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Muscular system:- PDF/PPT


The Muscular System

Specialized tissue that enable the
body and its parts to move.
Anterior View
Posterior View
 How many muscles are there in the human body?
 Answer: 640 Muscles
 The muscles make up about 40 % of the body mass.

 What is the longest muscle in the body?
 Answer: The Sartorius
 The Sartorius runs from the outside of the hip, down and across to the
inside of the knee. It twists and pulls the thigh outwards.

 What is the smallest muscle in the body?
 Answer: The Stapedius
 The Stapedius is located deep in the ear. It is only 5mm long and thinner
than cotton thread. It is involved in hearing.

 What is the biggest muscle in the body?
 Answer: The Gluteus Maximus
 The Gluteus Maximus is located in the buttock. It pulls the leg
backwards powerfully for walking and running.
There are about 60 muscles in the face.
Smiling is easier than frowning.
It takes 20 muscles to smile and over 40 to frown.

Smile and make someone happy.
Functions of the Muscles
 Movement
 Maintenance of posture and muscle
 Heat production
 Protects the bones and internal
Muscle Classification
 Functionally
 Voluntarily – can be moved at will
 Involuntarily – can’t be moved

 Structurally
 Striated – have stripes across the fiber
 Smooth – no striations
The 3 Types of Muscles

3 Types of Muscles

Skeletal Muscle Smooth Muscle Cardiac Muscle
Three types of muscle

Skeletal Cardiac Smooth
Classification of muscle
Voluntary Involuntary

Skeletal Cardiac Smooth

Limbs Heart Viscera

Striated Non-striated

Note: Control, Location and Structure
Smooth Muscle

 Fibers are thin
and spindle
 No striations
 Single nuclei
 Involuntary
 Contracts slowly
Smooth Muscle
 They fatigue… but very slowly
 Found in the circulatory
 Lining of the blood vessels
 Helps in the circulation of the
 Found in the digestive system
 Esophagus, stomach, intestine
 Controls digestion
 Found in the respiratory
 Controls breathing
 Found in the urinary system
 Urinary bladder
 Controls urination
Cardiac Muscle
 Cells are branched
and appear fused
with one another
 Has striations
 Each cell has a
central nuclei
 Involuntary
Cardiac Muscle
 Found ONLY in the heart
 Contractions of the heart
muscles pump blood
throughout the body and
account for the heartbeat.
 Healthy cardiac muscle
NEVER fatigues  or else…
Skeletal Muscle

Fibers are long and
            Has many nuclei
            Has striations
                Have alternating
                 dark and light bands
            Voluntary
         Skeletal Muscle
 Attached to skeleton by
 Causes movement of bones
  at the joints.
 And yes… they do fatigue
 Muscle fatigue activity 
  what substance forms
  causing muscle fatigue???
Functions of Skeletal Muscle
   Movement – muscle move bones by pulling
    not pushing.
     Synergists – any movement is generally
      accomplished by more than one muscle.
      All of the muscles responsible for the
      movement are synergists.
     The one that is most responsible for the
      movement is the Prime Mover (agonist).
    Functions of Skeletal Muscle
   Movement
       Antagonists – muscles and muscle groups
        usually work in pairs
        – example the biceps flex your arm and its
        partner the triceps extend your arm. The two
        muscles are antagonists, i.e. cause opposite
        – when one contracts the other relaxes.
       Levators – muscle that raise a body part.
Functions of Skeletal Muscle
   Maintenance of posture or muscle tone
     We are able to maintain our body position
      because of tonic contractions in our
      skeletal muscles. These contractions
      don’t produce movement yet hold our
      muscles in position.

 Heat production – contraction of muscles
produces most of the heat required to
maintain body temperature.
Structure of Skeletal Muscle
 Composed of striated muscle cells
(=muscle fibers) and connective
 Most muscles attach to 2 bones that
have a moveable joint between them.
 The attachment to the bone that does not move is
the origin.
 The attachment to the bone that moves is the
 Tendons anchor muscle firmly to bones.
Tendons are made of dense fibrous
connective tissue.
 Ligaments connect bone to bone at a
Structure of Skeletal Muscle
 Bursae – small fluid filled sacs that lie
between some tendons and the bones
beneath them. They are made of
connective tissue and are lined with
synovial membrane that secretes synovial

