BMSP 2135 Chapter 10
BMSP 2135 Chapter 10 2135 BMSP
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This 40 page Class Notes was uploaded by Marlena Trone on Tuesday October 11, 2016. The Class Notes belongs to 2135 BMSP at Virginia Polytechnic Institute and State University taught by in Fall 2016. Since its upload, it has received 5 views.
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Date Created: 10/11/16
CHAPTER 10: The Muscular System ORGANIZATION OF MUSCLES • about 600 human skeletal muscles • constitute about half of our body weight • three kinds of muscle tissue – skeletal, cardiac, smooth • specialized for one major purpose – converting the chemical energy in ATP into the mechanical energy of motion • myology: the study of the muscular system THE FUNCTIONS OF MUSCLES • Movement – move from place to place, movement of body parts and body contents in breathing, circulation, feeding and digestion, defecation, urination, and childbirth – role in communication – speech, writing, and nonverbal communications • Stability – maintain posture by preventing unwanted movements – antigravity muscles – resist the pull of gravity and prevent us from falling or slumping over – stabilize joints • Control of openings and passageways – sphincters – internal muscular rings that control the movement of food, bile, blood, and other materials • Heat production by skeletal muscles – as much as 85% of our body heat CONNECTIVE TISSUES OF A MUSCLE • Endomysium: thin sleeve of loose connective tissue (CT) surrounding each muscle fiber (muscle cell) allows capillaries and nerve fibers to reach each muscle fiber. • Perimysium: slightly thicker layer of CT surrounding each fascicle (bundles of muscle fibers) carry larger nerves and blood vessels, and stretch receptors • Epimysium: fibrous sheath surrounding the entire muscle – Outer surface grades into the fascia – Inner surface sends projections between fascicles to form perimysium • Fascia: sheet of connective tissue that separates neighboring muscles or muscle groups from each other and the subcutaneous tissue. FASCICLE ORIENTATION OF MUSCLES • Strength of a muscle and the direction of its pull are determined partly by the orientation of its fascicles CLASSIFICATION OF MUSCLES ACCORDING TO FASICLE ORIENTATION • fusiform muscles – thick in middle and tapered at ends – biceps brachii , gastrocnemius • parallel muscles – have uniform width and parallel fascicles – can span longer distances and shorten more than other shapes but produce less force than fusiform – rectus abdominis, zygomaticus major • triangular (convergent) muscles – fanshaped, broad at origin and tapering to a narrower insertion – powerful muscles due to large number of fibers in the wide region – pectoralis major, temporalis • pennate muscles – fascicles insert obliquely on a tendon (feather shaped) – unipennate, bipennate or multipennate – palmar interosseus, rectus femoris and deltoid – most powerful due to large number of fibers per length • circular muscles (sphincters) – ring around body opening – orbicularis oculi, urethral and anal sphincters MUSCLE ATTACHMENTS • indirect attachment to bone – tendons bridge the gap between muscle ends and bony attachment • the collagen fibers of the endo, peri, and epimysium continue into the tendon • from there into the periosteum and the matrix of bone – very strong structural continuity from muscle to bone • aponeurosis – tendon is a broad, flat sheet (palmar aponeurosis) • retinaculum – connective tissue band that tendons from separate muscles pass under • direct (fleshy) attachment to bone – little separation between muscle and bone – muscle seems to immerge directly from bone – margins of brachialis, lateral head of triceps brachii • some skeletal muscles do not insert on bone, but in dermis of the skin – muscles of facial expression MUSCLE ORIGINS AND INSERTIONS • Origin – bony attachment at stationary end of muscle • Belly – thicker, middle region of muscle between origin and insertion • Insertion – bony attachment to mobile end of muscle FUNCTIONAL GROUPS OF MUSCLES • action: the effects produced by a muscle – to produce or prevent movement • prime mover (agonist): muscle that produces most of force during a joint action • synergist: muscle that aids the prime mover – stabilizes the nearby joint – modifies the direction of movement • antagonist: opposes the prime mover – relaxes to give prime mover control over an action – preventing excessive movement and injury – antagonistic pairs: muscles that act on opposite sides of a joint • fixator muscle that prevents movement of bone MUSCLE ACTIONS ACROSS ELBOW Flexion: • prime mover = brachialis • synergist = biceps brachii • antagonist = triceps brachii – Contraction of this muscle leads to extension, the opposite motion • fixator muscle that holds scapula firmly in place – rhomboids INTRINSIC AND EXTRINSIC MUSCLES • intrinsic muscles – entirely contained within a region, such as the hand – both its origin and insertion in the hand • extrinsic muscles – act on a designated region, but