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Lecture

Back and Limbs Notes Outline

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Biology
Course
BIOL 1300
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All Professors
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Fall

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BACK AND LIMBS - OUTLINES INTRODUCTION TO ANATOMICAL TERMS I. ANATOMIC POSITION a. All terms are in reference to this position b. Standing/lying supine with palms and feet forward II. ANATOMIC PLANES a. Median (Midsaggital) – divides into left and right halves b. Saggital – parallel to the median (infinite number) c. Frontal (coronal) – divides into front and back halves d. Transverse (horizontal) – divides into top, bottom (infinite number)  Radiology slides: able to see fracture, screws accurately from saggital cross- section but not frontal III. TERMS OF RELATIONSHIP a. Superior (rostral, cephalic) /Inferior (caudal) b. Anterior/Posterior c. Medial/Lateral d. Proximal/Distal e. Extrinsic/Intrinsic f. Valgus/Varus – bone distal to the joint deviates away from /towards the midline  1) pick joint 2)look at bone distal to joint 3) look at long axis: towards or away? g. Superficial/Deep h. Bilateral/Unilateral i. Ipsilateral/Contralateral – same/opposite side as  Weak hip on one side  leg contralateral will sag… j. Palmar/Dorsal (hands); Plantar/Dorsal (feet) IV. TERMS OF MOVEMENT a. Flexion/Extension – occurs in saggital plane (bending/straightening)  Description of action includes name of body segment/joint/bone (not only motion, but where motion takes place)  Ex: “deltoid produces flexion of the arm/shoulder/humerus” b. Abduction/Adduction – occurs in frontal (coronal) plane (away from/towards body) c. Medial (internal)/Lateral (external) rotation – movement of ventral surface towards/away from median d. Elevation/Depression e. Protraction/Retraction – movement anteriorly/towards median f. Joint-Specfic:  Protrusion/retrusion – movement of jaw(TMJ) forward/back  Supination/pronation – palms up/down  Opposition/reposition – thumb touches digits  Dorsiflexion/plantar flexion – foot toward dorsal/plantar position  Inversion/eversion – plantar side of foot faces median/away V. OTHER MUSCULOSKELETAL TERMS a. Ligaments – band or sheets of fibrous connective tissue that connects 2 or more bones or structures b. Tendons – connect muscle to bone c. Fascia – sheet of fibrous connective tissue that envelop muscles and separates different layers or groups of structures d. Two sites of muscle attachment:  Origin: proximal attachment Don’t have to know which site is which – only have to  Insertion: distal attachment know that there are two points of attachment OVERVIEW OF THE SKELETAL SYSTEM I. CLASSIFICATION OF BONES a. Overview i. Comprised of 206 bones – classified by location, shape, or structure ii. Articulation – point where 2 or more bones come together (movement) b. Location i. Axial – bones of head, back, chest ii. Appendicular – upper and lower extremities, pelvic girdle (not axial because function has to do with lower extremities) iii. Sesamoid – bone embedded within tendon, typically where tendon passes over joint  increases mechanical efficiency of tendon (change angle – more power) c. Shape i. Long/short, flat, irregular (vertebra) ii. Important for embryology – develop differently d. Structure i. Spongy (trabecular) – not completely random – organized based on load, stress ii. Compact e. Osteology (self study) i. bone markings, formations  reveals function of structures around it ii. landmarks can be related to passage of nerves or vessels, muscle attachment II. CLASSIFICATION OF JOINTS a. Overview i. Joints structured in specific way  allows specific type of motion ii. Classified according to what is between them: Least mobile 1. Fibrous – fibrous tissue between  2. Cartilaginous or fibrocartilaginous  3. Synovial – synovial fluid Most mobile b. Fibrous Joints i. Suture – interlocking (ex: skull) ii. Syndesmosis – sheet of connective tissue between bones (ex: radius and ulna) iii. Gomphosis – peglike articulation – only teeth c. Cartilaginous Joints i. Synchondrosis (primary CJ) – 2 distinct regions of bone joined by growth