Muscular System
Muscle Types



Skeletal
 Termed striated with Parallel muscle fibers
 Under Conscious control of the nervous system
Smooth
 Non-striated with non-parallel muscle fibers
 Under unconscious control.
Cardiac
 Striated with non-parallel muscle fibers
 Involuntary muscle of the heart
 Under conscious control

Function of Skeletal Muscle
 Movement

Contraction causes and inhibits movement
 Posture/Balance

Helps maintain posture and balance
 Protection

Abdominal muscles protect the abdominal organs

Eyes squint/close to protect underlying tissue
 Temperature

Muscles can contract to produce heat

Types of Muscular Contractions
 Isometric

Muscle tension with no movement
 Example: Plank
 Isotonic

Concentric

Tension by shortening the muscle
 Example: Curling a dumbbell.

Eccentric

Tension by lengthening the muscle
 Example: Negatives

Levers
 Contain 3 parts to it

Fulcrum: joint where movement occurs

Force: muscle or gravity that is applied to the moveable bone.

Resistance: the weight being moved

3 types of levers
 1st class – similar to a seesaw

Fulcrum in the middle with weight/resistance on either side
 Example: Head extension

Fulcrum: Occipital condyles & C1

Force: posterior muscles of the occipital bone

Resistance: Weight of the head.
 2nd Class – Similar to a wheelbarrow

Fulcrum at the end of the lever, with resistance close to the fulcrum/force further away
 Example: Plantar Flexion (Standing on your toes)

Fulcrum: Metatarsal-Phalangeal joint

Force: Attachment of superficial plantar
flexor muscles (Gastrocnemius)

Resistance: Weight of the body.

3rd class – most of them

Fulcrum at the end of the lever, with resistance toward the end
of the lever and force between the resistances.
 Example: Elbow flexion by the biceps brachii

Fulcrum: elbow joint

Force: Attachment of the biceps brachii on the
radius

Resistance: Weight of the forearm
**Basic Knowledge**



O: Origin

Proximal attachment of the trunk (Closest to the trunk)
I: Insertion

Distal attachment of the trunk (Furthest from the trunk)
A: Action

The action of the muscle on one or more articulations
Skeletal Muscles: Upper Torso
Shoulder Girdle

Trapezius

Origin: Begins at the occipital bone, ligamentum nuchae, and the
spines of the thoracic vertebrae

Insertion: Ends at the clavicle, acromion process, and the spine of the
scapula

Action: Elevates the scapula, provides upward rotation of the
shoulder, adducts the scapula
 Example: Shoulder shrug

Rhomboid (Major and Minor)

Origin: Begins at the spinous process of C5 and T1-T5

Insertion: Ends at the medial border of the scapula

Action: Adducts the scapula, provides downward rotation of the shoulder
 Example: During a chin-up the rhomboids draw the scapula’s
medial border down to the spinal column

Serratus Anterior – Shares with the external abdominal oblique

Origin: Begins at the lateral surface of the upper 8 ribs

Insertion: Ends at the medial border of the scapula

Action: Abducts the scapula
 Example: “Boxer Muscle” used to help throw a punch

Levator Scapula

Origin: Begins at the transverse process of C1-C4

Insertion: Ends at the superior angle of scapula

Action: Elevates the scapula
 Example: used with trapezius in shoulder shrug

Pectoralis Minor

Origin: Begins at the outer surface of ribs 3-5

Insertion: Ends at the coracoid process of the scapula

Action: Abduction of the scapula, and provides downward rotation of
the shoulder.
Shoulder Joint

Deltoid – 3 parts to the deltoid
 Spinal Head (Posterior)
 Origin: Begins at the spine of the scapula
 Insertion: Ends at the deltoid tuberosity
 Action: shoulder extension and lateral rotation of
humerus
 Acromial Head (Lateral)
 Origin: Begins at the acromion process of scapula
 Insertion: Ends at the deltoid tuberosity
 Action: Shoulder abduction
 Clavicular Head (Anterior)
 Origin: Begins at the clavicle
 Insertion: Ends at the deltoid tuberosity
 Action: Shoulder flexion, and medial rotation of humerus

Pectoralis Major – most anterior part.

