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Skeletal Muscles Attach to bones Produce skeletal movement (voluntary)

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1 Skeletal Muscles Attach to bones Produce skeletal movement (voluntary)
Maintain posture Support soft tissues Regulate entrances to the body Maintain body temperature

2 Properties of Skeletal Muscles
Electrical excitability -ability to respond to stimuli by producing action potentials -two types of stimuli: 1. autorhythmic electrical signals 2. chemical stimuli – e.g. neurotransmitters Contractility -ability to contract when stimulated by an action potential -isotonic contraction: tension develops, muscle shortens -isometric contraction: tension develops, length doesn’t change Extensibility -ability to stretch without being damaged -allows contraction even when stretched Elasticity -ability to return to its original length and shape

3 Muscles: Gross Anatomy
muscles with similar functions are grouped and held together by layers of deep fascia e.g. biceps femoris and brachialis – forearm flexion three layers of connective tissue surround a muscle Epimysium – divides a muscle into fasicles Perimysium – divides a fasicle into muscle fibers Endomysium – divides a muscle fiber into myofibrils

4 Gross Anatomy muscles are surrounded by a fascia (areolar tissue)
remove the fascia – epimysium that surrounds the muscle and divides it into groups called fascicles each individual fascicle is surrounded by a perimysium perimysium divides the fascicle into muscle fibers muscle fiber = individual muscle cell each muscle fiber/muscle cell is surrounded by an endomysium endomysium divides the muscle fiber into protein filaments = myofibrils myofibrils contain a “skeleton” of protein filaments (myofilaments) organized as sarcomeres

5 Muscles: Gross Anatomy
epimysium and perimysium extend off the muscle to become organized as a tendon – attaches to the periosteum of the bone

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7 Microanatomy of Skeletal Muscle Fibers
large, multinucleated cells called fibers mature muscle fibers range from 10 to 100 microns in diameter typical length is 4 inches - some are 12 inches long muscle fibers increase in size during childhood = human GH & testosterone testosterone also increases muscle size embryonic development – stem cells (satellite cells) differentiate into immature myoblasts which begin to make the proteins of the myofibrils (i.e. the myofilaments) myoblasts mature into myocytes multiple myocytes fuse to form the muscle cell (muscle fiber) muscle fibers cannot divide through mitosis number of muscle cells predetermined before birth – they get larger as we grow satellite cells can repair damaged/dying skeletal muscle cells throughout adulthood

8 Muscle Cell Anatomy new terminology cell membrane = sarcolemma
cytoplasm = sarcoplasm large amounts of glycogen and myoglobin surrounds the myofibrils myofibrils made up of myofilaments actin & myosin transverse tubules ingrowths of the sarcolemma carry the action potential deep into the fiber flanks the sarcoplasmic reticulum novel internal membrane system = sarcoplasmic reticulum for calcium storage

9 The Proteins of Muscle contractile elements of the myofibrils = myofilaments -2 microns in diameter -give the muscle its striated appearance myofilaments are built of 3 kinds of protein contractile proteins myosin and actin regulatory proteins which turn contraction on & off troponin and tropomyosin structural proteins which provide proper alignment, elasticity and extensibility titin, myomesin, nebulin, actinin and dystrophin two kinds of myofilaments Thin - actin, troponin and tropomyosin Thick – myosin only

10 Sarcomere Structure myosin/thick filament only region = H zone
M line myosin/thick filament only region = H zone thin filament only region = I band length of myosin/thick filaments = A band contraction = “sliding filament theory” thick and thin myofilaments slide over each other and sarcomere shortens

11 Sarcomere Structure sarcomere = regions of myosin (thick myofilament) and actin (part of thin myofilament) bounded by two Z lines thin filaments project out from Z line – actin attached via actinin (structural protein) myosin/thick filaments lie in center of sarcomere - overlap with thin filaments and connect to them via cross-bridges myosin/thick filaments are held in place at the M line at the center and by titin at the Z-line

