The Muscular System

Muscle Attachment Sites

Muscle exerts force on tendons, which in turn pull on bones or other structures.

When a muscle contracts, it pulls one of the articulating bones toward the other.

Muscle Attachment Sites: Origin & Insertion

Origin – the site of a muscle’s attachment to the more stationary bone.

Insertion – the site of a muscle’s attachment to the more movable bone.

Often, the origin is proximal to the insertion. Belly – the fleshy part of the muscle between

the tendons of the origin and insertion.

Tenosynovitis

Commonly known as tendinitis. Painful inflammation of the tendons, tendon

sheaths, and synovial membranes of the joints.

Trauma, strain, excessive exercise, chronic, repetitive motions can all cause tenosynovitis.

Lever Systems & Leverage

A lever is a rigid structure that can move around a fixed point called a fulcrum.

Two forces act upon a lever: Effort – causes movement. Load (resistance) – opposes movement.

Lever Systems & Leverage

Levers produce trade-offs between effort and the speed and range of motion.

Mechanical advantage (leverage) – a smaller effort can move a heavier load – the effort must move a greater distance.

Mechanical disadvantage – a larger effort moves a lighter load – the effort must move a shorter distance and slower than the load.

Types of Levers

First-class levers. The fulcrum is between the effort and the load. Scissors and seesaws are examples. It can produce either a mechanical advantage or disadvantage

depending upon whether the effort or load is placed closer to the fulcrum.

If an effort is placed farther from the fulcrum than the load, a heavy load can be moved, but not fast or far.

If an effort is placed closer to the fulcrum than the load, only a lighter load can be moved, but it moves far and fast.

Raising the head at the atlanto-occipital joint.

Types of Levers

Second-class levers. The load is between the fulcrum and the effort. An example is a wheelbarrow. Always produces a mechanical advantage

because the load is always closer to the fulcrum than the effort.

None present in the human body.

Types of Levers

Third-class levers. The effort is between the fulcrum and the load. An example is a forceps. Always produces a mechanical disadvantage

because the effort is always closer to the fulcrum than the load.

This arrangement favors speed and range of motion over force.

Effects of Fascicle Arrangement

Within a fascicle, all muscles are parallel to one another.

The fascicles may form patterns with respect to the tendon: Parallel. Fusiform (cigar shaped). Circular. Triangular. Pennate (feather shaped).

Effects of Fascicle Arrangement

Fascicular arrangement affects a muscle’s power and range of motion.

The longer the muscles in a fiber, the greater the range of motion they can produce.

The power of a muscle depends upon it’s cross-sectional area (a short muscle fiber can contract as powerfully as a long one).

Coordination Within Muscle Groups

Movements are typically the result of several skeletal muscles acting as a group.

Most skeletal muscles are arranged in opposing (antagonistic) pairs at joints: Flexors – extensors, abductors – adductors, etc.

One muscle is called the prime mover (agonist) which contracts to cause an action and the other muscle is called the antagonist which stretches and yields to the effects of the prime mover.

Coordination Within Muscle Groups

Synergists work with agonists to stabilize intermediate joints and assist the prime mover.

Fixators stabilize the origin of the prime mover so that the prime mover can operate more efficiently.

In limbs, a compartment is a group of skeletal muscles, and their associated blood vessels and nerves, that have a common function. I.E. In the upper limbs with have flexor compartments

and extensor compartments.

Benefits of Stretching

Improved physical performance – greater R.O.M. Decreased risk of injury – decreases the resistance

in tissues. Reduced muscle soreness. Improved posture – stretching helps realign soft

tissues. Muscles should be stretched at a point of slight

discomfort (not pain) for 15-30 seconds.

