Muscular System PDF

Three muscle types Similarities:  skeletal & smooth -- elongated Ability of muscle to shorten -- depend on two type of myofilaments, the muscle microfilament of cytoskeleton Myo & Mys -- muscle & sarco (flesh) but all mean muscle Muscles are delicate Skeletal  \- Form the contours of body...

Three muscle types Similarities:  skeletal & smooth -- elongated Ability of muscle to shorten -- depend on two type of myofilaments, the muscle microfilament of cytoskeleton Myo & Mys -- muscle & sarco (flesh) but all mean muscle Muscles are delicate Skeletal  \- Form the contours of body smoothly, huge cigar shape and multi-nucleited cells \- Largest muscle fiber 30cm in length (striated)  \- Often activated by reflexes (voluntary) \- Fibers soft and fragile, bundled together to not rip apart when exerting force and effort Smooth \- Involuntary, no striations (ex. Stomach) \- Nasa walls of hollow visceral organs \- Spindle shape, single nucleus Cardiac  \- In heart \- Pump and propelled blood into diff tissues of the body (striated but involuntary) \- Innervated by the nervous system  \- Cushioned by small amount of endomysium \- Spiral figure of 8 (allowed the coordinated movement of heart) \- The internal chambers become small, cause the propelled to go to other vessels \- Branching cells, joined by special junction called intercalated disc \- Have pacemaker  Skeletal  \- Enclosed in connective tissue (endomysium) that is covered by another tissue (perimysium)  \- The entire muscle is covered by epimysium and blend with the tendons (provide durability and conserve space) \- They move from slow to fast Smooth \- Arrange in layers, one circular and one longitudinal \- Alternately contract and relax, they change the size and shape of organ para sa movement ng food (alle uod) (peristalsis) \- Very slow in some Cardiac  \- Branching (involuntary) \- May pacemaker  \- Slow Muscle function  M-line -- tiny protein rod that hold adjacent thick filaments together Myofibrils -- chain of tiny contractile unit called sarcomere (aligned end to end like box scars) in a train along the length of myofibril \- Arrangement of even smaller structures myofilament within the sarcomeres that produces bonding pattern 2 types of thread like protein myofilaments within each of box scars sarcomeres Larger thick filaments (myosins) with ATPase enzymes for muscle contraction (nagbebreak mg ATP na nagsspan sa buong Dark A band) their mid parts are smooth but ends are studded with small projections (myosin heads -- cross bridges, link thick and thin fila together during contraction)  Thin filaments -- composed of contractile proteins, allowing myosin head binding to actin.  \- Anchored sa Z disc, the light I band has part of two adjacent sarcomere and contain only thin filaments \- The light I band has part of 2 adjacent sarcomeres and contain only thin filaments (although they overlap with thick filaments, they do not reach the middle of a relaxed sarcomeres \- central region are also know ln as bare zone -Calcium natin ang responsible na mag signal para magkaroon tayo ng contraction  https://lh7-rt.googleusercontent.com/docsz/AD\_4nXfBCU7EQtk3vUZYmc5Dep2pNGh0xuvfUaQGSJKsQTRz6TbspL55cXaRdQqs18Nd3E3JXi9cAd5VfuMve61LbhdTnAVGeXfbuX3orl8rmnRFgFRcnyxw4ph0JFfTdoHq0cpaKaU2\_c5Ym39q0QnAtO5ZJD-3?key=uWNXddzjksrnbVJ46-ADbg  MGA KAILANGAN NATIN PARA MAKAPRODUCE NG MOVEMENT: https://lh7-rt.googleusercontent.com/docsz/AD\_4nXcbfO5ufpNoSq8E6Ol7yxs5qPjJcNfvMOMW08-AX4n\_zoMhvl7bPf2r2\_0z7Vh-FjRT90FvSbmVEVcKPKrFnalynio1zKo7J6isOu8b8F739IS3SMwbY5IirqZ87o18mAJ2fpKOIunIKDvf2pgtUwoaOQqP?key=uWNXddzjksrnbVJ46-ADbg Para mangyari yung muscle control, meron muna tayong tunatawag na SILIDING FILAMENT THEORY - Sliding Filament Theory  - The activation of myosin\'s cross bridges - which is the force generating sites \- Shortening happens if and when the cross bridges generate enough tension on the thin filaments to exceed the forces that oppose shortening \- Contraction ends when the cross bridges become inactive, the tension declines, and then the muscle fiber relaxes During contraction the thin filaments slide past the thick ones so that the actin and myosin filaments overlap to a greater degree: \- When the nervous system stimulates muscle fibers, the myosin heads on the thick filaments latch onto myosin-binding sites on actin in the thin filaments, and the sliding begins. \- These cross bridge attachments form and break several times during a contraction, acting like tiny ratchets to generate tension and propel the thin filaments toward the center of the sarcomere. \-  As this event occurs simultaneously in sarcomeres throughout the cell, the muscle cell shortens. \- Notice that as the thin filaments slide centrally, the Z discs to which they attach are pulled toward the M line. Overall, as a muscle cell shortens: the l bands shorten the distance