Chapter 11 notes - good resource for exam prep PDF

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Chpt. 11: Muscle of the Body 11.1 Mechanics of Muscle Function ● Arrangement of Fascicles in Muscles ○ Circular pattern- fascicles arranged in concentric rings ■ Surround external body openings, which they close by contracting ■ General name is the sphincter ● Orbicularis oris muscle around the mouth ● Orbicularis oculi around the eyes ○ Convergent pattern- fascicle arrangement where the origin is broad & the fascicles converge toward the tendon of insertion ■ Muscle fibers extend the length of the muscle from the length of the muscle from the origin to insertion ■ Triangle or fan-shaped ● Pectoralis major muscle ○ Parallel pattern- fascicles arrangement where the long axes of the fascicles run parallel to the long axis of the muscle & the muscle fibers extend from origin to insertion ■ Fusiform with an extended belly like the biceps brachii of the arm ■ Straplike like the sartorius muscle of the lower limb ○ Pennate pattern- the fascicles are short & attach obliquely to a tendon that runs the whole length of the muscle ■ Makes the muscle look like a feather ■ Multipennate→ arrangement looks like many feathers situated side by side with all their quills inserting into one large feather (deltoid) ■ Bipennate→ fascicles insert into the tendon from both sides (rectus femoris) ■ Unipennate→ fascicles insert into only one side of the tendon (extensor digitorum longus) ○ Arrangement of its fascicles influences both the amount of movement produced when a muscle shortens (range of motion) & amount of force the muscle produces (power) ■ More parallel→ more a muscle can shorten, resulting in longer distance of movement, not as powerful ■ More fibers→ more powerful

● Lever Systems: Bone-Muscle Relationships ○ Lever (bones of skeleton)- rigid bar that moves on a fixed point, the fulcrum (joints), when a force is applied to the lever ■ Allows a given effort to either: ● Move a heavier load ● Move a load farther & faster ■ Power lever- effort is farther from the fulcrum than load is, resulting in mechanical advantage, enabling a small effort to move a large load

■ Speed lever- effort is closer to fulcrum than the load, resulting in a mechanical disadvantage, but increase in speed, greater force required too move load

■ Law of Levers- when the effort arm is longer than the load arm, the lever operates at mechanical advantage, when the effort arm is shorter than the load arm, the lever operates at a mechanical disadvantage ○ Effort (muscle contraction)- the applied force is used to movie a resistance or load (body part that’s moved along with anything connected to it) ○ Example: See-saw ■ fulcrum→ middle ■ Two levers extend outward ■ Effort→ body weight of individuals ■ load→ weight of individuals ■ Distance from fulcrum where each is sitting is the effort arm & load arm respectively ○ Three classes of levers ■ First-Class Levers- fulcrum is located between the load & the point at which the effort is applied

● Can operate either at a mechanical advantage, for power, or at mechanical disadvantage, for speed & distance, depending on the lengths of the load arm & effort arm ● Example: posterior neck muscles around the atlanto-occipital joint to support the head ■ Second-Class Levers- effort is applied farther away from the fulcrum than the load ● Effort arm is longer than the load arm & the lever operates at mechanical advantage ● Example: standing on your toes ○ Fulcrum→ Metatarsophalangeal joint ○ Effort→ calf muscles plantar flex foot ○ Load→ elevating the body ■ Third-Class Levers- effort is applied closer to the fulcrum than the load ● Load arm is longer than the effort arm & operate at mechanical disadvantage ● Example: flexion of forearm (load) by the biceps brachii muscle (effort) at the elbow (fulcrum) ● Most skeletal muscles function as this for speed ○ Places insertions close to joint providing stability to the joint ○ Producing fast, extensive movements as in running or throwing with relatively little shortening of the muscle

● Muscle Actions and Interactions

○ Whatever action one muscle can do, there must be other muscles that can “undo” the action ○ Groups of muscles that produce opposite movements lie on opposite sides of a given joint

