Anatomy of Skeletal Elements The Musculoskeletal system • 206 bones • grouped into the axial and appendicular skeletons • 650 muscles – approximately 40% of your body weight – also divided into an axial and an appendicular division Classification of Bones • 6 types - based on anatomical classification – Long bones = greater length than width – Short bones = cube-shaped, spongy bone except at surface – Flat bones = two parallel plates of compact bone sandwiching spongy bone layer – Irregular bones = cannot be grouped – Sesamoid bones = develop in tendons where there is considerable friction, tension and stress – Sutural bones = located within joints between cranial bones Bone Markings (surface features) • Used to identify specific elevations, depressions, and openings of bones • Bone markings provide distinct and characteristic landmarks for orientation and identification of bones and associated structures. Bony Processes • Depressions and openings – – – – – Fissure – narrow slit Foramen – hole for nerves, blood vessels Fossa – cuplike depression Sulcus – furrow on a bone surface, contains a nerve or blood vessel Meatus – tubelike opening • Processes – projection or outgrowth on bone for attachment – – – – – – – – – – Condyle – smoothened process at end of bone, forms a joint Facet – smooth flat surface, forms a joint Head – rounded condyle on a neck, forms a joint Crest – prominent ridge or projection, for attachment of connective tissues Epicondyle – projection above a condyle, for attachment of connective tissues Line – long, narrow ridge (less prominent than a crest), for attachment of connective tissues Spinous process – sharp, slender projection, for attachment of connective tissues Trochanter – process of the femur, for attachment of connective tissues Tubercle – process of the humerus, for attachment of connective tissues Tuberosity – roughening on a bone surface, for attachment of connective tissues Skeletal system includes • Axial division – Skull and associated bones • Auditory ossicles • Hyoid bones – Vertebral column – Thoracic cage • Ribs & sternum • Appendicular division -Pectoral girdle -Pelvic girdle THE SKELETAL SYSTEM: AXIAL DIVISION Part A The Axial Skeleton • Axial division – Skull and associated bones • Auditory ossicles • Hyoid bone – Vertebral column – Thoracic cage • Ribs & Sternum The Skull and Associated Bones The Adult Skull • skull = 22 bones • cranium = 8 bones: 1 frontal, 1 occipital, 2 temporals, 2 parietals, 1 sphenoid and 1 ethmoid • facial bones = 14 bones: 2 nasals, 2 maxillae, 2 zygomatics ,1 mandible, 2 lacrimals, 2 palatines, 2 inferior nasal conchae, 1 vomer • mandible and auditory ossicles are the only movable skull bones The Adult Skull • skull is made up of several cavities – 1. cranial cavity – 2. nasal cavity – 3. the orbits – 4. paranasal sinuses • skull contains many holes for the passage of nerves and vessels = foramen/foramina • cranial bones also attach to membranes called meninges • outer surface provides large areas for muscle attachment that move the head or provide facial expressions Sutures • Immovable joints • form boundaries between skull bones • four main sutures – – – – – Coronal Sagittal Lambdoid Squamous PLUS lots of smaller sutures • e.g. Frontonasal • e.g.Temperozygomatic Occipital Bone • part of the base of the skull • surrounds the foramen magnum • forms part of the jugular foramen • hypoglossal foramen found under the occipital condyles Mastoid notch Parietal Bone •Part of the superior and lateral surfaces of the cranium •united by a sagittal suture •connects to frontal bone by coronal suture •connects to occipital bone by lambdoid suture Temporal Bone Petrous portion Tympanic portion •forms wall of jugular foramen •three portions: squamous, petrous and tympanic •petrous part houses tympanic membrane and middle and inner ears •auditory ossicles of middle ear transmit sound to inner ear Temporal Bone Temporal surface of greater wing of sphenoid Frontal process of zygomatic bone Squamous portion Lacrimal bone Petrous portion Tympanic portion Maxillary process of zygomatic bone Articular Tubercle Frontal Bone Supraorbital ridge or margin glabella Internasal suture Frontal process of maxilla Zygomatic process of maxilla – Forms the forehead & roof of the orbit glabella Sphenoid Bone • • • • Contributes to floor of cranium Bridges cranial and facial bones Optic canal allows passage of optic nerve