aps1 notes
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SKELETAL SYSTEM
CLASSIFICATION OF BONES - 206
Axial skeleton
Long axis of the body Skull, vertebral column, rib cage Most involved in protecting, supporting, carrying other body parts
Appendicular skeleton
Upper and lower limbs, girdles (shoulder/hip bones) that attach limbs toaxial skeleton
Involved in locomotion and manipulation of environmentClassified by shape
Long bones longer than they are wideo Shaft + 2 endso All limb bones except patella, wrist + ankle bones
Short bones approximately cube shapedo Wrist and ankles
Flat boneso Thin, flattened, usually a bit curvedo Sternum, scapulae, ribs, most skull bones
Irregular boneso Complicated shapeso Vertebrae, hip bones
Bone development
In uteroo Derived from mesenchymeo Development
Postnatalo Growth
Formation of the bony skeleton
Before week 8, skeleton entirely fibrous membranes + hyaline cartilage Intramembranous ossification bone developing from fibrous membrane
o Membrane bone Endochondral ossification bone development by replacing hyaline
cartilage
o Cartilage/endochondral bone
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Intramembranous ossification
Results in formation of cranial bones + clavicleso Frontal, parietal, occipital, temporal
Most are flat bones ~Week 8 of development, ossification begins on fibrous CT membranes
derived from mesenchyme
4 major steps of intramembranous ossification
Ossification centres appear in fibrous CT membraneo Mesenchymal cells differentiate osteoblasts
Bone matrix (osteoid) is secreted within fibrous membrane and calcifieso Osteoblasts secrete osteoido Trapped osteoblastsosteocytes
Woven bone + periosteum formo Osteoid accumulates between/around blood vessels randomly
results in network of woven boneo Vascularised mesenchymeperiosteum
Lamellar bone replaces woven bone, red marrow appearso Trabeculae deep to periosteum thicken later replaced with
mature lamellar bone, forming compact bone plates
o Spongy bone remains and vascular tissue red marrowEndochondral ossification
Almost all bones form by this method From 2ndmonth of development, hyaline cartilage bones used as models
for bone construction
More complex than intramembranous because hyaline cartilage must bebroken down as ossification proceeds
Primary ossification centre centre of hyaline cartilage shaft Secondary ossification centre one or both epiphyses gain bony tissue Structure
o Diaphysiso Epiphysiso Medullary cavity lined with endosteum
Filled with yellow marrowo Outer covering periosteum
Double membrane Outer fibrous layer DICT for strength Connect to compact bone by Sharpeys fibres Internal membrane osteogenic layer
Osteoblasts Osteoclasts Osteogenic cells
Vascular and innervatedo Compact bone
Osteons
Lamellae
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Harversian system (central canal) Volkmanns canals (perforating canals) connect
blood/nerve supply of periosteum to other canals
Lacunae/osteocyteso Spongy bone
Trabeculae, filled with red or yellow marrowOSSIFICATION
Conversion of hyaline cartilage to bone
PRIMARY diaphysis SECONDARY epiphyses FINAL epiphyseal plates
Postnatal bone growth
Long bones lengthen entirely by interstitial growth of epiphyseal platecartilage + its replacement by bone
Cartilage cells at the top growth/proliferation zoneo Divide quickly, pushing the epiphysis away from diaphysis entire
long bone lengthens
Older cells enlarge surrounding cartilage matrix calcifies chondrocytesdiecalcification zone
Bone growth ends with epiphysis and diaphysis fuse epiphyseal platecloser
o ~18 in femaleso ~21 in males
Can continue to grow in width
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Foetal skeleton
Ossificaion of skull starts late in second month of development At birth, skull bones sill incomplete connected by fontanelles
o Allow infants head to be compressed slightlyBONE REMODELLING AND REPAIR
Bone remodeling
Comprise bone deposit and resorption Bone deposit where bone is injured or requires extra strength by
osteocytes
Bone resorption osteoclastsControl of remodeling
Negative feedback maintaining Ca2+ homeostasis Reponses to mechanical/gravitational forces
Hormonal controls
Parathyroid hormone (PTH) parathyroid glandso Secretes when low blood Ca2+ levelso Stimulate resorption of bone osteoclasts break down bone
Calcitonin much more minimal effectMechanical stress
Muscle pull + gravity Wolffs law bone grows/remodels in response to demands placed on it
o Bone anatomy reflects common stresses Loading usually off centre bends bone (tension)
o As a result, bone usually thickest in middleHOMEOSTATIC IMBALANCES OF BONE
Osteomalacia and Rickets
Inadequate mineralization of bones Osteoid produced but calcium salts not deposited soften and weaken
bones
Painful when weight put on affected bones Osteomalacia in adults Rickets in children much more severe because bones are still growing Often caused by insufficient calcium in diet or vit D deficiency
Osteoporosis
Bone resorption > bone deposit bone mass decreasesbecome porousand light
Spongy bone of spine most vulnerable Most often occurs in the aged
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CRANIUM
8 cranial bones: parietal + temporal (2 each) Frontal, occipital, sphenoid, ethmoid Brains protective helmet
Frontal Bone Anterior cranium Articulates posteriorly
o Paired parietal bones via coronal suture Forehead vertical squamous part
o Ends inferiorly at supraorbital margins Forms superior margins of the orbits + most of the anterior cranial fossa
o Supraorbital margins pierced by supraorbital foramen supraorbital artery + nerve passes to forehead
Glabella between orbitso Lateralfrontal sinuses
Frontonasal suture joins nasal to frontal boneParietal bones + major sutures
One on each side, separated by sagittal suture Form most of the superior/lateral aspects of the skull bulk of cranial
vault
