General myology. Function of the muscle tissue generation of movements stabilization of the position of the body control of the volume of the organs –smooth

General myology

Function of the muscle tissue

• generation of movements

• stabilization of the position of the body

• control of the volume of the organs– smooth muscle - sphincters

• motion of the substances in the body– blood, lymph, urine, air, food and fluids, sperm

• generation of body heat– voluntary and involuntary contractions of skeletal

striated muscle

Characteristics of the muscle tissue

• electrical irritability (excitability)– ability of the skeletal muscle to respond to stimuli

– skeletal muscle contracts as a result of nerve irritation

• contractility– ability of contraction

• extensibility– ability to extend without tissue damage

• elasticity– ability to return to the original shape after being extended

Types of the muscle tissue

• smooth muscle tissue

(textus muscularis levis)

• striated muscle tissue

(textus muscularis striatus)

• cardiac striated mucle tissue

(textus muscularis striatus cardiacus)

Smooth muscle tissue

• smooth muscle cell (myocytus levis)• nucleus is in the centre of the cell• in sarcoplasm there are longitudinally placed

contractable myofibrils made of myofilaments (myofilamenta)– myofilamentum crassum

– myofilamentum tenue

• even at rest it is in a mild contractile state – tonus• doesn´t become fatigued• inervated by automonic system is not under

voluntary control

Eis, Jelínek, Špaček, Histopatologický atlas, Praha 2006

Smooth muscle


Smooth muscle – electronmicroscopical picture

Skeletal striated muscle Imyofibre (myofibra)

• elementary structural unit• multinucleated• thickness: 10–100 µm• length: mm – cm• origin: merging of elongated mononuclear cells

(myoblasts) → myotubes (nuclei inside, myofibrils at the surface) → conversion to myofibres (nuclei at the surface, myofibrils inside)

• sarcolemma on the surface– striated in the microscope

• lighter and darker sections

Skeletal striated muscle II• myoglobin (pigment causing red colouring)

• fibres– quick

• quickly fatigued

• light (white)

• in superficial layers

– slow• more resistant to tiredness

• dark (red)

• in deeper layer

• inervated by cranial and spinal nerves– without inervation non-functional and atrophies

Myofilaments and sarcomeres

• thick (myosin) and thin (actin) myofilaments (myofilamenta) overlap so they create annealing

• sarcomere (sarcomerum)– contractile muscle units of skeletal and cardiac

muscle– reach from one Z-disc to another

http://www.baileybio.com/plogger/?level=picture&id=264 http://www.bms.ed.ac.uk/research/others/smaciver/Myosin%20II.htm


Skeletal striated muscle – longitudinal section


Skeletal striated muscle – transverse section

Cardiac striated muscle• microscopically looks like a net

• similar to skeletal muscle tissue

• fibres connected by diagonal plasmatic bridges

• intercalated disc (discus intercalaris)– divides cardiac muscle tissue into mononuclear segments

(cells)

• nucleus in the middle of the cell

• sarcolemma on the surface

• conducting system of the heart (complexus stimulans cordis)– modified cells of the cardiac muscle are specialized to generate

impulses and to conduct them


Cardiac muscle tissue


Cardiac muscle tissue

intercalated disc

Basic muscle structure I

• striated muscle fibres• special muscle structures• primary muscle bundle

– 10-100 fibres connected and covered by fibrous tissue

• secondary bundles– connection of primary bundles and covering by

fibrous tissue

• bundles of higher orders

Basic muscle structure II

• fibrous tissue– endomysium (perimysium internum)

• covers myofibres and bundles

– epimysium (perimysium externum) = fascia• covers the whole muscle

• tendon (tendo)• aponeurosis (aponeurosis)• myotendinous junction (junctio myotendinea)

– connection of myofibres with first (originating) and inserting tendon

Basic muscle structure III

• origin (origo)– mobile end (punctum fixum)

• head (caput musculi)

• belly (venter musculi)

• attachment (insertio)– fixed point (punctum mobile)

http://medicina.ronnie.cz/c-1349-Makroskopicka-stavba-svalu.html

origin

belly

insertion

External muscle shape• fusiform muscle (m. fusiformis)• two-headed muscle (m. biceps)• three-headed muscle (m. triceps)• four-headed muscle (m. quadriceps)• flat muscle (m. planus)• two-bellied muscle (m. biventer)• orbicular muscle (m. orbicularis)• pennate muscle (m. pennatus)

– semipennate muscle (m. semipennatus)

– multipennate muscle (m. multipennatus)

– diagonally directed bundles face towards the inserting tendon

Čihák R., Anatomie 1, Grada Publishing a.s. 2001

Muscle contraction

• velocity: in tens of miliseconds

• contraction– isotonic

• length changed, inner tonus unchanged

• concentric (shortening of a muscle)