Muscles of Facial Expression

Scalp muscles Occipitofrontalis

Frontal bellyOccipital belly

Muscles of Facial Expression

Mouth muscles Orbicularis oris Zygomaticus major Zygomaticus minor Levator labii superioris Depressor labii inferioris Depressor anguli oris Buccinator

Muscles of Facial Expression

Neck muscle Platysma

Orbit and eyebrow muscles Orbicularis Oculi Corrugator Supercilii Levator palpebrae superioris

Frontalis

Origin – Epicranial aponeurosis Insertion – skin above the eye Action – draws skin anteriorly, raises

eyebrows, and wrinkles skin of the forehead

Occipitalis

Origin – occipital bone and mastoid process of the temporal bone

Insertion – epicranial aponeurosis Action – draws scalp posteriorly

Orbicularis Oris

Origin – surrounding the opening of the mouth

Insertion – skin at the corner of the mouth Action – closes and protrudes lips,

compresses lips against the teeth, and shapes lips during speech

Buccinator

Origin – maxilla and mandible Insertion – orbicularis oris Action – draws the angle of the mouth

laterally and inferiorly as in opening the mouth

Platysma

Origin – fascia over deltoid and pectoralis major muscles

Insertion – mandible, muscles around the angle of the mouth and the skin of the lower face

Action – draws the outer part of the lower lip inferiorly and posteriorly as in pouting and depresses the mandible

Orbicularis Oculi

Origin – medial wall of orbit Insertion – circular path around orbit Action – closes eye

Bell’s Palsy (Facial Paralysis)

Unilateral paralysis of the muscles of facial expression.

Due to damage or disease of the facial nerve (cranial nerve VII).

The causes is unknown; However, inflammation of the facial nerve or infection by herpes simplex are suggested causes.

Bell’s Palsy (Facial Paralysis)

The person cannot wrinkle the forehead, close the eye, or pucker the lips on the affected side.

Difficulty in swallowing and drooling often occur.

80% recover within a few weeks to a few months; However, for some the paralysis is permanent.

Muscles That Move the Eyeballs – Extrinsic Eye

Muscles Superior Rectus Inferior Rectus Lateral Rectus Medial Rectus Superior oblique Inferior oblique

Strabismus

A condition in which the eyes are not properly aligned.

A lesion of the oculomotor nerve (cranial nerve III) or the abducens nerve (cranial nerve VI).

Muscles That Move the Mandible

Masseter Temporalis Medial Pterygoid Lateral Pterygoid

Masseter

Origin – maxilla and zygomatic arch Insertion – angle and ramus of mandible Action – elevates mandible and retracts

mandible (closes mouth)

Temporalis

Origin – temporal bone Insertion – coronoid process and ramus of

mandible Action – elevates and protracts mandible and

moves mandible from side to side

Muscle That Move The Tongue

Genioglossus Styloglossus Palatoglossus Hyoglossus

Muscles of the Anterior Neck

Suprahyoid muscles Digastric Stylohyoid Mylohyoid Geniohyoid

Muscles of the Anterior Neck

Infrahyoid muscles Omohyoid Sternohyoid Sternothyroid Thyrohyoid

Muscles That Move the Head

Sternocleidomastoid Semispinalis Capitis Splenius Capitus Longissimus Capitis

Sternocleidomastoid

Origin – sternum and clavicle Insertion – mastoid process of the temporal bone Action –

Acting together (bilaterally), they flex the cervical portion of the vertebral column, extend the head, and elevate the sternum during forced inhalation

Acting singly (unilaterally), laterally flexes head towards and rotates head away from the side of the contracting muscle

Muscles That Act on the Abdominal Wall

Rectus Abdominus External oblique Internal oblique Transversus Abdominus Quadratus Lumborum

Rectus Abdominus

Origin – pubic crest and pubic symphisis. Insertion – cartilage of the 5th to 7th ribs and

xiphoid process. Action – flexes vertebral column,

compresses the abdomen to aid in defecation, urination, forced exhalation and childbirth.

External Oblique

Origin – inferior eight ribs. Insertion – iliac crest and linea alba. Action –.

Acting together (bilaterally) they compress the abdomen and flex the vertebral column.

Acting singly (unilaterally), laterally flexes the vertebral column and rotates the vertebral column.

