Muscle as an organ
Muscle tissue vs. Muscle as an
organ
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 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 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 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 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:
Tendon
Aponeurosis
Ligament
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 Terminology
Origin
Insertion
stationary
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 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 Muscles
Majority
Spindle shaped with
cord-like tendons
Convergent muscles
Broad origin,
pointed
insertion
Pennate Muscles: Unipennate
One or more tendons
run though muscle
body
Fascicles in oblique
angle to tendon
Can generate more
tension
Pennate Muscles:
Bipennate &
Multipennate
Examples
Circular Muscles
= Sphincters
Concentric fibers
adjust opening
Examples: orbicularis
occuli and oris
Types of Actions
 flexion, extension
 adduction, abduction
 elevation, depression
 rotation
 pronation, supination
Grouping of Muscles according to
Primary Action
Agonist = Prime Mover
Antagonist (action opposes agonist)
Synergists = Assistants of prime mover
Naming 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 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