plate(complete ossified in mature skeleton  no synchondrosis) ii. Symphysis (secondary) – fibrocartilaginous disc remains between bones (ex: two pelvic bones) d. Synovial Joints i. Structure: 1. capsule surrounding two bones, enclosing joint cavity 2. Cavity lined with synovial membrane – produces fluid, lubricates joint 3. Articulating ends of bones are covered in hyaline cartilage 4. Potential for increase in friction between joints and surrounded structures  bursa = connective tissue sac associated with joints which facilitate movement by reducing friction (“thin cushion”) glides ii. Types: based on how many axes of movement (# planes), shape of articulating surface 1. Plane – 2 flat surfaces, bones glide against each other 2. Uniaxial – movement around single axis (within single plane) a. Hinge (knee) b. Pivot (elbow) 3. Biaxial – two axes (fingers – move in saggital and frontal planes) a. Condyloid (fingers) b. Saddle (base of thumb) 4. Triaxial – three plans a. Ball and socket (shoulder – flex/ext, AB/AD, rotation) III. INNERVATION AND BLOOD SUPPLY TO JOINTS a. Periarticular arterial anastomosis around each joint – vessels approach joint from all directions (so if finger bent, doesn’t cut off blood supply) b. Mechanoreceptors – for proprioception – send information about position of joint back to CNS  when to stop extending c. Hilton’s Law – nerve supply to a joint is by the same nerves that innervate muscles IV. CLINICAL CORRELATE: ARTHRITIS a. Rheumatoid Arthritis i. Autoimmune disease – inflammatory (body attacks joints) ii. clinical presentation is bilateral – affects both extremities equally b. Osteoarthritis i. Mechanical breakdown – caused by overuse, imbalance related to activity ii.  may be unilateral *correctly describing movements that occur allows us to measure and analyze movement and related pathology. BACK, VERTEBRAL COLUMN & SPINAL CORD I. VERTEBRAL COLUMN a. Components i. Vertebra 1. 26 total: 7 cervical, 12 thoracic, 5 lumbar, 1 sacrum (5 at birth fuse), 1 coccyx (4 at birth) ii. Associated Discs iii. Associated ligaments b. Curvatures i. Normal (Netter 153) 1. Primary – all regions have forward flexion a. Thoracic b. sacral 2. Secondary – some forward curvatures reverse through development: a. Cervical – crawling  holding head up b. Lumbar – walking (end of 1y)  have to shift weight ii. Abnormal 1. Kyphosis – excessive forward flexion of thoracic spine (saggital plane) 2. Lordosis – excessive lumbar curvature – can occur temporarily during pregnancy; called Lordosis if chronic (saggital plane) 3. Scoliosis – abnormal lateral curvature (frontal plane) c. Joints of the vertebral column i. Movements: 1. Flexion/extension 2. Lateral flexion – can’t really use ad-, abduction, because both are away from spine (spine is in middle) 3. Rotation ii. Joints 1. Zygaphophyseal (facet a. posterior, b. between interlocking articular processes of stacked vertebra c. synovial plane joints  fair amount of motion d. interlocking  prevents fw and bk shifting e. are not weight-bearing – meant to glide 2. Intervertebral (symphysis) a. anterior, between big wide vertebral bodies b. thick, fibral, cartilaginous discs – meant to transmit weight and force (a little motion but not primary function) c. structure: i. nucleous pulposis (inner) - gelatinous ii. annulus fibrosis – concentric rings of conn tissue 3. Ligaments – support joints, guard excess movement a. Anterior and posterior longitudinal ligaments – prevent extension too far forward/back b. Interspinous and supraspinous ligaments - between spine of vertebra/ on external surface of vertebra c. Ligamentum flavum – lining vertebral canal – protects the spinal cord within spinal canal iii. Clinical correlation: herniated disc 1. Usually between two lumbar vertebra (L4-L5) or L5-S10 2. Due to uneven force on intervertebral disc (disc degeneration, weight, posture, improper lifting) 3. Different degrees of damage: disc degeneration, prolapse, extrusion 4. Laminectomy: a. remove portion of lamina to access damaged disc, pull out b. Heals with connective tissue, but may need bone graft *Keep alignment on spine when lifting so intervert discs bear weight II. SPINAL CORD AND MENINGES a. Spinal Cord i. Stacked vertebral  central