Muscular System

Muscular System

2012-2013

Vocab development • Calat- something inserted • Erg- work• Fasc- bundle • -gram- something written• Hyper- over, more• inter;- between • Iso-equal• Laten- hidden• Myo- muscle

• Reticul- a net• Sarco- flesh• Syn- together• Tetan- stiff• -tonic- stretched• -troph- well fed • Voluntar- of one’s free

will

Introduction

• Muscles are organs made of cells that use chemical energy stored in nutrients to exert a force on the structures they are attached to.

• Muscle actions provide:– Muscle tone– Propel body fluids and food– Generate the heartbeat– Distribute heat

Introduction

• 3 types of muscle– Skeletal– Smooth– Cardiac

Structure of Skeletal Muscle

• Composed mostly of skeletal muscle tissue, nervous tissue, blood, and other connective tissues

• Layers of connective tissue enclose and separate all parts of a skeletal muscle allowing the parts to move somewhat independently.

Skeletal Muscle: Connective Tissue Coverings

• Fascia– Separates a muscle from its adjacent muscles;

covers the whole muscle• Tendon– Connect a muscle to a bone

• Aponeuroses – connects muscle to bone and other muscles

Skeletal Muscle: Connective Tissue Coverings

• Epimysium– Closely surrounds a skeletal muscle

• Perimysium– Extends inward from epimysium & separates the

muscle tissue into small sections called fascicles • Endomysium – Each muscle fiber within a fascicle is covered by

this

Skeletal Muscle Fibers

• Each muscle fiber forms from many undifferentiated cells that fuse together

• Each muscle fiber is multinucleate• Shaped like a long, thin cylinder with rounded

ends• Sarcolemma- just beneath the muscle cell

membrane• Sarcoplasm- cytoplasm of the fiber


• Myofibrils – Bundles of threadlike structures found within muscle

fibers– Fundamental in the muscle contraction mechanism – Consist of 2 types of proteins

• Myosin- thick filaments• Actin- thin filaments

– Alternating of the myosin & actin causes the striations found in skeletal muscle • Sarcomeres- repeating patterns of striations along each muscle

fiber


• Sarcoplasmic reticulum – Within the sarcoplasm of a muscle fiber – Network of channels that surrounds each

myofibril

Skeletal Muscle Contraction

• Complex interaction of cellular and chemical pieces

• The result is movement within the myofibrils where the filaments of actin and myosin slide past each other causing the sarcomere to shorten


• Energy Sources – ATP • Muscle fiber only has enough ATP to contract briefly so

it must be able to regenerate ATP – Creatine Phosphate • Initial source of energy to regenerate ATP • Much more abundant in muscle fibers than ATP, but it

cannot supply energy directly to the cell – Cellular Respiration


• 10 steps to muscle contraction1. An action potential is conducted down a motor

neuron axon 2. The motor neuron terminal releases the

neurotransmitter acetylcholine (ACh)3. ACh binds to ACh receptors on the muscle fiber4. The sarcolemma is stimulated, an action potential is

generated, and the impulse is conducted over the surface of the muscle fiber and deep into the fiber through the transverse tubules.

Skeletal Muscle Contraction 5. The impulse reaches the sarcoplasmic reticulum, and

calcium channels open. 6. Calcium ions diffuse from the sarcoplasmic reticulum into

the sarcoplasm and bind to tropin molecules. 7. Tropomyosin molecules move and expose specific sites on

actin. 8. Actin and myosin link, forming cross-bridges.9. Thin (actin) filaments are pulled toward the center of the

sarcomere by myosin cross-bridges increasing the overlap of the thin and thick filaments.

