Muscular System PDF - BS Nursing Level 1 Anatomy and Physiology

BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH TYPES OF MUSCLES WHOLE SKELETAL MUSCLE ANATOMY SKELETAL Skeletal muscle, or striated muscle, with o atta...

BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH TYPES OF MUSCLES WHOLE SKELETAL MUSCLE ANATOMY SKELETAL Skeletal muscle, or striated muscle, with o attached to bones its associated connective tissue, o striated constitutes approximately 40% of body o voluntarily controlled weight. CARDIAC Skeletal muscle is so named because ○ located in the heart many of the muscles are attached to the ○ striated skeletal system ○ involuntarily controlled Some skeletal muscles attach to the skin SMOOTH or connective tissue sheets. ○ located in blood vessels, hollow Skeletal muscle is also called striated organs muscles because transverse bands, or ○ non-striated striations, can be seen in the muscle ○ involuntarily controlled under the microscope. Individual skeletal muscles, such as the FUNCTIONS OF MUSCULAR SYSTEM biceps brachii, are complete organs, as a result of being comprised of several tissues: muscle, nerve, and connective tissue. CONNECTIVE TISSUE COVERINGS Each skeletal muscle is surrounded by a connective tissue sheath called the epimysium that forms a connective tissue sheath that surrounds each skeletal muscle. A skeletal muscle is subdivided into groups of muscle cells, termed fascicles. Each fascicle is surrounded by a connective tissue covering, termed the perimysium which subdivides each whole muscle into numerous, visible bundles of muscle fibers (cells) called fascicles. The perimysium is a loose FIGURE 1 connective tissue serving as 1. Movement passageways for blood vessels and 2. Maintain posture nerves that supply each fascicle. 3. Respiration Each skeletal muscle cell (fiber) is 4. Production of body heat surrounded by a connective tissue 5. Communication covering, termed the endomysium. It is 6. Constriction of organs and vessels a delicate layer of connective tissue that 7. Contraction of the heart separates the individual muscle fibers within each fascicle. The endomysium FUNCTIONAL PROPERTIES OF MUSCLES serves as passageways for nerve fibers Contractility - the ability of muscle to and blood vessels that supply each shorten forcefully, or contract separate muscle fiber. The protein fibers of the three layers of Excitability - the capacity of muscle to connective tissue blend into one another respond to a stimulus and merge at the ends of most muscles to form tendons, which attach muscle Extensibility- the ability to be stretched to bone. beyond its normal resting length and still be able to contract SKELETAL MUSCLE FIBER ANATOMY Elasticity- the ability of the muscle to Most skeletal muscle fibers range in size from about 1 millimeter (mm) to about 4 recoil to its original resting length after it centimeters (cm) in length, but some has been stretched Mora, Pablo, Pantin, Pique| 1 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH skeletal muscle fibers are as much as 30 MECHANICAL COMPONENT STRUCTURE cm (almost 1 foot) in length. Bundles of protein filaments are called A muscle fiber is a large cell, with myofibrils. several hundred nuclei located at its Myofibrils consist of two types of periphery. myofilaments, actin (thin filaments) Muscle fibers range in length 1 mm to 30 and myosin (thick filaments). cm. Actin and myosin are arranged into Alternating light and dark bands give repeating units called sarcomeres. muscle fibers a striated appearance. The myofilaments in the sarcomere The number of muscle fibers remains provide for the mechanical aspect of constant after birth so enlargement of muscle contraction. muscles results from an increase in the size of muscle fibers, not an increase in SARCOMERE fiber number. The sarcomere is the basic structural and functional unit of skeletal muscle. It ELECTRICAL COMPONENT STRUCTURE is the smallest portion of a muscle that The sarcolemma (cell membrane) has can contract many tubelike inward folds, called Sarcomeres join end to end to create transverse tubules, or T tubules. myofibrils. T tubules occur at regular intervals along Z disks are networks of protein fibers the muscle fiber and extend into the that serve as an anchor for actin center of the muscle fiber. myofilaments