canal, contains SC ii. 31 segments: 8 cerv, 12 thor, 5 lumb, 5 sacr, 1 coccygeal iii. No uniform diameter – enlarged in cervical and lumbar regions – necessary to innervate upper and lower extremities iv. Terminal end = conus medullaris, ends at L1,-L2 (before vertebral column ends) b. Meninges – 3 layers of connective tissue that protect i. Dura mater (outer) 1. Forms spinal dural sac – tubular sheath within vert canal ii. Arachnoid mater 1. Subarachnoid space (below arachnoid) – has cerebrospinal fluid – helps bathe and nourish, give buoyancy to spinal cord iii. Pia mater (innermost) 1. Lateral projections = denticulate ligaments – help stabilize spinal cord laterally 2. Filum terminale – extension of pia mater within dural sac; dural sac closes off and is joined by layer of dura  3. Filum terminale externa – part that attaches to coccyx, stabilizes spinal cord vertically *cauda equina III. SEGMENTAL NERVES AND VESSELS a. Vessels i. Arteries 1. vertebral arteries unite  1 anterior spinal artery nourish anterior 2/3 (both sides) 2. 2 posterior arteries (smaller) – only supply posterior 1/3 3. Reinforced by radicular (radiating) arteries a. Great radicular artery – v big one ii. Veins 1. Complex, so referred to as 4 vertebral plexuses: anterior external, ant int, post, ext, post int 2. Communicate with venous sinuses in cranial cavity (base of skull) b. Nerves i. 31 pairs: 8 cerv, 12 thor, 5 lumb, 5 sacr, 1 coccygeal ii. Formation: 1. posterior roots coming off spinal cord  sensory; anterior roots  motor  form mixed spinal nerve (both sensory and motor) 2. each spinal nerve  rami: a. dorsal ramus – muscles and skin of back b. ventral ramus – thoracic wall, extremities iii. intervertebral foramen: spinal nerves exit laterally via these holes; foramen formed by vertebral arch and zygapophyseal joint iv. only 7 cervical vertebra, but 8 spinal nerves  nerve C7 comes out foramen above C7, and C8 comes out below (btw C7 and T1) v. spinal cord ends at lumbar region  last nerves have to go all the way down column before exiting  cauda equina (horse’s tail) – bundle of spinal nerve roots below L1; part of PNS 1. Clinical applicaton: spinal taps – want to puncture here instead of spinal cord, so if you inject too far not as much damage 2. Spina bifida – deformity in which there is failure of fusion of vertebra  SC protrudes into space a. Asymptomatic (spina bifida oculta) b. SB Cystica – fluid-filled cyst protrudes c. Meningocele – only meninges protrude d. Myelomeningocele – spinal cord and cauda equine protrude e. Level of lesion  level of impairment c. Myotomes and Dermatomes i. Myotome – all the muscles that are innervated by a single spinal cord segment (“the myotome of that level”) ii. Dermatome – area of skin innervated – not motor, but sensory iii. Used clinically to determine area of injury – “can you feel this?” keep going until sensation cut off; test which muscle functions are impaired (ie flexion but no extension) IV. MUSCLES a. Superficial Layer – trapezius, latissimus dorsi, levator scapulae, rhomboid major, minor a. Intermediate Layer – serratus posterior inferior and superior b. Deeper Layers – erector spinae, splenius capitus &cervicis, semispinalis capitis INTRO TO THE NERVOUS SYSTEM I. THE NEURON a. General structures i. Nervous system – composed of cells with long processes ii. Nerve fibers = bundles of cells iii. Branch points = cells leaving bundle (if you sever the nerves after branching, you avoid severing entire bundle) b. Structure of neuron i. Soma (cell body) – contains nucleus, other cell components ii. Axon – nearly uniform diameter 1. Axon hillock – sums up all inputs, generals and action potential iii. Terminal arborization (terminal branches) – end of axon iv. Dendrites/dendritic process – branched extensions of cell body c. Shapes i. Multipolar ii. Bipolar – axon and dendrites arise from single, common dendritic process iii. (pseudo)unipolar – single neuronal process divides into two axonal processes (no dendrites) d. Signalling i. Presynaptic neuron 1. Axon hillock – summarizes inputs (stimulatory and inhibitory) 2. Action potential – wave of depolarization spreads along axon 3. Neurotransmitters – released at points of synapse with other neurons