Skeletal Muscle Actions Skeletal muscles generate a great variety of body movements. The action of each muscle mostly depends upon the kind of joint it is associated with and the way the muscle is attached on either side of that joint.

Antagonistic Pairs Muscles work in antagonistic pairs. This means that they oppose each other in their action upon bones of the skeleton. Since all muscles move across at least one joint, antagonistic pairs move joints in opposite directions.

Antagonistic Pairs Muscles cannot push on a joint; they can only pull a joint in one direction. For example, the biceps can flex the elbow joint, but is unable to extend it. The extensor of the elbow is the triceps. Therefore, they oppose each other as antagonistic pairs.

The Origin The origin of any muscle is the bone to which a muscle is attached that remains stationary or does NOT move. For example, the muscle which moves your jawbone as you chew ( the masseter) has its origin on the cheekbone (the zygomatic).

The Insertion The insertion of a muscle is the bone to which a muscle is attached that moves. While the origin of the masseter is the zygomatic, the insertion is on the jawbone itself, the mandible. During contraction, the muscle insertion moves toward the origin.

Origin and Insertion Origin – immovable end Insertion – movable end Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Origin – immovable end Insertion – movable end When a muscle contracts, its insertion is pulled toward its origin Coracoid process Origins of biceps brachii Tendon of long head Tendon of short head Biceps brachii Radius Insertion of biceps brachii

Interaction of Skeletal Muscles Prime mover (agonist) – primarily responsible for movement Synergists – assist prime mover Antagonist – resist prime mover’s action and cause movement in the opposite direction of the prime mover

Lifespan Changes Myoglobin, ATP, and creatine phosphate decline By age 80, half of muscle mass has atrophied Adipose cells and connective tissues replace muscle tissue Exercise helps to maintain muscle mass and function

Muscles of Facial Expression and Mastication Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epicranial aponeurosis Frontalis Epicranius Occipitalis Temporalis Orbicularis oculi Zygomaticus major Zygomaticus minor Masseter Buccinator Sternocleidomastoid Orbicularis oris Platysma (a) Temporalis Lateral pterygoid Medial pterygoid Buccinator (b) (c)

Muscles of Facial Expression and Mastication Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epicranial aponeurosis Frontalis Epicranius Occipitalis Temporalis Orbicularis oculi Zygomaticus major Zygomaticus minor Masseter Buccinator Sternocleidomastoid Orbicularis oris Platysma (a) Temporalis Lateral pterygoid Medial pterygoid Buccinator (b) (c)

Muscles of Facial Expression and Mastication Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epicranial aponeurosis Frontalis Epicranius Occipitalis Temporalis Orbicularis oculi Zygomaticus major Zygomaticus minor Masseter Buccinator Sternocleidomastoid Orbicularis oris Platysma (a) Temporalis Lateral pterygoid Medial pterygoid Buccinator (b) (c)

Muscles of Facial Expression and Mastication Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Epicranial aponeurosis Frontalis Epicranius Occipitalis Temporalis Orbicularis oculi Zygomaticus major Zygomaticus minor Masseter Buccinator Sternocleidomastoid Orbicularis oris Platysma (a) Temporalis Lateral pterygoid Medial pterygoid Buccinator (b) (c)

Muscles That Move the Head and Vertebral Column Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Splenius capitis (cut) Longissimus capitis Semispinalis capitis Spinalis capitis Splenius capitis Spinalis cervicis Semispinalis capitis (cut) Longissimus cervicis Iliocostalis cervicis Iliocostalis thoracis Longissimus thoracis Spinalis thoracis Iliocostalis lumborum Quadratus lumborum

Muscles That Move the Head and Vertebral Column Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Splenius capitis (cut) Longissimus capitis Semispinalis capitis Spinalis capitis Splenius capitis Spinalis cervicis Semispinalis capitis (cut) Longissimus cervicis Iliocostalis cervicis Iliocostalis thoracis Longissimus thoracis Spinalis thoracis Erector Spinae Iliocostalis lumborum Quadratus lumborum

