Download Muscles

Muscles and Tendons
By
Dr MB Samarawickrama
(MBBS MS)
31th Batch July 2008
Muscles
Three types
• Skeletal Muscles
• Cardiac Muscles
• Smooth Muscles
Muscles
Need to know
• Histology
• Gross Anatomy
• Physiology
Muscles
Skeletal Muscles
• Formed by
number of
muscle fibers
• Non branching
Muscles-Histology
• Skeletal muscles
• Consist of unbranched fibres
• Banded by striations
• Small nuclei, placed peripherally on the surface
of the fibres
Microscopic structure
• Fiber’s size varies within a single muscle
• Hypertrophy of muscle results increase in
size of the fiber
• The number remains the same
• These fibres are bound together by a
loose areola tissue
• This envelope is known as epimysium
Muscles-Histology
ENDOMYCIUM,
PERIMYCIUM
EPIMYCIUM
Cardiac muscle
• Also striated
• Fibres are branched
• Large nuclei placed centrally
Smooth muscle
• Long spindle shaped cells
• Nucleus lies centrally
• Parallel cells joined to form muscle fibres
• The fibres arrange Circularly, longitudinally or
whorls & spirals with no demonstrable layers
The form of muscles
Fibres in a muscle
arrange in two
ways
• Parallel to the
line of pull
– increase range
of mobility
The form of muscles
• Oblique to the
line of pull
– range of mobility
is less
– Force of pull is
maximum
The form of muscles
E.g.
muscles with Parallel fibers
• Sartorius
• Rectus abdominis
• Infrahyoid muscles
• Anterior & posterior
fibres of the deltoid
Muscles with Parallel
Fusiform
The form of muscles
The muscles with oblique fibres
• One of 4 patterns
– Unipinate muscles
– Bipennate Muscles
– Multipinate Muscles-two types
The form of muscles
Unipinate muscle
• The tendon forms along
one margin of the muscle
• All the fibres slope into
one side of the tendon
• e.g. Flexor Policis Longus
The form of muscles
Bipennate Muscles
• The tendon forms centrally
• muscle fibres slope into the
two sides of the central
tendon.
– Like a feather
• e.g. Rectus Fumoris
The form of muscles
The form of muscles
Multipinate Muscles
• Two varieties
• Series of bipinnate
masses lying side by
side
• e.g.
• Central part of the deltoid
• Subscapularies
The form of muscles
Multipennate Muscles
• cylindrical muscle within
which a central tendon
forms
• Into the central tendon
muscle fibres converge
from all sides
• e.g. Tibialis anterior
Surface appearance of muscles
• Some more fleshy
• Some largely apponeurotic
• Some have a mixture of two
Surface appearance of muscles
• That reflect the function of the muscle
• If the muscle bears lot of pressure from
adjacent structures – it is covered by an
apponeurosis
• Where there is no pressure it is usually
flesh
Origin and insertion of muscle
• No reality in these terms
• Origin – fixed end
• Insertion – moving end
Origin and insertion of muscle
• But vary depending on the
circumstances
• Use the word attachment instead
Bone markings
• Fleshy origins leaves no marks on
bones
• The area is flatten or depressed on
the bone
•e.g. Pec. Major on the clavicle
Bone markings
• Insertion of a pure
tendon almost always
leave a smooth mark
on the bone
• e.g. Ligamentum
patelle attachment
Bone markings
• Rough marks are made where there is
admixture of flesh & tendon
• or where there is a lenthy insertion of
aponeurosis
• e.g. Linear aspera femur
Bone markings
Flat muscles arise from-flat bone
• Muscle origin does not extend to the edge of the flat
bone
• It origin from an edge of a curved line
• Between the origin and the edge of the bone is a bare
area
• This area is occupied by a bursa
• Which may or may not be communicated with the
adjacent joint
• e.g. subscapularis
Actions of muscles
• The action of muscles or muscle groups
are often oversimplified
• Terms denoting action, in particular,
emphasize only one of a number of
habitual actions
• A given muscle may play different roles in
different movements
Actions of muscles
• these roles may change if the movements
are assisted or opposed by gravity
• Single muscle rarely contract alone
• The action is influence by its companions
in contraction
Actions of muscles
• When a muscle crosses two joints
• It mainly act on distal joint to move it
• On proximal joint it act to steady the joint
– e.g. Biceps long tendon
– Triceps
Actions of muscles
• In such cases
• Position of the proximal joint changes the
length of the muscles
• Thus affect the movement of the distal
joint
Actions of muscles
• e.g. Action of long flexor tendons of the
IPJ is affected by the position of the wrist
• Position of the knee affect the action of the
Gastrocnemius on the ankle joint
Actions of muscles
Synergic actions
• Muscles acting as a prime movers on a certain
joint have a different action when a more distal
segment of the limb is in motion.
• Then they act synergistically to stabilized the
joint during the movement of the distal joint.
• e.g. short muscles of the shoulder estabilized
the shoulder when – wrist fingers & elbow in
movement
Actions of muscles
• Muscles act synergistically in another way
• This is to cancel out unwanted secondary
effect.
• e.g. Tricep contract when the forearm is
supinated while the elbow is flexed.
Actions of muscles
• This prevent the flexion of the elbow by
the contraction of the biceps
• This will not oppose the supination action.