ii. Postsynaptic neuron 1. Receptor molecules – in membrane of post. neuron – produce local change in transmembrane electric potential  Beta blockers: block huge class of receptors 2. Electric potential different can be increased or decreased: hyperpolarization = inhibition; hypo = stimulation II. ORGANIZATION OF THE NERVOUS SYSTEM a. Anatomical subdivisions i. Central nervous system (CNS) – brain and spinal cord ii. Peripheral Nervous System (PNS) – everything else 1. Group of peripheral nerve cell bodies = ganglia 2. Any neuron whose soma is in PNS = ganglion cell iii. Many neurons lie in both (delineation is arbitrary) b. Organization of spinal cord i. 31 pairs ii. Body segments – correspond to spinal nerve iii. Extremities: plexus of fibers from several segments 1. Brachial plexus (C5-T1) 2. Lumbosacral plexus (L2-S3) III. FUNCTIONAL SUBDIVISIONS a. Afferent/Efferent i. Afferent (sensory) 1. Peripheral sensory ending and CNS connected by unipolar neuron  no synapse 2. Pass through spinal cord through dorsal root ii. Efferent (motor) 1. Interval between CNS and peripheral target (effector organ) bridged by 1-2 neurons  synapse 2. Pass out of spinal cord in ventral root b. Somatic/Visceral – division based on types of tissues, structures being innervated i. Somatic - what we are aware of and can control (voluntary) 1. sensory return from endings in skin, deeper musc. tissue 2. motor outflow to voluntary, striated muscles 3. direct, single-neuron pathway ii. Visceral (autonomic) 1. Sensory return from walls and lining of organs (viscera) - includes heart, very large blood vessels 2. Motor outflow to cardiac muscle, smooth muscle and glands 3. Indirect enervation: 2-neuron pathway: nerve cell body in CNS  motor ganglion cell in PNS a) Sympathetic system – axons enter/leave thoracic and lumbar regions of SC (T1-L2) b) Parasympathetic system – axons enter/leave brain stem, via cranial nerves, or sacral regions of SC (S2-4) c) Usually work together to control complex visceral functions IV. NEURAL MODALITIES (GENERAL) 4 types of traffic – 4 types of fiber = neuro modalities a. General Somatic Efferent (GSE) – outflow to voluntary striated muscle (single neuron); axons sent through ventral roots b. General Somatic Afferent (GSA) – inflow from sensory endings in non-visceral tissue (single neuron); axons sent through dorsal roots i. Exteroception – sensing outside world: temp, touch, pressure, pain (from skin, bone and muscle) ii. Proprioception – knowledge of self – where you are in space: position, movement (from muscles, joints, tendons- ex touching finger to nose) c. General Visceral Efferent (GVE) – outflow to cardiac muscle, involuntary smooth muscle, glands (two neurons) – ventral roots i. [Parasympathetic – none in back and limbs] ii. Sympathetic – 1. Preganglionic fibers from T1-L2 leave each nerve as bundle = white ramus communicans 2. sympathetic chain ganglia – parallel to vert column, contains motor ganglion cells that serve all body levels (output becomes diffuse) 3. Bundle of postganglionic axons = gray ramus – reach sweat glands, arrector pili muscles (raise hair follicles), invol smooth muscle of blood vessel walls  Only T1-L2 spinal nerves  serve all parts of body d. [General Visceral Afferent (GVA) – inflow from sensory endings in viscera, large blood vessels (single neuron) dorsal roots – not in back and limbs] Somatic - VOLUNTARY Visceral - AUTONOMIC Afferent sensing – proprioception, Sensory from viscera DORSAL exteroception No synapse No synapse (unipolar cell) Efferent Voluntary muscle Smooth and cardiac muscle, VENTRAL No synapse glands 2 neurons – preganglionic and postganglionic V. THE SPINAL NERVE a. Basic Structure i. Ventral root – axons of multipolar neurons (going outward to stri vol muscle) ii. Dorsal root- axon processes of unipolar neurons 1. Grow centrally into dorsal portion of cord 2. Grow peripherally out towards sensory endings (skin, deep musc tissue) iii. Trunk – where ventral and dorsal roots converge (both motor and sens fibers) iv. Primary rami – form when nerve divides into 2 bundles (each both motor and sensory) 1. DPR – dorsal primary ramus – turns dorsally  medial or lateral branches – supply deep muscle and skin of the back 2. VPR – ventral