10. The muscle fiber contracts.

Skeletal Muscle Relaxation • 1. Acetylcholinesterase decomposes acetylcholine, and

the muscle fiber membrane is no longer stimulated.• 2. Calcium ions are actively transported into the

sarcoplasmic reticulum. • 3. ATP breaks linkages between actin and myosin

filaments without breakdown of ATP itself • 4. Breakdown of ATP “cocks” the myosin heads. • 5. Troponin and tropomyosin molecules inhibit the

interaction between myosin and actin filaments.• 6. Muscle fiber remains relaxed until it is stimulated again.

Muscle Fatigue

• Caused by– Decreased blood flow– Ion imbalances due to repeated stimulation– Psychological loss of desire to continue – Lactic acid accumulation – Oxygen debt

• Lactic acid accumulation – Accumulates in the muscles when ATP production

goes from aerobic to anaerobic

Muscular Responses

• Threshold Stimulus – A muscle fiber remains unresponsive until a

certain strength of stimulation is reached, once this is reached an action potential is generated and the process of muscle contraction begins

Muscular Responses

• Recording a Muscle Contraction

Muscular Responses

• Summation–

Muscular Responses

• Types of Contractions– Isotonic Contractions (equal force –change in

length)—allow you to move things • Concentric-muscle contracts with greater force than

resistance and shortens • Eccentric- muscle contracts with less force than

resistance and lengthens – Isometric Contractions – (equal length- change in

force) – allow you to sit and hold your posture

Muscular Responses

• Fast & Slow Twitch Muscle Fibers– 3 types

• Slow twitch fibers (red fibers) – Produce ATP from oxygen making them more resistant to fatigue – These fibers can contract for long periods of time without fatigue

• Fast twitch fibers (white fibers) – Produce ATP primarily through glycolysis – Can contract rapidly but also fatigue rapidly as lactic acid

accumulates in them • Intermediate Fibers (white fibers)

– Can contract rapidly and also have a larger respiratory capacity so they don’t fatigue like fast-twitch fibers

Smooth Muscles

• Smooth muscles lack striations• Cells have only one nucleus• 2 major types of smooth muscles– Multiunit – Visceral

Smooth Muscles

• Multiunit Smooth Muscle – Muscle fibers function as separate units – Found in the irises of the eyes & walls of large

blood vessels – Contract after stimulation by neurons or certain

hormones

Smooth Muscles • Visceral Smooth Muscle– Fibers respond as a single unit – Found in the walls of hollow organs (intestines, stomach,

bladder, uterus) – Two features- conduction of impulses and rythmicity produce

peristalsis• Peristalsis- wavelike motion of contraction

– Peristalsis is what help your body move food from organ in the digestive system to the next

– Vascular smooth muscle• Found in the walls of small blood vessels where it helps control blood

pressure and blood flow

Cardiac Muscle

• Found only in the heart • Composed of striated cells joined end to end• Opposite ends of cardiac cells are connected

by intercalated discs– Help join cells, transmit the force of contraction, &

diffuse ions from cell to cell

Skeletal Muscle Actions

• Skeletal action depends on – Type of joint it is associated with– The way the muscle is attached on either side of

the joint


• Body Movement – When a body part moves bones and muscles

interact as a lever – 3 types of levers• 1st class- resistance-fulcrum, force (seesaw; when the

arm straightens at the elbow) • 2nd class- fulcrum- resistance- force (wheelbarrow;

when you chew something up) • 3rd class- resistance-force-fulcrum (tweezers- when the

arm bends at the elbow)


• Origin and Insertion– Origin- less moveable end of the muscle– Insertion- more moveable end of the muscle – When a muscle contracts • Insertion is pulled toward its origin • Head of the muscle is the part closest to its origin

Skeletal Muscle Action


• Interaction of Skeletal Muscles– Agonist- muscle that causes an action – Synergists- muscles that work together– Prime mover- muscle that does most of the work

during an action – Antagonists- muscle that opposes action

Major Skeletal Muscles

• Muscles of Facial Expression – Innervated by the facial nerve (CN VII) – Lack of symmetry in facial expression may indicate

nerve damage

Muscles of Facial Expression

• Orbicularis oculi– orbicular= circular– Oculi= eye – Origin: orbital rim, frontal