Assessment of Muscle Action
• Common sense
• Feeling of contraction
• Pullin tendons in dead
• Nerve stimulation of motor nerve
• Electromyography
• Comparative anatomy
Action of Paradox
• Multiplicity of common movements are
aided by gravity
• In such movements opposing muscles
contract to keep the limb against the force
of gravity
Action of Paradox
• e.g. When the arm adduct from abducted
position
• Deltoid muscle contract which is a muscle
of abduction
• This is known as action of paradox
Blood supply
• Muscles have a rich blood supply
• Arteries and veins pierce the surface in company
with the motor nerve
• From muscle belly artery supply the tendon
• Lymphatics run back with arteries
• Large blood vessels enter the perimysium
• Branches of perimysial blod vesels ramify
• pass inbetween and surrounds the muscle fibers
Nerve supply of muscles
• Flat muscles of the body wall are pierced
by cutaneous nerve
• They do not supply the muscles
Nerve supply of muscles
In limbs
• If a nerve pierces a muscle that nerve supplies
the muscle
• The motor branch leaves proximal to the muscle
• In limbs nerves passes between muscle planes
• This planes distinct morphological masses that
have fused together
Nerve supply of muscles
In limbs
• All the muscles are not supplied by plexus
• Flexor muscles are supplied by anterior
divisions
• Extensor muscles are supplied by
posterior divisions
Nerve supply of muscles
• Sensory supply
• In a nerve supply to a muscle contain 40%
of sensory nerve fiber
Nerve supply of muscles
• Certain cranial nerves are purely motor (iii, iv, vi,
vii, xii) supply ocular & facial muscles.
• Spinal accessory nerve also contain no sensory
fibres
• Sensory supply to those muscles are derived
from other adjacent nerves
– e.g. trigemial V
Physiology of muscle
• All skeletal muscle in the body except
heart is supplied by somatic nerves
– Voluntary muscles
• Heart & all smooth muscles are supplied
by autonomic nerves
– Involuntary muscles
Physiology of muscle
• Smooth muscles can elongate to greater
extend e.g. bladder
• Skeletal muscle cannot elongate 1/3 of
their resting length
Naming of Muscles
• The names given to individual muscles are
usually descriptive, based on
• their shape, size, number of heads or
bellies
• Position, depth, attachments, or actions
Naming of Muscles
The terms used according to the Shape
• Deltoid
(= triangular)
• Quadratus (= square)
• Rhomboid
(= diamond-shape)
• Teres
(= round)
• Gracilis
(= slender)
• Rectus
(= straight)
• Lumbrical
(= worm-like)
Naming of Muscles
The terms used according to the Size
• Major
(large)
• Minor
(small)
• Longus
(= long)
• Brevis
(=short)
• Latissimus
(= broadest)
• Longissimus
(= longest)
Naming of Muscles
The terms use according to the Number of
heads or bellies
• Biceps
(= 2 heads)
• Triceps
(= 3 heads)
• Quadriceps (= 4 heads)
• Digastric
(= 2 bellies)
Triceps
Digastric
Naming of Muscles
The terms used according to the Position
• Interosseus
(= between bones)
• Supraspinatus
(= above spine of scapula)
• Infraspinatus
(= below spine of scapula)
• Dorsi
(= of the back)
• Abdominis
(= of the abdomen)
• Pectoralis
(= of the chest)
• Brachii
(= of the arm)
• Femoris
(= of the thigh)
• Oris
(= of the mouth)
• Anterior , posterior,
Naming of Muscles
The terms used according to the Depth
• Superficialis (= superficial)
• Profundus
(=deep)
• Externus
(or external)
• Internus
(or internal)
Naming of Muscles
The terms used according to the
Attachment
• sternocleidomastoid (from sternum and
clavicle to mastoid process)
• coracobrachialis (from the coracoid
process to the arm)
Naming of Muscles
The terms used according to the Action
• Extensor , flexor
• Abductor , adductor
• Levator (= lifter), depressor
• Supinator , pronator
• Constrictor , dilator
Naming of Muscles
These terms are often used in combination:
E.G flexor digitorum longus (= long flexor of
the digits)
latissimus dorsi (= broadest muscle of the
back).
Pathology
• Hypertrophy
• Atrophy
• Paralysis
• Ischaemia
• Necrosis
Tendons
• Tendons are tissues that connect muscles to
bone, allowing the force of the muscles to move
the joints.
• Tendons consist of longitudinally arranged
collagen fibres
• Shape cylindrical or flat
• The aponeurosis of the abdominal wall muscles
are wide sheats of tendons
Tendons
• Blood supply is by two main sources
• Descending vessels from the muscles
• Periosteal vessels from the bone of
insertion
Tendons
• In long tendons an additional supply present
• From neighboring artery
• If you tear (rupture) or cut (sever) the tendon
anywhere along its route unable to move the
distal part
• Tendons are stretched tightly as they connect
the muscle to the bone. If the tendon tears, the
end must be sewn back together again (a
surgical repair)
Tendons
• Synovial sheaths
• Enclose tendons where the range of
movement is considerable
• e.g. the tendon in the fingers
• this is to reduce the friction
Tendons
Tendons
• Sheeth has two layers
– Parietal
– Visceral
• Parietal layer firmly attach to the
surrounding structures
• Visceral layer firmly fixed to the tendon
Tendons
• In between
• Thin layer of fluid lubricate the two layers
& facilitate movements
• The visceral & parietal layers fused each
other on one side
Tendons
• They do not enclose tendon cylindrically
• Tendon looks pushed into double layers of
enclosed sheath
• Blood vessels can enter the tendon
between this space
Tendons