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Chap08 Skeletal System

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Kevin Perrino DC BCAO CCSP

The document provides an overview of the skeletal system, describing the bones that make up the skull, vertebral column, thoracic cage, upper and lower limbs, and their key features. It discusses the 206 bones in the adult skeleton, their classification into the axial and appendicular skeleton, and surface markings. Specific bones of the skull, vertebral column, thoracic cage, pectoral and pelvic girdles, and upper and lower limbs are then described in detail.

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8-1 Chapter 8 Skeletal System Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
8-2 The Skeletal System • Overview of the skeleton • The skull • The vertebral column and thoracic cage • The pectoral girdle and upper limb • The pelvic girdle and lower limb
8-3 Overview of the Skeleton • Regions of the skeleton – axial skeleton = central axis • skull, vertebral column, ribs, sternum and sacrum – appendicular skeleton = limbs and girdles • Number of bones – 206 in typical adult skeleton • varies with development of sesamoid bones (patella) – start at 270 at birth, decreases with fusion • Surface markings defined in Table 8.2
8-4
8-5 Surface Features of Bones
8-6 The Skull • 22 bones joined together by sutures • Cranial bones surround cranial cavity – 8 bones in contact with meninges • frontal, parietal, – calvaria (skullcap) forms roof and walls • Facial bones support teeth and form nasal cavity and orbit – 14 bones with no direct contact with brain or meninges – attachment of facial and jaw muscles
8-7 Frontal Bone • Forms forehead and part of the roof of the cranium • Forms roof of the orbit • Contains frontal sinus
8-8 Parietal Bone • Cranial roof and part of its lateral walls • Bordered by 4 sutures – coronal, sagittal, lambdoid and squamous • Temporal lines of temporalis muscle Temporal lines
8-9 Temporal Bone • Lateral wall and part of floor of cranial cavity – squamous part • zygomatic process • mandibular fossa and TMJ – tympanic part • external auditory meatus • styloid process – mastoid part • mastoid process – mastoiditis from ear infection • mastoid notch – digastric muscle
8- Petrous Portion of Temporal Bone • Part of cranial floor – separates middle from posterior cranial fossa • Houses middle and inner ear cavities – receptors for hearing and sense of balance – internal auditory meatus = opening for CN VII (vestibulocochlear nerve)
8- Right Temporal Bone
8- Openings in Temporal Bone • Carotid canal – passage for internal carotid artery supplying the brain • Jugular foramen – irregular opening between temporal and occipital bones – passageway for drainage of blood from brain to internal jugular vein
8- Occipital Bone • Rear and base of skull • Foramen magnum holds spinal cord • Skull rests on atlas at occipital condyles • Hypoglossal canal transmits hypoglossal nerve (CN XII) supplying tongue muscles • External occipital protuberance for nuchal ligament • Nuchal lines mark neck muscles
8- Sphenoid Bone • Lesser wing • Greater wing • Body of sphenoid • Medial and lateral pterygoid processes
8- Sphenoid Bone • Body of the sphenoid – sella turcica contains hypophyseal fossa – houses pituitary gland • Lesser wing – optic foramen • Greater wing – foramen rotundum and ovale for brs. trigeminal nerve – foramen spinosum for meningeal artery
8- Sphenoid Bone • Sphenoid sinus
8- Ethmoid Bone • Between the orbital cavities • Lateral walls and roof nasal cavity • Cribriform plate and crista galli • Ethmoid air cells form ethmoid sinus • Perpendicular plate forms part of nasal septum • Concha (turbinates) on lateral wall
8- Maxillary Bones • Forms upper jaw – alveolar processes are bony points between teeth – alveolar sockets hold teeth • Forms inferomedial wall of orbit – infraorbital foramen • Forms anterior 2/3’s of hard palate – incisive foramen – cleft palate
8- Locations of Paranasal Sinuses • Maxillary sinus fills maxillae bone • Other bones containing sinuses are frontal, ethmoid and sphenoid.
