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 belly  Occipital 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)   Difficulty in swallowing and drooling often occur.

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

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 5 th to 7 th 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 2 nd to 6 th 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 – 2 nd & 3 rd 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 5 th 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 – 5 th 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 femoris  Vastus lateralis  Vastus medialis  Vastus intermedius  Sartorius

Muscles That Act on the Femur, Tibia, and Fibula  Posterior (flexor) compartment of the thigh  Hamstrings  Biceps femoris  Semitendinosus  Semimenbranosus

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 – 1 st 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 5 th metatarsal.

 Action – dorsiflexes foot at ankle and everts foot.

Peronius Longus  Origin – head and body of fibula and lateral condyle of tibia.

 Insertion – 1 st metatarsal and 1 st 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 – 2 nd , 3 rd , & 4 th 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  1 st layer (most superficial)  Abductor hallucis  Flexor digitorum brevis  Abductor digiti minimi  2 nd layer  Quadratus plantae  Lumbricals

Intrinsic Muscles of the Foot  Plantar  3 rd layer  Flexor hallucis brevis  Adductor hallucis  Flexor digiti minimi  4 th layer (deepest)  Dorsal interossei  Plantar 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