between successive Z discs shortens the H zones disappear, and the contiguous A bands move closer together but their length does not change - the fiber must be activated para nga magkaroon tayo ng contraction,  that is, stimulated by a nerve ending so that a change in - Next, it must generate an electrical current, called an **action potential,** sa ating **sarcolemma**. - The action potential is automatically propagated along the sarcolemma. - Then, intracellular calcium ion levels must rise **[briefly]**, providing the final trigger for \> Para magkaroon ng contraction, we have the phase 1 amd phase 2:   **[TROPONIN]** - bonding site ng ating calcium sa ating skeletal muscles  \> Imbes na troponin ang bonding site ng ating calcium ion(counter part ng smooth muscle, ang tawag dito is **[CALMODULIN]** https://lh7-rt.googleusercontent.com/docsz/AD\_4nXf3Ii9rfJNuSa2zg4qFp77YvHUko2IEFVUbaWNqsyWKDFhMjFYk\_SlgpaYrYaScosaAcQM7gDellQt5QhTv7MK9rVuHK2aKsMGH8csW4RsG6vEcezWt79agIHnkdisndDvv9UJDUJ4FL-LU5cEoOW2zjyvj?key=uWNXddzjksrnbVJ46-ADbg  DITO NA NADEDETECT YUNG CHANGES: https://lh7-rt.googleusercontent.com/docsz/AD\_4nXd3EPUGoa7B0zYjJxCeQ3YumPkViBlvt9w4aiNK12160m2ceWwYc8sl8DgP\_Qx3sugQmWo0VCWJRVKrQ0G5C3Mn6TMfuxpPdt1AL-AeD2fGhlRHXBPd33bcVPafENGwzgwJ5eRVGZ0KCKS8UtwPD9Bi1Qsb?key=uWNXddzjksrnbVJ46-ADbg \> **[-95mV]** - resting membrane (habang wala pang action) \> kapag nag open or may stimulus, meron ng pumasok na sodium ions sa ating muscle fibers, **tataas yung ating sodium concentrations (yan yung maglelead ng depolarization, pero kailangan niya muna mareach ung ating threshold)** \> kapag nareach na ung **[+30mV]**, magcclose na ang ating sodium channel, at kapag nagclose na ang sodium channel,  magoopen naman ang potassium ion(lalabas yan ng mabilisan para maabot natin ang repolarization) -**[Repolarization]** is due to Potassi Exit hanggang sa bumalik na sa ating resting membrane potential (-95mV) at kapag narating na ang resting membrane meron nang closure of potassium channels EXCITATION-CONTRACTION COUPLING  - sequence of events by which transmission of an action potential along the sarcolemma leads to the sliding of myofilaments. Setting the stage - the events at the neuromuscular junction (NMJ) set thr stage for E-C coupling by providing excitation. Release Of acetylcholine binds to receptor proteins on the sarcolemma and triggers an action potential in a muscle fiber. Steps in Excitation-Contraction Coupling 1. The action potential propagates along the sarcolemma and down the T tubules 2. Calcium ions are released. Transmission of the AP along the T tubules of the triads causes the voltage-sensitive tubule proteins to change shape. This shape change opens the Ca²+(calcium ions) release channels in the terminal cisterns of the sarcoplasmic reticulum (SR), allowing Ca²+ to flow into the cytosol. 3. Calcium binds to troponin(binding site ng calcium) and removes the blocking action of tropomyosin(blocking active site). When Ca²+ binds, troponin changes shape, exposing binding sites for myosin (active sites) on the thin filaments. 4. Contraction begins. Myosin binding to actin forms cross bridges and contraction (cross bridge cycling) begins. At this point, E-C coupling is over( kapag ubos na yung available na calcium at ATP sa area). CROSS BRIDGE CYCLE - series of events during which myosin heads pull thin filaments toward the center of the sarcomere. Step in cross bridge cycle 1. Cross Bridge Formation. Yung ATP mabebreak into ADP and Phosphate. To Energized myosin head attaches to an actin myofilament, forming a cross bridge.  2. The power (working) stroke. ADP and Phosphate are released and the myosin head pivots and bends, changing to its bent low-energy state. As a result it pulls the actin filament toward the M Line. (In the absence of ATP, myosin heads will not detach, causing rigor mortis(stiffening).)  3. Cross Bridge Detachment. After ATP attaches to myosin, the link between the myosin and actin weakens, and the myosin head detaches (the cross bridge breaks)\*pag nagdetach may next step\* 4. Cocking of the myosin head. As ATP is hydrolyzed to ADP and Phosphate, the myosin head returns to its prestroke high-energy or "cocked" position. Note: This cycle will continue as long as ATP is available and Ca²+ is bound to troponin. \*Cycle to contract\* TWO MAIN CATEGORIES OF CONTRACTION Isotonic contraction (concentric) - iso (same) ton (tension) - muscle length changes and moves a load. one sufficient tension has dev. to move the load, the tension remains constant thru the rest of the contractile period. - We have two sub categories: concentric - muscle shortens and does work such as picking a book and kicking a ball. eccentric  - generates force as lengthens, they are equally important for coordination and purposeful movement.  