• excentric (lengthening of a muscle)

– isometric• length unchanged, muscle belly tonus changed

• spasm – involuntary contraction of one muscle• cramp – painful spasm• tetanus – multiple spasms of skeletal muscles

• tic – involuntary twiches of muscles, usually under voluntary control

• tremor – rhythmical, involuntary contractions of opposite groups of muscles

• fasciculations – involuntary, short twiches on motor unit visible under the skin

• fibrilace – spontaneous contractions of fibres of one muscle that aren´t visible under the skin

Abnormal contraction

Function of a muscle I• agonists

– in the same direction acting muscles

• antagonists– counteracting muscles

• synergists– muscles participating in one movement (working

together)

• main (principal) muscle – one out of the group of synergists

• auxiliary (accesory) muscles– they act together with the principal muscle

Function of a muscle II

• fixative (stabilizing) muscles– firm up the part of the body, that causes the

movement

• neutralizing muscles– neutralize unwanted directions of movements

• one-jointed muscles– they´re causing the movement only in 1 joint

• double-jointed (multiple-jointed) muscles– they act mainly in the joint closest to the insertion

Function of a muscle III

• flexor (m. flexor)– makes the angle in the joint

more acute

• extensor (m. extensor)– makes the angle in the joint

more obtuse

• adductor (m. adductor)– moves the bone medially

• abductor (m. abductor)– moves the bone laterally

• rotator (m. rotator)– turns the bone around its long

axis

• levator (m. levator)– lifts up a part of the body

• depressor (m. depressor)– drops down a part of the body

• pronator (m. pronator)– helps with pronation

• supinator (m. supinator)– helps with supination

• opponens (m. opponens)– places the thumb against other

fingers

• sphincter (m. sphincter)

• dilator (m. dilatator)

Function of a muscle IV

• tonus– maintains the permanent tension of the muscle– maintains the correct position of the joints and

parts of the body– decreases in sleep and narcosis

• postural muscles– ensure upright posture of the body

Inervation of a muscle

• neurovascular hilus– point of entry for nerves and vessels into the muscle

• diploneural muscles– inervated by 2 peripheral nerves

• plurineural muscles– inervated by more nerves

• neural fibres– motor

– sensory

– autonomic (visceromotor)http://www.sciencedirect.com/science/article/pii/S1748681505004535

Motor inervation• somatomotor fibres are axons of motoneurons of

anterior spinal horns (α-motoneurons)• neuromuscular synapse (synapsis neuromuscularis)

– termination of an axon on the surface of myofibre

• motor unit– group of myofibres inervated by 1 motoneuron

– simple, rough movements – big motor unit (150 myofibres)

– delicate, precise movements – small motor unit (8–15 myofibres)

Richard S. Snell, Clinical Anatomy, Lippincott Wiliams & Wilkins 2004 Gray´s anatomy, 35th British edition, W.B.Saunders Company Philadelphia 1973

Muscle spindleFusus neuromuscularis

= intrafusal muscle fibres• specialized organ of perception in the muscle =

proprioception• consists of several myofibres• surrounded by fibrous capsule• inervated by fibres of γ-motoneurons

– informations about length change to the spinal cord

• detects also difference of grade of contraction of extra– and intrafusal fibres

doc. MUDr. Josef Zámečník, Ústav patologie a molekulární medicíny 2.LF UK a FN v Motole

Muscle spindle – transverse section

doc. MUDr. Josef Zámečník, Ústav patologie a molekulární medicíny 2.LF UK a FN v Motole

Muscle spindle – transverse section

Fig. 14-5. Neuromuscular spindle. Cross section. Juxta-equatorial region. Front leg muscle. Newborn rat. E.M. x1900. 1. Extrafusal skeletal muscle fibers. 2. Lumen of capillary. 3. Outer capsule. 4. Periaxial space. 5. Inner capsule. 6. Myelinated nerve fibers. 7. Nuclear chain muscle. 8. Nuclear bag muscle fibers.

J.A.G. Rhodin: Histology. A text and atlas. 1974

Fig. 14-4. Neuromuscular spindle. Cross section. Equatorial region. Triceps surae muscle. Rat embryo, 2 days before birth. E.M. x1200. (From: J.H. Levy, 1972) 1. Extrafusal skeletal muscle fibers. 2. Lumen of blood capillary. 3. Outer capsule. 4. Periaxial space. 5. Inner capsule. 6. Myelinated nerve fibers. 7. Intrafusal nuclear chain muscle fibers. 8. Nuclear bag muscle fibers. 9. Fibroblasts. 10. Loose connective tissue.


