Download muscle fiber

Skeletal Muscles
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Attach to bones
Produce skeletal movement (voluntary)
Maintain posture
Support soft tissues
Regulate entrances to the body
Maintain body temperature
Properties of Skeletal Muscles
Electrical excitability
-ability to respond to stimuli by producing action potentials
-two types of stimuli: 1. autorhythmic electrical signals
2. chemical stimuli – e.g. neurotransmitters
Contractility
-ability to contract when stimulated by an action potential
-isotonic contraction: tension develops, muscle shortens
-isometric contraction: tension develops, length doesn’t change
Extensibility
-ability to stretch without being damaged
-allows contraction even when stretched
Elasticity
-ability to return to its original length and shape
Muscles: Gross Anatomy
•muscles with similar functions are grouped and held
together by layers of deep fascia
e.g. biceps femoris and brachialis – forearm
flexion
• three layers of connective tissue surround a muscle
– Epimysium – divides a muscle into fasicles
– Perimysium – divides a fasicle into muscle fibers
– Endomysium – divides a muscle fiber into myofibrils
Gross Anatomy
•muscles are surrounded by a fascia (areolar tissue)
•remove the fascia – epimysium that surrounds the
muscle and divides it into groups called fascicles
• each individual fascicle is surrounded by a
perimysium
•perimysium divides the fascicle into muscle fibers
• muscle fiber = individual muscle cell
•each muscle fiber/muscle cell is surrounded by an
endomysium
•endomysium divides the muscle fiber into protein
filaments = myofibrils
•myofibrils contain a “skeleton” of protein
filaments (myofilaments) organized as sarcomeres
Muscles: Gross Anatomy
• epimysium and perimysium extend off the muscle to become
organized as a tendon – attaches to the periosteum of the bone
Microanatomy of Skeletal Muscle
Fibers
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large, multinucleated cells called fibers
mature muscle fibers range from 10 to 100 microns in diameter
typical length is 4 inches - some are 12 inches long
muscle fibers increase in size during childhood = human GH & testosterone
testosterone also increases muscle size
• embryonic development – stem cells (satellite cells) differentiate into immature
myoblasts which begin to make the proteins of the myofibrils (i.e. the
myofilaments)
– myoblasts mature into myocytes
– multiple myocytes fuse to form the muscle cell (muscle fiber)
– muscle fibers cannot divide through mitosis
– number of muscle cells predetermined before birth – they get larger as we
grow
– satellite cells can repair damaged/dying skeletal muscle cells throughout
adulthood
Muscle Cell Anatomy
• new terminology
• cell membrane = sarcolemma
• cytoplasm = sarcoplasm
– large amounts of glycogen and
myoglobin
– surrounds the myofibrils
• myofibrils made up of myofilaments
– actin & myosin
• transverse tubules
– ingrowths of the sarcolemma
– carry the action potential deep into
the fiber
– flanks the sarcoplasmic reticulum
• novel internal membrane system =
sarcoplasmic reticulum
– for calcium storage
The Proteins of Muscle
• contractile elements of the myofibrils = myofilaments
-2 microns in diameter
-give the muscle its striated appearance
• myofilaments are built of 3 kinds of protein
– contractile proteins
• myosin and actin
– regulatory proteins which turn contraction on & off
• troponin and tropomyosin
– structural proteins which provide proper alignment, elasticity and extensibility
• titin, myomesin, nebulin, actinin and dystrophin
• two kinds of myofilaments
• Thin - actin, troponin and tropomyosin
• Thick – myosin only
M line
Sarcomere
Structure
• myosin/thick filament only region = H zone
• thin filament only region = I band
• length of myosin/thick filaments = A band
• contraction = “sliding filament theory”
• thick and thin myofilaments slide over each other and sarcomere
shortens
Sarcomere
Structure
• sarcomere = regions of myosin (thick myofilament) and actin (part of thin
myofilament)
• bounded by two Z lines
• thin filaments project out from Z line – actin attached via actinin (structural
protein)
• myosin/thick filaments lie in center of sarcomere - overlap with thin filaments
and connect to them via cross-bridges
• myosin/thick filaments are held in place at the M line at the center and by titin
at the Z-line
Contraction: The Sliding Filament Theory
•Actin proteins in the thin
filament have myosin
binding sites
