Download The Muscles (Myology)

By
Dr.Pardeep Kumar
The General Description of Muscles
Muscular System
The Muscular System
 Muscles are responsible for all types of
body movement – they contract or
shorten and are the machine of the
body.
 Skeletal is a voluntary muscle
 Skeletal muscles share 40% of body
weight.
Muscular System
Characteristics of Muscles
 Muscle cells are elongated
(muscle cell = muscle fiber)
 Contraction of muscles is due to the
movement of microfilaments
Muscular System
Skeletal Muscle Characteristics
 Most are attached by tendons to bones
 Cells are multinucleate
 Striated – have visible banding
 Voluntary – subject to conscious control
 Cells are surrounded and bundled by
connective tissue = great force, but tires
easily
Muscular System
Skeletal Muscles (striated or voluntary muscles)
are those which attach to bones and have the main function
of contracting to facilitate movement of our skeletons.
Muscular System
Structure
Structure of
of skeletal
skeletal muscle
muscle
Muscular System
Structure
Structure of
of skeletal
skeletal muscle
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).
Myofibrils: threadlike fibrils
that make up the contractile
part of a striated muscle fiber.
Fascia –
on the outside of the epimysium
skeletal muscle structure
Muscular System
Structure
Structureof
ofskeletal
skeletalmuscle
muscle

Muscle fibers are made up of a group of myofibrils.

Myofibrils contain myofilaments.
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The myofibrils have distinct, repeating microanatomical
units, termed sarcomeres, which represent the basic
contractile units of the muscle fiber/cell (myocyte).
Myofilaments (actin & myosin)
are responsible for muscle
movement.
Muscular System
Structure of skeletal muscle

Myofilaments: (Thick and Thin)
 Myosin: thick filaments
 Actin: thin filaments
 A unit of thick and thin filaments is known as a
Sarcomere.
 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.
Muscular System
Structure of skeletal muscle
Muscular System
Structure of skeletal muscle
Muscular System
Skeletal Muscle Attachments
 Epimysium blends into a connective
tissue attachment
 Tendon – cord-like structure
 Aponeuroses – sheet-like structure
 Sites of muscle attachment
 Bones
 Cartilages
 Connective tissue coverings
Muscular System
Origin and insertion of muscles