Muscles Used in Breathing

Diaphragm External intercostals Internal intercostals

Muscles of the Pelvic Floor

Levator ani Pubococcygeus Iliococcygeus

Coccygeus

Muscles of the Perineum

Superficial Perineal muscles Superficial transverse perineal Bulbospongiosis

Deep Perineal muscles Deep transverse perineal External urethral sphincter External anal sphincter

Muscles That Move the Pectoral Girdle

Anterior thoracic muscles Subclavius Pectoralis minor Serratus anterior

Posterior thoracic muscles Trapezius Levator scapulae Rhomboid major Rhomboid minor

Muscles That Move the Humerus

Axial muscles that move the Humerus Pectoralis major Latissimus dorsi

Muscles That Move the Humerus

Scapular muscles that move the Humerus Deltoid Subscapularis Supraspinatous Infraspinatous Teres major Teres minor coracobrachialis

Pectoralis Major

Origin – clavicle, sternum, and costal cartilages of 2nd to 6th ribs

Insertion – greater tubercle of the humerus Action –

As a whole, adducts and medially rotates arm at the shoulder joint

Clavicular head alone flexes arm Sternocostal head alone extends the arm

Latissimus Dorsi

Origin – spines of the inferior six thoracic vertebrae, lumbar vertebrae, crests of sacrum and ilum, and inferior four ribs

Insertion – intertubercular sulcus of humerus Action – extends, adducts, and medially

rotates the arm, draws arm inferiorly and posteriorly

Deltoid

Origin – acromial extremity of clavicle (anterior fibers), acromion of scapula (lateral fibers), and spine of scapula (posterior fibers)

Insertion – deltoid tuberosity of humerus Action –

Lateral fibers – abduct arm Anterior fibers – flex and medially rotate arm Posterior fibers – extend and laterally rotate arm

Muscles That Move the Radius and Ulna

Forearm flexors Biceps brachii Brachialis Brachioradialis

Forearm extensors Triceps brachii Anconeus

Muscles That Move the Radius and Ulna

Forearm Pronators Pronator teres Pronator quadratus

Forearm Supinator Supinator

Biceps Brachii

Origin – Long head – tubercle above glenoid cavity of

scapula Short head – coracoid process of scapula

Insertion – radial tuberosity of radius Action – flexes forearm at elbow, supinates

forearm, and flexes arm at shoulder

Brachialis

Origin – distal, anterior surface of humerus Insertion – ulnar tuberosity and coronoid

process of ulna Action – flexes forearm at elbow

Brachioradialis

Origin – lateral border of distal end of humerus

Insertion – superior to styloid process of radius

Action – flexes forearm at elbow, supinates and pronates forearm to neutral position

Triceps Brachii

Origin – Infraglenoid tubercle of scapula, posterior surface of humerus

Insertion – olecranon of ulna Action – extends forearm at elbow, extends

arm at shoulder

Pronator Teres

Origin – medial epicondyle of humerus and coronoid process of ulna

Insertion – midlateral surface of radius Action – pronates forearm at radioulnar

joints and weakly flexes forearm at elbow

Supinator

Origin – lateral epicondyle of humerus and ridge near radial notch of ulna

Insertion – lateral surface of proximal one third radius

Action – supinates forearm at radioulnar joints

Muscles That Move the Wrist, Hand, Thumb, and Fingers

Superficial anterior (flexor) compartment of the forearm Flexor carpi radialis Palmaris longus Flexor carpi ulnaris Flexor digitorum superficialis

Deep anterior (flexor) compartment of the forearm Flexor pollicus longus Flexor digitorum profundus

Muscles That Move the Wrist, Hand, Thumb, and Fingers

Superficial posterior (extensor) compartment of the forearm Extensor carpi radialis longus Extensor carpi radialis brevis Extensor digitorum Extensor digiti minimi Extensor carpi ulnaris

Muscles That Move the Wrist, Hand, Thumb, and Fingers

Deep posterior (extensor) compartment of the forearm Abductor pollicis brevis Extensor pollicis longus Extensor indicis

Flexor Carpi Radialis

Origin – medial epicondyle of humerus. Insertion – 2nd & 3rd metacarpals. Action – flexes and abducts hand (radial

deviation) at wrist.

Flexor Carpi Ulnaris

Origin – medial epicondyle of humerus and superior posterior border of ulna

Insertion – pisiform, hamate, and base of 5th metacarpal

Action – flexes and adducts (ulnar deviation) at wrist.

Extensor Digitorium

Origin – lateral epicondyle of humerus Insertion – distal and middle phalanges of

each finger Action – extends distal and middle phalanges

of each finger and extends the hand at the wrist

Extensor Carpi Ulnaris

Origin – lateral epicondyle of humerus and posterior border of ulna

Insertion – 5th metacarpal Action – extends and adducts hand at wrist.

