Muscle as an organ

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 4 tissue types.

> 700 skeletal muscles

Word roots:sarco mys

Overview of Muscle TissueOverview of Muscle Tissue

• Functions of muscle tissue

– Movement

– Maintenance of posture – enables the body to remain sitting or standing

– Joint stabilization

– Heat generation – muscle contractions produce heat

•Helps maintain normal body temperature

Types of Muscle TissueTypes of Muscle Tissue

• Three types • Skeletal muscle tissue – packaged into

skeletal muscles, Cells are striated, voluntary

•Makes up 40% of body weight

• Cardiac muscle tissue – occurs only in the walls of the heart, striated, involuntary

• Smooth muscle tissue – occupies the walls of hollow organs. Visceral, no striations, involuntary

Similarities of Muscle TissueSimilarities of Muscle Tissue

• Cells of skeletal and smooth muscles are known as fibers

• Muscle contraction depends on two types of myofilaments

• One type contains actin

• Another type contains myosin

•These two proteins generate contractile force

• Plasma membrane is called a sarcolemma

• Cytoplasm is called sarcoplasm

Basic Features of a Skeletal Muscle

• Connective tissue sheaths bind a skeletal muscle and its fibers together

•Epimysium –(overcoat) dense regular connective tissue surrounding entire muscle

•Perimysium – surrounds each fascicle (group of muscle fibers)

•Endomysium – a fine sheath of connective tissue wrapping each muscle cell

• Connective tissue sheaths are continuous with tendons

Gross AnatomyGross Anatomy

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

myofilaments

Epi-, Peri-, and Endomysium

Are interwoven - Go over into tendon

Distinguish between:TendonAponeurosisLigament

Basic Features of a Skeletal Muscle

• Muscle attachments

– Most skeletal muscles run from one bone to another

– One bone will move – other bone remains fixed

– Origin – immovable or less movable bone that muscle moves toward when a muscle contracts

– Insertion – Movable bone when a muscle contracts, moves towards origin

Muscle TerminologyMuscle Terminology

Origin stationary

Insertion moves

Possible: multiple origins

Basic Features of a Skeletal Muscle

• Muscle attachments • Muscles attach to origins and insertions

by connective tissue

•Direct (fleshy) attachments – connective tissue fibers are short, epimysium of muscle is fused to the periosteum of a bone of perichondrium of a cartilage

•Indirect attachments – connective tissue forms a tendon or aponeurosis

• Bone markings present where tendons meet bones

•Tubercles, trochanters, and crests

Arrangement of FasciclesArrangement of Fascicles

• Parallel/Fusiform-long axis of fascicles run parallel to long axis of the muscle

• Pennate – fascicles short and attach obliquely

• Convergent – has broad origin and fascicles converge toward a single tendon

• Circular-fascicles arranged in concentric rings

Parallel MusclesParallel Muscles

Majority

Spindle shaped with cord-like tendons

Convergent musclesConvergent muscles

Broad origin, pointed insertion

Pennate Muscles: UnipennatePennate Muscles: Unipennate

One or more tendons run though muscle body

Fascicles in oblique angle to tendon

Can generate more tension

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

Examples

Circular Muscles Circular Muscles

= Sphincters

Concentric fibers adjust opening

Examples: orbicularis occuli and oris

Types of ActionsTypes of Actions

flexion, extension adduction, abduction elevation, depression rotation pronation, supination

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

Naming the Skeletal MusclesNaming the Skeletal Muscles

• Location –most often with regard to bone

• Shape– the deltoid is triangular

• Relative size - Maximus (largest), minimus (smallest), longus (long), and brevis (short), indicate size

• Direction of fascicles and muscle fibers -Name tells direction in which fibers run

– Example – rectus (straight) abdominis and transversus or oblique abdominis

• Location of attachments – name reveals point of origin and insertion. Origin always named first! Example – brachioradialis,

Naming the Skeletal MusclesNaming the Skeletal Muscles

• Number of origins – two, three, or four origins

– Indicated by the words biceps, triceps, and quadriceps

• Action – the action is part of the muscle’s name

•Flexor, extensor, adductor, or abductor