Chapter 11 The Muscular System

An Introduction to the Muscular System The Muscular System consists only approximately 600 human skeletal muscles Muscle organization affects power, range, and speed of muscle movement Muscle cells (fibers) are organized in bundles called (fascicles) specific arrangement based on muscle function Skeletal muscles are classified by the way fascicles are organized – the relationships of fascicles to tendons 4 patterns of fascicle organization Parallel, Convergent, Pennate, Circular Each fascicle fibers are parallel and surrounded by perimysium The strength (power) of the muscle and the direction (range of motion) of its pull are determined partly by the orientation or shape of its fascicles Longer fibers: have greater range of motion & cover greater distance Short muscles with higher cross-sectional area have more force (tension)

Sarcolemma with transverse tubules (T-tubules) Muscle fiber Myofibril Myofilaments

Fascicle Arrangement Parallel Muscles Fibers parallel to the long axis of muscle Most skeletal muscles are this shape The tension developed during contractions depends on total # of myofibrils When parallel muscle contracts it shortens and get large in diameter. Some are broad flat bands, others are plump and cylindrical with tendons at both ends. Spindle shaped with a belly in the center For example, biceps brachii, rectus abdominus

Fascicle Arrangement - Convergent Muscles A broad area converges on attachment site (tendon, aponeurosis, or raphe-slender band of collagen fibers) Muscle fibers pull in DIFFERENT DIRECTIONS, depending on stimulation. This allows for wider versatility. When entire muscle contracts fibers do not pull as hard as the parallel type fan-shaped, broad at origin and tapering to a narrower insertion; more fibers For example, pectoralis muscles, temporalis

Fascicle Arrangement - Pennate Muscles Form an angle with the tendon Do not move as far as parallel muscles Contain more muscle fibers than parallel muscles producing more tension or force but smaller range of motion Unipennate Fibers on one side of tendon For example, extensor digitorum Bipennate Fibers on both sides of tendon For example, rectus femoris Multipennate Tendon branches within muscle For example, Deltoid

Fascicle Arrangement - Circular Muscles Also called sphincters Open and close to guard entrances of body Form ring around body opening orbicularis oris orbicularis oculi, urethral and anal sphincters

Skeletal Motion and Levers Skeletal muscles attach to skeleton, produce motion Attaching a muscle to a lever can modify the direction, force, speed and distance of the movement produced by the muscle contraction. A lever moves when pressure (applied force) is sufficient to overcome resistance (load). Levers: Mechanically bones operates as levers (rigid, moving structure) Move around a fixed point called the FULCRUM (F) which is a JOINT MUSCLES provide APPLIED FORCE / EFFORT (AF) on lever Required to overcome LOAD (L) = the RESISTANCE that opposes the movement The three classes of levers Depend on the relationship between applied force, fulcrum, and resistance First-class lever Bones = levers Second-class lever Muscles = effort/Force Third-class lever Fulcrum= joint Moves the Load

First- Class Levers Example 3: Scissors Example 4: Car Jack Center fulcrum between applied force and load Force and load are balanced Example 1: head on the vertebral column Load: weight of face, car Fulcrum: joint between skull and atlas, jack Applied force (Effort) : posterior neck muscles Example 2: Seesaw or teeter-totter Example 3: Scissors Example 4: Car Jack

Second-Class Levers Center resistance between applied force and fulcrum If the applied force is further from the fulcrum than the load, a strong resistance can be moved A small force moves a large weight Sacrifices speed Example 1:using the calf muscles to rise up on the toes Example 2: Wheelbarrow is an example Load is body weight Fulcrum is ball of Foot (metatarsal phalangeal joint) Applied force (effort) is contraction of the calf muscles

Second-Class Levers

Third-Class Levers MOST COMMON levers in the body Center applied force between load and fulcrum Greater force moves smaller load Maximizes speed and distance traveled Example 1: muscles like the biceps brachii that flex the forearm Load is the weight of the forearm and hand (plus whatever is held in the hand) Fulcrum is elbow Applied force (effort): contraction of biceps brachii muscle Example 2: tweezers

