This document discusses muscles and the muscular system. It begins by defining muscles and describing the various classifications of muscles. The key types are skeletal muscles, which are striated and voluntary. Skeletal muscles have origins, insertions, and bellies. They act to produce movement, maintain posture and support, and generate heat. The document outlines the structure of muscles and their components. It also categorizes muscles based on shape, function, and other characteristics.

1. MUSCLE
Dr. Seyed Morteza Mahmoudi,
MBBS

2. MUSCULAR SYSTEM
For the students of Gulf Medical University, Ajman, PharmD
LECTURE 21
Dr. Seyed Morteza Mahmoudi, MBBS
Gulf Medical University, Ajman

3. LEARNING OBJECTIVE
• Define muscle
• Understand the gross and
microscopic structure of
muscle
• What are the various
classifications of muscles?

5. • What are muscles?
• What are the types of muscles?
• What are their functions?

8. • There are approximately 639 skeletal muscles in the
human body.

9. Functions of skeletal muscle
1. Movement:
2. Support and posture maintain a constant state of slight
contraction – muscle tonus.
3. Heat production: The contraction of skeletal muscle
involves the production of energy, the by-product of which is
heat.

10. Functions
•Prime movers- chief muscle for primary movement
•Antagonists-opposing action of prime mover
•Fixators (increase tone but not movement) eg
shoulder girdle to trunk muscles for deltoid to act.
•Synergists –acting on intermediate joints to prevent
unwanted movements eg.. Flexor and extensors of carpus
on wrist to facilitate efficient movement of digits.

11. Visceral muscles are smooth and without banding.
They have short fibres and single cell nuclei.
These are involuntary muscles
Sites
•Walls of blood vessels and viscera (organs in the abdominal cavity).
•Sphincter & dilator pupillae
•Orbitalis muscle in orbit and Muller’s muscle in upper eyelid
•Dartos muscle in scrotum
•Arrector pilorum of hair follicle.
•Myoepithelial cells in glands

12. A muscle has 2 attachments
•Origin- the attachment that moves
the least
•Insertion- the attachment that
moves the most
•Belly- fleshy part of a muscle
•Tendon- end of a muscle that is
attached to bones, cartilage or
ligaments
•Aponeuroses- a flattened tendon
•Raphe- interdigitation of tendinous
ends of a flat muscle

14. MUSCLES
• The red flesh of the body that are the
specialized contractile cells
• The parts of a muscle are its:
Origin
Muscle attachment that remains
fixed
origin
Insertion
Muscle attachment that moves
belly
insertion
Belly
Fleshy and contractile part of a
muscle
Action
What joint movement a muscle
produces i.e. flexion,
extension, abduction etc.

15. •
Muscles are joined to bone by tough connective tissue called TENDON

16. CLASSIFIED
i)Voluntary muscle-under one’s control
and Involuntary muscles-not under
willful control
ii)Striated muscle-appears striated
under microscope;
Smooth/unstriated- appears
unstriped/unstriated
iii)Somatic muscle- makes up the body
wall and limbs.Visceral musclesmuscular component of hallow organs

18. Type I slow fibers Type II fast fibers Intermediate
of skeletal muscle of skeletal muscle fibers of skeletal
muscle
Slow tonic specially designed
for postural muscles, red in
colour due to high
concentration of myoglobin and
rich in mitochondria and
oxidative enzymes
Fast tonic contractions needed
for body movement, pale
colour rich in glycogen and
phosphorylases
Varient of Type II
Highly resistance to fatigue
due to well-developed in
aerobic respiration
Easily fatigue
Resistant to fatigue

19. Classified based on shape
Flat :eg: external oblique.The muscle fibers will run paralle to the
line of pull.
Quadrilateral:eg: thryohyoid
Strap like:eg: sartorius
Strap like with tendinous insertion:eg: rectus abdominus
Fusiform:eg: biceps brachi
Pennate: are oblique placed faciculi, feather like in
arrangement of the fasicles in relation to a tendon
i.
Unipennate: eg: extensor digitorum longus
ii.
Bipennate: eg: gastronimeus
iii.
Multipenate : eg: deltoid

20. •
Spiral fasciculi : spiral or
twisted fibers are seen as seen
in trapezius pectoralis major
• Circular: muscle
surrounds a body
orifices, constricting
when contracted
eg: orbicularis oculi

21. Classified based on movement
Prime mover: A muscle that is
chiefly responsible for a
particular movement
Antagonist: A muscle that opposes
the action of a prime mover
Synergist: A muscle that prevents
unwanted movements in an
intermediate joint where the
another muscle crosses that
joint. To prevent unwanted
movements and stabilizes the
intermediate joints.
Fixator: A muscle that contracts
isometrically, to stabilize the
origin of the prime mover so
that it can act efficiently
Concentric action: the
muscle length shortens
to produce a movement
Isometric action :the
muscle length remains
constant on producing a
movement
Excentric action: the
muscle lengthens when
active

22. Range of contraction
• Active
insufficiency:
normally muscles
contract 40%of its
fully stretched
state. This
limitation in the
range affects all
muscles that act on
several joints
simultaneously, thus
unable to shorten to
produce full range
•
Passive insufficiency: the
opposing muscle unable to
stretch beyond a certain length
to allow full range of movement
is Passive insufficiency.

25. Muscles

26. Types
Muscles
Skeletal muscles are striated (have distinct bands) made up of
fibres (long cells). – 30cm!!!!
The cells are multinucleated (many cell nuclei) and contract and relax
quickly.
These are voluntary muscles attached to the skeleton that help to
move the bones.
There are nearly 700 skeletal muscles spread all over the body.
Ends attached to bones, cartilage or ligaments by tendons,
aponeuroses

27. Structure of a muscle

30. Properties of skeletal muscle
1. Extensibility – the ability of muscle tissue to lengthen when
contracting
2. Elasticity – the ability of muscle tissue to return to its normal
resting length after being stretched, allowing repeated contractions
3. Contractility – the capacity of a muscle to contract or shorten
forcibly when stimulated by nerves or hormones (excitability).
4. Controlled by nerve stimuli.
5. Will atrophy (waste) –inadequate blood supply
6. Will hypertrophy -overworked

31. •Raphe is between 2 flat muscles serving as an
attachment

32. Aponeuroses – thin sheet of fibrous tissue attached to flat
muscles

33. Different forms
Rhomboid

34. Strap muscles

35. Fusiform
Bipennate;
Lumbricoid
Rectus
Flat
Unipennate
Multipennate