Muscles of the Body

Muscles of the Body• Ligaments connect bone to

bone

• Tendons connect muscle to bone

• The origin of a muscle is the attachment of a muscle’s tendon to the stationary bone

• The insertion of a muscle is the attachment of the muscle’s other tendon to the moveable bone

• In producing movement, bones act as levers and joints function as the fulcrums of these levers

• Movement is produced by a mechanical advantage

Archimedes (287 - 212 B.C.)• Scientist, mathematician, and engineer of ancient

Greece

• Invented a planetarium

• Invented a hydraulic musical organ

• Invented the Screw of Archimedes, which moved water uphill

• Figured out while taking a bath how to tell whether King Hiero’s crown was made of gold, and ran naked through the streets shouting “Eureka!”

• Invented a machine to lever ships between the dock and the water

“Give me a lever long enough, and a place to stand, and I will move the earth.”

Fascicle Arrangement

Learn How Muscles Are Named!

Learn How Muscles Are Named!

Muscles of Facial Expression• Orbicularis oris = kissing

muscle

• Occipitofrontalis (frontal belly) = surprise muscle

• Zygomaticus major = smile muscle

• Buccinator = whistling muscle

• Orbicularis oculi = winking muscle

• Corrugator supercilii = scowl muscle

• Zygomaticus minor = snarl muscle

• Mentalis = pout muscle

• Risorius = grimace muscle

Botox!

Muscles That Move the Eyeballs• All rectus muscles originate on the common

tendinous ring attached to orbit around optical foramen

• Superior oblique originates on sphenoid

• Inferior oblique originates on maxilla

• All rectus muscles insert on the eyeball on the same side as their name

• Oblique muscles insert on the eyeball between the adjacent rectus muscles

Muscles of the Head and Neck

• Masseter elevates the mandible

• Temporalis elevates and retracts the mandible

• Medial pterygoid elevates and retracts the mandible

• Lateral pterygoid depresses and protracts the mandible

• Platysma depresses the mandible and also “pouts”

• Occipitofrontalis (occipital belly) draws scalp posteriorly

Muscles of the Head and Neck

• Omohyoid originates on the scapula and depresses the hyoid

• Sternohyoid originates on the clavicle and sternum, and depresses the hyoid

• Once again useful in speaking and swallowing

• Digastric elevates the hyoid and depresses the mandible

• Stylohyoid elevates the hyoid

• Both originate at least in part on the temporal bone, and insert on the hyoid

• Useful in speaking and swallowing

Muscles of the Head and Neck

• Sternocleidomastoid laterally extends and rotates the head to the side opposite the muscle

• Originates on the sternum and clavicle

• Inserts on the mastoid process of the temporal bone

Muscles That Move the Shoulder Girdle• Trapezius (posterior):

elevates and adducts the scapula

• Levator scapulae (posterior): elevates and rotates scapula

• Rhomboid major (posterior): elevates and adducts scapula

• Pectoralis minor (anterior): abducts scapula, elevates ribs 3 - 5

• Serratus anterior (anterior): abducts scapula, elevates ribs, the “boxer’s muscle”

Muscles That Move the Arm• Supraspinatus: assists in

abducting the arm

• Infraspinatus: laterally rotates and adducts arm

• Subscapularis: medially rotates arm

• Teres major: extends, adducts, and medially rotates arm

• Teres minor: extends, adducts, and laterally rotates arm

• Deltoid: abducts arm

Muscles That Move the Arm• Supraspinatus, infraspinatus,

subscapularis, and teres minor form the rotator cuff

• These muscles and their tendons form a cuff or sleeve around the shoulder joint

• The supraspinatus is most commonly affected

• The muscle tears, or suffers impingement of the tendon

• Common in baseball players, swimmers, tennis players, and various workers

Muscles That Move the Arm

The rotator cuff

Muscles That Move the Arm

• Pectoralis major: adducts and medially rotates the arm

• Originates on the clavicle, sternum, and costal cartilages

• Inserts on the humerus

• Latissimus dorsi: extends, adducts, and medially rotates the arm

• Originates on vertebrae, sacrum, ilium, and ribs

• Inserts on the humerus

Muscles That Move the Forearm

• Triceps brachii: extends forearm

• Lateral and medial heads originate on the humerus

• Long head originates on infraglenoid tubercle

• Insert on the olecranon process of the ulna

• Brachialis: flexes forearm

• Originates on the humerus

• Inserts on the ulna

• Biceps brachii: flexes and supinates forearm

• Short head originates on coracoid process of scapula

• Long head originates on tubercle above glenoid cavity

• Inserts on the radial tuberosity

Muscles That Move the Forearm

• Supinator: supinates forearm

• Originates on the lateral epicondyle of the humerus

• Inserts on the radius

• Pronator teres: pronates forearm

• Originates on the medial epicondyle of the humerus

• Inserts on the radius

• Brachioradialus: flexes the forearm, pronates and supinates back to neutral position