Palmaris Longus

Origin – medial epicondyle of humerus Insertion – flexor retinaculum and palmar

aponeurosis (deep fascia in center of palm) Action – weakly flexes hand at wrist joint.

Intrinsic Muscles of the Hand

Thenar (lateral aspect of the palm) Abductor pollicis Opponens pollicis Flexor pollicis brevis Adductor pollicis

Intrinsic Muscles of the Hand

Hypothenar (medial aspect of the palm) Abductor digiti minimi Flexor digiti minimi brevis Opponens digiti minimi

Intermediate (Midpalmar) Lumbricals Palmar interossei Dorsal interossei

Carpal Tunnel Syndrome

The carpal tunnel is a narrow passageway formed anterior by the flexor retinaculum and posteriorly by the carpal bones.

The median nerve and flexor tendons pass through. They are vulnerable to compression, which results

in pain, numbness, and tingling in the fingers. It is caused by inflammation of the tendon sheaths,

fluid retention, and repetitive activities involving flexion at the wrist.

Muscles That Move the Vertebral Column

Splenius Splenius capitis Splenius cervicis

Erector Spinae Iliocostalis group (lateral) Longissussumus group (intermediate) Spinalis group (medial)

Muscles That Move the Vertebral Column

Transversospinales Seminspinalis Multifidus Rotatores

Segmental Interspinales Intertransversarii

Scalenes

Muscles That Move the Femur

Psoas major Iliacus Gluteus maximus Gluteus medius Gluteus minimus Tensor fasciae latae Piriformis

Muscles That Move the Femur

Obturator internus Obturator externus Superior gemellus Quadratus femoris Adductor longus Adductor brevis Adductor magnus Pectineus

Gluteus Maximus

Origin – iliac crest, sacrum, coccyx. Insertion – iliotibial tract of TFL and under

the greater trochanter of the femur. Action – extends thigh at hip and externally

rotates thigh.

Tensor Fasciae Latae (TFL)

Origin – iliac crest. Insertion – tibia by way of the iliotibial tract. Action – flexes and abducts thigh at hip

joint.

Adductor Longus

Origin – pubic crest and pubic symphysis. Insertion – linea aspera of femur. Action – adducts and flexes thigh at hip joint

and medially rotates thigh.

Adductor Magnus

Origin – inferior ramus of pubis and ischium to ischial tuberosity.

Insertion – linea aspera of femur. Action – adducts thigh at hip and medially

rotates thigh. The anterior part flexes the thigh and the posterior part extends the thigh.

Muscles That Act on the Femur, Tibia, and Fibula

Medial (adductor) compartment of the thigh Adductor magnus Adductor longus Adductor brevis Pectineus Gracilis

Muscles That Act on the Femur, Tibia, and Fibula

Anterior (extensor) compartment of the thigh Quadriceps femoris

Rectus femorisVastus lateralisVastus medialisVastus intermedius

Sartorius

Muscles That Act on the Femur, Tibia, and Fibula

Posterior (flexor) compartment of the thigh Hamstrings

Biceps femorisSemitendinosusSemimenbranosus

Gracilis

Origin – body and inferior ramus of pubis. Insertion – medial surface of body of tibia. Action – adducts thigh at hip, medially

rotates thigh and flexes leg at knee.

Rectus Femoris

Origin – anterior inferior iliac spine (ASIS). Insertion – patella via quadriceps tendon

then tibial tuberosity. Action – extend the leg at the knee joint and

flexes the thigh at the hip.

Vastus Lateralis

Origin – greater trochanter and linea aspera of femur.

Insertion – patella via quadriceps tendon then tibial tuberosity.

Action – extend the leg at the knee joint and flexes the thigh at the hip.

Vastus Medialis

Origin – linea aspera of femur. Insertion – patella via quadriceps tendon

then tibial tuberosity. Action – extend the leg at the knee joint and

flexes the thigh at the hip.

Vastus Intermedius

Origin – anterior and lateral surfaces of body of femur.

Insertion – patella via quadriceps tendon then tibial tuberosity.