Muscles That Move the Pectoral Girdle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trapezius Levator scapulae Supraspinatus Deltoid Infraspinatus Teres minor Teres major Rhomboid minor Rhomboid major Latissimus dorsi (a) Rhomboid minor Trapezius Deltoid Rhomboid major Latissimus dorsi (b) (c) (d)

Muscles That Move the Pectoral Girdle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trapezius Levator scapulae Supraspinatus Deltoid Infraspinatus Teres minor Teres major Rhomboid minor Rhomboid major Latissimus dorsi (a) Rhomboid minor Trapezius Deltoid Rhomboid major Latissimus dorsi (b) (c) (d)

Muscles That Move the Pectoral Girdle Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trapezius Levator scapulae Supraspinatus Deltoid Infraspinatus Teres minor Teres major Rhomboid minor Rhomboid major Latissimus dorsi (a) Rhomboid minor Trapezius Deltoid Rhomboid major Latissimus dorsi (b) (c) (d)

Major Skeletal Muscles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Frontalis Orbicularis oculi Zygomaticus Masseter Orbicularis oris Trapezius Sternocleido- mastoid Deltoid Pectoralis major Serratus anterior Biceps brachii Brachialis External oblique Brachioradialis Rectus abdominis Tensor fasciae latae Sartorius Rectus femoris Gracilis Adductor longus Vastus medialis Vastus lateralis Fibularis longus Gastrocnemius Tibialis anterior Soleus Extensor digitorum longus

Major Skeletal Muscles Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Temporalis Occipitalis Sternocleidomastoid Trapezius Deltoid Teres minor Infraspinatus Teres major Brachialis Triceps brachii Rhomboid Latissimus dorsi External oblique Gluteus medius Gluteus maximus Adductor magnus Biceps femoris Gracilis Semitendinosus Semimembranosus Vastus lateralis Sartorius Gastrocnemius Fibularis longus Calcaneal tendon Soleus

Muscles That Move the Arm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trapezius Sternocleidomastoid Pectoralis minor Deltoid Internal intercostal Pectoralis major External intercostal Serratus anterior Linea alba (band of connective tissue) Rectus abdominis Internal oblique External oblique Transversus abdominis Aponeurosis of external oblique

Muscles That Move the Arm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Levator scapulae Supraspinatus Spine of scapula Deltoid Infraspinatus Teres minor Teres major Long head of triceps brachii (a) Lateral head of triceps brachii Levator scapulae Supraspinatus Infraspinatus Teres minor Teres major Triceps brachii (b) (c) (d)

Muscles That Move the Forearm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Trapezius Clavicle Subscapularis Deltoid Coracobrachialis Medial border of scapula Short head of biceps brachii Long head of biceps brachii Brachialis (a) Subscapularis Coracobrachialis Biceps brachii (short and long heads) Brachialis (b) (c) (d)

Muscles That Move the Forearm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Biceps brachii Brachialis Supinator Pronator teres Brachioradialis Brachioradialis Flexor carpi radialis Extensor carpi radialis longus Flexor carpi ulnaris Palmaris longus Flexor carpi ulnaris Flexor digitorum superficialis Pronator quadratus Flexor retinaculum (a) (b) Flexor digitorum superficialis Pronator teres Flexor carpi radialis Pronator quadratus (c) (d) (e)

Cross Section of the Forearm Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Abductor pollicis longus m. Extensor digitorum m. Flexor pollicis longus m. Extensor carpi ulnaris m. Radius Extensor pollicis longus m. Extensor carpi radialis brevis m. Ulna Extensor carpi radialis longus m. Flexor digitorum profundus m. Pronator teres m. Ulnar n. Plane of section Brachioradialis m. Ulnar a. Radial n. Flexor carpi ulnaris m. Radial a. Median n. Flexor carpi radialis m. Flexor digitorum superficialis m. Anterior Palmaris longus m.