Fig. 14-6. Neuromuscular spindle. Cross section. Juxta-equatorial region. Enlargement of rectangle in Fig. 14-5. E.M. x4500. 1. Part of extrafusal muscle fiber. 2. Lumen of capillary. 3. Sheet-like cells of outer capsule. 4. Myelinated nerve fibers. 5. Periaxial space. 6. Inner capsule. 7. Nucleus of fibroblast. 8. Nucleus of Schwann cell. 9. Nucleus of nuclear bag fiber. 10. Polar ends of nuclear chain fibers. 11. Satellite muscle cell. 12. Sensory nerve endings.

Fig. 14-7. Sensory nerve ending. Neuromuscular spindle. Enlargement of rectangle in Fig. 14-6. E.M. x60,000. 1. Myofilaments of intrafusal nuclear chain muscle fiber. 2. Sensory nerve ending. 3. Mitochondria. 4. Membranous contact between sarcolemma and cell membrane of nerve ending. 5. Zonula adherens junction. 6. External (basal) lamina.


Fig. 14-18. Motor nerve endings. Skeletal muscle. Gold chloride method. Human. L.M. x200. 1. Striated muscle fibers. 2. Bundle of myelinated nerve fibers. 3. Motor end plates.

Fig. 14-19. Motor end plates. Gold chloride method. Skeletal muscle. Human. L.M. x600. 1. Efferent nerve fibers. 2. Motor end plate in surface view. 3. Motor end plate in side view. 4. Striated skeletal muscle fibers.

Fig. 14-20. Motor end plate. Skeletal muscle. Enlargement of area approximately similar to rectangle in Fig. 14-19. Rat. E.M. x30,000. 1. Efferent nerve process (axon). 2. Myelin sheath. 3. Successive laminae of the myelin sheath terminate as cytoplasmic swellings. 4. Cytoplasm of Schwann cell (neurolemma). 5. Endoneurial connective tissue. 6. Cytoplasm of teloglial cell (Schwann cell). 7. Axon terminal end (end knob). 8. Synaptic trough (recess). 9. Mitochondria. 10. Subneural, synaptic clefts. 11. Nucleus of skeletal muscle cell. 12. Myofibrills. 13. External (basal) lamina.


Fig. 14-21. Detail of motor end plate. Skeletal muscle. Rat. E.M. x60,000. 1. Axon terminal. 2. Cytoplasm of muscle cell (sole plate). 3. Mitochondria. 4. Flat synaptic vesicles. 5. Round synaptic vesicles. 6. Presynaptic membrane. 7. Synaptic cleft with glycoprotein material. 8. Postsynaptic, junctional folds. 9. Subneural primary and secondary clefts. 10. Postsynaptic sarcolemma. 11. Synaptic vesicles fusing with presynaptic membrane. 12. Microtubules. 13. Ribosomes.

Figs. 14-22. and 14-23. Detail of synaptic junctions of motor end plate. Skeletal muscle. Rat. E.M. x124,000. 1. Presynaptic cell membrane of axon terminal. 2. Synaptic cleft. 3. Postsynaptic sarcolemma. 4. Round (excitatory?) electron-lucent, synaptic vesicles, bounded by a delicate, trilaminar membrane. 5. Flat (inhibitory?) synaptic vesicles.

Vascular supply of a muscle

• entry and exit of the vessels in muscle neurovascular hilus

• flowing blood volume depends on the activity of the muscle

• poor supply for the tendons – blood and lymph vessels of their own– branches of the vessels for the muscle,

periosteum, tendons

Growth and regeneration of a muscle

• lengthwise growth– growth of length of myofibres at their ends

• widthwise growth– myofibres are getting thicker

• from birth the amount of myofibres is unchanged

• cells are not regularly renewed regeneration practically can´t occur

Special muscle structures I

• fascia (= perimysium externum)– fibrous envelope of muscle or muscle group

– barrier for spreading of inflammation in that specific area

• osteofascial septum (= septum osteofasciale)– fascial divider from the superficial fascia to

the periosteum

– separates the space for muscle groups – compartment (compartimentum)

https://www2.aofoundation.org/wps/portal/!ut/p/c0/

Compartment syndrome• in the first hours after injury of the muscle or fractures of

the long bones of the thigh, leg, arm or forearm

• increase of pressure in the fascial space (intramuscular bleeding, oedema) → compression of the vessels → ischemia with possible necrosis

• treatment is mostly surgical – fasciotomy or dermatofasciotomy – fascial incision (together with skin) for decreasing the pressure in the

fascial space

• Volkmann´s contracture– flectional contracture of the hand and fingers as a result of postischemic

fibrous degeneration of muscle bellies of the flexors, sometimes also extensors

Fasciotomy

http://lifeinthefastlane.com/ortho-library/compartment-syndrome/

Special muscle structures II• tendon (tendo)