•these sites are “covered
up” by troponin and
tropomyosin in relaxed
muscle
•removal of
troponin/tropomyosin
from these sites is
required for contraction
•removal of
troponin/tropomyosin is
done through binding of
calcium to troponin
•calcium is released from
the sarcoplasmic reticulum
upon the action potential
Contraction: The Sliding Filament Theory
• myosin/thick myofilament
is a bundle of myosin
molecules
• myosin looks like a “golf
club” with a head, a hinge
region and a shaft
• each myosin protein has a
globular “head” with a site
to bind and breakdown
ATP (ATPase site) and to
bind actin (actin binding
site)
• binding of actin and myosin
binding sites = crossbridging
RESETTING of
system
Increase in Cai
Removal of troponin-tropomyosin
CONTRACTION
Sliding of actin along myosin
-for cross bridging- you will need two things:
1. calcium – uncovers the myosin binding sites on actin – “pushes aside” the troponintropomyosin complex
2. myosin head bound to ADP
-for contraction – i.e. pivoting of the myosin head into the M line – the myosin head must be
empty
-to “reset” for a new cycle of cross-bridging – the myosin head must detach and pivot back -the
myosin head must bind ATP
-once the myosin head pivots back – the ATP is broken down to ADP – head is ready to
cross-bridge again – if actin is “ready”
Contracted Sarcomere
• http://highered.mcgrawhill.com/sites/0072495855/student_view0/chapter10/animation__myofilam
ent_contraction.html
• http://www.youtube.com/watch?v=EdHzKYDxrKc
• https://www.youtube.com/watch?v=4201SrN0WlY
• https://www.youtube.com/watch?v=Ct8AbZn_A8A
The Neuromuscular Junction
• the motor neuron’s synaptic terminal is
in very close association with the muscle
fiber
• distance between the bulb and the folded
sarcolemma = neuromuscular junction
•neurotransmitter released = acetylcholine
https://www.youtube.co
m/watch?v=7wM5_aUn2
qs
The “Big Picture”
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AP generated at trigger zone in
pre-synaptic motor neuron
AP arrives in synaptic end bulb – causes entry
of calcium into end-bulb release of
of acetylcholine/Ach
Binding of Ach to ligand-gated Na
channels on muscle sarcolemma (i.e. Ach
receptors)
Na+ enters muscle cell = depolarization
Muscle membrane potential reaches
threshold  Action Potential
AP travels along sarcolemma into
T-tubules
AP “passes by” sarcoplasmic reticulum 
release of calcium into sarcoplasm
Ca binds troponin-tropomyosin complex &
“shifts” it off myosin binding site
Cross-bridging between actin and myosin,
pivoting of myosin head = Contraction
(ATP dependent)
Contraction vs. Relaxation
• Acetylcholinesterase (AchE) breaks down ACh
• calcium pumped back into sarcoplasmic reticulum
• Limits duration of contraction
Action Potentials in Nerve and Muscle
• Entire muscle cell membrane versus only the axon of the neuron
is involved
• Resting membrane potential
– nerve is -70mV
– skeletal & cardiac muscle is closer to -90mV
• Duration
– nerve impulse is 1/2 to 2 msec
– muscle action potential lasts 1-5 msec for skeletal & 10-300msec for
cardiac & smooth
• Fastest nerve conduction velocity is 18 times faster than velocity
over skeletal muscle fiber
Motor Units
• Each skeletal fiber has only ONE NMJ
• motor unit = somatic motor neuron +
all the skeletal muscle fibers it
innervates
• number and size of motor units indicate
precision of muscle control
• Motor units fire asynchronously
– some fibers are active others are relaxed
– delays muscle fatigue so contraction can
be sustained
• motor units are also intermingled
– the net distribution of force applied to
the tendon remains constant even when a
fraction of muscle fibers are relaxed
Muscle twitch
Single momentary contraction
unit
Response to a single stimulus
Muscle Metabolism
• Production of ATP:
-contraction requires huge amounts of ATP
-muscle fibers produce ATP three ways:
1. Creatine phosphate
2. Anaerobic metabolism
3. Aerobic metabolism
Creatine Phosphate
• Muscle fibers at rest produce more ATP then they need for resting metabolism
• Excess ATP within resting muscle used to form creatine phosphate
– creatine – arginine, glycine and methionine
• made by kidneys and liver
• phosphorylated by the enzyme creatine kinase
• takes a phosphate off of ATP and transfers it creatine
• takes the phosphate off of creatine phosphate and transfers it back to ADP –
to make ATP
• Creatine phosphate: 3-6 times more plentiful than ATP within muscle
• Sustains maximal contraction for 15 sec (used for 100 meter dash).