and separate one The T tubules are associated with sarcomere from the next. enlarged portions of the smooth A sarcomere extends from one Z disk to endoplasmic reticulum called the the next Z disk. sarcoplasmic reticulum. The organization of actin and myosin The enlarged portions are called myofilaments gives skeletal muscle its terminal cisternae striated appearance and gives it the Two terminal cisternae and their ability to contract. associated T tubule from a muscle triad The myofilaments slide past each other, The sarcoplasmic reticulum has a causing the sarcomeres to shorten. relatively high concentration of Ca2+, Each sarcomere consists of two which plays a major role in muscle light-staining bands separated by a contraction. dark-staining band. The cytoplasm of a muscle fiber is called Light bands, consist only of actin, and sarcoplasm which contains many are called I bands. They extend from bundles of protein filaments the Z disc, toward the center of the sarcomere, to the ends of the myosin myofilaments. It contain only actin myofilaments and thus appear lighter staining. Dark staining bands are called A bands. They extend the length of the myosin myofilaments. The center of each A band has a smaller band, called the H zone, and contains only myosin myofilaments. The middle of each H zone has a dark line, called M line. Actin and myosin myofilaments overlap for some distance on both ends of the A band; this overlap causes the contraction. MYOFILAMENT STRUCTURE Actin myofilaments are made up of three components: actin, troponin, and FIGURE 2: STRUCTURE OF SKELETAL MUSCLE tropomyosin. Troponin molecules have binding sites for Ca2+ and tropomyosin filaments Mora, Pablo, Pantin, Pique| 2 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH block the myosin myofilament binding sites on the actin myofilaments. Myosin myofilaments, or thick myofilaments, resemble bundles of tiny golf clubs. Myosin heads have ATP binding sites, ATPase and attachment spots for actin. FIGURE 4: NEUROMUSCULAR JUNCTION SLIDING FILAMENT MODEL When a muscle contracts, the actin and myosin myofilaments in the sarcomere slide past one another and shorten the sarcomere. When sarcomeres shorten, myofibrils, FIGURE 3: SKELETAL MUSCLE FIBER muscle fibers, muscle fascicles, and muscles all shorten to produce muscle NEUROMUSCULAR JUNCTION STRUCTURE contraction. During muscle relaxation, sarcomeres A motor neuron is a nerve cell that lengthen stimulates muscle cells. A neuromuscular junction is a EXCITABILITY OF MUSCLE FIBERS synapse where a neuron connects with a Muscle fibers are electrically excitable. muscle fiber. Electrically excitable cells are polarized. A synapse refers to the cell-to-cell The inside of the cell membrane is junction between a nerve cell and either negatively charged compared with the another nerve cell or an effector cell, outside. such as in a muscle or a gland. A voltage difference, or electrical charge A motor unit is a group of muscle fibers difference, exists across each cell that a single motor neuron stimulates. membrane. A presynaptic terminal is the end of a The charge difference is due to neuron cell axon fiber. differences in concentrations of ions on A synaptic cleft is the space between either side of the membrane. the presynaptic terminal and postsynaptic membrane. ION CHANNELS The postsynaptic membrane is the The phospholipid bilayer is impermeable muscle fiber membrane (sarcolemma). to ions. A synaptic vesicle is a vesicle in the Two types of membrane proteins, called presynaptic terminal that stores and ion channels, permit ions to pass releases neurotransmitter chemicals. through the membrane. Neurotransmitters are chemicals that ○ Leak channels allow the slow stimulate or inhibit postsynaptic cells. It leak of ions down their is a molecule that allows a neuron to concentration gradient. communicate with its target. ○ Gated channels may open or Acetylcholine is the neurotransmitter close in response to various types that stimulates skeletal muscles. of stimuli. RESTING MEMBRANE POTENTIAL The electrical charge difference across the cell membrane of an unstimulated Mora, Pablo, Pantin, Pique| 3 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH cell is called the resting membrane the cell becomes positive and the potential. outside negative. Muscle cells (fibers) have a resting Occurs because gated ion channels open membrane potential but can also when the cell is stimulated. perform action potentials. The diffusion of ions through these The resting membrane potential is due channels changes the charge across the to the inside of the membrane being cell membrane and produces an action negatively charged in comparison to the potential. outside of the membrane which is Action potential lasts for 1 to 3 positively charged. milliseconds. Action potentials are due to the The entry of Na+ causes the inside of membrane having gated channels. the cell membrane to become more The resting membrane potential exists positive than when the cell is at resting because of: membrane potential. This increase in positive charge inside 1. The concentration of K+ being higher on the cell membrane is called the inside of the cell membrane and the depolarization. concentration of Na+ being higher on If the depolarization changes the the outside membrane potential to a value called 2. The presence of many negatively threshold, an action potential is charged molecules, such as proteins, triggered inside the cell that are too large to exit An action potential is a rapid change in the cell charge across the cell membrane 3. The presence of leak channels in the The action potential travels across the membrane that are more permeable to sarcolemma. K+ than they are to Na+ Near the end of depolarization, the 4. Na+ tends to diffuse into the cell and K+ positive charge causes gated Na+ tends to diffuse out. channels to close and gated K+ channels 5. In order to maintain the resting to open. membrane potential, the Opening of gated K+ channels starts sodium-potassium pump recreates the repolarization of the cell membrane. Na+ and K+ ion gradient by pumping Repolarization is due to the exit of K+ Na+ out of the cell and K+ into the cell. from the cell The outward diffusion of K+ returns the cell to its resting membrane conditions and the action potential ends. In a muscle fiber, an action potential results in muscle contraction. FIGURE 5: RESTING MEMBRANE POTENTIAL FIGURE 6: RESTING MEMBRANE POTENTIAL ACTION POTENTIALS An action potential reverses the resting DEPOLARIZATION membrane potential so that the inside of Mora, Pablo, Pantin, Pique| 4 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH Change in charges inside becomes more potential in the muscle fiber which, in + and outside more - Na+ channels turn, stimulates the fiber to contract. open The action potential is stimulated by the release of acetylcholine from the motor neuron. FIGURE 7: DEPOLARIZATION REPOLARIZATION Na+ channels close change back to resting potential FIGURE 10: FUNCTION OF THE NEUROMUSCULAR JUNCTION MUSCLE CONTRACTION An action potential travels down the motor neuron to the presynaptic terminal. FIGURE 8: REPOLARIZATION The action potential causes Ca2+ channels to open and Ca2+ to enter the terminal. Ca2+ causes synaptic vesicles to release acetylcholine into synaptic cleft. Acetylcholine opens Na+ channels in the sarcolemma and causes an action potential. The action potential travels along the entire sarcolemma The action potential moves down T tubules. Action potentials open gate Ca2+ channels in the sarcoplasmic reticulum which releases stored calcium. Ca2+ binds to troponin which is attached to actin causing tropomyosin to move exposing attachment sites for myosin. Myosin heads bind to actin. Muscles contract when cross bridges move. FIGURE 9: ION CHANNELS AND ACTION POTENTIALS The heads of the myosin myofilaments bend,causing the actin to slide past the FUNCTIONS OF THE NEUROMUSCULAR myosin. As long as Ca2+ is present, the JUNCTION cycle repeats. Each muscle fiber is innervated by a branch of a motor neuron at a neuromuscular junction. Contact between the axon terminal and the sarcolemma results in an action Mora, Pablo, Pantin, Pique| 5 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH Energy for muscle contractions is supplied by ATP. Energy is released as ATP → ADP + Pi and energy from ATP is stored in myosin heads. A new ATP must bind to myosin before cross-bridge is released. Rigor mortis will occur when a person dies and no ATP is available to release cross-bridges. FIGURE 11: SKELETAL MUSCLE EXCITATION FIGURE 14: ATP BREAKDOWN AND CROSS-BRIDGE FIGURE 12: SKELETAL MUSCLE EXCITATION MOVEMENT MUSCLE RELAXATION Muscle relaxation occurs when acetylcholine is no longer released at the neuromuscular junction. Action potentials to the sarcoplasmic reticulum stop. Ca2+ is actively transported back into the sarcoplasmic reticulum using energy supplied by ATP. Ca2+ diffuses away from the troponin molecules and tropomyosin again blocks FIGURE 13: SKELETAL MUSCLE EXCITATION the attachment sites on the actin molecules. CROSS BRIDGE MOVEMENT The cross-bridge cycle stops and the The mechanical component of muscle muscle relaxes. contraction is called cross-bridge cycling. MUSCLE TWITCH The energy from one ATP molecule is A muscle twitch is a single contraction of required for one cross bridge cycle. a muscle fiber in response to a stimulus. A muscle twitch has three phases: ATP AND MUSCLE CONTRACTIONS latent phase, contraction phase, and relaxation phase. Mora, Pablo, Pantin, Pique| 6 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH The lag phase or latent phase is the Small, delicate muscles have very few time between the application of a fibers per motor unit. stimulus and the beginning of Large, powerful, less precise muscles contraction. have fewer, larger motor units. The contraction phase is the time during which the muscle contracts and FORCE OF CONTRACTION IN INDIVIDUAL the relaxation phase is the time during MUSCLE FIBERS which the muscle relaxes. The relaxation phase of much longer Individual muscle fibers can generate than the contraction phase, because the different amounts of force. concentration of Ca+ in the sarcoplasm The amount of force generated depends decreases slowly due to active transport upon the number of cross-bridges into the sarcoplasmic reticulum formed. More cross-bridges creates more force. One factor that influences the number of cross-bridges formed is the frequency of stimulation. A low frequency of stimuli allows a muscle fiber to undergo twitches that contract then fully relax. If the frequency of stimuli increases, the muscle fiber is unable to relax completely between twitches, more cross bridges form and summation occurs. The tension generated by the muscle increases. SUMMATION AND RECRUITMENT Muscles stimulated at greater FIGURE 15: MUSCLE TWITCH frequencies first display wave summation followed by Incomplete TYPES OF CONTRACTIONS Tetanus occurs when the frequency of There are two types of muscle stimulation only allows for partial contractions: isometric and isotonic. relaxation of the muscle fiber. 1. The isometric contraction has an Tetanus is a sustained contraction that increase in muscle tension, but no occurs when the frequency of change in length. The muscles does not stimulation is so rapid that no relaxation shorten and this happen if you try to lift occurs. something that is far too heavy for you Recruitment is the stimulation of several motor units. 2. The isotonic contraction increases the tension in a muscle and decreases the length. The muscles shortens and it happen anytime you move your limbs in order to lift and object and move it SUMMATION AND RECRUITMENT The strength of muscle contraction strength depends on two factors: 1. The amount of force in an individual muscle fiber, called summation 2. The amount of force in a whole muscle, called recruitment MOTOR UNIT A motor unit consists of a single motor FIGURE 16: MULTIPLE-WAVE SUMMATION neuron and all the muscle fibers it innervates. MUSCLE TONE An action potential in the neuron of a Muscle tone is the constant tension motor unit causes contraction of all the produced by body muscles over long muscle fibers in that unit. periods of time. Mora, Pablo, Pantin, Pique| 7 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH Muscle tone is responsible for keeping ○ The Ca2+ pump in the the back and legs straight, the head in sarcoplasmic reticulum an upright position, and the abdomen from bulging. Muscle fibers store enough ATP to Muscle tone depends on a small contract for about 5–6 seconds. If percentage of all the motor units in a contraction is to continue beyond this muscle being stimulated at any point in time, more ATP must be produced. time, causing their muscle fibers to contract tetanically and out of phase ATP is derived from four processes in with one another. skeletal muscle. TYPES OF ISOTONIC CONTRACTIONS 