12 Contraction: The Sliding Filament Theory
Actin proteins in the thin filament have myosin binding sites these sites are “covered up” by troponin and tropomyosin in relaxed muscle removal of troponin/tropomyosin from these sites is required for contraction removal of troponin/tropomyosin is done through binding of calcium to troponin calcium is released from the sarcoplasmic reticulum upon the action potential

13 Contraction: The Sliding Filament Theory
myosin/thick myofilament is a bundle of myosin molecules myosin looks like a “golf club” with a head, a hinge region and a shaft each myosin protein has a globular “head” with a site to bind and breakdown ATP (ATPase site) and to bind actin (actin binding site) binding of actin and myosin binding sites = cross-bridging

14 -for cross bridging- you will need two things:
Increase in Cai Removal of troponin-tropomyosin CONTRACTION Sliding of actin along myosin RESETTING of system -for cross bridging- you will need two things: 1. calcium – uncovers the myosin binding sites on actin – “pushes aside” the troponin- tropomyosin complex 2. myosin head bound to ADP -for contraction – i.e. pivoting of the myosin head into the M line – the myosin head must be empty -to “reset” for a new cycle of cross-bridging – the myosin head must detach and pivot back -the myosin head must bind ATP -once the myosin head pivots back – the ATP is broken down to ADP – head is ready to cross-bridge again – if actin is “ready”

15 Contracted Sarcomere https://www.youtube.com/watch?v=BMT4PtXRCVA

16 The Neuromuscular Junction
the motor neuron’s synaptic terminal is in very close association with the muscle fiber distance between the bulb and the folded sarcolemma = neuromuscular junction neurotransmitter released = acetylcholine https://www.youtube.com/watch?v=7wM5_aUn2qs

17 The “Big Picture” AP generated at trigger zone in
pre-synaptic motor neuron 2. AP arrives in synaptic end bulb – causes entry of calcium into end-bulb release of of acetylcholine/Ach Binding of Ach to ligand-gated Na channels on muscle sarcolemma (i.e. Ach receptors) Na+ enters muscle cell = depolarization Muscle membrane potential reaches threshold  Action Potential 6. AP travels along sarcolemma into T-tubules 7. AP “passes by” sarcoplasmic reticulum  release of calcium into sarcoplasm 8. Ca binds troponin-tropomyosin complex & “shifts” it off myosin binding site 9. Cross-bridging between actin and myosin, pivoting of myosin head = Contraction (ATP dependent)

18 Contraction vs. Relaxation
Acetylcholinesterase (AchE) breaks down ACh calcium pumped back into sarcoplasmic reticulum Limits duration of contraction

19 Action Potentials in Nerve and Muscle
Entire muscle cell membrane versus only the axon of the neuron is involved Resting membrane potential nerve is -70mV skeletal & cardiac muscle is closer to -90mV Duration nerve impulse is 1/2 to 2 msec muscle action potential lasts 1-5 msec for skeletal & msec for cardiac & smooth Fastest nerve conduction velocity is 18 times faster than velocity over skeletal muscle fiber

20 Motor Units Each skeletal fiber has only ONE NMJ
motor unit = somatic motor neuron + all the skeletal muscle fibers it innervates number and size of motor units indicate precision of muscle control Motor units fire asynchronously some fibers are active others are relaxed delays muscle fatigue so contraction can be sustained motor units are also intermingled the net distribution of force applied to the tendon remains constant even when a fraction of muscle fibers are relaxed Muscle twitch Single momentary contraction of a motor unit Response to a single stimulus

21 Muscle Metabolism Production of ATP: -contraction requires huge amounts of ATP -muscle fibers produce ATP three ways: 1. Creatine phosphate 2. Anaerobic metabolism 3. Aerobic metabolism

22 Creatine Phosphate Muscle fibers at rest produce more ATP then they need for resting metabolism Excess ATP within resting muscle used to form creatine phosphate creatine – arginine, glycine and methionine made by kidneys and liver phosphorylated by the enzyme creatine kinase takes a phosphate off of ATP and transfers it creatine takes the phosphate off of creatine phosphate and transfers it back to ADP – to make ATP Creatine phosphate: 3-6 times more plentiful than ATP within muscle Sustains maximal contraction for 15 sec (used for 100 meter dash). Athletes often use creatine supplementation gain muscle mass but shut down bodies own synthesis (safety?)

