gross anatomy of skeletal muscles

Gross anatomy of muscles:

Muscles of facial expression:

epicranius-- made up of the frontalis and occipitalis muscles
frontalis-- originates at the galea aponeurotica and inserts at the skin superior to the supraorbital line. It draws the scalp forward and and raises the eyebrows, as well as wrinkling the forehead horizontally
occipitalis-- origin is at the occipital bone and the mastoid process of the temporal bone, insertion at the galea aponeurotica. Used to draw back the scalp
orbicularis oris-- origin at the muscle fibers surrounding the opening of the mouth, insertion at the skin of the corners of the mouth. Closes and compresses lips against the teeth, protrudes lips, and forms lips during speech
zygomaticus major-- originates at the zygomatic bone and insertion at the angle of the mouth and orbicularis oris. Draws up the angle of the mouth or draws it out, such as in smiling or laughing
levator labii superior-- originates from the superior to infraorbital foramina of the maxillary bone and inserting at the angle of the mouth and the orbicularis oris to raise (elevate) the upper lip
depressor labil inferioris-- origin at the mandible, lateral to the mentalis, and inserting at the skin of the lower li to depress the lower lip
buccinator-- originates at the alveolar processes of the maxilla and mandible, and the pterygomandibular raphe (a fibrous band extending from the pterygoid hamulus to the mandible). It inserts at the orbicularis oris. This is the major cheek muscle, compresses the cheek as in blowing out air or causing the cheeks to cave in for the sucking action
mentalis-- the most lateral mandibular muscle, originating at the bottom of the bone and inserting at the skin of the chin, used to elevate and protrude the lower lip, and pulls the skin of the chin up, as in pouting
platysma-- originates at the fascia over the deltoid and pectoralis major, inserting at the mandible, muscles at the angle of the mouth, and the skin of the lower face. A broad, flat muscle used to draw outer parts of the lower lip downward and backward or depress the mandible
risorius-- originates at the fascia over the salivary gland and inserting at the angle of the mouth. Used to draw the angle of the mouth laterally
orbicularis occuli-- originates at the medial wall of the orbit, following a circular path around the eye. This muscle is used to close the eye
corrugator supercilii-- origin at the medial end of the superciliary arch of the frontal bone and insertion at the skin of the eyebrow to draw the eyebrow down
levator palpebrae superioris-- originates at the roof of the orbit (lesser wing of the sphenoid bone), insertion at the upper eyelid to elevate the superior eyelid

Muscles that move the lower jaw:

masseter-- origin at the maxillary bone and zygomatic arch, inserting at the angle and ramus of the mandible to elevate the mandible and protrude it
temporalis-- originates at the temporal bone, inserting at the coronoid process of the mandible. Used to elevate and retract the mandible
medial pterygoid-- origin at the medial surface of the lateral pterygoid plate of the sphenoid and the maxilla, inserting at the angle and ramus of the mandible. For elevating and protruding, as well as moving the mandible side to side
lateral pterygoid-- originates at the greater wing of the and the lateral surface of the pterygoid plate of the sphenoid, inserting at the condyle of the mandible to protract the mandible and move it sideways

Muscles that move the eye (extrinsic):

superior rectus-- origin at the tendinous ring around the optic foramen, insertion at the superior and central portion of the eye to roll the eye up
inferior rectus-- origin at the tendinous ring around the optic foramen, insertion at the inferior and central eye to move the eye down
lateral rectus-- origin at the tendinous ring around the optic foramen, insertion at the lateral eye to move the eye laterally
medial rectus-- origin at the tendinous ring around the optic foramen, insertion at the medial eye to move the eye medially
superior oblique-- origin at the tendinous ring around the optic foramen, insertion between the superior and lateral recti to rotate the eye on it's axis, directing the cornea down and laterally. Note that this moves through a ring of fibrocartilage called the trochlea(trochlea=pulley)
inferior oblique-- originates at the maxillary bone in front of the orbital cavity, inserting between the inferior and lateral recti to move the eye on it's axis, directing the cornea up and laterally