Third-Class Levers

http://dreambodysixpack.com/wp-content/uploads/2014/03/levers.jpg

https://lifescitpjhs. wikispaces. com/file/view/Levers https://lifescitpjhs.wikispaces.com/file/view/Levers.gif/330073754/520x416/Levers.gif

Muscle Attachments to Other Tissues Origin ORIGIN – bony attachment at STATIONARY end of muscle-does not move one fixed point of attachment INSERTION- bony attachment to MOVABLE END of muscle And one moving point of attachment Most muscles originate or insert on the skeleton Skeletal muscles shorten & pull on the two skeletal elements to which they are attached. Origin is usually proximal to insertion Insertion

Tendons and Aponeuroses Collagen fibers of the endomysium, perimysium, and epimysium join at ends of muscles to form CT attachment to periosteum of bone. When muscles contract they pull on the tendon that then moves the bone “Cable-like” cord of dense CT collagen fibers and elastic fibers (Ex: back of your hand). Direct very little separation between bone and muscle (brachialis) Indirect larger separation (biceps brachii) Biceps brachii Brachialis Aponeurosis: broad flat tendon. Sparingly supplied with blood vessels and nerves. Formation of rectus sheath from aponeuroses of the abdominal muscles.

Muscle Interactions Muscles work in groups to maximize efficiency action – the effects to produce or prevent movement Agonist (Prime Mover) muscle that produces most of force during a joint action produces a particular movement Synergist A smaller muscle that assists a larger agonist Helps start motion or stabilize origin of agonist (fixator) stabilizes the nearby joint modifies the direction of movement Antagonist Opposes movement of a particular agonist relaxes to give prime mover control over an action prevents excessive movement and injury antagonistic pairs – muscles that act on opposite sides of a joint; flexors–extensors, abductors–adductors

Muscle Actions Across Elbow prime mover Brachialis synergist biceps brachii fixator - muscle that holds scapula firmly in place Rhomboids antagonist triceps brachii

Naming Skeletal Muscles LOCATION in the Body Identifies body regions For example, temporalis, frontalis, tibialis anterior, ORIGIN AND INSERTION First part of name indicates origin Second part of name indicates insertion Ex: Sternocleidomastoid FASCICLE ORGANIZATION (Direction) Describes fascicle orientation within muscle rectus (straight), transversus, oblique Ex: rectus abdominus POSITION Extrinsic -Muscles outside an organ (Hypoglossus-tongue from the mandible) Intrinsic- Muscles inside an organ (inferior longitudinal muscle lines the sides of the tongue)

Naming Skeletal Muscles STRUCTURAL CHARACTERISTICS Number of tendons origins Biceps (biceps femoris) Triceps (triceps brachii) Quadriceps (quadraceps femoris) Shape Trapezius, deltoid, rhomboid, orbicularis Size maximus, minimus, longus, brevis ACTION Flexor and Extensor (extensor digitorum) Abductor and Adductors (adductor magnus) Levator and Depressor (levator scapulae) Supinator and Pronator (pronator teres)

Naming Exercises Extensor carpi radialis longus Biceps brachii Adductor longus Occipitalis Orbicularis oris Quadriceps femoris Gluteus maximus Rectus abdominus

Naming Skeletal Muscles Terms Indicating Specific Regions of the Body Abdominis (abdomen) Brachialis (brachium) Carpi (wrist) Cleido-/-clavius Cutaneous (skin) Femoris (femur) Radialis (radius) Scapularis (scapula) Temporalis (temples) Thoracis (thoracic region) Tibialis (tibia) Sartorius (like a tailor) Buccinator (trumpeter) Costalis (ribs) Glosso-/-glossal (tongue) Inguinal (groin) Oculo- (eye) Oris (mouth) Popliteus (posterior knee) Uro- (urinary) Gracilis (slender) Latissimus (widest Vastus (great) Major (larger) Minor (smaller)

Extrinsic Muscles of the Eyeball Originate on skull, insert onto white (sclera) of eye Four muscles are rectus (straight) and two are oblique Fastest contracting and most precisely controlled muscles Superior rectus, inferior rectus, medial rectus, lateral rectus Superior oblique, inferior oblique

Muscles of Facial Expression Originate on skull or within the skin and insert into the skin Express emotions, assist in chewing, whistling, blowing, sucking Examples: Occipitalis, frontalis, zygomaticus major/minor, buccinator, orbicularis oris (orb= circle; oris=mouth), orbicularis oculi (oculi=eye)

Dimples are a deformity of the zygomaticus MAJOR muscle Dimples are a deformity of the zygomaticus MAJOR muscle. Generally thought to be a birth defect where this muscle is shorter than normal.