& maxillary bones– Insertion: lateral region of

eye, some encircle the eye– Action: closing the eyelid– Expression: form’s crows

feet


• Corrugator– Origin: frontal bone– Insertion: eyebrow– Action: draws eyebrow

medially & inferiorly– Expression: frowning &

suffering


• Procerus– Origin: fascia covering

the lower nasal bone & upper lateral nasal cartilage

– Insertion: skin between and above the eyebrows

– Action: causes transverse wrinkles over the bridge of the nose

– Expression: squinting


• Nasalis – Circles the opening of

the nostrils– Has 2 parts:

• Dilator naris • Compressor naris

– Action: dilates & compresses nostrils • Wiggles your nostrils


• Epicranius– Origin: occipital bone – Insertion: skin around

the eye & orbicularis oculi

– Action: elevates eyebrows, moves scalp forward & backward

– Expression: surprise


• Orbicularis Oris– Oribicular= circle– oris = mouth – Origin: encircles mouth– Insertion: angle of mouth – Action: encloses &

protrudes up; helps keep food on occlusal surfaces during chewing

– Expression: closing or pursing lips


• Quadratus Labii Superioris – 4 muscles of the upper

lip • Levator labii superioris

alaeque nasi• Levator labii superioris• Zygomaticus minor• Zygomaticus major

– Allow you to frown and smile


• Quadratus Labii Superioris cont…– Levator labii superioris

alaeque nasi• Origin: maxilla• Insertion: nose• Action: dilates nostrils &

raises upper lip


• Quadratus Labii Superioris – Levator labii superioris

• Origin: maxilla• Insertion: upper lip• Action: raises upper lip • Expression: scorn

Muscles of Facial Expresssion • Quadratus Labii Superioris

Cont…– Zygomaticus minor

• Origin: zygomatic bone• Insertion: upper lip• Action: raises upper lip• Expression: scorn

– Zygomaticus major • Origin: zygomatic bone• Insertion: angle of mouth• Action: elevates the corner

of the mouth • Expression: smiling

Muscles of Facial Expression • Levator Anguli Oris– Origin: canine fossa (on

the maxilla)– Insertion: orbicularis oris– Action: elevates the

angle of the mouth – Expression: smiling

(laughing)


• Smiling– Produced by the

contraction of 2 facial muscles: • Zygomaticus major • Oribicularis oculi


• Risorius– Origin: fasica superficial

to masseter muscle– Insertion: angle of the

mouth– Action: pulls angle of the

mouth laterally– Expression: smiling

widely; grinning


• Depressor labii inferioris– Origin: mandible– Insertion: lower lip– Action: depresses the

angle of the mouth – Expression: sadness;

grief


• Depressor Anguli Oris – A.K.A triagularis – Origin: mandible– Insertion: angle of the

mouth– Action: depresses angle

of the mouth– Expression: frowning


• Mentalis – Origin: mandible near

the incisive fossa– Insertion: skin of the

chin– Action: pulls skin of chin

upward; protrudes lower lip; raise lower lip

– Expression: doubt; disdain

Muscles of Facial Expression • Buccinator

– 2 origins: • Pterygomandibular raphe • Alveolar process of the mandible

& maxilla– Insertion: orbicularis oris– Action: draws the corners of

the lips laterally, compresses cheek, helps keep food on occlusal surface during chewing

– Plays and important role in chewing

– Makes up the musculature of the cheek

Muscles of Facial Expresion • Laughter

– Muscle that form the core of the laughter of exhilartion: • Zygomatic major• Oribicularis oculi

– Muscles used to enhance laughter:• Levator labii superioris• Risorius • Mentalis• Depressor anguli oris• Orbicularis oris


