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Advanced Biology

Advanced Biology. Chapter 7 - Skull. 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. Cranium. Encloses and protects the brain

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Advanced Biology

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  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

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