Download Chapter 6: Muscular System

Chapter 6:
Muscular System
Anatomy & Physiology
Kasprowicz
The essential function of
muscle is contraction –
making it responsible for
almost all body movement.
Types of Muscle
1) Skeletal
2) Cardiac
3) Smooth
Types of Muscle
• muscle cells are elongated =
muscle fibers (smooth, skeletal)
• contain myofilaments (ability
to contract)
• terminology:
myo-, mys- = muscle
sarco- = flesh
General Muscle Characteristics
1)
2)
3)
4)
Very large, multinucleated cells
Striated (visible stripes or banding
pattern)
Voluntary (conscious) control; can
be reflexive too
muscle fibers (cells) are bundled
together by strong connective
tissues 
exert great force, but tire easily
Skeletal Muscle
Deep fascia
Connective Tissues in Skeletal Muscle

Endomysium – around single
muscle fiber

Perimysium – around a fascicle
(bundle) of fibers

Epimysium – covers the entire
skeletal muscle

Deep Fascia – on the outside of the
epimysium
Connective Tissues in Skeletal Muscles
Connective Tissues in Skeletal Muscle

tendon – dense connective tissue
attaching muscle to bone (cord-like)

aponeuroses – attach muscles
indirectly to bone,cartilages or
connective tissue coverings (sheetlike)

Epimysium blends into a connective
tissue attachment
Connective Tissues in Skeletal Muscles
Connective Tissues in Skeletal Muscles
Aponeurosis of the
external oblique
Connective Tissues in Skeletal Muscles
Refer to
pg. 272 in
your
textbook
Connective Tissues in Skeletal Muscles
Spindle-shaped cells with one
nucleus
2) no striations
3) Involuntary (no conscious
control)
4) Found in hollow visceral organs
5) Have small amount of
endomysium
1)
Smooth Muscle
6)
7)
slow, sustained, tireless
movement
often layers in
opposite
directions
Smooth Muscle
Smooth Muscle: Stomach Wall
Branching cells with one nucleus
connected by intercalated discs
2) Striated
3) Involuntary (no conscious
control)
4) small amounts of endomysium
1)
Cardiac Muscle
5)
Cardiac fibers
are arranged in
spiral or 8shaped bundles
Cardiac Muscle
1)
Producing movement
2)
Maintaining posture
3)
Stabilizing joints
4)
Support soft tissues
5)
Generating heat
6)
Guard entrances and exits
Muscle Functions
Muscle Functions
Skeletal Muscle Fiber (Cell) Formation
Skeletal Muscle Fiber (Cell) Formation

Cells are multinucleate

Nuclei are just beneath the sarcolemma
(1) sarcolemma - specialized plasma
membrane of muscle cells
Microscopic Anatomy of Muscle
(2) Cytoplasm filled with myofibrils
myofibrils – perfectly aligned, ribbonlike organelles; give muscle
fiber its striped appearance
Microscopic Anatomy of Muscle
(2) Cytoplasm filled with myofibrils
A closer look at the myofibril
Light (I) bands
Dark (A) bands
Microscopic Anatomy of Muscle
(2) Cytoplasm filled with myofibrils
Banding Pattern:
Light (I) bands contain the Z disc
Dark (A) bands contain the H zone
M line - holds
adjacent
filaments
together;
center of
H zone
Microscopic Anatomy of Muscle
An even closer look at the myofibril…
(3) Sarcomere
- contractile unit of the myofibril
- Z disc to Z disc
Microscopic Anatomy of Muscle
An even closer look at the myofibril…
(3) Sarcomere
Microscopic Anatomy of Muscle
Zooming in on the sarcomere…
(4) Myofilaments - special proteins
that cause muscle to contract
Two Types:
a) myosin (thick filament)
b) actin
(thin filament)
Microscopic Anatomy of Muscle
Two Types:
a) myosin (thick filament)
 protein with heads that form
cross bridges b/t thick & thin
filaments during muscle
contraction

Contain ATPase enzymes
Microscopic Anatomy of Muscle
Two Types:
b) actin (thin filament)

