Advanced Biology

1. Advanced Biology Chapter 7 - Skull

2. Overview • Usually consists of 22 bones • 8 form the cranium • 14 form the facial skeleton • All bones but the lower jaw are interlocked by sutures • The lower jaw (mandible) is held to the cranium by ligaments

3. Cranium • Encloses and protects the brain • Provides attachment points for muscles that make chewing and head movement possible • Some cranial bones contained air-filled cavities called paranasal sinuses • These sinuses are lined with mucous membranes and are connected to the nasal cavity by passages • Reduce the weight if the skull • Increase the intensity of the voice by serving as resonant sound chambers

4. Bones of the Cranium

5. Bones of the Cranium • Frontal Bone

6. Bones of the Cranium • Frontal Bone • Forms the anterior portion of the skull above the eyes • Includes the forehead, roof of the nasal cavity, and roofs of the orbits (bony sockets) of the eyes • Develops in two parts that are usually completely fused by the fifth or sixth year of life • Parts: • Supraorbital foramen (or notch) • Located on the upper margin of each orbit • Allows nerves and blood vessels to pass to the tissues of the forehead • Frontal sinus • Located above each eye near the midline

7. Bones of the Cranium • Frontal Bone

8. Bones of the Cranium • Parietal Bone

9. Bones of the Cranium • Parietal Bones • Located on each side of the skull just behind the frontal bone • Are curved and have four borders • Sutures: • Fused together along the sagittal suture • Meet the frontal bone at the coronal suture

10. Bones of the Cranium • Parietal Bone

11. Bones of the Cranium • Occipital Bone

12. Bones of the Cranium • Occipital Bone • Forms the back of the skull and the base of the cranium • Sutures: • Joins the parietal bones along the lambdoid suture • Special Features: • Foramen magnum • Located on the lower surface • Allows the inferior part of the brainstem to connect with the spinal cord • Occipital condyles • Rounded processes • Located on each side of the foramen magnum • Articulate with the first vertebra (atlas) of the vertebral column

13. Bones of the Cranium • Occipital Bone

14. Bones of the Cranium • Temporal Bones

15. Bones of the Cranium • Temporal Bones • Form part of the sides and the base of the cranium • House the internal ear structures • Sutures: • Join the parietal bones along the squamous suture

16. Bones of the Cranium • Temporal Bones

17. Bones of the Cranium • Temporal Bones (cont.) • Special Features: • External acoustic meatus • Located near the inferior margin • Leads inwards to parts of the ear • Mastoid Process • Rounded projection • Located below each external acoustic meatus • Provides an attachment for certain muscles of the neck • Styloid process • Long, pointed process • Located below each external acoustic meatus • anchors muscles associated with the tongue and the pharynx • Carotid canal • Located near the mastoid process • Transmits the internal carotid artery • Jugular foramen • Opening located between the temporal and occipital bones • Transmits the jugular vein • Zygomatic process • Projects anteriorlyfrom the temporal bone in the region of external auditory meatus • Joins the temporal process of the zygomatic bone to form the zygomatic arch (cheek)

18. Bones of the Cranium • Temporal Bones

19. Bones of the Cranium • Sphenoid Bone

20. Bones of the Cranium • Sphenoid Bone • Located in anterior portion of cranium • Consists of a central part and 2 wing-like structures that extend laterally towards the sides of the skull • Helps form the base of the cranium, the sides of the skull, and the floors and sides of the orbits • Special Features: • Sellaturcica • Saddle-shaped depression • Located along the midline • Houses the pituitary gland which hangs from the base of the brain by a stalk • Sphenoidal sinuses • Lie next to each other • Separated by a bony septum that projects downward into the nasal cavity

21. Bones of the Cranium • Sphenoid Bone

22. Bones of the Cranium • Ethmoid Bone

23. Bones of the Cranium • Ethmoid Bone • Located in front of the sphenoid bone • Consists of two masses (one on each side of the nasal cavity) joined horizontally by cribriform plates (which form part of the roof of the nasal cavity) • Each cribriform plate has tiny openings called olfactory foramina through which nerves associated with the sense of smell pass • A perpendicular plate projects downward in the midline from the cribriform plates to form most of the nasal septum • Also forms sections of the cranial floor, orbital walls, and nasal cavity walls

24. Bones of the Cranium • Ethmoid Bone (cont.) • Special features • Superior nasal concha and middle nasal concha • Delicate, scroll-shaped plates • Project inward from lateral portions the ethmoid bone towards the perpendicular plate • Support mucous membranes that line nasal cavity • Mucous membranes moisten, warm, and filter air as it enters the respiratory tract • Ethmoidal sinuses • Small air spaces • Cristagalli • A triangular process • Projects upward into the cranial cavity between the cribriform plates • Place of attachment for membranes that enclose the brain

