Muscular System

Axial Muscles

- originate on the axial skeleton
- support the head and spinal cord
- used in facial expressions, chewing and swallowing
- involved in breathing and the support and protection of abdominal and pelvic organs

Occipitofrontalis

- large muscle that covers the cranium
- raises eyebrows and wrinkles the forehead

Orbicularis Oculi

- circular muscle around the eye
- closes the eye

Orbicularis Oris

- circular muscle around the mouth
- compresses and purses the lips

Zygomaticus Major and Minor

- originate on the zygomatic bone and attach to the upper corner of the lip
- raise the mouth or lip

Platysma

- large muscular sheet over the neck that attaches to the bottom lip
- depresses the mandible

Masseter

- elevates the mandible
- one of the main chewing muscles that are responsible for the strength of the bite
- found on the jaw

Temporalis

- elevates the mandible
- one of the main chewing muscles that is responsible for the strength of the bite
- found above the ear

Medial Pterygoid

- move the mandible from side to side for chewing
- found lower down

Lateral Pterygoid

- move the mandible side to side for chewing
- found higher up

Buccinator

- compresses cheeks and assists in mastication
- found laterally to the lips

Digastric

- depresses the mandible
- found underneath the mandible

Hyoid Muscle Group

- elevate and depress the hyoid during swallowing or speech

Sternocleidomastoid

- one of two thick muscles running from the sternum and clavicle to the mastoid and occipital bone
- flexes the neck and turns the head obliquely to the opposite side

Scalenes

- flexes the neck

Splenius

- either of two flat muscles that extend from the upper vertebrae to the base of the skull
- extend the neck

Superior Oblique Eye Muscle

- originates from the sphenoid bone
- involved in intorsion
- moves the line of sight down and outward

Inferior Oblique Eye Muscle

- originates from the orbital floor
- extorts the eye
- moves the line of sight up and outward

Superior Rectus Eye Muscle

- top of the eye
- controls upward movement of the eye

Medial Rectus Eye Muscle

- medial side of eye
- moves the eye inward

Lateral Rectus Eye Muscle

- lateral side of the eye
- moves the eye outward

Inferior Rectus Eye Muscle

- bottom of the eye
- moves the eye downward

Spinalis

- one of the muscles that makes up the erector spinae
- extends the vertebral column and bends it sideways
- found above the transverse processes

Longissimus

- one of the muscles that make up the erector spinae
- extends the vertebral column and bends it sideways
- above and lateral to the transverse process

Iliocostales

- one of the muscles that makes up the erector spinae
- extends the vertebral column and bends it sideways
- thin sheet that arises on the ilium and inserts on the ribs

Transversospinalis

- responsible for local movements of the vertebral column and lateral bending
- connects and stabilizes the vertebrae
- can be called the intervertebral muscles

External Oblique

- allow the trunk to twist side to side
- found on each side of the rectus abdominis
- flat muscle

Transverse Abdominis

- stabilize the trunk and helps maintain internal abdominal pressure
- deepest of the flat muscles

Internal Oblique

- pair of muscles above the external obliques
- allow the trunk to twist and turn

Rectus Abdominis

- middle of the abdomen
- hold internal organs in place and stabilize the body during movement

Internal and External Intercostals

- important for forced breathing
- inhalation and exhalation

Diaphragm

- a muscular partition separating the abdominal and thoracic cavities
- functions in respiration, urination, defecation and childbirth
- main breathing muscle

Pelvic Floor

- consists of three layers known as the pelvic diaphragm
- controls urination, defecation and childbirth
- supports the pelvic organs
- erection and ejaculation

Appendicular Muscles

- move the upper and lower limbs
- stabilize the pectoral and pelvic girdle

Trapezius

- either of two flat triangular muscles of the shoulder and upper back
- involved in moving the shoulders and arms
- origin is the occipital bone and vertebrae
- insertion is the clavicle and scapula

Deltoid

- large triangular muscle covering the shoulder joint
- serving to abduct and flex and extend and rotate the humerus
- origin is the clavicle and scapula
- insertion is the humerus

Pectoralis Major

- adducts and rotates the arm
- origin at the ribs, sternum and clavicle
- insertion at the humerus

Brachialis

- flexion at the elbow
- origin at the humerus
- insertion at the ulna

Bicep Brachii

- flexion at the elbow
- origin at the scapula
- insertion at the radius

Brachioradialis

- flexion at the elbow
- origin at the humerus
- insertion at the radius

Pronator Group

- pronation of the forearm

Supinator

- supination of the forearm

Flexors Carpi and Flexors Digiti

- flexes the wrist

Extensors Carpi and Extensors Digiti

- extends the wrist

Rotator Cuff Muscles

- group of four muscles that provide the range of motion for the shoulder
- origin at the scapula
- insertion at the humerus