primary ramus (larger) – turns anteriorly  runs as intercostal nerve – supples vol stri muscle of thoracic wall 3. VPR also has nerve fibers destined for skin overlying intercostal space a) Lateral cutaneous branch (mid-axillary line) b) Anterior cutaneous branch (sternum) * Two different systems: one circumferential segmental system (spinal nerve), longitudinal system  joined by the rami communicans b. Addition of sympathetic motor outflow – postganglionic sympathetic GVE fibers are added to every spinal nerve (sweat glands, pili muscles, blood vessels all over body) i. Preganglionic axon in cord segment  VPR  white rami  sympathetic chain) synapse  post ganglionic axon  grey rami 1. Distributed in VPR  all cells 2. Turn back into DPR for distribution VI. CLINICAL CORRELATIONS a. if you sever a spinal cord segment, only a small portion is deinnervated because other nerves overlap b. Dermatomes and myotomes i. two basic concepts that allow us to locate injured segment ii. Dermatome – area of innervated skin; myotome – innervated muscle iii. Myotomes are more circumscribed; dermatomes spread out c. Fate of embryonic body segments in the trunk and limbs… d. Analysis of nerve injuries i. Damage to ventral root – monosegmental motor deficit ii. Damage to dorsal – monosegmental sensory deficit iii. Damage to trunk – monosegmental motor and sensory deficits iv. Damage along primary ramus – depends on axons present in nerve at site of injury: 1. Fibers beyond site of injury are compromised 2. Fibers that branched before site of injury (closer to CNS) are unaffected 3. Fibers that have joined nerve are compromised v. Injury to spinal cord 1. Segments above function normally 2. Segments below can function, but can’t communicate with brain (can’t use striated muscle at will, but it does respond to local sensory input) EMBRYOLOGY I. TERMS A. Human development i. Prenatal Period 1. (preembryonic period) – first 2 weeks 2. Embryonic period – through day 56 (8 weeks) 3. Fetal period – weeks 9-38 ii. Postnatal period – birth to adulthood B. Ways of counting age: i. Fertilization age – age counting from time of fertilization ii. Gestational age – from first day of last normal menstrual period (doctors use this - 2 weeks longer than fert. age) C. Miscellaneous i. Teratogens – environmental agents that cause congenital abnormalities 1. the embryonic period is a critical period of susceptibility to teratogens II. OVULATION AND FERTILIZATION A. Females i. In the embryo 1. Primordial germ cells form in yolk sac of female embryo 2. PGCs migrate into the developing ovary , differentiate into oogonia 3. Oogonia undergo mitosis  millions of oogonia 4. Oogonia differentiate into primary oocytes  now they can no longer undergo mitosis 5. primary oocytes are surrounded by follicular (connective tissue) cells primary follicle formed 6. first meiotic division begins, but halted in prophase I ii. Ovulation (puberty and every month following) 1. Follicle-stimulating hormone (FSH) stimulates a few oocytes (in primordial follicles) each month 2. Follicle maturation:  Follicle cells become cuboidal  now called granulosa cells, form zona pellucida -this is the primary follicle  Intercellular spaces fill with fluid = secondary follicle  oocyte pushed to the side, surrounded by corona radiate  granulose cells produce estrogen 3. Oocyte maturation:  High levels of estrogen  hormonal surge  Oocyte completes first meiotic division  secondary oocyte and polar body (lacks cytoplasm; will degenerate)  2ndary oocyte begins meiosis II, but is halted in metaphase 4. Ovulation:  Mature follicle forms bulge on ovary surface  Secondary oocyte, zp, and cr is expelled and swept up by distal end of oviduct  Remaining granulosa cells in ovary form corpus luteum – produces progesterone and estrogen  prepares uterus for implantation iii. Comception/Menstruation  implantation  conceptus produces hCG  CL remains  OR no implantation  CL degenerates  menstruation B. Males i. In the embryo 1. About 250 compartments within each testis, seminiferous tubules within each compartment 2. Only Sertoli cells and primordial germ cells in seminiferous tubules ii. Spermatogenesis 1. Testosterone (from Leydig cells in interstitial space) cells differentiate into spermatogonia  mitosis 2. Daughter cells differentiate into primary spermatocytes 3. spermatocytes meiosis 4. Second meiosis  spermatids iii. Spermiogenesis: spermatids become spermatozoa 1. Excess cytoplasm eliminated 2. Special structures added (mitochondria, flagellum) 3. Acrosomal vesicle added to nucleus – needed to penetrate egg  takes approx. 