By

Dr MB Samarawickrama(MBBS MS)

31th Batch July 2008

Muscles and Tendons

Muscles

Three types

• Skeletal Muscles

• Cardiac Muscles

• Smooth Muscles

MusclesNeed 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 musclesE.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 musclesBipennate 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 markingsFlat 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 musclesSynergic 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