8- Zygomatic Bones • Forms angles of the cheekbones and part of lateral orbital wall • Zygomatic arch is formed from temporal process of zygomatic bone and zygomatic process of temporal bone
8- Lacrimal Bones • Form part of medial wall of each orbit • Lacrimal fossa houses lacrimal sac in life – tears collect in lacrimal sac and drain into nasal cavity
8- Nasal Bones • Forms bridge of nose and supports cartilages of nose • Often fractured by blow to the nose
8- Vomer • Inferior half of the nasal septum • Supports cartilage of nasal septum
8- • Only movable bone – jaw joint between mandibular fossa and condyloid process • Holds the lower teeth • Attachment of muscles of mastication – temporalis muscle onto coronoid process – masseter muscle onto angle of mandible • Mandibular foramen • Mental foramen Mandible
8- The Vertebral Column • 33 vertebrae and intervertebral discs of fibrocartilage • Five vertebral groups – 7 cervical in the neck – 12 thoracic in the chest – 5 lumbar in lower back – 5 fused sacral – 4 fused coccygeal • Variations in number of lumbar and sacral vertebrae
8- Newborn Spinal Curvature • Spine exhibits one continuous C- shaped curve • Known as primary curvature
8- Adult Spinal Curvatures • S-shaped vertebral column with 4 curvatures • Secondary curvatures develop after birth – lifting head as it begins to crawl develops cervical curvature – walking upright develops lumbar curvature
8- General Structure of Vertebra • Body • Vertebral foramen form vertebral canal • Neural arch – 2 lamina – 2 pedicles • Processes – spinous, transverse and articular
8- Intervertebral Foramen and Discs • Intervertebral foramen – Notches between adjacent vertebrae – passageway for nerves • Intervertebral discs – bind vertebrae together – absorb shock – gelatinous nucleus pulposus surrounded by anulus fibrosus (ring of fibrocartilage) – herniated disc pressures spinal nerve or cord
8- Typical Cervical Vertebrae • Small body and larger vertebral foramen • Transverse process short with transverse foramen for protection of vertebral arteries • Bifid or forked spinous process in C2 to C6 • C7 vertebra prominens
8- The Unique Atlas and Axis • Atlas (C1) supports the skull – concave superior articular facet • nod your head in “yes” movement – ring surrounding large vertebral foramen • anterior and posterior arch • no vertebral body • Axis (C2) – dens or odontoid process is held in place inside the vertebral foramen of the atlas by ligaments – allows rotation of head -- “no”
8- Atlas and Axis Articulation
8- Typical Thoracic Vertebrae • Larger body than cervical but smaller than lumbar • Spinous processes pointed and angled downward • Superior articular facets face posteriorly permitting some rotation between adjacent vertebrae • Rib attachment – costal facets on vertebral body and at ends of transverse processes for articulation of ribs
8- Lumbar Vertebrae • Thick, stout body and blunt, squarish spinous process • Superior articular processes face medially – lumbar region resistant to twisting movements
8- Sacrum (Anterior View) • 5 sacral vertebrae fuse by age 26 • Anterior surface – smooth and concave – sacral foramina were intervertebral foramen • nerves and blood vessels – 4 transverse lines indicate line of fusion of vertebrae
8- Sacrum (Posterior View) • Median sacral crest • Lateral sacral crest • Posterior sacral foramina • Sacral canal ends as sacral hiatus • Auricular surface is part of sacroiliac joint
8- Coccyx • Single, small bone – 4 vertebrae fused by 30 – Co1 to Co4 • Attachment site for muscles of pelvic floor • Cornua – hornlike projections on Co1 for ligaments attach coccyx to sacrum • Fractured by fall or during childbirth
8- Thoracic Cage • Consists of thoracic vertebrae, sternum and ribs • Attachment site for pectoral girdle and many limb muscles • Protects many organs • Rhythmically expanded by respiratory muscles to draw air into the lungs
8- Rib Structure • Flat blade called a shaft – inferior margin has costal groove for nerves and vessels • Proximal head and tubercle are connected by neck • Articulation – head with body of vertebrae – tubercle with transverse process Tubercle Head
8- Numbered Rib Articulations
8- True and False Ribs • True ribs (1 to 7) attach to sternum with hyaline cartilage • False ribs (8-12) – 11-12 are floating and not attached to sternum • 12 pairs of ribs in both sexes