• Originates on the humerus

• Inserts on the radius

Muscles That Move the Wrist• Flexor digitorum

superficialis, Flexor carpi radialis, Flexor carpi ulnaris, and Palmaris longis

• All originate at least in part on the medial epicondyle of the humerus

• All insert on the carpals or phalanges

• Flexor pollicis longus flexes the thumb

• It originates on the interosseous membrane and inserts on the thumb

Muscles That Move the Wrist

• Extensor carpi radialis longus/brevis, Extensor carpi ulnaris, and Extensor digitorum all extend the hand and digits

• All originate at least in part on the lateral epicondyle of the humerus

• All insert on the metacarpals or phalanges

• Abductor pollicis longus abducts the hand and thumb, and extends the thumb

• It originates on the interosseous membrane and inserts on the first metacarpal

Muscles That Move the Wrist

• Extensor pollicis longus/brevis extend the thumb and abduct the hand

• Both originate at least in part on the interosseus membrane

• Both insert on the thumb

Muscles of the Thorax

• The diaphragm produces inhalation when it contracts, exhalation when it relaxes

• It originates on the xiphoid process, as well as some vertebrae and ribs

• It inserts on the central tendon

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Muscles of the Thorax• Contraction of the external

intercostals elevates the ribs during inhalation, relaxation depresses the ribs during exhalation

• They originate on the inferior border of the rib above, and insert on the superior border of the rib below

• Contraction of the internal intercostals draws the ribs together during exhalation

• They originate on the superior border of the rib below, and insert on the inferior border of the rib above

Muscles That Move the Thigh• Psoas major and iliacus flex

and rotate the thigh laterally

• Both insert on the lesser trochanter of the femur

• Tensor fasciae latae flexes and abducts the thigh

• It originates on the iliac crest and inserts on the tibia

• Pectineus flexes and adducts the thigh

• It originates on the pubis and inserts on the femur

• Adductor longus adducts and flexes the thigh

• It originates on the pubis and ischium and inserts on the femur

Muscles That Move the Thigh

• Adductor magnus adducts and laterally rotates the thigh

• It originates on the ischium and pubis and inserts on the linea aspera of the femur

• Gracilis adducts and medially rotates the thigh

• It originates on the pubis and inserts on the tibia

Muscles That Move the Thigh

• Gluteus maximus extends and laterally rotates the thigh

• It originates on the iliac crest, sacrum, and coccyx

• It inserts on the femur

• Gluteus medius abducts and medially rotates the thigh

• It originates on the ilium

• It inserts on the greater trochanter of the femur

Muscles That Move the Leg

• Sartorius flexes the leg, also flexes, abducts, and laterally rotates the thigh

• It originates on the ilium and inserts on the tibia

• Sartorius is the longest muscle in the body

• Rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius together form the quadriceps femoris, which extend the leg

• All originate on the ilium or femur

• All insert on the patella and the tibia

Muscles That Move the Leg• Biceps femoris flexes the leg and

extends the thigh

• The long head originates on the ischium and the short head on the femur

• Inserts on the tibia and fibula

• Semitendinosus and semimembranosus flex the leg and extend the thigh

• Both originate on the ischial tuberosity

• Both insert on the tibia

• All three muscles together are known as the hamstrings

Muscles That Move the Foot• Tibialis anterior dorsiflexes and

inverts the foot

• It originates on the tibia and inserts on the first metatarsal and cuneiform

• Soleus plantar flexes the foot

• It originates on the fibula and tibia and inserts on the calcaneus

• Fibularis longus/brevis (peroneus) plantar flex and evert the foot

• Fibularis longus originates on the tibia and fibula and inserts on the first metatarsal and first cuneiform

• Fibularis brevis originates on the fibula and inserts on the fifth metatarsal

Muscles That Move the Foot

• Gastrocnemius plantar flexes the foot, and flexes the leg

• It originates on the condyles of the femur and inserts on the calcaneus

• Flexor digitorum longus plantar flexes the foot and flexes the toes

• It originates on the tibia and inserts on the distal phalanges 2 - 5

• Flexor hallucis longus plantar flexes the foot and flexes the great toe

• It originates on the fibula and inserts on the great toe