INTRODUCTION TO MYOLOGY Kaan Ycel M.D., Ph.D. Painting by Danny Quirk 23.February.2014 Monday
myology interested in all the muscles in the body Musculus (muscle) mus-mouse; musculus- little mouse. So called because the shape and movement of some muscles (notably biceps) were thought to resemble mice. If you bend and straighten your arm at the elbow, you should see the front of the upper arm move under the skin. To the ancient Romans this movement resembled a little mouse scurrying
beneath the skin. Skeletal muscles move the skeleton, as a result the body. Types of Muscles based on distinct characteristics Functional voluntary vs. involuntary
Histological striated vs. smooth or unstriated Anatomical (location) @ body wall (soma) and limbs @ hollow organs (viscera) or blood vessels Skeletal striated muscle
voluntary somatic muscle gross skeletal muscles that compose the muscular system moving or stabilizing bones and other structures (e.g., the eyeballs). Innervated by the somatic nervous system. Cardiac striated muscle involuntary visceral muscle forms the walls of the heart and adjacent parts of the great vessels. pumps blood.
Smooth muscle (unstriated muscle) involuntary visceral muscle forms part of the walls of most vessels and hollow organs (viscera) moving substances through them coordinated sequential contractions (pulsations or peristaltic contractions). Innervated by the autonomic nervous system.
FEATURES OF SKELETAL MUSCLES HEAD OR BELLY fleshy, reddish, contractile portions TENDON white non-contractile portions composed mainly of organized collagen bundles, that provide a means of attachment. Most skeletal muscles attach to Directly or indirectly to bones Cartilages
Ligaments Fascias or combinations of the ones above Some to organs (eyeball)/skin (facial muscles)/mucous membranes(intrinsic tongue muscles) Muscles are organs of locomotion (movement) also: provide static support
give form to the body provide heat Some tendons form flat sheets aponeuroses anchor the muscle to the skeleton to deep fascia to aponeurosis of another muscle
Many terms provide information about a structure's Shape Size Location Function Resemblance of one structure to another Basis of function Bones attached to
Abductor digiti minimi muscle abducts the little finger. Sternocleidomastoid muscle (G. kleidos, bolt or bar, clavicle) attaches inferiorly to the sternum and clavicle and superiorly to the mastoid process of the temporal bone of the cranium. Levator scapulae elevates the scapula (L. shoulder blade). Descriptive names Deltoid muscle
triangular, like the symbol for delta, the fourth letter of the Greek alphabet. -oid like; deltoid means like delta. Position medial, lateral, anterior, posterior Length
brevis, short; longus, long Shape piriformis muscle pear shaped (L. pirum, pear + L. forma, shape or form). Location temporalis muscle in the temporal region (temple) of the cranium (skull).
CLASSIFICATION OF MUSCLES according to their shapes Flat parallel fibers often with an muscles aponeurosis
External oblique muscle broad flat muscle Sartorius narrow flat muscle with parallel fibers longest muscle in the body Pennate muscles
feather-like (L. pennatus, feather), arrangement of fasicles Unipennate Extensor digitorum longus Bipennate Rectus
femoris Multi-pennate Deltoid Fusiform muscles spindle shaped with a round, thick belly (or bellies) and
tapered ends Convergent muscles arise from a broad area converge to form a single tendon Quadrate
muscles four equal sides (L. quadratus, square) rectus abdominis between its tendinous intersections. Circular or sphincteral surround amuscles
body opening or orifice, constricting it when contracted orbicularis oculi closes the eyelids Multi-headed or multi-bellied muscles more than one head of attachment or more than one contractile belly
Biceps muscles two heads of attachment triceps muscles three heads Two bellies digastric muscle gastrocnemius muscle
CONTRACTION OF MUSCLES Skeletal muscles function by contracting they pull and never push. When a muscle contracts and shortens one of its attachments usually remains fixed the other attachment (more mobile) pulled toward it movement
Attachments of muscles origin & insertion Origin proximal end of the muscle remains fixed during muscular contraction. Insertion distal end of the muscle movable This is not always the case. Some muscles can act in both directions under
different circumstances. Reflexive Contraction automatic (reflexive) contraction, not voluntarily controlled Respiratory movements of the diaphragm Myotatic reflex
Functions of muscles Prime mover (agonist) main muscle responsible for producing a specific movement of the body. Does most of the work (expending most of the energy) required. In most movements, there is a single prime mover, but some movements involve two prime movers working in equal measure.
Fixator steadies the proximal parts of a limb through isometric contraction while movements are occurring in distal parts. Synergist complements the action of a prime mover. Usual to have several synergists assisting a prime mover in a particular movement.
Antagonist a muscle that opposes the action of another muscle. A primary antagonist directly opposes the prime mover, synergists may also be opposed by secondary antagonists. The same muscle may act as a prime mover, antagonist, synergist, or fixator under different conditions.
Nerves and arteries to muscles Variation in the nerve supply of muscles is rare; it is a nearly constant relationship. In the limb, muscles of similar actions are generally contained within a common fascial compartment and share innervation by the same nerves. Nerves and arteries to muscles
Nerves supplying skeletal muscles (motor nerves) usually enter the fleshy portion of the muscle (vs. the tendon), almost always from the deep aspect (so the nerve is protected by the muscle it supplies). The blood supply of muscles is not as constant as the nerve supply and is usually multiple. Fascia (L. fasciae) wrapping, packing, and insulating materials of the deep structures of the body
Underlying the subcutaneous tissue superficial fascia Deep fascia dense, organized connective tissue layer, devoid of fat covers most of the body deep to the skin and subcutaneous tissue In the limbs, groups of muscles with similar functions sharing the same nerve supply are located in fascial compartments, separated by thick sheets of deep fascia, called intermuscular septa, that extend centrally
from the surrounding fascial sleeve to attach to bones. These compartments may contain or direct the spread of an infection or a tumor.