Major sutures:o Coronal parietalfrontalo Sagittal parietalcranial midlineo
Lambdoid parietal
occipitalo Squamous patietaltemporal
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Occipital bone
Forms most of skulls posterior wall + base Articulates anteriorly with: parietal, temporal bones via: lambdoid +
occipitomastoid sutures
Joins with sphenoid bone in cranial floor via basilar region Forms posterior cranial fossa Foramen magnum at base inferior part of brain connects with spinal
cord
Occipital condylesarticulate with atlasTemporal bones
Located under parietal bones articulate at squamous sutures 4 regions
o Squamous Zygomatic process
o Tympanic Surrounds external acoustic meatus Styloid process
o Mastoid Mastoid process Stylomastoid foramen
o Petrous Deep Cranial base middle cranial fossa Middle/internal ear cavities Jugular foramen, carotid canal Foramen lacerum Internal acoustic meatus
Sphenoid bone Consists of central body + 3 pairs of processes
o Greater wingso Lesser wingso Pterygoid processes
Sphenoid sinuses Superior sella turcica
o Seat hypophyseal fossa Houses pituitary gland
Greater wings project laterally and formo Middle cranial fossao Dorsal walls of orbitso External wall of skull
Lesser wings formo Part of the anterior cranial fossao Medial walls of orbits
Pterygoid processes project inferiorlyo Anchor pterygoid muscles chewing muscles
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Openings of the sphenoid bone
Optic canals Superior orbital fissure Foramen rotundum/ovale/spinosum
Ethmoid bone Deepest skull bone Forms most of bony area between nasal cavity + orbits Superior formed by cribriform plates
o Help form roof of nasal cavitieso Anterior cranial fossao Punctured by tiny holes olfactory foraminao Crista galli superior process
Secures brain in cavity Perpendicular plate
o Forms superior part of nasal septum divides nasal cavity intoleft/right halves Lateral masses with ethmoid sinuses
o Superior nasal conchae Lateral surfaces of lateral masses orbital plates
o Medial walls of orbitsFACIAL BONES
Mandible
U-shaped Largest, strongest facial bone Ramus meets body at angle Two processes separated by mandibular notch Coronoid process at anterior Mandibular condyle at posterior
o Articulates with mandibular fossa of temporal bone Body anchors lower teeth alveolar margin = sockets Mental foramina
Maxillary bones
Upper jaw/central portion of facial skeleton Articulates with all facial bones except mandible Carry upper teeth in alveolar margins Palatine processes bony roof of mouth
o Project posteriorly from teeth Frontal processes lateral nose bridge Lateral to nasal cavity maxillary sinuses Articulate with zygomatic bones via zygomatic processes Inferior orbital fissure at junction of maxilla with greater wing of
sphenoid
Infraorbital foramen below eye socket
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Zygomatic bones
Cheekbones Articulate with zygomatic processes of
o Temporal boneso Frontal boneo Maxillae
Cheeks and part of inferolateral orbital marginsNasal bones
Fused medially forms bridge of nose Articulate with frontal bone, maxillae, perpendicular plate of ethmoid
bone, cartilages of external nose
Lacrimal bones
Contribute to medial walls of each orbit Articulate with:
o Frontal bone superiorlyo Ethmoid bone posteriorlyo Maxillae anteriorly
Contains deep groove forms lacrimal fossao Houses lacrimal sacallows tears to drain from eye surface into
nasal cavity
Palatine bones
L shapedo Horizontal + perpendicular plates
Articular processeso Pyramidalo Sphenoidalo Orbital
Horizontal platesjoined medially, form posterior part of hard palate Perpendicular plates form posterolateral walls of nasal cavity + small part
of the orbits
Vomer bones
Forms inferior part of the nasal septumInferior nasal conchae
Thin, curved bones in the nasal cavity Project medially from lateral walls of nasal cavity
o Inferior to middle nasal conchae of ethmoid bone Form lateral walls of nasal cavity
Hyoid bone
Lies inferior to mandible in anterior neck Only bone that does not articulate directly with any other bone Horseshoe-shaped
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Special characteristics of the orbits and nasal cavity
The Orbits
Encases eyes, cushioned by fatty tissue Also contains muscles that move the eyes + lacrimal glands Consists of seven bones
o Frontal, sphenoid, zygomatic, maxilla, palatine, lacrimal andethmoid bones
Superior/inferior orbital fissues + optic canals also seenNasal Cavity
Constructed of bone and hyaline cartilage Roofcribriform plates of ethmoid Lateral wallslargely superior/middle conchae of ethmoid bone,
perpendicular plates of palatine bones + inferior nasal conchae
Floorpalatine processes of maxillae + palatine bones Divided into right + left parts by nasal septum
o Vomer inferiorly, perpendicular plate of ethmoid superiorlyParanasal sinuses
Mucosa-lined, air-filled cavities that cluster around the nasal cavity Five skull bonesfrontal, sphenoic, ethmoid + pairedmaxillary (2)
sinuses
Air enters sinuses from nasal cavity mucus formed by sinus mucosaedrains into nasal cavity
Mucosa helps to warm/humifidy inspired air
Lighten the skull + enhance resonance of the voiceHuman skull
Larger cranial case, especially frontal bone (bigger brain = greaterintelligence), smaller snout (less dependency of smell), smaller mandible
(hunter/gatherer diet, omnivores vs herbivores), large orbits and
protected (greater reliance on vision)
THE VERTEBRAL COLUMN
26 irregular bones connected to provide curvature and flexibilityo 7 cervical (neck)o 12 thoracic (middle)o 5 lumbar (back)o COMMON MEAL TIMES 7am, 12noon, 5pm
Become progressively larger from cervical lumbar must supportgreater weight
Inferior to lumbar vertebrae sacrumo Articulates with hip bones of the pelviso Terminuscoccyx
Curvaturessinusoid (S) shape from lateral view (posterolateral)o Increase resilience + flexibility of spine Acts like spring rather than rod
