Muscles

Chapter 10

Fasicle arrangeme

nt

Parallel Muscle Tension

• Depends on total number of myofibrils

• Directly relates to cross section of muscle

• 1 in.2 (6.45 cm2) of cross section develops 50 lb (23 kg) of tension

Parallel Muscles Figure 11–1a

Convergent Muscles

• A broad area converges on attachment site (tendon, aponeurosis, or raphe)

• Muscle fibers pull in different directions, depending on stimulation

• e.g., pectoralis muscles

Convergent Muscles

Pennate Muscles

• Form an angle with the tendon• Do not move as far as parallel

muscles• Contain more myofibrils than

parallel muscles• Develop more tension than parallel

muscles

Pennate Muscles

Figure 11–1c, d, e

Circular Muscles

• Also called sphincters • Open and close to guard entrances

of body• e.g., obicularis oris

Circular Muscles

Levers

• Mechanically, each bone is a lever (a rigid, moving structure):– and each joint a fulcrum (a fixed

point)

• Muscles provide applied force (AF):– required to overcome resistance (R)

Functions of a Lever

• To change:– direction of an AF– distance and speed of movement

produced by an AF– effective strength of an AF

3 Classes of Levers

• Depend on the relationship between applied force, fulcrum, and resistance:– first class– second class– third class

First-Class Levers

Figure 11–2a

First-Class Levers

• Seesaw is an example• Center fulcrum between applied

force and resistance• Force and resistance are balanced

Second–Class Levers

Second-Class Levers

• Wheelbarrow is an example• Center resistance between applied

force and fulcrum• A small force moves a large weight

Third-Class Levers

Figure 11–2c

Third-Class Levers

• Most common levers in the body• Center applied force between

resistance and fulcrum• Greater force moves smaller

resistance• Maximizes speed and distance

traveled

Physics of levers

Origins and Insertions

• Muscles have 1 fixed point of attachment (origin) and 1 moving point of attachment (insertion)

• Most muscles originate or insert on the skeleton

• Origin is usually proximal to insertion

Actions

• Movements produced by muscle contraction

• Body movements – e.g., flexion, extension, adduction,

etc.

• Described in terms of bone, joint, or region

Descriptive Names for Skeletal Muscles

1. Location in the body2. Origin and insertion3. Fascicle organization4. Relative position5. Structural characteristics6. Action

Muscles:anterior

Muscles:posterior

Muscles of Facial Expression Figure 11–4a

Muscles of Facial Expression Figure 11–4b

Extrinsic Eye Muscles

• Also called extra-ocular musclesFigure 11–5a, b

Muscles of Mastication

Anterior Muscles of the Neck

Figure 11–9

Muscles of the

Vertebral Column

Figure 11–10a

Muscles of the Vertebral Column

Oblique and Rectus Muscles

• Lie within the body wall Figure 11–11a, b

Oblique and Rectus Muscles Figure 11–11a, c

The Appendicul

ar Muscles

Figure 11–13a

The Appendicul

ar Muscles

Muscles that Move the Arm

Figure 11–15a

Muscles that Move the Arm

Muscles that Move

the Forearm

and Hand

Figure 11–16a

Muscles that Move

the Forearm and Hand

Figure 11–16b

Muscles that Move the Hand and

Fingers

Muscles that Move the Hand and Fingers

Muscles that Move the Thigh Figure 11–19a, b

Muscles that Move the Thigh

Muscles that Move the

Leg

Figure 11–20a

Muscles that Move the Leg

Figure 11–20b, c

Muscles that Move the Foot and Toes

Muscles that Move the Foot and Toes

Up next …

Nervous System Histology