Origin: Begins at the medial part of clavicle/costal cartilage of ribs
1-6

Insertion: Ends at the bicipital groove of the humerus

Action: shoulder extension/flexion, medial
rotation/adduction/horizontal flexion of humerus

Latissimus Dorsi

Origin: Begins at the back of the lumbar/thoracic vertebrae

Insertion: Ends at the bicipital groove of the humerus (anterior portion)

Action: Shoulder extension, adduction/medial rotation of the humerus

Rotator Cuff Muscles – 4 parts to it
 Supraspinatus

Origin: begins at the supraspinous fossa of the
scapula

Insertion: Ends at the Greater tubercle of the
humerus

Action: Initiates shoulder abduction
 Infraspinatus

Origin: Begins at the infraspinous fossa of the
scapula

Insertion: Ends at the Greater tubercle of the
humerus

Action: Lateral humerus rotation
 Teres Minor

Origin: begins at the lateral border of the scapula

Insertion: Ends at the Greater tubercle below the Infraspinatus

Action: Adducts/laterally rotates the humerus
 Subscapularis – medial rotator

Origin: Begins at the subscapular fossa of the scapula (Anterior)

Insertion: Ends at the Lesser tubercle of the humerus (Medial)

Action: Abducts/medially rotates the humerus

Teres Major – blends with the Latissimus Dorsi

Origin: Begins at the lateral border of the scapula

Insertion: Ends at the bicipital groove (front of the humerus)

Action: Shoulder extension/medial rotation of the humerus

Biceps Brachii – 2 parts to it. Bi-articulation (crosses through the glenohumeral joint/elbow joint)


Short Head

Origin: Begins at the coracoid process of the scapula

Insertion: Ends at the radial tuberosity

Action: Shoulder/Elbow flexion
Long Head

Origin: Begins at the supraglenoid tubercle of the scapula

Insertion: Ends at the radial tuberosity

Action: Shoulder/Elbow flexion

Triceps Brachii – 3 Parts to it, Bi-Articulation (crosses through the glenohumeral joint/elbow joint)
 Long Head

Origin: Begins at the infraglenoid tubercle of scapula

Insertion: Ends at the olecranon process of the ulna

Action: shoulder/elbow extension
 Medial Head

Origin: Begins at the posterior/medial aspect of the humerus

Insertion: Ends at the olecranon process of the ulna

Action: Elbow extension
 Lateral Head

Origin: Begins at the lateral aspect of the humerus

Insertion: Ends at the olecranon process of the ulna

Action: Elbow Extension

Coracobrachialis – shoulder + elbow = the brachial

Origin: Begins at the coracoid process of the scapula

Insertion: Ends at the medial shaft of the humerus (Brachialis)

Action: shoulder flexion
Elbow Joint

Brachialis



Origin: Begins at the anterior shaft of the humerus
Insertion: Ends at the coronoid process of the ulna/ulnar tuberosity
Action: Elbow flexion

Broachioradilais

Origin: Begins at the shaft of the humerus, above lateral epicondyle

Insertion: Ends at the styloid process of the radius

Action: Elbow flexion when forearm is semi-pronated

Supinator




Origin: Begins at the lateral epicondyle of the humerus
Insertion: Ends at the anterolateral surface of the radius (Distal to radial
tuberosity)
Action: Supinates the forearm, assists in elbow extension
Pronator Teres – first muscle on the lateral side

Origin: begins on the medial epicondyle of the humerus

Insertion: Ends at the lateral surface of the radius, same as supinator

Action: Pronates the forearm, assists in elbow flexion
Muscle on the anterior of the Forearms – Used in flexion

Palmar Aponeurosis

Layer of tendon covering the palm of the hand

Insertion of Palmaris Longus

Protects vessels/tendons of the palm

Flexor Retinaculum

From the lateral carpal bone to medial carpal bone

Carpal Tunnel is formed with concave configuration

Most tendons pass under the retinaculum

First Layer of the Anterior Forearm Muscles – 4 muscles on superficial
part in anatomical position.
 Flexor Carpi Radialis – middle finger