1.Conversion of two ADP to one ATP and 1. Concentric contractions are isotonic one adenosine monophosphate (AMP) by contractions in which muscle tension the enzyme adenylate kinase increases as the muscle shortens. It 2.Transfer of a phosphate from a molecule result in an increasing tension as the called creatine (krē′a-tēn) phosphate muscle shortens by the enzyme creatine kinase from ADP to form ATP 2. Eccentric contractions are isotonic 3. Anaerobic production of ATP during contractions in which tension is intensive short-term exercise maintained in a muscle, but the 4. Aerobic production of ATP during most opposing resistance causes the muscle exercise and normal conditions to lengthen. ATP PRODUCTION AS EXERCISE TYPES OF SKELETAL MUSCLE FIBER PROGRESSES SLOW TWITCH FIBERS (Type I) Muscle fibers store enough ATP for about ○ contract slowly 5 to 6 seconds of contraction. ○ fatigue slowly Next, ATP production by adenylate ○ have a considerable amount of kinase and creatine kinase occurs. This myoglobin is depleted after about 15 seconds. ○ use aerobic respiration When a muscle fiber is working too ○ are dark in color strenuously for ATP stores and creatine ○ used by long distance runners phosphate to be able to provide enough ○ contain large amounts of ATP, anaerobic respiration predominates. myoglobin Fast-twitch muscle fibers are the primary anaerobic muscle fibers. FAST TWITCH FIBERS (Type II) Slow-twitch fibers utilize aerobic ○ contract quickly pathways. ○ fatigue quickly The lactate produced by anaerobic ○ use anaerobic respiration fast-twitch fibers is used as a starting ○ energy from glycogen point for aerobic ATP production in ○ light color slow-twitch fibers. ○ used by sprinters Most human muscles have a blend of MUSCLE FATIGUE fast twitch and slow twitch fibers. The Fatigue is a temporary state of reduced amount of each type varies for each work capacity. muscle. Without fatigue, muscle fibers would be The large postural muscles of the back worked to the point of structural damage and lower limbs contain more to them and their supportive tissues. slow-twitch fibers. The muscles of the upper limbs contain Mechanisms of fatigue include: more fast-twitch muscle fibers. ENERGY FOR MUSCLE CONTRACTIONS Acidosis and ATP depletion due to either Muscle fibers have three ATP dependent an increased ATP consumption or a proteins decreased ATP production ○ The myosin head Oxidative stress, which is characterized ○ The Na+/K+ ATPase to maintain by the buildup of excess reactive oxygen resting membrane potential species (ROS; free radicals) Local inflammatory reactions Mora, Pablo, Pantin, Pique| 8 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH A retinaculum is a band of connective MUSCLE SORENESS tissue that holds down the tendons at Following vigorous exercise, people each wrist and ankle. sometimes experience muscle pain, Skeletal muscle attachments have an which can last for several days. origin and an insertion, with the origin The pain is related to the effects of being the attachment at the least mobile inflammatory chemicals on the muscle location. fibers. The insertion is the end of the muscle Exercise schedules that alternate attached to the bone undergoing the exercise with periods of rest, such as greatest movement. lifting weights every other day, provide The part of the muscle between the time for the repair of muscle tissue. origin and the insertion is the belly. A group of muscles working together are OXYGEN DEFICIT called agonists. There are two distinct phases of O2 use: A muscle or group of muscles that oppose muscle actions are termed 1. Oxygen deficit is the lag time between antagonists. when a person begins to exercise and when they begin to breathe more heavily because of the exercise. 2. Excess postexercise oxygen consumption is the lag time before breathing returns to its pre exercise rate once exercise stops. SMOOTH MUSCLE Smooth muscle cells are non-striated small, spindle-shaped muscle cells, usually with one nucleus per cell. The myofilaments are not organized into sarcomeres. The cells comprise organs controlled involuntarily, except the heart. Neurotransmitter substances, hormones, FIGURE 17: MUSCLE ATTACHMENT and other factors can stimulate smooth muscle. MUSCLE NAMES CARDIAC MUSCLE Muscles are named according to: Cardiac muscle cells are long, striated, 1.Location– a pectoralis muscle is located in and branching, with usually only one the chest. nucleus per cell. 2. Size– the size could be large or small, Cardiac muscle is striated as a result of short or long. the sarcomere arrangement. 