• Athletes often use creatine supplementation
– gain muscle mass but shut down bodies own synthesis (safety?)
Anaerobic Cellular Respiration
• Muscles deplete creatine – can make ATP
in anaerobically or aerobically
• Glycogen converted into glucose first
• ATP produced from the breakdown of
glucose into pyruvic acid (sugar) during
glycolysis
– if no O2 present (anaerobic) - pyruvic
converted to lactic acid which diffuses into
the blood
• Glycolysis can continue anaerobically to
provide ATP for 30 to 40 seconds of
maximal activity (200 meter race)
• If O2 is present the pyruvic acid is
converted into acetyl coA (aerobic)
Aerobic Cellular Respiration
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ATP for any activity lasting over 30 seconds
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if sufficient oxygen is available, pyruvic acid is converted into acteyl coA
Acetyl coA enters the mitochondria to enter the Kreb’s cycle
Kreb’s cycle generates NADH and FADH2 (electron carriers)
The electrons are carried to an enzymes located on the inner mitochondrial membrane
The electrons are then transported along three complexes of enzymes – ultimately transported to oxygen
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Provides 90% of ATP energy if activity lasts more than 10 minutes
Each glucose = 36 ATP
fatty acids and amino acids can also be used by the mitochondria
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This results in the synthesis of ATP, water and heat
Fatty acid = ~100 ATP
Sources of oxygen – diffusion from blood, released by myoglobin
Types of Muscle Fibers
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classified on how they make their ATP
Fast fibers = fast glycolytic
Slow fibers = slow oxidative
Intermediate fibers = fast glycolytic-oxidative
Percentage of fast versus slow fibers is genetically
determined
• Proportions vary with the muscle
– neck, back and leg muscles have a higher proportion of postural,
slow oxidative fibers
– shoulder and arm muscles have a higher proportion of fast
glycolytic fibers
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Fast Fibers: Large in diameter
Contain densely packed myofibrils
Large glycogen reserves
powerful, explosive contractions
fatigue quickly
• Fast oxidative-glycolytic (fast-twitch A)
– red in color (lots of mitochondria, myoglobin & blood vessels)
– split ATP at very fast rate; used for walking and sprinting
• Fast glycolytic (fast-twitch B)
– white in color (few mitochondria & BV, low myoglobin)
– anaerobic movements for short duration; used for weight-lifting
• Slow fibers: Half the diameter of fast fibers
– Three times longer to contract
– Continue to contract for long periods of time
– longest to fatigue
• e.g. marathon runners
Classification
• According to arrangement of fibers and fascicles
– Parallel muscles
• Parallel to long axis of muscle
– Convergent muscles
• Fibers converge on common attachment site
– Pennate muscles
• One or more tendons run through body of muscle
• Unipennate, bipennate, multipennate
– Circular muscles
• Fibers concentrically arranged
Bones & Muscles: Origins and Insertions
• Origin – portion of the skeletal muscle that attaches to the more stationary
structure
• Insertion - portion of the skeletal muscle that attaches to the more moveable
structure
• majority of muscles originate or insert from bony markings on the skeleton
• markings: specific elevations, depressions, and openings of bones
– bony markings provide distinct and characteristic landmarks for orientation and identification
of bones and associated structures.