Origin: Begins at the medial epicondyle of the humerus

Insertion: Ends at the base of 2nd/3rd metacarpals, under
retinaculum

Action: Elbow/Wrist flexion and wrist abduction
 Palmaris Longus – Ring Finger

Origin: Begins at the medial epicondyle of the humerus

Insertion: Ends at the palmar aponeurosis

Action: Elbow/wrist flexion.
 Passes over the retinaculum
 Flexor Carpi Ulnaris – Little Pinky

Origin: Begins at the medial epicondyle of the
humerus/upper ulna

Insertion: Ends at the pisiform. Hamate carpals, base of 5th
metacarpal

Action: Elbow/Wrist flexion and wrist adduction
 Passes under the retinaculum
 Sesmoid bone is embedded in the tendon

2nd Layer of the Anterior Forearm Muscles
 Flexor Digitorum Superficialis

Origin: Begins at the medial epicondyle of the humerus/coronoid
process/shaft of radius

Insertion: Ends at the four tendons attaching to the medial phalanx of the
medial digits

Action: Elbow/wrist/metacarpal-phalangeal/interphalangeal joint flexion

3rd layer of the Anterior Forearm Muscles
 Flexor Digitorum Profundus

Origin: Begins at the upper anterior of the ulna/interosseous membrane

Insertion: Ends at the distal phalanx of the 4 medial digits

Action: flexion at the wrist/metacarpal-phalangeal/1st and 2nd interphalangeal
joints.
 Flexor Pollicis Longus

Origin: Begins at the anterior shaft of the radius

Insertion: ends at the distal phalanx of the thumb

Action: Flexion of the wrist/carpal-metacarpal/ metacarpalphalangeal/interphalangeal joint.

4th layer of the Anterior Forearm Muscles
 Pronator Quadratus – at the wrist for the forearm

Origin: Distal end of the ulna

Insertion: Distal end of the radius

Action: Pronates the forearm
**Synovial membrane allows for the passage of tendons, the membrane gives a smooth surface to slide in. **

Muscles on the Posterior of the Forearm – Used in extension

Superficial Extensor Muscles – 4 of them




Extensor Carpi Radialis Longus

Origin: Begins above the lateral epicondyle of the humerus, below brachioradialis

Insertion: Ends at the base of the 2nd metacarpal

Action: Wrist extension/abduction
Extensor Carpi Radialis Brevis

Origin: Begins at lateral epicondyle of the humerus

Insertion: Ends at the base of 3rd metacarpal

Action: Wrist extension/abduction
Extensor Digitorum Communis

Origin: Begins at the lateral epicondyle of the humerus

Insertion: Ends at the dorsal end of medial four digits

Action: extension at Wrist/metacarpalphalangeal/interphalangeal joint
 Second tendon of the little finger is termed
Extensor Digiti Minimi
 Sent by the extensor Digitorum to the little
pinky.
Extensor Carpi Ulnaris

Origin: Begins at the lateral epicondyle of the humerus

Insertion: Ends at the base of the 5th metacarpal

Action: Wrist extension/adduction

Only muscle on the lateral side helping for
abduction

Deeper Extensor Muscles
 Abductor Pollicis Longus

Origin: Begins at the proximal dorsal surface of radius/ulna and
interosseous membrane

Insertion: Ends at the metacarpal of the thumb

Action: Extend wrist/abducts the thumb
 Extensor Pollicis Longus

Origin: Begins at the posterior surface of the ulna/interosseous
membrane

Insertion: ends at the distal phalanx of the thumb

Action: Extends metacarpal/phalangeal/interphalangeal joints of the
thumb
 Extensor Pollicis Brevis

Origin: Begins at the posterior surface of the radius/interosseous
membrane

Insertion: Ends at the proximal phalanx of the thumb

Action: Extends the wrist/metacarpal-phalangeal joint of the thumb
 Extensor Indicis