64 days for ii and iii iv. Capacitation: maturation of spermatozoa, necessary for fertilization 1. Glycoprotein coat added to sperm in duct system 2. Coat must be removed in uterus, uterine tubules = capacitation III. FERTILIZATION AND ZYGOTE DEVELOPMENT A. Fertilization i. Sperm usually encounter egg in ampulla of uterine tube: 1. Penetration of corona radiata – sperm releases enzymes from acrosomal cap  breaks through network holding cells together  Multiple sperms release enzymes, but only one will get through 2. Penetration of zona pellucida – acrosomal reaction 3. Fusion of membranes of sperm and egg – about 12 hours after fert. ii. Consequences of fertilization: 1. Fusion triggers release of granules  composition of zp and egg plasma membrane change  other sperm can’t penetrate = zona reaction 2. Oocyte completes meiosis II 3. Male pronucleus forms: enlarged nucleus, tail degenerates 4. Two nuclei fuse  zygote 5. Chromosomes prepare for mitosis  No increase in total cytoplasmic mass B. Cleavage i. Daughter cells = blastomeres; become smaller with each division (egg was very big; cells reach normal size after several divisions) ii. By 3 days: 12-32 blastomeres = morula iii. Day 3-4: morula enters uterus C. Compaction i. 9 cell stage: cells form a ball and closely adhere  more interaction Joined blastomeres form outside layer - smooth surface surrounded inner cells D. Cavitation i. Fluid cavity (blastocoele) forms  separates inner cells from outer ii. Inner and outer cells attached at embryonic pole iii. Now called blastocyst iv. Inner cells = embryoblast; outer cells = trophoblast – contributes to placenta E. Hatching i. Blastocyst now needs to grow in size, attach to uterine lining  must shed zp ii. Zp thins out and degenerates, outer blastomeres release enzymes that digest a hole in zp  blastocyst “hatches” IV. Implantation A. Day 6: trophoblast attaches to (proliferated) endometrium at embryonic pole B. Changes: i. Trophoblast becomes 2 layers 1. Syncitiotrophoblast – some cells fuse to form multinucleated “cell”, expands into endometrium  Produces hCGstimulates ovary to produce progesterone uterine lining maintained 2. Cytotrophoblast – inner layer remains unfused and mitotically active – as they divide they migrate to 1. ii. Decidua reaction: 1. Stromal cells enlarge, fill with glycoprotein and lipids 2. Prevents maternal immune reaction to conceptus 3. Sncytiotrophoblast penetrates stromal cells and erodes them to release nutrients 4. Glands in stroma enlarge, blood supply increases  help nourish conceptus until placenta takes over C. Complications i. Ectopic pregnancy - implantation outside uterus = LIFE-THREATENING (internal bleeding) ii. Placenta previa – implantation near cervix  bleeding during pregnancy and/or excessively so during delivery PRINCIPLES OF SKELETAL MUSCLE ACTION I. INTRODUCTION A. Elements of skeletal muscle function i. At least 2 points of attachment ii. Stimulated by somatic nervous system iii. Active muscle = tension generated iv. Muscle shortens  acttachments brought closer = movement B. Axioms i. For a muscle to have effect, it must cross a joint. ii. A muscle has the ability to effect any joint it crosses (sometimes not obvious which joints a muscle crosses – start at muscle attachment and trace along bone to other attachment) II. STRUCTURE A. Histological Organization of skeletal muscle i. Individual muscle fibers surrounded by endomysium ii. Fibers wrapped into fascicule and separated from each other by perimysium iii. All fibers bound into one muscle by epimysium iv. At ends of muscle fibers, three layers condense into connective tissue = periosteum v. Myotendenous junction = where muscle fibers end vi. Periosteum blends with tendons as it approaches attachment site vii. Sharpey’s fibers – penetrate bone and anchor periosteum to bone B. Contractile apparatus i. Sarcomere = interval between 2 striations (Z lines/Z bands) ii. Thick filaments extend from M line iii. thin filaments (with actin molecules ) extend from Z band and overlap with myosin heads of thick filaments iv. held together by structure protein titin C. Sliding filament theory i. tension = repeated making/breaking bonds between myosin heads and actin molecules on thin filaments ii. if tension is sufficient to overcome load (including deforming some connective tissue), muscle will contract iii. each sarcomere shortens by .6 micrometers  muscle has to have many sarcomeres iv. to generate force, have to have more bonds forming at once  more fibers per muscle D. Transmission of force – how does sarcomere action attach to muscle attachments? i. Actin filaments – don’t attach to discrete Z-line – attach to macromolecular meshwork (intracellular)  complexed with transmembrane integrins  in extracellular compartment, integrins attach to lamina, elements of connective tissue matrix ii. Sarcomere is part of macromolecular meshwork  muscle is elastic – can spring back iii. all structural elements can be deformed, but are also resilient: once work is done, there is stored energy  element of recoil III. GROSS CONFIGURATION OF MUSCLES A. Strap muscles – many sarcomeres in series  wide range of motion B. Mulipennate – pack lots of motive power into short area (ie deltoid) C. Other configurations? (not mentioned in lecture) IV. MODES OF CONTRACTION A. Concentric contraction – tension overcomes resistance  shortens B. Isometric contraction – tension doesn’t overcome  no motion C. Eccentric contraction – tension increases, but muscle lengthens (as in biceps as you lower something heavy by extending arm) V. CONTROL OF MUSCLE CONTRACTION A. Efferent innervation i. Final alpha-motor neuron (“once they say go that’s it”)– body in ventral grey rami of spinal cord ii. Muscle spindles allow contraction to be preset, monitor progress B. Motor unit – alpha-motor neuron and cell muscle fibers it innervates i. Can grade contraction ii. Can control which part of muscle is used (ie deltoid) C. Afferent return – exteroception and proprioception VI. ANALYSIS OF MUSCLE ACTIONS A. Angular – change joint angle B. Shunt – end of bone moves towards/away (gravity can cause too) C. Translation/Shear – end of bone displaced D. Spin – bone spinning about long axis VII. REFLEXES A. Afferent and efferent control of a voluntary muscle B. Inhibitory neuron – can block reflex C. Damage: i. Cut afferent  no reflex, voluntary action maintained ii. Cut efferent  sensory input intact, but no reflex or voluntary action iii. Cut spinal cord  no voluntary action, but reflex intact (also no inhibition of reflex) PECTORAL REGION AND SHOULDER I. PECTORAL REGION a. Mammary gland nd th i. Between 2 and 6 ribs, lateral border of sternum and midaxillary line ii. Overlies pectoralis and serratus anterior iii. Attached to skin by suspensory ligaments/ligaments of Cooper iv. Retromammary space – between breast and pectoral fascia, contains blood and lymph vessels, nerves; allows some movement of breast on thoracic wall b. Blood supply i. Thoracoacromial branches ii. Lateral thoracic artery and branches iii. Brances from posterior intercostal arteries iv. Internal thoracic artery  perforating branches medial mammary branches c. Lymphatic drainage i. most to subareolar lymphatic plexus ii. >75% then to anterior or pectoral nodes of axillary groupclavicular lymph nodesmain lymphatic trunk venous system (some may drain to other axillary nodes) iii. Rest goes to parasternal lymph nodes  brachomediastinal lymphatic trunk  venous system d. Breast cancer i. Usually adenocarcinomas from epithelial cells of lactiferous ducts ii. Spreads through lymphatic vessels (may spread via venous system to brain) iii. Drains to axillary lymph nodes = common site of metastasis iv. May also develop in supraclavicular lymph nodes, opposite breast, abdomen II. SHOULDER a. Osteology i. Sternum – body, jugular notch, manubrium, xiphoid process ii. Clavicle – acromial facet, coronoid tubercle, sterna facet, subclavian groove, impression for costoclavicular ligament, anterior/posterior surface *curve shift = common site of fracture iii. Scapula – acromion, coracoid