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o Cervical + lumbar concaveo Thoracic + sacralconvex
Abnormal spinal curvatures
Scoliosis Abnormal lateral curvature Most often in thoracic region
Kyphosis
Dorsally exaggerated thoracic curvature Hunchback
Lordosis
Accentuated lumbar curvature Can arise from potbellies and pregnant women
o Adjustment to preserve centre of gravityIntervertebral discs
Cushionlike pad Two parts
o Inner gelatinous nucleus pulposusrubber ball Elasticity + compressibility
o Collar composed of collagen fibres + fibrocartilage annulusfibrosus
Limits expansion of nucleus pulposus when spine iscompressed
Withstands twisting forces + resists tension in spineHerniated (prolapsed)/slipped disc
Usually involves rupture of the annulus fibrosus followed by protrusion ofnucleus pulposus through annulus
o Can press on spinal cord/spinal nervenumbness/excruciatingpain
GENERAL STRUCTURE OF VERTEBRAE
Body/centrum anteriorly
o Disc shapedo Weight-bearing region
Vertebral arch posteriorly formed by:
Two pediclesshort bony pillarso Project posteriorly from bodyo Form sides of archo Inferior + superior notches provide lateral openings between
adjacent vertebraeintervertebral foramina (spinal nerves)
Two laminaeflattened plateso Form posterior part of arch
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Body + vertebral arch enclose vertebral foramen
Successive vertebral foramenvertebral canal (spinal cord)Seven processes project from vertebral arch
Spinous process arises from junction of two laminae Transverse process extends laterally from each side of vertebral arch Superior/inferior articular process (2 each)
o Protrude superiorly and inferiorlyo Smooth joint surfacesfacets covered with hyaline cartilageo Articular surfaces join to next vertebra
Regional vertebral characteristics TABLE OF COMPARISON
Movements: flexion/extension, lateral flexion, rotationCervical vertebrae
C1-C7lightest vertebrae C3-C7 features
o Oval body wider side to side than anteroposterior dimensiono Except in C7, spinous process is short, projects directly back + bifid
(splits at tip)
Large vertebral foramen generally triangular Transverse process contains transverse foramen vertebral arteries pass
to service brain
Spinous process of C7 not bifid much larger than other cervicalvertebrae
C1 + C2atlas + axis, more robust than tpical cervical vertebraeo No intervertebral disco Atlas C1no body, no spinous process holds up the worldo Axis C2 has a body (dens, odontoid peg missing body of atlas)
Thoracic vertebrae
12 all articulate with ribs Increase in size from first to last Body roughly heart shaped
o Bears two small facets demifacetsreceive head of ribs (T10-T12 only single facet)
Vertebral foramen circular Spinous process long, points sharply downwards T1-T10 transverse processes have facets transverse costal facets,
articulate with tubercles of the ribs
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Lumbar vertebrae
Receives most stress Large bodies, kidney shaped superiorly Pedicles/laminae shorter and thicker than those of other vertebrae Spinous processes short, flat, hatchet shapedrobust Triangular vertebral foramen
Sacrum
Posterior wall of the pelvis Formed by 5 fused vertebrae Articulates superiorly with L5 via superior articular processes, inferiorly
with coccyx
Articulates laterally with two hip bones via auricular surfacesformssacroiliac joints of pelvis
Wing-like alae laterally Vertebral canal continues inside sacrum as sacral canal Enlarged external opening sacral hiatuslaminae of fifth sacral
vertebrae fail to fuse medially
Coccyx
Tailbone 4-5 fused vertebrae Articulates superiorly with the sacrum
Bipedalism
Spinal curvature allows maintaining centre of mass, flexibility, balance
Increasing thickness/strength of descending vertebrae adaptation forweight bearing
Rib cage laterally orientated vs anteroposteriorly as in quadrupedsTHORACIC CAGE
Thoracic vertebrae Ribs Sternum
o Sternal angle Costal cartilagessecure ribs to sternum Bony thorax forms protective cage around vital organs of thoracic cavity,
supports shoulder girls + upper limbs + provides attachment points for
muscles
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Ribs
12 pairs All attach posteriorly to thoracic vertebrae curve down toward anterior
body surface
Superior 7 rib pairs attach directly to sternumindividual costalcartilages
o TRUE ribs Remaining 5 pairsfalse ribs
o Attach indirectly to sternum or entirely lack sternal attachmento 8-10 joining the costal cartilage immediately above ito 11-12 floating ribsno anterior attachments
Structureo Bulk of ribshafto Superior border is smootho Inferior border is sharp, thin and has a costal groove on inner faceo Head wedge-shaped articulates with vertebral bodies by twofacets
Body of same numbered thoracic vertebra Body of vertebra immediately superior
THE APPENDICULAR SKELETON
Bones of limbs + their girdleso Girdles connect axialappendicular skeletono Pectoral girdleo Pelvic girdle
Enables movement of manipulative lifestylePectoral (shoulder) girdle
Consists of clavicle anteriorly and scapula posteriorlyo Anteriorly, medial end of each clavicle joins the sternumo Posteriorly, distal ends of clavicles meet scapulae laterally
Scapulae attached to thorax + vertebral column only bymuscles
Attach upper limbs to axial skeleton Very light, allow the most mobility in the body because:
o Only clavicle attaches to axial skeleton scapula can move freelyo Shoulder joint socket shallow + poorly reinforced
Very unstableClavicles DISTINGUISH ORIENTATION
Cone shaped at medial sternal end, flat at acromial end Superior surface fairly smooth, inferior surface ridges/grooved by
ligaments + muscle action
Lateral 1/3 concave, medial 2/3 convex and rounded Not very strong likely to fracture
o Curved to ensure anterior fractures if posterior, subclavianartery would be damaged
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Scapulae