8- Pectoral Girdle • Attaches upper extremity to the body • Scapula and clavicle • Clavicle attaches medially to the sternum and laterally to the scapula – sternoclavicular joint – acromioclavicular joint • Scapula articulates with the humerus – humeroscapular or shoulder joint – easily dislocated due to loose attachment
8- Clavicle • S-shaped bone, flattened dorsoventrally • Inferior - marked by muscle and ligament • Sternal end rounded -- acromial end flattened
8- Scapula • Triangular plate overlies ribs 2 to 7 • Spine ends as acromion process • Coracoid process = muscle attachment • Subscapular, infraspinous and supraspinous fossa • Glenoid fossa = socket for head of humerus
8- Scapular Features
8- Upper Limb • 30 bones per limb • Brachium (arm) = humerus • Antebrachium (forearm) = radius and ulna (radius on thumb side) • Carpus (wrist) = 8 small bones(2 rows) • Manus (hand) = 19 bones(2 groups) – 5 metacarpals in palm – 14 phalanges in fingers
8- Humerus • Hemispherical head • Anatomical neck • Greater and lesser tubercles and deltoid tuberosity • Intertubercular groove holds biceps tendon • Rounded capitulum articulates with radius • Trochlea articulates with ulna • Olecranon fossa holds olecranon process of ulna • Forearm muscles attach to medial and lateral epicondyles
8- Ulna and Radius • Radius – head = disc rotates during pronation and supination • articulates with capitulum – radial tuberosity for biceps muscle • Ulna – olecranon and trochlear notch – radial notch holds ulna • Interosseous membrane – ligament attaches radius to ulna along interosseous margin of each bone
8- Carpal Bones • Form wrist – flexion, extension, abduction and adduction • 2 rows (4 bones each) – proximal row = scaphoid, lunate, triquetrum and pisiform – distal row = trapezium, trapezoid, capitate and hamate
8- Metacarpals and Phalanges • Phalanges are bones of the fingers – thumb or pollex has proximal and distal phalanx – fingers have proximal, middle and distal phalanx • Metacarpals are bones of the palm – base, shaft and head
8- Sesamoid Bone
8- Pelvic Girdle • Girdle = 2 hip bones • Pelvis = girdle and sacrum • Supports trunk on the legs and protects viscera • Each os coxae is joined to the vertebral column at the sacroiliac joint • Anteriorly, pubic bones are joined by pad of fibrocartilage to form pubic symphysis
8- Pelvic Inlet and Outlet • False and true pelvis separated at pelvic brim • Infant’s head passes through pelvic inlet and outlet
8- Os Coxae (Hip Bone) • Acetabulum is hip joint socket • Ilium – iliac crest and iliac fossa – greater sciatic notch contains sciatic nerve • Pubis – body, superior and inferior ramus • Ischium – ischial tuberosity bears body weight – ischial spine – lesser sciatic notch between ischial spine and tuberosity – ischial ramus joins inferior pubic ramus
8- Comparison of Male and Female • Female lighter, shallower pubic arch( >100 degrees), and pubic inlet round or oval • Male heavier, upper pelvis nearly vertical, coccyx more vertical, and pelvic inlet heart-shaped
8- Femur and Patella (Kneecap) • Nearly spherical head and constricted neck – ligament to fovea capitis • Greater and lesser trochanters for muscle attachment • Posterior ridge called linea aspera • Medial and lateral condyles and epicondyles found distally • Patella = triangular sesamoid
8- Tibia • Tibia is thick, weight- bearing bone (medial) • Broad superior head with 2 flat articular surfaces • medial and lateral condyles – roughened anterior surface palpated below patella (tibial tuberosity) – distal expansion = medial malleolus
8- Fibula • Slender lateral strut stabilizes ankle • Does not bear any body weight – spare bone tissue • Head = proximal end • Lateral malleolus = distal expansion • Joined to tibia by interosseous membrane
8- The Ankle and Foot • Tarsal bones are shaped and arranged differently from carpal bones due to load-bearing role of the ankle • Talus is most superior tarsal bone – forms ankle joint with tibia and fibula – sits upon calcaneus and articulates with navicular • Calcaneus forms heel (achilles tendon) • Distal row of tarsal bones – cuboid, medial, intermediate and lateral cuneiforms