23 Anaerobic Cellular Respiration
Muscles deplete creatine – can make ATP in anaerobically or aerobically Glycogen converted into glucose first ATP produced from the breakdown of glucose into pyruvic acid (sugar) during glycolysis if no O2 present (anaerobic) - pyruvic converted to lactic acid which diffuses into the blood Glycolysis can continue anaerobically to provide ATP for 30 to 40 seconds of maximal activity (200 meter race) If O2 is present the pyruvic acid is converted into acetyl coA (aerobic)

24 Aerobic Cellular Respiration
ATP for any activity lasting over 30 seconds if sufficient oxygen is available, pyruvic acid is converted into acteyl coA Acetyl coA enters the mitochondria to enter the Kreb’s cycle Kreb’s cycle generates NADH and FADH2 (electron carriers) The electrons are carried to an enzymes located on the inner mitochondrial membrane The electrons are then transported along three complexes of enzymes – ultimately transported to oxygen This results in the synthesis of ATP, water and heat Provides 90% of ATP energy if activity lasts more than 10 minutes Each glucose = 36 ATP fatty acids and amino acids can also be used by the mitochondria Fatty acid = ~100 ATP Sources of oxygen – diffusion from blood, released by myoglobin

25 Types of Muscle Fibers Proportions vary with the muscle
classified on how they make their ATP Fast fibers = fast glycolytic Slow fibers = slow oxidative Intermediate fibers = fast glycolytic-oxidative Percentage of fast versus slow fibers is genetically determined Proportions vary with the muscle neck, back and leg muscles have a higher proportion of postural, slow oxidative fibers shoulder and arm muscles have a higher proportion of fast glycolytic fibers

26 Fast Fibers: Large in diameter Contain densely packed myofibrils
Large glycogen reserves powerful, explosive contractions fatigue quickly Fast oxidative-glycolytic (fast-twitch A) red in color (lots of mitochondria, myoglobin & blood vessels) split ATP at very fast rate; used for walking and sprinting Fast glycolytic (fast-twitch B) white in color (few mitochondria & BV, low myoglobin) anaerobic movements for short duration; used for weight-lifting Slow fibers: Half the diameter of fast fibers Three times longer to contract Continue to contract for long periods of time longest to fatigue e.g. marathon runners

27 Classification According to arrangement of fibers and fascicles
Parallel muscles Parallel to long axis of muscle Convergent muscles Fibers converge on common attachment site Pennate muscles One or more tendons run through body of muscle Unipennate, bipennate, multipennate Circular muscles Fibers concentrically arranged

28 Bones & Muscles: Origins and Insertions
Origin – portion of the skeletal muscle that attaches to the more stationary structure Insertion - portion of the skeletal muscle that attaches to the more moveable structure majority of muscles originate or insert from bony markings on the skeleton markings: specific elevations, depressions, and openings of bones bony markings provide distinct and characteristic landmarks for orientation and identification of bones and associated structures. many markings come together to form a joint many markings are often the sites for the origins or insertions of muscles, or a channel for the passage of nerves and vessels 3 kinds of bony markings: depressions – fossa, fissure openings – foramen, canal, meatus processes – condyles, spines, crests, heads, lines, ridges, trochanters, tubercles

29 Muscle Names Yield clues to muscle orientation, location or function
Biceps brachii (two heads, arm) Vastus femoris (large, femur) Orbicularis oculi (circular, eye) Rectus abdominus (erect, abdomen)

30 Musculoskeleton: Axial Division
Axial skeleton: 80 bones main axis of the body forms a framework for the protection of delicate organs including the sense organs Axial musculature axial musculature arises from and inserts on the axial skeleton responsible for positioning the head and spinal column – postural muscles also moves the rib cage, assisting in breathing grouped into 4 groups: 1. muscles of the head and neck 2. muscles of the vertebral column 3. the abdominals - oblique and rectus muscles 4. muscles of the pelvic floor

