Muscle as an organ

Muscle tissue vs. Muscle as an organ One of the 4 primary tissue types How many subtypes? Made up of 4 tissue types. > 700 skeletal muscles Word roots: sarco mys

Overview of Muscle Tissue Functions of muscle tissue –Movement –Maintenance of posture – enables the body to remain sitting or standing –Joint stabilization –Heat generation – muscle contractions produce heat Helps maintain normal body temperature

Types of Muscle Tissue Three types Skeletal muscle tissue – packaged into skeletal muscles, Cells are striated, voluntary Makes up 40% of body weight Cardiac muscle tissue – occurs only in the walls of the heart, striated, involuntary Smooth muscle tissue – occupies the walls of hollow organs. Visceral, no striations, involuntary

Similarities of Muscle Tissue Cells of skeletal and smooth muscles are known as fibers Muscle contraction depends on two types of myofilaments One type contains actin Another type contains myosin These two proteins generate contractile force Plasma membrane is called a sarcolemma Cytoplasm is called sarcoplasm

Basic Features of a Skeletal Muscle Connective tissue sheaths bind a skeletal muscle and its fibers together Epimysium –(overcoat) dense regular connective tissue surrounding entire muscle Perimysium – surrounds each fascicle (group of muscle fibers) Endomysium – a fine sheath of connective tissue wrapping each muscle cell Connective tissue sheaths are continuous with tendons

Gross Anatomy Each skeletal muscle is wrapped by 3 concentric layers of connective tissue.

myofilaments

Epi-, Peri-, and Endomysium Are interwoven - Go over into tendon Distinguish between: Tendon Aponeurosis Ligament

Basic Features of a Skeletal Muscle Muscle attachments –Most skeletal muscles run from one bone to another –One bone will move – other bone remains fixed –Origin – immovable or less movable bone that muscle moves toward when a muscle contracts –Insertion – Movable bone when a muscle contracts, moves towards origin

Muscle Terminology Origin stationary Insertionmoves Possible: multiple origins

Basic Features of a Skeletal Muscle Muscle attachments Muscles attach to origins and insertions by connective tissue Direct (fleshy) attachments – connective tissue fibers are short, epimysium of muscle is fused to the periosteum of a bone of perichondrium of a cartilage Indirect attachments – connective tissue forms a tendon or aponeurosis Bone markings present where tendons meet bones Tubercles, trochanters, and crests

Arrangement of Fascicles Parallel/Fusiform-long axis of fascicles run parallel to long axis of the muscle Pennate – fascicles short and attach obliquely Convergent – has broad origin and fascicles converge toward a single tendon Circular-fascicles arranged in concentric rings

Parallel Muscles Majority Spindle shaped with cord-like tendons

Convergent muscles Broad origin, pointed insertion

Pennate Muscles: Unipennate One or more tendons run though muscle body Fascicles in oblique angle to tendon Can generate more tension

Pennate Muscles: Bipennate & Multipennate Examples

Circular Muscles = Sphincters Concentric fibers adjust opening Examples: orbicularis occuli and oris

Types of Actions  flexion, extension  adduction, abduction  elevation, depression  rotation  pronation, supination

Grouping of Muscles according to Primary Action Agonist = Prime Mover Antagonist (action opposes agonist) Synergists = Assistants of prime mover

Naming the Skeletal Muscles Location –most often with regard to bone Shape– the deltoid is triangular Relative size - Maximus (largest), minimus (smallest), longus (long), and brevis (short), indicate size Direction of fascicles and muscle fibers -Name tells direction in which fibers run –Example – rectus (straight) abdominis and transversus or oblique abdominis Location of attachments – name reveals point of origin and insertion. Origin always named first! Example – brachioradialis,

Naming the Skeletal Muscles Number of origins – two, three, or four origins –Indicated by the words biceps, triceps, and quadriceps Action – the action is part of the muscle’s name Flexor, extensor, adductor, or abductor