Nervous System and Muscles
 Contribution of the nervous
 Electrochemical impulses
travel from frontal lobes –
motor nerves- muscle fibers
and cause them to contract.
 Coordination = parietal lobes
of the cerebrum (conscious
muscle sense) and in the
cerebellum (unconscious
Structure of Skeletal Muscle
 The membrane that surrounds the muscle cell is
called the sarcolemma.
 Muscle cells are filled with 2 types of fine
threadlike proteins: MYLOFILAMENTS
 myosin (thick)
 actin (thin).
 The myofilaments are
arranged in the cells in small
units called sarcomeres.
Structure of Skeletal Muscle
 Neuromuscular junction
 Spot where the axon of a motor nerve nears
the muscle fiber.
 The axon terminal does not touch the muscle
but comes close. The space between the
axon and the muscle cell is called the
 Within the terminal end of the axon are small
sacs filled with a neurotransmitter called
Muscle Contraction
 Sequence
 Electrical impulse travels down a motor
neuron. When it reaches the end,
acetylcholine (chemical) is released into the
 Acetylcholine bind to special receptors on
the muscle cell and causes an electrical
impulse to spread over the cell.
 The sarcomeres shorten and the muscle cell



Movement of Muscles
 Origin: the attachment of
the muscle to the bone
that remains stationary

 Insertion: the attachment belly
of the muscle to the bone
that moves

 Belly: the fleshy part of
the muscle between the insertion
tendons of origin and/or
Movement of skeletal muscle
 These muscles move when the brain
sends messages to the muscle
 Always work in pairs
 2 movements of skeletal muscle
 Contraction (shorten)
 Extension (lengthen)
Categories of
skeletal muscle actions
 Categories Actions
 Extensor Increases the angle at a joint
 Flexor Decreases the angle at a joint
 Abductor Moves limb away from midline of body
 Adductor Moves limb toward midline of body
 Levator Moves insertion upward
 Depressor Moves insertion downward
 Rotator Rotates a bone along its axis
 Sphincter Constricts an opening
Practice these Movements
1. Bend arm
– biceps  contract
– triceps  extend
2. Straighten arm
– biceps  extend
– triceps  contract
3. Bend knee
– quadriceps  extend
– hamstrings  contract
More Movements
4. Straighten knee
– quadriceps  contract
– hamstrings  extend
5. Crunches
– abdomen  contract
– back muscles  extend
6. Point toes
– calf muscle  contract
– shin muscle  extend
Naming Skeletal Muscles

 Location of the muscle
 Shape of the muscle
 Relative Size of the muscle
 Direction/Orientation of the muscle

    (around cranium)

 Tibialis anterior tibialis
(front of tibia) anterior
Naming Skeletal Muscles
 Shape:
 deltoid (triangle)
 trapezius (trapezoid, 2
parallel sides)

 serratus (saw-

 rhomboideus
(rhomboid, 4 parallel
sides) Rhomboideus
 orbicularis and major
sphincters (circular)Serratus anterior
Muscles Named by Size
 maximus (largest) minor
 minimis (smallest)
 longus (longest) major
 brevis (short)
 major (large)
 minor (small)
Muscles Named by
Direction of Fibers
 Rectus (straight)
–parallel to long Rectus
axis abdominis

 Transverse

 Oblique
Muscles Named for
Number of Origins

 Biceps (2)

 Triceps (3)

 Quadriceps (4)
Muscles Named for Origin and
originates from
sternum and clavicle insertion
and inserts on
mastoid process of
temporal bone

Muscles Named for Action
 Flexor carpi radialis
(extensor carpi radialis)
– flexes wrist

 Abductor pollicis brevis
(adductor pollicis) Adductor
– flexes thumb magnus
 Abductor magnus
– abducts thigh

 Extensor digitorum
– extends fingers
Arrangement of Fascicles

 Parallel
 strap-like
 ex: sartorius

 Fusiform
 spindle shaped
 ex: biceps femoris
Arrangement of Fascicles
 Pennate
 “feather shaped”

 Unipennate
 ex: extensor
digitorum longus

 Bipennate
 ex: rectus femoris

 Multipennate
 ex: deltoid
Arrangement of Fascicles
 Convergent
 ex: pectoralis

 Circular
 sphincters
 ex: orbicularis oris

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