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33 Muscles of the Head and Neck
Muscles of facial expression – know for practical Extrinsic eye muscles – know for practical Muscles of mastication – check your list for practical Muscles of the tongue – check your list for practical Muscles of the pharynx – don’t worry about these Muscles of the anterior neck – know for practical

34 Muscles of Facial Expression
Originate on surface of skull Largest group associated with mouth Orbicularis oris Buccinator Occipitofrontalis muscle Movement of eyebrows, forehead, scalp Platysma Skin of neck, depresses mandible

35 Muscles of Facial Expression
Orbicularis oris - puckering Buccinator - whistling Occipitofrontalis muscle (Epicranius) movement of eyebrows, forehead, scalp Front belly = Frontalis (moves eyebrows and forehead) Back belly = Occipitalis (moves back of scalp) Zygomaticus Major and Minor - smiling Risorius - grinning Orbicularis oculi – closes eye Depressor anguli oris - – lowers angle of mouth Depressor labii inferioris –depresses lower lip Levator labii superioris – raises upper lip Mentalis - pouting Platysma – pouting & depresses mandible originate on surface of skull – insert on the skin of the face

36 zygomaticus minor zygomaticus major

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38 Muscles of Mastication
Act on the mandible Temporalis – elevates mandible Masseter – elevates mandible Medial pterygoid & Lateral pterygoid protract the mandible and move it side to side Don’t need to know for practical

39 Six Extra-Ocular (Oculomotor) Muscles
Inferior rectus Superior rectus Medial rectus Lateral rectus Superior oblique Inferior oblique

40 Muscles of the Tongue Necessary for speech and swallowing Genioglossus
Hyoglossus Palatoglossus Styloglossus palatoglossus temporalis styloglossus hyoglossus mylohyoid

41 Anterior Muscles of the Neck
foundation for the muscles of the tongue and pharynx, move the hyoid up or down for swallowing & breathing, depress the mandible Digastric – two bellies Mylohyoid Stylohyoid Sternohyoid Sternothyroid Thyrohyoid Omohyoid

42 Anterior Muscles of the Neck
Foundation for the muscles of the tongue and pharynx Digastric Mylohyoid Stylohyoid Sternocleidomastoid omohyoid thyrohyoid sternohyoid thyroid gland

43 Anterior Muscles of the Neck
Sternocleidomastoid two sites of origin – clavicle and sternum inserts onto mastoid process both together – flexes head forward individually – laterally flexes & rotates head to the opposite side

44 Anterior Muscles of the Neck

45 Muscles of the Vertebral Column
covered by a superficial layer of back muscles Trapezius Latissimus dorsi superficial and deep layers quite complex – multiple origins and insertions + overlapping 5 Groups: Splenius group Erector spinae group Scalenes Transversospinalis group Segmental group

46 Muscles of the Vertebral Column
Superficial muscles: Splenius group – together they extend the head and neck, individually they laterally flex and rotate to the same side Splenius capitis Splenius cervicis

47 Muscles of the Vertebral Column
Superficial muscles: Erector Spinae - spinal extensors comprised of capitis, cervicis, thoracic and lumborum portions Spinalis – medial group of muscles capitis, cervicis and thoracis groups Iliocostalis – lateral group of muscles cervicis, thoracis and lumborum Longissimus – in between these two (intermediate) capitis, cervicis and thoracis lumborum portion fuses with iliocostalis

48 Muscles of the Vertebral Column
Deep muscles: Interconnect and stabilize the vertebrae Scalenes – flexes and rotates neck, used in deep inspiration Anterior Medial Posterior Transversospinal group – extends the vertebral column and rotates it to the opposite side Semispinalis – capitis, cervicis and thoracis portions runs from transverse to spinous processes Multifidus – below the ribcage semispinalis is called mutifidis Rotatores

49 Muscles of the Vertebral Column
Deep muscles: Quadratus lumborum - flexes the lumbar spine Segmental group – extends and laterally flexes vertebral column Interspinales – run between spinous processes Intertransversarii – run between transverse processes