25. Bones of the Cranium • Ethmoid Bone

26. Facial Skeleton • Consists of 13 immovable bones and a movable lower jaw bone • Form the basic shape of the face • Provide attachments for muscles that move the jaw and control facial expressions

27. Facial Skeleton

28. Facial Skeleton • Maxillary Bones

29. Facial Skeleton • Maxillary Bones • Form the upper jaw • Contain the sockets of the upper teeth • Portions of the bones form the anterior roof of the mouth (hard pallete) the floors of the orbits, and the sides and floor of the nasal cavity • All other immovable bones articulate with the maxillary bones • Special features: • Maxillary sinuses • Inside the maxillae, lateral to the nasal cavity • Largest of the sinuses (extend from the floor of the orbits to the roots of the upper teeth) • Palatine processes • Portions of the maxillary bones that fuse along the midline (median palatine suture) and form the anterior section of the hard palate • Alveolar process • Downward projection on the inferior border of each maxillary bone • Together, the two processes form a horseshoe shaped arch called the alveolar arch • Teeth occupy cavities in the arch and are bound to the bony sockets by dense connective tissue

30. Facial Skeleton • Maxillary Bones

31. Facial Skeleton • Pallatine Bones

32. Facial Skeleton • Palatine Bones • L-shaped bones located behind the maxillae • Horizontal portions form the posterior section of the hard plate and the floor of the nasal cavity • Perpendicular portions help form the lateral walls of the nasal cavity

33. Facial Skeleton • Pallatine Bones

34. Facial Skeleton • Zygomatic Bones

35. Facial Skeleton • Zygomatic Bones • Form the prominences of the cheeks below and to the sides of the eyes • Help form the lateral walls and the floors of the orbits • Special features: • Temporal process • Extends posteriorly to join the zygomatic process of a temporal bone

36. Bones of the Cranium • Zygomatic Bones

37. Bones of the Cranium • Lacrimal Bone

38. Facial Skeleton • Lacrimal Bones • Thin, scalelike structures located in the medial wall of each orbit between the ethmoid bone and the maxilla • A groove in the anterior portion of the bone leads from the orbit to the nasal cavity and provides a pathway for a channel that carried tears from the eye to the nasal cavity

39. Facial Skeleton • Nasal Bones

40. Facial Skeleton • Nasal Bones • Long, thin, and nearly rectangular • Lie side by side and are fused at the midline to form the bridge of the nose • Serve as attachments for the cartilaginous tissues that form the shape of the nose

41. Facial Skeleton • Vomer Bone

42. Facial Skeleton • Vomer Bone • Thin and flat • Located along the midline within the nasal cavity • Joins the perpendicular plate of the ethmoid bone posteriorly to form the nasal septum

43. Facial Skeleton • Inferior Nasal Concha

44. Facial Skeleton • Inferior Nasal Conchae • Fragile, scroll-shaped bones attached to the lateral walls of the nasal cavity • Largest of the conchae • Located below the superior and middle nasal conchae of the ethmoid bone • Support mucous membranes within the nasal cavity

45. Facial Skeleton • Mandible

46. Facial Skeleton • Mandible • Horizontal, horseshoe shaped body with a flat ramus projecting at each end • Special Features: • Ramus • Divided into the mandibularcondyle (posterior) and the coronoid process (anterior) • The mandibularcondyles articulate with the mandibularfossae of the temporal bones • The coronoid processes provide attachments for muscles used in chewing • Alvelolar border • Curved bar of bone on the superior border of the mandible • Contains the hollow sockets of the lower teeth • Mandibular foramen • Opening located on the medial side of the mandible, near the center of each ramus • Admit s blood vessels and a nerve that supply the roots of the lower teeth • Mental foramen • Opening through which branches of the blood vessels and the nerve emerge • Opens on the outside near the point of the jaw • Supply the tissues of the chin and the lower lip

47. Facial Skeleton • Mandible

48. Passageways of the Skull

49. Infantile Skull • Soft spots: • At birth, fibrous membranes connect the cranial bones • The area where these membranes are located are called fontanels (soft spots) • Soft spots permit molding (some movement between the bones) which assists in movement through the birth canal • Closure of soft spots: • The posterior fontanel usually closes about 2 months after birth • The sphenoidal fontanel usually closes at about 3 months • The mastoid fontanel usually closes near the end of the 1st year • The anterior fontanel may not close until the middle or end of the second year • Characteristics • Small face with a prominent forehead and large orbits • Jaw and nasal cavity are small • Sinuses are incompletely formed • Frontal bone is in 2 parts • Skull bones are thin and somewhat flexible and so are easily fractured

50. Infantile Skull