Download Muscles Axial (Ch. 10)

Crafton Hills College
Muscles Axial (Ch. 10)
Part 1: The Muscular System - Characteristics, Functions & Anatomy
A. General Characteristics
1. Skeletal muscles work together or in opposition
2. Muscles only pull (never push)
3. As muscles shorten, Insertion moves toward origin
4. "For every muscle action, there is an opposite (if not always equal) reaction"
B. Muscle Classification
1. Functional Classification
a. Prime movers - provide the major force for producing a specific movement
b. Antagonists - oppose or reverse a particular movement
c. Synergists
i. Add force to a movement
ii. Reduce undesirable or unnecessary movement
2. Naming Muscles
a. Location of muscle - bone or body region associated with the muscle
b. Shape of muscle - e.g., the deltoid muscle (deltoid = triangle)
c. Relative size - e.g., maximus (largest), minimus (smallest), longus (long)
d. Direction of fibers - e.g., rectus (fibers run straight), transversus, and oblique (fibers run at
angles to an imaginary defined axis)
e. Number of origins - e.g., biceps (two origins) and triceps (three origins)
f. Location of attachments - named according to point of origin or insertion
g. Action - e.g., flexor or extensor, as in the names of muscles that flex or extend, respectively
C. Structure of Muscle
1. Arrangement of Fascicles
a. Parallel - fascicles run parallel to the long axis of the muscle (e.g., sartorius)
b. Pennate - short fascicles that attach obliquely to a central tendon running the length of the
muscle (e.g., rectus femoris)
c. Convergent - fascicles converge from a broad origin to a single tendon insertion (e.g.,
pectoralis major)
d. Circular - fascicles are arranged in concentric rings (e.g., orbicularis oris)
D. Lever Systems
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1. Terminology
a. Lever - a rigid bar that moves on a fulcrum, or fixed point
b. Effort - force applied to a lever
c. Load - resistance moved by the effort
2. Classes of Levers
a. First class - the fulcrum is between the load and the effort
b. Second class - the load is between the fulcrum and the effort
c. Third class - the effort is applied between the fulcrum and the load
Part 2: The Muscular System - AXIAL MUSCLES
A. Overview
1. Anterior: 40 superficial muscles divided into 10 regional areas
2. Posterior: 27 superficial muscles divided into 7 regional areas
3. Muscle Names & Structure
a. Name and description of the muscle often describe properties of the muscle
b. Origin and insertion: Always a joint between origin & insertion
c. Action: Best learned by acting out a muscle's movement on one's own body
d. Nerve supply - name of major nerve that innervates the muscle
B. Muscles of Facial Expression
1. Characteristics & Properties
a. All Facial Muscles innervated by cranial nerve VII (facial nerve)
b. Usually insert in skin (rather than bone), and adjacent muscles often fuse
2. Frontalis: Part of Epicranius (occipitofrontalis)
a. Pull the scalp forward
b. Origin: Galea aponeurotica (c.t.)