Made of the contractile protein actin
& some other regulatory proteins
Microscopic Anatomy of Muscle
Zooming in around the H zone….
Microscopic Anatomy of Muscle
(5) Sarcoplasmic reticulum (SR)
specialized smooth ER surrounding
each myofibril
stores calcium which is released
when muscle is stimulated to
contract
Microscopic Anatomy of Muscle
Sarcoplasmic reticulum (SR)
Microscopic Anatomy of Muscle
Sarcoplasmic reticulum (SR)
Microscopic Anatomy of Muscle
Microscopic Organization of Muscle:
Level 1 (refer to Fig. 10-6, pg. 278)
Let’s put this all together….
Microscopic Organization of Muscle:
Level 2
Let’s put this all together….
Microscopic Organization of Muscle:
Level 3
Let’s put this all together….
Microscopic Organization of Muscle:
Level 4
Let’s put this all together….
Microscopic Organization of Muscle:
Level 5
Let’s put this all together….
Skeletal Muscle Activity:
Initiating the Contraction
 Irritability – ability to receive and
respond to a stimulus
(a property shared with neurons)
 Contractility – ability to shorten
when an adequate stimulus is
received
Special Functional Properties of Muscle
Skeletal muscles must be
stimulated by a nerve to
contract (motor neuron).
Quick Review of Neurons & Synapses
Quick Review of Neurons & Synapses
Quick Review of Neurons & Synapses
Motor unit:
One neuron & the muscle cells stimulated
by that neuron
Nerve Stimulus to Muscle
Neuromuscular junctions

the neuron & muscle fibers do NOT touch

separated by a gap
called the synaptic
cleft which is filled
w/ interstitial fluid
Nerve Stimulus to Muscle
Neuromuscular junctions
Nerve Stimulus to Muscle
Neurotransmitters
 chemical
released by neurons used to
“carry” the impulse across the
synaptic cleft
Acetylcholine (ACh) is the
neurotransmitter used at the
neuromuscular junction of skeletal
muscle
Transmission of Nerve Impulse to Muscle
Steps in Impulse Transmission

ACh is released by the pre-synaptic
axon terminal of the motor neuron

ACh crosses the synaptic cleft &
attaches to receptors on the
sarcolemma

Sarcolemma becomes permeable to
sodium (Na+)
Transmission of Nerve Impulse to Muscle
Steps in Impulse Transmission
 Sodium floods into the cell generating an
action potential (electrical current)
 Once started, muscle contraction
cannot be stopped !!
 ACh is broken down by the enzyme
acetylcholinesterase
This prevents continued contraction of
the muscle cell in the absence of
additional nerve impulses.
Transmission of Nerve Impulse to Muscle
Steps in Impulse Transmission

When an action potential
sweeps along the sarcolemma
and a muscle cell is excited,
calcium ions are released from
the sarcoplasmic reticulum
Transmission of Nerve Impulse to Muscle
Steps in Impulse Transmission

The flood of Ca+ ions is the final
trigger for the contraction of the
muscle
Transmission of Nerve Impulse to Muscle
Skeletal Muscle Activity:
Sliding Filament Theory
of Muscle Contraction
Sliding Filament
Theory: Overview
 Myosin heads form
cross bridges with
binding sites on
actin
 Myosin heads detach &
then bind to the next
site on actin
Resting Sarcomere
Sarcomere Contracts
Mechanism of Muscle Contraction
Sliding Filament
Theory: Overview

This action continues,
causing the myosin &
actin to slide past
each other
Resting Sarcomere
Sarcomere Contracts
Mechanism of Muscle Contraction
Sliding Filament
Theory: Overview

Collective shortening of
Resting Sarcomere
the muscle cell
sarcomeres =
muscle contraction
Sarcomere Contracts
Mechanism of Muscle Contraction
Step 1:
 Ca+ ions released from the SR
attach to the troponintropomyosin complex

Binding sites on the actin
filament are exposed
The Contraction Cycle : The Nitty Gritty
Step 1:
The Contraction Cycle : The Nitty Gritty
Step 2:
 myosin heads attach to actin binding
sites, forming cross bridges

ATP was required to prep the
myosin head (ATP  ADP + P)
The Contraction Cycle : The Nitty Gritty
Step 2:
The Contraction Cycle : The Nitty Gritty
Step 3:
 ADP + P released from myosin
head

myosin head flexes/pivots =
“power stroke”
The Contraction Cycle : The Nitty Gritty
Step 3:
The Contraction Cycle : The Nitty Gritty
Step 4:

ATP binds to myosin head,
causing it to
detach from
the actin
filament
The Contraction Cycle : The Nitty Gritty
Step 5:
 myosin head re-energized
(ATP  ADP + P)
Step 6:
 Ca+ ions pumped back into the SR
 troponin-tropomyosin complex
moves back to its original position
The Contraction Cycle : The Nitty Gritty
The Contraction Cycle : The Nitty Gritty
The Contraction Cycle : The Nitty Gritty
Muscle Contraction Animations
http://www.mhhe.com/biosci/bio_animations/09_MH_MuscleContraction_Web/index.html
Muscle Contraction 3-D Animation
http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__action_potentials_and_muscle_contraction.html
Action Potentials & Muscle Contraction
https://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter10/animation__breakdown_of_atp_and_crossbridge_movement_during_muscle_contraction.html
Break Down of ATP & Cross Bridge Attachment
https://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter10/animation__sarcomere_contraction.html
Sarcomere Contraction

The “all-or-none” response of muscle
contraction refers to the muscle cell,
NOT the whole muscle

Whole muscle reacts with a graded
response (different degrees of
shortening)
Contraction of the Whole Muscle
Graded responses are produced in 2 ways:
1)
Change the frequency of stimulation
2)
Change the # of muscle cells
stimulated/time
- more activated muscle cells
stronger FORCE of contraction
Contraction of the Whole Muscle
Changing Stimulation Frequency
1
Muscle Twitch – 1 stimulus;
single, brief, jerky contraction
Contraction of the Whole Muscle
Changing Stimulation Frequency
2
Wave Summation– frequency of
stimulus increases; less time to relax;
contraction strength “summed”
Contraction of the Whole Muscle
Changing Stimulation Frequency
3
Incomplete Tetanus – frequency
of stimulation increases even more
Contraction of the Whole Muscle
Changing Stimulation Frequency
4
Tetanus – frequency of stimulation
very rapid; no evidence of relaxation;
smooth, sustained contraction
Contraction of the Whole Muscle

Initially, muscles used stored ATP for
energy
 ATP is hydrolyzed into ADP + P
 Only 4-6 seconds worth of ATP is stored
by muscles

After this, other metabolic pathways
must be used to produce ATP
Energy for Muscle Contraction
Pathway 1: Direct Phosphorylation
 Muscle
cells contain creatine
phosphate (CP)
 CP is a high-energy molecule that
transfers energy to ADP, regenerating
ATP
 CP
supplies are exhausted in about
20 seconds
Energy for Muscle Contraction
Pathway 1:
Direct
Phosphorylation
Energy for Muscle Contraction
Pathway 2: Anaerobic Respiration
(a.k.a. lactic acid fermentation)
 breaks
down glucose without oxygen
 Glucose
is broken down to pyruvic
acid; 2 ATP are produced
 Pyruvic
acid  lactic acid
Energy for Muscle Contraction
Pathway 2:
Anaerobic Respiration
(lactic acid fermentation)
Energy for Muscle Contraction
Pathway 2: Anaerobic Respiration
 This reaction is not as efficient,
but it is fast
 Huge amounts of glucose are needed
 Lactic acid produces muscle fatigue

Duration: 30-60 seconds
Energy for Muscle Contraction
Pathway 3: Aerobic Respiration
 Series
of metabolic pathways that occur
in the mitochondria & require oxygen
 Glucose
is broken down to carbon
dioxide and water releasing energy
 This
is a slower reaction that requires
continuous oxygen
 High
energy pay-off: 36 ATP
Energy for Muscle Contraction
Pathway 3:
Aerobic Respiration
Energy for Muscle Contraction

When a muscle is fatigued, it is unable to
contract

The common reason for muscle fatigue is
oxygen debt
 Oxygen must be “repaid” to tissue to
remove oxygen debt
 Oxygen is required to get rid of
accumulated lactic acid