Origin: Begins at the posterior surface of the ulna/interosseous membrane

Insertion: Ends at the dorsal expansion of the index finger

Action: Extension of the index finger

Intrinsic Muscles of the hand – Comes from the retinaculum
 Thenar Muscle group

Group of three muscles at the base of the thumb

Allowing the thumb to oppose other digits
 Used for grasping
 Hypothenar Muscle Group

Group of three muscles at the base of the little finger

Some movement of the little finger
 Interossei Muscle (7 – 3 palm, 4 dorsal)

Origin: Begins at a series of 7 muscles from the shaft of the
metacarpal


Insertion: Ends at the dorsal end of the four medial digits (4 dorsal interossei Muscles)

Action: Adduction/Abduction of these digits
Lumbricals

Origin: Begins at a series of 4 muscles from tendon of flexor Digitorum profundus

Insertion: Ends at the dorsal end of the medial 4 digits

Action: Extend the interphalangeal joint/flex the metacarpal/phalangeal joint.
Trunk Muscles

Spinal extensors – Occipital bone to the sacrum

Three different layers

Muscles that course vertically on the spines of the vertebrae

Used for spinal extension.

Sternocleidomastoid – neck muscle

Origin: Begins at the sternum and clavicle

Insertion: Ends at the mastoid process

Action: Responsible for rotation of the head and lateral flexion of head/neck

Diaphragm

Origin: Begins at the lumbar, inferior rib (Lateral attachment) and
xiphoid process

Insertion: Ends at the central tendon (migrates towards the middle)

Action: Responsible for expanding thorax in inspiration

Intercostals - Primary Function to keep space between ribs

External Intercostals – travels downwards from one rib to another
 Origin: Begins at the rib above
 Insertion: Ends at the rib below
 Action: Helps pull rib up during inspiration

Internal Intercostals – travels in opposite direction
 Origin: begins at the rib below
 Insertion: ends at the rib above
 Action: Pulls rib down during expiration

*Innermost intercostal are deep to the internal
intercostal*

External Abdominal Oblique

Origin: Begins at the outer surface of ribs – attachment with serratus anterior

Insertion: Ends at the Linea Alba, and at the bottom free edge of the aponeurosis (Inguinal ligament)
 Inguinal Ligament: Runs from the anterior & Superior iliac spine to the pubic tubercle

Action: Involved in trunk flexion/lateral rotation, increase
intra-abdominal pressure
 *Aponeurosis splits and goes above and below the
Rectus abdominalis*

Internal Abdominal Oblique – follows same direction as internal
intercostals

Origin: Begins at the lumbar fascia, inguinal ligament, iliac
crest and pubic tubercle

Insertion: Ends at the linea alba, inferior ribs

Action: Involved in trunk flexion/lateral rotation, increase
intra-abdominal pressure

Transverse Abdominalis – 3rd most deep, travels horizontally across

Origin: Begins at the lumbar fascia, iliac crest and inguinal
ligament

Insertion: Ends at the linea alba



Action: Used to increase intra-abdominal pressure
Rectus Abdominalis – Has bands that cause the muscle to split into smaller parts

Origin: Begins at the pubis bone

Insertion: Ends at the xiphoid process/edge of the lower ribs

Action: used for trunk flexion and to increase intra-abdominal pressure
*Valsava Effect*

Your lungs inflate as you take a deep breath.

As the epiglottis is closed, air in the lungs get trapped and the lungs press against the vertebral column –
stabilizing it

As the abdominal muscle/diaphragm contract, external pressure is applied, increasing the compression pressure

This increased pressure reduces, restricting the venous return to the heart

Causing temporary suspension of cerebral blood flow
 Leads to fainting, which removes the gravity pull on the cerebral blood flow enhancing cerebral blood
flow
Lower Torso


Most of the muscles are wrapped by the Fascia Latae (elastic wrapping around all muscles)
Direction of connective tissue are circular but the thickened fibers along the lateral side go in a vertical direction
(Iliotibial band)

Iliotibial band gives support to the lateral side of the knee due to its lateral attachment of the tibia
Hip Flexors

Iliopsoas Muscle – 2 of them

Psaos Major

Origin: Begins at the transverse process and bodies of the
lumbar vertebrae. Attaches with inigual ligament.

