OBJECTIVES

At the end of the lecture, students should be able to: Describe the main criteria of skeletal muscles. Describe the attachments of skeletal muscles. Describe the different directions of skeletal muscle fibers. Describe the mode of action of skeletal muscles. Describe briefly the naming of skeletal muscles. Describe briefly the nerve supply of skeletal muscles.

Muscular System

Composed of two main types : Involuntary

Smooth: Found in the walls of viscera. Cardiac: Found only in the heart.

Voluntary Skeletal

Main Criteria of Skeletal Muscles

VoluntaryStriatedAttached to skeletonProduce movement of skeletonSupplied by somatic nerves

Attachments

MOSTLY TWO:MOSTLY TWO: ORIGINORIGIN

Least movable Mostly fleshy Proximal end

INSERTIONINSERTION Most movable Mostly fibrous Distal end

Types of Attachments

Tendons o Cords of fibrous tissue.

Aponeurosis o A thin broad and strong sheet

of fibrous tissue.Raphe

o An interdigitation of the tendinous ends of the flat muscles.

Muscles are attached to bones, cartilage or ligaments by:

Directions of Muscle Fibers

Parallel to body midline More range of movementMore range of movement, less

powerful. Pennate (Pennate (Penniform musclePenniform muscle) )

oblique to body midline More powerfulMore powerful, less range of

movement.1. Unipennate (some muscles in hands).

2. Bipennate (quadriceps muscle).

3. Multipennate (Deltoid muscle).

parallel

Mode of Actions

Prime mover (Agonist):Prime mover (Agonist):It is the chief muscle

responsible for a particular movementExampleExample:: Quadriceps Femoris

is the prime mover for extension of the knee joint

Mode of Actions

Antagonist : Antagonist : It opposes the action of the

prime mover.Before contraction of prime

mover, antagonist must be relaxed.ExampleExample: : Biceps Femoris

(Flexor of knee) opposes the action of quadriceps when the knee joint is extended.

Mode of Actions

Synergist :Synergist : Assist or prevents unwanted

movement in an intermediate joint crossed by the Prime Mover. (Sometimes it refers to as "neutralizers" because they help

cancel out, or neutralize, extra motion from the agonists to make sure that the force generated works within the desired plane of motion)

ExampleExample: : Biceps and brachioradialis. The bicep is the prime mover in elbow joint movement and the brachioradialis acts as a synergistic muscle to stabilize the joint, thus aiding in the motion.

Mode of Actions

Fixator :Fixator :Its contraction does not

produce movement by itself but it stabilizes the origin of the prime mover so that it can act efficiently.ExampleExample:: Muscles attaching the

shoulder girdle to the trunk contract to fix shoulder girdle, allowing deltoid muscle (taking origin from shoulder girdle) to move shoulder joint (humerus).

Naming of Muscles Size: Size:

1.1. Major or Maximus Major or Maximus (large) gluteus maximus

2.2. Minor or Minimus Minor or Minimus (small). gluteus minimus

3.3. LatissimusLatissimus (broad) (latissimus dorsi).

4. LongusLongus (long) (Adductor longus).

5.5. BrevisBrevis (short) (Adductor brevis).

Position:Position:1.1. PectoralisPectoralis (pectoral region)

Depth:Depth:1. Superficialis (superficial).2. Profundus (deep).3. Externus (external).

Naming of Muscles Shape:Shape:

1.1. DeltoidDeltoid (triangular).2.2. TeresTeres (rounded)3.3. Rectus Rectus (straight).

Number of Heads:Number of Heads:1.1. Biceps Biceps (2 heads).2.2. Triceps Triceps (3 heads).3.3. Quadriceps Quadriceps (4 heads).

Attachments:Attachments:1.1. Coracobrachialis Coracobrachialis (from coracoid process

to arm).Action:Action:

1.1. Flexor digitorum: Flexor digitorum: flexion of digits.

Nerve Supply

The nerves supplying the skeletal muscles are Mixed.

60% are Motor. 40% are Sensory. It contains some Autonomic fibers

(Sympathetic). The nerve enters the muscle at about

the middle point of its deep surface.

Summary Skeletal muscles are striatedstriated, voluntaryvoluntary muscles attachedattached

to to & movemove the skeleton.They have 2 attachments: originorigin & insertioninsertion.Their fibers may be parallelparallel or oblique (pennate)oblique (pennate) to the line.According to mode of action, they are classified as:

prime mover, antagonist, synergist or fixatorprime mover, antagonist, synergist or fixator.

They may be named according to: size, shape, number of heads, position, attachments, depth or action.size, shape, number of heads, position, attachments, depth or action.

They are supplied by a mixedmixed nerve.

Sample QuestionsQuestion # 1

Which statement is NOT true?

A. Origin muscles are least movable, mostly fleshy, distal end. B. Parallel muscles are more range of movement, more

powerful. C. Insertion muscles are most movable, mostly fibrous,

proximal end. D. Pennate muscles are less powerful, less range of

movement.

Sample QuestionsQuestion # 2

Which statement is true?

A. Agonist is the chief muscle responsible for a particular movement

B. Antagonist support the action of the prime mover.C. Synergist assist or prevents unwanted movement in an

intermediate joint crossed by the Antagonist. D. Fixator contraction does not produce movement by itself

but it stabilizes the origin of the Synergist mover so that it can act efficiently.

Questions!