I) Muscle Mechanics

A) Lever Systems: Bone-Muscle Relationships
     1. bones & muscles operates as levers to create motion
     2. depending upon the position of the effort, fulcrum and resistance ... there are 3 types
          a. first-class levers
               i. effort and resistance are on opposite sides of the fulcrum
               ii. an example would be lifting your head off of your chest
          b. second-class levers
               i. the resistance is between the effort and the fulcrum
               ii. an example would be the act of standing on your toes
          c. third-class levers
               i. the effort is between the resistance and the fulcrum
               ii. an example would be the biceps flexing the arm

C) Muscle Interactions
     1. muscles work by contracting (pulling) ... nevery by pushing
     2. the insertion is the attachment of a muscle on the movable bone
     3. the origin is the attachment of a muscle to its fixed or immovable point of attachment
     4. muscles can be classified into four functional groups
          a. prime mover (agonist) - the muscle that provides the major effort in movement
          b. antagonist - muscle that opposes the motion of the prime mover
          c. synergists - muscles that help other muscles
          d. fixators - muscles that immobilize a bone

D) Naming Skeletal Muscles - muscles are named for a variety of reasons
     1. location of the muscle - ie. the frontalis is over the frontal bone
     2. shape of the muscle - ie. the trapezius is roughly in the shape of a trapezoid
     3. relative size of the muscle - ie. the gluteus maximus is the largest of 3 gluteal muscles
     4. direction of muscle fibers - ie. the oblique muscles run diagonally
     5. number of origins - ie. the triceps have 3 origins
     6. location of the muscle's origin and/or insertion - ie. the extensor digitorum inserts into the digits
     7. action of the muscle - ie. the adductor magnus acts to adduct the leg

II) Major Muscles of the Body
          NOTE: Anterior & posterior diagrams with the major muscles are at the bottom of this page.

A) muscles of the scalp
     1. epicranius
          a. frontalis - over the frontal bone; furrows the forehead
          b. occipitalis - over the occipitalis bone

B) muscles of the face
     1. corrugator supercilii - over the eyebrows; pulls the eyebrows medially
     2. orbicularis oculi - around the eye; for winking
     3. zygomaticus - from the zygomatic bone to the corner of the mouth; helps you smile
     4. risorius - horizontal muscle from the corner of the mouth extending laterally
     5. levator labii superioris - from below the eye to the upper lip; lifts the upper lip
     6. depressor labii inferioris - from the lower lip down to the chin; pull the lower lip down
     7. depressor anguli oris - from the lower lip /corner to the chin; pulls the lip down at an angle
     8. orbicularis oris - around the mouth; puckers the lips
     9. mentalis - at the chin
     10. buccinator - cheek muscle
     11. platysma - sheet-like muscle from the jaw over the neck

C) muscles of mastication (chewing)
     1. masseter - over the ramus of the jaw; prime mover for closing the jaw
     2. temporalis - at the side of the head; pulls the jaw up and back in chewing
     3. medial pterygoid - inside the face; pulls the jaw side-to-side and forward for chewing
     4. lateral pterygoid - inside the face; pulls the jaw side-to-side and forward for chewing
     5. buccinator - cheek muscle

D) muscles promoting tongue movements
     1. genioglossus
     2. hyglossus
     3. styloglossus

E) suprahyoid muscles - from the mandible to the hyoid bone
     1. digastric - from the tip of the chin back to the hyoid bone
     2. stylohyoid
     3. mylohyoid
     4. geniohyoid

F) infrahyoid muscles - from the hyoid bone to the neck
     1. sternohyoid
     2. sternothyroid
     3. omohyoid
     4. thyrohyoid

G) pharyngeal constrictor muscles

H) anterolateral neck muscles
     1. sternocleidomastoid - from the sternum/clavicle back to the mastoid process; bend the neck forward
     2. scalenes - from the cervical vertebra to the top ribs

I) intrinsic muscles of the back
     1. splenius - from the occipital bone down to the spine; pulls the head back
     2. erector spinae - extend vertically down the back; keeps your back straight and extends it
          a. iliocostalis
          b. longissimus
          c. spinalis
     3. semispinalis - same function as the erector spinae, but closer to the spine
     4. quadratus lumborus - lower back muscle attached to the pelvis

J) muscles of the thorax: breathing
     1. external intercostals - rib muscles
     2. internal intercostals - rib muscles
     3. diaphragm - a single muscle that pulls down to draw air in and relaxes (and moves up) to push air out

K) muscles of the anterior and lateral abdominal wall
     1. rectus abdominus - vertical straight muscle in the middle front of the abdomen
     2. external oblique - superficial angled muscle at your sides
     3. internal oblique - internal (under the external) angled muscle at your sides
     4. transversus abdominus - horizontal muscle at your sides that holds things in

L) muscles of the pelvic floor and perineum
     1. muscles of the pelvic diaphragm
          a. levator ani
          b. coccygeus
     2. muscles of the urogenital diaphragm
          a. deep transverse perineus
          b. sphincter urethrae
     3. muscles of the superficial space
          a. ischiocavernosus
          b. bulbospongiosus
          c. superficial transverse perineus

