Chapter 8 Skeletal System GCU

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

5. 8-5
Surface Features of Bones

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)

11. 8-
Right Temporal Bone

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

16. 8-
Sphenoid Bone
• Sphenoid
sinus

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

40. 8-
Numbered Rib Articulations

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

45. 8-
Scapular Features

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

51. 8-
Sesamoid Bone

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)

63. 8-
Bipedalism and Limb
Adaptations

64. 8-
Bipedalism and Upright
Stance

65. 8-
Bipedalism and Head Position