Post on 07-Feb-2021
Chapter 10 Muscular System:
Gross Anatomy
AP1 Chapter 10 1
Chapter 10 Outline
I. General Principles A. Muscle Shapes B. Nomenclature C. Movements accomplished by muscles D. Muscle Anatomy
AP1 Chapter 10 2
I. General Principles • Most skeletal muscles
extend from one bone to another & cross at least 1 joint. – 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
AP1 Chapter 10 3
Fig 10.27 Pg 353
Fig 10.15 Pg 339
I. G
ener
al P
rinci
ples
Pg 321 Figure 10.1
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: – 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
AP1 Chapter 10 4
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).
AP1 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 AP1 Chapter 10 6
A. Muscle Shapes
• 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
AP1 Chapter 10 7
Pg 322 Fig 10.2
A. Muscle Shapes 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
AP1 Chapter 10 8
Pg 322 Fig 10.2
A. Muscle Shapes 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
AP1 Chapter 10 9
Pg 322 Fig 10.2
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
B. Nomenclature
AP1 Chapter 10 10
Examples of shapes pg 323 Fig 10.3
AP1 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 1. Class I 2. Class II 3. Class III
AP1 Chapter 10 12
Resistance
Load (L)
Lever Systems & Leverage • Lever
– Ridged structure that can move around a fixed point
• Fulcrum – The Fixed Point (Elbow)
• Effort (Pull) – Causes the movement – Contraction of the Bicep
• Resistance (Weight) – Opposes the movement
Resistance
Load (L)
3 types of Levers Determined by positions of the Fulcrum, the effort, & the Load
1st Class Lever • F is between the L
and the E • Seesaw
3rd Class Lever • E is between the F
and the L • Forceps
2nd Class Lever • L is between the F
and the E • Wheelbarrow