M) muscles of the anterior thorax
     1. pectoralis minor
     2. serratus anterior - muscles that insert into your ribs; boxer's muscle
     3. subclavius

N) muscles of the posterior thorax
     1. trapezius - kite-shaped muscle that goes from the cranium to the shoulders and down to the spine; pulls the head back or shrugs the shoulders
     2. levator scapulae - attached to the top of the scapula to lift it up
     3. rhomboids - from the spine to the scapula; pulls the scapula medially towards the spine

O) muscles crossing the shoulder joint
     1. pectoralis major - chest muscle; pulls the arm forward
     2. latissimus dorsi - lower back muscle ... along the lower half of the spine and inserting onto the humerus
     3. deltoid - shoulder muscle; lifts your arm
     4. subscapularis
     5. supraspinatus
     6. infraspinatus
     7. teres minor
     8. teres major
     9. coracobrachialis

P) muscles crossing the elbow joint [cross section through the upper arm]
     1. posterior muscles of the elbow joint
          a. triceps brachii - posterior muscle of the upper arm; extends the arm
          b. anconeus - posterior muscle at the elbow that helps to pronate the arm
     2. anterior muscles of the elbow joint
          a. biceps brachii - anterior muscle of the upper arm; flexes the arm
          b. brachialis - underneath the biceps (can be seen poking out on each side at the distal end of the biceps)
          c. brachioradialis - extends to the radius; at the top of the forearm

Q) muscles of the forearm [cross section through the forearm]
     1. anterior muscles of the forearm
          a. superficial muscles of the anterior forearm
               i. pronator teres
               ii. flexor carpi radialis - on the palm side of the forearm on the thumb edge; helps make a fist
               iii. palmaris longus - on the palm side of the forearm in the middle; helps make a fist
               iv. flexor carpi ulnaris - on the palm side of the forearm on the little finger edge; helps make a fist
               v. flexor digitorum superficialis - flexes the fingers
          b. deep muscles of the anterior forearm
               i. flexor pollicis longus - flexes the thumb
               ii. flexor digitorum profundus - flexes the fingers
               iii. pronator quadratus
     2. posterior muscles of the forearm
          a. superficial muscles of the posterior forearm
               i. extensor carpi radialis longus - on the back of the forearm on the thumb edge; extends the fingers
               ii. extensor carpi radialis brevis - on the back of the forearm on the thumb edge; extends the fingers
               iii. extensor digitorum - on the back of the forearm in the middle; extends the fingers
               iv. extensor carpi ulnaris - on the back of the forearm on the little finger edge; extends the fingers
          b. deep muscles of the posterior forearm
               i. supinator - helps to twist the forearm so that it's face-up
               ii. abductor pollicis - abducts the thumb
               iii. extensor pollicis brevis - extends the thumb
               iv. extensor pollicis longus - extends the thumb
               v. extensor indicis - extends the index finger

R) thigh muscles
     1. muscles with the origin at the pelvis
          a. iliopsoas - from the iliac crest downward
               i. iliacus
               ii. psoas major
          b. sartorius - from the iliac crest, diagonally across the thigh to the medial side of the knee; helps cross the legs
     2. medial muscles of the thigh
          a. adductors - pulls the legs together; medial to the pectineus; laterial to the gracilis
               i. adductor magnus
               ii. adductor longus
               iii. adductor brevis
          b. pectineus - pulls the legs together; lateral to the adductors
          c. gracilis - pulls the legs together; medial to the adductors
     3. anterior muscles of the thigh
          a. quadriceps femoris - four muscles in the front of the thigh
               i. rectus femoris - straight, vertical muscle in the front of the thigh
               ii. vastus lateralis - to the lateral side of the rectus femoris
               iii. vastus medialis - to the medial side of the rectus femoris
               iv. vastus intermedius - underneath the rectus femoris
          b. tensor fasciae latae - at the lateral sides of the thigh
     4. posterior muscles of the thigh
          a. gluteal muscles
               i. gluteus maximus - the large muscle that you sit on
               ii. gluteus medius - located at the hip; used as an injection site
               iii. gluteus minimus
          b. lateral rotators
               i. piriformis
               ii. obturator externus
               iii. obturator internus
               iv. gemellus
               v. quadratus femoris
          c. hamstrings - three muscles at the back of the thigh
               i. biceps femoris - most medial and largest of the three muscles in the back of the thigh
               ii. semitendinosus - lateral to the biceps femoris
               iii. semimembranosus - underneath the semitendinosus

S) lower leg muscles
     1. anterior musces of the lower leg
          a. tibialis anterior - along the front of the shin bone
          b. extensor digitorum longus
          c. peroneus tertius
          d. extensor hallucis
     2. lateral muscles of the lower leg
          a. peroneus longus - at the lateral side of the lower leg
          b. peroneus brevis
     3. posterior muscles of the lower leg [cross section through the lower leg]
          a. superficial muscles
               i. triceps surae
                   1. gastrocnemius - the large calf muscle
                   2. soleus - underneath the gastrocnemius (can be seen poking out on each side at the distal end of the gastrocnemius)
               ii. plantaris
          b. deep muscles
               i. popliteus
               ii. flexor digitorum longus
               iii. flexor hallucis longus
               iv. tibialis posterior

Anterior Musculature

Posterior Musculature