Isometric contraction - measure - there is no changes  - there is muscle tension but neither shorten nor lengthen - mga nakabitin Pathways for regenerating ATP during muscle act - Direct phosphorylation - creatine phosphate and adenosine diphosphate. gamit ang creatine kinase to break creatine and magproproduce na ng creatine and ATP.  - - - - Anaerobic Pathway - glycolysis in cytosol into pyruvic acid and then lactic acid formation - - - - Aerobic Pathway - air cellular respi, happen in mitochondria - - - Note: Thru all this pathway we produce 35 ATP Action Potential Binding of Ca Different Muscles  SUPERFICIAL MUSCLES OF THE BODY  https://lh7-rt.googleusercontent.com/docsz/AD\_4nXcLO7aBkXnSo2RuvArKZtEbAKj6qsk4\_hbvuR5QI7GvFDO9arnm9SR0QTXq7vOQn-mTRH3SnbnHKXv7VQSXwu8GZHSdObhQX9Y6ixvXl32IBrY96coQw\_1sbrrizOASbKql8HOcWsE6B1bBiQUWGvIbnpx9?key=uWNXddzjksrnbVJ46-ADbg Temporalis- sa temporal bone O. Oculi- sa mata O. Oris- sa mouth Trapezius-may mga prominent na muscles   YOU READ THE **ORIGIN** AND THE **NERVE SUPPLY!!** Muscles of the Head, Part I: Facial Expression MUSCLES OF THE SCALP - **Epicranius** (occipitofrontalis) (epi over; cran = skull) - Bipartite muscle consisting of the frontal and occipital bellies connected by the epicranial aponeurosis. The alternate actions of these two muscles pull scalp forward and backward - **Frontal** **belly** (front forehead) - With aponeurosis fixed, raises the eyebrows (as in surprise). Wrinkles forehead skin horizontally - **Occipital** **belly** (occipito base of skull) - Fixes aponeurosis and pulls scalp posteriorly - **Orbicularis** **oculi** (orb circular, ocul = eye) - Closes eye; various parts can be activated individually; produces blinking and squinting; draws eyebrows inferiorly - **Zygomaticus**-major and minor (zygomatic cheekbone) - Raises lateral corners of mouth upward (smiling muscle) - **Risorius** (risor laughter) - Draws corner of lip laterally; tenses lips; synergist of zygomaticus - **Levator** **labii** **superioris** (leva raise; labi = lip; superior above, over) - Opens lips; raises and furrows upper lip - **Depressor** **labii** **inferioris** (depressor depresses; infer = below) - Draws lower lip inferiorly (as in a pout) - **Depressor** **anguli** **oris** (angul angle, corner; or = mouth) - Draws corners of mouth down and laterally (a \"tragedy mask\" grimace); zygomaticus antagonist - **Orbicularis** **oris** - Closes lips; purses and protrudes lips; kissing and whistling muscle - **Mentalis** (ment = chin) - Wrinkles chin; protrudes lower lip - **Buccinator** (bucc cheek or \"trumpeter\") - Compresses cheek (as in whistling and sucking); trampoline-like action holds food between teeth during chewing; draws corner of mouth laterally; well developed in nursing infants - **Platysma** (platy broad, flat) - Tenses skin of neck (as during shaving); helps depress mandible; pulls lower lip back and down, producing downward sag of mouth https://lh7-rt.googleusercontent.com/docsz/AD\_4nXeP3Nye2IUE1UfRGFuPIsQ7HmlwtLF3Pj87bajO9w-zB3jJPO\_9wvwyETbXYTTqBk8uouaAGFPj9key2h6oPXNaVtdT9a7YhMyPqYlHjM7y89g0hxhlSIAe3mNJB91SMx4Cl7P-fF\_Gyqmbjblviv29IuAM?key=uWNXddzjksrnbVJ46-ADbg  Muscles of the Head, Part II: Mastication and Tongue Movement MUSCLES OF MASTICATION - **Masseter** (maseter chewer) - Prime mover of jaw closure; elevates mandible - **Temporalis** (tempora time; pertaining to the temporal bone) - Closes jaw; elevates and retracts mandible; maintains position of the mandible at rest; deep anterior part may help protract mandible - **Medial** **pterygoid** (medial toward median plane; pterygoid winglike) - Acts with the lateral pterygoid muscle to protrude (pull anteriorly) the mandible and promote side-to-side (grinding) movements; synergist of temporalis and masseter muscles in elevation of the mandible - **Lateral** **pterygoid** (lateral away from median plane) - Provides forward sliding and side-to-side grinding movements of the lower teeth; protrudes mandible - **Buccinator** - Compresses the cheek; keeps food between grinding surfaces of teeth during chewing MUSCLES PROMOTING TONGUE MOVEMENTS (EXTRINSIC TONGUE MUSCLES) - **Genioglossus** (geni = chin; glossus tongue) - Protracts tongue; can depress or act in concert with other extrinsic muscles to retract tongue - **Hyoglossus** (hyo pertaining to hyoid bone) - Depresses tongue and draws its sides inferiorly - **Styloglossus** (stylo pertaining to styloid process) - Retracts and elevates tongue  https://lh7-rt.googleusercontent.com/docsz/AD\_4nXeKn-gM3EDNiXIpzC\_5jqBnrUJg8f8tMn7iqxuZdPvYRULdS2g9ubWEZZS96oxgbZO8UAlH2Kb9z9Tzwb2AhgjWHG1EHRQa0vCueXpf5dKrMmoikMC1VYGBlQ2ZFuguzfgyAXIFzimCh1KdXDikza\_wSVvD?key=uWNXddzjksrnbVJ46-ADbg Muscles of the Anterior Neck and Throat: Swallowing SUPRAHYOID MUSCLES - Muscles that help form floor of oral cavity, anchor tongue, elevate hyoid, and move larynx superiorly during swallowing; lie superior to hyoid bone - **Digastric** (di