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Muscles are attached to
at least two points
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)
Muscular System
Action of skeletal Muscles
 Prime mover – muscle with the major
responsibility for a certain movement
 Antagonist – muscle that opposes or
reverses a prime mover
 Synergist – muscle that aids a prime
mover in a movement and helps
prevent rotation
Muscular System
Naming of Skeletal Muscles
 Direction of muscle fibers
 Example: rectus (straight)
 Relative size of the muscle
 Example: maximus (largest)
Muscular System
Naming of Skeletal Muscles
 Location of the muscle
Example: many muscles are named
for bones (e.g., temporalis)
 Number of origins
Example: triceps (three heads)
Muscular System
Naming of Skeletal Muscles
 Location of the muscles origin and
insertion
 Example: sterno (on the sternum)
 Shape of the muscle
 Example: deltoid (triangular)
 Action of the muscle
 Example: flexor and extensor (flexes or
extends a bone)
Muscular System
It includes:Muscles of Back
Muscles of thorax
Diaphragm
Muscles of abdomen
The muscles of back
Superficial group
 Trapezius
 Latissimus dorsi
 Levator scapulae
 Rhomboideus Major
 Rhomboideus Minor
1.Trapezium
2.Levator scapular
Deltoid
3.Rhomboideus
Triangle of ausculation
4.Latissimus dorsi
Thoracolumbar fascia
Trapezius
 Origin – medial 3rd of superior nuchal line of occipital bone
 External occipital protuberance
 Ligamentum nuchae
 Spine of 7th cervicle vertebrae
 T1 – T12 spines
 Corresponding supraspinatous ligaments
 Insertion – Lateral 3rd of clavicle
 Acromion & upper lip of crest of spine
 Medial end of spine of Scapula
 Action – Rotate the scapula during
abduction of the arm beyond 90
 Weakness of this muscle leads to dropping
shoulder
Muscular System
Base of skull
(occipital
protuberance)
Latissimus Dorsi
Origin
 posterior part of iliac crest
 Spines of lower 6 Thoracic vertebrae
 lower 3 or 4 ribs
 Lumbar Fascia
 Inferior angel of scapula
Insertion
 floor of the inter tubercular sulcus
Nerve Supply – Thoracodorsal nerve
Action
 It extends, adducts & medailly
rotates the arm
Levator Scapulae
Origin
 Transverse process of upper 4 cervical vertebrae
Insertion
 Superior angle & Medial border of scapula
Nerve Supply
 Dorsal scapular nerve
 3rd & 4th cervical nerve
Action –
Elevation of scapula
Rhomboideus Major
 Origin –
 2nd – 5th thoracic spine
 I – Medial border of scapula
 Nerve Supply – Dorsal scapular nerve
 Action – Elevates the medial border & of scapula & pulls it medially
Rhomboideus Minor
Origin
 Lower part of ligamentum nuchae
 Spines of lower 7th cervicle & 1st thoracic vertebrae
Insertion
 Medial border of scapula
Nerve Supply –
 Dorsal scapular nerve
Action –
 Elevates the medial border of scapula & pulls it medially
Triangle of auscultation
 Small triangular gap at the back
Boundary
 Superiorly - Lateral border of Trapezius
 Laterally - Medial border of scapula
 Inferiorly - Upper border of latissimus dorsi.
 Floor is by seventh rib, 6th & 7th intercostal spaces & rhomboideus major.
Clinical Importance of auscultation
 Only part not covered by the muscle.
 Used to hear the respiratory sounds are better heard with stethoscope
 On the Right side – Breadth sound is auscultated
 On the Left side – Any kind of Esophageal obstructions can be by
auscultation
Muscles of Thorax
The muscles of thorax
Extrinsic muscles
 Pectoralis major
 Pectoralis minor
 Serratus anterior
Intrinsic muscles
 Intercostales externi
 Intercostales interni
Pectoralis major
 Origin
 Anterior surface of medial half of
clavicle
 Anterior surface of sternum
 6th costal cartilage
 Insertion
 Crest of great tubercle of
Humerus
 Action
 Adduction
 Flexion
 Medical rotation
Pectoralis minor
(lies deep to pectoralis major)
 Origin
 Anterior external surface of 3rd
to 5th ribs.
 Insertion
 Coracoid process of scapula
 Action
 Forward and downward
movement of scapula
Serratus anterior
 Origin
 External surface of upper
8~9 ribs.
 Oblique externus
abdominis
 Insertion
 Anterior surface of medical
border of scapula
Intercostales externi
 Origin: lower border of each
rib
 Insertion: upper border of
each rib
 Action: elevate the rib
(muscles of inspiration)
 Replaced anteriorly by external
intercostals membrane.
Intercostales interni
 Origin: upper border of rib
 Insertion: lower border of rib
 Action: depress ribs (muscles
of expiration)
 Replaced posteriorly by internal
intercostals membrane.
Diaphragm
Shape and position:
dome-shaped between thorax and
abdomen, consists of a peripheral
muscular part and a central tendon
Origin

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Sternal part: xiphoid process
Costal part: lower six ribs and costal
cartilages
Lumbar part: arises by two crura from
upper 2~3 lumbar vertebrae
Insertion: central tendon
Weak areas: triangular spaces without


muscular tissue
Lumbocostal triangle: between costal
and lumbar parts.
Sternocostal triangle: between costal
and sternal parts.
Openings in the diaphragm
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Aortic hiatus－lies anterior to the body of the 12th thoracic
vertebra between the crura. It transmits the aorta, thoracic
duct
Esophageal hiatus －for esophagus and vagus nerves at level
of T10.
Vena cava foramen －for inferior vena cava, through central
tendon at T8 level
T8
T10
T12
Action:


Contraction: the dome
moving downward,
increases the volume of
thoracic cavity which
results in inspiration, at the
same time the intraabdominal pressure is
increased assists in
defecation, vomiting or
child birth.
Relaxation: the dome
returns to the former
position, reduces the
volume to the thoracic
cavity, resulting in
expiration.
Muscles of abdomen
Anterolateral group
 Obliquus externus absominis
 Oblequus enternus
abdominis
 Transversus abdominis
 Rectus abdominis
Posterior group
 Quadiatus lumborum
 Psoas major
Obliquus
externus
abdominis
Origin : external surface
of lower 8 ribs.
downward, forward
and medially (run
down and inward)
Insertion : iliac crest
The lower part of
aponeurosis of this
muscles forms
 Inguinal ligament
 Lacunar ligament
 Superficial
inguinal ring
－
triangular-shaped
defect in aponeurosis
of obliquus externus
abdominis above
pubic tubercle
internus
 Obliquus
Deep to obliquus


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
externus
abdominis
General direction
of fibres: upwards,
forwards and
medially
Origin:
thoracolumbar fascia
Anterior 2/3rd of iliac crest
Lateral 2/3 of inguinal
ligament

Insertion:

Cartilage of 7th to 10th ribs
abdominis
Transversels abdominis



Deep to obliquus internus
Origin

Inner surface of costal cartilage of
lower 6 Ribs.
Thoracolumbar fascia
Iliac crest
Lateral 1/3rd of inguinal ligament

Insertion

Sheath of rectus abdominis
Inguinal falx with aponeurosis of
obliquus internus abdominis



 Inguinal falx : arch over
spermatic cord, inserted
with transverses
abdominis fiber into
medial part of pecten of
pubis
 Cremaster: around the
spermatic cord and testis
Rectus abdominis
 Position: lie on to either side of
midline
 Origin: pubic crest and
symphysis
 Insertion: xiphoid process and
5th-7th costal cartilages
 Has 3-4 tendinous intersections
Similar functions for above four pairs of muscles
 Support and compress the abdominal viscera
 Increase intra-abdominal pressure, aid in expulsive
efforts-vomiting, coughing, sneezing, defecation,
urination and childbirth.
 Depress ribs, assist in (the act of force(4)expiration.
 Flex, lateral flex, and rotate vertebral column
Sheath of rectus abdominis
Ant layer－formed by fusion of aponeurosis of
obliquus externus abdominis and anterior
leaf of aponeurosis of obliquus internus
abdominis
Post layer

Formed by fusion of posterion leaf of
aponeurosis of obliquus internus
abdominis and aponeurosis of transverses
abdominis

Absent in about 4-5cm below the
umbilicus, where aponeuroses of all three
muscles form anterior layer the lower free
border named arcuate line

Below this line rectus abdominis in contact
with transverse fascia
Linea alba
－tendinous raphe between right and left recti from xiphoid to pubic symphysis.
Inguinal region
Boundaries
 Inguinal ligament
 Lateral margin of rectus
abdominis
 A horizontal line
stretching from anterior
iliac spine to lateral
margin of rectus
abdominis
Descent of testes
Seven-week embryo showing the
testis before its descent from the
dorsal abdominal wall
Fetus at 28 week the testis passing
through the inguinal canal
Newborn
Inguinal canal
Position: oblique passage, 4cm long, located 1.5cm above
medial half of inguinal lig.
Boundaries
 Ant wall


Aponeurosis of
obliquus externus
abdominis
Obliquus internus
abdominis (lateral
third of wall)
 Post wall
 Transverse fascia
 Inguinal flax medially
 Roof－arched lower
fibers of obliquus
internus and
transversua abdominis
 Floor－inguinal lig．
 Two openings
 Superficial inguinal ring
 Deep inguinal ring －defect in
transverse fascia 1.5cm above
midpoint of inguinal ligament
 Structures passing through the inguinal canal
 Spermatic cord and ilioinguinal nerve in males
 Round ligament of uterus and ilioinguinal nerve in females
Inguinal Triangle (of Hesselbach)
Boundaries
 Inguinal ligament
inferiorly
 Lateral border of
rectus abdominis
medially
 Inferior epigastric
artery laterally
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