Human anatomy notes on skeletal system specifically axial skeleton

1. The Skeletal System
Axial Osteology

2. The Axial Skeleton
• Functions as a framework - supports and protects
organs in the dorsal and ventral body cavities
• Contains the special sense organs for taste, smell,
hearing, balance, and vision
• Attachment sites for muscles that
- adjust the posture of the head, neck, and trunk
- move the thoracic cage for respiration
- stabilize the appendicular skeleton
• Joints of the axial skeleton are very strong
- reinforced with ligaments and allow limited movement
• Contain red marrow for blood cell production
- portions of the vertebrae, sternum, and ribs

4. The Cranium
• The skull contains 22 bones: 8 form the cranium or
‘braincase’ and 14 are associated with the face
• The cranium surrounds and protects the brains:
- occipital, 2 parietal, frontal, 2 temporal, sphenoid, ethmoid
- occipital, parietal, frontal bones form the calvaria ‘skullcap’
- encloses the cranial cavity a fluid-filled chamber
- BVs, nerves, and membranes attached to the inner surface
stabilize position of the brain
- outer surface provides an extensive area for attachment of
muscles that move the eyes, jaws, and head

5. Cranial and Facial Subdivisions of the Skull
Fig 6.2

6. The Adult Skull
Fig 6.3a

7. Fig 6.3b

8. Fig 6.3d

9. Sutures
• Immovable joints at the boundaries between
skull bones
- bones firmly joined together with dense fibrous CT
• 5 major sutures: lamboid, sagittal, coronal,
squamous, and frontonasal

10. Fig 6.3c

11. The Adult Skull (Lateral View)

12. Fig 6.3d
The Adult Skull (Anterior View)

13. Sectional Anatomy of the Skull
Fig 6.4

14. Sectional Anatomy of the Skull
Fig 6.4

15. The Occipital Bone
• Contributes to the posterior, lateral, inferior cranium
• Foramen magnum connects the cranial cavity with the
spinal cavity enclosed by the vertebral column
• Bone markings:
- occipital condyles allows the skull to articulate with the first
cervical vertebra (the atlas)
- external occipital crest, external occipital protuberance,
inferior and superior nuchal lines (mark attachment of
muscles and ligments that stabilize articulation between the
atlas and the skull), jugular foramen (internal jugular vein),
hypoglossal canals (hypoglossal nerves control tongue muscle
• Internal grooves follow the path of BVs and the ridges
mark the attachment site of the meninges

16. The Occipital Bone
Fig 6.6a

17. The Occipital Bone
Fig 6.6b

18. The Adult Skull (Inferior View)

19. The Adult Skull (Inferior View)
Fig 6.3e

20. The Parietal Bones
• Contribute to the superior and lateral surfaces of
the cranium and form the major part of the calvaria
• Bone markings:
- the superior and inferior temporal lines mark the
attachment of the temporalis muscle (closes the mouth)
- parietal eminence, the smooth surface superior to the
temporal lines

21. The Parietal Bones
Fig 6.6

22. The Frontal Bone
• Forms the forehead and roof of the orbits
• The convex anterior surface is called the squamous
part, or forehead, ends at the supra-orbital margins
- thickened ridges or superciliary arches support the eyebrows
- supra-orbital foramen or notch
• Orbital part forms the roof of each orbit
- inferior surface or orbital surface contains openings for BVs
and nerves
- lacrimal fossa location of the lacrimal gland
• Interior surface bears the frontal crest that marks the
attachment of membranes to prevent tissue contact

23. Fig 6.7a
Frontal (metopic) suture – during development bones form
through fusion of separate centers of ossification, and at birth the
fusions are not complete

24. The Frontal Bone
Fig 6.7b

25. The Frontal Bone

26. Temporal Bone
• Contribute to the cranial lateral and inferior walls
- contribute to the zygomatic arches
- form the only articulations with the mandible and articulate
with the zygomatic, parietal, occipital bones, and sphenoid
- protect the sense organs of the inner ear
- inferior convex surfaces form an extensive area for muscle
attachments that close the jaw and move the head
• Bone markings:
- zygomatic and temporal process form the zygomatic arch
- mandibular fossa and articular tubercle (mandible)
- tympanic part surrounds entrance to the external
acoustic meatus (external auditory canal) which ends at
the tympanic membrane (eardrum)

27. Temporal Bone Markings
• Petrous part surrounds and protects the sense
organs of hearing and balance
• Mastoid process - attachment site for muscles that
rotate or extend the head
- mastoid air cells (sinuses) within the mastoid process
- mastoid foramen near the base of the mastoid for BVs that
supply the membranes surrounding the brain
• Styloid process - attachment site for ligaments that
support the hyoid bone and muscles of the tongue,
pharynx, and larynx
- the facial nerve passes through the stylomastoid foramen

28. Temporal Bone Markings
• The carotid canal – passageway for the internal
carotid artery that supplies blood to the brain
• Foramen lacerum – contains hyaline cartilage and
small arteries
• Musculotubal canal surrounds the auditory (or
Eustachian or pharyngotympanic) tube
- begins at the pharynx and ends at the tympanic cavity or
middle ear (contains the auditory ossicles)
• Internal acoustic meatus carries BVs and nerves to
the inner ear and the facial nerve to the stylomastoid
foramen

29. The Temporal Bone
Fig 6.8a,b

30. Fig 6.8c

31. Fig 6.8

32. The Sphenoid (Sphenoidal Bone)
• Articulates with every other cranial bone
- acts as a bridge uniting the cranial and facial bones
- articulates with the palatine, zygomatic, maxillae, and
vomer of the facial bone complex
- also acts as a brace strengthening the sides of the skull
• General shape compared to a bat or butterfly
- greater and lesser wings
- hypophysial fossa between the wings cradles the
pituitary gland below the brain and the bony enclosure is
called the sella turcica