two; gaster = belly) - Open mouth and depress mandible; acting in concert, the digastric muscles elevate hyoid bone and steady it during swallowing and speech - **Stylohyoid** - Elevates and retracts. hyoid, thereby elongating floor of mouth during swallowing - **Mylohyoid** (myle = molar) - Elevates hyoid bone and floor of mouth, enabling tongue to exert backward and upward pressure that forces food into pharynx - **Geniohyoid** (geni = chin) - Pulls hyoid bone superiorly and anteriorly, shortening floor of mouth and widening pharynx to receive food INFRAHYOID MUSCLES - Straplike muscles that depress the hyoid bone and larynx during swallowing and speaking - **Sternohyoid** (sterno sternum) - Depresses larynx and hyoid bone if mandible is fixed; may also flex skull - **Sternothyroid** (thyrothyroid cartilage) - Pulls larynx and hyoid bone inferiorly - **Omohyoid** (omo shoulder) - Depresses and retracts hyoid bone - **Thyrohyoid** - Depresses hyoid bone or elevates larynx if hyoid is fixed PICTURE PHARYNGEAL CONSTRICTOR MUSCLES - **Superior, middle, and inferior pharyngeal constrictor muscles** - The 3 pharyngeal constrictor muscles - they constrict the pharynx during swallowing w/c propels food to the esophagus via a massage-like action called **peristalsis.** Muscles of the Neck and Vertebral Column: Head Movements and Trunk Extension ANTEROLATERAL NECK MUSCLES - **Sternocleidomastoid** (sterno breastbone; cleido clavicle; mastoid= mastoid process) - they flex and laterally rotates the head simultaneously contraction of both muscles flexes the neck and generally against resistance as when raising head, when lying on back, acting alone each muscle rotates head towards shoulder on opposite sides and tilts or laterally fixes head to its own site. - **Scalenes** (anterior, middle, and posterior) (scalene uneven )- uneven muscles, elevate the first two ribs w/c aid in respiration, they flex and rotate the neck INTRINSIC MUSCLES OF THE BACK  - **Splenius** (capitis and cervicis portions) (splenion bandage; caput head; cervi = neck) - they extend or hyperextend the head when splenius muscle on one side activated, head rotates and bends laterally towards same site PICTURE - **Erector** **Spinae** - also called as **sacrospinalis** muscle; prime mover of back extension. Each side consists of 3 columns - the iliocostalis, longissimus, and spinalis.  - **Iliocostalis** (lumborum, thoracis, and cervicis portions) (ilio = ilium; cost rib; thorac = thorax) - extend and laterally flex the vertebral column; maintain erect posture; acting on one side, bend vertebral column to same side - **Longissimus** (thoracis, cervicis, and capitis parts) (Jongissimus longest) - extend and laterally flex vertebral column; capitis extends head and turns the face toward the same side - **Spinalis (**thoracis and cervicis parts) (spin vertebral column, spine) - they extends vertebral column - **Semispinalis** (thoracis, cervicis, and capitis regions) (semi half) - extends vertebral column and head and rotates them to opposite side; acts synergistically w/ stemocleidomastoid (scm) muscles of opp side - **Quadratus** **Lumborum** (quad four-sided; lumb = lumbar region) - flexes vertebral column laterally when acting separately; when pair acts jointly, lumbar spine is extended and 12th rib is fixed; maintains upright posture; assists in forced inspiration PICTURE Deep Muscles of Thorax: Breathing - **External** **intercostals** (external toward the outside; inter between; cost = rib) - w/ 1st ribs fixed w/ scalene muscles, pull ribs toward one another to elevate rib cage; aid in inspiration; synergist of diaphragm - **Internal** **Intercostals** (internal toward the inside, deep) - w/ 12th ribs fixed by quadratus lumborum, muscles of posteriior abdominal wall, they draw ribs together and depress rib cage; aid forced expiration; antagonistic to external intercostals - **Diaphragm** (dia across; phragm partition) - prime mover of inspiration; flattens on contraction, increasing vertical dimensions of thorax; when strongly contracted, dramatically increases intra-abdominal pressure PICTURE Muscles of the Abdominal Wall: Trunk Movements and Compression of Abdominal Viscera MUSCLES OF ANTERIOR AND LATERAL ABDOMINAL WALL - **Rectus** **abdominis** (rectus straight; abdom abdomen) - flex and rotate lumbar region of vertebral column; fix and depresses the ribs, stabilize pelvis during walking, increase intra-abdominal pressure; used in sit-ups, curls - **External** **Oblique** (external toward outside; oblique running at an angle) - flex vertebral column and compress abdominal wall and increase intra-abdominal pressure; acting individually, aid muscles of back in rotation trunk and flexing laterally; used in oblique curls - **Internal** **Oblique** (internal toward the inside; deep) - moving same as external oblique - **Transversus** **Abdominis** (transverse