Muscular system class at addis ababa cba

Anatomy

1. The Muscular system
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YosefTadesse

2. Introduction
•The muscular system and muscular tissue contribute to
homeostasis by
–producing movements
–stabilizing body position
–regulating organ volume
–moving substances within the body
–producing heat
•Muscle is highly cellular, well-vascularized tissue
•Muscle provides contractile force by shortening
•There are three kinds of muscle tissue
–Skeletal muscle
–Cardiac muscle
–Smooth muscle
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3. Function
•Body movement
–Most skeletal muscles are attached to bones, are
typically under conscious control, and are responsible for
most body movements including walking, running, or
manipulating objects with the hands
•Maintenance of posture
–Skeletal muscles constantly maintain tone, which keeps
us sitting or standing erect
•Respiration
–Muscles of the thorax are responsible for the
movements necessary for respiration
•Production of body heat
–When skeletal muscles contract, heat is given off as a
by-product. This released heat is critical to the
maintenance of body temperature.
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4. •Communication
–Skeletal muscles are involved in all aspects of
communication, such as speaking, writing, typing,
gesturing, and facial expression
•Constriction of organs and vessels
–The contraction of smooth muscle within the walls
of internal organs and vessels causes constriction
of those structures
–This constriction can help propel and mix food and
water in the digestive tract, propel secretions
from organs, and regulate blood flow through
vessels
•Heart beat
–The contraction of cardiac muscle causes the
heart to beat, propelling blood to all parts of the
body 4