– strip of tough fibrous connective tissue composed of bundles of collagenous fibrils

– connects the muscle to the bone

– peritenonium internum (covers the bundles)

– peritenonium externum (consistent envelope on the surface of the tendon)

• aponeurosis (aponeurosis)– flat tendon

– mutually crossing bundles in layers

• tendinous sheath (vagina tendinum)– space along the tendon lined by synovial membrane

– vagina fibrosa: surrounds the vagina synovialis, holds the tendons to the bone

– vagina synovialis• epitenonium: inner layer (covers the tendon)

• peritenonium: outer layer

• mesotenonium: mutual switching of both previous things

http://www.zoology.ubc.ca/~biomania/tutorial/bonejt/jt01ac03.htm

Special muscle structures III• bursae mucosae

– pouches in the vincinity of the joints, tendons and muscles

– lined by synovial membrane, filled up with synovial fluid

– reduction of rubbing in places exposed to considerable movement and pressure

• retinacula– strengthened stripes of the superficial fascia

– tie the inserting tendons to the bone

– together with the skeleton create osteofibrous canal

• vincula– mesotenonium of tendinous sheaths of the flexors of the hand

– vascular supply for corresponding tendons run through them

– vincula brevia et longa

http://www.msdlatinamerica.com/ebooks/SurgicalExposuresinOrthopaedicsTheAnatomicApproach/sid139333.htmlhttp://www.blackburnfeet.org.uk/hyperbook/trauma/ankleFx/ankleFxBasic1.htmhttp://medical-dictionary.thefreedictionary.com/bursa

Development – muscles of the trunk

• from dermatomyotoms (part of the somites)– epaxial unit

• maintains the segmental arrangement

• inervation: posterior rami of the spinal nerves

• deep muscles of the back

– hypaxial unit• merges into larger units

• inervation: anterior rami of the spinal nerves

• lateral and anterior muscles of the body wall

– border: fascia thoracolumbalis – lamina media

Myoseptum horizontale

http://en.wikipedia.org/wiki/Epaxial_and_hypaxial_muscles

http://www.sharksinfo.com/lateral-line.html

Development – muscles of the limbs

• migration of hypaxial myogenic cells from ventrolateral margin of the dermatomyotom to the limb bud

• secondary extension of the beginnings to the trunk– spinohumeral muscles

– thoracohumeral muscles

• inervation: anterior rami of the spinal nerves– form the plexuses

• plexus brachialis (brachial plexus) – C5-8, T1

• plexus lumbalis (lumbar plexus) – T12, L1-4

• plexus sacralis (sacral plexus) – L4-5, S1-3

EMG (electromyography)• detection of the superficial muscle or the intramuscular

activity

• detects the change of electrical potential

• diagnostics for various muscle and neural malfunctions

http://biomech.ftvs.cuni.cz/pbpk/kompendium/biomechanika/experiment_metody_emg.php

http://www.fsps.muni.cz/inovace-SEBS-ASEBS/elearning/biomechanika/vyzkumne-metody-v-biomechanice

Functional muscle test

• informs us about the muscle strength

• helps to assess the extent and location of the impairment

• analysis and examination of performance for the whole movement

• assessment – 6 grades• 0 – no sign of contraction

• 1 – twich (not enough to do the move)

• 2 – very weak (movement in the whole extent, doesn´t overcome the resistance of the tested part of the body)

• 3 – weak (overcomes the gravity)

• 4 – good (overcomes medium-sized outer resistance)

• 5 – normal (very good function)

Rigor mortis• is state of muscle rigidity, that begins 3-4 hours after

death and lasts approx. 24 hours• after death Ca2+ ions leave the sarcoplasmatic

reticulum and enable the myosin heads to bond to the actin fibres

• since the synthesis of ATP has ceased, actin bridges don´t separate until the time when proteolytic enzymes start to eliminate the cells

http://tincconsconwa.blogspot.cz/2010/01/rigor-mortis.html

• skeletal muscle tissue starts to be replaced by fibrous and fatty tissue around the age of 30

• reflexes slowdown, loss of flexibility and decrease of strength

• change of muscle fibres from quick to slow

Growing old and musle tissue

Enthesopathy

• illness of muscle and tendinous insertions

• usually caused by repeated overstraining

• e.g. tennis elbow

http://www.fyzioterapie-stepankavojtova.cz/bolestivyloket.htmlhttp://compex.zdravi-cz.eu/tenisovy-loket.php

Documents

General myology. Function of the muscle tissue generation of movements stabilization of the position of the body control of the volume of the organs –smooth