50 The Oblique and Rectus Muscles
Abdominal Oblique and Rectus Muscles Rectus abdominus – partitioned into 4 sections by fibrous “tendinous intersections” 3 Abdominal oblique muscles External oblique (down and in) Internal oblique (up and in) Transversus abdominis (side to side) Compress underlying organs together – flex the vertebral column singly - rotate the vertebral column to the opposite side -the oblique muscles are connected to their opposite partners via an aponeurosis (broad, flat tendon) -the 3 aponeuroses form an “envelope” that encloses the rectus abdominus = rectus sheath

51 The Diaphragm

52 The Pelvic Floor & Perineum
pelvic diaphragm or floor = coccygeus & levator ani & external anal sphincter found in the anal triangle- contains the anus supports pelvic viscera & resists increased abdominal pressure during defecation, urination, coughing, vomiting, etc pierced by anal canal, vagina & urethra additional muscles lie superficial to the pelvic floor = perineal muscles found in the urogenital triangle- contains the external genitalia also contains muscles – assist in the erection (male and female)

53 Muscles of the Pelvic Floor

54 Musculoskeleton: Appendicular Division
Appendicular skeleton: 126 bones Bones of upper and lower limbs Pectoral and pelvic girdles connect limbs to trunk Appendicular musculature originates or inserts on the appendicular skeleton stabilizes or moves components of the appendicular skeleton stabilizes pectoral girdle (i.e. shoulder joint) stabilizes pelvic girdle (i.e. hip joint) moves the upper and lower limbs grouped into 7 distinct groups: 4 groups move the upper limb 3 groups move the lower limb

55 Muscles that move the pectoral girdle
clavicle can be elevated or depressed or stabilized subclavius muscle movements of the scapula are quite complex adduction/retraction – rowing abduction/protraction – punching or ‘hunching’ of shoulders elevation – shrugging depression – pull-downs superior rotation – jumping jack inferior rotation – parallel bars

56 Muscles that move the pectoral girdle
POSTERIOR MUSCLES: Trapezius muscle – one of the largest muscles on the back affects position of pectoral girdle, neck, head -can perform a series of complex motions -divided into clavo-, acromio- and spino- sections (superior, medial and inferior fibers) -origin: occipital bone, C7 & all thoracic vertebrae -insertion – spine of scapula and lateral 1/3 of clavicle -superior fibers – elevate and superiorly rotate scapula -medial fibers – retract scapula -inferior fibers – depress scapula

57 Muscles that move the pectoral girdle
POSTERIOR MUSCLES Rhomboid muscles: major and minor adducts scapula origin: C7 to T5 vertebrae insertion: on medial border of scapula Levator scapulae muscle elevates scapula origin: C1 through C4 insertion: medial border of scapula (above the spine)

58 Serratus anterior muscle abducts scapula origin: first 9 ribs
ANTERIOR MUSCLES Serratus anterior muscle abducts scapula origin: first 9 ribs insertion: medial border of scapula Subclavius depresses the clavicle Pectoralis minor rotates it down (inferior) origin: ribs 3-5 insertion: corocoid process of scapula

59 Muscles that Move the Arm
Deltoid can be divided into anterior, medial and posterior fibers major arm abductor anterior fibers: flex and medially rotate arm medial fibers: prime mover; abduction of arm posterior fibers: extend and laterally rotate arm origin: spine of scapula, acromion and lateral 1/3 of clavicle insertion: deltoid tuberosity of humerus

60 Muscles that Move the Arm
Rotator Cuff muscles: surround and stabilize the glenohumeral joint origin: bony fossae and inferior angle of scapula insertion: lesser or greater tubercle of humerus Supraspinatus abducts the arm Supscapularis rotates arm medially Infraspinatus adducts and rotates arm laterally Teres minor