5. •Muscle tissues differ in
–the structure of their cells
–their body location
–their function
–the means by which they are activated to
contract
•Muscle cells are elongated and are
referred to as muscle fibers
•Prefixes of myo or mys and sarco refer
to muscle
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6. Functional Characteristics
•Excitability or irritability: the ability to
respond to a stimulus
•Contractility: the ability to shorten
•Extensibility: the ability to stretch
•Elasticity: the ability to resume normal
length after being shortened or
contracted
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7. Skeletal muscles of the
body
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8. Attachments
•Most muscles span joints and have at least two
attachments
•Origin
–Attachment of a muscle that remains relatively fixed during
muscular contraction
–Generally a more proximal or axial location
•Insertion
–Attachment of a muscle that moves during muscular
contraction
–Generally a more distal or appendicular attachment
•Direct attachments have the epimysium attaching
directly to the periosteum of the bone or
perichondrium of a cartilage
•Indirect attachments have the epimysium attaching to
a tendon or an aponeurosis
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9. Interactions of Skeletal Muscles
•Muscle contraction causes shortening, not
lengthening of a muscle
•Typically, as a muscle contracts it moves
its insertion toward its origin
–only pull on the skeleton; they can never push
•The arrangement of body muscles permits
them to work either together or in
opposition to achieve a movement
•Generally muscles are grouped to “undo” an
action done by another group
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10. Functional Muscle Groups
•Muscles can be classified into four
functional groups
–Prime movers (agonists)
–Antagonists
–Synergists
–Fixators
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11. Prime Movers (agonist)
•A muscle that
provides the
major force for
producing a
specific
movement
•E.g. biceps
brachii is the
prime mover of
elbow flexion
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12. Antagonist
•Muscles that oppose a
particular movement
•When a prime mover is
active, the antagonist
muscles are often
stretched or in
relaxed state
•Antagonists also
regulate the action of
prime mover
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13. Synergist
•Synergists aid agonists by
–promoting the same movement
–Eg: brachialis is a synergist in elbow
flexion
–reducing extraneous movements that
may be produced when the prime
mover acts
•In two joint muscles synergists stabilize a
joint as the muscle acts on the other
•Synergist can also restrict rotary
movement at a joint so the muscle’s full
effort be applied to the desired
movement
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14. Fixator
•Serves to stabilize
the bone upon which
a prime mover acts
•E.g. Serratus
anterior holds the
scapula against the
thorax while a prime
mover acts upon the
arm
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15. Naming Skeletal Muscles
•Shape: relative shape of the muscle
–Deltoid: Triangular e.g. Deltoid
–Trapezius: Trapezoid e.g. Trapezius
–Serratus: Sawtoothed e.g. Serratus anterior
–Rhomboid: Diamond-shaped e.g. Rhomboid major
–Orbicularis: Circular e.g. Orbicularis oculi
–Pectinate: Comblike e.g. Pectineus
–Piriformis: Pear-shaped e.g. Piriformis
–Platys: Flat e.g. Platysma
–Quadratus: Square, four-sided e.g. Quadratus
femoris
–Gracilis: Slender e.g. Gracilis
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16. •Location: structure near which a muscle
is found
–Pectoralis: chest
–Intercostal: between ribs
–Temporalis: near the temporal bone
•Attachment: sites where muscle
originates and inserts
–Sternocleidomastoid: originating on the sternum and
clavicle and inserting on the mastoid process of the
temporal bone
•Relative position
–Medial: e.g. medial rectus
–Lateral: e.g. lateral rectus
–Internal: e.g. internal oblique
–External: e.g. external oblique
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17. •Size: relative size of the muscle
–Maximus: Largeste.g. Gluteusmaximus
–Minimus: Smallest e.g. Gluteus minimus
–Longus: Long e.g. Adductor longus
–Brevis: Short e.g. Adductor brevis
–Latissimus: Widest e.g. Latissimusdorsi
–Longissimus: Longeste.g. Longissimus
capitis
–Magnus: Large e.g. Adductor magnus
–Major: Larger e.g. Pectoralismajor
–Minor: Smaller e.g. Pectoralisminor
–Vastus: Huge e.g. Vastus lateralis
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18. •Number of origins: number of tendons of origin
–Biceps: Two origins e.g. Biceps brachii
–Triceps: Three origins e.g. Triceps brachii
–Quadriceps: Four origins e.g. Quadriceps
femoris
•Direction: orientation of muscle fascicles
relative to the body’s midline
–Rectus: Parallel to midline e.g. Rectus
abdominis
–Transverse: Perpendicular to midline e.g.
Transversus abdominis
–Oblique: Diagonal to midline e.g. External
oblique
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19. •Action: principal action of the muscle
–Flexor: Decreases a joint angle e.g. Flexor carpi radialis
–Extensor: Increases a joint angle e.g. Extensor carpi ulnaris
–Abductor: Moves a bone away from the midline e.g. Abductor
pollicis longus
–Adductor: Moves a bone closer to the midline e.g. Adductor
longus
–Levator: Raises or elevates a body part e.g. Levator scapulae
–Depressor: Lowers or depresses a body part e.g. Depressor labii
inferioris
–Supinator: Turns palm anteriorly e.g. Supinator
–Pronator: Turns palm posteriorly e.g. Pronator teres
–Sphincter: Decreases the size of an opening e.g. External anal
sphincter
–Tensor: Makes a body part rigid e.g. Tensor fasciae latae
–Rotator: Rotates a bone around its longitudinal axis e.g.
Rotatore
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Arrangement of Fascicles

21. Parallel
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•The long axis of the fascicles run parallel
to the long axis of the muscle
•Terminate at either end in flat tendons
•Form long strap like muscles that have
greatest potential for shortening
•Not very powerful

22. Fusiform
•Fascicles nearly parallel to longitudinal
axis of muscle
•Terminate in flat tendons
•Muscle tapers toward tendons, where
diameter is less than at belly
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23. Pennate
•Short fascicles in relation to total muscle
length; attach obliquely to a central tendon
which extends nearly entire length of muscle
•Occur as 3 forms
(a) Unipennate
(b) Bipennate
(c) Multipennate
•Have highest concentration of fibers, shorten
little, but are very powerful
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24. •Unipennate: fascicles are arranged on only one
side of tendon
•Bipennate: fascicles are arranged on both
sides of centrally positioned tendons
•Multipennate: fascicles attach obliquely from
many directions to several tendons
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25. Convergent
•Fascicles spread over
broad area converge at
thick central tendon
•Has a broad origin and its
fascicles converge toward
a single tendon
•Triangular shape
•Can act upon the joint
from a variety of positions
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26. Circular
•Fascicular pattern is
arranged in concentric
rings
•Surround external body
openings which they
close by contracting
•This type of muscles are
called sphincters
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