Tricep Brachii

- extension at the elbow
- origin at the humerus and scapula
- insertion at the ulna

Latissimus Dorsi

- broad flat muscle on either side of the back
- extends the humerus
- origin at the vertebrae
- insertion at the humerus

Rhomboid Group

- elevates and adducts the scapula
- origin at the vertebrae
- insertion at the scapula

Iliapsoas

- consists of the psoas major and iliacus
- flexes the thigh

Sartorius

- muscle in the thigh (tailor muscle)
- rotate and flex the leg
- origin at the ilium
- insertion at the tibia

Rectus Femoris

- one of the muscles that makes up the quadriceps and patellar ligament
- extends the leg
- origin at the ilium and femur
- insertion at the tibia
- spans the hip and knee joint

Vastus Lateralis

- one of the muscles that make up the quadriceps and patellar ligament
- extends the leg
- origin at the ilium and femur
- insertion at the tibia
- largest quad muscle found on the outside of the thigh

Vastus Intermedius

- one of the muscles that makes up the quadriceps and patellar ligament
- extends the leg
- origin at the ilium and femur
- insertion at the tibia
- middle of the thigh beneath the rectus femoris

Vastus Medialis

- one of the muscles that makes up the quadriceps and patellar ligament
- extends the leg
- origin at the ilium and femur
- insertion at the tibia
- smallest of the quad muscles that runs inside the thigh

Gracilis

- flexes and adducts the thigh
- origin at the pubis
- insertion at the tibia

Gluteal Group

- consists of the gluteus maximus, medius and minimus
- extends and abducts the thigh

Hamstrings

- consists of the semitendinosus, biceps femoris and semimembranosus
- flexes the lower leg
- origin at the ischium
- insertion at the fibula and tibia

Tensor Fascia Latae

- abducts the thigh
- stabilizes the hip and knee joints by putting tension on the iliotibial band

Gastrocnemius

- muscle in the back part of the leg
- responsible for the plantar flexion of the foot
- origin at the femur
- insertion at the calcaneus

Soleus

- broad flat muscle in the calf of the leg under the gastrocnemius muscle
- plantar flexes the foot
- origin at the tibia and fibula
- insertion at the calcaneus

Tibialis Anterior

- dorsiflexes the foot

IT Band

- slides back and forth over the distal portion of the femur

Functions of the Muscular System

- movement
- stabilization
- heat generation
- movement of substances
- communication (facial expressions)

Striated Muscle Tissue

- muscle tissue characterized by transverse stripes
- includes skeletal and cardiac muscle

Skeletal Muscle

- voluntary muscles
- striated
- some subconscious control
- one nerve, one artery and one or two veins

Cardiac Muscle

- found only in the heart
- involuntary
- striated
- single cells
- consists of many cells joined together at intercalated discs

Smooth Muscle

- lacks striations
- involuntary
- urinary bladder, uterus, intestines
- eye, circulatory vessels, respiratory tubes
- actin and myosin not arranged in neat rows
- spindle-shaped cell with one central nucleus
- contractile myofilaments lie at a slightly oblique angle

Fascicles

- bundles of fibers that make of muscle

Fibers

- make up fascicles

Myofibrils

- smaller fibers that make up each (cell)

Actin

- make up myofibril
- thin filament surrounding each end

Myosin

- make up myofibril
- middle thick filament

Myoblasts

- fuse together to become myocytes

Sarcolemma

- surrounds the sarcoplasm

Sarcomere

- basic unit of muscle contraction
- each muscle has many
- boundaries cause the striations

Myocardium

- muscular heart wall

Load

- external force that opposed the force of the muscle

Isotonic Contraction

- force of the muscle is greater than the load

Isometric Contraction

- load is greater than the force of the muscle

Origin

- attachment to the more stationary element

Insertion

- attachment to more mobile element

Levator Scapulae

- origin at the cervical vertebrae
- insertion at the scapula

Parallel Muscle

- entire muscle shortens by 30%
- example is the sternocleidomastoid

Fusiform Muscle

- narrow tendons at each end
- exerts great force at each end
- example is the bicep brachii

Circular Muscle

- useful for closing an orifice
- example is the orbicularis oculi

Convergent Muscle

- muscle fibers over broad area
- come together at common attachment site
- can pull in multiple directions
- example is the pectoralis major

Pennate

- has one or more tendons running through the body of the muscle
- contains more muscle fibers per unit area meaning it can generate more force
- rectus femoris, deltoid

Prime Mover (Agonist)

- muscle that contracts during the movement

Synergyst

- muscle that assists the agonist

Antagonist

- muscle that opposes the actions of the agonist