61 Muscles that Move the Arm
Coracobrachialis flexion and adduction at shoulder origin at corocoid process of scapula insertion on the humerus Pectoralis major muscle flexes arm shoulder adducts and medially rotates arm origin: clavicle, sternum and costal cartilages insertion: greater tubercle of humerus Latissumus dorsi muscle extends arm at shoulder origin: all lumbar vertebrae, sacrum and coccyx insertion: intertubercular groove of humerus

62 Summary: Muscle Actions at the Shoulder Joint
Abduction: Deltoid (middle) Supraspinatus Flexion: Pectoralis Major Deltoid (anterior) Coracobrachialis Lateral Rotation: Infraspinatus Teres minor Deltoid (posterior) prime movers in bold Adduction: Latissimus dorsi Pectoralis major Coracobrachialis Teres major Teres minor Infraspinatus Extension: Latissimus dorsi Deltoid (posterior) Teres major Triceps brachii (long) Medial Rotation: Subscapularis Pectoralis Major Latissimus dorsi Teres major Deltoid (anterior)

63 Muscles that Move the Forearm
3 Flexors of the elbow joint: all insert either onto the radius or the ulna 1. biceps brachii – “two heads” of humerus long & short heads flexes elbow & supinates forearm origin: short head - corocoid process of scapula; long head – scapula (above glenoid cavity) insertion: radial tuberosity of radius 2. brachioradialis origin: humerus insertion: radius (styloid process) 3. brachialis major flexor of the elbow joint insertion: coronoid process of ulna

64 Muscles that Move the Forearm
4 Extensors of the elbow joint: different origins – all insert onto the olecranon process 1. triceps brachii – “three heads” of humerus long, medial & lateral heads extends elbow origin: short & medial heads – back of humerus; long head – scapula (below glenoid cavity) insertion: olecranon process 2. anconeus 4th extensor of the elbow joint origin: lateral epicondyle of humerus

65 Muscle that Pronate & Flex
Pronator teres medial epicondyle to radius so contraction turns palm of hand down towards floor Flexor carpi muscles radialis ulnaris Flexor digitorum muscles superficialis profundus Flexor pollicis longus brevis

66 Muscles that Supinate & Extend
Supinator lateral epicondyle of humerus to radius supinates hand Extensors of wrist and fingers extensor carpi extensor digitorum extensor pollicis extensor indicis

67 Intrinsic Muscles, Tendons and Ligaments of the Hand

68 Retinaculum Tough connective tissue band that helps hold tendons in place Flexor retinaculum runs from pisiform/hamate to scaphoid/trapezium overlies 10 tendons + median nerve flexor carpi radialis, pollicis longus, digitorum superioficialis & digitorum profundus carpal tunnel syndrome = painful compression of median nerve due to narrowing passageway under flexor retinaculum

69 Muscles of the pelvic girdle and lower limbs
Three groups Muscles that move the thighs Muscles that move the leg Muscles that move the foot and toes

70 Muscles that Move the Thigh at the Hip Joint
muscles that move the thigh can perform multiple movements e.g. sartorius – “tailor muscle” hip flexion lateral rotation of femur flexion of knee medial rotation of leg these muscles span the hip joint hip joint – another ball-in-socket joint capable of multiple planes of motion movements at the hip joint abduction adduction flexion extension medial rotation lateral rotation circumduction

71 Muscles that Move the Thigh at the Hip Joint
can categorize the muscles of the thigh & their movements this way Medial compartment – hip adductors Lateral compartment – hip abductors Anterior compartment – hip flexors (knee extensors) Posterior compartment – hip extensors & knee flexors Gluteal region – hip extensors and abductors Deep Gluteal region – lateral rotators

72 Muscles that Flex the Thigh
9 Hip flexors: these muscles also either adduct or abduct the thigh iliopsoas – made up two muscles: iliacus & psoas major major hip flexors origin – lumbar vertebrae and iliac fossa insertion – lesser trochanter of femur sartorius - longest muscle origin – anterior superior iliac spine insertion - tibia tensor fascia latae – also abducts the thigh by pulling on its tendon; medially rotates origin – iliac crest insertion – tibia by way of the iliotibial tract or IT band rectus femoris – part of the quadriceps 3 adductors + pectineus

