OIA (easy)

Trapezius

• Origin: skull + upper spine

• Insertion: clavicle + scapula

• Action: elevates, retracts, and depresses scapula

Rhomboid Major

• Origin: upper thoracic vertebrae

• Insertion: medial border of scapula

• Action: retracts (pulls back) scapula

Rhomboid Minor

• Origin: lower cervical / upper thoracic vertebrae

• Insertion: medial border of scapula (above major)

• Action: retracts scapula

Pectoralis Major

• Origin: clavicle, sternum, ribs

• Insertion: humerus

• Action: flexes, adducts, and medially rotates arm

Serratus Anterior

• Origin: ribs

• Insertion: medial border of scapula

• Action: protracts scapula (“boxer’s muscle”)

Latissimus Dorsi

• Origin: lower spine + iliac crest

• Insertion: humerus

• Action: extends, adducts, and medially rotates arm

Deltoid

• Origin: clavicle + scapula

• Insertion: humerus (deltoid tuberosity)

• Action: abducts arm

Gluteus Maximus

• Origin: ilium + sacrum

• Insertion: femur + IT band

• Action: extends thigh (climbing, rising)

Semimembranosus

• Origin: ischial tuberosity

• Insertion: medial tibial condyle

• Action: extends thigh & flexes knee

Biceps Femoris

• Origin: long head: ischial tuberosity
  short head: femur

• Insertion: fibula

• Action: flexes knee; long head extends thigh

Rectus Femoris

• Origin: iliac spine

• Insertion: tibial tuberosity

• Action: extends knee + flexes hip

Vastus Medialis

• Origin: femur

• Insertion: tibial tuberosity

• Action: extends knee

Vastus Intermedius

• Origin: femur

• Insertion: tibial tuberosity

• Action: extends knee

Vastus Lateralis

• Origin: femur

• Insertion: tibial tuberosity

• Action: extends knee

Sartorius

• Origin: ASIS (hip bone)

• Insertion: medial tibia

• Action: flexes hip + flexes knee (“criss-cross” muscle)

Pectineus

• Origin: pubis

• Insertion: femur

• Action: adducts and flexes thigh

Iliacus

• Origin: iliac fossa

• Insertion: femur (with psoas)

• Action: flexes thigh

Psoas Major

• Origin: lumbar vertebrae

• Insertion: femur

• Action: flexes thigh

Gastrocnemius

• Origin: femoral condyles

• Insertion: calcaneus

• Action: plantar flexion (point toes)

Soleus

• Origin: tibia + fibula

• Insertion: calcaneus

• Action: plantar flexion

Tibialis Anterior

• Origin: tibia

• Insertion: first metatarsal

• Action: dorsiflexes foot (toes up)

Fibularis Longus

• Origin: fibula

• Insertion: 1st metatarsal + cuneiform

• Action: everts foot

Biceps Brachii

Long head:

• Origin: supraglenoid tubercle
  Short head:

• Origin: coracoid process

• Insertion: radial tuberosity

• Action: flexes elbow + supinates forearm

Triceps Brachii

Long head:

• Origin: scapula
  Lateral & medial heads:

• Origin: humerus

• Insertion: olecranon of ulna

• Action: extends elbow

Brachialis

• Origin: humerus

• Insertion: ulna

• Action: main elbow flexor

Orbicularis Oculi

• Origin: around orbit

• Insertion: eyelid skin

• Action: closes eye

Orbicularis Oris

• Origin: around mouth

• Insertion: lips

• Action: closes/purses lips

Buccinator

• Origin: maxilla + mandible

• Insertion: orbicularis oris

• Action: compresses cheek (blowing, sucking)

Masseter

• Origin: zygomatic arch

• Insertion: mandible

• Action: elevates mandible (chewing)

External Oblique

• Origin: ribs

• Insertion: linea alba + pelvis

• Action: compresses abdomen; trunk rotation

Internal Oblique

• Origin: pelvis

• Insertion: ribs + linea alba

• Action: compresses abdomen; trunk rotation

Rectus Abdominis

• Origin: pubis

• Insertion: ribs + xiphoid

• Action: flexes trunk (sit-ups)

Transversus Abdominis

• Origin: ribs + pelvis

• Insertion: linea alba

• Action: compresses abdomen (deep core)

Semitendinosus

O: Ischial Tuberosity in common with long head of bicep femoris

I: Upper fibial shaft

A: Extends thigh at hip, Flexes knee, medially rotates leg