○ Muscles are classified into several functional types ■ Prime mover/Agonist- muscle that has the major responsibility for producing a specific movement of that motion ● Pectoralis major is agonist for flexing the arm but antagonist for extension of the arm ■ Antagonist- muscles that oppose or reverse a particular movement ● Latissimus dorsi is agonist for flexing the arm but prime mover for extension of the arm ■ Synergists- help prime movers, either by adding a little extra force to the movement being carried out or by reducing undesirable extra movements that the prime mover may produce ● Fixators→ hold a bone firmly in place so that a prime mover has a stable base on which to move a body part ○ Muscles that fix the scapula when the arm moves ○ Muscles that maintain posture & stabilize joints ● Act to cancel some of the movements when a prime mover cross several joints & cause movement at all of them 11.2 Organization of Skeletal Muscles ● Organizational Scheme Based on Embryonic Development ○ Muscle of visceral organs

■ Either smooth or cardiac muscle ■ Develops from the splanchnic mesoderm around the early gut ○ Pharyngeal arch (branchiomeric) muscles ■ Skeletal muscles of the pharynx plus some other muscles of the head & neck ■ All develop around the embryonic pharynx from the 4th to 7th somitomeres ● Muscles of facial expression ● Two sets of muscles involved in swallowing: ○ Suprahyoid muscles ○ Pharyngeal constrictors ● Sternocleidomastoid (neck) ● Trapezius (back) ○ Axial muscles ■ Skeletal muscles of the thorax, abdooment, & pelvis plus many muscles of the neck & few in the head ■ Lie anterior & posterior to the body axis ■ Main functions are moving the trunk & maintaining posture ■ Develop from the myotomes & some somitomeres ○ Limb muscles ■ Upper & lower limbs arise from the ventral region as limb buds, & limb muscles develop from the lateral parts of the nearby myotomes ■ Function in locomotion & manipulation objects

● Muscle Compartments of the Limbs ○ Upper Limb ■ Anterior

● Compartment of the arm: ○ Biceps brachii, brachialis, & coracobrachialis ○ Flex arm at the shoulder or flex forearm at the elbow ○ Innervated by the musculocutaneous nerve ● Compartment of the forearm: ○ Wrist, digital flexors, & pronators ○ Innervated by either the median nerve or ulnar nerve ■ Posterior ● Compartment of the arm: ○ Triceps brachii ○ Extend elbow ○ Innervated bt radial nerve ● Compartment of the forearm: ○ Digital & carpal extensors ○ Extend wrist ○ Innervated by radial nerve

○ Lower Limb ■ Posterior ● Thigh (hamstring group): ○ Extend the thigh at the hip & flex leg at the knee ○ Innervated by the tibial branch of sciatic nerve ● Leg: ○ Digital flexor muscles & plantar flexors ○ Innervated by the tibial nerve ■ Anterior

● Thigh (iliopsoas & quadriceps femoris): ○ Flex thigh at hip & extend leg at knee ○ Innervated by femoral nerve ● Leg: ○ Digital extensor muscles & dorsiflexors ○ Innervated by deep fibular nerve ■ Medial→ Thigh (adductor group): ● Adduct thigh ● Innervated primarily by the obturator nerve ■ Lateral→ Leg: ● Fibularis muscles that planter flex & evert foot ● Innervated by superficial fibular nerve

11.3 Major Skeletal Muscles of the Body

● Naming the Skeletal Muscles ○ Location ■ Brachialis→ in the arm (brachium = arm) ■ Intercostal muscle→ lie between ribs (costa =ribs) ○ Shape ■ Deltoid→ triangular (greek delta = Δ) ■ Right & Left Trapezius form a trapezoid ○ Relative Size ■ Maximus→ largest ■ Minimus→ smallest ■ Longus→ long ■ Brevis→ short ○ Direction of Fascicles and Fibers ○ Location of Attachments ■ Reveals their points of origin & insertion ■ Origin always named first→ brachioradialis ● Origin = brachium (humerus) ● Insertion = radius ○ Number of origins ■ Biceps→ “two heads” ■ Triceps→ “three heads” ■ Quadriceps→ “four heads” ○ Action ■ Flexor/Extensor ■ Adductor/Abductor ● The Muscle Tables ○ Muscles of the Head→ Facial Expression ■ Lie in the face & scalp just deep to the skin ■ Thin & vary in shape & adjacent muscles tend to be fused ■ Insert on skin NOT bones