Thin, triangular flat bones 3 borders superior, medial and lateral 3 angles
o Lateral angle superior + lateralo Superior angle superior + medialo Inferior angle medial + lateral
Glenoid cavity articulates with the humeruso Shoulder joint
Anterior surface concaveo Coracoid process projects anteriorly from superior border
Anchors biceps brachii Bounded by suprascaular notch + glenoid cavity
Posterioro Prominent spine that ends laterallyo Acromion roughened triangular projection
Fossaeo Infraspinous + supraspinous inferior + superior to spineo Subscapular fossa entire anterior scapular surface
Upper limb
Humerus typical long bone
Articulates with scapula at the shoulder + with radius and ulna at elbow Head fits into glenoid cavity of scapula Greater + lesser tubercles sites of attachment of rotator cuff muscles
o Separated by intertubercular sulcus/bicipital groove guidestendons
Midway down the shaft deltoid tuberosityattaches the deltoidmuscle
Distal two condyleso Medial trochlea - articulates with ulnao Lateral ball-like capitulum articulates with radiuso Medial/lateral epicondyles muscle attachment sites
Fossaeo Anterior coronoid fossa superior to trochleao Posterior olecranon fossa
Forearm
Radius + ulnaUlna
Slightly longer than the radius mainly responsible for elbow joint withhumerus
Proximal end looks like adjustable end of monkey wrencho Two processes olecranon (elbow) + coronoid
Distal end shaft narrows and ends in a knoblike head
o Medialstyloid process
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Radius
Thin at proximal end wide at distal end Head shaped like head of a nail Styloid process
Wrist and hand Carpals wrist Metacarpals palm Phalanges fingers
Pelvic (hip) girdle
Attaches lower limbs to axial skeleton Transmits full weight of upper body to lower limbs Very secure deep sockets Formed by hip bones
o 3 separate bones: ilium, ischium, pubiso Deep socketacetabulum at point of fusion receives head of the
femur
Ilium
Forms superior region of coxal bone Superior edge iliac crests Anterior superior iliac spine Posterior superior iliac spine Greater sciatic notch
Iliac fossa
Ischium
Posteroinferior part of the hip bone Ischial tuberosity what we sit on
o Strongest parts of the hip bonesPubis
Anterior portion of hip bone Lies horizontally Obturator foramen closed by a fibrous membrane Pubic bones joined by fibrocartilage discpubic symphysis
o Inferiorinverted V-shaped pubic arch
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Pelvis structure + gender
Pubic arch Sacral curvature Pelvic brim
Female Generally tilted forward shallow, has a greater capacity Lighter, thinner, smoother bones Smaller acetabulum, farther apart Broader pubic angle (80-90 degrees), more rounded
Male
Generally tilted far less forward narrow and deep true pelvic cavity Heavier, thicker, more prominent markings on bones Larger acetabulum, closer together More acute pubic angle (50-60 degree)
Lower limb
Thigh femur
Largest, longest, strongest bone in the body Headneck Junction of shaft + necklateral greater trochanter and posteromedial
lesser trochanter
o Projections serve as sites of attachment for thigh/buttock muscles
Long vertical ridge along shaft
linea aspera Medial/lateral condylesarticulate with tibia
o Medial/lateral epicondyles Patellatriangular sesamoid bone secures anterior thigh muscles to
tibia
Tibia
Receives weight of body from femur + transmits it to the foot Tibial tuberosity patellar ligament attaches Distally, tibia is flatinferiorly, medial malleolus
o Medial bulge of ankleFibula
Stick-like Articulates proximally and distally with tibia
o Proximal end = heado Distal end lateral malleoluslateral ankle bulge
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Foot
Tarsus 7 tarsal bonesform posterior part of foot Talus articulates with tibia/fibula superiorly Calcaneus heel of the foot Metatarsals 5 Phalanges 14
JOINTS/ARTICULATIONS
Point of articulation of two or more bones Provide mobility Hold it together + protect Weakest parts of skeleton but CT makes it resist crushing or tearing
Classification of joints
By structure and function FUNCTION range of movement
o Synarthrosis: (together join) immoveableo Amphiarthrosis: (both sides) slightly moveableo Diarthrosis: freely moveable
STRUCTURALo Fibrous: no cavity, fibrous CTo Cartilaginous: no cavity, cartilageo Synovial: joint cavity + capsule
Fibrous joints
Bones joined by fibrous tissue
dense fibrous connective tissue
Most immoveable E.g. Sutures, syndesmoses
Synovial joines
Fluid-containing joint cavity at separation point Permits substantial freedom of movement
General structure of synovial joints
Articular cartilage hyaline cartilage covering articular surfaces of boneo Absorb compression + prevent crushing of bone ends
Joint (synovial) cavity potential space containing synovial fluid Articular capsule 2 layers
o External layer fibrous capsule DICTo Inner layer synovial membrane loose CT
Covers all internal joint surfaces that are not hyalinecartilage
Synovial fluido Reduces friction between cartilages
Reinforcing ligamentso Reinforces joints
Nerves and blood vessels
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Bursae/tendon sheaths
Bursae flattened fibrous sacs lined with synovial membrane containsthink film of synovial fluid
o Occur where ligaments, muscles, skin, tendons or bones rubtogether
Tendon sheaths elongated bursa that wraps completely around atendon subjected to friction
o Common where several tendons are crowded together withinnarrow canals
Movements allowed by synovial joints
Muscles origin attached to immoveable/less moveable bone Insertion attached to more moveable bone Range of movement
o Non-axial (slipping movements only)o Uniaxial one planeo Biaxial two planeo Multiaxial in or around all 3 planes
Types of movemento Glodingo Angular movementso Rotation
Gliding
Flat bone surface slips over another (back + forth, side to side)o Very limited movement