has its origin elsewhere – Ex. origin in forearm, insertion in the hand • The flexor pollicis longus is a muscle with its origin in the forearm that acts on the hand, thus it is an extrinsic muscle • The abductor pollicis brevis is a muscle located in the hand that acts on the hand, thus it is an intrinsic muscle. • The tongue is essentially a muscle. There are intrinsic muscles of the tongue that make up much of the tongue tissue. There are also extrinsic muscles with origins on the hyoid, for example, that act on the tongue (ex. Hyoglossus) MUSCLE INNERVATION • innervation of a muscle – refers to the identity of the nerve that stimulates it – enables the diagnosis of nerve, spinal cord, and brainstem injuries from their effects on muscle function • spinal nerves arise from the spinal cord – emerge through intervertebral foramina – innervate muscles below the neck – plexus – weblike network of spinal nerves adjacent to the vertebral column • cranial nerves arise from the base of the brain – emerge through skull foramina – innervate the muscles of the head and neck – numbered I to XII THE MUSCULAR SYSTEM MUSCLES OF FACIAL EXPRESSION • muscles that insert in the dermis and subcutaneous tissues • tense the skin and produce facial expressions • innervated by facial nerve (CN VII) • paralysis causes face to sag • found in scalp, forehead, around the eyes, nose and mouth, and in the neck MUSCLES OF CHEWING AND SWALLOWING • extrinsic muscles of the tongue – tongue is very agile organ – pushes food between molars for chewing (mastication) – forces food into the pharynx for swallowing (deglutition) – crucial importance to speech • intrinsic muscles of tongue – vertical, transverse, and longitudinal fascicles MUSCLES OF CHEWING • four pairs of muscles produce the biting and chewing movements of the mandible – depression – to open mouth – elevation – biting and grinding – protraction – incisors can cut – retraction – make rear teeth meet – lateral and medial excursion – grind food – temporalis, masseter, medial pterygoid, lateral pterygoid • innervated by mandibular nerve which is a branch of the trigeminal (V) HYOID MUSCLES Suprahyoid Group: • aspects of chewing, swallowing, and vocalizing • eight pairs of hyoid muscles associated with hyoid bone • digastric opens mouth widely • geniohyoid – depresses mandible • mylohyoid – elevates floor of mouth at beginning of swallowing • stylohyoid – elevates hyoid Infrahyoid Group: • fix hyoid bone from below…allowing suprahyoid muscles to open mouth • omohyoid – depresses hyoid after elevation • sternohyoid – depresses hyoid after elevation • thyrohyoid – depresses hyoid and elevates larynx • sternothyroid – depresses larynx after elevation MUSCLES OF PHARYNX • three pairs pharyngeal constrictors – encircle pharynx forming a muscular funnel – during swallowing drive food into the esophagus MUSCLES ACTING ON THE HEAD • originate on the vertebral column, thoracic cage, and pectoral girdle • insert on the cranial bones • actions – flexion (tipping head forward) – extension (holding the head erect) – lateral flexion (tipping head to one side) – rotation (turning the head to the left and right) • some muscles cause contralateral movement – movement of the head toward the opposite side (contraction of a muscle on the left turns the head right) • some muscles cause ipsilateral movement – movement of the head toward the same side • neck flexors – sternocleidomastoid, scalenes • neck extensors – trapezius, splenius capitis, semispinalis capitis MUSCLES OF THE TRUNK • three functional groups – muscles of respiration – muscles that support abdominal wall and pelvic floor – movement of vertebral column MUSCLES OF RESPIRATION • breathing requires the use of muscles enclosing thoracic cavity – diaphragm, external intercostal, internal intercostal, and innermost intercostal muscles • inspiration – air intake • expiration – expelling air • other muscles of chest and abdomen that contribute to breathing – sternocleidomastoid, scalenes of neck – pectoralis major and serratus anterior of chest – latissimus dorsi of back – abdominal muscles – internal and external obliques, and transverse abdominis – some anal muscles DIAPHRAGM • Muscular dome between thoracic and abdominal cavities • Muscle fascicles extend to a fibrous central tendon • Contraction flattens the diaphragm – Enlarges thoracic cavity (inspiration breathing in) • In relaxation of diaphragm it rises – Shrinks the thoracic cavity (expiration breathing out) INTERCOSTALS • external intercostals – elevates ribs – expand thoracic cavity – create partial vacuum causing inflow of air • internal intercostals – depresses and retracts ribs – compresses thoracic cavity – expelling air • innermost intercostals – same action as internal intercostals MUSCLES OF THE ANTERIOR ABDOMINAL WALL • four pairs of sheetlike muscles – external abdominal oblique – internal abdominal oblique – transverse abdominal – rectus abdominis • strengthen abdominal wall EXTERNAL ABDOMINAL OBLIQUE • most superficial of lateral abdominal muscles • supports abdominal viscera against pull of gravity • stabilizes vertebral column during heavy lifting • maintains posture • compresses abdominal organs • aids in forced expiration • rotation at waist INTERNAL ABDOMINAL OBLIQUE • intermediate layer of lateral abdominal muscles • unilateral contraction causes ipsilateral rotation of waist • aponeurosis – tendons of oblique and transverse muscles –broad, fibrous sheets TRANSVERSE ABDOMINAL • deepest of lateral abdominal muscles • horizontal fibers • compresses abdominal contents • contributes to movements of vertebral column RECTUS ABDOMINIS • flexes lumbar region of vertebral column • produces forward bending at the waist • extends from sternum to pubis • rectus sheath encloses muscle • three transverse tendinous intersections divide rectus abdominis into segments – “six pack” SUPERFICIAL MUSCLES OF BACK • Extend, rotate and laterally flex vertebral column • Upper limb movement MUSCLES ACTING ON THE SHOULDER AND UPPER LIMB • compartments – spaces in which muscles are organized and are separated by fibrous connective tissue sheets (fasciae) – each compartment contains one or more functionally related muscles along with their nerve and blood supplies • muscles of upper limbs divided into anterior and posterior compartments • muscles of lower limbs divided into anterior, posterior, medial, and lateral compartments • intermuscular septa (thick fascia) separates compartments • compartment syndrome – one of the muscles or blood vessels in a compartment is injured MUSCLES ACTING ON THE SHOULDER • originate on the axial skeleton • insert on clavicle and scapula • scapula loosely attached to thoracic cage – capable of great movement – rotation, elevation, depression, protraction, retraction – clavicle braces the shoulder and moderates movements ANTERIOR GROUP OF MUSCLES OF PECTORAL GIRDLE • pectoralis minor – ribs 35 to coracoid process of scapula – draws scapula laterally • serratus anterior – ribs 19 to medial border of scapula – abducts and rotates or depresses scapula POSTERIOR GROUP OF MUSCLES OF PECTORAL GIRDLE • four muscles of posterior group – trapezius superficial – levator scapulae, rhomboideus minor, and rhomboideus major deep • trapezius – stabilizes scapula and shoulder – elevates and depresses shoulder apex • levator scapulae – elevates scapula – flexes neck laterally • rhomboideus minor – retracts scapula and braces shoulder • rhomboideus major – same as rhomboideus minor MUSCLES ACTING ON THE ARM • nine muscles cross the shoulder joint and insert on humerus • two are axial muscles because they originate on axial skeleton – pectoralis major – flexes, adducts, and medially rotates humerus – latissimus dorsi – adducts and medially rotated humerus • seven scapular muscles • originate on scapula – deltoid • rotates and abducts arm • intramuscular injection site – teres major • extension and medial rotation of humerus – coracobrachialis • flexes and medially rotates arm – remaining four form the rotator cuff that reinforce the shoulder joint ROTATOR CUFF MUSCLES • tendons of the remaining four scapular muscles form the rotator cuff • “SITS” muscles – for the first letter of their names – supraspinatus – infraspinatus – teres minor – subscapularis • tendons of these muscles merge with the joint capsule of the shoulder as they cross it in route to the humerus • holds head of humerus into glenoid cavity • supraspinatus tendon most easily damaged MUSCLES ACTING ON FOREARM • elbow and forearm capable of flexion, extension, pronation, and supination – carried out by muscles in both brachium (arm) and antebrachium (forearm) • muscles with bellies in the arm (brachium) – principal elbow flexors – anterior compartment • brachialis and biceps brachii – brachialis produces 50% more power than biceps brachii – brachialis is prime mover of elbow flexion – principal elbow extensor – posterior compartment • triceps brachii – prime mover of elbow extension • principal flexor – brachialis • synergistic flexors – biceps brachii – brachioradialis • principal extensor – triceps brachii • muscles with bellies in the forearm (antebrachium) • most forearm muscles act on the hand and wrist – brachioradialis – flexes elbow – anconeus – extends elbow – pronator quadratus – prime mover in forearm pronation – pronator teres – assists pronator quadratus in pronation – supinator – supinates the forearm SUPINATION AND PRONATION Supination • supinator muscle • palm facing anteriorly or superiorly Pronation • pronator quadratus and pronator teres • palm faces posteriorly or inferiorly ANTERIOR MUSCLES ACTING ON WRIST AND HAND • extrinsic muscles of the forearm • intrinsic muscles in the hand itself • extrinsic muscle actions – flexion and extension of wrist and digits – radial and ulnar flexion – finger abduction and adduction – thumb opposition POSTERIOR MUSCLES ACTING ON WRIST AND HAND • extension of wrist and fingers, adduct / abduct wrist • extension and abduction of thumb (pollicis) • brevis short, ulnaris on ulna side of forearm CARPAL TUNNEL SYNDROME • flexor