Muscles That Move the Hand Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Triceps brachii Brachioradialis Extensor carpi radialis longus Flexor carpi ulnaris Extensor carpi ulnaris Extensor carpi radialis brevis Extensor digitorum Extensor carpi radialis longusand brevis Extensor retinaculum Extensor carpi ulnaris Extensor digitorum (a) (b) (c)

Muscles of the Abdominal Wall Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Rectus abdominis External oblique Internal oblique Transversus abdominis Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Peritoneum Transversus abdominis Linea alba Internal oblique (a) External oblique Skin (e) Rectus abdominis External oblique Internal oblique Transversus abdominis (b) (c) (d)

Muscles of Pelvic Outlet Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Scrotum Penis Clitoris Ischiocavernosus Urethral orifice Bulbospongiosus Vaginal orifice Superficial transversus perinei Anus Anus Levator ani Gluteus maximus External anal sphincter (a) (b) Coccyx Coccygeus Levator ani Rectum Vagina Urethra Urogenital diaphragm Symphysis pubis (c)

Muscles That Move the Thigh Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Psoas major Psoas minor Iliacus Pectineus Tensor fasciae latae Sartorius Adductor longus Rectus femoris Sartorius Adductor magnus Vastus lateralis Vastus intermedius Quadriceps femoris tendon (patellar tendon) Gracilis Patella Vastus medialis Patellar ligament (a) (b) Adductor brevis Adductor longus Gracilis Adductor magnus (c) (d) (e) Psoas major Psoas minor Iliacus (f) (g)

Muscles That Move the Thigh Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gluteus medius Tensor fasciae latae Gluteus maximus Sartorius Rectus femoris Vastus lateralis Biceps femoris Iliotibial tract (band) (a) Gluteus medius Gluteus minimus Gluteus maximus Piriformis (b) (c) (d)

Muscles That Move the Leg Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Gluteus medius Gluteus maximus Adductor magnus Vastus lateralis covered by fascia Gracilis Semitendinosus Biceps femoris Semimembranosus Sartorius Gastrocnemius Semitendinosus (a) Biceps femoris (long head) Semimembranosus Biceps femoris (short head) (b) (c)

Muscles That Move the Leg Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lateral Medial Semitendinosus m. Long head of biceps femoris m. Semimembranosus m. Short head of biceps femoris m. Gracilis m. Adductor magnus m. Sciatic n. Plane of section Adductor longus m. Great saphenousv. Shaft of femur Femoralv . and a. Sartorius m. Vastus lateralis m. Vastus medialis m. Vastus intermedius m. Adipose tissue Rectus femoris m. Skin Anterior

Muscles That Move the Leg Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Plantaris Iliotibial tract (band) Soleus Semitendinosus Biceps femoris Semimembranosus Gastrocnemius Gracilis Sartorius Gastrocnemius: Medial head Lateral head Fibularis longus (b) (c) Soleus Calcaneal tendon Fibularis brevis Flexor digitorum longus Tibialis posterior Flexor retinaculum Flexor digitorum longus Calcaneus Fibular retinacula (a) (d) (e)

Muscles That Move the Foot Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Patella Patellar ligament Tibialis anterior Gastrocnemius Fibularis longus Extensor digitorum longus Soleus Fibularis brevis Tibia Extensor retinacula (a) Extensor digitorum longus Tibialis anterior Fibularis tertius Extensor hallucis longus (b) (c) (d)

Muscles That Move the Foot Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Biceps femoris Vastus lateralis Gastrocnemius Head of fibula Tibialis anterior Fibularis longus Soleus Extensor digitorum longus Calcaneal tendon Fibularis brevis Extensor retinacula Fibularis tertius Fibular retinacula (a) Fibularis longus Fibularis brevis (b) (c)