Pterygoid processes sites of muscle attachment Ethmoid Bone • • • • Irregularly shaped bone forms part of orbit & forms roof of nasal cavity Cribriform plate with olfactory foramina for olfactory nerves Perpendicular plate forms part of nasal septum Facial Bones: Maxilla • Paired bone – Largest of the facial bones – Forms upper jaw Facial Bones: Mandible • entire lower jaw • articulates with temporal bone at the Temporomandibular joint • moveable part of skull Facial bones • Nasal bones – Paired bones – Articulate with frontal bone – Extend to superior border of external nares • Vomer Nasal bones – Forms inferior (bottom) portion of nasal septum – Articulates with maxillae and palatine bones Facial bones • Inferior nasal concha – Located on each side of nasal septum – Increase epithelial surface – Create turbulence in inspired air • Zygomatic bone – Temporal process articulates with zygomatic process of temporal bone – Forms zygomatic arch Facial bones •Lacrimal bones –Smallest bones in skull –Delivers tears to nasal cavity via nasolacrimal canal • Palatine bones – Small – L-shaped – Form posterior portion of hard palate – Contribute to floor of orbit The Orbit • Orbital complex – Bony recess that holds the eye – Seven bones • • • • • • • Frontal bone Lacrimal bone Palatine bone Zygomatic bone Ethmoid Sphenoid Maxilla Skull: Inferior View Basilar Portion Condylar fossa Condylar foramen may be present Petrous portion Skull: Interior View Figure 6.4 Sectional Anatomy of the Skull, Part I Tuberculum sellae Cerebral surface of Greater wing of sphenoid Hypophyseal fossa Dorsum sella Lesser wing of sphenoid Foramen Rotundum Sella Turcica Cranial Fossae • Depressions in cranial floor • for the lobes of the brain • Anterior cranial fossa – Frontal bone, ethmoid, lesser wings of sphenoid • Middle cranial fossa – Sphenoid, temporal bones, parietal bones • Posterior cranial fossa – Occipital bone, temporal bones, parietal bones Skull: Sagittal View Skull: Sagittal View The Nasal Complex • Bones and cartilage that enclose the nasal cavity • lined with a nasal mucosa • associated with the 4 paranasal sinuses – hollow airways – lined with mucosa – like nasal mucosa – found in the frontal bones, sphenoid, ethmoid and maxillae The Paranasal Sinuses Infant Skull: The Fontanels • the flat bones in the infant skull are separated by fontanels • fibrous connections between skull bones • permit infant skulls to pass through birth canal • permit the skulls of infants and children to continue growing • will be replaced by sutures in the adult skull The Hyoid Bone • Consists of a body, greater horns and lesser horns • Base for muscles of the tongue and larynx Adult Vertebral Column • strong, flexible rod – average male = 71 cm (28 inches) – average female – 61 cm (24 inches) • capable of moving – – – – anteriorly posteriorly laterally also rotation • supports the head • encloses and protects the spinal cord • allows for the exit of 31 pairs of spinal nerves – through intervertebral foramina Adult Vertebral Column • 26 vertebrae – 24 individual vertebrae – Sacrum – Coccyx • • • • • Seven cervical vertebrae Twelve thoracic vertebrae Five lumbar vertebrae Sacrum – 5 fused vertebrae Coccyx – 4 fused vertebrae Adult Vertebral Column • vertebrae separated by intervertebral discs – discs of fibrocartilage made up of an outer ring and a softer inner region – found between C1 and C2 and all the way down to between L5 and the sacrum – form the joints of the vertebral column Adult Vertebral Column • absorb shock – flatten, broaden and bulge outward • weakening in the outer ring can allow the herniation of the inner material Spinal Curvature • Four curvatures: increase the strength of the column – Thoracic (primary) – forms fetally and retain the curve of the fetus – Sacral (primary) – forms fetally and retain the curve of the fetus – Cervical (secondary) – forms when the baby holds its head erect – Lumbar (secondary) – forms upon walking Vertebrae • Every vertebrae has the following: – 1. body – weight bearing part of the vertebra • separated by the discs – 2. vertebral arch – surrounds the spinal cord • surrounds a hole called a vertebral foramen – 3. processes – seven of them • 1. Spinous (1) – muscle attachment • 2. Transverse (2) – muscle attachment • 3. Superior articular (2) – forms joint with upper vertebra • 4. Inferior articular (2) – forms joint with lower vertebra Vertebrae • cervical vertebrae = transverse foramina in the transverse processes • bifid spinous process • 1st two cervical vertebrae (atlas and axis) look different but have all aspects of a vertebrae Cervical Vertebra Vertebrae Thoracic Vertebrae Lumbar Fused Vertebrae: The sacrum & coccyx • Sacrum - Union of 5 vertebrae (S1 - S5) – completely fused by age 30 – median sacral crest = fused spinous processes – sacral ala = fused transverse processes – sacral canal ends at sacral hiatus • Coccyx = Union of 4 vertebrae (Co1 - Co4) – completely fused by age 30 Rib Cage • 12 pairs of ribs • vertebral end for articulation with the facets of the 12 thoracic vertebrae – both body and the transverse process • sternal end for articulation with the sternum Rib Cage -three kinds of ribs: 1. True – separate & direct connection to the sternum via costal cartilage 2. False – no direct connection to the sternum – joined via a composite piece of costal cartilage 3. Floating – no connection to the sternum Sternum • comprised of the: • 1. Manubrium – with two clavicular notches and a jugular notch • 2. Body – connects to manubrium via a sternal angle • 3. Xiphoid process Sternum & Rib Cage • several muscles and muscle groups either originate from the sternum and/or ribcage (or costal cartilages) or insert onto these structures – sternum: • sternocleidomastoid • sternohyoid & sternothryoid – depresses hyoid bone and larynx – ribcage: • • • • • intercostals – external and internal serratus anterior & posterior numerous muscles of the vertebral column pectoralis major & minor 4 muscles of the abdominal wall THE SKELETAL SYSTEM: APPENDICULAR DIVISION Part A Appendicular Skeleton • Bones of upper and lower limbs • Pectoral and pelvic girdles – Connect limbs to trunk Shoulder Girdle • Includes – Scapula (shoulder blade) – Clavicle (collarbone) • Squares shoulders • Helps move the upper limb • Provides a base for muscle attachment Clavicle • S-shaped bone • Connects manubrium of sternum to the acromion process of scapula • Only direct connection between pectoral girdle and axial skeleton The Scapula • • Medial or vertebral border is the insertion point for the rhomboids, levator scapulae & serratus anterior Two processes attach to ligaments and tendons – – Coracoid process – e.g insertion for pectoralis minor, origin of biceps Acromion process – e.g. origin of the deltoid • • • continues on to become the scapular spine Articulates at the round head of the humerus to form the glenohumoral joint Articulates with clavicle at the acromioclavicular joint Figure 7.5a, b The Scapula The Humerus • articulates with glenoid cavity of scapula • possesses an anatomical neck for capsule attachment and a surgical neck • trochlea and capitulum form joints with the ulna and radius = elbow joint • numerous muscles insert at greater and lesser tubercle – greater tubercle – insertion of 3 rotator cuff muscles + pectoralis major – lesser tubercle – insertion for the other rotator cuff • intertubercular groove – insertion for latissimus dorsi • deltoid tuberosity – insertion of deltoid muscle The Radius and Ulna • Parallel bones of the forearm • radial tuberosity – insertion point for the biceps brachii • Olecranon process of ulna articulates with olecranon fossa of humerus – olecranon process is a major point of muscle attachment for the triceps • Coronoid fossa of humerus accommodates coronoid process of ulna – insertion for the major forearm flexor = brachialis Carpal Bones • 8 wrist bones • Two rows, proximal and distal – scaphoid bone, lunate bone, triquetrum, pisiform – trapezium, trapezoid bone, capitate bone, hamate bone – scaphoid = most commonly injured carpal bone • fall on the outstretched hand – fracture into two separate pieces (tears blood vessels) “Some lovers try positions that they can’t handle” Metacarpal Bones • Articulate with distal carpals • Distally articulate with phalanges – Fingers have three phalanges – Pollex/thumb has two phalanges The Pelvic Girdle • the pelvic girdle consists of the two ossa coxae. • ossum coxa – Ilium – Ischium – Pubis • union between pelvis and sacrum = sacroiliac joint The Pelvic Girdle • Ilium – Largest hip bone – accommodates the head of the femur – Fused to ischium posteriorly – Fused to pubis anteriorly via the superior ramus • Ischium – “sit bones” – ischial spine & tuberosity • ischial tuberosity – site of origin for hamstrings and adductor magnus – lesser