running straight across) - compresses abdominal contents PICTURE Muscles of the Pelvic Floor and Perineum: Support of Abdominopelvic Organs MUSCLE OF THE PELVIC DIAGRAM  - Levator ani (levator raises; ani anus) - supports and maintains position of pelvic viscera; resist downward thrusts that accompany rises in intrapelvic pressure during coughing, vomiting, and expulsive efforts of abdominal muscles; forms sphincters at anorectal junction and vagina; lifts anal canal during defecation - Coccygeus (соссу соссух) - supports pelvic viscera; supports coccyx and pulls it forward after it has been reflected posteriorly by defecation and childbirth  MUSCLES OF THE UROGENITAL DIAPHRAGM  - Deep transverse perineal muscle (deep far from surface; transverse across; perine near anus) - supports pelvic organs; steadies central tendon - External urethral sphincter (sphin squeeze) - constricts urethra; allows voluntary inhibition of urination; helps support pelvic organs MUSCLES OF THE SUPERFICIAL PERINEAL SPACE - Ischiocavernosus (ischi hip; caverna hollow chamber) - retards venous drainage and maintains erection of penis or clitoris - Bulbospongiosus (bulbon bulb; spongio sponge) - empties male urethra; assists in erection of penis and of clitoris - Superficial transverse perineal muscle (superficial closer to surface) - stabilizes and strengthens central tendon of perineum  PICTURE MUSCLES OF THE ANTERIOR THORAX - Pectoralis Minor (pectus chest, breast; minor lesser) - w/ ribs fixed, draws scapula forward and downward; with scapula fixed, draws rib cage superiorly - Serratus anterior (serratus saw) - rotates scapula so its inferior angle moves laterally and upward; prime mover to protract and hold scapula against chest wall; raises point of shoulder; important role in abducting and raising arm and in horizontal arm movements (pushing, punching); called "boxer's muscle" - Subclavius (sub under, beneath; clav clavicle) - helps stabilize and depress pectoral girdle PICTURE Superficial Muscles of the Anterior and Posterior Thorax: Movements of the Scapula and Arm MUSCLES OF THE POSTERIOR THORAX - Trapezius (trapezion irregular four-sided figure) - stabilizes, raises, retracts, and rotates scapula; middle fibers retract (adduct) scapula; superior fibers elevate scapula (as in shrugging the shoulders) or help extend head w/ scapula fixed; inferior fibers depressed scapula (and shoulder) - Levator Scapulae (levator raises) - elevates/adducts scapula in concert w/ superior fibers of trapezius; tilts glenoid cavity downward when scapula is fixed, flexes neck to the same side - Rhomboids (major and minor) (rhomboid diamond shaped) - stabilize scapula; act together (and w/ middle trapezius fibers) to retract (adduct) scapula, thus "squaring shoulders"; rotate scapula so that glenoid cavity is downward (as when lowering arm against resistance; eg. paddling a canoe) PICTURE Muscles Crossing the Shoulder Joint: Movements of the Arm (Humerus) - Pectoralis major (pectus breast, chest; major larger) - prime mover of arm flexion; rotates the arm medially; adducts arm, against resistance; with scapula (and arm) fixed, pulls rib cage upward, thus can help in climbing, throwing, pushing, and forced inspiration - Deltoid (delta triangular) - prime mover of arm abduction when all its fibers contract simultaneously;  - Latissimus dorsi (latissimus widest; dorsi = back) - prime mover of arm extension; powerful arm adductor; medially rotates arm at shoulder; PICTURE - Subscapularis (sub under; scular scapula) - chief medial rotator of humerus; assisted by pectoralis major; helps hold head of humerus in glenoid cavity, stabilizing shoulder joint - Supraspinatus (supra above, over; spin = spine) - initiates abduction; stabilizes shoulder joint; helps prevent downward dislocation of humerus, as when carrying a heavy suitcase - Infraspinatus (infra below) - rotates humerus laterally; helps hold head of humerus in glenoid cavity, stabilizing the shoulder joint - Teres minor (teres round: minor lesser) - same as infraspinatus muscle - Teres major - extends, medially rotates, and adducts humerus; synergist of latissimus dorsi - Coracobrachialis (coraco coracoid; brachi = arm) - flexes and adducts humerus;  synergist of the pectoralis major PICTURE Muscles Crossing the Elbow Joint: Flexion and Extension of the Forearm POSTERIOR MUSCLES - Triceps Brachii (triceps three heads; brachi = arm) - powerful forearm extensor (prime mover, particularly medial head); antagonist of forearm flexors; long and lateral heads mainly active in extending the forearm against resistance; long head tendon may help stabilize shoulder joining and assist in arm adduction - Anconeus (ancon elbow) - may control ulnar abduction during forearm pronation; synergist of triceps brachii in elbow extension  ANTERIOR MUSCLES - Biceps brachii (biceps two heads) - flexes