Increasing acidity (from lactic acid) and
lack of ATP causes the muscle to contract
less
Muscle Fatigue & Oxygen Debt
Isotonic Muscle Contraction
 The myofilaments slide past
each other  muscle shortens
 movement occurs
Examples: bending knee,
rotating the arms,
smiling
Types of Muscle Contraction
Isometric Muscle Contraction
 muscle is not able to shorten

muscle tension keeps increasing
Examples:
lifting a 1000 lb. object alone;
pushing against an object that
doesn‘t move
Types of Muscle Contraction
 state
of continuous partial
contractions
 Different fibers contract at different times to
provide muscle tone
 muscle
remains firm, healthy & ready
for action
 Increasing
muscle tone increases
metabolic energy used, even at rest
Muscle Tone
Muscle Tone
If the nerve supply to a muscle is
destroyed, the muscle is no
longer stimulated in this manner,
and it loses tone and becomes
paralyzed. Soon after, it becomes
flaccid (soft and flabby) and
begins to atrophy (waste away).
Muscle Tone
Muscle Tone
“use it or lose it”
Aerobic (Endurance) Exercise

Examples: jogging, biking, swimming

stronger, more flexible muscles w/
greater resistance to fatigue
Effects of Exercise
Aerobic (Endurance) Exercise

Physiological Effects
1) increased blood supply to muscles
2) more mitochondria
3) increased metabolism
4) keeps bones strong
5) improves neuromuscular coordination
Effects of Exercise
“use it or lose it”
Resistance (Isometric) Exercise

Examples: weight training

increased muscle
size and strength
Effects of Exercise
Aerobic (Endurance) Exercise

Physiological Effects
1) increased # of myofilaments 
increased size of muscle fibers
2) more connective tissue
3) keeps bone strong
Effects of Exercise
1)
All (almost ) skeletal muscle cross a
least one joint
2)
Most of a skeletal muscle lies proximal
to the joint crossed
3)
All skeletal muscles have at least 2
attachments: the origin and the insertion
4)
Skeletal muscles can only PULL (create
tension)
5)
When a muscle contracts, the insertion
moves toward the origin
“Golden Rules” of Skeletal Muscle Activity