Insertion: Ends at the lesser trochanter of the femur

Action: used as hip flexor

Iliacus

Origin: Begins at the iliac fossa

Insertion: ends at the lesser trochanter

Action: Used as a hip flexor

Rectus Femoris – Quadriceps muscle
 Origin: Begins at the anterior/inferior angle of the iliac spine
 Insertion: Ends at the patella
 Action: used to flex the knee and hip

Sartorius
 Origin: Begins at the anterior/superior iliac spine – diagonally across the hip
joint.
 Insertion: Ends at the medial side of tibia
 Action: Used to flex the knee and hip and lateral rotation of the hip
Hip Flexors

Pectineus – smallest muscle at the top
 Origin: Begins at the pubis – rectineal line
 Insertion: Ends at the femur, pectineal (spiral) line – On the femur and travels
across and over
 Action: Used to adduct and flex the hip

Adductor Longus
 Origin: Begins near the pubis symphasis
 Insertion: Ends at the linea aspera of the femur – posterior surface

Action: Used to adduct/flex the hip

Adductor Brevis
 Origin: Begins at the pubis
 Insertion: Ends at the upper 3rd of linea aspera of femur – crosses on the back
 Action: Used to adduct and flex the hip.

Adductor Magnus
 Origin: Begins at the pubis, ramus of ischium and ischial tuberosity
 Insertion: Ends at the posterior shaft of femur
 Action: Used to adduct the hip, flex the hip (Anterior parts), and extend the hips (posterior parts)

Gracilis – travels medial side of the knee
 Origin: begins at the pubis
 Insertion: Ends at the medial side of the tibia
 Action: Used to adduct and flex the hip, and flex the knee
Hip Extensors

Gluteal Muscles – 3 of them

Gluteus Maximus – thickest and most superficial
 Origin: Begins at the sacrum/gluteal surface of
ilium
 Insertion: Ends at ¼ of gluteal tuberosity & ¾ of
ilitobial band
 Action: Powerful hip extensor & laterally rotates
the hip

Gluteus Medius – deep to the maximus
 Origin: Begins at the gluteal surface of ilium
 Insertion: Ends at the greater trochanter
 Action: Hip abductor/medial rotator

Gluteus Minimus – Most deep
 Origin: Begins at the gluteal surface of the ilium
 Insertion: Ends at the greater trochanter
 Action: Used to abduct/medially rotate the hip
**The gluteus Medius and minimus balance the body to maintain a uni-leg position. Example: Walking**
When walking the medius/minimus contract keeping the balance of the pelvic girdle

Hamstring Muscles – 3 of them
 Semimembranosus – Larger and inferior

Origin: Begins at the ischial tuberosity

Insertion: Ends at the medial side of tibia - attaches by
a membrane above the tendon

Action: Used to extend the hip/flex the knee
 Semitendinosus – Beneath the semimembranosus

Origin: Begins at the ischial tuberosity

Insertion: Ends at the Medial side of tibia - attached
by a tendon

Action: Used to extend the hip/flex the knee
 Biceps Femoris – Biarticulate Muscle

Origin: Long Head begins at the ischial tuberosity

Origin: Short Head begins at the posterior/lateral side
of the femur

Insertion: Ends at the head of the fibula – Long/Short
head fuse together

Action: Long head is used to extend the hip/flex knee,
short head flexes the knee

Tensor Fascia lata - When tightened it will give lateral support to the knee by putting tension on the Iliotibial Band
 Origin: Begins at the tuberosity on the ilium crest
 Insertion: Ends at the Iliotibial Band
 Action: Used to abduct/medially rotate the hip.