Intercarpal/intertarsal joins, flat articular processes of vertebraeAngular movements
Increase/decrease angle between two bones Flexion, extension, hyperextension, abduction, adduction, circumduction
Flexion
Bending movement, decreases angle of the joint brings articulatingbones closer together
o E.g. bending head forward on the chest, bending body trunk/kneefrom straight to angled position, lifting the arm anteriorly
Extension
Reverse of flexionoccurs at same joints Increases the angle between articulating bones typically straightens a
flexed neck, body trunk, elbow or knee
Excessive extensionhyperextension
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Abduction
Movement of a limb away from the midline/median plane along thefrontal plane
o E.g. raising arm/thigh laterallyAdduction
Opposite of abduction Movement of limb toward the body midline
Circumduction
Movement of a limb so that it describes a cone in space Hip/shoulder ball and socket joints
Rotation
Turning a bone around its own long axis Only movement allowed between two cervical vertebral/common at thehip Medial rotationdirected toward the midline Lateral rotationdirected away from the midline
Supination + pronation
Supination rotating forearm laterally palm faces anteriorly/superiorlyo Radius/ulna parallel
Pronation rotating forearm medially palm faces posteriorly/inferiorlyo Radius/ulna form X shape
Dorsiflexion + plantarflexion
Dorsiflexion lifting up the foot so that superior surfaceshin Plantarflexion pointing the toes (towards plants)
Types of synovial joints
Plane joints
Flat articular surfaces allow only short nonaxial gliding movements Gliding joints intercarpal/intertarsal, between vertebral articular
processes
o NO ROTATIONHinge joints
Cylindrical end of one bone fits into trough shape on another bone Movement along a single plane door hinge Permit flexion and extension
Pivot joints
Allows uniaxial rotation around long axis E.g. radius + ulna
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Injuries
Knees most susceptible to sports injuries because of high reliance onnonarticular factors for stability carry the bodys weight
Very vulnerable to horizontal blows e.g. football/ice hockey 3 Cs collateral ligaments, cruciate ligaments, cartilages (menisci) Most damaging lateral blows to extended knee tear TCL and medial
meniscus attached to it + anterior cruciate ligament
Q ANGLE
Small Q-angle genu varumo Bowlegged excess pressure placed on medial aspect of knee joint
destruction of the cartilage (arthrosis)
Large Q-angle genu valgumo Knocked knees overstretching of the TCL + excess pressure on
the lateral meniscus
Shoulder joint
Most freely moving joint but not very stable Ball and socket joint Humerus fits into glenoid cavity of scapular Articular capsule very loose and thin so great freedom of movement Few ligaments reinforcing shoulder joint primarily on anterior aspect
Structure
Incomplete girdle one attachment point to the axial skeleton(sternoclavicular joint) scapula attached via muscles to posterior wall ofthe thorax
o Allows greater range of movement Sternoclavicular joint synovial joint allowing fliding/axial rotation
Joint capsule
Loose fibrous sac extending from shallow glenoid cavityanatomicalneck of the humerus
Glenohumeral ligaments extend anteriorly from glenoid cavity anatomical neck loose and provide minimal strength to the joint
Weakest partinferior aspectDegree of movement
Role of upper limb does not involve weight-bearing/locomotionadapted for manipulation, balance and mobility
Shoulder joint allows flexion, extension, abduction, adduction,medial/lateral rotation + circumduction
Greater range of movement than any other joint within the body becauseof shallow glenoid fossa, loose capsule + ligaments, + mobility
Strength of joint relies on rotator cuff muscles secure and stabilize thejoint (attach scapula to humerus)
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Hip (coxal) joint
Ball and socket joint Good range of motion but not nearly as wide as shoulders range
o Movements limited by strong ligaments + deep socket
Joint formed by articulation of head of femus with acetabulum of hip bone Depth enhanced by circular rim of fibrocartilage Ligamentum teres aka ligament of the head of the femur
o Flat intracapsular band running from head of femur to lower lip ofthe acetabulum
o Contains an artery that helps supply the head of the femur
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Structure
Firmly attached to sacrum posteriorly completely encircles the pelvis toarticulate anteriorly at the pubic symphysis
o Pelvic girdle stable for transfer of weight to lower limbs via hipjoint
Sacroiliac joint partly synovial/partly fibrouso Thick fibrous ligaments restrict movement only slight gliding
movement allowed
Pubic symphysis is cartilaginous joint allowing very little or no movementJoint capsule
Fibrous capsule of hip joint very strong cylindrical sleeve enclosing deepjoint/most of femoral neck
Capsular ligaments iliofemoral, pubofemoral, ischiofemoral reinforcelongitudinal fibres of joint capsule
Degree of movement
All ball and socket movements possible but movement limited byacetabulum, muscles, ligaments and contact with coxal bones
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Osteoarthritis (degenerative joint disease)
Most common chronic arthritis wear and tear Softened, roughened, pitted, eroded articular cartilages Exposed bone tissue thickens stiff/less mobile joints
Rheumatoid arthritis
Chronic inflammatory disorder autoimmune disease Arises between 30-50 Early stages joint tenderness/stiffness common
Begins with inflammation of synovial membrane of affected joints Inflammatory cells migrate into joint cavity which destroy body tissues
o Synovial fluid accumulatesjoints swello Inflamed synovial membrane thickens erodes cartilageo Scar tissue connects bones ossifies/ joins immobilised