process, glenoid cavity, medial/lat borders, spine, superior/inf angles, suprascapular notch, supraglenoid/infraglen tubercle, supraspinous/infraspinous fossa iv. Humerus – deltoid tuberosity, greater/lesser tubercle, head, bicipital groove, spiral groove *anatomical neck is site of growth plate in development, surgical neck is common site of fracture b. Articulations and associated structures i. Sternoclavicular (SC) joint – saddle type; has fibrocart. disc (helps with weight dist.); elevation/depression, protraction/retraction, rotation (as you raise shoulder) 1. Sternoclavicular, interclavicular, costoclavicular ligaments ii. Acromoioclavicular (AC) joint – plane type synovial joint (glides), has fibrocart. disc; rotation 1. Acromioclavicular ligament, coracoclavicular ligament iii. Glenohumeral (GH) joint – ball and socket synovial joint; flex/ext, AB/AD, int/ext rotation *glenoid fossa much smaller than humeral head “bowling ball and golf tee”  lacks stability, can dislocate, stabilized by non-contractile and contractile elements: 1. Glenoid labrum – fibrocart. disc within joint, builds up edges; glenoid cavity, labrum, joint capsule 2. Glenohumeral ligaments – superior, medial, inferior (SGHL, MGHL, IGHL) 3. Coracohumeral ligament – thickens capsule 4. Coracoacromial ligament – helps pack structures 5. Transverse humeral ligament 6. Subacromial/subdeltoid bursa – between coracoacromial arch and supraspin. tendon; gliding (contains synovial fluid)  decreases friction 7. Contractile elements = muscles of rotator cuff – see end iv. Scapulothoracic joint – functional, not structural joint; elev/depress, protraction/retract, down/up rotation c. Kinematics i. Shoulder 1. Flexion/Extension – in saggital plane 2. Abduction/Adduction – coronal and horizontal plane 3. With shoulder in AB – internal/external rotation in saggital and horizontal planes ii. Scapulohumeral rhythm 1. scapulothoracic and GH both move to elevate shoulder 2. Have to laterally rotate humerus (move greater tuberosity out of the way) to achieve full ROM (abduction) d. Musculature i. Posterior axioappendicular muscles (extrinsic) 1. Posterior a. Superficial i. Trapezius- elevate and upward rotate scapula (upper), adducts (middle), depress and downward rotate (lower) ii. Latissimus Dorsi – shoulder extension, adduction, IR b. Deep i. Levator Scapulae – elev and down rotation of scap ii. Rhomboid Major – AD/retract, down rotates scap iii. Rhomboid minor – works with major 2. Anterior a. Pectoralis major – adducts, medially rotates humerus b. Pec minor – stabilize scapula c. Serratus Anterior – protract and upward rotation of scapula, compresses against thoracic wall d. Subclavius – anchor and depress scap ii. Scapulohumeral muscles (intrinsic) 1. Deltoid – flex (anterior), abduct (middle) , extend (poster) shoulder 2. Teres Major – medial, internal rotation of shoulder 3. Rotator cuff muscles (SItS) a. Subscapularis – medial, internal rotation Order of attachment b. Supraspinatus – shoulder abduction on humeral head c. Infraspinatus – lateral*, external rotation from medial to lateral d. Teres Minor – lateral*, external rotation *prevents impaction of greater tubercle on acromion Muscles and tendons prevent GH dislocation: i. Shunt or distraction/compression (away/tow joint) ii. Sheer/translation (up and down) iii. Angular motion e. Rotator cuff injury: i. Use of upper limb above horizontal (throwing, swimming) ii. Allow humeral head and rot cuff to impinge on coracoacromial arch iii. May produce irritation of arch, inflamm of cuff, esp supraspinatus tendon iv. Rupture of this tendon  upward shift of humerus THE BRACHIAL PLEXUS I. NERVE SUPPLY a. Ventral rami of C5-T1 (from from both anterior (motor) and posterior (sensory) roots) b. Organization i. Roots – formed by ventral rami ii. Trunks – roots combine into superior, middle, inferior iii. Divisions – trunks divide into anterior and posterior iv. Cords – divisions combine into medial, lateral, posterior – all wrapped around axillary artery, named according to relation to it v. Branches – cords divide into 2 nerves each – musculocutaneous, median (from 2 cords), ulnar, radial, axillary 1. Superclavicular branc
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