8- The Foot • Remaining bones of foot are similar in name and arrangement to the hand • Metatarsal I is proximal to the great toe (hallux) – base, shaft and head • Phalanges – 2 in great toe • proximal and distal – 3 in all other toes • proximal, middle and distal
8- Embryonic Limb Rotation • Rotation of upper and lower limbs in opposite directions – largest digit medial in foot and lateral in hand – Elbow flexes posteriorly and knee flexes anteriorly
8- Foot Arches • Sole of foot not flat on ground • 3 springy arches absorb stress – medial longitudinal arch from heel to hallux – lateral longitudinal arch from heel to little toe – transverse arch across middle of foot • Arches held together by short, strong ligaments – pes planis (flat feet)
8- Bipedalism and Limb Adaptations
8- Bipedalism and Upright Stance
8- Bipedalism and Head Position

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Chap08 Skeletal System

  • 1. 8-1 Chapter 8 Skeletal System Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
  • 2. 8-2 The Skeletal System • Overview of the skeleton • The skull • The vertebral column and thoracic cage • The pectoral girdle and upper limb • The pelvic girdle and lower limb
  • 3. 8-3 Overview of the Skeleton • Regions of the skeleton – axial skeleton = central axis • skull, vertebral column, ribs, sternum and sacrum – appendicular skeleton = limbs and girdles • Number of bones – 206 in typical adult skeleton • varies with development of sesamoid bones (patella) – start at 270 at birth, decreases with fusion • Surface markings defined in Table 8.2
  • 4. 8-4
  • 6. 8-6 The Skull • 22 bones joined together by sutures • Cranial bones surround cranial cavity – 8 bones in contact with meninges • frontal, parietal, – calvaria (skullcap) forms roof and walls • Facial bones support teeth and form nasal cavity and orbit – 14 bones with no direct contact with brain or meninges – attachment of facial and jaw muscles
  • 7. 8-7 Frontal Bone • Forms forehead and part of the roof of the cranium • Forms roof of the orbit • Contains frontal sinus
  • 8. 8-8 Parietal Bone • Cranial roof and part of its lateral walls • Bordered by 4 sutures – coronal, sagittal, lambdoid and squamous • Temporal lines of temporalis muscle Temporal lines
  • 9. 8-9 Temporal Bone • Lateral wall and part of floor of cranial cavity – squamous part • zygomatic process • mandibular fossa and TMJ – tympanic part • external auditory meatus • styloid process – mastoid part • mastoid process – mastoiditis from ear infection • mastoid notch – digastric muscle
  • 10. 8- Petrous Portion of Temporal Bone • Part of cranial floor – separates middle from posterior cranial fossa • Houses middle and inner ear cavities – receptors for hearing and sense of balance – internal auditory meatus = opening for CN VII (vestibulocochlear nerve)
  • 12. 8- Openings in Temporal Bone • Carotid canal – passage for internal carotid artery supplying the brain • Jugular foramen – irregular opening between temporal and occipital bones – passageway for drainage of blood from brain to internal jugular vein
  • 13. 8- Occipital Bone • Rear and base of skull • Foramen magnum holds spinal cord • Skull rests on atlas at occipital condyles • Hypoglossal canal transmits hypoglossal nerve (CN XII) supplying tongue muscles • External occipital protuberance for nuchal ligament • Nuchal lines mark neck muscles
  • 14. 8- Sphenoid Bone • Lesser wing • Greater wing • Body of sphenoid • Medial and lateral pterygoid processes
  • 15. 8- Sphenoid Bone • Body of the sphenoid – sella turcica contains hypophyseal fossa – houses pituitary gland • Lesser wing – optic foramen • Greater wing – foramen rotundum and ovale for brs. trigeminal nerve – foramen spinosum for meningeal artery
  • 17. 8- Ethmoid Bone • Between the orbital cavities • Lateral walls and roof nasal cavity • Cribriform plate and crista galli • Ethmoid air cells form ethmoid sinus • Perpendicular plate forms part of nasal septum • Concha (turbinates) on lateral wall
  • 18. 8- Maxillary Bones • Forms upper jaw – alveolar processes are bony points between teeth – alveolar sockets hold teeth • Forms inferomedial wall of orbit – infraorbital foramen • Forms anterior 2/3’s of hard palate – incisive foramen – cleft palate
  • 19. 8- Locations of Paranasal Sinuses • Maxillary sinus fills maxillae bone • Other bones containing sinuses are frontal, ethmoid and sphenoid.