• Auriculares– 3 small muscles around

the auricle of the ear– Not well developed in

man– Allow you to wiggle your

ears

Muscles of Facial Expression • Platysma

– Broad, thin, superficial muscle

– Origin: fascia below clavicle– Insertion: lower border of

mandible from canine to second molar

– Action: depresses angle of the mouth, wrinkles the skin of the neck & upper chest

– Expression: dejection, horror, grimacing

Muscles of Mastication

• 4 pairs of muscles attached to the mandible – 3 pairs close the lower jaw – 1 pair lowers the jaw & allows side to side

movement


• Masseter – Origin: zygomatic arch – Insertion: lateral surface

of the mandible – Action: elevates the

mandible


• Temporalis – Origin: temporal fossa – Insertion: coronoid fossa

of the mandible – Action: elevates the

mandible; retraction


• Lateral Pterygoid– Origin: sphenoid bone– Insertion: mandibular

condyle– Action: depresses &

protracts mandible


• Medial Pterygoid– Origin: sphenoid,

palatine, & maxilla – Insertion: medial surface

of the mandible – Action: elevates

mandible; moves it from side to side

Muscles That Move the Head and Vertebral Column

• Sternocleidomastoid– Origin:sternum & collar

bone – Insertion: temporal bone– Action: pulls head to one

side, flexes neck or elevates the sternum

Muscles That Move the Head & Vertebral Column

• Splenis Capitis– Origin: spinous process

of lower cervical & upper thoracic vertebrae

– Insertion: occipital bone – Action: rotates head,

bends head to one side, or extends neck


• Semispinalis capitis– Origin: processes of

lower cervical & upper thoracic vertebrae

– Insertion: occipital bone – Action: elevates head &

rotates the head

Muscles that Move the Head & Vertebral Column

• Quadratus lumborum – Origin: iliac crest– Insertion: upper lumbar

vertebrae & twelfth rib – Action: aids in breathing,

extends lumbar region of vertebral column


• Erector Spinae – Origin & Insertion at

many locations on the axial skeleton

– Action: extend & rotate the head & maintain the erect position of the vertebral column

Muscles That Move the Pectoral Girdle

• Work closely with the muscles that move the arm

• Connect the scapula to near by bones & help move the scapula up, down, forward, & backward


• Trapezius – Origin: occipital bone &

spines of the cervical & thoracic vertebrae

– Insertion: clavicle, spine, & acromion process of scapula

– Action: rotates scapula; shrugs shoulders


• Rhomboid Major – Origin: spines of upper

thoracic vertebrae– Insertion: medial border

of the scapula – Action: retracts,

elevates, & rotates the scapula


• Rhomboid Minor – Origin: spines of the

lower cervical vertebrae– Insertion: medial border

of the scapula – Action: retracts &

elevates the scapula


• Levator Scapulae – Origin: transverse

process of the cervical vertebrae

– Insertion: medial margin of the scapula

– Action: elevates scapula


• Serratus Anterior – Origin: outer surfaces of

upper ribs– Insertion: ventral surface

of scapula – Action: pulls scapula

anteriorly & downward


• Pectoralis Minor – Origin: sternal ends of

upper ribs – Insertion: coracoid

process of scapula – Action: pulls scapula

forward and downward to raise ribs

Muscles That Move the Forearm

• Most forearm muscle movements are produced by muscles that connect the radius or ulna to the humerus or pectoral girdle.

• Muscles that move the forearm are grouped into three categories: – Flexors- – Extensors– Rotators


• Flexor: – Biceps Brachii

• Origin: above the glenoid cavity of the scapula

• Insertion: radius• Action: flexes elbow &

rotates the hand laterally (turning a doorknob or screw driver)


• Flexor– Brachialis

• Origin: anterior shaft of the humerus

• Insertion: coronoid process of ulna

• Action: Flexes elbow – Strongest flexor of the

elbow


• Flexor:– Brachioradialis

• Origin: distal lateral end of humerus

• Insertion: lateral surface of the radius above the styloid process

• Action: flexes elbow


• Extensor – Triceps Brachii

• Origin: below glenoid cavity & lateral & medial surfaces of the humerus

• Insertion: olecranon process of the ulna

• Action: extends elbow • This is the only muscle on

the back of the arm.