73 Muscles that Extend the Thigh
5 Hip extensors: originate from pelvis & sacrum and insert into the femur, tibia and fibula some also laterally rotate the thigh 3 Hamstrings – also flexors of the knee hamstring part (lowest part) of adductor magnus Gluteus maximus major hip extensor extension and lateral rotation of hip pulls on iliotibial tract origin – iliac crest, sacrum and coccyx insertion – gluteal tuberosity on femur

74 Muscles that Adduct the Thigh
5 adductors - adducts hip originate from pubis and insert onto the linea aspera of femur Adductor magnus biggest of the adductors divided into an adductor part and a hamstring part hamstring part also extends the hip adductor part also flexes the hip Adductor brevis Adductor longus Pectineus pectineus, adductor longus and brevis are also hip flexors Gracilis also flexes the knee

75 Muscles that Abduct the Thigh
4 Hip Abductors: originate from pelvis and insert onto the greater trochanter of femur Gluteus Medius origin – iliac crest Gluteus Minimus origin - anterior gluteal line Sartorius Tensor fascia latae

76 Muscles that Rotate the Thigh
9 lateral rotators of the thigh: most insert onto the greater trochanter Piriformis Obturator internus Obturator externus Superior gemellar Inferior gemellar Quadratus femoris Gluteus maximus (medius and minimus) Adductor magnus Sartorius 3 medial rotators: Gluteus medius and minimus –when hip is extended Adductor brevis TFL

77 Summary: Muscle Actions at the Hip Joint
Abduction: Gluteus medius Gluteus minimus Tensor fascia latae Sartorius Flexion: Iliopsoas 3 adductors Pectineus Sartorius Rectus femoris Gracilis Lateral Rotation: Adductor magnus (hamstring) Gluteus maximus Sartorius 2 Obturators 2 Gemellars Quadratus femoris Piriformis prime movers in bold Adduction: Adductor longus Adductor brevis Adductor magnus Pectineus Extension: Gluteus maximus Adductor magnus (ham.) Biceps femoris (long head) Semimembranosus Semitendinosus Medial Rotation: Gluteus medius Gluteus minimus Adductor brevis Tensor fascia latae

78 Muscles that Extend the Leg
4 Extensor muscles of the leg or Quadriceps femoris – “four heads” of the femur for leg extension at the knee joint found on the anterior and lateral surfaces of the thigh originate from the pelvis (rectus femoris) and femur ( 3 vastus muscles) all insert onto the tibial tuberosity on the tibia via the patellar ligament Rectus femoris – because of its origin on the anterior inferior iliac spine – also a hip flexor Vastus lateralis Vastus medialis Vastus intermedius

79 Muscles that Flex the Leg
11 Flexors of the leg for flexion of the knee joint some also extend the hip (hamstrings) found in the posterior compartment of the thigh originate from the pelvis and insert onto the tibia and fibula 3 Hamstrings: all originate on the ischial tuberosity Biceps femoris – 2 heads Semimembranosus Semitendinosus common insertion with semimembranosus onto tibia 3 Adductor muscles Sartorius Gracilis

80 Muscles that Flex the Leg
11 Flexors of the knee Gastrocnemius gastroc = belly kneme = leg also plantar flexes foot with soleus origin – femoral condyles insertion – calcaneus via the Achilles tendon Popliteal muscle poplit = back of knee Unlocks knee joint origin – lateral condyle of femur insertion - tibia Plantaris weak knee flexor

81 Muscles that Plantar Flex the Foot
Gastrocnemius, soleus and plantaris are also plantarflexors of the foot Tibialis posterior also inverts the foot (turn in) Fibularis/Peroneus longus and brevis also evert the foot (turn out) Flexor digitorum and hallicis longus also curl the toes

82 Muscles that Dorsiflex the Foot
4 muscles are responsible for dorsiflexion of foot (toes up) Tibialis anterior also inverts the foot Fibularis/Peroneus tertius everts the foot with the other 2 fibularis muscles Extensor digitorum and hallicis longus


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