3. Shape- the shape could be triangular, Cardiac muscle contraction is quadrate, rectangular, or round. autorhythmic. 4. Orientation Of Fascicles– fascicles could Cardiac muscle cells are connected to run straight (rectus) or at an angle one another by specialized structures (oblique). that include desmosomes and gap 5. Origin And Insertion- The junctions called intercalated disks. sternocleidomastoid has its origin on the Cardiac muscle cells function as a single sternum and clavicle and its insertion on unit in that action potential in one the mastoid process of the temporal cardiac muscle cell can stimulate action bone. potentials in adjacent cells. 6. Number Of Heads- A Biceps Muscle Has Two Heads (origins), and a triceps SKELETAL MUSCLE ANATOMY muscle has three heads (origins). A tendon connects skeletal muscle to 7. Function- Abductors and adductors are bone. the muscles that cause abduction and Aponeuroses are broad, sheetlike adduction movements. tendons. Mora, Pablo, Pantin, Pique| 9 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH FIGURE 18: SKELETAL MUSCLES ANTERIOR VIEW FIGURE 20: MUSCLES OF FACIAL EXPRESSION AND MASTICATION FIGURE 21: TONGUE AND SWALLOWING MUSCLES FIGURE 19: SKELETAL MUSCLES POSTERIOR VIEW MUSCLES OF MASTICATION TEMPORALIS MASSETER PTERYGOIDS (TWO PAIRS) Mora, Pablo, Pantin, Pique| 10 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH Internal abdominal oblique: ○ compresses abdomen Transverse abdominis: ○ compresses abdomen FIGURE 24: MUSCLES OF THE ANTERIOR ABDOMINAL WALL FIGURE 22: DEEP NECK AND BACK MUSCLES PELVIC DIAPHRAGM MUSCLES THORACIC MUSCLES - Levator ani External intercostals: - Ischiocavernosus ○ elevate ribs for inspiration - Bulbospongiosus Internal intercostals: - Deep transverse perineal ○ depress ribs during forced - Superficial transverse perineal expiration Diaphragm: ○ moves during quiet breathing FIGURE 25: PELVIC DIAPHRAGM MUSCLES UPPER SCAPULAR AND LIMB MUSCLES 1 Trapezius: ○ shoulders and upper back ○ extends neck and head Pectoralis major: FIGURE 23: MUSCLES OF THE THORAX ○ chest ABDOMINAL WALL MUSCLES ○ elevates ribs Rectus abdominis: Serratus anterior: ○ center of abdomen ○ between ribs ○ compresses abdomen ○ elevates ribs External abdominal oblique: Deltoid: ○ sides of abdomen ○ shoulder ○ compresses abdomen ○ abductor or upper limbs Mora, Pablo, Pantin, Pique| 11 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH FIGURE 26: MUSCLES OF THE SHOULDER UPPER LIMB MUSCLE FIGURE 28: MUSCLES OF THE FOREARM Triceps brachii: ○ 3 heads MUSCLES OF HIPS AND THIGHS ○ extends elbow Iliopsoas: Biceps brachii: ○ flexes hip ○ “flexing muscle” Gluteus maximus: ○ flexes elbow and shoulder ○ buttocks Brachialis: ○ extends hip and abducts thigh ○ flexes elbow Gluteus medius: Latissimus dorsi: ○ Hip ○ lower back ○ abducts and rotates thigh ○ extends shoulder MUSCLES OF THE UPPER LEG 1 The quadriceps femoris is comprised of 4 thigh muscles: The rectus femoris: ○ front of thigh ○ extends knee and flexes hip The vastus lateralis: ○ extends knee The vastus medialis: ○ extends knee The vastus intermedius: ○ extends knee Gracilis: ○ adducts thigh and flexes knee Biceps femoris, semimembranosus, semitendinosus: ○ Hamstring FIGURE 27: ARM MUSCLES ○ back of thigh ○ flexes knee, rotates leg, extends FOREARM MUSCLES hip - Flexor longus The rectus femoris: - Flexor carpi radialis ○ front of thigh - Flexor carpi ulnaris ○ extends knee and flexes hip - Flexor digitorum profundus The vastus lateralis: - Flexor digitorum superficialis ○ extends knee - Pronator The vastus medialis: - Brachioradialis ○ extends knee - Extensor carpi radialis brevis The vastus intermedius: Mora, Pablo, Pantin, Pique| 12 BS NURSING LEVEL 1: ANATOMY AND PHYSIOLOGY (MC 1) MUSCULAR SYSTEM Dr. Mary Villarose C. Gaspan, RpH ○ extends knee FIGURE 30: LOWER LEG MUSCLES REFERENCES *PPT* FIGURE 29: MUSCLE OF THE HIP AND THIGH MUSCLES OF LOWER LEG Tibialis anterior: ○ front of lower leg ○ inverts foot Gastrocnemius: ○ calf ○ flexes foot and leg Soleus: ○ attaches to ankle ○ flexes foot Mora, Pablo, Pantin, Pique| 13