
Three types of muscles are specialized to form one very specific job — to take the chemical
energy of ATP and to convert it into the mechanical energy of motion.
1) Movement is the biggest function of muscles — move individual body parts, move body
contents, serves in communication (speaking, non-verbal communication via facial
expressions).
2) Stability — muscles help us to maintain an upright posture, maintain stability in our joints,
prevent us from falling or collapsing.
3) Control opening or closing of body passages. Example: controls opening or closing of our
mouth. Opening or closing eye. Internally, sphincter muscles of digestive tract help us to
regulate the passages of food particles.
4) Heat production. Muscles provide us with up to 85% of our body’s heat, so essential role
in maintaining the body’s metabolism.
Muscles generally attach to our bones by way of tendons. There’s basically a gap between the
muscle and the bones. Tendons (very thick connective tissue) bridge that gap. Most skeletal
muscles are attached to different bones on each end.
When the muscle contracts, it moves one bone relative to the other. So when we identify these
attachment points we call the stationary (non-moving) bone/attachment the origin. The
attachment to the moving bone is called the insertion.
Innervation — a muscle’s nerve supply. Without a nerve supply, a muscle cannot contract.
Two divisions — head-and-neck division + appendicular division. Muscles are innervated by 2
groups of nerves. Generally, the spinal nerves that exit via the vertebral column will innervate
skeletal muscles below the neck (like arms and legs). Cranial nerves arise from the brainstem
and generally innervate muscles of the head and neck.
Facial expression muscles: 10 muscles innervated by cranial or facial nerve VII:
• Frontalis (2) — cover portion of forehead, action: elevate eyebrow (draw scalp forward), Also
, wrinkles skin of forehead
• Occipitalis: (2) — covers occipital bone, retracts the scalp
• Orbicularis Oculi — circular muscle surrounding eyes, sphincter of eyelid, opening and
closing eyelid, blinking, squinting
• Orbicularis Oris — circular muscle around mouth; close lips, protrude lips forward,
presses lips against teeth
• Zygomaticus Major — laughing muscle, located in cheek region. Draw angle of mouth
upward and laterally. So if we look to identify our zygomaticus major.
• Depressor Labii Inferioris — located inferior to lips, will draw lower lips down and
laterally. Actions: help in chewing, and also expression of doubt.
• Levator Labii Superioris — located superior to lips (next to nose). Action is to
elevate and “evert” the lips in a sad or sneering-type expression.
• Buccinator (deep to masseter) — a chewing muscle. Compress cheek against teeth
so food stays where it needs to be when chewing.
• Mentalis — “mental” refers to the chin area, so this the muscle is found on the very tip of
the chin. Elevates and protrudes lower lip. For drinking, speaking, pouting expression,
wrinkles chin. On diagrams, always shown as a cut muscle since it is a superficial muscle
and need to show other muscles deep to it. (Very inferior on chin)
• Platysma — a large fan-like muscle covers the anterior surface of our neck. It works
to draw the lower lip down and the angle of the mouth downward in some expressions
like horror or surprise. Very superficial muscle.
TONGUE: Extrinsic tongue muscle group:
• Styloglossus — draw tongue upward and posteriorly. To help in chewing and
swallowing. Also for speech, in communication. Innervation is hypoglossal nerve.
• Hypoglossal Nerve: Cranial nerve located off of the brainstem. Innervates muscles of
the head-and-neck region.
• Hyoglossus — depresses tongue. When we swallow, we need tongue to move down, so
this muscle works to perform do that so food can be moved into the esophagus as we
swallow.
Innervation: hypoglossal nerve
MASTICATION muscles (chewing muscles):
• Temporalis — located above ear on lateral skull over temporalis bone. Elevate and
retract mandible (lower jawbone), and also lateral and medial movements (side to
side).
• Innervation — mandibular branch of the trigeminal nerve. (Trigeminal nerve is CNV)
• Masseter: elevates mandible, meaning to close mouth or bring lower jawbone up so the lips
meet. Also plays small role in lateral and medial movement of the mandible (move jaw left
and right). Also protraction and retraction (lower jaw forward and backward). All important in
chewing.
• Innervation — mandibular branch of the trigeminal nerve, CNV
NECK MUSCLES — innervated some by cranial, but mostly SPINAL nerves
