Chapt. 11 Muscle Tissue Phyl 141

Origin

Definition: The muscle attachment point that does not move; the anchor point for the muscle. Function: Gives the muscle a stable base to pull against.

Insertion

Definition: The muscle attachment point that moves toward the origin. Function: Muscles move the bone or object at the insertion toward the origin.

Prime mover (agonist)

Definition: The main muscle responsible for a specific movement. A muscle can be the prime mover for more than one action. Function: Produces the main force for the movement.

Antagonist

Definition: A muscle that does the opposite action of another muscle (e.g., the antagonist of a flexor is an extensor). Function: Opposes and controls the agonist's movement.

Synergist

Definition: A muscle that helps the prime mover do the same action. Function: Assists the prime mover.

Fixator

Definition: A muscle that holds a specific bone or body part in place. Function: Stabilizes a bone so the prime mover can act on it.

Agonist/antagonist pairs

Definition: Biceps brachii (anterior arm) and triceps brachii (posterior arm); hamstrings (posterior thigh) and quadriceps femoris (anterior thigh); flexor digitorum superficialis/profundus (anterior forearm) and extensor digitorum (posterior forearm). Function: Biceps flexes the forearm and triceps extends it; hamstrings flex the leg and quadriceps extend it; the finger flexors flex the fingers and wrist and the extensor digitorum extends them.

Muscle action naming

Definition: Muscle actions are named "object/joint" + "movement". Example: biceps brachii = forearm flexion = elbow flexion = humeroulnar joint flexion. Function: Gives a consistent way to describe what a muscle does.

Fascicle arrangement types

Definition: Parallel (biceps brachii; rectus abdominis with tendinous bands), wrapping (supinator), convergent (pectoralis), pennate (unipennate: extensor digitorum; bipennate: rectus femoris; multipennate: deltoid), circular (orbicularis oris). Function: The pattern of fascicles determines how the muscle pulls.

Levers (1st, 2nd, 3rd class)

Definition: First class: fulcrum between the applied force and the load (pry bar; splenius capitis and semispinalis capitis). Second class: load between the applied force and the fulcrum (wheelbarrow; gastrocnemius). Third class: applied force between the load and the fulcrum (tongs; biceps brachii). Function: Explains how muscles, bones, and joints work together to move a load.

Latin and Greek roots in muscle names

Definition: ad = to/toward; ab = away from; sub = under; ductor = something that moves; anti = against; epi = on top of; apo = to the side of; longissimus = longest; longus = long; brevis = short; maximus = large; medius = medium; minimus = tiny/little; rectus = straight; multi = many; uni = one; bi/di = two; tri = three; quad = four; externus = outside; internus = inside. Function: Lets you decode muscle names to guess their shape, size, location, or action.

Sternocleidomastoid (SCM)

Definition: Neck muscle named for its three attachment points: sternum, clavicle, and mastoid process (temporal bone). Function: Neck flexion. One SCM = lateral neck flexion; two SCMs together = neck flexion.

Scalene

Definition: Neck muscles (3 uneven muscles; name means uneven) that attach cervical vertebrae to ribs. Function: Synergist for neck flexion and lateral neck flexion; also helps with breathing.

Splenius

Definition: Neck muscle attaching the nuchal ligament/occipital bone to the spine. Function: Head and neck extension.

Trapezius

Definition: Named for its trapezoid shape. Attaches skull, spine, spine of scapula, and clavicle. Function: Moves the scapula (retraction, elevation, depression).

Rhomboid (major and minor)

Definition: Named for its rhomboid shape; has a major and minor version. Attaches scapula to spine. Function: Scapular retraction.

Levator scapulae

Definition: Named for elevating the scapula. Attaches scapula to spine. Function: Elevates the scapula.

Deep back muscles

Definition: Erector spinae (3 muscles: semispinalis, longissimus, spinalis), interspinales (between spinous processes), intertransversarii (between transverse processes), and multifidus (one of the thickest muscles of the spine and lumbar region). Function: All either extend the spine/trunk or laterally flex the trunk/spine.

Rectus abdominis

Definition: Named for being a straight (rectus) abdominal muscle. Attaches xiphoid process and pubic bone. Function: Flexes the trunk/spine.

External and internal obliques

Definition: Named for being diagonal (oblique) abdominal muscles. The internal oblique is deep to the external oblique. External oblique fibers run medially inferiorly; internal oblique fibers run laterally inferiorly. Function: Laterally flex the trunk and small rotation.