• many markings come together to form a joint
• many markings are often the sites for the origins or insertions of muscles, or
a channel for the passage of nerves and vessels
• 3 kinds of bony markings:
– depressions – fossa, fissure
– openings – foramen, canal, meatus
– processes – condyles, spines, crests, heads, lines, ridges, trochanters, tubercles
Muscle Names
• Yield clues to muscle orientation, location or
function
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Biceps brachii (two heads, arm)
Vastus femoris (large, femur)
Orbicularis oculi (circular, eye)
Rectus abdominus (erect, abdomen)
Musculoskeleton: Axial Division
• Axial skeleton: 80 bones
– main axis of the body
– forms a framework for the protection of delicate
organs
• including the sense organs
• Axial musculature
– axial musculature arises from and inserts on the
axial skeleton
– responsible for positioning the head and spinal
column – postural muscles
– also moves the rib cage, assisting in breathing
– grouped into 4 groups:
– 1. muscles of the head and neck
– 2. muscles of the vertebral column
– 3. the abdominals - oblique and rectus muscles
– 4. muscles of the pelvic floor
Muscles of the Head and Neck
• Muscles of facial expression – know for practical
• Extrinsic eye muscles – know for practical
• Muscles of mastication – check your list for
practical
• Muscles of the tongue – check your list for
practical
• Muscles of the pharynx – don’t worry about these
• Muscles of the anterior neck – know for
practical
Muscles of Facial Expression
• Originate on surface of skull
• Largest group associated with mouth
– Orbicularis oris
– Buccinator
• Occipitofrontalis muscle
– Movement of eyebrows, forehead, scalp
• Platysma
– Skin of neck, depresses mandible
Muscles of Facial Expression
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Orbicularis oris - puckering
Buccinator - whistling
Occipitofrontalis muscle (Epicranius)
– movement of eyebrows, forehead, scalp
– Front belly = Frontalis (moves eyebrows and
forehead)
– Back belly = Occipitalis (moves back of
scalp)
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Zygomaticus Major and Minor - smiling
Risorius - grinning
Orbicularis oculi – closes eye
Depressor anguli oris - – lowers angle of
mouth
Depressor labii inferioris –depresses lower
lip
Levator labii superioris – raises upper lip
Mentalis - pouting
Platysma – pouting & depresses mandible originate
on surface of skull –
insert on the skin of the face
zygomaticus minor
zygomaticus major
Muscles of Mastication
• Act on the mandible
• Temporalis –
elevates mandible
• Masseter – elevates
mandible
• Medial pterygoid &
Lateral pterygoid
– protract the mandible
and move it side to
side
– Don’t need to know
for practical
Six Extra-Ocular (Oculomotor)
Muscles
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Inferior rectus
Superior rectus
Medial rectus
Lateral rectus
Superior oblique
Inferior oblique
Muscles of the Tongue
• Necessary for speech and swallowing
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Genioglossus
Hyoglossus
Palatoglossus
Styloglossus
palatoglossus
temporalis
styloglossus
hyoglossus
mylohyoid
Anterior Muscles of the Neck
• foundation for the muscles of the tongue and pharynx, move the hyoid up or
down for swallowing & breathing, depress the mandible
– Digastric – two bellies
– Mylohyoid
– Stylohyoid
– Sternohyoid
– Sternothyroid
– Thyrohyoid
– Omohyoid
Anterior Muscles of the Neck
• Foundation for the muscles of the tongue and pharynx
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Digastric
Mylohyoid
Stylohyoid
Sternocleidomastoid
omohyoid
thyrohyoid
sternohyoid
thyroid
gland
Anterior Muscles of the Neck
– Sternocleidomastoid
• two sites of origin – clavicle
and sternum
• inserts onto mastoid process