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SKELETAL MUSCULE TISSUE
MUSCULAR SYSTEM
Allows movement and posture attaches to bone Protection Heat production and storage Muscles made of CT and muscle fibres Regulation of blood/air flow (SM) All type of muscle excitable, contractile, extensile and elastic
SKELETAL MUSCLE
Striated Multinucleated Long Voluntarily controlled
STRUCTURE
Individual muscle fibres wrapped in endomysium Group of muscle fibres called a fascicle wrapped in perimysium Group of fascicle make up the muscles wrapped in epimysium Vascular has blood vessels running through it
MORE DETAIL
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Myofibril contains actin and myosin proteins Myofibril surrounded by sarcoplasmic reticulum (smooth ER) Muscle fibre plasma membrane called sarcolemma Sarcolemma has T-tubules which allow Ca to flow through and helps in
contraction
SMOOTH MUSCLE
FOUND: walls of tubes and hollow organs e.g. bladder, gut, bronchi Controls flow of blood, movement through gut, secretions/excretions to
be expelled
Single nucleus, not striated Gap junctions allow linked cells to act in unison Involuntarily controlled High capacity for stretch and elongation Not highly structured
CARDIAC MUSCLE
Main constituent of the heart Striated Involuntary Single nucleus Separated by intercalated discs
o Gap junctions allow functioning as functional syncytia (heartcontracts as a whole)
PacemakerNaming skeletal muscles
Location indicates bone/body region Shape some named for distinctive shapes e.g. orbicularis is round Relative size e.g. maximus, minimus, longus etc Direction of muscle fibres usually in relation to midline e.g. rectus =
straight, transversus = at right angles to midline etc
Number of origins e.g. biceps = 2 origins, triceps = 3 origins or heads Location of the attachments e.g. sternocleidomastoid
Action flexor, extensor, adductor
Arrangement of fascicles
Circular surround external body openingsclose by contracting sphincters
Convergent broad origin, narrow insertion fan shaped e.g. pec major Parallel straplike e.g. Sartorius Pennate short fascicles, attach obliquely feather
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Actions of muscles point of reference + movement
Agonist/prime mover: muscle mainly responsible for producingmovement e.g. biceps brachiielbow flexion
Antagonists: muscle whose action opposes the agonist e.g. triceps brachiibiceps brachii
Synergists: Helper to the agonist e.g. teres major + latissimus dorsi Fixators: synergistic muscles that specifically immobilize a bone e.g.
rhomboids fixing scapula
Rule of thumb
Muscles in the same compartment generally perform the same action Generally - ANTERIOR muscles from hip neck = flexors
o POSTERIOR muscles from hip downwards = flexorsFacial muscles
Obicularis oculi surrounds the orbitcloses the eye Zygomaticus major + minor pair extending diagonally from
cheekbonecorner of mouth, raises lateral corners of mouth upward
(smiling muscle)
Risorius inferior/lateral to zygomaticus draws corner of lip laterally(laughing muscle)synergist of zygomaticus
Obicularis oris forms the lips allows protrusion/closure of lips Buccinator deep to masseter principle muscle of cheek, compresses
cheek, holds food between teeth while chewing, draws corner of mouth
laterally
Masseter covers lateral aspect of mandibular ramus
prime mover ofjaw closer, elevates mandible
Temporalis closes jaw, elevates + retracts mandibleNeck muscles
Sternocleidomastoid two-headsflexes/laterally flexes/laterallyrotates the head
o Prime mover of head flexion Splenius extend from upper thoracic vertebrae to skull (mastoid
process)extend/hyperextend the head
Trunk muscles Erector spinae prime movers of extension of the vertebral column
o Spinalisalong spinous processeso Longissimusintermediate muscleo Iliocostalismost lateral muscle group
Quadratus lumborum lateral flexion of the vertebral column, extensionof lumbar spine, assists in respiration
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Abdominal wall musclesprime movers of flexion of vertebral column +
antagonists to erector spinae muscles
Rectus abdominis medially superficial External oblique laterally superficiallargest of the lateral muscles
o Pocketfibres run downwards and medially Internal oblique opposite direction to external obliquedeep to above
o Fibres run upward and medially Transversus abdominis deepest muscle of abdominal wall
o Fibres run horizontallyMuscles that stabilize the shoulder
Anterior
Pectoralis minor deep to pectoralis major, abducts scapula Serratus anterior holds scapula against chest wall
o Prime mover of scapula abduction punching musclePosterior
Trapezius 2x triangular, superficial adducts, stabilizes + elevates thescapula
Rhomboids deep to trapezius (rectangular shaped) medialacts toadduct the scapula
Rotator cuff muscles reinforce shoulder joint/hold head of humerus in glenoidfossa
Subscapularis medial rotation of humerus Infraspinatus lateral rotation of humerus Supraspinatus Teres minor lateral rotation of humerus
Upper limb muscles
Anterior flexion of the shoulder
Pectoralis major prime mover of arm flexion at shoulder, adduction,medial rotation of humerus
Coracobrachialis medial humerussynergist of pec major,adduction/flexion of humerus
Posterior extensors
Latissimus dorsi prime mover for arm extension at shoulder, adduction+ medial rotation of humerus antagonist to pec major
Teres major adducts/medially rotates humerus
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Abductors over the shoulder
Deltoid prime mover of arm abduction at shoulder Supraspinatus assists in abduction (intial 10 degrees)
Muscles that move the elbow
Anterior flexors
Biceps brachiiflexes forearm at elbow, supinates forearm Brachilis deep to biceps brachii, JUST LATERAL Brachioradialis from humerus to distal forearm
Posterior extensors
Triceps brachii 3 heads, prime mover of forearm extension at elbowMuscles that move the wrist
