HONORS ANATOMY & PHYSIOLOGYCHAPTER 10

The Muscular System

Anatomy of the Muscular System

• OriginMuscle attachment that remains

fixed• Insertion

Muscle attachment that moves• Action

What joint movement a muscle produces

i.e. flexion, extension, abduction, etc.

• For muscles to create a movement, they can only pull, not push

• Muscles in the body rarely work alone, & are usually arranged in groups surrounding a joint

• A muscle that contracts to create the desired action is known as an agonist or prime mover

• A muscle that helps the agonist is a synergist

• A muscle that opposes the action of the agonist, therefore undoing the desired action is an antagonist

An Overview of the Major Skeletal Muscles

Figure 7-11(a)

An Overview of the Major Skeletal Muscles

Figure 7-11(b)

Anatomy of the Muscular SystemMuscles of the Head and Neck

Figure 7-12(a)

Muscles of the Head & Neck

Muscles of facial expression lie in scalp and face just deep to skin or other muscles

overall are thin with variation in shape & strength

lateral scalp muscles are vestigial in humans

Muscles of the Scalp

Epicranius (Occipitalfrontalis) Frontal Belly:

covers forehead & dome of head raises eyebrows wrinkles forehead horizontally

Occipital Belly: covers posterior occiput pulls scalp posteriorly

Aponeurosis: flat, sheet –like tendon attaches frontal and occipital bellies

Muscles of the Face 1

Corrugator supercilii @ border of frontalis wrinkles forehead vertically

Orbicularis oculi flat, sphincter muscle surrounding orbit closes eye, blinking, squinting

Zygomaticus: major & minor diagonally across cheekbone mouth smiling

Muscles of Facial Expression 2

Risorius slender muscle inferior & lateral to zygomaticus tenses lips, draws corner of mouth laterally

Buccinator horizontal cheek muscle compresses cheek (whistling or sucking) holds food between cheek when chewing

Platysma thin, sheet-like superficial neck muscle tenses skin of neck, helps depress mandible, produces

downward sag of mouth

Muscles of Mastication

Masseter covers mandibular ramus prime mover of jaw closure

Temporalis fan-shaped, covers temporal, frontal, & parietal bones closes jaw

Pterygoids: Medial & Lateral along internal surface of mandible protrudes mandible, promotes side-to-side grinding

movementBuccinator

horizontal cheek/compresses cheek

Tongue Muscles

“glossus”: tongueGenioglossusHyoglossusStyloglossus

Muscles of the Anterior Neck & Throat

1. Digastric forms “V” shape under chin opens mouth & depresses mandible

2. Sternocleidomastoid attaches to sternum, clavicle, & mastoid process flexes & laterally rotates head

Muscles of Respiration

1. External Intercostals 11 pair lie between ribs running down & forward pull ribs toward each other to elevate rib cage

2. Internal Intercostals 11 pair between ribs, lie deep to & @ right angles

to #1 (run down & posterior draw ribs together & depress rib cage

Muscles of Respiration - 2

3. Diaphragm broad, flat , dome-shaped(when relaxed) muscle

prime mover of inspirationflattens on contractionforms floor of thoracic cavity

pierced by 3 structures:1. Aorta2. Inferior Vena Cava (IVC)3. Esophagus

Muscles of the Anterior Abdominal Wall

Rectus abdominis medial, superficial pair found between pubis & rib

cage segmented by 3 tendinous insertions flex vertebral column & compress abdominal wall

External oblique fibers run down & medially aponeurosis turns under inferiorly forming inguinal

ligament flex vertebral column & compress abdominal wall

Muscles of the Anterior Abdominal Wall - 2

Internal Oblique fibers run upward & medially flex vertebral column & compress abdominal wall

Transversus abdominis deepest of muscles in abdominal wall fibers run horizontally compresses abdominal contents

Superficial Muscles of the Thorax: Anterior

Pectoralis minor directly beneath pectoralis major with ribs fixed, draws scapula forward & downward

Serratus anterior fan-shaped, deep to scapula forms medial wall of axilla rotates scapula so its inferior angle moves laterally &

upward boxers muscle

Subclavius

Superficial Muscles of the Posterior Thorax

*Trapezious most superficial muscle of posterior thorax flat, triangular stabilizes, raises, & rotates scapula

Levator scapulae deep to trapezius,straplike elevates & adduct scapula

Rhomboids 2 diamond-shaped muscles deep to trapezius stabilize scapula

Muscles Crossing Shoulder Joint

Pectoralis major large, fan-shaped covering superior portion of chest prime mover of arm flexion, rotates arm medially,

adducts armDeltoid

forms rounding to shoulder prime mover of arm abduction when all its fibers

contract together

Muscles Crossing Shoulder Joint - 2

Latissimus dorsi broad, flat, triangular muscle of lumbar region prime mover of arm extension powerful arm adductor rotates arm at shoulder Swimming muscle

Muscles Crossing the Elbow: Posterior

Triceps brachii large , fleshy muscle 3-headed origin powerful arm extensor

Muscles Crossing Elbow: Anterior

Biceps brachii 2-headed fusiform muscle flexes elbow & supinates forearm

Brachialis deep to biceps major forearm flexor

Muscles Crossing the Hip Joint

Iliopsoas made up of 2 related muscles:1. Iliacus more lateral of the 2 prime mover for flexing thigh or flexing trunk on

thigh (taking a bow)1. Psoas longer & thicker of the 2 as motion for iliacus , also flexes vertebral column

laterally

Muscles Crossing the Hip - 2

Sartorius strap-like superficial muscle running obliquely across

anterior surface of thigh longest muscle in body crosses both hip & knee joint flexes, abducts, & laterally rotates thigh helps produce cross-legged position

Muscles of the Medial Compartment of Thigh

Adductors: Adductor magnus Adductor longus Adductor brevis all 3 adduct, flex, & medially rotate thigh

Muscles of the Anterior Compartment of Thigh

Quadriceps femoris 4 muscles that extend knee, flex thigh at hip, &

rotates thigh laterally, stabilizes hip joint1. Rectus femoris2. Vastus lateralis3. Vastis medius4. Vastus intermedius

Muscles of the Posterior Compartment of Thigh

Hamstrings: 3 muscles that together extend thigh and flex knee1. Biceps femoris2. Semitendinosus3. Semimembranous

Muscles of Anterior Compartment Lower Leg

Tibialis anterior: parallel to sharp anterior margin of tibia prime mover of dorsiflexion

Muscles of Anterior Compartment Lower Leg

Extensor digitorum longus lateral to tibialis anterior prime mover of toe extension

Muscles of the Posterior Compartment of Leg

Gastrocnemius: form proximal curve on back of leg plantar flexes foot

Soleus: broad, flat muscle, deep to gastrocnemius plantar flexes foot

Muscles of the Posterior Compartment of Leg

Tibialis posterior: thick, flat muscle , deep to soleus prime mover of foot inversion