• Rotators:– Supinator

• Origin: lateral epicondyle of humerus & ulna

• Insertion: lateral surface of radius

• Action: rotates forearm laterally and supinates the hand (palm facing upward)


• Rotators:– Pronator teres

• Origin: medial epicondyle of humerus and the ulna

• Insertion: lateral surface of radius

• Action: rotates forearm medially and pronates the hand


• Rotator:– Pronator Quadratus

• Origin: anterior distal end of ulna

• Insertion: anterior distal end of radius

• Action: rotates forearm medially and pronates hand

Muscles That Move the Hand

• Movements of the hand include movements of the wrist and fingers.

• 2 major groups of muscles– Flexors- on anterior side of the forearm – Extensors- on the posterior side of the forearm


• Flexors – Flexor carpi radialis

• Origin: medial epicondyle of the humerus

• Insertion: base of the 2nd & 3rd metacarpals

• Action: flexes wrist & abducts hand


• Flexor– Flexor carpi ulnaris

• Origin: medial epicondyle of the humerus

• Insertion: carpals & metacarpals

• Action: flexes the wrist & adducts the hand

Muscles that Move the Hand

• Flexors– Palmaris longus

• Origin: medial epicondyle of humerus

• Insertion: fascia of the palm

• Action: flexes wrist; like you are telling someone to come here


• Flexors– Flexor Digitorum

Profundus • Origin: anterior surface of

the ulna • Insertion: bases of distal

phalanges in fingers 2-5 • Action: flexes distal joints

of fingers


• Flexor– Flexor digitorum

superficialis • Origin: humerus • Insertion: tendons of

fingers • Action: flexes the fingers

and wrist


• Extensor – Extensor Carpi Radialis

Longus • Origin: distal end of the

humerus • Insertion: base of 2nd

metacarpal • Action: extends wrist and

abducts the hand


• Extensor– Extensor carpi radialis

brevis • Origin: lateral epicondyle

of the humerus • Insertion: base of 2nd & 3rd

metacarpals • Action: extends wrist &

abducts hand


• Extensors – Extensor carpi ulnaris

• Origin: lateral epicondyle of humerus

• Insertion: base of the 5th metacarpal

• Action: extends wrist & adducts hand


• Extensor – Extensor Digitorum

• Origin: lateral epicondyle of the humerus

• Insertion: posterior surface of phalanges in fingers 2-5

• Action: extends fingers

Muscles that Move the Arm

• Flexors – Coracobrachialis

• Origin: coracoid process of the scapula

• Insertion: shaft of the humerus

• Action: flexes & adducts the arm


• Flexor– Pectoralis major

• Origin: clavicle, sternum, & costal cartilages of upper ribs

• Insertion: humerus • Action: flexes, adducts,

and rotates arm medially


• Extensor– Teres Major

• Origin: lateral border of scapula

• Insertion: humerus • Action: extends, adducts,

and rotates the arm medially


• Extensor– Latissimus Dorsi

• Origin: spines of scral, lumbar, & lower thoracic vertebrae, iliac crest, & lower ribs

• Insertion: humerus • Action: extends, adducts,

and rotates the arm medially, or pulls the should downward & back


• Abductors – Supraspinatus

• Origin: posterior surface of scapula above spine

• Insertion: humerus• Action: abducts the arm


• Abductors – Deltoid

• Origin: acromion process, spine of the scapula, & clavicle

• Insertion: humerus • Action: abducts, extends,

& flexes the arm


• Rotators – Subscapularis

• Origin: Anterior surface of scapula

• Insertion: humerus• Action: rotates arm

medially


• Rotators – Infraspinatus

• Origin: posterior surface of scapula below spine

• Insertion: humerus • Action: rotates arm

laterally


• Rotators – Teres Minor

• Origin: lateral border of scapula

• Insertion: humerus • Action: rotates arm

laterally

Muscles of the Abdominal Wall

• Muscles of the abdominal wall connect the rib cage & vertebral column to the pelvic girdle