Transverse abdominis (transversus abdominis)

Definition: Named for being opposite (transverse) to the rectus abdominis; deep to the internal oblique. Function: Compresses the abdomen.

Diaphragm

Definition: Muscle attaching sternum, ribs, and spine. Function: Pushes organs inferiorly to help breathing.

Intercostals

Definition: Named for being between (inter) the ribs (costal). Three types from superficial to deep: external, internal, innermost. Fiber orientation matches the external and internal obliques. Function: Elevate and depress the ribs for breathing.

Pectoralis major

Definition: Named for being the big muscle of the pectoral region. Attaches sternum/ribs/clavicle to the intertubercular groove of the humerus. Function: Arm flexion, medial rotation of the arm, and arm adduction.

Pectoralis minor

Definition: Named for being the small muscle of the pectoral region. Attaches ribs to the coracoid process. Function: Moves the scapula (depresses it).

Deltoid

Definition: Named for being triangular. Attaches clavicle/scapula to humerus. Function: Arm abduction.

Latissimus dorsi

Definition: Named for being the broad (latissimus) back (dorsi) muscle. Attaches lumbar spine to the intertubercular groove of the humerus. Function: Extends the arm, medially rotates the arm, and adducts the arm.

Serratus anterior

Definition: Attaches ribs to scapula. Function: Moves the scapula (depresses it) and acts as a fixator for the scapula.

Winged scapula syndrome

Definition: Condition in which the nerve to the serratus anterior is damaged (e.g., during mastectomy), so the muscle no longer works as a fixator. Function (of the muscle lost): Serratus anterior normally holds the scapula against the body; without it the scapula sticks out.

Rotator cuff muscles (SITS)

Definition: Supraspinatus, Infraspinatus, Teres minor, Subscapularis. Named for the fossae they sit in: supraspinous fossa, infraspinous fossa, lateral border, subscapular fossa. Function: Move the arm and stabilize the glenohumeral (GH) joint.

Subscapularis

Definition: Rotator cuff muscle in the subscapular fossa. Function: Medial rotator of the arm and GH joint stabilizer.

Supraspinatus

Definition: Rotator cuff muscle named for being above (supra) the spine (spinatus) of the scapula. Function: Arm abduction and GH joint stabilization.

Infraspinatus

Definition: Rotator cuff muscle named for being below (infra) the spine (spinatus) of the scapula. Function: Lateral rotation of the arm and GH joint stabilization.

Teres minor

Definition: Rotator cuff muscle on the lateral border of the scapula; synergist of infraspinatus. Function: Lateral rotation of the arm and GH joint stabilization.

Teres major

Definition: Attaches scapula to the intertubercular groove of the humerus; synergist of latissimus dorsi. Function: Extends the arm, medially rotates the arm, and adducts the arm.

SLAP tear

Definition: Superior Labral tear from Anterior to Posterior; a tear of the glenoid labrum that often affects the tendon of biceps brachii. Function: The glenoid labrum deepens the glenoid fossa to help stabilize the shoulder joint.

Biceps brachii

Definition: Named for having two (bi) heads (long and short) on the arm (brachii). Attaches coracoid process/head of humerus to radius. Function: Forearm flexor.

Brachioradialis

Definition: Named for attaching humerus and radius. Function: Forearm flexor (synergist).

Brachialis

Definition: Named for being an arm muscle. Attaches humerus to ulna; deep to biceps brachii. Function: Forearm flexor (synergist).

Triceps brachii

Definition: Named for having three heads (long, lateral, medial) on the arm. Attaches scapula/humerus to the olecranon of the ulna. Function: Forearm extender.

Pronator teres

Definition: Named for being a diagonal (teres) pronator. Attaches medial epicondyle of the humerus to radius. Function: Forearm pronator.

Flexor carpi radialis and flexor carpi ulnaris

Definition: Named for flexing the wrist. Attach medial epicondyle of the humerus to carpal bones. Function: Wrist flexors.

Flexor digitorum superficialis (FDS)

Definition: Named for being the superficial digit flexor. Attaches medial epicondyle to the middle phalange. Function: Flexes the joint between the proximal and middle phalanges.

Flexor digitorum profundus (FDP)

Definition: Named for being the deep (profundus) digit flexor. Attaches medial epicondyle to the distal phalange. Function: Flexes the joint between the distal and middle phalanges.