Anterior wrist/digit flexors + pronation of forearm
Palmaris longus inserts into palmar aponeurosis (easily palpated) Flexor carpi radialis just lateral to palmaris longus Flexor carpi ulnaris just medial to palmaris lungusinserts into
palmar aponeurosis
Surrounded by flexor retinaculumPosterior wrist/digit extensors
Extensor carpi radialis longus next to brachioradialis + originates inlateral epicondyle
Extensor carpi ulnarus Extensor digitorum prime mover of digit extension
Lower limb muscles move the leg at the hip
Iliopsoas psoas major + iliacus anterior
Psoas major mainly in abdomen, extends from lumbar vertebrae tolesser trochanter of femur
o Blends with iliacus FLEXES THE HIP
Gluteus maximus - posterior
Largest/most superficial muscle of gluteal region extends the thigh atthe hip, laterally rotates the thigh
Hamstrings posterior
Perform actions at the hip and knee jointo Hip extension (thigh at hip), raising trunk to standing position,
knee flexion
Biceps femoris Semitendinosus - medial Semimembranosus deep to semitendinosus
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Adductors
Medial compartment of thigh (magnus, longus, brevis) Adduct and flex thigh at the hip
Quadriceps femoris anterior compartment
Rectus femoris Vastus lateralis Vastus medialis Vastus intermedius Extend the leg at the knee + rectus femoris flexes thigh at the hip
Satorius
Longest muscle in the body Flexion of the hip and knee, lateral rotation of the thigh (cross-legged)
Muscles that move the foot
Anterior dorsiflexion + toe extension
Tibialis anterior prime mover of dorsiflexion Extensor digitorum longus prime mover of toe extension
Posterior plantarflexion + toe flexion
Gastrocnemius prime mover of plantar flexion at the ankle + flexion ofknee
Soleus deep to gastrocnemius
Flexor digitorum longus deep muscle, flexes toes + plantar flexes foot atthe ankle
KNOW COMPARTMENTS
PHYSIOLOGY OF MUSCLE CONTRACTION
Microscopic anatomy of a skeletal muscle fibre
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Myofibrils
Rod-like 1-2um in diameter Contain contractile elements of skeletal muscle cells sarcomeres
Striations, sarcomeres, myofilaments Dark bands A bands, light bands I bands Each dark band has a lighter region in midsection H zone
o Bisected vertically by dark line M line I bands also have darker region Z disc/line Sarcomere smallest contractile unit of muscle fibre functional skeletal
muscle unit
o Region between two successive Z discsCross-sections
H-zone: thick filaments only I-band: thin filaments only M-line: thick filaments linked by accessory proteins Outer edge of A band thick/thin filaments overlap
Ultrastructure/molecular composition of myofilaments
Thick filaments primarily myosino Head-like structure attaches to actin to form cross-bridge
attachments
o Myosin head site for ATP binding
Thin filaments globular (G) and fibrous (F) actino G binding sites for myosin cross bridgeo Binding site usually covered by tropomyosino Troponin TnI inhibitory subunit that binds to actin, TnT binds to
tropomyosin, TnC binds to Ca2+ (from SR)
o Ca2+ binding to TnC exposes binding sitesSarcoplasmic reticulum/T-tubules
SR
Smooth ER Regulate intracellular levels of Ca2+ Stores Ca2+ and releases it on demand when muscle is contracted
T tubules
Sarcolemma protrudes deep into cell elongated tube formedT tubule
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Generation of AP across sarcolemma
AP arrives at axon terminal at neuromuscular junction ACh released ACh binds to receptors in sarcolemma chemically-gated Na+/K+
channels openpermeabilities change
AP propagates transmission of AP along T tubules changes shape ofproteins, stimulates SR calcium release into cytosol
Myosin heads bind to actin, contraction begins AP: 1-2ms, contraction 20-200ms
Muscle fibre contraction
Ca2+ levels rise ions bind to troponin sites, removes blocking action oftropomyosin (troponin changes shape)
Energised myosin head attaches to actin myofilament, forming a crossbridge
ADP + P released myosin head pivots/bends, changing to bent low-energy shape pulls on actin filament, sliding it toward M line ATP attaches to myosin, link between myosin + actin weakens myosin
head detaches
ATP hydrolyzed to ADP + P, myosin head returns to high-energy position Powered by ATP
Motor unit
Each muscle served by at least one motor nerve Motor unitmotor neuron + all muscle fibres it supplies
Fine control small motor unitso Muscle fibres in single motor unit spread throughout the muscle
weak contraction
Large, weight-bearing muscles (less precise movements) large motorunits
Muscle twitch
Response of a motor unit to single AP of its motor neuron 3 distinctphases
Latent period first few milliseconds following stimulationo Muscle tension beginning to increase but no response seen on
myogramo Ca2+ from SR
Period of contraction active cross bridgeso Sliding filamentso Onset to peak of tension development 10-100mso If tension > resistance, muscle shortens
Period of relaxation 10-100mso Initiated by re-entry of Ca2+ into SRo Muscle tension decreases to 0, tracing returns to baselineo Returns to initial length
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Muscle responses are smooth graded muscle responses via:
Changing the frequency of stimulation Changing the strength of stimulation
Changes in stimulus frequency
Increased muscular force by increased firing rate of motor neuronso Temporal summation
Successive contractions occur before muscle completely relaxes partially contracted already
Maximal tension fused/complete tetanusChanges in stimulus strength
Recruitmento Achieved by delivering shocks of increasing voltage to the muscle
Stimuli producing no observable contractions subthreshold stimulio First observable stimulus threshold stimuluso Beyond this point, muscle contracts more and more vigorously
Maximal stimulus strongest stimulus that produces increasedcontractile force all muscles motor units recruited