Muscles of Mastication Originate from skull and insert on the mandible Masseter The strongest jaw muscle; elevates the mandible Temporalis Helps elevate and retract the mandible Pterygoid muscles Medial/lateral Position mandible for chewing; elevation and depression of mandible; helps to protrude the jaw

Muscles of the neck that move the head Sternocleidomastoid: originates from sternum and clavicle and inserts on mastoid process If both left and right are contracted, the cervical vertebrae flex and head extends Contraction of one flexes the neck laterally and rotates the face in the opposite direction Scalene muscles Cervical oblique muscles that flex the neck

Scalene muscles

Muscles of the Abdominal Wall Oblique and Rectus Muscles Function in abdominal compression needed for forced breathing (exercise), urination, defecation, childbirth, for bending the trunk Lie within the body wall Oblique muscles- external and internal obliques and transversus abdominis Compress underlying structures Rotate vertebral column Rectus muscles- vertically oriented (six-pack) Flex vertebral column Between xiphoid process and pubic symphysis Divided longitudinally by linea alba (medial collagenous partition) Diaphragmatic muscle

Muscles of the Abdominal Wall Linea alba External oblique Rectus abdominis Stabilized vertebral column Aids in compression of abdominal wall Trunk rotation Rotates lumbar vertebrae Stabilized pelvis for walking Internal oblique Transverse abdominis Same function as External oblique Compresses abdominal contents

Muscles of Respiration - diaphragm relaxation contraction flattens diaphragm enlarges thoracic cavity (inspiration) in relaxation of diaphragm it rises shrinks the thoracic cavity (expiration) contraction https://media1.britannica.com/eb-media/36/92936-004-8881E781.jpg

Muscles Used in Breathing external intercostals elevates ribs expand thoracic cavity create partial vacuum causing inflow of air- Inspiration internal intercostals depresses and retracts ribs compresses thoracic cavity expelling air- Expiration

Muscles of the Shoulders and Upper Limbs Muscles that position the pectoral girdle trapzius, rhomboid, levator scapulae, serratus anterior, pectoralis minor Muscles that move the arm deltoid, teres major and minor, pectoralis major, latissimus dorsi, Muscles involved in shoulder rotation the Rotator Cuff Muscles that move the forearm and hand Extensors- Mainly on posterior and lateral surfaces of arm Flexors- Mainly on anterior and medial surface Muscles that move the hand and fingers

Muscles That Position the Pectoral Girdle trapezius stabilizes scapula/ shoulder elevates/depresses shoulder apex levator scapulae elevates scapula flexes neck laterally rhomboideus major/minor retracts scapula and braces shoulder trapzius, rhomboid, levator scapulae, serratus anterior, pectoralis minor

Muscles That Position the Pectoral Girdle Pectoralis Minor ribs to coracoid process of scapula protracts and depresses scapula lifts ribs during forced expiration Serratus anterior On the chest Originates along ribs They help us move our arms multi- dimensionally and with great speed.

