Naming Muscles Skeletal muscles are named according to certain criteria A. Location- may indicate bone or body region that muscle is associated with Ex. Zygomaticus- associated with the zygomatic arch in the skull B. Shape- Muscles often have a definitive shape, after which they are name Ex. Deltoid means triangle (and the deltoid muscle is triangular) C. Relative Size 1. Maximus= largest 2. Minimus= smallest 3. Longus= long 4. Brevis= short Ex. Gluteus maximus (larger) and minimus (smaller)

Naming Muscle D. Direction of Muscle Fibers - may reflect the direction of the fibers in relation to midline or other axis 1. Rectus= straight (runs parallel) 2. Transversus/oblique ( right angles)/ obliquely Ex. Rectus femoris- muscle that runs parallel with the femur E. Number of Origins 1. Biceps= two origins 2. Triceps= three origins 3. Quadriceps= four origins Ex. Biceps Brachii F. Location of origin and insertions 1. may be named according to the attachment points 2. Origin is always named first Ex. Sternocleidomastoid (dual origin on sternum and clavicle; insertion on mastoid process

Naming Muscle G. Action 1. Uses words such as flexor, extensor, or adductor Ex. Adductor longus on thigh adducts the thigh H. Sometimes several criteria are combined in a name. Ex. Extensor carpi radialis longus 1. muscle’s action (extensor) 2. joint it acts on (carpi= wrist) 3. Where it is (radialis = radius of forearm) 4. size (long relative to other wrist muscles

Criteria for Naming Muscles Location (region or bone) Action (flexor carpi radialis) Number of attachments (biceps brachii) Shape (trapezius) Size (longus, maximus, minimus) Directions of fibers (obliques-diagonal)

IMPORTANT things about MUSCLES Attach to bone by tendon or aponeurosis MUST CROSS a joint MUST have two attachments Can affect the shape of the bone ALWAYS “pull” and get shorter (contract) Work in opposing pairs Example: biceps and triceps Have striations in the direction of their movement

Naming Muscle II. Muscle Interactions- four functional groups A. Prime mover- provide the major force for producing a specific movement. Also called the agonist Ex. Biceps Brachii for forearm flexion B. Antagonist- oppose or reverses a particular movement Ex. Triceps brachii for forearm extension (oppose biceps) C. synergist- aid agonist (prime movers) by promoting the same movement or reducing undesireable or unnecessary movements that might occur as the prime mover contracts. Ex. Semimembranosis helps the biceps femoris with thigh extension and knee flexion

Naming Muscle D. Fixators- a synergist that immobilizes or stabilizes a bone or a muscle’s origin Ex. Rotator cuff muscles (terest minor, infraspinatus, supraspinatus, subscapularis) E. Example of movement of all four involved in a movement a. prime mover= pectoralis major (shoulder flexion) b. antagonist= lattisimus dorsi c. synergist= biceps brachii d. fixator= rotator cuff

Naming Muscle III. Muscle Movements- Muscles move toward their origin from the insertion of the muscle. Origin is the bone point that does not move and the insertion is the bone attachment that does move. Ex. Origin- sternum and clavicle Insertion- mastoid Muscle when it contracts pulls the mastoid (skull) down toward the sternum and clavicle (bringing your head toward your chest) A. Flexion- bending movement that brings two articulating bones closer together. B. Extension- reverse of flexion, moves the bones further apart. Joint animations

Naming Muscle C. Abduction- movement of limb away from the mid-line D. adduction- movement of limb toward the mid-line. E. Circumduction- moving a limb so it describes a cone in space F. Rotation- turning of a bone on its long axis, this also includes lateral and medial rotation of hip and shoulder G. Supination- palm up H. Pronation palm down

Naming Muscle