33. The Sphenoidal Bone Markings
• Superior orbital fissure – passageway for BVs and
cranial nerves of the eye
• Optic groove – the transverse groove that crosses
the sella turcica above the seat level
- at either end is the optic canal, a passageway for the
optic nerves
• On either side of the sella turcica are the
rotundum, ovale, and the spinosum foramina
- carry BVs and cranial nerves to the orbit, face, and jaws
• Pterygoid processes form a pair of plates
- attachment sites for muscles that move the lower jaw and
soft palate
- pterygoid canal provides a route for a small nerve and an
artery that supply the soft palate and adjacent structures

34. The Sphenoid
Fig 6.9a

35. Fig 6.9b

36. The Ethmoid (Ethmoidal Bone)
• Irregular shaped bone that forms part of the orbital
wall, the anteromedial cranium floor, roof of the nasal
cavity, and part of the nasal septum
• Cribriform plate - perforated by cribriform foramina (openings
for the olfactory nerves)
- the falx cerebri (a membrane that stabilizes the position of the
brain) attaches to a prominent ridge called the crista galli
• Ethmoidal labyrinth an interconnected network of
ethmoidal air cells that open into the nasal cavity
- mucous secretions flush the surfaces of the nasal cavities
- superior and middle nasal conchae slows the airflow to warm,
humidify, and remove dust
- perpendicular plate forms part of the nasal septum

37. The Ethmoid
Fig 6.10

38. The Cranial Fossae
Cranial fossa – curving depression of the cranial floor
• Anterior cranial fossa formed by:
- the frontal bone, the ethmoid, the lesser wing of the sphenoid;
cradles the frontal lobes of the cerebral hemispheres
• Middle cranial fossa is formed by:
- the sphenoid, temporal, parietal bones; cradles the temporal
lobes of the cerebral hemispheres, the diencephalon, and
mesencephalon
• Posterior cranial fossa is formed primarily by:
- the occipital bone, with contributions from the temporal and
parietal bones
- suports the occipital lobes of the crebral hemispheres, the
crebellum, and the pons and medulla oblongata (brain stem)

39. The Cranial Fossae
Fig 6.11a

40. The Cranial Fossae
Fig 6.11b

41. Bones of the Face
• There are 14 facial bones
• Paired bones include the maxillae, palatine, nasal,
zygomatic, lacrimal, and inferior nasal conchae
• Single bones include the vomer and mandible
• Protect and support the entrances to the digestive
and respiratory tracts
• The superficial facial bones provide areas for
attachment of muscles, control facial expressions
and assist in food manipulation

42. The Maxillae
• The largest facial bones – form the upper jaw
- articulates with all facial bones except the mandible
• Orbital surface provides protection for the eye
• Frontal processes articulate with the frontal bone
of the cranium and with a nasal bone
• Alveolar margin or processes contain the upper
teeth
• The infra-orbital foramen passageway for a major
sensory facial nerve
- runs along the infra-orbital groove passes through the
inferior orbital fissure and the foramen rotundum to reach
the brain stem

43. The Maxillae
• Maxillary sinuses are the largest sinuses in the skull
- lighten the portion of the maxillae superior to the teeth
- produce mucous secretions that flush inferior surfaces of
the nasal cavities
• Palatine processes form most of the hard palate of
the mouth
- incisive fossa on the inferior midline marks the openings of
the incisive canals that contain small arteries and nerves

44. The Maxillae
Fig 6.12a

45. The Maxillae
Fig 6.12

46. The Palatine Bones
• Small, L-shaped bones (horizontal and vertical)
• Horizontal plates articulate with the maxillae to form
the posterior portions of the hard palate
- a greater palatine groove lies between the palatine bone and
the maxilla on each side
- usually contains 1 or more lesser palatine foramina
- nasal crest, marks the articulation with the vomer
• Vertical portion of the ‘L’ is formed by the
perpendicular plate of the palatine bone
- articulates with the maxillae, sphenoid, ethmoid, inferior
nasal concha
- medial surface has 2 ridges: 1) the conchal crest, and 2) the
ethmoidal crest
- orbital process, forms a small portion of the orbital floor

47. The Palatine Bones
Fig 6.13

48. The Palatine Bones

49. The Orbital Complex

50. Sectional Anatomy of the Skull
Fig 6.5

51. Sectional Anatomy of the Skull

52. The Mandible
Fig 6.14a

53. The Mandible

54. The Nasal Complex
• Paranasal sinuses are the interconnected hollow
spaces inside the frontal, ethmoid, sphenoid,
and maxillary bones
• These spaces reduce the weight of the skull,
produce mucus, and allow air to resonate for
voice production
• These paranasal sinuses are called the frontal
sinus, maxillary sinus, sphenoidal sinus, and the
ethmoidal air cells

55. The Nasal Complex
Fig 6.16a,b

56. The Nasal Complex
Fig 6.16c

57. The Nasal Complex
Fig 6.16d

58. Hyoid Bone
Fig 6.17

59. 22 Bones of the Skull
8 form the cranium
• Occipital
• Parietal (2)
• Frontal
• Temporal (2)
• Sphenoid
• Ethmoid
14 facial bones
Paired bones:
• Maxillae
• Palatine
• Nasal
• Zygomatic
• Lacrimal
• Inferior nasal conchae
Single bones
• Vomer
• Mandible