c. Insertion: Eyebrow skin & root of nose
d. Action: Scrunches forehead skin (frown)
3. Corrugator supercilii:
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Pull eyebrows medially and inferiorly
4. Orbicularis oculi: Around Eye - Blinking, squinting, eyebrows down
5. Orbicularis oris: Surrounds mouth - Closes mouth, purses & protrudes lips (whistling & kissing)
6. Zygomaticus: Raises corners of mouth upwards (smiling)
a. Origin:
Zygomatic bone
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b. Insertion: Skin/muscle at corner of mouth
7. Buccinator: Compresses cheek; holds food between teeth
C. Muscles of Mastication
1. Characteristics & Properties
a. Four pairs of muscles for mastication
i. Prime movers - Temporalis & Masseter
ii. Grinding movements - Pterygoids & Buccinators
b. All Innervated by cranial nerve V (Trigeminal nerve)
2. Temporalis: Closes jaw - Elevates & retracts mandible
3. Masseter: Closes jaw & elevates mandible
a. Origin:
Zygomatic arch & Maxilla
b. Insertion: Angle & Ramus of Mandible
4. Medial pterygoid: Elevates mandible, aids grinding
5. Lateral pterygoid: Projects jaw (anteriorly, aids grinding motion)
D. Extrinsic Tongue Muscles
1. Three major muscles anchor & move tongue
a. Styloglossus: Elevates & retracts
b. Hypoglossus: Depresses & retracts tongue
c. Genioglossus: Depresses & protracts tongue
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Innervated by cranial nerve XII (hypoglossal)
E. Muscles of Neck & Throat
1. Swallowing
a. Deep throat muscles
i. Floor of the oral cavity & Anchor the tongue
ii. Act together to depresses larynx & hyoid bone (aided by superficial throat muscles)
1) Sternohyoid
2) Stylohyoid
3) Mylohyoid
2. Head Movements
a. Sternocleidomastoid: Flexing neck forward
i. Origin: Sternum (manubrium) & Clavicle
ii. Insertion: Mastoid process (temporal bone)
iii. Lateral head movements are accomplished by the sternocleidomastoid and scalene
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muscles
b. Trapezius: Aids in extention of head, raises, rotates, adducts scapula
F. Trunk Movements
1. Deep Back Muscles
a. Erector spinae: Prime mover of back extension - lateral bending of the back
i. Illiocostalis: Inserts to mid-shaft of rib (lateral)
ii. Longissimus: Inserts to rib-head/transverse processes (intermediate)
iii. Spinalis: Inserts to spinous processes (medial)
b. Quadratus lumborum: Flexes vertebral column laterally
G. Muscles of Respiration
1. Primary function: Promote movement for breathing
2. External intercostals
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More superficial layer lifts rib cage & increases thoracic volume to allow inspiration
3. Internal intercostals
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Deeper layer aids in forced expiration
4. Diaphragm
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Most important muscle in inspiration
H. Muscles of the Abdominal Wall
1. Characteristics & Properties
a. Composed of 4 paired muscles (fasciae & aponeuroses):
i. Internal obliques
ii. External obliques
iii. Transversus abdominis
iv. Rectus abdominis
b. Overlapping angles of muscle fibers/fascicles = strength
c. Promotes urination, defecation, childbirth, vomiting, coughing, & screaming
I. Muscles of Pelvic Floor (Pelvic Diaphragm)
1. Pelvic diaphragm composed of two paired muscles
a. Levator ani
b. Coccygeus
i. Muscle(s) Properties:
1) Close the inferior outlet of pelvis
2) Support the pelvic floor
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3) Elevate the pelvic floor (helps release feces)
2. Sphincter muscles allow a person to have voluntarily control excretion of their waste
a. Sphincter urethrae:
Urination
b. External anal sphincter: Defecation
3. Erection: Muscles assisting in erection of clitoris & penis
a. Ischiocavernosus: Along pubic angle
b. Bulbospongiosus: Circumscribing clitoris or penis
J. Shoulder Muscles
1. Extrinsic Muscles
a. Anterior: pectoralis major, pectoralis minor, serratus anterior
b. Posterior: latissimus dorsi, trapezius muscles, levator scapulae, and rhomboids
c. Involved with movements of the scapula (elevation, depression, rotation, & lateral & medial)
d. Prime movers of shoulder elevation: trapezius and levator scapulae
2. Deep Muscles ("Intrinsic")
a. Nine muscles cross the shoulder joint and insert into the humerus
b. Prime movers include:
i. Pectoralis major: Arm flexion
ii. Pectoralis minor: Scapula down/forward OR Ribs up
iii. Latissimus dorsi: Arm extension
iv. Deltoid (as a whole): Arm abduction
3. Rotator cuff muscles
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Mainly to reinforce the capsule of shoulder
a. Supraspinatus:
Assist abduction of humerus
b. Infraspinatus:
Lateral rotation of humerus
c. Teres minor:
Lateral rotation of humerus
d. Subscapularis:
Rotates humerus
e. Coracobrachialis: Flexion & adduction of humerus
f. Teres major:
Extends & rotates humerus down&in
i. Act as synergists
ii. Do not help reinforce the shoulder joint
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