Muscular System (LAB)

epimysium

dense irregular connective tissue (with varying irregularity) that transitions to dense regular connective tissue that surrounds groups of fascicles

perimysium

mix of dense irregular tissue and areolar connective tissue that surrounds the fascicle

endomysium

areolar connective tissue that surrounds individual muscle fibers

sarcolemma

muscle cell membrane

sarcoplasm

cytoplasm of muscle cells

muscle fiber

muscle cell

sarcoplasmic reticulum

specialized smooth endoplasmic reticulum in muscle cells that stores and releases calcium

fascicle

discrete bundle of muscle cells

myofibril

rod-like contractile element of muscle cells that are composed of many sarcomeres

sarcomere

contractile unit of muscle cells that is composed of myofilaments

myofilaments

actin (thin) and myosin (thick)

A-band

dark colored portion of the sarcomere that contains the full length of myosin filaments and overlapping actin filaments

I-band

light colored portion of the sarcomere that contains only actin filaments and is intersected by the Z-disc

Z-disc

thin, dark boundary within muscle cells that marks the end of each sarcomere and anchors actin filaments

terminal cisternae

sacs on the sarcoplasmic reticulum that store calcium

transverse (T) tubule

extensions of the sarcolemma where action potential travel down to other parts of the cell

motor end-plate

component of the neuromuscular junction that receives neurotransmitters and converts it into an electrical signal for muscle contraction

axon terminal

enlarged end of a neurons axon where neurotransmitters are stored and released

pre-synaptic vesicles

small, membrane-bound organelles that store and mediate the release of neurotransmitters at the synapse

synaptic cleft

space between two neurons that allows neurotransmitter diffusion and signal transmission

skeletal muscle traits

• striated

• voluntary

• attached to bones and skin

• multinucleated

cardiac muscle traits

• striated

• involuntary

• only in the heart

• 1-2 nuclei

smooth muscle traits

• unstriated

• involuntary

• in hollow organs of GI tract, blood vessels, bronchi, arrector pilli muscles of skin, and intrinsic eye muscle

• unnucleated

occipitofrontalis (epicranius)

bipartite muscle of the scalp consisting of frontal and occipital bellies connected by the epicranial aponeurosis

occipitofrontalis (epicranius) frontal belly origin

epicranial aponeurosis

occipitofrontalis (epicranius) frontal belly insertion

skin of eyebrows and root of nose

occipitofrontalis (epicranius) frontal belly function

raising eyebrows and wrinkling forehead

occipitofrontalis (epicranius) occipital belly origin

occipital and temporal bones

occipitofrontalis (epicranius) occipital belly insertion

epicranial aponeurosis

occipitofrontalis (epicranius) occipital belly funtion

fixes aponeurosis and pulls scalp posteriorly

muscles of the face

• orbicularis oculi

• zygomaticus

• risorius

• orbicularis oris

• levator labii superioris
  depressor labii inferioris

• depressor anguli oris

• mentalis
  buccinator

muscles of mastication

• masseter

• temporalis

• medial pterygoid

• lateral pterygoid

• buccinator

muscles promoting tongue movement (also throat muscles)

• genioglossus

• hyoglossus

• styloglossus

muscles of the throat

• digastric

• mylohyoid

• geniohyoid

• omohyoid

• sternohyoid

• sternothyroid

• thyrohyoid

orbicularis oculi

thin, flat sphincter muscle of eyelid that surrounds the rim of the orbit

orbicularis oculi insertion

tissue of eyelid

orbicularis oculi origin

frontal and maxillary bones and ligament around orbit

orbicularis oculi function

closes eyes

zygomaticus

muscle pair extending diagonally from cheekbone to corner of mouth

zygomaticus function

raises lateral corners of mouth

zygomaticus origin

zygomatic bone

zygomaticus insertion

skin and muscle at corner of mouth

orbicularis oris

complicated, multilayered muscle of lips with fibers that run in many different directions (most run circulatory)

orbicularis oris origin

arises indirectly from maxilla and mandible

orbicularis oris insertion

encircles mouth, inserting into muscle and skin at angles of mouth

orbicularis oris function

closes lips

risorius

slender muscle inferior and lateral to zygomaticus

risorius origin

lateral fascia associated with masseter muscle

risorius insertion

skin at angle of mouth

risorius function

draws corners of lips laterally

buccinator

thin, horizontal cheek muscle; principle muscle of cheek

buccinator origin

molar region of maxilla and mandible

buccinator insertion

orbicularis oris

buccinator function

compresses cheek

levator labii superioris

thin muscle between inferior eye margin and orbicularis oris

levator labii superioris origin

zygomatic bone and infraorbital margin of maxilla

levator labii superioris insertion

skin and muscle of upper lip

depressor labii inferioris

small muscle running from mandible to lower lip

depressor labii inferioris origin

body of mandible lateral to its midline

depressor labii inferioris insertion

skin and muscle of lower lip

depressor labii inferioris function

draws lower lip inferiorly (pout)

depressor anguli oris

small muscle lateral to depressor inferioris

depressor anguli oris origin

body of mandible below incisors

depressor anguli oris insertion

skin and muscle at the angle of the mouth below the insertion of the zygomaticus

depressor anguli oris function

draws corners of the mouth down laterally

mentalis

one of the muscle pairs forming a V-shaped muscle mass on the chin

mentalis origin

mandible below incisors

mentalis insertion

skin of chin

mentalis function

wrinkles chin

masseter

powerful muscle of mastication that covers the lateral aspect of the mandibular ramus

masseter origin

zygomatic arch and bone

masseter insertion

angle and ramus of mandible

masseter function

prime mover of jaw closure

temporalis

fan-shaped muscle that covers parts of the temporal, frontal, and parietal bones

temporalis origin

temporal fossa

temporalis insertion

coronoid process of mandible via a tendon that passes deep to zygomatic arch

temporalis function

closes jaw

medial pterygoid

deep two headed mastication muscle that runs along the internal surface of the mandible and is largely concealed by that bone

medial pterygoid origin

medial surface of lateral pterygoid plate of sphenoid bone, maxilla, and palatine bone

medial pterygoid insertion

medial surface of mandible near its angle

medial pterygoid function

acts with lateral pterygoid muscle to protract (pull anteriorly) the mandible and promote grinding movements

lateral pterygoid

deep two headed mastication muscle that lies superior to medial pterygoid muscle

lateral pterygoid origin

greater wing and lateral pterygoid plate of sphenoid bone

lateral pterygoid insertion

condylar process of mandible and capsule of temporomandibular joint

lateral pterygoid function

provides forward sliding and grinding movements of the lower teeth

genioglossus

fan shaped muscle that forms the bulk of the inferior part of the tongue

genioglossus origin

internal surface of mandible near symphysis

genioglossus insertion

inferior aspect of the tongue and body of hyoid bone

genioglossus function

protracts tongue

hyoglossus

flat, quadrilateral muscle

hyoglossus origin

body and greater horn of hyoid bone

hyoglossus insertion

inferolateral tongue

hyoglossus function

depresses tongue

styloglossus

slender muscle that runs superior to and at right angles to hyoglossus

styloglossus origin

styloid process of temporal bone

styloglossus insertion

inferolateral tongue

styloglossus function

retracts and elevates tongue

digastric

consists of 2 bellies united by an intermediate tendon, forming a V-shape under the chin

digastric origin

lower margin of mandible and mastoid process

digastric insertion

by a connective tissue loop to hyoid bone