• Linea alba- band of tough connective tissue that extends from the xiphoid process of the sternum to the pubic symphysis & provides attachment for some of the abdominal muscles

• Contraction of these muscles helps move air out of the lungs during forceful exhalation & other everyday functions of the body


• External oblique – Origin- outer surfaces of

the lower ribs – Insertion- Outer lip of

iliac crest & linea alba – Action- Tenses

abdominal wall & compresses abdominal contents


• Internal Oblique – Origin- crest of ilium &

inguinal ligament – Insertion- cartilages of

the lower ribs, linea alba, & crest of the pubis

– Action- Tenses abdominal wall & compresses abdominal contents


• Transversus abdominis – Origin- costal cartilages of

the lower ribs, processes of the lumbar vertebrae, lip of iliac crest, & inguinal ligament

– Insertion- linea alba & crest of pubis

– Action- tenses abdominal wall & compresses abdominal contents


• Rectus Abdominis – Origin- Crest of the pubis

& pubic symphysis – Insertion- xiphoid

process of sternum & costal cartilage

– Action- tenses the abdominal wall & compresses abdominal contents & also flexes the vertebral column

Muscles that Move the Thigh

• Muscles that move the thigh are attached to the femur & to part of the pelvic girdle – Important exceptions: sartorius & rectus femoris

• Muscles can be separated into 2 groups:– Anterior- primarily flexes the thigh; advance the

lower limb when walking – Posterior- primarily extends, abducts, or rotates

the thigh

Muscles that Move the Thigh: Anterior Group

• Psoas major– Origin: lumbar

intervertebral discs; bodies and transverse processes of lumbar vertebrae

– Insertion: lesser trochanter of the femur

– Action: flexes the thigh

Muscles that Move the Thigh: Anterior Group

• Iliacus – Origin: Illiac fossa of

ilium – Insertion: lesser

trochanter of the femur – Action: Flexes thigh

Muscles that Move the Thigh: Posterior Group

• Gluteus maximus – Origin: sacrum, coccyx, &

posterior surface of the ilium

– Insertion: posterior surface of the femur & fascia of the thigh

– Action: extends hip; helps straighten the lower limb at the hip when you walk, run, or climb


• Gluteus minimus – Origin: lateral surface of

the ilium– Insertion: greater

trochanter of the femur – Action: abducts &

rotates the thigh medially


• Gluteus medius – Origin: lateral surface of

the ilium– Insertion: greater


rotates thigh medially


• Piriformis – Origin: anterior surface

of the sacrum – Insertion: greater


rotates the thigh medially ; stabilizes the hip


• Tensor fasciae latae – Origin: anterior iliac

crest– Insertion: greater

trochanter of the femur – Action: abducts, flexes,

& rotates thigh medially

Muscles that Move the Thigh: Adductors

• Pectineus – Origin: spine of the pubis – Insertion: femur distal to

lesser trochanter– Action: Flexes & adducts

thigh


• Adductor brevis – Origin: pubic bone – Insertion: posterior

surface of femur – Action: adducts & flexes

thigh


• Adductor longus – Origin: pubic bone near

the pubic symphysis– Insertion: posterior

surface of the femur – Action: adducts & flexes

the thigh


• Adductor magnus – Origin: Ischial tuberosity – Insertion: posterior

surface of the femur– Action: adducts thigh,

posterior portion extends & anterior portion flexes thigh


• Gracilis – Origin: Lower edge of

pubic symphysis– Insertion: medial surface

of the tibia – Action: adducts thigh &

flexes knee

Muscles that Move the Leg

• Connect the tibia or fibula to the femur or pelvic girdle.

