skeletal muscle tissue and organization
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1) Describe the distinguishing characteristics of the different muscle tissues
2) Discuss the organization of skeletal muscle
3) Explain the micro-anatomy of a skeletal muscle fiber
4) Describe the fascicle arrangement in different types of muscle
5) Review general muscle terminology
Skeletal Muscle Tissue and Organization
main objectives:
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Muscle Muscle tissuetissue vs. Muscle as an vs. Muscle as an organorgan
One of the 4 primary tissue types
How many subtypes?
Made up of _____ tissue types.
> 700 skeletal muscles
Word roots:sarco mys
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Function of Skeletal MusclesFunction of Skeletal Muscles
1. Skeletal movement
2. Posture and body position
3. Support of soft tissues
4. Guarding of entrances & exits
5. Maintenance of body temperature
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Gross AnatomyGross Anatomy
Each skeletal muscle is wrapped by 3 concentric layers of connective tissue.
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Epi-, Peri-, and Endomysium
Are interwoven - Go over into tendon
Distinguish between:TendonAponeurosisLigament
Function: ProtectionBlood supplyInnervation
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Nerve and Blood Vessel Supply
Skeletal muscles are rich in nerves and blood vessels
Chemical communication at Synapsis (neuromuscular junction)
Synaptic terminal of axon meets motor end plate of muscle cell
Coiled capillaries are able to adapt to changes in length of muscle fiber
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Microanatomy of Skeletal Muscle FibersMicroanatomy of Skeletal Muscle Fibers
Some vocabulary:
Skeletal muscle fiber or myofiber
Sarcolemma
Sarcoplasm
Sarcoplasmic reticulum
Myofibril
Myofilaments
Fig 9-3
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Myofiber Myofiber (( 100µm) 100µm) Myofibrils Myofibrils (( 1-2 µm) 1-2 µm) MyofilamentsMyofilaments
Actin & MyosinActin & Myosin
Myofilaments
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SarcomeresSarcomeres
Thick and Thin Filaments are organized in repeating functional units = ______
Each myofibril has linear arrangement of ~ 10,000 sarcomers
Banded appearance (striation) due to arrangement of thick and thin filaments
Interaction of thick and thin filaments responsible for skeletal muscle fiber contraction
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Sarcomere Structure
Z - lineZ - lineA- bandA- band
= dArk band= dArk bandI - bandI - band
= LIght band= LIght band
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Thin Filament: ActinThin Filament: ActinF-actinG-actin
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Thick Filament: MyosinThick Filament: Myosin
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Some Myoblasts do not fuse satelite cells in endomysium
regeneration of muscle
Development of Myofibers from
MyoblastsMyoblasts
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Motor UnitsMotor Units
= All muscle fibers that are controlled by a single motor neuron
The lower the ratio of muscle fibers to neurons, the more precise the movement can be!
Few cases 1: 1 relationship. Where?
Most cases: many muscle fibers (up to 2,000) : 1 motor neuron. Where?
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Muscle ControlMuscle tone = Resting tension of skeletal muscles
(continuous contraction of some motor units to maintain some muscle tension)
Recruitment or Multiple motor unit summation
Maximal tension production: ?
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Muscle Hypertrophy vs. Atrophy
Hypertrophy due to anaerobic exercise
Leads to increased muscle size - how?
Atrophy if supply of myofilaments exceeds demand. Muscle fibers become smaller and weaker.
Eventual death of muscle fibers is irreversible! Importance of Physical Therapy
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Three Types of Muscle FibersThree Types of Muscle Fibers
1) Fast (1) Fast (or Whiteor White) Fibers) FibersFast contraction after nervous stimulation
Large diameterlarge glycogen reserve
few mitochondria
densely packed myofibrils
Fatigue fast due to mainly anaerobic respiration
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2) Slow (or Red) Fibers2) Slow (or Red) Fibers
Slower but continuous contraction for extended periods
Smaller diameter (~ half)contain myoglobin
more capillaries
more mitochondria
Do not fatigue as fast due to ? Fig 9-13
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3) Intermediate Fibers3) Intermediate Fibers
Have attributes inbetween fast and slow types
Most skeletal muscles contain mixture of fiber types. Proportion of fast to slow depends on ___________?
One motor unit only contains one fiber type
Eye, hand: ____ fibers dominate
Back, calf: ____ fibers dominate
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Organization of Skeletal Muscle Fibers
Effect of individual muscle contraction
determined by:1. arrangement of muscle fibers2. way of attachment to skeletal system
Bundles of muscle fibers =
Muscle fibers within 1 fascicle are parallel
4 types of fascicle organizationwww.freelivedoctor.com
Parallel MuscelsParallel Muscels
Majority
Spindle shaped with cord-like tendons
Some flat bands with broad _____ on each end
Examples: ?
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Convergent muscelsConvergent muscels
Broad origin, pointed insertion
Direction of pull can be varied:versatility!!
Example
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Pennate Muscles: UnipennatePennate Muscles: UnipennateOne or more tendons run
though muscle body
Fascicles in oblique angle to tendon
Can generate more tension
Example
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Pennate Muscles: Pennate Muscles: Bipennate & Bipennate & Multipennate Multipennate
ExampleExample
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Circular Muscles Circular Muscles
= Sphincters
Concentric fibers adjust opening
Examples: orbicularis occuli and oris
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Muscle TerminologyMuscle Terminology
Origin stationary
Insertion moves
Possible: multiple origins
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Types of ActionsTypes of Actions
flexion, extension adduction, abduction elevation, depression rotation,
circumduction pronation, supination
etc. . . . .
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Grouping of Muscles according to Grouping of Muscles according to Primary ActionPrimary Action
Agonist = Prime Mover
Antagonist (action opposes agonist)
Synergists = Assistants of prime mover
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Anterior Thorax
Deltoid– IM injection site
Pectoralis– Major and minor
Serratus anterior
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The Arm, AnteriorAspect
•Biceps Brachii•Two Heads•Origin: Coracoid and Supraglenoid tubercle•Insertion: Radial Tubercle
•Brachialis•Brachioradialis•Digital Flexors
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The Arm, Posterior Aspect
•Triceps Brachii•Three Heads:
•Long•Lateral•Medial
•Carpal Extensors•Digital Extensors•Extensor retinaculum
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The Hand,Dorsal Aspect
•Extensor retinaculum
•Extensor tendons
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The Hand, Palmar Aspect
•Flexor Retinaculum AKA Transverse Carpal Ligament•Carpal Tunnel
•Irritates the median nerve
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The Pelvis
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The Thigh:Anterior View
•Quadriceps Group (4 heads) converge as the Quadriceps Tendon
•Vastus Lateralis•Vastus Medialis•Rectus Femoris•Vastus intermedius
•Iliotibial Tract•Sartorius
•Longest muscle in body
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