1. The Muscular System Part A10

2. Interactions of Skeletal Muscles
Skeletal muscles work together or in opposition
Muscles only pull (never push)
As muscles shorten, the insertion generally moves toward the origin
Whatever a muscle (or group of muscles) does, another muscle (or group) “undoes”

3. Muscle Classification: Functional Groups
Prime movers – provide the major force for producing a specific movement
Antagonists – oppose or reverse a particular movement
Synergists
Add force to a movement
Reduce undesirable or unnecessary movement
Fixators – synergists that immobilize a bone or muscle’s origin

4. Naming Skeletal Muscles
Location of muscle
Shape of muscle – deltoid = triangle
Relative size – maximus, minimus, longus
Direction of fibers relative to body or bone axis
rectus – parallel
Transversus - perpendicular
Oblique – angle
Number of origins – biceps = two origins
Location of attachment –points of origin or insertion
Action – flexor, extensor, abductor, adducer etc…

5. Arrangement of Fascicles
Figure 10.1

6. Bone-Muscle Relationships: Lever Systems
Lever – a rigid bar that moves on a fulcrum, or fixed point
Effort – force applied to a lever
Load – resistance moved by the effort

7. Bone-Muscle Relationships: Lever Systems
Mechanical advantage
Effort is less than load
Figure 10.2a

8. Bone-Muscle Relationships: Lever Systems
Mechanical disadvantage
Effort is greater than load
Figure 10.2b

9. Lever Systems: First Class
Examples of both mechanical advantage and disadvantage
Figure 10.3a

10. Lever Systems: Second Class
Always a mechanical advantage
Figure 10.3b

11. Lever Systems: Third Class
Always a mechanical disadvantage
Figure 10.3c

12. Major Skeletal Muscles: Posterior (dorsal) View
27 superficial muscles divided into 7 body regions
Figure 10.5b

13. Major Skeletal Muscles: Anterior (ventral) View
40 superficial muscles divided into 10 body regions
Figure 10.4b

14. Shoulder Muscles
Prime movers
Figure 10.13a

15. Shoulder Muscles
Figure 10.13b

16. Shoulder Muscles
Rotator cuff muscles
Figure 10.14d

17. Muscles of the Neck: Head Movements
Major head flexor
Lateral head movements
Figure 10.9a

18. Muscles of the Neck: Head Movements
Head extension
Figure 10.9b

19. Muscles of Respiration
Internal intercostals – deep layer that aids in forced expiration
External intercostals – superficial layer that lifts the rib cage
Figure 10.10a

20. Muscles of Respiration: The Diaphragm
Diaphragm – most important muscle in inspiration
Figure 10.10b

21. Muscles of the Abdominal Wall
Figure 10.11a

22. Muscles of the Abdominal Wall
Figure 10.11b

23. Muscles Crossing Hip and Knee Joints
Most anterior compartment muscles of the hip and thigh flex the femur at the hip and extend the leg at the knee
Posterior compartment muscles of the hip and thigh extend the thigh and flex the leg
The medial compartment muscles all adduct the thigh
These three groups are enclosed by the fascia lata

24. Movements of the Thigh at the Hip: Flexion and Extension
The ball-and-socket hip joint permits flexion, extension, abduction, adduction, circumduction, and rotation
Most important thigh flexors
iliopsoas (prime mover),
tensor fasciae latae,
rectus femoris
The medially located adductor muscles and sartorius assist in thigh flexion

25. Movements of the Thigh at the Hip: Flexion and Extension
Thigh extension
hamstring muscles
biceps femoris, semitendinosus, & semimembranosus
Forceful extension is aided by the gluteus maximus

26. Movements of the Thigh at the Hip: Flexion and Extension
Figure 10.19a

27. Movements of the Thigh at the Hip: Other Movements
Abduction and rotation
gluteus medius & gluteus minimus,
antagonized by the lateral rotators
Thigh adduction by five adductor muscles
adductor magnus, adductor longus, & adductor brevis; the pectineus, & the gracilis

28. Movements of the Thigh at the Hip: Other Movements
Figure 10.20a

29. Movements of the Knee Joint
The sole extensor of the knee is the quadriceps femoris
The hamstring muscles flex the knee, and are antagonists to the quadriceps femoris
Figure 10.19a