Upper Body Muscle Anatomy

Upper Body Muscles

• The brachialis originates from the distal, anterior humerus, inserts at the coronoid process of the ulna, and its action is to flex the forearm.
• The biceps brachii originates from the supraglenoid tubercle and coracoid process of the scapula, inserts at the radial tuberosity, and performs flexion and supination of the forearm.
• The triceps brachii originates from the infraglenoid tubercle of the scapula and the posterior body of the humerus, inserts at the olecranon process of the ulna, and extends the forearm.
• The flexor carpi radialis originates from the medial epicondyle of the humerus, inserts at the 2nd and 3rd metacarpals, and flexes and abducts the wrist.
• The flexor carpi ulnaris originates from the medial epicondyle of the humerus, inserts at the 5th metacarpal, and flexes and adducts the wrist.
• The extensor carpi ulnaris originates from the lateral epicondyle of the humerus, inserts at the 5th metacarpal, and extends and adducts the wrist.
• The rectus abdominus originates from the pubic symphysis and crest, inserts at the external surfaces of cartilages of ribs 5-7 and the xiphoid process, and flexes the lumbar vertebrae, compressing the abdomen during forced expiration.
• The external obliques originate from the outer surface of ribs 5-12, interdigitating with the serratus anterior and linea alba, insert at the iliac crest, inguinal ligament, and anterior superior iliac spine, and compress the abdomen while acting as an opposite rotator of the thoracic vertebrae.
• The pectoralis major originates from the clavicle, sternum, and cartilage of the first 6 ribs and inserts at the greater tubercle; it acts to flex, adduct, and rotate the arm.
• The trapezius originates from the occipital bone and spines of C7 to all thoracic vertebrae, inserts at the clavicle and the acromion spine of the scapula, and extends the head and shrugs the shoulders.
• The latissimus dorsi originates from the spines of T6-L5, iliac, and sacral crests, inserts at the intertubercular groove, and extends, adducts, and rotates the arm.
• The deltoid originates from the clavicle, and the spine, acromion, and spine of the scapula; it inserts at the deltoid tuberosity of the humerus and abducts the arm.
• The rhomboid major raises and adducts the scapula.
• The serratus anterior protracts the shoulder anteriorly.
• The coracobrachialis flexes and adducts the arm at the shoulder.
• The teres major extends, adducts, and rotates the arm medially.
• The infraspinatus rotates the arm laterally.

Lower Body Muscles

• The gracilis originates from the inferior ramus and body of the pubis, inserts at the medial condyle of the tibia, and adducts the thigh and flexes the leg.
• The vastus intermedius originates from ¾ of the dorsal and dorsolateral surface of the femur, inserting at the mid-tibial tuberosity to extend the knee.
• The vastus medialis originates from medial intertrochanteric line to near the medial edge of Linea aspera and inserts at dorsomedial fascia of vastus intermedius, medial patella, and medial tibial tuberosity, extending the knee, displacing the patella medially and rotates femur laterally on tibia.
• The vastus lateralis origin is the Linea aspera up to the lateral margin of the greater trochanter and arching across the margin to the dorsal intertrochanteric line its fascia is the dorsal surface of the lateral intermuscular septum, its point of insertion is dorsolateral fascia of vastus intermedius, lateral patella, and lateral tibial tuberosity, it extends the knee, displaces the patella laterally and rotates femur medially on tibia.
• The rectus femoris, a 2-joint extensor of the knee, originates from the anterior inferior iliac spine and cranial lip of acetabulum with tendon insertion with the vastus intermedius and variably at 1/3 of its length above the knee on the cranial patella and tibial tuberosity, also flexes the hip.
• The sartorius (tailor's muscle) originates from the anterior superior iliac spine, inserts on the medial proximal tibia, and flexes the leg, flexing and rotating the thigh (cross legs).
• The tibialis anterior originates from the lateral condyle and body of the tibia, inserts at the 1st metatarsal and tarsal bones performing dorsiflexion and foot inversion.
• The gastrocnemius originates from the lateral and medial condyles of the femur, inserting at the calcaneus (via Achilles tendon) and plantarflexes the foot and flexes the leg
• The soleus originates from the head of the fibula and the medial proximal tibia, inserts at the calcaneus, and plantarflexes the foot (most important walking muscle).
• The gluteus maximus originates from the sacrum and ilium, inserts via the proximal femur to extend the hip during forceful exertion.
• The gluteus medius originates from the lateral surface of the ilium, inserts at the greater trochanter of the femur, and abducts and rotates the thigh and hip.
• The piriformis originates from the anterior surface of the lateral sacrum, inserts at the greater trochanter of the femur (along medial surface), and laterally rotates the thigh at the hip.

Head, Face and Neck Muscles

• The epicranius, a two-part muscle united by galea aponeurotica on superior and lateral aspects of the skull.
  • The frontalis originates from the galea aponeurosis, inserting on the skin above the supraorbital margin and raises the eyebrows.
  • The occipitalis originates from the occipital bone and mastoid process and inserts at the galea aponeurosis, pulling the scalp posteriorly.
• The temporalis originates from the temporal bone, inserts at the coronoid process of the mandible, and elevates (closes) the jaw.
• The orbicularis oris originates from the fascia associated with the maxillae, mandible, and lips, inserts at the muscles and skin at the angle of the mouth (modiolus), and purses and puckers the lips.
• The buccinator (trumpeter's muscle) originates from the alveolar processes of the posterior mandible and maxillae, inserts at the orbicularis oris muscle, and compresses the cheek when blowing or sucking.
• The zygomatic major/minor:
  • The Minor originates from the ventral surface of the zygomatic bone, inserts at the skin of the nasolabial groove and upper lip, and elevates the upper lip laterally.
  • The Major originates from the ventral part of the zygomatic arch, inserts at the modiolus (corner) of the mouth, and pulls upward and laterally on the modiolus at the mouth corners.
• The orbicularis oculi originates from the medial wall of the orbit, inserts on the tissue of the eyelid, and closes the eye.
• The masseter originates from the zygomatic arch, inserts at the angle and ramus of the mandible, and closes the jaw and protracted the mandible.