Skeletal Muscle Tissue And Organization

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:

www.freelivedoctor.com

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


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


Gross AnatomyGross Anatomy

Each skeletal muscle is wrapped by 3 concentric layers of connective tissue.


Epi-, Peri-, and Endomysium

Are interwoven - Go over into tendon

Distinguish between:TendonAponeurosisLigament

Function: ProtectionBlood supplyInnervation


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


http://www.mdausa.org/images/p73_anes_2myas.gif

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


http://images.google.com/imgres?imgurl=www.finchcms.edu/anatomy/histology/histology/muscle/images/h_m_13compare.jpg&imgrefurl=http://www.finchcms.edu/anatomy/histology/histology/muscle/h_m_13desc.html&h=331&w=411&prev=/images%3Fq%3Dmyofiber%2Bcross%2Bsect

Myofiber Myofiber (( 100µm) 100µm) Myofibrils Myofibrils (( 1-2 µm) 1-2 µm) MyofilamentsMyofilaments

Actin & MyosinActin & Myosin

Myofilaments


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


Sarcomere Structure

Z - lineZ - lineA- bandA- band

= dArk band= dArk bandI - bandI - band

= LIght band= LIght band


Thin Filament: ActinThin Filament: ActinF-actinG-actin


Thick Filament: MyosinThick Filament: Myosin


Some Myoblasts do not fuse satelite cells in endomysium

regeneration of muscle

Development of Myofibers from

MyoblastsMyoblasts


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?


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: ?


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


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


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


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


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: ?


Convergent muscelsConvergent muscels

Broad origin, pointed insertion

Direction of pull can be varied:versatility!!

Example


Pennate Muscles: UnipennatePennate Muscles: UnipennateOne or more tendons run

though muscle body

Fascicles in oblique angle to tendon

Can generate more tension

Example


Pennate Muscles: Pennate Muscles: Bipennate & Bipennate & Multipennate Multipennate

ExampleExample


Circular Muscles Circular Muscles

= Sphincters

Concentric fibers adjust opening

Examples: orbicularis occuli and oris


Muscle TerminologyMuscle Terminology

Origin stationary

Insertion moves

Possible: multiple origins


Types of ActionsTypes of Actions

flexion, extension adduction, abduction elevation, depression rotation,

circumduction pronation, supination

etc. . . . .


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


Anterior Thorax

Deltoid– IM injection site

Pectoralis– Major and minor

Serratus anterior


The Arm, AnteriorAspect

•Biceps Brachii•Two Heads•Origin: Coracoid and Supraglenoid tubercle•Insertion: Radial Tubercle

•Brachialis•Brachioradialis•Digital Flexors


The Arm, Posterior Aspect

•Triceps Brachii•Three Heads:

•Long•Lateral•Medial

•Carpal Extensors•Digital Extensors•Extensor retinaculum


The Hand,Dorsal Aspect

•Extensor retinaculum

•Extensor tendons


The Hand, Palmar Aspect

•Flexor Retinaculum AKA Transverse Carpal Ligament•Carpal Tunnel

•Irritates the median nerve


The Pelvis


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


Business

Skeletal Muscle Tissue And Organization