sciatic notch – ramus unites with the pubis • Pubis – “pubic bone” – superior & inferior ramus • rami connect to the ilium and ischium • surrounds the obturator foramen – pubic symphysis is pad of fibrocartilage between 2 pubic bones • known as an amphithrotic (slightly movable) joint – inferior pubic ramus for origin of iliacus (hip flexor), gracilis, adductor brevis and magnus (hip adductors) – superior pubic ramus for origin of the hip adductor pectineus – pubic crest/tubercle for origin of adductor longus – – – – – – iliac fossa for origin of iliacus iliac crest for origin of gluteus maximus and medius anterior gluteal line for origin of gluteus medius anterior superior iliac spine for origin of sartorius anterior inferior iliac spine for origin of rectus femoris greater sciatic notch for passage of sciatic nerve Figure 7.12a-c Divisions of the Pelvis Female vs. Male Pelvis • • • • • • Smoother Lighter Less prominent markings Enlarged pelvic outlet Less sacral curvature Wider more circular pelvic inlet • Broader pubic angle The Femur • Longest bone in body – takes 4-5 months to completely replace • Rounded head on an anatomical neck – fits into the acetabulum of the pelvis to form the hip joint • proximal trochanters for muscle attachment • Distal medial and lateral condyles articulate with tibia – to form the knee joint – knee joint is a hinge joint capable of one plane of motion • • Large tendon attachments to the trochanters and the linea aspera Linea aspera – – – • roughened line on the back of the femur origin for the hamstring biceps femoris (short head) & the knee extensor vastus medialis also the insertion point for adductor longus, brevis and magnus Greater and lesser trochanters – greater trochanter – origin of vastus lateralis (knee extensor) & the insertion point for the hip abductors: gluteus medius and minimus and piriformis – lesser trochanter – insertion for iliopsoas (hip flexor) The Patella • Large sesmoid bone - forms within the tendon of the quadriceps femoris. • Forms within tendon of quadriceps femoris muscle group • Patellar ligament attaches to tibial tuberosity The Tibia • Largest bone of leg • Tibial tuberosity – site of insertion for the quadriceps femoris • Anterior margin – known as the “shin bone” • Intercondylar eminence between the condyles – condyles of the tibia form the knee joint with the condyles of the femur • Medial malleolus – Medial support for talocrural joint The Tibia & Fibula The Tarsus • Seven tarsal bones – calcaneus = heel • weight of body transferred through this bone! – talus – forms the ankle joint with the tibia and fibula • ligaments from the two malleolus processes reinforce this joint – navicular – cuboid – 3 cuneiform bones • weight passing through the calcaneus then passes along to 5 metatarsal bones that form 2 arches: -Longitudinal arch -Transverse arch Joints Supportive Connective tissue: Cartilage 1. Cartilage: functions in support, attachment, protection -cells = chondrocytes -matrix = collagen II fibers embedded in a gellike ground-substance -ground substance - water + proteoglycans -proteoglycans – core protein (aggrecan) + sugars (e.g. chondroitin sulfate, glucosamine) -in developing child - model for future bone (endochondral bone formation) -avascular tissue - produces anti-angiogenic chemicals (inhibits growth of blood vessels) -therefore diffusion is the main mode of transport Proteoglycan -3 types: 1) Hyaline - most common - “glass” - ends of bones, within joints (synovial, articular), - end of nose, supports respiratory passages 2. Elastic - flexible cartilage - external ears and parts of larynx 3. Fibrocartilage - very tough -> more collagen fibers - shock absorber e.g. intervertebral discs of the knee Classification of Joints Articulation (A Joint) • • • Wherever two bones interact Function depends on structure can classify according to: A. structure – i.e. what they are made of A. fibrous B. cartilagenous C. synovial B. function - movement – No movement = synarthrotic – Slight movement = amphithrotic – Extensive movement = diathrotic Fibrous Joints •lack a synovial cavity •articulating surfaces are held very closely by fibrous connective tissue •three types: 1. Sutures: composed a thin layer of fibrous connective tissue -unites the bones of the skull e.g. coronal suture -interlocking edges of the suture gives them strength -immovable joint 2. Syndesmoses: greater distance between