1. The Muscular System Part 1
Chapter 10
The Muscular System Part 1
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2. Objectives Know the various functions of muscle
Know the structure of muscle and the various shapes muscles form
Understand how muscles attach to bone and what origin and insertion describe
Understand how muscles fit into functional groups
Know how muscles are named
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3. Functions Produces movement Posture and Stability
Control of body opening and passages
Generates heat
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4. Structure Macro to micro Epimysium Fascicles Muscle fibers (cells)
Wrapped by perimysium
Muscle fibers (cells)
Wrapped by endomysium
Myofibrils
Contractile element
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5. Muscle Shapes Determined by the orientation of the fascicles
Five main shapes
Fusiform
Parallel
Triangular
convergent
Pennate
Unipennate
Bipennate
Multipennate
Circular
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6. Muscle Attachments Two types of attachments Indirect Direct
Muscles connected to bones via visible tendons
Tendons merge with periosteum and bony matrix
Aponeurosis – broad sheet-like tendon
Retinaculum – band of connective tissue which tendons pass through
Direct
Muscle appears to be directly connected to the muscle with little space between them
Small microscopic gaps bridged by collagen fibers
Not always to bone, may be to fascia or the skin

7. Muscle Attachments
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8. Origins and Insertions
Origin – bony site of attachment that remains more stationary
Insertion – bony site of attachment that is more mobile
Belly – thick portion of muscle between attachment sites

9. Functional Groups of Muscles
Action – the effect produced by a muscle
To move or not to move
Four categories (based on action)
Prime mover (agonist)
Produces most of the force during a joint action
Synergist
Aids the prime mover by having similar effect on joint or stabilizing and focusing action of prime mover
Antagonist
Opposes the prime mover
Fixator
Muscle that prevents a bone from moving

10. Intrinsic and Extrinsic Muscles
Intrinsic muscles
Contained entirely within a specific region
Origin and insertion within same region
Extrinsic muscles
Have origin and insertions in different regions
Innervation
Spinal nerves – below the neck
Cranial nerves – head and neck

11. Naming Muscles Named according to various descriptive criteria
Location of muscle – indicate the bone or body region muscle associated with
Temporalis, intercostals
Shape of the muscle
Trapezius, deltoid

12. Naming Muscles Relative size of muscle Direction of muscle fibers
Maximus, minimus, longus (long), brevis (short)
Direction of muscle fibers
Named in relation to a line running the length of the body
Rectus, transverse, oblique
Number of origins (heads)
Bi, tri, and quad

13. Naming Muscles
Location of attachments – named according to their points of origin and insertion
Sternocleidomastoid
Origin is always first
Action – named according to the effect of the muscle
Flexor, extensor, adductor