• both together – flexes head
forward
• individually – laterally flexes
& rotates head to the
opposite side
Anterior Muscles of the Neck
Muscles of the Vertebral Column
• covered by a superficial layer of
back muscles
– Trapezius
– Latissimus dorsi
• superficial and deep layers
• quite complex – multiple origins and
insertions + overlapping
• 5 Groups:
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Splenius group
Erector spinae group
Scalenes
Transversospinalis group
Segmental group
Muscles of the Vertebral Column
• Superficial muscles:
• Splenius group – together they
extend the head and neck,
individually they laterally flex and
rotate to the same side
• Splenius capitis
• Splenius cervicis
Muscles of the Vertebral Column
• Superficial muscles:
• Erector Spinae - spinal extensors
– comprised of capitis, cervicis,
thoracic and lumborum portions
– Spinalis – medial group of
muscles
– capitis, cervicis and thoracis
groups
– Iliocostalis – lateral group of
muscles
– cervicis, thoracis and
lumborum
– Longissimus – in between
these two (intermediate)
Muscles of the Vertebral Column
• Deep muscles:
• Interconnect and stabilize the
vertebrae
• Scalenes – flexes and rotates
neck, used in deep inspiration
• Anterior
• Medial
• Posterior
• Transversospinal group –
extends the vertebral column and
rotates it to the opposite side
• Semispinalis – capitis, cervicis
and thoracis portions
• runs from transverse to spinous
processes
• Multifidus – below the ribcage
Muscles of the Vertebral Column
• Deep muscles:
• Quadratus lumborum flexes the lumbar spine
• Segmental group – extends
and laterally flexes vertebral
column
• Interspinales – run
between spinous
processes
• Intertransversarii – run
between transverse
processes
The Oblique and Rectus Muscles
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Abdominal Oblique and Rectus Muscles
Rectus abdominus – partitioned into 4 sections
-the oblique muscles are connected to
by fibrous “tendinous intersections”
their opposite partners via an aponeurosis
3 Abdominal oblique muscles
(broad, flat tendon)
-the 3 aponeuroses form an “envelope” that
– External oblique (down and in)
encloses the rectus abdominus = rectus
– Internal oblique (up and in)
sheath
– Transversus abdominis (side to side)
– Compress underlying organs
– together – flex the vertebral column
– singly - rotate the vertebral column to the opposite side
The Diaphragm
The Pelvic Floor & Perineum
• pelvic diaphragm or floor = coccygeus & levator ani & external
anal sphincter
– found in the anal triangle- contains the anus
– supports pelvic viscera & resists increased abdominal pressure during
defecation, urination, coughing, vomiting, etc
– pierced by anal canal, vagina & urethra
• additional muscles lie superficial to the pelvic floor = perineal
muscles
– found in the urogenital triangle- contains the external genitalia
– also contains muscles – assist in the erection (male and female)
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Muscles of
the Pelvic
Floor
Musculoskeleton: Appendicular Division
• Appendicular skeleton: 126 bones
– Bones of upper and lower limbs
– Pectoral and pelvic girdles
» connect limbs to trunk
• Appendicular musculature
• originates or inserts on the appendicular
skeleton
• stabilizes or moves components of the
appendicular skeleton
• stabilizes pectoral girdle (i.e. shoulder joint)
• stabilizes pelvic girdle (i.e. hip joint)
• moves the upper and lower limbs
• grouped into 7 distinct groups:
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4 groups move the upper limb
3 groups move the lower limb
Muscles that move the pectoral girdle
• clavicle can be elevated or
depressed or stabilized
– subclavius muscle
• movements of the scapula
are quite complex
– adduction/retraction – rowing