• Two major groups:– Flexors– Extensors


• Hamstring Group – Biceps femoris

• Origin: ischial tuberosity & linea aspera

• Insertion: head of fibula & lateral condyle of tibia

• Action: flexes knee, rotates leg laterally & extends thigh


• Hamstring Group – Semitendinosus

• Origin: ischial tuberosity • Insertion: medial surface

of the tibia • Action: flexes knee,

rotates leg medially & extends thigh


• Hamstring Group– Semimembranosus

• Origin: ischial tuberosity• Insertion: medial condyle

of tibia • Action: Flexes the knee,

rotates the leg medially & extends the thigh


• Sartorius – Origin: anterior superior

iliac spine – Insertion: medial surface

of tibia – Action: flexes knee &

hip, abducts & rotates thigh laterally


• Quadriceps Group– Rectus Femoris

• Origin: spine of the illium & margin of the acetabulum

• Insertion: patella by tendon, which continues as the patellar ligament to the tibia

• Action: extends knee, flexes thigh


• Quadriceps Group– Vastus Lateralis

• Origin: greater trochanter & posterior surface of the femur

• Insertion: patella by tendon, which continues as patellar ligament to the tibia

• Action: extends knee


• Quadriceps Group– Vastus medialis

• Origin: medial surface of the femur




• Quadriceps Group – Vastus intermedius

• Origin: anterior & lateral surfaces of femur



Muscles that Move the Foot

• Movements of the foot include movements of the ankle & toes

• Attach to the femur, tibia, & fibula to bones of the foot • Move the foot upward (dorsiflexion) or downward

(plantar flexion) and turn the foot so the plantar surface faces medially (inversion) or laterally (eversion)

• 4 types: dorsal flexors, plantar flexors, invertor, evertor


• Dorsal Flexor – Tibialis Anterior

• Origin: lateral condyle & lateral surface of the tibia

• Insertion: tarsal bone & first metatarsal

• Action: dorsiflexion & inversion of foot


• Dorsal Flexor – Fibularis Tertius

• Origin: anterior surface of the tibia

• Insertion: dorsal surface of the 5th metatarsal

• Action: dorsiflexion & eversion of the foot


• Dorsal Flexor – Extensor Digitorum

Longus • Origin: lateral condyle of

tibia & anterior surface of the fibula

• Insertion: dorsal surfaces of 2nd & 3rd phalanges of the 4 lateral toes

• Action: dorsiflexion & eversion of the foot, extends toes


• Dorsal Flexor – Extensor Hallucis Longus

• Origin: anterior surface of the fibula

• Insertion: distal phalanx of the big toe

• Action: extends big toe, dorsiflexion & inversion of foot

Muscle that Move the Foot

• Plantar Flexor– Gastrocnemius

• Origin: lateral & medial condyles of femur

• Insertion: posterior surface of calcaneus

• Action: plantar flexion of foot, flexes knee


• Plantar Flexor – Soleus

• Origin: head & shaft of fibula & posterior surface of the tibia

• Insertion: posterior surface of the calcaneus

• Action: plantar flexion of the foot


• Plantar Flexion– Plantaris

• Origin: femur• Insertion: calcaneus • Action: plantar flexion of

foot, flexes knee


• Plantar Flexor – Flexor Digitorum Longus

• Origin: posterior surface of the tibia

• Insertion: distal phalanges of four lateral toes

• Action: plantar flexion & inversion of foot, flexes four lateral toes


• Invertor – Tibialis Posterior

• Origin: lateral condyle & posterior surface of tibia & posterior surface of fibula

• Insertion: tarsal & metatarsal bones

• Action: plantar flexion & inversion of foot


• Evertor – Fibularis Longus

• Origin: lateral condyle of tibia & head & shaft of the fibula

• Insertion: Tarsal & metatarsal bones

• Action: plantar flexion & eversion of foot, supports arch

Muscular System

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