Muscles that move the tongue:

genioglossus-- origin at the mandible, insertion at the inferior surface if the tongue and the hyoid bone to depress the tongue and thrust it forward
styloglossus-- originates at the styloid process of the temporal bone, insertion at the lateral and inferior surfaces of the tongue
palatoglossus-- origin at the anterior surface of the soft palate, insertion at the the lateral surface of the tongue to draw the tongue up and the soft palate down
hyoglossus-- origin at the body of the hyoid bone, insertion at the lateral surface of the tongue to depress the tongue and draw down it's sides

Muscles of the pharynx:

inferior constrictor-- origin at the cricoid and thyroid cartilages of the larynx, insertion at the posterior median raphe of the pharynx to constrict the inferior portion of the larynx
middle constrictor-- origin at the greater and lesser cornu of the hyoid and the stylohyoid ligament, insertion at the posterior median raphe of the pharynx to constrict the middle larynx (as in to propel a bolus out of the throat)
superior constrictor-- origin at the pterygoid process, pterygoidmandibular raphe, and the mylohoid line of the mandible, insertion at the posterior median raphe of the pharynx to constrict the superior pharynx
stylopharyngeus-- origin at the medial side of the base of the styloid process, insertion at the lateral aspect of the pharynx and thyroid cartilage to elevate the pharynx and dialate it
salpingopharyngeus-- origin at the inferior portion of the auditory tube, insertion at the posterior fibers of the palatopharyngeus muscle to elevate the superior portion of the lateral wall of the pharynx during swallowing and opens the orifice of auditory tube
palatopharyngeus-- origin at the soft palate, insertion at the posterior border of the thyroid cartilage and lateral wall of the pharynx to elevate the larynx and pharynx and helps close nasopharynx during swallowing

Muscles of the floor of the oral cavity:

digastric-- anterior belly origin from the inner side of the lower border of the mandible, posterior belly from the mastoid process of the temporal bone, insertion at the body of the hyoid bone via an intermediate tendon to elevate the hyoid bone and depress the mandible
stylohyoid-- origin from the styloid process of the temporal bone, insertion at the body of the hyoid bone to elevate the hyoid and draw it back
mylohyoid-- origin from the inner surface of the mandible, insertion at the body of the hyoid bone to elevate the hyoid and floor of the mouth, depresses the mandible
geniohyoid-- origin from the inner surface of the mandible, insertion at the hyoid to elevate the hyoid and tongue anteriorly, to depress the mandible

Muscles of the larynx:

omohyoid-- origin at the superior border of the scapula and superior transverse ligament, insertion at the body of the hyoid to depress the hyoid
sternohyoid-- origin at the medial end of the clavicle and manubrium of the sternum to depress the hyoid
sternothyroid-- origin at the manubrium, insertion at the hyoid cartilage of the larynx to depress the thyroid cartilage
thyrohyoid-- origin at the thyroid cartilage, insertion at the greater cornu of the hyoid to elevate the thyroid cartilage and depress the hyoid
cricothyroid-- origin at the anterior and lateral portions of the cricoid cartilage of the larynx, insertion at the anterior border of the inferior cornu of the hyoid and posterior part of the inferior border of the lamina of the thyroid cartilage

Muscles that move the head:

sternocleidomastoid-- origin at the sternum and clavicle, insertion at the mastoid process of the temporal bone. Contractions of both flex the cervical vertebrae, draw the head forward, and elevate the chin. Contractions of one muscle rotates the head towards the opposite shoulder
semispinalis capitis-- origin at the articular process of the C7 and the the transverse process of T1-T6, insertion at the occipital bone to extend (both) or rotate (one at a time) the head towards the same side as the contracted muscle
splenius capitis-- origin at the ligamentum nuchae and the spines of C1-C7 and T1-T6, insertion at the occipital bone and mastoid process of the temporal to extend or rotate the head to the same side as the contracted muscle
longissimus capitis-- origin at the transverse process of C4-C7, insertion at the mastoid process of the temporal bone to extend or rotate the head in the opposite direction