– abduction/protraction – punching or
‘hunching’ of shoulders
– elevation – shrugging
– depression – pull-downs
– superior rotation – jumping jack
– inferior rotation – parallel bars
Muscles that move the pectoral girdle
• POSTERIOR MUSCLES:
• Trapezius muscle – one of the largest
muscles on the back
– affects position of pectoral girdle,
neck, head
-can perform a series of complex motions
-divided into clavo-, acromio- and spinosections (superior, medial and inferior
fibers)
-origin: occipital bone, C7 & all thoracic
vertebrae
-insertion – spine of scapula and lateral 1/3 of
clavicle
-superior fibers – elevate and superiorly rotate
scapula
-medial fibers – retract scapula
-inferior fibers – depress scapula
Muscles that move the pectoral girdle
• POSTERIOR MUSCLES
• Rhomboid muscles: major and minor
– adducts scapula
– origin: C7 to T5 vertebrae
– insertion: on medial border of scapula
• Levator scapulae muscle
– elevates scapula
– origin: C1 through C4
– insertion: medial border of scapula
(above the spine)
• ANTERIOR MUSCLES
• Serratus anterior muscle
– abducts scapula
– origin: first 9 ribs
– insertion: medial border of scapula
• Subclavius
– depresses the clavicle
• Pectoralis minor
– abducts scapula
– rotates it down (inferior)
– origin: ribs 3-5
– insertion: corocoid process of
scapula
Muscles that Move the Arm
• Deltoid
– can be divided into anterior, medial
and posterior fibers
– major arm abductor
– anterior fibers: flex and medially
rotate arm
– medial fibers: prime mover;
abduction of arm
– posterior fibers: extend and laterally
rotate arm
– origin: spine of scapula, acromion and
lateral 1/3 of clavicle
– insertion: deltoid tuberosity of
humerus
Muscles that Move the Arm
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Rotator Cuff muscles:
– surround and stabilize the glenohumeral
joint
– origin: bony fossae and inferior angle of
scapula
– insertion: lesser or greater tubercle of
humerus
– Supraspinatus
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abducts the arm
– Supscapularis
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rotates arm medially
– Infraspinatus
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adducts and rotates arm laterally
– Teres minor
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adducts and rotates arm laterally
Muscles that Move the Arm
• Coracobrachialis
– flexion and adduction at shoulder
– origin at corocoid process of scapula
– insertion on the humerus
• Pectoralis major muscle
– flexes arm shoulder
– adducts and medially rotates arm
– origin: clavicle, sternum and costal
cartilages
– insertion: greater tubercle of humerus
• Latissumus dorsi muscle
– extends arm at shoulder
– adducts and medially rotates arm
– origin: all lumbar vertebrae, sacrum and
coccyx
– insertion: intertubercular groove of
humerus
Summary: Muscle Actions at the Shoulder Joint
Abduction:
1. Deltoid (middle)
2. Supraspinatus
Flexion:
1. Pectoralis Major
2. Deltoid (anterior)
3. Coracobrachialis
Lateral Rotation:
1. Infraspinatus
2. Teres minor
3. Deltoid (posterior)
prime movers in bold
Adduction:
1. Latissimus dorsi
2. Pectoralis major
3. Coracobrachialis
4. Teres major
5. Teres minor
6. Infraspinatus
Extension:
1. Latissimus dorsi
2. Deltoid (posterior)
3. Teres major
4. Triceps brachii (long)
Medial Rotation:
1. Subscapularis
2. Pectoralis Major
3. Latissimus dorsi
4. Teres major
5. Deltoid (anterior)
Muscles that Move the Forearm
• 3 Flexors of the elbow joint:
– all insert either onto the radius or
the ulna
• 1. biceps brachii – “two heads” of
humerus
– long & short heads
– flexes elbow & supinates forearm
– origin: short head - corocoid process
of scapula; long head – scapula
(above glenoid cavity)
– insertion: radial tuberosity of radius
• 2. brachioradialis
– origin: humerus
– insertion: radius (styloid process)
