Anatomy and Chemistry Basics
The Muscular System
The major skeletal muscles are illustrated in Figures 1 through 6 and described in Tables 1 through 4.
Figure 1. The major skeletal muscles—anterior superficial view.
Figure 2. The major skeletal muscles—posterior superficial view.
|
Muscle |
Origin/Insertion |
Action |
|---|---|---|
|
frontalis |
o: galea aponeurotica i: skin around eyes |
raises eyebrows; surprised |
|
occiptalis |
o: occipital bone i: galea aponeurotica |
pulls scalp back; surprised |
|
orbicularis oculi |
o: maxillary and frontal bones i: eyelids |
closes eyelids; blinking |
|
orbicularis oris |
o: muscle fibers around mouth i: skin around mouth |
closes lips; kissing |
|
buccinator |
o: maxilla and mandible i: orbicularis oris |
compresses cheek; whistling |
|
platysma |
o: fascia in upper chest i: mandible and corner of mouth |
lowers mandible; opens mouth |
|
mentalis |
o: mandible i: skin of chin |
protrudes lower lip; pouting |
|
risorius |
o: fascia on masseter muscle i: skin at corner of mouth |
lateral movement of lips; grimacing |
|
zygomaticus |
o: zygomatic bone i: skin around mouth |
raises edges of mouth; smiling |
|
levator labii superioris |
o: infroarbital margin of maxilla i: skin of upper lip |
raises upper lip; as in disgust |
|
depressor labii inferioris |
o: mandible i: skin of lower lip |
lowers lower lip |
|
temporalis |
o: parietal bone i: mandible |
raises mandible; closes mouth |
|
masseter |
o: zygomatic arch i: mandible |
raises mandible; closes mouth |
|
medial pterygoid |
o: sphenoid and maxilla i: mandible |
raises mandible; side-to-side mouth motion |
|
lateral pterygoid |
o: sphenoid and maxilla i: mandible |
raises mandible; side-to-side mouth motion |
|
sternocleidomastoid |
o: sternum and clavicle i: temporal bone |
flexes and rotates head |
|
splenius capitis |
o: cervical and thoracic vertebrae i: temporal bone |
rotates, bends, or extends head |
|
semispinalis capitis |
o: cervical and thoracic vertebrae i: occipital bone |
rotates or extends head |
|
longissimus |
o: cervical and thoracic vertebrae i: temporal bone |
rotates, bends, or extends head |
|
omohyoid |
o: scapula i: hyoid bone |
depresses hyoid bone |
|
sternohyoid |
o: sternum and clavicle i: hyoid bone |
depresses hyoid bone |
|
Muscle |
Origin/Insertion |
Action |
|---|---|---|
|
semispinalis capitis |
o: cervical and thoracic vertebrae i: occipital bone |
extends and rotates head |
|
splenius capitis |
o: cervical and thoracic vertebrae i: occipital and temporal bone |
extends and rotates head |
|
deltoid |
o: clavicle and scapula i: humerus |
abducts, flexes, extends, and rotates arm |
|
pectoralis major |
o: clavicle, sternum, ribs i: humerus |
flexes, adducts, and rotates arm |
|
infraspinatus |
o: scapula i: humerus |
rotates arm |
|
teres major |
o: scapula i: humerus |
extends and rotates arm |
|
latissimus dorsi |
o: vertebrae, ribs, ilium i: humerus |
extends, adducts, and rotates arm |
|
levator scapulae |
o: cervical vertebrae i: scapula |
elevates scapula |
|
pectoralis minor |
o: ribs i: scapula |
stabilizes scapula; elevates ribs |
|
serratus anterior |
o: ribs i: scapula |
stabilizes scapula; elevates ribs |
|
trapezius |
o: occipital bone and cervical/thoracic vertebrae i: scapula and clavicle |
elevates, adducts, and rotates scapula |
|
rhomboideous major / rhomboideus minor |
o: cervical/thoracic vertebrae i: scapula |
adducts and rotates scapula |
|
rectus abdominis |
o: pubic crest and symphysis i: xiphoid process and ribs |
flexes vertebral column; compresses abdomen |
|
external oblique |
o: ribs i: linea alba, ilium |
compresses abdomen; rotates trunk |
|
transverse abdominis |
o: ilium, ribs i: linea alba, xiphoid process |
compresses abdomen |
|
external intercostals |
o: lower border of rib above i: upper border of rib below |
elevates ribs; aids inspiration |
|
internal intercostals |
o: upper border of rib below i: lower border of rib above |
pulls ribs together; aids expiration |
|
diaphragm |
o: lower ribs, sternum i: central tendon |
aids inspiration |
|
spinalis |
o: lumbar and thoracic vertebrae i: thoracic and cervical vertebrae |
extends vertebral column |
|
longissimus |
o: lumbar and cervical vertebrae i: temporal bone, vertebrae |
extends vertebral column |
|
iliocostalis |
o: ilium, ribs i: ribs |
extends vertebral column |
Figure 3. The major skeletal muscles—anterior and lateral views.