  • 20. 8- Zygomatic Bones • Forms angles of the cheekbones and part of lateral orbital wall • Zygomatic arch is formed from temporal process of zygomatic bone and zygomatic process of temporal bone
  • 21. 8- Lacrimal Bones • Form part of medial wall of each orbit • Lacrimal fossa houses lacrimal sac in life – tears collect in lacrimal sac and drain into nasal cavity
  • 22. 8- Nasal Bones • Forms bridge of nose and supports cartilages of nose • Often fractured by blow to the nose
  • 23. 8- Vomer • Inferior half of the nasal septum • Supports cartilage of nasal septum
  • 24. 8- • Only movable bone – jaw joint between mandibular fossa and condyloid process • Holds the lower teeth • Attachment of muscles of mastication – temporalis muscle onto coronoid process – masseter muscle onto angle of mandible • Mandibular foramen • Mental foramen Mandible
  • 25. 8- The Vertebral Column • 33 vertebrae and intervertebral discs of fibrocartilage • Five vertebral groups – 7 cervical in the neck – 12 thoracic in the chest – 5 lumbar in lower back – 5 fused sacral – 4 fused coccygeal • Variations in number of lumbar and sacral vertebrae
  • 26. 8- Newborn Spinal Curvature • Spine exhibits one continuous C- shaped curve • Known as primary curvature
  • 27. 8- Adult Spinal Curvatures • S-shaped vertebral column with 4 curvatures • Secondary curvatures develop after birth – lifting head as it begins to crawl develops cervical curvature – walking upright develops lumbar curvature
  • 28. 8- General Structure of Vertebra • Body • Vertebral foramen form vertebral canal • Neural arch – 2 lamina – 2 pedicles • Processes – spinous, transverse and articular
  • 29. 8- Intervertebral Foramen and Discs • Intervertebral foramen – Notches between adjacent vertebrae – passageway for nerves • Intervertebral discs – bind vertebrae together – absorb shock – gelatinous nucleus pulposus surrounded by anulus fibrosus (ring of fibrocartilage) – herniated disc pressures spinal nerve or cord
  • 30. 8- Typical Cervical Vertebrae • Small body and larger vertebral foramen • Transverse process short with transverse foramen for protection of vertebral arteries • Bifid or forked spinous process in C2 to C6 • C7 vertebra prominens
  • 31. 8- The Unique Atlas and Axis • Atlas (C1) supports the skull – concave superior articular facet • nod your head in “yes” movement – ring surrounding large vertebral foramen • anterior and posterior arch • no vertebral body • Axis (C2) – dens or odontoid process is held in place inside the vertebral foramen of the atlas by ligaments – allows rotation of head -- “no”
  • 32. 8- Atlas and Axis Articulation
  • 33. 8- Typical Thoracic Vertebrae • Larger body than cervical but smaller than lumbar • Spinous processes pointed and angled downward • Superior articular facets face posteriorly permitting some rotation between adjacent vertebrae • Rib attachment – costal facets on vertebral body and at ends of transverse processes for articulation of ribs
  • 34. 8- Lumbar Vertebrae • Thick, stout body and blunt, squarish spinous process • Superior articular processes face medially – lumbar region resistant to twisting movements
  • 35. 8- Sacrum (Anterior View) • 5 sacral vertebrae fuse by age 26 • Anterior surface – smooth and concave – sacral foramina were intervertebral foramen • nerves and blood vessels – 4 transverse lines indicate line of fusion of vertebrae
  • 36. 8- Sacrum (Posterior View) • Median sacral crest • Lateral sacral crest • Posterior sacral foramina • Sacral canal ends as sacral hiatus • Auricular surface is part of sacroiliac joint
  • 37. 8- Coccyx • Single, small bone – 4 vertebrae fused by 30 – Co1 to Co4 • Attachment site for muscles of pelvic floor • Cornua – hornlike projections on Co1 for ligaments attach coccyx to sacrum • Fractured by fall or during childbirth
  • 38. 8- Thoracic Cage • Consists of thoracic vertebrae, sternum and ribs • Attachment site for pectoral girdle and many limb muscles • Protects many organs • Rhythmically expanded by respiratory muscles to draw air into the lungs
  • 39. 8- Rib Structure • Flat blade called a shaft – inferior margin has costal groove for nerves and vessels • Proximal head and tubercle are connected by neck • Articulation – head with body of vertebrae – tubercle with transverse process Tubercle Head
  • 41. 8- True and False Ribs • True ribs (1 to 7) attach to sternum with hyaline cartilage • False ribs (8-12) – 11-12 are floating and not attached to sternum • 12 pairs of ribs in both sexes
  • 42. 8- Pectoral Girdle • Attaches upper extremity to the body • Scapula and clavicle • Clavicle attaches medially to the sternum and laterally to the scapula – sternoclavicular joint – acromioclavicular joint • Scapula articulates with the humerus – humeroscapular or shoulder joint – easily dislocated due to loose attachment
