1. Muscular System: Gross Anatomy
Chapter 10
Muscular System:
Gross Anatomy
AP1 Chapter 10

2. Chapter 10 Outline General Principles Muscle Shapes Nomenclature
Movements accomplished by muscles
Muscle Anatomy
AP1 Chapter 10

3. 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
Fig 10.27
Pg 353
Fig 10.15
Pg 339
AP1 Chapter 10

4. I. General Principles Muscle Terminology Origin: Insertion: Belly:
(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
I. General Principles
Pg 321 Figure 10.1
AP1 Chapter 10

5. 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

6. 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

7. 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:
Pennate
Straight
Orbicular
AP1 Chapter 10

8. A. Muscle Shapes Pennate Bipennate: Semipennate: Multipennate
Pg 322
Fig 10.2
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

9. A. Muscle Shapes Straight Orbicular
Pg 322
Fig 10.2
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
Orbicular
Fasiculi are arranged in a circle around an opening & act as sphincters to close and opening
AP1 Chapter 10

10. Muscles are named according to:
B. Nomenclature
Muscles are named according to:
Location:
Examples: Pectoralis (chest) ; Gluteus (Buttock); Brachial (arm)
Size
Gluteus maximus (Large); Gluteus minimus (Small); Longus (long); Brevis (short)
Shape
Deltoid (triangular); Quadratus (rectangular); teres (round)
Orientation of fasciculi
Rectus (Straight); Oblique (slanting or inclined; diagonal)
Origin & insertion
Brachioradialis (origin in arm [brachii] and insertion at radius)
Number of heads
Biceps have 2 heads (Triceps 3 heads)
Functions
Adductor  moves toward midline
Abductor  moves away from midline
Masseter  Chews
AP1 Chapter 10

11. Examples of shapes pg 323 Fig 10.3
AP1 Chapter 10

12. C. Movements accomplished by muscles
Contracting muscles generate force that acts on bones (Levers) across joints (Fulcrums) to create movement.
3 classes
Class I
Class II
Class III
Load (L)
Resistance
AP1 Chapter 10

13. Lever Systems & Leverage
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
Load (L)
Resistance

14. 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
2nd Class Lever
L is between the F and the E
Wheelbarrow
3rd Class Lever
E is between the F and the L
Forceps