INTRODUCTION TO MUSCLE TISSUE Learning objectives Definition Structure

INTRODUCTION TO MUSCLE TISSUE

Learning objectives • • • Definition Structure Properties Classification Functions.

Muscle Definition: collection of specialised cells with impt properties – contractility Elasticity Muscle – Muscle fibers blood vessels connective tissue nerve fibers

Properties of muscle Special property = contractility Plasmalemma = sarcolemma Cytoplasma = sarcoplasm Endoplasmic reticulum = sarcoplasmic reticulum

tissue ? group of cells morphologically similar & physiologically identical.

Muscle cells or myocyte – Features 1. Shape : long , narrow , cylinderical fibres 2. Fibres run parallel to axis of muscle. 3. Composed of smaller of thicker & thinner filaments

4. Made up of myoproteins = Actin , myosin , troponin Three kinds of muscle • Striated • Smooth • Cardiac

• • • Skeletal muscle / Voluntary/Striated Straight Unbranched They acts on the joint Reveals cross striations Structural Syncitium

• It is under the control of our will – voluntary • Nuclei towards periphery. • Light & dark band present -striped muscle

• Parts of voluntary muscle • Fleshy belly • Fibrous extension = tendon or aponeurosis

Classification of voluntary muscles 1. According to color= Red & White • • • Red More primitive Less cross striations More sarcoplasm Contraction is slow Found in deep muscles • Ex: extensors • • • White More recent More striations Less sarcoplasm Contraction is rapid Found in Superficial muscles • Ex: muscles for eye movement

2. Types of insertion of muscles

3. According to the direction of the muscle fibers a. Parallel b. Pennate c. Spiral d. Cruciate

a). Parallel muscles • The muscle fibers are parallel to line of pull • The fibers are long • Functions: • Range of movement • ↓ Power of action

Sub divisions of parallel muscles a). Strap muscles b). Quadrate muscles c). Fusiform muscles

• Strap muscles Ex: Sartorius Rectus abdominis

• Quadrate Quadratus lumborum • Fusiform muscle Biceps brachii

b) Pennate muscles • Fibers are oblique to line of pull b. 1 Unipennate Flexor pollicis longus Extensor digitorum longus Peroneus tertius

b. 2 Bipennate Rectus femoris Dorsal interossei of hand & foot

b. 3 Multipennate • A series of bipennate muscles lie side by side in one plane Acromial fibers of deltoid

B 4 Circumpennate • The muscle is cylindrical • Oblique fibers converge into central tendon from all sides Tibialis anterior

c) Spiral muscle • Muscles are twisted in arrangements close to their insertion ex- Pectoralis major & latissimus dorsi

• Cruciate muscle • Muscle fibers are arranged in sup and deep planes crossing like “X”

• • • Action of muscles Prime mover Antagonists Fixation muscles Synergists

TENDON: skeletal muscle & bundles of fibres is surrounded by connective tissue , at the end of muscle & is continued as tendon.

Aponeurosis ?

Antagonistic muscle ØDefinition : muscle on contraction brings opposite movements at the same joint

Øexample– a) contraction of biceps flexes the elbow joint whereas triceps brings expense elbow joint. b) Abductor draw the bone away from body Adductors brings bone towards the body c) sphinctor – constricts an opening d) dilator - dialates opening

• • • Structure of voluntary muscle Coverings Epimysium Perimysium Endomysium Each fasiculus is covered by endomysium

muscle Fasciculus Muscle fibers Myofibris Myofilaments of actin & mysoin

E M structure of skeletal muscle 1)Myofibrils composed of myosin (thick filaments) , actin & other proteins (thin filament) 2). Dark bands – A band 3). Lightband – I band 4). Center of A band – light – H band.

• H band is again bisect by M line. • Each I band has dark line the Z disc the portion of myofibril b/w two Z discs – sarcomere.

• • Sarcolemma Sarcoplasm Myofibrils Myofilaments

• Smooth muscle • Not under control of conscious mind • The action is sluggish

• Smooth muscle • Two types of smooth muscles • Multi unit muscle Contraction does not arise spontaneously • Ex: Muscles of iris and those of the wall of large arteries

• Single unit muscle • Contraction is spontaneous • Action is myogenic • Ex: are muscles of stomach, intestines, uterus, ureter and some of the small blood vessels

• Cardiac muscle

• Source of development : all from secondary mesoderma in origin. Ciliary muscle of eye & iris ----- ectodermal in origin. • Skeletal muscle – somatopleuric mesoderm • Cardiac muscle splanchnopleuric • Smooth muscle mesoderm.

Functions muscle tissue • To provide movement of skeleton & other organs. • Contraction • Storage of glycogen

Muscle contracts & relaxes but never expands Ø largest muscle – gluteus maximus Ø longest muscle – sartorious ØSmallest muscle – stapedius of middle ear