Muscles that act on the anterior abdominal wall:

rectus abdominis-- origin at the pubic crest and the symphysis pubis, insertion at the cartilage of fifth to seventh ribs and xiphoid process to flex the vertebral column and compress the abdomen
external oblique-- origin at the lower eight ribs, insertion at the iliac crest and linea alba (midline aponeurosis). Contraction of both compresses the abdomen. Contraction of one bends the spine laterally
internal oblique-- origin at the iliac crest, inguinal ligament, and thoracolumbar fascia, insertion at the last three or four ribs to compress the abdomen or bend the spine laterally
transverse abdominis-- origin at the iliac crest, inguinal ligament, lumbar fascia, and cartilages of the last six ribs, insertion at the xiphoid process, linea alba, and pubis to compress the abdomen

Muscles used in breathing

diaphragm-- origin at the xiphoid process, costal cartilage of the last six ribs, and the lumbar vertebrae. THe diaphragm forms the thoracic floor, pulls the central tendon down during inspiration, increasing the lateral and anteroposterior dimensions of the thorax
external intercostals-- origin at the inferior border of the rib superior to the muscle, insertion at the superior border of the inferior rib to elevate the ribs during inspiration and increasing the volume of the thorax
internal intercostals-- origin at the superior border of the inferior rib, insertion at the inferior border of the superior rib to draw adjacent ribs together during forced expiration and decreasing the volume of the thorax

Muscles of the pelvic floor:

levator ani-- made up of the pubococcygeus and the iliococcygeus
pubococcygeus-- origin at the pubis, insertion at the coccyx, urethra, anal canal, and central tendon of the peritoneum. Used to support and slightly raise the pelvic floor, resists increased intraabdominal pressure, and draws the anus towards the pubis and constricts it
iliococcygeus-- origin at the ischial spine, insertion at the coccyx, same purpose served at the pubococcygeus
coccygeus-- origin at the ischial spine, insertion at the lower sacrum and upper coccyx. Used to support and slightly raise the pelvis floor, resists intraabdominal pressure, and pulls the coccyx forward following deification or parturition

Muscles of the perineum (the entire outlet of the pelvis):

superficial transverse perineus-- origin at the ischial tuberosity, insertion at the central tendon of the perineum to help stabilize the central tendon
bulbocavernosus-- origin at the central tendon of the perineum, insertion at the inferior fascia of the urogenital diaphragm, corpus spongiosum and deep fascia on dorsum of the penis in males, pubic arch and root and dorsum of the clitoris in females. Action, in males is maintaining an erection in males, and clitoris in females
ischiocavernosus-- origin at the ischial tuberosity, ischial and pubic rami, insertion at the corpus cavernosum of the penis or clitoris to help eject last drops of urine and semen
urogenital diaphragm-- consists of the deep transverse perineus, the urethral sphincter, and a fibrous membrane
deep transverse perineus-- origin at the ischial rami, insertion at the central tendon of the perineum to help eject last drops of semen and urine
urethral sphincter-- origin at the ischial and pubic rami, insertion at the medial raphe in males and the vaginal wall in females. Used for the same purposes as the deep transverse perineum
external anal sphincter-- origin at the anococcygeal raphe, insertion at the central tendon of the perineum to keep the anal canal and orifice closed