Hip Lateral Rotators – 6 of them in total

Action is to laterally rotate the hip and to turn the hip out

Attaches from the intertrochanteric crest
Hip Flexors/Knee Extensors

Quadriceps Muscles – 4 of them

Rectus Femoris
 Only part of the quadriceps group the flexes the hip

Vastus Medialis
 Origin: Begins at the medial part of the femur
 Insertion: Ends at the patella
 Action: Used in knee extension

Vastus Lateralis
 Origin: Begins at the lateral part of the femur
 Insertion: Ends at the patella
 Action: Used in knee extension

Vastus Intermedialis – Between the Lateralis and the medialis
 Origin: Begins at the anterior part of the femur
 Insertion: Ends at the patella
 Action: Used in knee extension
Knee Flexors – Septum divides the deep/superficial muscles






Gastrocnemius – Most superficial

Origin: Begins above the medial/lateral condyle of the femur

Insertion: Ends at the calcaneus – Achilles tendon

Action: used to flex the knee and for plantar flexion
Popliteus

Origin: Begins above the lateral condyle of the femur

Insertion: Ends at the upper posterior surface of the tibia

Action; used to laterally rotate the femur, and to unlock the knee
Plantaris – Deep

Origin: Begins under the gastrocnemius

Insertion: Ends at the calcaneus - Achilles tendon

Action: Used to flex the knee and for plantar flexion
Soleus – Deepest

Origin: Posterior of the fibular/tibia. Deep to the
gastrocnemius/Plantaris

Insertion: Ends at the calcaneus – Achilles tendon

Action: Used for plantar flexion
Ankle Plantar Flexors – 3 of them

All 3 parts are deep in the leg and are held by the retinaculum and
tendons are encased in synovial tubes or tunnels to prevent friction.

The Flexor Digitorum Longus and Hallucis Digitorum Longus cross each
other at the ankle joint
Tibialis Posterior

Origin: Begins posterior to the tibia, fibula and interosseous membrane

Insertion: Ends at the attachment on the plantar surface of the foot –
navicular bone tuberosity

Action: Used for inversion of ankle/plantar flexion
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Flexor Digitorum Longus – Digitorum = Digits of the feet
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Origin: Begins posterior to the tibia
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Insertion: Ends at the distal phalanges of the lateral four digits
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Action: Used for toe/plantar flexion
Flexor Hallucis Longus – Hallucis = the big toe
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Origin: Begins posterior to the fibula
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Insertion: Distal phalanx of the big toe
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Action: used for flexing the big toe
Ankle Dorsi Flexors
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Tibialis Anterior
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Origin: Begins at the anterior upper shaft of tibia
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Insertion: Ends at the 1st metatarsal base and medial cuneiform
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Action: Used for ankle inversion/dorsi flexion
Extensor Digitorum Longus
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Origin: Begins at the upper portion of the tibia and anterior shaft of the fibula
and interosseous membrane
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Insertion: Ends at the dorsal expansion on the digits
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Action: Used for dorsi flexion/toe extension
Extensor Hallucis Longus
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Origin: Begins at the anterior surface of the fibula and interosseous membrane
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Insertion: Ends at the distal phalanx of the big toe
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Action: Used for dorsi flexion/big toe extension.
Ankle Evertors/Plantar Flexors – tendons from the ankle pass through the
extensor retinaculum.
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Peroneus Longus
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Origin: begins at the lateral side of the fibula
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Insertion: Ends at the dorsal surface of the 1st metatarsal and
medial cuneiform
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Action: Used to evert the ankle and plantar flexion
Peroneus Brevis
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Origin: Begins at the lateral shaft of the fibula
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Insertion: Ends at the 5th metatarsal base
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Action: everts the ankle and used for plantar flexion
Ankle Evertors and Dorsi Flexors
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Peroneus Teritus
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Origin: Begins at the distal surface of fibula
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Insertion: Ends at the 5th digit expansion
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Action: Everts the ankle and used for plantar flexion
Toe Extensors
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Extensor Digitorum/Hallucis Brevis
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Origin: Begins at the dorsal surface of calcaneus
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Insertion: Extensor Digitorum: ends at one tendon to the 2nd/3rd/4th
digits
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Insertion: Hallucis Brevis: ends at one tendon to the 1st digit
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Action: Helps extend toes
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Foot Intrinsic Muscles – arranged in layers
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work together to produce movement
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has a retinaculum to align the tendons properly