• 3. brachialis
– major flexor of the elbow joint
– origin: humerus
– insertion: coronoid process of ulna
Muscles that Move the Forearm
• 4 Extensors of the elbow
joint:
– different origins – all insert
onto the olecranon process
• 1. triceps brachii – “three
heads” of humerus
– long, medial & lateral heads
– extends elbow
– origin: short & medial heads –
back of humerus; long head –
scapula (below glenoid cavity)
– insertion: olecranon process
• 2. anconeus
– 4th extensor of the elbow joint
– origin: lateral epicondyle of
humerus
Muscle that Pronate & Flex
• Pronator teres
– medial epicondyle to radius
so contraction turns palm
of hand down towards floor
• Flexor carpi muscles
– radialis
– ulnaris
• Flexor digitorum
muscles
– superficialis
– profundus
• Flexor pollicis
– longus
– brevis
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Muscles that Supinate & Extend
• Supinator
– lateral epicondyle of humerus to
radius
– supinates hand
• Extensors of wrist and fingers
– extensor carpi
– extensor digitorum
– extensor pollicis
– extensor indicis
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Intrinsic Muscles, Tendons and Ligaments of the
Hand
Retinaculum
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Tough connective tissue band that helps hold tendons in place
Flexor retinaculum runs from pisiform/hamate to scaphoid/trapezium
– overlies 10 tendons + median nerve
– flexor carpi radialis, pollicis longus, digitorum superioficialis & digitorum profundus
– carpal tunnel syndrome = painful compression of median nerve due to narrowing passageway
under flexor retinaculum
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Muscles of the pelvic girdle and
lower limbs
• Three groups
– Muscles that move the thighs
– Muscles that move the leg
– Muscles that move the foot and toes
Muscles that Move the Thigh at the Hip Joint
• muscles that move the thigh can perform multiple movements
– e.g. sartorius – “tailor muscle”
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hip flexion
lateral rotation of femur
flexion of knee
medial rotation of leg
• these muscles span the hip joint
– hip joint – another ball-in-socket joint capable of multiple planes of
motion
• movements at the hip joint
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abduction
adduction
flexion
extension
medial rotation
lateral rotation
circumduction
Muscles that Move the Thigh at the Hip Joint
• can categorize the muscles of the thigh & their movements
this way
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Medial compartment – hip adductors
Lateral compartment – hip abductors
Anterior compartment – hip flexors (knee extensors)
Posterior compartment – hip extensors & knee flexors
Gluteal region – hip extensors and abductors
Deep Gluteal region – lateral rotators
Muscles that Flex the Thigh
• 9 Hip flexors:
– these muscles also either adduct or
abduct the thigh
– iliopsoas – made up two muscles:
iliacus & psoas major
• major hip flexors
• origin – lumbar vertebrae and iliac fossa
• insertion – lesser trochanter of femur
– sartorius - longest muscle
• origin – anterior superior iliac spine
• insertion - tibia
– tensor fascia latae – also abducts the
thigh by pulling on its tendon; medially
rotates
• origin – iliac crest
• insertion – tibia by way of the iliotibial tract
or IT band
– rectus femoris – part of the quadriceps
– 3 adductors + pectineus
Muscles that Extend the Thigh
• 5 Hip extensors:
– originate from pelvis & sacrum and insert
into the femur, tibia and fibula
– some also laterally rotate the thigh
– 3 Hamstrings – also flexors of the knee
– hamstring part (lowest part) of adductor
magnus
– Gluteus maximus
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major hip extensor
extension and lateral rotation of hip