Movement occurs when a muscle
contracts and moves an attached bone

Muscles are attached to at least two
points
 Origin – attachment to a immoveable bone
 Insertion – attachment to an movable bone
Types of Body Movements
When a
skeletal muscle
contracts, its
insertion
moves toward
its origin
Types of Body Movements
 prime mover – muscle primarily
responsible for a certain movement
Example: biceps, hamstrings
(a.k.a. agonist)
 Antagonist – muscle that opposes
or reverses a prime mover
 Triceps when biceps flexes; quads
when hamstrings flex
Body Movements: Muscle Interactions
Prime Mover – biceps
Antagonist – triceps
Prime Mover – triceps
Antagonist – biceps
 Synergist – muscle that aids a
prime mover in a movement and
helps prevent rotation
Example: finger flexor muscles
brachioradiulus & brachialis in
the forelimb
Body Movements: Muscle Interactions
1) Flexion
decreases angle of joint, bringing
2 bones closer together
common in hinge, ball & socket joints
2) Extension
increases the angle of a joint,
moving the bones apart
hyperextension >180° angle
Types of Body Movements
Hyperextension
Flexion & Extension
Flexion & Extension
3) Rotation
movement of a bone around its
longitudinal axis
common in ball & socket joints
atlas (C1) around the axis (C2)
Types of Body Movements
Rotation
4) Abduction
movement of a limb away from the
medial plane
also used to refer to fanning of finger or toes
5) Adduction
movement of a limb toward the
midline
Types of Body Movements
Abduction & Adduction
Abduction & Adduction
6) Circumduction
proximal end is stationary; distal
end moves in a circle
limb moves in a cone shape
common in ball & socket joint
combo of flexion, extension, abduction &
adduction
Types of Body Movements
Circumduction
1) Dorsiflexion (point toes up
towards shin) & Plantar
Flexion (pointing the toes)
Special Body Movements
2) Inversion (turn sole of foot
medially) & Eversion (turn sole
of foot laterally)
Special Body Movements
3) Supination & Pronation
movements of the radius around
the ulna
supination: palm forward; radius &
ulna are parallel (anatomical
position); thumb lateral
pronation: palm facing back;
radius crosses ulna; thumb medial
Special Body Movements
3) Supination & Pronation
Special Body Movements
4) Opposition
movement of thumb across palm
to touch fingertips
Special Body Movements
Elevation & Depression
Protraction &
Retraction
1) Direction of muscle fibers
in reference to an imaginary line
(midline of body, long axis of limb)
ie. Rectus (fibers parallel to line)
Oblique (fibers at a slant to line)
Naming Skeletal Muscles
2) Relative Size
Longus = long
Longissimus = longest
Teres = long and round
Brevis = short
Magnus = large
Major = larger
Maximus = largest
Minor = small
Minimus = smallest
Naming Skeletal Muscles
3) Location of the Muscle
in reference to the associated bone
ie. temporalis (temporal bone)
frontalis (frontal bone)
Naming Skeletal Muscles
4) Number of origins
ie. biceps, triceps, quadriceps
5) Location of the muscle’s origin
and insertion
ie. Sternocleidomastoid muscle
Naming Skeletal Muscles
6) Shape of the muscle
ie. Deltoid (triangular)
7) Action of the muscle
ie.
adductor muscle, extensor muscle
Naming Skeletal Muscles
Head & Neck Muscles
Facial Muscles
• Frontalis
raises eyebrows and wrinkles the
forehead
• Orbicularis Oculi
close, squint, blink and wink the eyes
• Orbicularis Oris
closes the mouth and protrudes the lips;
the “kissing” muscle
Head and Neck Muscles
• Buccinator
flattens the cheek (whistling or playing
a trumpet); also a chewing muscle
• Zygomaticus
“smiling” muscle; raises the corners of
the mouth upward
Head and Neck Muscles
Chewing Muscles
• Buccinator
• Masseter
closes the jaw by elevating the mandible
(prime mover)
• Temporalis
helps masseter close the jaw (synergist)
Head and Neck Muscles
Frontalis
Temporalis
Orbicularis oculi
Zygomaticus
Orbicularis
oris
Buccinator
Masseter
Temporalis
Frontalis
Orbicularis oculi
Orbicularis oris
Masseter
Zygomaticus
Buccinator
Frontalis
Temporalis
Orbicularis
oculi
Zygomaticus
Buccinator
Orbicularis oris
Masseter
Neck Muscles
• Platysma
pulls down corners of the mouth,
downward sag of the mouth
• Sternocleidomastoid
two-headed muscle;
flex your neck (bowing of head); tilt
head to side
Head and Neck Muscles
Frontalis
Temporalis
Orbicularis oculi
Zygomaticus
Orbicularis
oris
Masseter
Buccinator
Platysma
Sternocleidomastoid
Frontalis
Temporalis
Orbicularis oculi
Orbicularis oris
Masseter
Zygomaticus
Buccinator
Sternocleidomastoid
Plastysma
Frontalis
Temporalis
Orbicularis
oculi
Zygomaticus
Buccinator
Orbicularis oris
Sternocleidomastoid
Masseter
platysma
Trunk Muscles
• move the vertebral column (mostly
posterior, anti-gravity muscles)
• anterior thorax muscles (move ribs,
head & arms)
• muscles of the abdominal wall (help
move vertebral column & form the
“girdle” holding internal organs in place)
Trunk Muscles
Anterior Muscles: Thorax
• Pectoralis Major
- fan-shaped muscle
- origin: sternum, pectoral girdle, ribs
- insertion: humerus
- adduct & flex the arm
Trunk Muscles
