Chapter 11 The Muscular System

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Chapter 11The Muscular System

• Skeletal muscle major groupings
• How movements occur at specific joints
• Learn the origin, insertion, function and
  innervation of all major muscles
• Important to allied health care and physical
  rehabilitation students

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Muscle Attachment SitesOrigin and Insertion

• Skeletal muscles shorten pull on the bones they
  are attached to
• Origin is the bone that does not move when muscle
  shortens (normally proximal)
• Insertion is the movable bone (some 2 joint
  muscles)
• Fleshy portion of the muscle in between
  attachment sites belly

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Tenosynovitis

• Inflammation of tendon and associated connective
  tissues at certain joints
• wrist, elbows and shoulder commonly affected
• Pain associated with movement
• Causes
• trauma, strain or excessive exercise

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Lever Systems and Leverage

• Muscle acts on rigid rod (bone)that moves around
  a fixed point called a fulcrum
• Resistance is weight of bodypart perhaps an
  object
• Effort or load is work doneby muscle contraction
• Mechanical advantage
• the muscle whose attachment is farther from the
  joint will produce the most force
• the muscle attaching closer to the joint has the
  greater range of motion and the faster the speed
  it can produce

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Fascicle Arrangements

• A contracting muscle shortens to about 70 of its
  length
• Fascicular arrangement represents a compromise
  between force of contraction (power) and range of
  motion
• muscles with longer fibers have a greater range
  of motion
• a short fiber can contract as forcefully as a
  long one.

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Coordination Within Muscle Groups

• Most movement is the result of several muscle
  working at the same time
• Most muscles are arranged in opposing pairs at
  joints
• prime mover or agonist contracts to cause the
  desired action
• antagonist stretches and yields to prime mover
• synergists contract to stabilize nearby joints
• fixators stabilize the origin of the prime mover
• scapula held steady so deltoid can raise arm

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How Skeletal Muscle are Named

• Direction the muscle fibers run
• Size, shape, action, number of origins or
  locations
• Examples from Table 11.2
• triceps brachii -- 3 sites of origin
• quadratus femoris -- square shape
• serratus anterior -- saw-toothed edge

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Muscles of Facial Expression

• Arise from skull insert onto skin
• Encircle eyes, nose mouth
• Express emotions
• Facial Nerve (VII)
• Bells palsy facial paralysis due

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Muscles of Facial Expression

• Orbicularis oculi closes the eye
• Levator palpebrae superioris opens the eye
• Orbicularis oris puckers the mouth
• Buccinator forms the muscular portion of the
  cheek assists in whistling, blowing, sucking
  chewing

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Muscles that Move the Mandible

• Masseter, temporalis pterygoids
• Arise from skull insert on mandible
• Cranial nerve V (trigeminal nerve)
• Protracts, elevates or retracts mandible
• Temporalis Masseter elevate the mandible
  (biting)
• temporalis retracts

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Jaw Muscles -- Deep Dissection

• Lateral pterygoid protracts mandible
• sphenoid bone to condyle of mandible
• Medial pterygoid elevates protracts mandible
• sphenoid bone to angle of mandible
• Together move jaw side to side to grind food.

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Muscles that Move the Tongue

• 4 extrinsic mm ariseelsewhere, but insertinto
  tongue
• Genioglossus
• from inside tip of mandible
• Styloglossus
• from styloid process
• Palatoglossus
• from hard palate
• Hyoglossus
• from hyoid bone
• Together move tongue in various directions
• Intubation is necessary during anesthesia since
  Genioglossus relaxes tongue falls posteriorly
  blocking airway

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Muscles of the Floor of the Oral Cavity

• Suprahyoid muscles lie superior to hyoid bone.
• Digastric m. extends from mandible to mastoid
  process
• used to open the mouth
• Mylohyoid m. extends from hyoid to mandible
• supports floor of mouth elevates hyoid bone
  during swallowing
• Stylohyoid Geniohyoid elevate the hyoid during
  swallowing

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Muscles that Move the Head

• Sternocleidomastoid muscle
• arises from sternum clavicle inserts onto
  mastoid process of skull
• innervated by cranial nerve XI (spinal accessory)
• contraction of both flexes the cervical vertebrae
  extends head
• contraction of one, laterally flexes the neck and
  rotates face in opposite direction

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Muscles of Abdominal Wall

• Notice 4 layers of muscle in the abdominal wall

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Muscles of Abdominal Wall

• 4 pairs of sheetlike muscles
• rectus abdominis vertically oriented
• external internal obliques and transverses
  abdominis
• wrap around body to form anterior body wall
• form rectus sheath and linea alba
• Inguinal ligament from anterior superior iliac
  spine to upper surface of body of pubis
• Inguinal canal passageway from pelvis through
  body wall musculature opening seen as superficial
  inguinal ring
• Inguinal hernia rupture or separation of
  abdominal wall allowing protrusion of part of the
  small intestine (more common in males)

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Muscles Used in Breathing

• Breathing requires a change in size of the
  thorax
• During inspiration, thoracic cavity increases in
  size
• external intercostal lift the ribs
• diaphragm contracts dome is flattened
• During expiration, thoracic cavity decreases in
  size
• internal intercostal mm used in forced expiration
• Diaphragm is innervated by phrenic nerve (C3-C5)
  but intercostals innervated by thoracic spinal
  nerves (T2-T12)

Quadratus lumborum fills in space between 12th
rib iliac crest to create posterior body wall
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Stabilizing the Pectoral Girdle

• Anterior thoracic muscles
• Subclavius extends from 1st rib to clavicle
• Pectoralis minor extends from ribs to coracoid
  process
• Serratus anterior extends from ribs to inner
  surface of scapula
• Posterior thoracic muscle
• Trapezius extends from skull vertebrae to
  clavicle scapula
• Levator scapulae extends from cervical vertebrae
  to scapula
• Rhomboideus extends from thoracic vertebrae to
  vertebral border of scapula

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Axial Muscles that Move the Arm

• Pectoralis major Latissimus dorsi extend from
  body wall to humerus.

