The Muscular System-Gross Anatomy Over 600 Human skeletal muscles I. Muscular terminology Myology – the study of muscles Kinesiology – the study of skeletal muscle action, physiology and body mechanics (biomechanics) Nerve supply – part of the peripheral nervous system. Either cranial nerves or spinal nerves.

Parts of a Skeletal Muscle Origin –attachment to stationary end of muscle Belly –thicker, middle region of muscle Insertion –attachment to mobile end of muscle

II. Coordinated Muscle Actions A. Prime mover –produces most of force B. Synergist aids the prime mover –stabilizes the nearby joint –modifies the direction of movement that occurs C. Antagonist –opposes the prime mover D. Fixator –prevents movement of bone that prime mover is attached to, joint stabilizer

Muscle Actions during Elbow Flexion Prime mover = brachialis Synergist = biceps brachii Antagonist = triceps brachii Fixator = muscle that holds scapula firmly in place such as rhomboids

III. How Muscles are Named System of Latin names developed in 1895 –updated since then, last muscle English names for muscles are slight modifications of the Latin names. LocationSize ActionDirection of Fibers Shape Number of heads Origin and Insertion

Skeletal Muscle Shapes Fusiform muscles Convergent muscle Parallel muscles

Skeletal Muscle Shapes (2) Circular muscles Pennate muscles

IV. Gross Anatomy of Skeletal Muscles- chapter 10

Major Skeletal Muscles: Anterior View

Major Skeletal Muscles: Posterior View

Muscles of Facial Expression Small muscles that insert into the dermis Innervated by facial nerve (VII) Paralysis causes face to sag Found in scalp, forehead, around the eyes, nose and mouth, and in the neck

Occipitofrontalis is found in the scalp. Frontalis raises the eyebrows while Occipitalis fixes the epicranial aponeuronesis which is a CT covering of the cephalic region Muscles of the Scalp and Forehead Frontalis Occipitalis

Muscles around the Eyes Nasalis Orbicularis oculi closes the lid. Nasalis widens nostrils, wrinkles nose Orbicularis Oculi

Orbicularis oris encircles mouth called the “kissing muscle” because it is used to pucker lips Zygomaticus group curl corner of mouth up in smile “smiling muscle” Risorius- syngerist to zygomaticus, “laughter muscle” Buccinator keeps food on top of teeth, blowing & sucking, “trumpeter’s muscle”, used for facial expression and chewing Depressor Group (2)- draws angle of mouth downward Muscles around the Mouth Orbicularis oris Risorius Depressor labii inferioris Buccinator Zygomaticus major Depressor anguli oris Levator labii superioris

Some of the Muscles used in Facial Expression Tenses neck

Muscles of Mastication Major muscles arise from skull & insert on mandible Temporalis & Masseter elevate the mandible Medial & Lateral Pterygoids help elevate, but produce excursion movement, used to grind Buccinator- holds food in mouth Temporalis Masseter Lateral pterygoid Medial pterygoid

Neck Muscles Platysma- tenses neck Sternocleidomastoid Turn head to look behind or touch ear to shoulder

Muscles of Respiration -- Diaphragm Muscular dome between thoracic and abdominal cavities Contraction flattens it –increases the vertical dimension of the thorax drawing air into the lungs –raises the abdominal pressure to help expel urine, feces and facilitating childbirth

Muscles of Respiration -- Intercostals External intercostals –pull ribcage up & outward during inspiration Internal intercostals –pull ribcage downward during forced expiration

Muscles of the Abdomen 4 Pairs of sheetlike muscles –external oblique –internal oblique –transverse abdominis –rectus abdominis

Rectus Abdominis & External Oblique External oblique Superficial, Downward anteriorly Compresses abdomen Rotates trunk laterally Rectus abdominis –vertical, straplike –Six pack abs –linea alba (CT) Compresses abdomen External oblique Rectus abdominis

Internal Oblique -Transverse Abdominis Internal oblique –anteriorly –Upwards deeper Compresses abdomen Transverse abdominis –horizontal fiber orientation –deepest layer Compresses abdominal contents Transverse abdominis Internal oblique

Anterior Scapular Muscle Group Pectoralis Minor –protracts & depresses scapula –lifts ribs during forced expiration Serratus Anterior –abducts & rotates or depresses scapula –Throwing and pushing muscle –“boxer’s muscle”

Rhomboids –Retracts and rotates scapula, fixator of scapula Posterior Scapular Muscle Group Levator scapulae Elevates and retracts scapula Trapezius Raises and lowers Shoulders “shrugs shoulders”

Muscles Acting on the Humerus Muscles cross the shoulder joint to the humerus –Pectoralis major – prime mover of arm flexion adduction against resistance –Latissimus dorsi-prime mover of arm extension, powerful arm adductor (power stroke) Pectoralis majorLatissimus dorsi Major chest muscle Swimmer’s muscle Extends and Adducts humerus Flexes upper arm

Deltoid is prime mover of arm abduction, antagnostic to pectoralis major “shoulder pad muscle” 4 form the rotator cuff muscles that reinforce the shoulder joint capsule (supraspinatus, teres minor, infraspinatus, subscapularis) Muscles Acting on the Humerus

Muscles Acting on the Elbow Principal flexors –biceps brachii Inserts on radius –brachialis inserts on ulna, prime mover Synergistic flexor –Brachioradialis Flexors in order of strength- brachialis, biceps brachii, brachioradialis Extensor –triceps brachii inserts onto ulna

Muscles of the wrist and hand- examples Flex/extend wrist and fingers, adduct/abduct wrist Digitorum = inserts into fingers Carpi = inserts onto carpal bones Pollicis = inserts into thumb

Muscles of the wrist and hand- examples Extension of wrist and fingers, Adduct/abduct wrist Extension and abduction of thumb (pollicis) Brevis = short, Ulnaris = on ulna side of forearm Extensors

Muscles of Posterior Thigh Hamstring group (Biceps fermoris, semitendinosus, semimembranosus) Prime mover of Knee flexion

Muscles of the Anterior Thigh Sartorius Tailor’s muscle- crossing legs Quadriceps femoris- prime mover of knee extension and hip flexion (Rectus femoris, vastus lateralis, vastus medialis, vastus intermedialis) Tensor fasciae latae- abducts Gracilis- adducts thigh

Posterior Muscles Acting on the Hip Gluteus maximus –forms mass of the buttock –prime hip extensor –provides most of lift when you climb stairs Gluteus medius and gluteus minimus- abducts thigh and stabilizes pelvic girdle for walking Gluteus maximus Gluteus medius Iliotibial band(tensor fascia latae)- abducts thigh

Adductors of the Hip Joint 5 muscles act for adduction of the thigh Adductor magnus is also an extensor of hip joint Adductor brevis and Adductor longus adduct the femur Adductor longus Adductor brevis Adductor magnus

Anterior Compartment of the Leg Tibialis anterior = dorsiflexes and inverts foot Tibialis anterior

Posterior Compartment of the Leg Superficial Group of Plantar Flexors Gastrocnemius = flexes knee and plantar flexes ankle Gastrocnemius