Pectoralis
major
Pectoralis
minor
Anterior Muscles: Thorax
• Intercostal Muscles
- deep muscles between the ribs
- aid in breathing
(external – inhale, internal – forcible
exhale)
Trunk Muscles
Internal
intercostals
External
intercostals
Anterior Muscles: Abdominal Girdle
• Rectus abdominus
- pubis to rib cage
- flex the vertebral column
- compression of abdominal contents
Trunk Muscles
Anterior Muscles: Abdominal Girdle
• External Oblique
- lateral walls of abdomen
- origin: ribs
insertion: illium
- flex the vertebral column, rotate/bend
trunk
Trunk Muscles
Anterior Muscles: Abdominal Girdle
• Internal Oblique
- origin: iliac crest insertion: ribs
- function same as external oblique
• Transversus abdominis
- deepest muscle in abdomen
- fibers run horizontally
- compresses the abdominal contents
Trunk Muscles
Posterior Muscles
• Trapezius
- kite-shaped muscle
- origin: occipital bone to last thoracic
vertebrae
insertion: scapula & clavicle
- head extension & movement of
scapula
Trunk Muscles
Posterior Muscles
• Latissimus Dorsi
- 2 large, flat muscles in the lower
back
- origin: lower spine & ilium
insertion: proximal end of humerus
- arm extension & adduction
(“power stroke”)
Trunk Muscles
Posterior Muscles
• Erector Spinae
- prime mover of back extension
(keep your body “erect”); control
bending at the waist
- paired; deep in the back
- span vertebral column
Trunk Muscles
Posterior Muscles
• Qudratus lumborum
- posterior abdominal wall
- flex spine laterally, extend vertebral
column
- origin: iliac crest
insertion: upper lumbar vertebrae
Trunk Muscles
Posterior Muscles
• Deltoids
- triangular muscle forming shoulder
- origin: spine of scapula to clavicle
insertion: proximal humerus
- prime mover of arm abduction
Trunk Muscles
• The anterior arm muscles cause elbow
flexion
strongest: brachialis
biceps brachii
“weakest”: brachioradialis
• posterior arm: triceps brachii
Muscles of the Upper Limb
Anterior Arm Muscles
• Biceps brachii
- origin: 2 heads in pectoral girdle
insertion: radius
- prime mover of forearm flexion &
supination
Muscles of the Upper Limb
Anterior Arm Muscles
• Brachialis
- origin: humerus
- forearm flexion
insertion: ulna
• Brachioradialis
- origin: humerus
insertion: distal forearm
Muscles of the Upper Limb
Posterior Arm Muscles
• Triceps brachii
- origin: 3 heads in pectoral girdle
insertion: olecranon process of ulna
- prime mover of elbow extension
- biceps brachii antagonist
Muscles of the Upper Limb
• cause movement of hip, knee &
foot joints
• some of the largest, strongest
muscles in the body
• specialized for walking & balance
• many of the muscles cross 2 joints
and can cause movement at both
Muscles of the Lower Limb
Muscles that Move the Hip Joint
• Gluteus Maximus
- forms most of the flesh of the buttock
- origin: sacrum & illiac
insertion: femur & iliotibial tract
- hip extensor (important when
climbing and jumping)
Muscles of the Lower Limb
Muscles that Move the Hip Joint
• Gluteus Medius
- beneath gluteus maximus
- hip abductor; steadies pelvis when
walking
• Iliopsoas (two, fused muscles)
- prime mover of hip flexion; keeps
upper body from falling backward
when standing
Muscles of the Lower Limb
Muscles that Move the Hip Joint
• Adductor Muscles
- group of muscles; medial thigh
- adduct, or press, thighs together
- origin: pelvis
insertion: femur
- tend to get flabby
Muscles of the Lower Limb
Iliopsoas
Adductor muscles
Anterior
View
Gluteus medius
Gluteus maximus
Adductor magnus
Iliotibial tract
Posterior
View
Muscles that Move the Knee Joint
• Hamstring Group
- group of muscles; posterior thigh
- biceps femoris, semimembranosus,
semitendinosus
- origin: ischium
insertion: tibia
- prime movers of thigh extension &
knee flexion
Muscles of the Lower Limb
Muscles that Move the Knee Joint
• Sartorius
- thin, strap-like, relatively weak flexor
- most superficial thigh muscle
- synergist in sitting
“criss cross
applesauce”
Muscles of the Lower Limb
Muscles that Move the Knee Joint
• Quadriceps Group
- group of muscles; anterior thigh
- rectus femoris & 3 vastus muscles
- origin: pelvis & thigh
insertion: tibia via patellar ligament
- prime movers of knee extension; hip
flexion
Muscles of the Lower Limb
Iliopsoas
Q
U
A
D
S
Sartorius
Iliopsoa
Rectus femoris s
Adductor muscles
Vastus lateralis
Vastus medialis
Anterior
View
Posterior
View
Muscles that Move the Ankle & Foot
• Tibialis Anterior
- superficial muscle of anterior leg (shin)
- origin: tibia
insertion: tarsals
- dorsiflex & invert the foot
• Fibularis Muscles
- plantar flexion and eversion
- origin: fibula
insertion: metatarsals
Muscles of the Lower Limb
Muscles that Move the Ankle & Foot
• Gastrocnemius
- forms curved calf; 2 parts
- origin: femur
insertion: heel using Achille’s tendon
- prime mover of plantar flexion
Muscles of the Lower Limb
Muscles that Move the Ankle & Foot
• Soleus
- deep to gastrocnemius
- origin: tibia & fibula (no effect on knee)
insertion: heel using Achille’s tendon
- plantar flexion
Muscles of the Lower Limb
Posterior
View
Anterior
View