Axial Muscles that Move the Arm Pectoralis major makes up the bulk of the chest muscles in the male and lies under the breast in the female. has four actions which are primarily responsible for movement of the shoulder joint in flexion. Deltoid The major abductor originates from the acromion and spine of the scapula inserts on humerus Abducts, flexes and extends arm

Axial Muscles that Move the Arm - Posterior Teres Major/Minor Produce medial rotation at shoulder Latissimus dorsi Produces extension at shoulder joint

The Rotator Cuff Muscles involved in shoulder rotation Supraspinatus Subscapularis Anterior Infraspinatus Posterior Teres minor their tendons http://medicalimages.allrefer.com/large/rotator-cuff-muscles.jpg

Muscles that Move the FOREARM: FLEXORS Humerus Biceps brachii, short head Biceps brachii, long head Biceps brachii: originates on scapula; inserts on radial tuberosity. Flexes shoulder and elbow; supinates hand Triceps brachii, long head Triceps brachii, medial head Brachialis Brachialis: originates on humerus; inserts on ulna. Flexion of elbow Brachioradialis Brachioradialis: originates on humerus; inserts on radius. Flexes elbow Anterior view, superficial layer 43

Muscles Acting on Elbow Principal flexors biceps brachii inserts on radius brachialis inserts on ulna Synergistic flexor brachioradialis Prime extensor triceps brachii inserts onto ulna 3 origins on the humerus

Supination/ Pronation Forearm Pronator teres -pronates the forearm, turning the hand posteriorly. Articulates with the humerus and ulna Supinator- supinates the forearm, turning the hand anteriorly. Articulates with the humerus and the radial tuberosity. Lies beneath brachialradialis

The extensor digitorum muscle of the posterior forearm extends the medial four digits of the hand.

Tendon Sheaths Flexor retinaculum bracelet-like fibrous sheet flexes the wrist Anterior surface of wrist Stabilizes tendons of flexor muscles Extensor retinaculum Wide band of connective tissue Posterior surface of wrist Stabilizes tendons of extensor muscles Tight space between the flexor retinaculum and the carpal flexor tendons is called the carpal tunnel. Inflammation of the retinaculum and synovial tendon sheaths can restrict movement and irritate the distal portions of the median nerve that innervates the hand. This condition is known as carpal tunnel syndrome.

Appendicular Musculature Compartments –spaces in which muscles are organized and separated by fibrous connective tissue sheets called facia. Three compartments each with unique innervation: Anterior compartment: quadriceps femoris; sartorius Medial compartment: adductors; obturator nerve Posterior compartment: hamstrings (biceps femoris, semimembranosus, semitendinosus); sciatic nerve Muscles That Move the Thigh Gluteal muscles Adductors

Gluteal Muscles Deeper muscles of the hip - rotate femur Gluteus maximus Largest, most posterior gluteal muscle Produces extension and lateral rotation at hip; extends hip Gluteus medius and gluteus minimus Originate anterior to gluteus maximus Insert on trochanter; abduct hip

Medial Adductors / Lateral Rotators Adductor Group Adductor magnus Produces adduction, extension, and flexion Adductor brevis Hip flexion and adduction Adductor longus Pectineus Gracilis Lateral group Piriformis Hip extension and flexion. Attaches to sacrum and femur Piriformis syndrome occurs when the piriformis irritates the sciatic nerve which comes into the gluteal region beneath the muscle, causing pain in the buttocks and referred pain along the sciatic nerve.

Posterior Muscles of the Thigh Extend hip and flex knee Hamstrings Biceps femoris Semimembranosus Semitendinosus

Anterior Muscles that Cross the Hip Joint Extensors of the Knee Four muscles of the quadriceps femoris 3 heads originate from femur; all heads insert on quadriceps tendon above patella vastus lateralis, vastus medialis, vastus intermedius Rectus femoris muscle Sartorius Originates superior to the acetabulum longest muscle in the body- obliquely from thigh to knee- tailors muscle –helps effect cross-legged position

Muscles of the Calf: Posterior/Anterior Muscles That Produce Extension (Plantar Flexion) at the Ankle Gastrocnemius -flexes knee and ankle Soleus - flex ankle The Achilles Tendon - calcaneal tendon Shared by the gastrocnemius and soleus Muscles That Produce Flexion (Dorsiflexion) at the Ankle Tibialis anterior Opposes the gastrocnemius

Muscles that move the tarsals, metatarsals, and phalanges and originate and insert only on those bones

gluteus medius – never the maximus; risk of damaging the sciatic nerve Injections Subcutaneous Intramuscular: Most common sites: deltoid gluteus medius – never the maximus; risk of damaging the sciatic nerve vastus lateralis Intravenous