Muscles that move the pectoral (shoulder) girdle:

subclavius-- origin at the first rib, insertion at the clavicle to depress the clavicle
pectoralis minor-- origin at the third through fifth ribs, insertion at the coracoid process of the scapula. Used to depress the scapula, rotate the shoulder joint anteriorly, and elevates the third, fourth and fifth ribs during forced inspiration when the scapula is fixed
serratus anterior-- origin at the upper eight or nine ribs, insertion at the vertebral border and inferior angle of the scapula to rotate the scapula laterally and elevate the ribs when the scapula is fixed
trapezius-- origin at the occipital bone, ligamentum nuchea, and spines of C7 and C1-C7, insertion at the clavicle and acromion process and spine of the scapula. Used to elevate the clavicle, adducts the scapula, elevates or depresses the scapula, and extends the head
rhomboideus major-- on the posterior aspect of the back. Origin at the spines of T2-T5, insertion at the vertebral border of the scapula to adduct the scapula and slightly rotate it superiorly
rhomboideus minor-- located superiorly to rhomboideus major, more angled than the larger. Origin at the spines of C7 and T1, insertion at the superior angle of the scapula to adduct the scapula

Muscles that move the arm:

pectoralis major-- a large, fan-shaped muscle on the chest. Origin at the clavicle, sternum, and cartilages of the second to sixth ribs, insertion at the greater tubercle of the humerus. Used to flex the arm, adduct it, and rotate the arm medially
deltoid-- origin at the clavicle, acromion and spine of the scapula, insertion at the deltoid tuberosity of the humerus. Abducts, flexes, and extends the arm
subscarularis-- origin at the supraspinous fossa of the scapula, insertion at the greater tubercle of the humerus. Assists the deltoid in abduction of the arm
infraspinatus-- origin at the infraspinous fossa of the scapula, insertion at the greater tubercle of the humerus. Rotates the arm laterally
latissimus dorsi-- origin at the spines of T6-T12 and L1-L5, the crests of the sacrum and ilium, and the lower four ribs, insertion at the intertubercular groove of the humerus. Extends, adducts, and rotates the arm medially, draws the shoulder down and back
teres major-- origin at the inferior angle of the scapula, insertion distal to the lesser tubercle of the humerus. Extends the arm and draws it sown, assists in adduction and medial rotation
teres minor-- origin at the lateral border of the scapula, insertion at the greater tubercle of the humerus

Muscles that move the forearm:

biceps brachii-- origin for the long head is the the tubercle above the glenoid cavity, for the short head, the coracoid process of the scapula. Insertion is at the radial tuberosity and bicipital aponeurosis. Flexes and supinates the forearm
brachilalis-- origin at the distal, anterior surface of the humerus, insertion at the tuberosity and coronoid process of the ulna for flexing the forearm
brachioradialis-- origin at the supracondyloid ridge of the humerus, insertion at the superior styloid process of the radius. Flexes the forearm
triceps brachii-- origin of the long head is the infraglenoid tuberosity of the scapula, the origin for the lateral head is the lateral and posterior surface of the humerus superior to the radial groove, the medial head, the posterior surface of the humerus inferior to the radial groove. Insertion at the olecranon of the ulna. Extends the forearm
coracobrachialis-- origin at the coracoid process of the scapula, insertion at the middle of the medial surface of the shaft of the humerus. Flexes and adducts the arm
anconeus-- origin at the lateral epicondyle of the humerus, insertion at the olecranon and superior portion of the shaft of the ulna. Extends the forearm
supinator-- origin at the lateral epicondyle of the humerus and ridge on the ulna, insertion at the oblique line of the radius. Supinates the forearm
pronator teres-- origin at the medial epicondyle and coronoid process of the ulna, insertion at the midlateral surface of the radius. Pronates the forearm
pronator quadratus-- origin at the distal portion of the shaft of the ulna, insertion at the distal portion of the radius. Pronates and rotates the forearm

