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General Myology

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General Myology General myology © David Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 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) © David Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 Smooth muscle © David Kachlík 30.9.2015 Eis, Jelínek, Špaček, Histopatologický atlas, Praha 2006 Smooth muscle – electronmicroscopical picture © David Kachlík 30.9.2015 Eis, Jelínek, Špaček, Histopatologický atlas, Praha 2006 Skeletal striated muscle I myofibre (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 © David Kachlík 30.9.2015 • 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 © David Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 © David Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 Eis, Jelínek, Špaček, Histopatologický atlas, Praha 2006 Skeletal striated muscle – transverse section © David Kachlík 30.9.2015 Eis, Jelínek, Špaček, Histopatologický atlas, Praha 2006 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© David Kachlíkthem 30.9.2015 Cardiac muscle tissue © David Kachlík 30.9.2015 Eis, Jelínek, Špaček, Histopatologický atlas, Praha 2006 Cardiac muscle tissue intercalated disc © David Kachlík 30.9.2015 Eis, Jelínek, Špaček, Histopatologický atlas, Praha 2006 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© David orders Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 Basic muscle structure III • origin (origo) – mobile end (punctum fixum) • head (caput musculi) origin belly • belly (venter musculi) • attachment (insertio) insertion – fixed point (punctum mobile) http://medicina.ronnie.cz/c-1349-Makroskopicka-stavba-svalu.html © David Kachlík 30.9.2015 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 David Kachlík face 30.9.2015 towards the inserting tendon © David Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 Abnormal contraction • 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 © David Kachlík 30.9.2015 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© David the Kachlík principal 30.9.2015 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 © David Kachlík 30.9.2015 Function of a muscle III • flexor (m. flexor) • levator (m. levator) – makes the angle in the joint – lifts up a part of the body more acute • depressor (m. depressor) • extensor (m. extensor) – drops down a part of the body – makes the angle in the joint • pronator (m. pronator) more obtuse – helps with pronation • adductor (m. adductor) • supinator (m. supinator) – moves the bone medially – helps with supination • abductor (m. abductor) • opponens (m. opponens) – moves the bone laterally – places the thumb against other • rotator (m. rotator) fingers – turns the bone around its long • sphincter (m. sphincter) axis © David Kachlík• 30.9.2015dilator (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 © David Kachlík 30.9.2015 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 © David Kachlík 30.9.2015 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) © David Kachlík 30.9.2015 © David Kachlík 30.9.2015 Richard S. Snell, Clinical Anatomy, Lippincott Wiliams & Wilkins 2004 Gray´s anatomy, 35th British edition, W.B.Saunders Company Philadelphia 1973 Muscle spindle Fusus 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 © David Kachlík 30.9.2015 Muscle spindle – transverse section doc. MUDr. Josef Zámečník,© David Ústav patologie Kachlík a molekulární 30.9.2015 medicíny 2.LF UK a FN v Motole Muscle spindle – transverse section doc. MUDr. Josef Zámečník,© David Ústav patologie Kachlík a molekulární 30.9.2015 medicíny 2.LF UK a FN v Motole 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
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