elbow joint and supinates forearm; usually occurs at same time; weak flexor of arm at shoulder - Brachialis - major forearm flexor (lifts ulna as biceps lifts the radius) - Brachioradialis (radi radius, ray) - synergist in flexing forearm; acts to best advantage when forearm is partially flexed and semi pronated; stabilizes elbow during rapid flexion and extension Muscles of the Forearm: Movements of the Wrist, Hand, and Fingers PART I: ANTERIOR MUSCLES - eight muscles of the anterior fascial compartment are listed from the lateral to the medial aspect. Most arise from a common flexor tendon attached to the medial epicondyle of the humerus and have additional origins as well. Most of their tendons of insertion are held in place at the wrist by a thickening of deep fascia called the *flexor retinaculum.* SUPERFICIAL MUSCLES - Pronator teres (pronation turning palm posteriorly, or down; teres round) - pronates forearm; weak flexor of the elbow - Flexor carpi radialis (pronation turning palm posteriorly, or down; teres round) - powerful flexor of wrist abducts hand; weak synergist of elbow flexion - Palmaris longus (palma palm; longus = long) - Tenses skin and fascia of palm during hand movements; weak wrist flexor; weak synergist for elbow flexion - Flexor carpi ulnaris (ulnar ulna) - Powerful flexor of wrist, also adducts hand in concert with extensor carpi ulnaris (posterior muscle); stabilizes wrist during finger extension - Flexor digitorum superficialis (digit finger, toe; superficial close to surface) - Flexes wrist and middle phalanges of fingers 2-5; the important finger flexor for speed and flexion against resistance DEEP MUSCLES - Flexor pollicis longus (pollix thumb) - Flexes distal phalanx of thumb - Flexor digitorum profundus (profund deep) - Flexes distal interphalangeal joints; slow-acting flexor of any or all fingers; helps flex wrist PICTURE - Pronator quadratus (quad= square, four-sided) - Prime mover of forearm pronation; acts with pronator teres; also helps hold ulna and radius together PART II: POSTERIOR MUSCLES - These muscles of the posterior fascial compartment are listed from the lateral to the medial aspect. They are all innervated by the radial nerve or its branches. More than half of the posterior compartment muscles arise from a common extensor origin tendon attached to the posterior surface of the lateral epicondyle of the humerus and adjacent fascia. The extensor tendons are held in place at the posterior aspect of the wrist by the *extensor retinaculum*, which prevents \"bowstringing\" of these tendons when the wrist is hyperextended. The *extensor muscles* of the fingers end in a broad hood over the dorsal side of the digits, the extensor expansion. SUPERFICIAL MUSCLES - Brachioradialis (see Table 10.10) - Extensor carpi radialis longus (extend increase angle between two bones) - Extends wrist in conjunction with extensor carpi ulnaris and abducts wrist in conjunction with flexor carpi radialis - Extensor carpi radialis brevis (brevis short) - Extends and abducts wrist; acts synergistically with extensor carpi radialis longus to steady wrist during finger flexion - Extensor digitorum - Prime mover of finger extension; extends wrist; can abduct (flare) fingers - Extensor carpi ulnaris - Extends wrist in conjunction with extensor carpi radialis and adducts wrist in conjunction with flexor carpi ulnaris DEEP MUSCLES - Supinator (supination turning palm anteriorly or upward) - Assists biceps brachii to forcibly supinate forearm; works alone in slow supination; antagonist of pronator muscles - Abductor pollicis longus (abduct movement away from median plane) - Abducts and extends thumb - Extensor pollicis brevis and longus - Extends thumb PICTURE PICTURE PICTURE Intrinsic Muscles of the Hand: Fine Movements of the Fingers THENAR MUSCLES IN BALL OF THUMB - Abductor pollicis brevis (pollex thumb) - Abducts thumb (at carpometacarpal joint) - Flexor pollicis brevis - Flexes thumb (at carpometacarpal and metacarpophalangeal joints) - Opponens pollicis (opponens = opposition) - Opposition: moves thumb to touch tip of little finger - Adductor pollicis - Adducts and helps to oppose thumb HYPOTHENAR MUSCLES IN BALL OF LITTLE FINGER - Abductor digiti minimi (digiti minimi little finger) - Abducts little finger at metacarpophalangeal joint - Flexor digiti minimi brevis - Flexes little finger at metacarpophalangeal joints - Opponens digiti minimi - Helps in opposition:brings metacarpal V toward thumb to cup the hand PICTURE Intrinsic Muscles of the Hand: Fine Movements of the Fingers MIDPALMAR MUSCLES - Lumbricals (lumbric earthworm) - Flex fingers at metacarpophalangeal joints but extend fingers at interphalangeal joints - Palmar interossei (interossei- between bones) - Adduct fingers: pull fingers in toward third digit; act with lumbricals to extend fingers at interphalangeal joints and flex