Muscles that move the wrist and fingers:

flexor carpi radialis-- on the anterior aspect. Origin at the medial epicondyle of the humerus, insertion at the second and third metacarpals. Flexes and abducts the wrist
flexor carpi ulnaris-- on the anterior aspect. Origin at the medial epicondyle of the humerus and the upper dorsal border of the ulna, insertion at the pisiform, hamate, and fifth metacarpal. Flexes and adducts the wrist
palmaris longus-- on the anterior aspect. Origin at the medial epicondyle of the humerus, insertion at the transverse carpal ligament and palmar aponeurosis. Flexes the wrist and tenses the palmar aponeurosis
extensor carpi radialis longus-- on the posterior aspect. Origin at the lateral epicondyle of the humerus, insertion at the second metacarpal. Extends and abducts the wrist
flexor digitorum profundus-- on the anterior aspect. Origin at the medial epicondyle of the humerus, coronoid process of the ulna, and the oblique line of the radius. Insertion at the bases of the distal phalanges. Flexes the distal phalanges
flexor digitorum superficialis-- origin at the medial epicondyle of the humerus, coronoid process of the ulna, and oblique line of the radius. Insertion at the middle phalanges. Flexes the middle phalanges
extensor digitorum-- origin at the lateral epicondyle of the humerus, insertion at the the middle and distal phalanges. Extends phalanges
extensor indicis-- origin at the dorsal surface of the ulna, insertion at the tendon of the extensor digitorum of the index finger. Extends the index finger

Muscles that move the vertebral column:

rectus abdominis-- origin at the pubic crest and symphysis pubis, insertion at the cartilages of the fifth through seventh ribs and the xiphoid process. Flexes the vertebral column at the lumbar curve and compresses the abdomen
quadratus lumborum-- origin at the iliac crest, insertion at the twelfth rib and L1-L4. Flexes the vertebral column laterally
sacrospinalis-- consists of three groups: iliocostalis (lateral), longissimus (intermediate), and spinalis (medial)
lateral:

iliocostalis lumborum-- origin at the iliac crest, insertion at the lower six ribs. Extends the lumbar region
iliocostalis thoracis-- origin at the lower six ribs, insertion at the upper six ribs. Maintains erect position
iliocostal cervicis-- origin at the first six ribs, insertion at the transverse processes of T4-T6. Extends the cervical region

intermediate:

longissimus thoracis-- origin at the transverse processes of the lumbar vertebrae, insertion at the transverse processes of all the thoracic vertebrae, upper lumbar, and ninth and tenth ribs. Extends the thoracic region
longissimus cervicis-- origin at the transverse processes of T4-T5, insertion at the transverse processes of C2-C6. Extends the cervical region
longissimus capitalis-- origin at the transverse processes of the upper four thoracic vertebrae, insertion at the mastoid process of the temporal bone. Extends the head and rotates it to opposite sides

medial:

spinalis thoracis-- origin at the spines of the upper lumbar and lower thoracic vertebrae, insertion at the spines of the upper thoracic vertebrae. Extends the vertebral column

Muscles that move the thigh:

iliopsoas-- the psoas major and iliacus
psoas major-- origin at the transverse processes and bodies of the the lumbar vertebrae, insertion at the lesser trochanter of the femur. Flexes and rotates the thigh laterally, flexes the vertebral column
iliacus-- origin at the iliac fossa, insertion at the tendon of the psoas major. Flexes and rotates the thigh laterally, slightly flexes the vertebral column
gluteus maximus-- origin at the iliac crest, sacrum, coccyx, and aponeurosis of the sacrospinalis. Insertion at the iliotibial tract of the fascia lata and gluteal tuberosity of the femur. Extends and rotates the thigh laterally
gluteus medius-- origin at the ilium, insertion at the greater trochanter of the femur, Abducts and rotates the thigh medially
gluteus minimus-- origin at the ilium, insertion at the greater trochanter of the femur. Abducts and rotates the thigh laterally
tensor fasciae latae-- origin at the iliac crest, insertion at the tibia by way of the iliotibial tract. Flexes and abducts the thigh
adductor longus-- origin at the pubic crest and symphysis pubis, insertion at the linea aspera of the femur. Adducts, rotates, and flexes the thigh
adductor brevis-- origin at the inferior ramus of the pubis, insertion at the linea aspera of the femur. Adducts, rotates, and flexes the thigh
adductor magnus-- origin at the inferior ramus of the pubis and ischium to ischial tuberosity, insertion at the linea aspera of the femur. Adducts, flexes, and extends the thigh
piriformis-- origin at the sacrum, insertion at the greater trochanter of the femur to rotate the thigh laterally and abducts it
obturator internus-- origin at the margin of the obturator foramen, pubis, and ischium, insertion at the greater trochanter of the femur. Rotates the thigh laterally and abducts it
pectineus-- origin at the fascia of the pubis, insertion at the pectineal line of the femur. Flexes, adducts and rotates the thigh laterally

