OIA STUDY

A&P

Epicranius (frontal & occipital bellies): Muscles of scalp

Origin:

Insertion:

Action:

O: Frontal belly—epicranial aponeurosis & Occipital belly—occipital and temporal bones

I: Frontal belly—skin of eyebrows and root of nose & Occipital belly—epicranial aponeurosis

A: Frontal belly raises eyebrows & Occipital belly pulls scalp posteriorly and fixes aponeurosis

Orbicularis oculi : Muscles of Eye

Origin:

Insertion:

Action:

O: Frontal and maxillary bones and ligaments around orbit

I: Tissue of eyelid

A: Closes eye (blinking, squinting) & Draws eyebrows inferiorly

Levator labii superioris : Muscles of mouth

Origin:

Insertion:

Action:

O: Zygomatic bone and infraorbital margin of maxilla

I: Skin and muscle of upper lip

A: Raises and furrows upper lip & Opens lips

Zygomaticus (major & minor)

Origin:

Insertion:

Action:

O: Zygomatic bone

I: Skin and muscle at corner of mouth

A: Raises corners of mouth (smiling)

Depressor labii inferioris

Origin:

Insertion:

Action:

O: Body of mandible lateral to midline

I: Skin and muscle of lower lip

A: Draws lower lip inferiorly

Depressor anguli oris

Origin:

Insertion:

Action:

O: Body of mandible below incisors

I: Skin and muscle at angle of mouth

A: Draws corners of mouth downward

Orbicularis oris

Origin:

Insertion:

Action:

O: Indirectly from maxilla and mandible; fibers blend with other lip muscles

I: Encircles mouth; muscle and skin at angles of mouth

A: Closes lips & Purses and protrudes lips

Mentalis

Origin:

Insertion:

Action:

O: Mandible below incisors

I: Skin of chin

A: Protrudes lower lip & Wrinkles chin

Buccinator

Origin:

Insertion:

Action:

O: Molar region of maxilla and mandible

I: Orbicularis oris

A: Draws corner of mouth laterally, Compresses cheek & Holds food between teeth during chewing

Platysma : Muscles of neck

Origin:

Insertion:

Action:

O: Fascia of chest (over pectoral muscles and deltoid)

I: Lower margin of mandible; skin and muscle at corner of mouth

A: Tenses skin of neck, Depresses mandible, & Pulls lower lip back and downward

Masseter : Muscles of Mastication

Origin:

Insertion:

Action:

O: Zygomatic arch and zygomatic bone

I: Angle and ramus of mandible

A: Elevates mandible (closes jaw)

Temporalis

Origin:

Insertion:

Action:

O: Temporal fossa

I: Coronoid process of mandible

A: Elevates mandible, Retracts mandible & Closes jaw

Medial pterygoid

Origin:

Insertion:

Action:

O: Sphenoid, palatine, and maxillary bones

I: Medial surface of mandible near angle

A: Elevates mandible & Assists in grinding movements of teeth

Lateral pterygoid

Origin:

Insertion:

Action:

O: Greater wing of sphenoid bone

I: Condylar process of mandible

A: Protracts mandible (moves jaw anteriorly) & Assists in grinding movements of teeth

Digastric : Muscles of the mandibular depression

Origin:

Insertion:

Action:

O: Anterior belly—lower margin of mandible & Posterior belly—mastoid process

I: Hyoid bone (via connective tissue loop)

A: Elevates hyoid bone, Opens mouth & Depresses mandible

Sternocleidomastoid : muscles that move the head & neck

Origin:

Insertion:

Action:

O: Manubrium of sternum & Medial clavicle

I: Mastoid process of temporal bone & Superior nuchal line of occipital bone

A: Both sides: flex neck & One side: rotates head to opposite side

Scalenes (anterior, middle, posterior)

Origin:

Insertion:

Action:

O: Transverse processes of cervical vertebrae

I: Ribs 1–2

A: Flex and slightly rotate neck & Elevate ribs 1–2 (inspiration)

Splenius (capitis & cervicis)

Origin:

Insertion:

Action:

O: Ligamentum nuchae & Spinous processes C7–T6

I: Mastoid process, Occipital bone & Transverse processes C2–C4

A: Extend/hyperextend head & One side: rotates and bends head same side

Erector spinae (iliocostalis, longissimus, spinalis)

Origin:

Insertion:

Action:

O: Iliac crest & Vertebrae and ribs (varies by part)

I: Ribs and vertebrae above origin & Mastoid process (longissimus)

A: Extends vertebral column, Lateral flexion of spine & Longissimus extends/rotates head

Diaphragm : Deep thorax muscles for respiration

Origin:

Insertion:

Action:

O: Lower ribs, sternum, lumbar vertebrae, costal cartilages

I: Central tendon

A: Prime mover of inspiration & Increases thoracic volume

Internal intercostals

Origin:

Insertion:

Action:

O: Superior border of rib below

I: Inferior border of rib above

A: Depress rib cage & Forced expiration

External intercostals

Origin:

Insertion:

Action:

O: Inferior border of rib above

I: Superior border of rib below

A: Elevate rib cage & Aid inspiration

Pectoralis major : Arm Adductors

Origin:

Insertion:

Action:

O: Clavicle, Sternum, Ribs 1–6/7 & External oblique aponeurosis

I: Intertubercular sulcus of humerus

A: Flexes arm, Adducts arm & Medially rotates arm

Deltoid

Origin:

Insertion:

Action:

O: Lateral 1/3 clavicle, Acromion & Spine of scapula

I: Deltoid tuberosity of humerus

A: Abducts arm & Assists flexion, extension, rotation

Trapezius

Origin:

Insertion:

Action:

O: Occipital bone, Ligamentum nuchae & C7–all thoracic vertebrae

I: Clavicle, Acromion & Spine of scapula

A: Elevates, retracts, rotates scapula & Extends head

Latissimus dorsi

Origin:

Insertion:

Action:

O: Lower thoracic vertebrae, Lumbar vertebrae, Iliac crest & Lower ribs

I: Intertubercular sulcus of humerus

A: Extends arm, Adducts arm & Medially rotates arm

Infraspinatus

Origin:

Insertion:

Action:

O: Infraspinous fossa of scapula

I: Greater tubercle of humerus

A: Laterally rotates arm & Stabilizes shoulder

Teres minor

Origin:

Insertion:

Action:

O: Posterior lateral scapula

I: Greater tubercle of humerus

A: Laterally rotates arm & Stabilizes shoulder

Teres major

Origin:

Insertion:

Action:

O: Inferior angle of scapula

I: Intertubercular sulcus of humerus

A: Extends arm, Adducts arm & Medially rotates arm

Supraspinatus

Origin:

Insertion:

Action:

O: Supraspinous fossa of scapula

I: Greater tubercle of humerus

A: Initiates arm abduction & Stabilizes shoulder

Levator scapulae

Origin:

Insertion:

Action:

O: C1–C4 transverse processes

I: Medial border of scapula

A: Elevates scapula, Adducts scapula & Laterally flexes neck

Rhomboids (major & minor)

Origin:

Insertion:

Action:

O: C7–T5 spinous processes

I: Medial border of scapula

A:Retracts scapula, Stabilizes scapula & Rotates scapula downward

Serratus anterior

Origin:

Insertion:

Action:

O: Ribs 1–8/9

I: Medial border of scapula

A: Protracts scapula, Holds scapula against chest wall & Rotates scapula upward (arm raising)

Subscapularis

Origin:

Insertion:

Action:

O: Subscapular fossa of scapula

I: Lesser tubercle of humerus

A: Medially rotates arm, Adducts arm & Stabilizes shoulder joint

Pectoralis minor

Origin:

Insertion:

Action:

O: Ribs 3–5

I: Coracoid process of scapula

A:Draws scapula forward and downward & Elevates ribs (forced inspiration)

Rectus abdominis : Torso flexor/ Compressor muscles

Origin:

Insertion:

Action:

O: Pubic crest and symphysis

I: Xiphoid process & Costal cartilages ribs 5–7

A: Flexes vertebral column, Compresses abdomen & Stabilizes pelvis

External oblique

Origin:

Insertion:

Action:

O: Lower 8 ribs

I: Linea alba, Pubic crest/tubercle & Iliac crest

A: Compresses abdomen & Rotates and laterally flexes trunk

Internal oblique

Origin:

Insertion:

Action:

O: Iliac crest, Lumbar fascia & Inguinal ligament

I: Linea alba, Pubic crest & Costal cartilages last 3 ribs

A: Compresses abdomen, Rotates trunk & Lateral flexion

Transversus abdominis

Origin:

Insertion:

Action:

O: Inguinal ligament, Iliac crest, Costal cartilages lower ribs & Lumbar fascia

I: Linea alba & Pubic crest

A:Compresses abdominal contents

Triceps brachii

Origin:

Insertion:

Action:

O: Scapula (glenoid cavity) & Posterior humerus

I: Olecranon of ulna

A: Extends forearm

Anconeus

Origin:

Insertion:

Action:

O: Lateral epicondyle of humerus

I: Olecranon of ulna

A: Assists forearm extension & Stabilizes elbow

Biceps brachii

Origin:

Insertion:

Action:

O: Coracoid process & Supraglenoid tubercle

I: Radial tuberosity

A: Flexes forearm & Supinates forearm

Brachioradialis

Origin:

Insertion:

Action:

O: Humerus (lateral ridge)

I: Styloid process of radius

A: Flexes forearm

Brachialis

Origin:

Insertion:

Action:

O: Anterior humerus

I: Coronoid process of ulna

A: Primary flexor of forearm

Coracobrachialis

Origin:

Insertion:

Action:

O: Coracoid process of scapula

I: Midshaft of humerus

A: Flexes arm & Adducts arm

Pronator teres

Origin:

Insertion:

Action:

O: Medial epicondyle of humerus & Coronoid process of ulna

I: Midshaft of radius

A: Pronates forearm & Weak forearm flexor

Flexor carpi radialis

Origin:

Insertion:

Action:

O: Medial epicondyle of humerus

I: Bases of metacarpals II–III

A: Flexes hand & Abducts hand

Palmaris longus

Origin:

Insertion:

Action:

O: Medial epicondyle of humerus

I: Palmar aponeurosis

A: Weak flexion of hand & Tenses palmar fascia

Flexor carpi ulnaris

Origin:

Insertion:

Action:

O: Medial epicondyle of humerus & Olecranon and ulna

I: Base of metacarpal V & Pisiform and hamate

A: Flexes hand & Adducts hand

Extensor carpi radialis longus

Origin:

Insertion:

Action:

O: Lateral supracondylar ridge of humerus

I: Base of metacarpal II

A: Extends hand & Abducts hand

Extensor digitorum

Origin:

Insertion:

Action:

O: Lateral epicondyle of humerus

I: Distal phalanges of fingers II–V

A: Extends fingers & Extends hand

Extensor carpi ulnaris

Origin:

Insertion:

Action:

O: Lateral epicondyle of humerus & Posterior ulna

I: Base of metacarpal V

A: Extends hand & Adducts hand

Extensor pollicis longus & brevis

Origin:

Insertion:

Action:

O: Radius, ulna, interosseous membrane

I: Distal phalanx of thumb (longus) & Proximal phalanx of thumb (brevis)

A: Extends thumb

Adductor magnus / longus / brevis

Origin:

Insertion:

Action:

O: Pubis and ischium (varies by muscle)

I: Linea aspera of femur & Adductor tubercle (magnus)

A: Adducts thigh, Flexes thigh, Medial rotation of thigh & Magnus assists extension

Pectineus

Origin:

Insertion:

Action:

O: Pectineal line of pubis

I: Linea aspera of femur

A: Adducts thigh, Flexes thigh & Medially rotates thigh

Gracilis

Origin:

Insertion:

Action:

O: Inferior ramus and body of pubis

I: Medial tibia

A: Adducts thigh, Flexes leg & Medially rotates leg

Rectus femoris

Origin:

Insertion:

Action:

O: Anterior inferior iliac spine & Superior acetabulum

I: Tibial tuberosity (via patella)

A: Extends leg & Flexes thigh

Vastus lateralis

Origin:

Insertion:

Action:

O: Greater trochanter, Linea aspera & Intertrochanteric line

I: Tibial tuberosity (via patella)

A: Extends leg & Stabilizes knee

Vastus medialis

Origin:

Insertion:

Action:

O: Linea aspera & Intertrochanteric line

I: Tibial tuberosity (via patella)

A: Extends leg & Stabilizes patella

Vastus intermedius

Origin:

Insertion:

Action:

O: Anterior and lateral femur

I: Tibial tuberosity (via patella)

A: Extends leg

Tensor fasciae latae

Origin:

Insertion:

Action:

O: Iliac crest & ASIS

I: Iliotibial tract

A: Flexes thigh, Abducts thigh, Medially rotates thigh & Stabilizes knee/trunk

Gluteus maximus

Origin:

Insertion:

Action:

O: Ilium, Sacrum & Coccyx

I: Gluteal tuberosity of femur & Iliotibial tract

A: Extends thigh, Laterally rotates thigh & Abducts thigh

Gluteus medius

Origin:

Insertion:

Action:

O: Lateral ilium

I: Greater trochanter of femur

A: Abducts thigh, Medially rotates thigh & Stabilizes pelvis

Gluteus minimus

Origin:

Insertion:

Action:

O: Ilium

I: Greater trochanter of femur

A: Abducts thigh, Medially rotates thigh & Stabilizes pelvis

Biceps femoris

Origin:

Insertion:

Action:

O: Ischial tuberosity & Linea aspera

I: Head of fibula & Lateral tibia

A: Extends thigh, Flexes leg & Laterally rotates leg

Semitendinosus

Origin:

Insertion:

Action:

O: Ischial tuberosity

I: Medial tibia

A: Extends thigh, Flexes leg & Medially rotates leg

Semimembranosus

Origin:

Insertion:

Action:

O: Ischial tuberosity

I: Medial tibia

A: Extends thigh, Flexes leg, Medially rotates leg

Iliopsoas (iliacus + psoas major)

Origin:

Insertion:

Action:

O: Iliacus: iliac fossa & Psoas major: lumbar vertebrae

I: Lesser trochanter of femur

A: Flexes thigh at hip, Flexes trunk & Lateral flexion of spine (psoas)

Sartorius

Origin:

Insertion:

Action:

O: Anterior superior iliac spine

I: Medial proximal tibia

A: Flexes thigh, Abducts thigh, Laterally rotates thigh & Flexes leg

Tibialis anterior

Origin:

Insertion:

Action:

O: Tibia & Interosseous membrane

I: Medial cuneiform & Metatarsal I

A: Dorsiflexes foot, Inverts foot & Supports arch

Extensor digitorum longus

Origin:

Insertion:

Action:

O: Tibia, Fibula & Interosseous membrane

I: Toes II–V

A: Extends toes & Dorsiflexes foot

Extensor hallucis longus

Origin:

Insertion:

Action:

O: Fibula & Interosseous membrane

I: Distal phalanx of great toe

A: Extends great toe & Dorsiflexes foot

Gastrocnemius

Origin:

Insertion:

Action:

O: Femur (condyles)

I:Calcaneus (via Achilles tendon)

A: Plantar flexes foot & Flexes knee

Soleus

Origin:

Insertion:

Action:

O: Tibia and fibula

I: Calcaneus

A: Plantar flexes foot

Tibialis posterior

Origin:

Insertion:

Action:

O: Tibia, Fibula & Interosseous membrane

I: Tarsals and metatarsals (II–IV region)

A: Inverts foot (prime mover), Plantar flexes foot & Supports arch

Flexor digitorum longus

Origin:

Insertion:

Action:

O: Posterior tibia

I: Distal phalanges of toes II–V

A: Flexes toes, Plantar flexes foot & Inverts foot

Flexor hallucis longus

Origin:

Insertion:

Action:

O: Fibula & Interosseous membrane

I: Distal phalanx of great toe

A: Flexes great toe, Plantar flexes foot & Inverts foot

Fibularis (peroneus) longus

Origin:

Insertion:

Action:

O: Head and upper fibula

I: Metatarsal I & Medial cuneiform

A: Everts foot & Plantar flexes foot