them at metacarpophalangeal joints - Dorsal interossei - Abduct (diverge) fingers; extend fingers at interphalangeal joints and flex them at metacarpophalangeal joints PART 1: ANTERIOR AND MEDIAL MUSCLES ORIGIN ON THE PELVIS OR SPINE - Iliopsoas - composite of two closely related muscles (iliacus and psoas major) whose fibers pass under the inguinal ligament to insert via a common tendon on the femur. - Iliacus (iliac ilium) - Iliopsoas is the prime mover for flexing thigh, or for flexing trunk on thigh as during a bow - Psoas major (psoa loin muscle; major larger) - As above; also flexes vertebral column laterally; important postural muscle - Sartorius (sartor tailor) - Flexes, abducts, and laterally rotates thigh; flexes knee (weak) as in a soccer kick; helps produce the cross-legged position PICTURE MUSCLES OF THE MEDIAL COMPARTMENT OF THE THIGH - Adductors - Large muscle mass consisting of three muscles (magnus, longus, and brevis) forming medial aspect of thigh; arise from inferior part of pelvis and insert at various levels on femur. All are used in movements that press thighs together, as when astride a horse; important in pelvic tilting movements that occur during walking and in fixing the hip when the knee is flexed and the foot is off the ground. Obturator nerve innervates entire group. Strain or stretching of this muscle group is called a \"pulled groin". - Adductor magnus (adduct = move toward midline; magnus large) - Anterior part adducts and medially rotates and flexes thigh; posterior part is a synergist of hamstrings to extend thigh - Adductor longus (longus long) - Adducts, flexes, and medially rotates thigh - Adductor brevis (brevis short) - Adducts, flexes, and medially rotates thigh - Pectineus (pecten comb) - Adducts, flexes, and medially rotates thigh - Gracilis (gracilis slender) - Adducts thigh, flexes and medially rotates leg, especially during walking MUSCLES OF THE ANTERIOR COMPARTMENT OF THE THIGH - Quadriceps femoris - Arises from four separate heads (quadriceps four heads) that form the flesh of front and sides of thigh. These heads (rectus femoris, and lateral, medial, and intermediate vasti muscles) have a common insertion tendon, the quadriceps tendon, which inserts into the patella and then via the patellar ligament into tibial tuberosity. The quadriceps is a powerful knee extensor used in climbing, jumping, running, and rising from seated position. The tone of quadriceps plays important role in strengthening the knee joint. Femoral nerve innervates the group. - Rectus femoris (rectus straight; femoris femur) - Extends knee and flexes thigh at hip - Vastus lateralis (vastus large; lateralis lateral) - Extends and stabilizes knee - Vastus medialis (medialis medial) - Extends knee Muscles Crossing the Hip and Knee Joints: Movements of the Thigh and Leg - Vastus intermedius (intermedius = inter- mediate) - Extends knee - Tensor fasciae latae (tensor to make tense; fascia band; lata = wide) - Steadies the knee trunk on thigh by making iliotibial tract taut; flexes and abducts thigh; rotates thigh medially PART II: POSTERIOR MUSCLES GLUTEAL MUSCLES-ORIGIN ON PELVIS - Gluteus maximus (glutos buttock; maximus largest) - Major extensor of thigh; complex, powerful, and most effective when thigh is flexed and force is necessary, as in rising from a forward flexed position and in thrusting the thigh posteriorly in climbing stairs and running; generally inactive during standing and walking; laterally rotates and abducts thigh - Gluteus medius (medius middle) - Abducts and medially rotates thigh; steadies pelvis; its action is extremely important in walking; e.g., muscle of limb planted on ground tilts or holds pelvis in abduction so that pelvis on side of swinging limb does not sag and foot of swinging limb can clear the ground - Gluteus minimus (minimus smallest) - As for gluteus medius LATERAL ROTATORS - Piriformis (piri pear; forma = shape) - Rotates extended thigh laterally; because inserted above head of femur, can also help abduct thigh when hip is flexed; stabilizes hip joint PICTURE MUSCLES CROSSING THE HIP AND KNEE JOINTS: MOVEMENTS OF THE THIGH AND LEG - Obturator externus (obturator obturator foramen; externus outside) - As for piriformis - Obturator internus (internus inside) - As for piriformis - Gemellus (superior and inferior) (gemin twin, double; superior above; inferior below) - As for piriformis - Quadratus femoris (quad four-sided square) - Rotates thigh laterally and stabilizes hip joint PICTURE MUSCLES OF THE POSTERIOR COMPARTMENT OF THE THIGH - Hamstrings - The hamstrings are fleshy muscles of the posterior thigh (biceps femoris, semitendinosus, and semimembranosus). They cross both the hip and knee joints and are prime movers of thigh extension and knee flexion. The group has a common origin site and is innervated by sciatic nerve (actually two nerves, the