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How many human skeletal muscle are there?
about 600
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Three kinds of muscle tissue
- 1. skeletal
- 2. cardiac
- 3. smooth
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Functions of the Muscles
- Movement
- Stability-antigravity muscles
- Control of openings and passageways- sphincter
- Heat production by skeletal muscles
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Connective Tissue of a Muscle
- Endomysium
- Perimysium
- Epimysium
- Fascia
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Endomysium
thin sleeve of loose connective tissue surrounding each muscle fiber.
allows room for capilliaries and nerve fibers to reach each muscle fiber
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Perimysium
slightly thicker layer of connective tissue
Fascicles- bundles of muscle fibers wrapped in perimysium
carry larger nerves and blood vessels, and stretch receptors
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Epimysium
- fibrous sheath surrounding the entire muscle
- outer surface grades into the fascia
- inner surface sends projections between fascicles to form perimysium
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Fascia
sheet of connective tissue that separates neighboring muscles or muscle groups from each other and the subcuyaneous tissue.
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Classification of Muscles According to Fascicle Orientation
- fusiform muscles
- parallel
- triangular (convergent)
- pennate
- circular (sphincters)
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Fusiform Muscles
thick in middle and tapered at the end
ex. biceps brachii, gastrocnemius
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Parallel Muscle
have uniform width and parallel fascicles
can span longer distances than other shapes
ex. rectus abdominis and zygomaticus major
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triangular muscle
fan-shaped broad at orgin and tapering to a narrow insertion
ex. pectoralis major, temporalis
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pennate muscle
- fascicles insert obliquely on a tendon (feather shaped)
- Unipennate, bipennate or multipennate
- ex. palmar interosseos, rectus femons deltoid
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circular muscles (sphincters)
- rind around body opening
- orbicularis oculi, urethral and anal sphincters
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Tendons-
- Indirect Attachment
- bridge the gap between muscle ends and bony attachment
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aponeurosis
tendon is a broad, flat sheet of tendon
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retinaculum
connective tissue band that tendons from separate muscles pass under
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Some skeletal muscle do not insert on bone, but in dermis of the skin muscles of facial expression
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Muscle Origins and Insertions
Origin- bony attachment at stationary end of muscle
Belly- thicker, middle region of muscle between origin and insertion
Insertion- bony attachment to mobile end of muscle.
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Functional Groups of Muscles
- action
- prime mover
- synergist
- antagonist
- fixator
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action
the effects produced by a muscle
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prime mover (agonist)
muscle that produces most of force during a joint action
ex. brachialis
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synergist
muscle that aids the prime mover
- stabilizes the nearby joint
- modifies the direction of movement
ex. biceps brachii
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antagonist
opposes the prime mover
- relaxes to give prime mover control over an action
- preventing excessive movement and injury
triceps brachii
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antagonistic pairs
muscles that act on opposite sides of a joint
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fixator
muscle that prevents movement of bone
ex. muscle that holds scapula firmly into place - Rhomboids
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Rhombus
shaped muscles associated with the scapula and are chiefly responsible for it retraction
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Intrinsic Muscles
entirely contained within a region, such as the hand
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extrinsic muscles
act on a designated region, but has its origin elsewhere
fingers-extrinsic muscles in the forearm
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Innervation of a muscle
refers to the identity of the nerve that stimulates it
enables the diagnosis of nerve, spinal cord, and brainstorm injuries from their effects on muscle function
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spinal nerves
- arise from the spinal cord
- emerge through intervertebrial foramina
- immediately branch into a posterior and anterior ramus
- innervate muscles below the neck
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plexus
weblike network of spinal nerves adjacent to the verebral column
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cranial nerves
- arise from the base of the brain
- emerge through skull foramina
- innervate the muscles of the head and neck
- numbered I to XII
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