  • 43. 8- Clavicle • S-shaped bone, flattened dorsoventrally • Inferior - marked by muscle and ligament • Sternal end rounded -- acromial end flattened
  • 44. 8- Scapula • Triangular plate overlies ribs 2 to 7 • Spine ends as acromion process • Coracoid process = muscle attachment • Subscapular, infraspinous and supraspinous fossa • Glenoid fossa = socket for head of humerus
  • 46. 8- Upper Limb • 30 bones per limb • Brachium (arm) = humerus • Antebrachium (forearm) = radius and ulna (radius on thumb side) • Carpus (wrist) = 8 small bones(2 rows) • Manus (hand) = 19 bones(2 groups) – 5 metacarpals in palm – 14 phalanges in fingers
  • 47. 8- Humerus • Hemispherical head • Anatomical neck • Greater and lesser tubercles and deltoid tuberosity • Intertubercular groove holds biceps tendon • Rounded capitulum articulates with radius • Trochlea articulates with ulna • Olecranon fossa holds olecranon process of ulna • Forearm muscles attach to medial and lateral epicondyles
  • 48. 8- Ulna and Radius • Radius – head = disc rotates during pronation and supination • articulates with capitulum – radial tuberosity for biceps muscle • Ulna – olecranon and trochlear notch – radial notch holds ulna • Interosseous membrane – ligament attaches radius to ulna along interosseous margin of each bone
  • 49. 8- Carpal Bones • Form wrist – flexion, extension, abduction and adduction • 2 rows (4 bones each) – proximal row = scaphoid, lunate, triquetrum and pisiform – distal row = trapezium, trapezoid, capitate and hamate
  • 50. 8- Metacarpals and Phalanges • Phalanges are bones of the fingers – thumb or pollex has proximal and distal phalanx – fingers have proximal, middle and distal phalanx • Metacarpals are bones of the palm – base, shaft and head
  • 52. 8- Pelvic Girdle • Girdle = 2 hip bones • Pelvis = girdle and sacrum • Supports trunk on the legs and protects viscera • Each os coxae is joined to the vertebral column at the sacroiliac joint • Anteriorly, pubic bones are joined by pad of fibrocartilage to form pubic symphysis
  • 53. 8- Pelvic Inlet and Outlet • False and true pelvis separated at pelvic brim • Infant’s head passes through pelvic inlet and outlet
  • 54. 8- Os Coxae (Hip Bone) • Acetabulum is hip joint socket • Ilium – iliac crest and iliac fossa – greater sciatic notch contains sciatic nerve • Pubis – body, superior and inferior ramus • Ischium – ischial tuberosity bears body weight – ischial spine – lesser sciatic notch between ischial spine and tuberosity – ischial ramus joins inferior pubic ramus
  • 55. 8- Comparison of Male and Female • Female lighter, shallower pubic arch( >100 degrees), and pubic inlet round or oval • Male heavier, upper pelvis nearly vertical, coccyx more vertical, and pelvic inlet heart-shaped
  • 56. 8- Femur and Patella (Kneecap) • Nearly spherical head and constricted neck – ligament to fovea capitis • Greater and lesser trochanters for muscle attachment • Posterior ridge called linea aspera • Medial and lateral condyles and epicondyles found distally • Patella = triangular sesamoid
  • 57. 8- Tibia • Tibia is thick, weight- bearing bone (medial) • Broad superior head with 2 flat articular surfaces • medial and lateral condyles – roughened anterior surface palpated below patella (tibial tuberosity) – distal expansion = medial malleolus
  • 58. 8- Fibula • Slender lateral strut stabilizes ankle • Does not bear any body weight – spare bone tissue • Head = proximal end • Lateral malleolus = distal expansion • Joined to tibia by interosseous membrane
  • 59. 8- The Ankle and Foot • Tarsal bones are shaped and arranged differently from carpal bones due to load-bearing role of the ankle • Talus is most superior tarsal bone – forms ankle joint with tibia and fibula – sits upon calcaneus and articulates with navicular • Calcaneus forms heel (achilles tendon) • Distal row of tarsal bones – cuboid, medial, intermediate and lateral cuneiforms
  • 60. 8- The Foot • Remaining bones of foot are similar in name and arrangement to the hand • Metatarsal I is proximal to the great toe (hallux) – base, shaft and head • Phalanges – 2 in great toe • proximal and distal – 3 in all other toes • proximal, middle and distal
  • 61. 8- Embryonic Limb Rotation • Rotation of upper and lower limbs in opposite directions – largest digit medial in foot and lateral in hand – Elbow flexes posteriorly and knee flexes anteriorly
  • 62. 8- Foot Arches • Sole of foot not flat on ground • 3 springy arches absorb stress – medial longitudinal arch from heel to hallux – lateral longitudinal arch from heel to little toe – transverse arch across middle of foot • Arches held together by short, strong ligaments – pes planis (flat feet)