Chapter 10 Muscular System Gross Anatomy AP 1

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Chapter 10 Muscular System: Gross Anatomy AP 1 Chapter 10 1

Chapter 10 Muscular System: Gross Anatomy AP 1 Chapter 10 1

Chapter 10 Outline I. General Principles A. B. C. D. Muscle Shapes Nomenclature Movements

Chapter 10 Outline I. General Principles A. B. C. D. Muscle Shapes Nomenclature Movements accomplished by muscles Muscle Anatomy AP 1 Chapter 10 2

I. General Principles • Most skeletal muscles extend from one bone to another &

I. General Principles • Most skeletal muscles extend from one bone to another & cross at least 1 joint. Fig 10. 27 Pg 353 – Some aren’t facial muscles attach to bone on one end & the skin on the other (moves the face) • Muscle contraction causes most body movements by pulling 1 bone toward the other across a movable joint. • ACTION: movement accomplished by a muscle when it contracts Fig 10. 15 Pg 339 AP 1 Chapter 10 3

I. General Principles Muscle Terminology • Origin: – (fixed end, or head) usually both

I. General Principles Muscle Terminology • Origin: – (fixed end, or head) usually both the most stationary & most proximal end of the muscle. (some have multiple) • Insertion: – (Mobile end) usually the most distal end attached to the bone undergoing the most movement. • Belly: Pg 321 Figure 10. 1 – Region between the origin & insertion • Tendon: – Responsible for attaching muscle to bone – Long cable-like structures; broad sheet-like structures called aponeuroses; or short, almost non -existent structures 4 AP 1 Chapter 10

I. General Principles • Muscles (much like the movement discussed in Chapter 8) oppose

I. General Principles • Muscles (much like the movement discussed in Chapter 8) oppose each other. • Agonist: – Muscle accomplishing 1 movement (biceps brachii) • Antagonist: – Muscle opposing the movement of the agonist (Triceps brachii). AP 1 Chapter 10 5

I. General Principles • Muscles also tend to functions in groups to accomplish specific

I. General Principles • Muscles also tend to functions in groups to accomplish specific movements: – Synergists: members of a group of muscles working together to prod a mvmt. – Prime Mover: the muscle responsible for the major role accomplishing the desired movement – Fixators: muscles that holds one bone in place relative to the body while (normally) a more distal bone is moved – Example: • Synergists: biceps brachii & brachialis fxn in elbow flexion • Prime mover: Brachialis • Fixators: muscles in the scapula to keep shoulder stationary while humerus is moving AP 1 Chapter 10 6

A. Muscle Shapes Pg 322 Fig 10. 2 • Shape & size of a

A. Muscle Shapes Pg 322 Fig 10. 2 • Shape & size of a muscle influence the degree to wh/ it can contract & amount of force generated. • 3 major classes based on fasciculi orientation: 1. Pennate 2. Straight 3. Orbicular AP 1 Chapter 10 7

A. Muscle Shapes Pg 322 Fig 10. 2 1. Pennate – Bipennate: • Fasciculi

A. Muscle Shapes Pg 322 Fig 10. 2 1. Pennate – Bipennate: • Fasciculi arranged like the barbs of a feather on 2 sides of a common tendon – Semipennate: • All fasciculi are on 1 side of the tendon (unipennate) – Multipennate • Fasciculi arranged at many places around the central tendon • Ex/muscles extending from the knee AP 1 Chapter 10 8

A. Muscle Shapes Pg 322 Fig 10. 2 2. Straight – Fasciculi are arranged

A. Muscle Shapes Pg 322 Fig 10. 2 2. Straight – Fasciculi are arranged parallel to the long axis of the muscle. Result: – • • Muscles shorten to a greater degree because of the direct line to the tendon, but contract with less force b/c fewer total fascicles are attached to the tendon. Hyoid muscles 3. Orbicular – Fasiculi are arranged in a circle around an opening & act as sphincters to close and opening AP 1 Chapter 10 9

B. Nomenclature Muscles are named according to: A. Location: – Examples: Pectoralis (chest) ;

B. Nomenclature Muscles are named according to: A. Location: – Examples: Pectoralis (chest) ; Gluteus (Buttock); Brachial (arm) B. Size – Gluteus maximus (Large); Gluteus minimus (Small); Longus (long); Brevis (short) C. Shape – Deltoid (triangular); Quadratus (rectangular); teres (round) D. Orientation of fasciculi – Rectus (Straight); Oblique (slanting or inclined; diagonal) E. Origin & insertion – Brachioradialis (origin in arm [brachii] and insertion at radius) F. Number of heads – Biceps have 2 heads (Triceps 3 heads) G. Functions – – – Adductor moves toward midline Abductor moves away from midline Masseter Chews 10 AP 1 Chapter 10

Examples of shapes pg 323 Fig 10. 3 AP 1 Chapter 10 11

Examples of shapes pg 323 Fig 10. 3 AP 1 Chapter 10 11

C. Movements accomplished by muscles • Contracting muscles generate force that acts on bones

C. Movements accomplished by muscles • Contracting muscles generate force that acts on bones (Levers) across joints (Fulcrums) to create movement. • 3 classes Load (L) Resistance 1. Class I 2. Class II 3. Class III AP 1 Chapter 10 12

Lever Systems & Leverage • Lever – Ridged structure that can move around a

Lever Systems & Leverage • Lever – Ridged structure that can move around a fixed point • Fulcrum Load (L) – The Fixed Point (Elbow) • Effort (Pull) – Causes the movement – Contraction of the Bicep • Resistance (Weight) – Opposes the movement Resistance

3 types of Levers Determined by positions of the Fulcrum, the effort, & the

3 types of Levers Determined by positions of the Fulcrum, the effort, & the Load 1 st Class Lever • F is between the L and the E • Seesaw 2 nd Class Lever • L is between the F and the E • Wheelbarrow 3 rd Class Lever • E is between the F and the L • Forceps