The Muscular System

THE MUSCULAR
SYSTEM
DocPoks Pangan M.D
Natural Science

• The bones, muscles and joints together form an integrated system called the Musculoskeletal System
• Myology is the scientific study of muscles
• Muscular system is an organ system consisting of skeletal, smooth and cardiac muscles
• Orthopedics is the branch of medical science concerned with the prevention or correction of the disorders of the musculoskeletal system

ANTERIOR VIEW

POSTERIOR VIEW

FUNCTIONS OF THE MUSCLES

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Movement
Maintenance of posture and muscle tone
Heat production
Protects the bones and internal organs.

MUSCLE CLASSIFICATION
• Functionally
• Voluntarily – can be moved at will
• Involuntarily – can’t be moved intentionally
• Structurally
• Striated – have stripes across the fiber
• Non Striated(Smooth) – no striations

THE 3 TYPES OF MUSCLES
3 T y p e s o f M u s c le s
S k e le t a l M u s c le

S m o o t h M u s c le

C a r d ia c M u s c le

SMOOTH MUSCLE
Involuntary muscle due to our inability to control its movements.
 Found in the walls of hollow organs such as the stomach, esophagus, bronchi and in the walls of blood vessels.
• Fibers are thin and spindle shaped.
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No striations
Single nuclei
Involuntary
Contracts slowly

SMOOTH MUSCLE
• They fatigue… but very slowly
• Found in the circulatory system
• Lining of the blood vessels
• Helps in the circulation of the blood

• Found in the digestive system
• Esophagus, stomach, intestine
• Controls digestion

SMOOTH MUSCLE
• Found in the respiratory system
• Controls breathing

• Found in the urinary system
• Urinary bladder
• Controls urination

SMOOTH MUSCLE

CARDIAC MUSCLE
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Cells are branched and appear fused with one another • Has striations
• Each cell has a central nuclei • Involuntary

• 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 cylindrical  Has many nuclei
 Has striations
 Have alternating dark and light bands
 Voluntary

STRUCTURE OF SKELETAL MUSCLE
Epimysium
This is the connective tissue wrap just under the deep fascia that surrounds the entire muscle

Perimysium
This connective tissue surrounds each individual fascicle (bundle of muscle fibers).

Endomysium
This is the connective tissue wrapped around each individual muscle cell (fiber).

STRUCTURE OF SKELETAL MUSCLE
Myofibrils

Threadlike fibrils that make up the contractile part of a striated muscle fiber

STRUCTURE OF SKELETAL MUSCLE
Microscopic anatomy
• Muscle cells (fibers) are grouped in a highly organized way in the muscle. The membrane that surrounds the muscle cell is called the sarcolemma. • Muscle cells are filled with 2 types of fine threadlike proteins called myofilaments: myosin (thick) and actin (thin). These structures slide past each other causing the muscle cell to contract or shorten.
• The myofilaments are arranged in the cells in small units called sarcomeres.

STRUCTURE OF SKELETAL MUSCLE

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Myofilaments - (Thick and
Thin)
Myosin - thick filaments
Actin - thin filaments
Sarcomere - A unit of thick and thin filaments.
.

• These structures hold the key to muscle contraction. The staggered thin and thick filaments has the effect as one might pull a rope towards oneself hand over hand.

STRUCTURE OF SKELETAL MUSCLE

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 actions. – 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 bundles of striated muscle cells or fibers that are held together by a sheath of connective tissue.
• 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 insertion.

• Tendons anchor muscle firmly to bones. Tendons are made of dense fibrous connective tissue.
• Ligaments connect bone to bone at a joint.

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 fluid.

STRUCTURE OF SKELETAL MUSCLE
Contribution of the nervous system
• Electrochemical impulses travel from the frontal lobes of the cerebrum via motor nerves to the muscle fibers and cause them to contract.

• Sensation is a function of the brain – impulses are integrated in the parietal lobes of the cerebrum (conscious muscle sense) and in the cerebellum (unconscious). These activities promote coordination

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 synapse.
• Within the terminal end of the axon are small sacs filled with a neurotransmitter called acetylcholine. NEUROMUSCULAR JUNCTION

MUSCLE CONTRACTION
Sequence
• Electrical impulse travels down a motor neuron.
When it reaches the end, acetylcholine
(chemical) is released into the synapse.
• 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 contracts. MOVEMENT OF MUSCLES
• Origin: the attachment of the muscle to the bone that remains stationary • Insertion: the attachment of the muscle to the bone that moves
• Belly: the fleshy part of the muscle between the tendons of origin and/or insertion

origin

belly

insertion

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
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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

NAMING SKELETAL MUSCLES
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Location of the muscle
Shape of the muscle
Relative Size of the muscle
Direction/Orientation of the muscle fibers/cells
Number of Origins
Location of the Attachments
Action of the muscle

MUSCLES NAMED BY LOCATION
• Epicranius (occipitofrontalis) around cranium
• Tibialis anterior (front of tibia)

NAMING SKELETAL MUSCLES
Shape:
Trapezius
• deltoid (triangle)
• trapezius (trapezoid, 2 parallel sides)
• serratus (saw-toothed)
Deltoid
• rhomboideus (rhomboid, 4 parallel sides)
• orbicularis and sphincters (circular)

Serratus anterior

Rhomboideus major MUSCLES NAMED BY SIZE
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maximus (largest) minimis (smallest) longus (longest) brevis (short) major (large) minor (small)

Psoas minor
Psoas major

MUSCLES NAMED BY
DIRECTION OF FIBERS
• Rectus (straight)
–parallel to long axis
• Transverse

Rectus abdominis • Oblique

External oblique

MUSCLES NAMED FOR
NUMBER OF ORIGINS
• Biceps (2)
• Triceps (3)

Biceps brachii

• Quadriceps (4)

MUSCLES NAMED FOR ORIGIN AND INSERTION
Sternocleidomastoid
Originates from sternum and clavicle and inserts on mastoid process of temporal bone

insertion

origins

ORIGIN AND INSERTION OF MUSCLE
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Origin: the point where the tendon attaches to the bone which does not move during muscle action. Insertion: the point where the tendon attaches to the bone which moves during an action.
e.g. Action of biceps muscle: Scapula is origin
(Proximal point) and radius is the insertion.
(distal point)

MUSCLES NAMED FOR ACTION
• Flexor carpi radialis (extensor carpi radialis)
– flexes wrist
• Abductor pollicis brevis (adductor pollicis)
– flexes thumb
• Abductor magnus
– abducts thigh
• Extensor digitorum
– extends fingers

Adductor magnus One Joint
Muscle

Two Joint Muscle

Lateral Hamstrings
Medial
Hamstrings

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 major

• Circular
• sphincters
• ex: orbicularis oris

MUSCLES TO REMEMBER…

THERE ARE ABOUT 60 MUSCLES IN THE FACE
SMILING IS EASIER THAN
FROWNING
IT TAKES 20 MUSCLES TO SMILE AND OVER 40 TO FROWN.

THANK YOU! I LOVE U GUYS!