Figure 4. The major skeletal muscles—anterior superficial view, anterior deep view, posterior superficial view, and posterior deep view.
|
Muscle |
Origin/Insertion |
Action |
|---|---|---|
|
coracobrachiolis |
o: scapula i: humerus |
flexes and adducts arm |
|
biceps brachii |
o: scapula, glenoid cavity i: radius |
flexes arm, flexes forearm, rotates hand |
|
brachialis |
o: humerus i: ulna |
flexes forearm |
|
brachioradialis |
o: humerus i: radius |
flexes forearm |
|
triceps brachii |
o: humerus i: ulna |
extends forearm |
|
anconeus |
o: humerus i: ulna |
extends forearm |
|
pronator teres |
o: humerus, ulna i: radius |
medial rotation of forearm pronate hand |
|
pronator quadratus |
o: ulna i: radius |
medial rotation of forearm pronate hand |
|
supinator |
o: ulna i: radius |
lateral rotation of forearm |
|
flexor carpi radialis |
o: humerus i: metacarpals |
flexes and abducts wrist |
|
flexor carpi ulnaris |
o: humerus, ulna i: carpals, metacarpals |
flexes and abducts wrist |
|
flexor digitorum superficialis |
o: humerus, ulna, radius i: phalanges |
flexes fingers 2–5 |
|
flexor digitorum profundus |
o: ulna i: phalanges |
flexes distal fingers 2–5 |
|
palmaris longus |
o: humerus i: flexor retinaculum |
flexes wrist |
|
extensor carpi radialis longus |
o: humerus i: second metacarpal |
extends and abducts wrist |
|
extensor carpi ulnaris |
o: humerus, ulna i: fifth metacarpal |
extends and adducts wrist |
|
extensor digitorum |
o: humerus i: distal phalanges |
extends fingers 2–5 |
|
extensor pollicis brevis |
o: radius i: phalanx of thumb |
extends thumb |
|
extensor pollicis longus |
o: radius i: phalanx of thumb |
extends thumb |
|
extensor indicis |
o: ulna i: index finger |
extends index finger |
|
abductor pollicis longus |
o: radius and thumb i: first metacarpal |
abducts and extends thumb |
|
Muscle |
Origin/Insertion |
Action |
|---|---|---|
|
gluteus maximus |
o: ilium, sacrum, coccyx i: femur |
extends and rotates thigh |
|
gluteus medius |
o: ilium i: femur |
abducts and rotates thigh |
|
pectineus |
o: pubis i: femur |
adducts and flexes thigh |
|
adductor longus |
o: pubis i: femur |
adducts, flexes, and rotates thigh |
|
adductor brevis |
o: pubis i: femur |
adducts, flexes, and rotates thigh |
|
adductor magnus |
o: pubis, ischium i: femur |
adducts, flexes, and rotates thigh |
|
gracilis |
o: pubis i: tibia |
adducts thigh and flexes leg |
|
sartorius |
o: ilium i: tibia |
flexes and rotates thigh; flexes leg |
|
quadriceps femoris: rectus femoris |
o: ilium, femur i: patella, tibia |
extends leg; flexes thigh |
|
quadriceps femoris: vastus lateralis |
o: ilium, femur i: patella, tibia |
extends leg |
|
quadriceps femoris: vastus medialis |
o: ilium, femur i: patella, tibia |
extends leg |
|
quadriceps femoris: vastus intermedius |
o: ilium, femur i: patella, tibia |
extends leg |
|
biceps femoris (hamstrings) |
o: ischium, femur i: fibula |
flexes and rotates leg; extends thigh |
|
semitendinosus (hamstrings) |
o: ischium i: tibia |
flexes and rotates leg; extends thigh |
|
semimembranosus (hamstrings) |
o: ischium i: tibia |
flexes and rotates leg; extends thigh |
|
tibialis anterior |
o: tibia i: 1st metatarsal and cuneiform |
dorsiflexes and inverts foot |
|
extensor digitorum longus |
o: tibia, fibula i: phalanges of toes |
dorsiflexes and everts foot; extends toes |
|
gastrocnemius |
o: femur i: calcanues |
plantar flexes foot; flexes leg |
|
soleus |
o: tibia, fibula i: calcaneus |
plantar flexes foot |
Figure 5. The major skeletal muscles—anterior superficial view, anterior deep view, posterior superficial view, and posterior deep view.
Figure 6. The major skeletal muscles—anterior superficial view, anterior deep view, posterior superficial view, and posterior deep view.