Isotonic/isometric contractions
Isotonic
Muscle length changes and moves the loado Once sufficient tension has developed to move the load, tension
remains relatively constant
Thin filaments sliding Concentric and eccentric Concentric muscle shortens e.g. picking up book, more familiar Eccentric muscle lengthens and generates force e.g. walking up stairs
(calf muscle) ~50% more forcefulmicrotears
Isometric
Tension builds but muscle neither shortens nor lengthens Occurs when muscle attempts to move load greater than tension muscle
can develop e.g. lifting piano singlehandedly
Occur when acting to maintain upright posture/hold joints in stationarypositions
Cross bridges generating force but not moving thin filamentsMuscle metabolism
Muscle stores have very little reserves of ATP Direct phosphorylation of ADP by creatine phosphate Anaerobic glycolysis glucose lactic acid Aerobic respiration
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Direct phosphorylation of ADP by creatine phosphate
Creatine phosphate high-energy molecule stored in muscles Muscles store 2-3 times as much CP as ATP Very efficient provide for maximum muscle power for 14-16 seconds
Anaerobic pathway glycolysis + lactic acid formation
As stored ATP/CP are exhausted, more ATP generated by breakdown ofglucose obtained from blood/glycogen stored in the muscle
Initial stage of glucose breakdown glycolysis Glucose2 pyruvate + 2 ATP per molecule Pyruvic acidlactic acid, enough energy for ~60s of exercise
Aerobic pathway
95% of ATP source
Occurs in the mitochondria Indirectly 32ATP per glucose but slow and requires oxygen
Short duration exercise
6 seconds ATP stored in muscles used first 10 seconds ATP from CP and ADP 30-40seconds glycogen stored in muscles broken down to glucose,
oxidized to generate ATP
Prolonged-duration exercise
Aerobic glycolysisMuscle fatigue
Physiological inability to contract even if muscle is still receiving stimuli APs generated K+ lost from muscle cells ATPase pump inefficient so
K+ accumulates in fluids of T tubules
o MP disturbed, Ca2+ not released from SR Potential causes: ATP deficit, accumulation of ADP, lactic acid, ions ACh release impaired, CP reduced, Ca2+ stores reduced, glycogen reduce,
insufficient O2
Oxygen deficit
Amount of oxygen required to restore resting state Oxygen reserves must be replenished Accumulated lactic acidpyruvic acid Glycogen stores replaced ATP/CP reserves resynthesized Liver lactic acid in blood glucose/glycogen Heat major waste product only about 40% of energy released is useful
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Force of muscle contraction affected by:
Number of muscle fibres stimulated Relative size of the fibres Frequency of stimulation Degree of muscle stretch
Number of muscle fibres stimulated
Increased motor units recruited, greater the muscle forceSize of the muscle fibres
Bulkier muscles (greater cross-sectional area), more tension it candevelop greater strength
Frequency of stimulation
Rapid stimulation contractions summed Temporal summation
Degree of muscle stretch
Optimal operating length is length of maximal force generation Ideal length-tension relationship muscle slightly stretched, thin+thick
filaments overlap optimally
Between 80-120% of optimal resting lengthMuscle fibre type
Speed of contraction speed of shortening slow/fast fibreso
Difference in speed refects how fast myosin ATPases split ATP +electrical activity of motor neurons
o Depends how quickly Ca2+ moved from cytosol SR Major pathways for forming ATP
o Mostly reliant on oxygen-using aerobic pathways oxidative fibreso Mostly reliant on anaerobic glycolysis glycolytic fibres
Skeletal muscle cells classified
Slow oxidative (SO) fibres Fast oxidative (FO) fibres Fast glycolytic (FG) fibres
Slow oxidative fibres endurance exercise
Contract slowlyo Because myosin ATPases are slow
Depends on oxygen/aerobic pathways Fatigue resistant/has high endurance typical of aerobic fibres Thin large amount of cytoplasm impedes diffusion of O2/nutrients from
blood
o BECAUSE SLOW Little power because thin so limited number of myofibrils Many mitochondria because aerobic Red abundant supply of myoglobin storing O2 reserves
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Fast glycolytic fibres short intense/powerful movements
Contracts rapidlyo Myosin ATPases fast
Depends on glycogen reserves rather than on blood-delivered nutrients Tires quickly glycogen reserves short-lived, lactic acid accumulates
quickly
Large diameter Few mitochondria, little myoglobin, low capillary dense so white
Fast oxidative fibres
Contract quickly but oxygen dependent, rich supply ofmyoglobin/capillaries
Effect of exercise on muscles
Aerobic
DOES NOT PROMOTE SKELETAL MUSCLE HYPERTROPHY Increased number of capillaries surrounding muscle fibres Increased number of mitochondria within muscle fibres More myoglobin Most dramatic in slow oxidative fibres depending primarily on aerobic
pathways
More efficient muscle metabolism greater endurance, strength,resistance to fatigue
Resistance
Increased individual muscle fibres esp. FG fibresSmooth muscle
Spindle-shaped, uninucleate Most organized into sheets
o GI tract, blood vessels, respiratory/reproductive tract In most cases, two sheets present fibres at right angles to each other
o Longitudinal layer fibres run parallel to long axis of organo Circular fibres run around the circumference
Smooth muscle contraction
No T-tubules SR less developed Actin + myosin interact by sliding filament mechanism Final trigger for contraction rise in intracellular Ca2+ ion level Energised by ATP Ca2+ binds to calmodulin which interacts with myosin kinase and
activates myosin
Electrically coupled by gap junctions Takes 30x longer to contract and relax than skeletal muscle but can
maintain same contractile tension for prolonged periods at less than 1%of the energy cost
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