Chapter 10 Muscular System Gross Anatomy AP 1
- Slides: 14
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 accomplished by muscles Muscle Anatomy AP 1 Chapter 10 2
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 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 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 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 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 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 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) ; 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
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 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 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
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