Muscular System

Axial Muscles

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