Ulnar collateral ligament injury (Tommy John surgery)

Definition: Injury to the ulnar collateral ligament on the medial side of the elbow; treated with ulnar collateral ligament reconstruction (Tommy John surgery). Function: The ulnar collateral ligament stabilizes the elbow joint.

Extensor digitorum

Definition: Named for extending the fingers. Attaches lateral epicondyle of the humerus to the fingers. Function: Extends fingers 2-5.

Extensor digiti minimi

Definition: Named for extending the 5th finger. Attaches lateral epicondyle of the humerus to the 5th digit. Function: Extends the 5th digit.

Extensor carpi ulnaris

Definition: Named for extending the wrist on the ulnar side. Attaches lateral epicondyle of the humerus to carpal bones. Function: Wrist extender.

Extensor carpi radialis longus and brevis

Definition: Named for extending the wrist on the radial side. Attach lateral epicondyle of the humerus to carpal bones (ECRL starts above the lateral epicondyle). Function: Wrist extenders.

Lateral epicondylitis (tennis elbow)

Definition: Condition affecting the lateral epicondyle of the humerus, where the wrist and finger extensors attach. Function (of the muscles involved): The forearm extensors extend the wrist and fingers.

Extensor indicis

Definition: Forearm muscle you need to know the function of but not recognize. Function: Extends the 2nd digit.

Supinator

Definition: Forearm muscle you need to know the function of but not recognize. Function: Supinates the forearm.

Opponens pollicis

Definition: Hand muscle you need to know the function of but not recognize. Function: Opposition of the thumb and 5th finger.

Endoplasmic reticulum

Definition: A bunch of tubes in the cell. Function: In muscle cells it is called the sarcoplasmic reticulum and stores calcium for contraction.

Thin filament

Definition: Filament made of actin; anchored at the Z-disc. Function: Is pulled inward by myosin to shorten the sarcomere.

Thick filament

Definition: Filament made of myosin; held together at the M line. Function: Myosin heads bind actin and pull the thin filaments inward.

Zone of overlap

Definition: Region of the A band where thin and thick filaments overlap; its size changes with contraction. Function: Where cross-bridges form, so it determines how much tension the sarcomere can make.

Cross-bridge

Definition: A myosin head bound to an active site on actin. Function: Links the filaments so the power stroke can pull actin inward.

Sarcomere length: ideal length

Definition: About 80% to 120% of resting length. Function: Produces maximum tension (tension = strength).

Sarcomere length: decreased length

Definition: Below 80% of resting length; the zone of overlap increases until the thin filaments have nowhere else to go. Function: Strength is decreased.

Sarcomere length: length increases too much

Definition: Above 120% of resting length; the zone of overlap shrinks until no overlap occurs. Function: Tension is reduced because of the lack of connection, and there is no tension with no overlap.

Erector spinae

Definition: Deep back muscle group of 3 muscles: semispinalis, longissimus, and spinalis. Function: Extend the spine/trunk or laterally flex the trunk/spine.

Interspinales

Definition: Small deep back muscles located between the spinous processes. Function: Extend the spine or laterally flex the trunk/spine.

Intertransversarii

Definition: Small deep back muscles located between the transverse processes. Function: Extend the spine or laterally flex the trunk/spine.

Glenoid labrum

Definition: Cartilage rim around the glenoid fossa of the scapula; the SLAP tear affects it. Function: (general anatomy) Deepens the socket of the shoulder joint and helps keep the humerus in place.

Scapular fossae

Definition: Supraspinous fossa (above the scapular spine), infraspinous fossa (below the spine), subscapular fossa (front surface of the scapula). Function: Each is the home of a rotator cuff muscle: supraspinatus, infraspinatus, subscapularis.

Frontal belly of occipitofrontalis

Definition: Part of the occipitofrontalis muscle over the forehead. Function: (general anatomy) Raises the eyebrows and wrinkles the forehead.

Occipital belly of occipitofrontalis

Definition: Part of the occipitofrontalis muscle over the back of the skull. Function: (general anatomy) Pulls the scalp posteriorly.

Temporalis

Definition: Fan-shaped muscle on the side of the skull. Function: (general anatomy) Elevates the mandible (closes the jaw).

Masseter

Definition: Cheek muscle over the angle of the jaw. Function: (general anatomy) Elevates the mandible (closes the jaw).

Orbicularis oculi

Definition: Circular muscle around the eye. Function: (general anatomy) Closes the eyelids.