○ Muscles of the Head→ Mastication (chewing) & Tongue Movement ■ Prime movers of jaw closure are the masseter & temporalis ■ Buccinator plays a role in chewing ■ Tongue muscles are composed of muscle fibers that curl, squeeze, & fold the tongue during speaking & chewing

○ Muscles of the Anterior Neck & Throat→ swallowing ■ Suprahyoid muscles aid in closing the air passageways of the larynx ■ Infrahyoid muscles pull hyoid bone & larynx inferiorly to their original position ■ Pharyngeal constrictor muscles of the walls of the throat squeeze the food inferiorly into the esophogus

○ Muscles of the Neck & Vertebral Column→ head movements & trunk expression ■ Head movements→ the head is moved by muscles that originate on the axial skeleton inferiorly ● Flexion→ sternocleidomastoid muscles ● Lateral flexion & rotation→ contraction fo muscles on one side of neck (sternocleidomastoids & deeper neck muscles) ● Extension→ aided by trapezius but mainly splenius muscles ■ Trunk extension is brought about by the deep (intrinsic) back muscles ■ Largest of the deep back muscles is the erector spinae group→ iliocostalis, longissimus, & spinalis

○ Deep Muscles of the Thorax→ breathing ■ Intercostal muscles are very short & run only from one rib to the next ● External form the most superficial layer (inspiration) ● Internal form intermediate muscle ● Third & deepest layer composed of the subcostalis, innermost intercostals, & transversus thoracis

■ Diaphragm- most important muscle of respiration, it forms a complete partition between the thoracic & abdominopelvic cavities ■ Accessory muscles of ventilation ● Scalene & sternocleidomastoid help lift ribs in forced inspiration ● Abdominal muscles help in forced expiration

○ Muscles of the abdominal wall→ trunk movements & compression of abdominal viscera ■ External oblique, internal oblique, & transversus abdominis ■ Anterior flexion, lateral flexion, & rotation of trunk

○ Muscles of the Pelvic Floor & Perineum→ support of abdominopelvic organs ■ Pelvic diaphragm consist of the levator ani & small coccygeus, supporting pelvic organs ■ Perineum- body region inferior to pelvic diaphragm

○ Superficial Muscles of the Anterior & Posterior Thorax→ movements of the scapula ■ Elevation→ superior movement with levator scapulae & superior fascicles of trapezius functioning as prime movers & rhomboids as synergists ■ Depression→ inferior movement with the serratus anterior, pectoralis minor, & inferior part of the trapezium working synergistically ■ Protraction/Abduction→ serratus anterior prime mover ■ Retraction/Adduction→ mid part of trapezius & rhomboids act as synergists ■ Upward Rotation→ serratus anterior & superior part of trapezius ■ Downward Rotation→ rhomboids & levator scapulae

○ Muscles Crossing the Shoulder Joint→ movements of the arm ■ Prime movers→ pectoralis major, latissimus dorsi, & deltoid ■ Synergists & fixators→ supraspinatus, infraspinatus, subscapularis, teres minor, teres major, & coracobrachialis

○ Muscles Crossing the Elbow Joint→ Flexion & Extension fo the Forearm

○ Muscles of the Forearm→ movements of the wrist, hand, & fingers

○ Intrinsic Muscles of the Hand→ fine movements of the fingers

○ Muscles Crossing the Hip & Knee Joints→ movements of the thigh & leg ■ Anterior muscles of hip & thigh primarily flex the thigh at the hip & extend the leg at the knee ■ Posterior muscles of hip & thigh extend the thigh & flex the leg ■ medial/adductor muscles have no action on the leg ■ Movements of the thigh: ● Flexors→ iliopsoas, tensor fasciae latae, rectus femoris, & pectineus ● Extensors→ gluteus maximus & hamstrings ● Adductors→ originate medial to hip joint ● Abductors→ gluteus medius & minimus ● Medial & later rotators→ adductors & deep muscles of glute ■ Movements of the leg: ● Extensors→ quadricep femoris ● Flexors→ hamstring muscles

○ Intrinsic Muscles of the Foot→ toe movement & foot support

11.4 Regional Surface Anatomy ● The Head

● The Neck

● The Thorax & Abdomen

● The Back

● The Upper Limb and Shoulder

● The Lower Limb and Gluteal Region...