tibial and common fibular nerves wrapped in a common sheath). Ability of hamstrings to act on one of the two joints spanned depends on which joint is fixed-if knee is fixed (extended), they extend hip; if hip is extended, they flex knee. However, when hamstrings are stretched, they tend to restrict full accomplishment of antagonistic movement, e.g., if knees are fully extended, it is difficult to flex the hip fully (and touch your toes), and when the thigh is fully flexed as in kicking a football, it is almost impossible to extend the knee fully at the same time (without considerable practice). Name of this muscle group comes from old butchers\' practice of using their tendons to hang hams for smoking. \"Pulled hamstrings\" are common sports injuries in those who run very hard, e.g., football halfbacks. - Biceps femoris (biceps two heads) - Extends thigh and flexes knee; laterally rotates leg, especially when knee is flexed - Semitendinosus (semi half; tendinosus tendon) - Extends thigh and flexes knee; with semimembranosus, medially rotates leg - Semimembranosus (membranosus membrane) - Extends thigh and flexes knee; medially rotates leg Muscles of the Leg: Movements of the Ankle and Toes PART I: MUSCLES OF THE ANTERIOR COMPARTMENT - Tibialis anterior (tibial tibia; anterior = toward the front) -- prime mover of dorsiflexion; inverts foot; helps support medial longitudinal arch of foot - Extensor digitorum longus (extensor increases angle at a joint; digit = finger or toe; longus = long) - Prime mover of toe extension (acts mainly at metatarsophalangeal joints); dorsiflexes foot - Fibularis (peroneus) tertius (fibular fibula; tertius = third) - Dorsiflexes and everts foot - Extensor hallucis longus (hallux great toe) - Extends great toe; dorsiflexes foot PICTURE PICTURE PART II: MUSCLES OF THE LATERAL COMPARTMENT - These muscles have a common innervation, the superficial fibular nerve. Besides plantar flexion and foot eversion, these muscles stabilize the lateral ankle and lateral longitudinal arch of the foot. - Fibularis (peroneus) longus - Plantar flexes and everts foot; may help keep foot flat on ground - Fibularis (peroneus) brevis (brevis short) - Plaritar flexes and everts foot PART III: MUSCLES OF THE POSTERIOR COMPARTMENT - The muscles of the posterior compartment have a common innervation, the tibial nerve. They act in concert to plantar flex the ankle SUPERFICIAL MUSCLES - Triceps surae - Refers to muscle pair (gastrocnemius and soleus) that shapes the posterior calf and inserts via a common tendon into the calcaneus of the heel; this *calcaneal* or *Achilles tendon* is the largest tendon in the body. Prime movers of ankle plantar flexion - Gastrocnemius (gaster belly; kneme leg) - Plantar flexes foot when knee is extended; because it also crosses knee joint, it can flex knee when. foot is dorsiflexed - Soleus (soleus fish) - Plantar flexes foot; important locomotor and postural muscle during walking, running, and dancing - Plantaris (planta sole of foot) - Helps to flex knee and plantar flex foot DEEP MUSCLES - Popliteus (poplit back of knee) - Flexes and rotates leg medially to unlock extended knee when flexion begins; with tibia fixed, rotates thigh laterally - Flexor digitorum longus (flexor = decreases angle at a joint) - Plantar flexes and inverts foot; flexes toes; helps foot \"grip\" ground - Flexor hallucis longus - Plantar flexes and inverts foot, flexes great toe at all joints; \"push off\" muscle during walking - Tibialis posterior (posterior toward the back) - Prime mover of foot inversion; plantar flexes foot; stabilizes medial longitudinal arch of foot (as during ice skating) PICTURE PICTURE Intrinsic Muscles of the Foot: Toe Movement and Arch Support - help to flex, extend, abduct, and adduct the toes. MUSCLES ON DORSUM OF FOOT - Extensor digitorum brevis - Helps extend toes at metatarsophalangeal joints MUSCLES ON SOLE OF FOOT-FIRST LAYER (MOST SUPERFICIAL) - Flexor digitorum brevis - Helps flex toes - Abductor hallucis (hallux great toe) - Abducts great toe - Abductor digiti minimi - Abducts and flexes little toe MUSCLES ON SOLE OF FOOT-SECOND LAYER - Flexor accessorius (quadratus plantae) - Straightens out the oblique pull of flexor digitorum longus - Lumbricals - By pulling on extensor expansion, flex toes at metatarsophalangeal joints and extend toes at interphalangeal joints PICTURE Intrinsic Muscles of the Foot: Toe Movement and Arch Support MUSCLES ON SOLE OF FOOT-THIRD LAYER - Flexor hallucis brevis - Flexes great toe\'s metatarsophalangeal joint - Adductor hallucis - Helps maintain the transverse arch of foot; weak adductor of great toe - Flexor digiti minimi brevis - Flexes little toe at metatarsophalangeal joint MUSCLES ON SOLE OF FOOT-FOURTH LAYER (DEEPEST) - Plantar (3) and dorsal interossei (4) - See palmar and dorsal interossei (Table 10.13) PICTURE PICTURE PICTURE