Orbicularis oris

Definition: Circular muscle around the mouth (the slide's example of a circular muscle). Function: (general anatomy) Closes and purses the lips.

Zygomaticus major

Definition: Facial muscle from the cheekbone to the corner of the mouth. Function: (general anatomy) Pulls the corner of the mouth up and back (smiling).

Buccinator

Definition: Cheek muscle. Function: (general anatomy) Compresses the cheek (e.g., holds food against the teeth).

Platysma

Definition: Thin superficial sheet of muscle over the front of the neck. Function: (general anatomy) Depresses the lower lip/jaw and tenses the skin of the neck.

Linea alba

Definition: Tendinous midline band of the abdomen running between the right and left rectus abdominis (rectus sheath). Function: (general anatomy) Anchors the abdominal muscles along the midline.

Anconeus

Definition: Small muscle on the posterior elbow. Function: (general anatomy) Assists the triceps brachii in extending the forearm.

Palmaris longus

Definition: Superficial anterior forearm muscle. Function: (general anatomy) Weakly flexes the wrist.

Flexor retinaculum and extensor retinaculum

Definition: Bands of connective tissue at the wrist (flexor) and ankle (superior and inferior extensor). Function: (general anatomy) Hold tendons in place against the joint.

Gluteus maximus

Definition: Largest buttock muscle (posterior hip). Function: (general anatomy) Extends and laterally rotates the thigh at the hip.

Gluteus medius

Definition: Muscle on the lateral side of the hip, deep to gluteus maximus. Function: (general anatomy) Abducts the thigh and stabilizes the pelvis.

Tensor fasciae latae

Definition: Muscle on the lateral hip that attaches to the iliotibial tract. Function: (general anatomy) Flexes and abducts the thigh and tenses the iliotibial tract.

Iliotibial tract

Definition: Thick band of fascia on the lateral thigh. Function: (general anatomy) Stabilizes the hip and knee.

Iliopsoas

Definition: Deep anterior hip muscle. Function: (general anatomy) Flexes the thigh at the hip.

Pectineus

Definition: Short muscle on the upper medial thigh. Function: (general anatomy) Flexes and adducts the thigh.

Adductor longus

Definition: Medial thigh muscle. Function: (general anatomy) Adducts the thigh.

Adductor magnus

Definition: Large medial thigh muscle. Function: (general anatomy) Adducts the thigh (and helps extend it).

Gracilis

Definition: Long, thin medial thigh muscle. Function: (general anatomy) Adducts the thigh and flexes the knee.

Sartorius

Definition: Long strap-like muscle crossing the anterior thigh from lateral to medial. Function: (general anatomy) Flexes the hip and knee and laterally rotates the thigh.

Quadriceps femoris

Definition: Group of four muscles in the anterior thigh: rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. Function: Extends the leg at the knee (antagonist of the hamstrings). The rectus femoris also flexes the hip (general anatomy).

Rectus femoris

Definition: Quadriceps muscle on the anterior thigh; bipennate (slide example). Function: Extends the leg at the knee (general anatomy: also flexes the hip).

Vastus lateralis and vastus medialis

Definition: Quadriceps muscles on the lateral and medial sides of the anterior thigh. Function: Extend the leg at the knee.

Hamstrings

Definition: Group of three muscles in the posterior thigh: biceps femoris, semitendinosus, semimembranosus. Function: Flex the leg at the knee (antagonist of the quadriceps); (general anatomy) also extend the thigh at the hip.

Gastrocnemius

Definition: Superficial calf muscle; the slide's example of a second-class lever. Function: (general anatomy) Plantar flexes the foot and flexes the knee.

Soleus

Definition: Calf muscle deep to the gastrocnemius. Function: (general anatomy) Plantar flexes the foot.

Plantaris

Definition: Small muscle in the posterior leg with a long thin tendon. Function: (general anatomy) Weakly assists plantar flexion.

Calcaneal tendon

Definition: Tendon attaching the gastrocnemius and soleus to the calcaneus (heel bone). Function: (general anatomy) Transmits calf muscle force to plantar flex the foot.

Tibialis anterior

Definition: Muscle on the anterior (front) leg beside the tibia. Function: (general anatomy) Dorsiflexes and inverts the foot.

Fibularis longus

Definition: Muscle on the lateral leg. Function: (general anatomy) Everts and plantar flexes the foot.

Extensor digitorum longus

Definition: Muscle on the anterior and lateral leg. Function: (general anatomy) Extends the toes and dorsiflexes the foot.