articular edges -more fibrous connective tissue -connective tissue arranged as a sheet (interosseous membrane) or bundle (ligament) -slightly movable e.g. tibiofibular ligament connecting the tibiofibular joint e.g. interosseous membranes between the radius and ulna, tibia and fibula 3. Gomphoses: cone shaped peg fits into a socket e.g articulations of the roots of the teeth with the jaw -held by the periodontal ligament -immovable Cartilagenous Joints •lacks a synovial cavity •allows little or no movement •articulating bones are connected by hyaline cartilage or fibrocartilage 1. Synchondroses: connecting material is hyaline cartilage e.g. epiphyseal/growth plate of a growing bone -immovable 2. Symphyses: ends of bones are covered with hyaline cartilage but are connected by a flat disc of fibrocartilage -all symphyses occur at the midline of the body e.g. pubic symphysis - connects two ends of the pubis bones e.g. intervertebral joints between the bodies of 2 vertebrae -slightly movable Synovial joints Synovial Joints •presence of a synovial cavity between the articulating bone surfaces •freely movable joints •lined with hyaline cartilage called articular cartilage •filled with a fluid called synovial fluid •surrounded by a fibrous capsule – inside is lined with a synovial membrane •movement is along three possible axes: Monaxial Biaxial Triaxial or Multiaxial Synovial Joints: General Anatomy • Articular/Joint capsule encloses joint cavity – continuous with periosteum of the bones of the joint – lined by a synovial membrane that produces synovial fluid • Synovial fluid = slippery fluid; feeds cartilages • Articular cartilage = hyaline cartilage covering the joint surfaces • Articular discs and menisci – found in the jaw, wrist, sternoclavicular and knee joints – absorbs shock, guides bone movements and distributes forces • Tendon attaches muscle to bone • Ligament attaches bone to bone 9-86 Synovial joints Synovial Joints •synovial joint movement is along three possible axes: Monaxial or uniaxial – e.g. knee joint, elbow joint Biaxial – e.g interphalangeal joint Triaxial or Multiaxial – e.g. shoulder & hip joint Synovial joints Synovial Joints Types •6 subtypes: 1. planar/gliding 2. hinge 3. pivot 4. condyloid 5. saddle 6. ball and socket 1. Planar/Gliding joints : articulating surfaces are flat or slightly curved -permit side to side or back and forth gliding motions -non-axial - no motions around an axis -some books say they are limited monaxial joints e.g. intercarpal joints of the wrist bones e.g. intertarsal joints of the ankle bones 2. Hinge joints: convex surface of one bone fits into a concave surface -produces an angular, open and close movement -movement is in one plane of motion = monaxial 3. Pivot joints: rounded or pointed end of one bone fits into a ring of another -also monaxial -rotates around a longitudinal axis e.g. atlas-axis joint - first 2 vertebrae 4. Condyloid joints: or ellipsoid joints -convex oval shaped projection of one bone fits into the oval-shaped depression of another bone -biaxial = two planes of motion e.g. metacarpals and proximal phalanges e.g. metatarsals and proximal phalanges e.g. atlanto-occipital joint 5. Saddle joints: articular surface of one bone is saddle shaped -modified condyloid joint -biaxial – but more moveable than condyloid joints e.g. thumb metacarpal and trapezium carpal bone = trapeziometacarpal joint 6. Ball and socket joints: ball-like end of one bone fits into a cuplike depression of another -mult-iaxial - several planes of motion e.g. hip joint, shoulder joint Three categories based on range of motion • Synarthroses – Immovable joints • Amphiarthroses – Slightly movable joints • Diarthroses – Freely movable joints Synarthroses • Bony edges may interlock • Sutures – Between skull bones • Gomphosis – Between teeth and jaw • Synchondrosis – Epiphyseal plate • Synostosis – Fused bones Amphiarthroses • Limited movements • Syndesmosis – Collagen fibers connect bones • e.g. tibiofibular joint • Symphysis – Bones are separated by cartilage pad • e.g. pubic symphysis Diarthroses (synovial joints) • • • • • Wide range of movement Bony surfaces covered by articular cartilage Lubricated by synovial fluid Enclosed with joint capsule Accessory structures – – – – – – Menisci Fat pads Ligaments Tendons Bursae Tendon sheaths Joints: Range of Motion • Degrees through which a joint can move • Determined by – structure of the articular surfaces – strength and tautness of ligaments, tendons and capsule • stretching of ligaments increases range of motion • double-jointed people have long or slack ligaments – action of the muscles and tendons • nervous system monitors joint position and muscle tone 9-95 Joints: Range of Motion • Abduction/Adduction • Flexion/Extension/Hyperextension 9-96 Joints: Range of Motion Movements of Head and Trunk • Flexion, hyperextension and lateral flexion of vertebral 9-97 column Special movement terms: Rotation • Movement on longitudinal axis – rotation of trunk, thigh, head or arm • Medial rotation turns the bone inwards • Lateral rotation turns the bone outwards 9-98 Special movements of the hand: Pronation & Supination • Medial and lateral rotation of the hand – called Pronation & Supination Special movements of the hand • Radial and ulnar flexion • Abduction of fingers and thumb • Opposition is movement of the thumb to approach or touch the fingertips • Reposition is movement back to the anatomical position 9-100 Special movement of the foot • Dorsiflexion is raising of the toes as when you swing the foot forward to take a step (heel strike) • Plantarflexion is extension of the foot so that the toes point downward as in standing on tiptoe • Inversion is a movement in which the soles are turned medially • Eversion is a turning of the soles to face laterally Special movement of the Mandible: Protraction & Retraction • Protraction & Retraction of mandible • Lateral excursion = sideways movement • Medial excursion = movement back to the midline – side-to-side grinding during9-102 chewing Representative Articulations The Temporomandibular Joint • TMJ = mandibular fossa of temporal bone & condylar processes of mandible • Thick articular disc between the bones • Supporting structures – – – – Dense capsule Temporomandibular ligament Stylomandibular ligament Sphenomandibular ligament • Loose hinge joint Intervertebral Articulations • Articular processes of adjacent vertebrae • Symphyseal joints at bodies • Ligaments bind vertebrae • Permits flexion, extension, lateral flexion, rotation The Sternoclavicular Joint • Gliding joint • between the sternal end of clavicle and manubruim of sternum •Articular disc •Supports include -Anterior and posterior sternoclavicular ligaments -Interclavicular ligaments -Costoclavicular ligaments The Shoulder Joint • known as the glenohumoral joint – between the glenoid fossa and head of humerus • Loose shallow joint • Greatest range of motion Strength and stability are sacrificed for motion • Supported by ligaments and muscles • Many bursae to decrease friction between ligaments The Elbow Joint • Hinge joint • Flexion and extension • Includes humeroulnar joint and humeroradial joint • Supported by – Radial and ulnar collateral ligaments – Annular ligaments The joints & ligaments of the Wrist • Three joints – Distal radioulnar joint • Pivot diarthrosis • Pronation / supination – Radiocarpal joint • • • • Ellipsoidal articulation Flexion/extension Adduction/ abduction circumduction – Intercarpal joints • Gliding joints Joints of the Hand • Intercarpal joints – Gliding • Carpometacarpal joint of thumb – Saddle • Carpometacarpal joints – Gliding • Metacarpophalangeal joints – Ellipsoidal • Interphalangeal joints – Hinge The Hip Joint • • • • • • Ball and socket diarthrosis Acetabulum of os coxae and head of femur Flexion / extension Adduction / abduction Circumduction Rotation • • • • • Iliofemoral ligament Pubofemoral ligament Ischiofemoral ligament Transverse acetabular ligaments Ligament of femoral head The Knee Joint • Complex hinge joint • Resembles three separate joints – Medial condyles of femur and tibia – Lateral condyles of femur and tibia – Patella and patellar surface of femur • Flexion / extension • Limited rotation • Support is not a single unified capsule – Not a single fluid cavity • • • • Fibrocartilage pads Medial and lateral menisci Fat pads Seven major ligaments bind knee joint – – – – Popliteals Patellar Anterior and posterior cruciates Tibial and fibular collaterals The Joints of the Ankle and Foot • Hinge joint • Inferior surface of tibia, lateral malleolus of fibula, trochlea of talus – Primary joint is tibiotalar • Stabilizing ligaments • Dorsiflexion / plantar flexion • Intertarsal joints – Gliding • Tarsometatarsal joints – Gliding • Metatarsophalangeal – Gliding • Interphanageal – Hinge