Action – extend the leg at the knee joint and flexes the thigh at the hip.

Sartorius

Origin – ASIS. Insertion – medial surface of body of tibia. Action – flexes leg at knee, flexes, abducts,

and externally rotates thigh at hip. “Tailor’s muscle”.

Biceps Femoris

Origin –. Long head – ischial tiberosity. Short head – linea aspera of femur.

Insertion – head of fibula and lateral condyle of tibia.

Action – flexes leg at knee joint and extends thigh at hip.

Semitendinosus

Origin – ischial tiberosity. Insertion – proximal part of medial surface

of shaft of tibia. Action – flexes leg at knee and extends thigh

at hip.

Seminmembranosus

Origin – ischial tiberosity. Insertion – medial condyle of tibia. Action – flexes leg at knee and extends thigh

at hip.

Muscles That Move the Foot and Toes

Anterior compartment of the leg Tibialis anterior Extensor hallucis longus Extensor digitorum longus Fibularis (peroneus) tertius

Lateral (fibular) compartment of the leg Fibularis (peroneus) longus Fibularis (peroneus) brevis

Muscles That Move the Foot and Toes

Superficial posterior compartment of the leg Gastrocnemius Soleus Plantaris

Deep posterior compartment of the leg Popliteus Tibialis posterior Flexor digitorum longus Flexor hallucis longus

Tibialis Anterior

Origin – lateral condyle and body of tibia, interosseous membrane.

Insertion – 1st metatarsal and first (medial) cuneiform.

Action – dorsiflexes foot at ankle and inverts foot at intertarsal joints.

Extensor Digitorium Longus

Origin – lateral condyle of tibia, anterior surface of fibula and interosseous membrane.

Insertion – base of 5th metatarsal. Action – dorsiflexes foot at ankle and everts

foot.

Peronius Longus

Origin – head and body of fibula and lateral condyle of tibia.

Insertion – 1st metatarsal and 1st cuneiform. Action – plantar flexes foot and everts foot.

Gastrocnemius

Origin – lateral and medial condyles of femur and capsule of knee.

Insertion – calcaneous by way of calcaneal (Achille’s) tendon.

Action – plantar flexes foot at ankle and flexes leg at knee.

Soleus

Origin – head of fibula and medial border of tibia.

Insertion – calcaneous by way of calcaneal (Achille’s) tendon.

Action – plantar flexes foot at ankle.

Flexor Digitorum Longus

Origin – posterior surface of tibia. Insertion – distal phalanges of toes 2-5. Action – plantar flexes foot and flexes distal

and middle phalanges of toes 2-5.

Tibialis Posterior

Origin – tibia, fibula, and interosseus membrane.

Insertion – 2nd, 3rd, & 4th metatarsals, navicular, all cuneiforms, and cuboid.

Action – plantar flexes foot at ankle and inverts foot.

Flexor Hallucis Longus

Origin – inferior two-thirds of fibula. Insertion – distal phalanx of great toe. Action – plantar flexes foot at ankle, flexes

great toe.

Shinsplint Syndrome

Pain or soreness along the tibia, specifically the medial, distal two-thirds.

Caused by tendinitis of the anterior compartment muscles, especially tibialis anterior muscle, inflammation of the periosteum around the tibia or stress fractures of the tibia.

Running on hard surfaces with poorly conditioned muscles, poor support shoes, etc. Contributes to this condition.

Intrinsic Muscles of the Foot

Dorsal Extensor digitorum brevis

Intrinsic Muscles of the Foot

Plantar 1st layer (most superficial)

Abductor hallucisFlexor digitorum brevisAbductor digiti minimi

2nd layerQuadratus plantaeLumbricals

Intrinsic Muscles of the Foot

Plantar 3rd layer

Flexor hallucis brevisAdductor hallucisFlexor digiti minimi

4th layer (deepest)Dorsal interosseiPlantar interossei

Plantar Fasciitis

Otherwise know as painful heel syndrome. Inflammatory reaction due to chronic irritation of

the plantar aponeurosis at its origin on the calcaneous.

The most common cause of heel pain in runners. Tx. - Strip out the plantar aponeurosis with a tennis

ball or golf ball.

Tendons

Patellar tendon & ligament Calcaneal or Achille’s tendon