retinaculum: braceletlike fibrous sheet that the flexor tendons of the extrinsic muscles that flex the wrist pass on their way to their insertions • carpal tunnel: tight space between the flexor retinaculum and the carpal bones – flexor tendons passing through the tunnel are enclosed in tendon sheaths • carpal tunnel syndrome: prolonged, repetitive motions of wrist and fingers can cause tissues in the carpal tunnel to become inflamed, swollen, or fibrotic – puts pressure on the median nerve of the wrist that passes through the carpal tunnel along with the flexor tendons – tingling and muscular weakness in the palm and medial side of the hand – pain may radiate to arm and shoulder – treatment – antiinflammatory drugs, immobilization of the wrist, and sometimes surgery to remove part or all of flexor retinaculum • Repetitive motions cause inflammation and pressure on median nerve INTRINSIC HAND MUSCLES • Thenar group: form thick, fleshy mass at base of thumb – adductor pollicis – abductor pollicis brevis – flexor pollicis brevis – opponens pollicis • Hypothenar group: fleshy base of the little finger – abductor digiti minimi – flexor digiti minimi brevis – opponens digiti minimi • Midpalmar group: hollow of palm – dorsal interosseous muscles (4) – palmar interosseous muscles (3) – lumbricals (4 muscles) MUSCLES ACTING ON THE HIP AND LOWER LIMB • largest muscles found in lower limb • less for precision, more for strength needed to stand, maintain balance, walk, and run • several cross and act on two or more joints • leg: the part of the limb between the knee and ankle • foot: includes tarsal region (ankle), metatarsal region, and the toes Muscles Acting on the Hip and Femur • anterior muscles of the hip – iliacus • flexes thigh at hip • iliacus portion arises from iliac crest and fossa – psoas major • flexes thigh at hip • arises from lumbar vertebrae – they share a common tendon on the femur and are collectively known as the iliopsoas Posterior Muscles Acting on Hip and Femur • lateral and posterior muscles of the hip – tensor fasciae latae • extends knee, laterally rotates knee – gluteus maximus • forms mass of the buttock • prime hip extensor • provides most of lift when you climb stairs – gluteus medius and minimus • abduct and medially rotate thigh • lateral rotators six muscles inferior to gluteus minimus • deep to the two other gluteal muscles – gemellus superior – gemellus inferior – obturator externus – obturator internus – piriformis – quadratus femoris • medial (adductor) compartment of thigh • five muscles act as primary adductors of the thigh – adductor brevis – adductor longus – adductor magnus – gracilis – pectineus Muscles Acting on the Knee and Leg • anterior (extensor) compartment of the thigh – contains large quadriceps femoris muscle • prime mover of knee extension • most powerful muscle in the body • has four heads – rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius – all converge on single quadriceps (patellar) tendon – extends to patella – then continues as patellar ligament – inserts on tibial tuberosity – sartorius – longest muscle in the body • posterior (flexor) compartment of the thigh – contains hamstring muscles: biceps femoris semitendinosus semimembranosus MUSCLES OF THE LEG • crural muscles, acting on the foot, are separated into 3 compartments. – anterior compartment (red) – fibular (lateral) compartment (green) – posterior (superficial = pink) (deep = purple) Anterior Compartment of Leg • anterior (extensor) compartment of the leg – dorsiflex the ankle – prevent toes from scuffing when walking – fibularis (peroneus) tertius – extensor digitorum longus – extensor hallucis longus – tibialis anterior Posterior Compartment of Leg Superficial Group • three muscles of the superficial group – gastrocnemius plantar flexes foot, flexes knee – soleus – plantar flexes foot – plantaris weak synergist of triceps surae • triceps surae – collective name for gastrocnemius and soleus – inserts on calcaneus by way of the calcaneal (Achilles) tendon – strongest tendon in the body Posterior Compartment of Leg Deep Group • four muscles in the deep group – flexor digitorum longus – flexes phalanges – flexor hallucis longus – flexes great toe – tibialis posterior – inverts foot – popliteus – acts on knee Lateral (Fibular) Compartment of the Leg • two muscles in this compartment – fibularis longus – fibularis brevis – both plantar flex and evert the foot • provides lift and forward thrust Intrinsic Muscles of Foot • four ventral muscle layers • support for arches – abduct and adduct the toes – flex the toes – one dorsal muscle – extensor digitorum brevis extends toes ATHLETIC INJURIES • muscles and tendons are vulnerable to sudden and intense stress • proper conditioning and warmup needed • common injuries; – compartment syndrome – shinsplints – pulled hamstrings – tennis elbow – pulled groin – rotator cuff injury – treat with rest, ice, compression and elevation (RICE) • “no pain, no gain” is a dangerous misconception
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