Muscles that act on the leg:

quadriceps femoris-- four distinct part, usually described as separate muscles. The patellar ligament, rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius
rectus femoris-- origin at the anterior inferior iliac spine, insertion at the upper boarder of the patella. Used with the others to extend the leg. Used alone to flex the thigh
vastus lateralis-- origin at the greater trochanter and linea aspera of the femur. Insertion at the upper border and sides of the patella, tibial tuberosity through the patellar ligament. Used with the others to extend the leg
vastus medialis-- origin at the linea aspera of the femur. Insertion at the upper border and sides of the patella, tibial tuberosity through the patellar ligament. Used with the others to extend the leg
vastus intermedius-- origin at the anterior and lateral surfaces of the body of the femur. Insertion at the upper border and sides of the patella, tibial tuberosity through the patellar ligament. Used with the others to extend the leg
hamstrings-- the biceps femoris, semitendinosus, and semimembranosus
biceps femoris-- long head originates at the ischial tuberosity, the short head from the linea aspera of the femur. Insertion at the head of the fibula and lateral condyle of the tibia. Flexes the leg and extends the thigh
semitendinosus-- origin at the ischial tuberosity, insertion at the proximal part of the medial surface of the body of the tibia. Flexes the leg and extend the thigh
semimembranosus-- origin at the ischial tuberosity, insertion at the medial condyle of the tibia. Flexes the leg and extends the thigh
gracillis-- origin at the symphysis pubis and pubic arch, insertion at the medial surface of the body of the tibia. Flexes the leg and extends the thigh
sartorius-- long, strap-like muscle of the inner thigh. Origin at the anterior superior spine of the ilium, insertion at the medial surface of the body of the tibia. Flexes the leg, flexes the thigh and rotates it laterally, as in crossing the legs

Muscles that move the foot and toes:

gastrocnemius-- origin at the lateral and medial condyles of the femur and the capsule of the knee. Insertion at the calcaneus vie the calcaneal (Achilles) tendon. The Achilles tendon is able to take 1000 pounds of force without tearing, yet is the most commonly torn tendon of the human body. Plantar flexes the foot
soleus-- origin at the head of the fibula and medial border of the tibia, insertion at the calcaneus via the Achilles tendon. Plantar flexes the foot
peroneus longus-- origin at the head and body of the fibula and lateral condyle of the tibia, insertion at the first metatarsal and first cuneiform. Plantar flexes and everts the foot
peroneus brevis-- origin at the body of the fibula, insertion at the fifth metatarsal. Plantar flexes and everts the foot
peroneus tertius-- origin at the distal third of the fibula, insertion at the fifth metatarsal. Dorsiflexes and everts the foot
tibialis anterior-- origin at the lateral condyle of the body of the tibia, insertion at the first metatarsal and first cuneiform. Dorsiflexes and inverts the foot
tibialis posterior-- origin at the interisseus membrane between the tibia and fibula. Insertion at the second, third, and fourth metatarsals, navicular, third cuneiform, and cuboid. Plantar flexes and inverts the foot
flexor digitorum longus-- origin at the tibia, insertion at the distal phalanges of the four toes. Flexes the toes, plantar flexes and inverts the foot
extensor digitorum longus-- origin at the lateral condyle of the the tibia and anterior surface of the fibula. Inserts at the middle and distal phalanges the the four toes. Extends the toes, dorsiflexes and everts the foot

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