pulls on iliotibial tract
origin – iliac crest, sacrum and coccyx
insertion – gluteal tuberosity on femur
Muscles that Adduct the Thigh
•
5 adductors - adducts hip
– originate from pubis and insert onto
the linea aspera of femur
– Adductor magnus
– biggest of the adductors
– divided into an adductor part
and a hamstring part
– hamstring part also extends the
hip
– adductor part also flexes the hip
– Adductor brevis
– Adductor longus
– Pectineus
– pectineus, adductor longus and
brevis are also hip flexors
– Gracilis
– also flexes the knee
Muscles that Abduct the Thigh
• 4 Hip Abductors:
• originate from pelvis and insert
onto the greater trochanter of
femur
• Gluteus Medius
• origin – iliac crest
• Gluteus Minimus
• origin - anterior gluteal line
• Sartorius
• Tensor fascia latae
Muscles that Rotate the Thigh
• 9 lateral rotators of the thigh:
• most insert onto the greater trochanter
• Piriformis
• Obturator internus
• Obturator externus
• Superior gemellar
• Inferior gemellar
• Quadratus femoris
• Gluteus maximus (medius and minimus)
• Adductor magnus
• 3 medial rotators:
• Sartorius
• Gluteus medius and minimus –
when hip is extended
• Adductor brevis
Summary: Muscle Actions at the Hip Joint
Abduction:
1. Gluteus medius
2. Gluteus minimus
3. Tensor fascia latae
4. Sartorius
Flexion:
1. Iliopsoas
2. 3 adductors
3. Pectineus
4. Sartorius
5. Rectus femoris
6. Gracilis
Lateral Rotation:
1. Adductor magnus (hamstring)
2. Gluteus maximus
3. Sartorius
4. 2 Obturators
5. 2 Gemellars
6. Quadratus femoris
7. Piriformis
prime movers in bold
Adduction:
1. Adductor longus
2. Adductor brevis
3. Adductor magnus
4. Pectineus
Extension:
1. Gluteus maximus
2. Adductor magnus (ham.)
3. Biceps femoris (long head)
4. Semimembranosus
5. Semitendinosus
Medial Rotation:
1. Gluteus medius
2. Gluteus minimus
3. Adductor brevis
4. Tensor fascia latae
Muscles that Extend the Leg
• 4 Extensor muscles of the leg or
Quadriceps femoris – “four heads” of the
femur
– for leg extension at the knee joint
– found on the anterior and lateral
surfaces of the thigh
– originate from the pelvis (rectus
femoris) and femur ( 3 vastus muscles)
– all insert onto the tibial tuberosity
on the tibia via the patellar ligament
– Rectus femoris – because of its origin on
the anterior inferior iliac spine – also a hip
flexor
– Vastus lateralis
– Vastus medialis
– Vastus intermedius
Muscles that Flex the Leg
•
11 Flexors of the leg
• for flexion of the knee joint
• some also extend the hip (hamstrings)
• found in the posterior compartment of the
thigh
• originate from the pelvis and insert onto
the tibia and fibula
• 3 Hamstrings: all originate on the ischial
tuberosity
– Biceps femoris – 2 heads
– Semimembranosus
– Semitendinosus
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common insertion with
semimembranosus onto tibia
3 Adductor muscles
Sartorius
Gracilis
Muscles that Flex the Leg
•
11 Flexors of the knee
• Gastrocnemius
• gastroc = belly
• kneme = leg
• also plantar flexes foot with soleus
• origin – femoral condyles
• insertion – calcaneus via the Achilles tendon
• Popliteal muscle
– poplit = back of knee
– Unlocks knee joint
– origin – lateral condyle of femur
– insertion - tibia
• Plantaris
• weak knee flexor
Muscles that Plantar Flex the Foot
• Gastrocnemius, soleus and plantaris are also plantarflexors of the
foot
• Tibialis posterior
– also inverts the foot (turn in)
• Fibularis/Peroneus
– longus and brevis
– also evert the foot (turn out)
• Flexor digitorum and hallicis longus
– also curl the toes
Muscles that Dorsiflex the Foot
• 4 muscles are responsible for dorsiflexion of foot (toes up)
• Tibialis anterior
– also inverts the foot
• Fibularis/Peroneus tertius
– everts the foot with the other
2 fibularis muscles
• Extensor digitorum and hallicis longus