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Muscles that Move the Arm

• Deltoid arises from acromion spine of scapula
  inserts on arm
• abducts, flexes extends arm
• Rotator cuff muscles extend from scapula
  posterior to shoulder joint to attach to the
  humerus
• supraspinatus infraspinatus above below
  spine of scapula
• subscapularis on inner surface of scapula

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Flexors of the Forearm (elbow)

• Cross anterior surface of elbow joint form
  flexor muscle compartment
• Biceps brachii
• scapula to radial tuberosity
• flexes shoulder and elbow supinates hand
• Brachialis
• humerus to ulna
• flexion of elbow
• Brachioradialis
• humerus to radius
• flexes elbow

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Extensors of the Forearm (elbow)

• Cross posterior surface of elbow joint forms
  extensor muscle compartment
• Triceps brachii
• long head arises scapula
• medial lateral heads from humerus
• inserts on ulna
• extends elbow shoulder joints
• Anconeus
• assists triceps brachii in extending the elbow

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Cross-Section Through Forearm

• If I am looking down onto this section is it from
  right or left arm?

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Muscle that Pronate Flex

• Pronator teres
• medial epicondyle to radius so contraction turns
  palm of hand down towards floor
• Flexor carpi muscles
• radialis
• ulnaris
• Flexor digitorum muscles
• superficialis
• profundus
• Flexor pollicis

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Muscles that Supinate Extend

• Supinator
• lateral epicondyle of humerus to radius
• supinates hand
• Extensors of wrist and fingers
• extensor carpi
• extensor digitorum
• extensor pollicis
• extensor indicis

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Retinaculum

• Tough connective tissue band that helps hold
  tendons in place
• Extensor Flexor retinaculum cross wrist region
  attaching from bone to bone (carpal tunnel
  syndrome painful compression of median nerve
  due to narrowing passageway under flexor
  retinaculum

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Intrinsic Muscles of the Hand

• Origins insertions are within the hand
• Help move the digits
• Thenar muscles move the thumb
• Hypothenar muscles move the little finger
• Opposition, flexion, extension, abduction
  adduction

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Muscles that Move the Vertebrae

• Quite complex due to overlap
• Erector spinae fibers run longitudinally
• 3 groupings
• spinalis
• iliocostalis
• longissimus
• extend vertebral column
• Smaller, deeper muscles
• transversospinalis group
• semispinalis, multifidis rotatores
• run from transverse process to dorsal spine of
  vertebrae above help rotate vertebrae

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Scalene Muscle Group

• Attach cervical vertebrae to uppermost ribs
• Flex, laterally flex rotate the head

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Muscles Crossing the Hip Joint

• Iliopsoas flexes hip joint
• arises lumbar vertebrae ilium
• inserts on lesser trochanter
• Quadriceps femoris has 4 heads
• Rectus femoris crosses hip
• 3 heads arise from femur
• all act to extend the knee
• Adductor muscles
• bring legs together
• cross hip joint medially
• see next picture
• Pulled groin muscle
• result of quick sprint activity
• stretching or tearing of iliopsoas or adductor
  muscle

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Adductor Muscles of the Thigh

• Adductor group of muscle extends from pelvis to
  linea aspera on posterior surface of femur
• pectineus
• adductor longus
• adductor brevis
• gracilis
• adductor magnus (hip extensor)

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Muscles of the Butt Thigh

• Gluteus muscles
• maximus, medius minimus
• maximus extends hip
• medius minimus abduct
• Deeper muscles laterally rotate femur
• Hamstring muscles
• semimembranosus (medial)
• semitendinosus (medial)
• biceps femoris (lateral)
• extend hip flex knee
• Pulled hamstring
• tear of origin of muscles from ischial tuberosity

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Cross-Section through Thigh

• 3 compartments of muscle with unique innervation
• anterior compartment is quadriceps femoris
  innervated by femoral nerve
• medial compartment is adductors innervated by
  obturator nerve
• posterior compartment is hamstrings innervated by
  sciatic nerve

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Muscles of the Calf (posterior leg)

• 3 muscles insert onto calcaneus
• gastrocnemius arises femur
• flexes knee and ankle
• plantaris soleus arise from leg
• flexes ankle
• Deeper mm arise from tibia or fibula
• cross ankle joint to insert into foot
• tibialis posterior
• flexor digitorum longus
• flexor hallucis longus
• flexing ankle joint toes

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Muscles of the Leg and Foot

• Anterior compartment of leg
• extensors of ankle toes
• tibialis anterior
• extensor digitorum longus
• extensor hallucis longus
• tendons pass under retinaculum
• Shinsplits syndrome
• pain or soreness on anterior tibia
• running on hard surfaces
• Lateral compartment of leg
• peroneus mm plantarflex the foot
• tendons pass posteriorly to axis of ankle joint
  and into plantar foot

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Muscles of the Plantar Foot

• Intrinsic muscles
• arise insert in foot
• 4 layers of muscles
• get shorter as go into deeper layers
• Flex, adduct abduct toes
• Digiti minimi muscles move little toe
• Hallucis muscles move big toe
• Plantar fasciitis (painful heel syndrome) chronic
  irritation of plantar aponeurosis at calcaneus
• improper shoes weight gain