this lecture covered the bones, embryology, meninges, and blood supply to the head. the neurocranium is made up of the frontal, parietal, occipital, temporal, and sphenoid bones. the temporal bone is made up of the squamous portion and the petrous portion, the latter of which makes up part of the cranial base. the sphenoid bone is a winged shaped bone that has lesser and greater "wings" and houses the pituitary in the sellae turcica. between the bones of the skull are sutures, which are fusions of the bones that ossify with age. the coronoid sutures fuse the frontal and parietal bones, the sagittal suture fuses the left and right parietal bones, the lamboidal sutures fuse the occiptal and parietal bones. the intersection of the coronoid and sagittal sutures is the bregma junction, the intersection of the sagittal and lamboidal is the lambda junction, and the intersection of the temporal, parietal, frontal, and sphenoid bones on the lateral sides is called the pteryion junction.
the spine develops from sclerotome cells which migrate medially, surround the notochord, and begin to form cartilaginous "models", from which bones form in the process of endochondrial ossification. the individual vertebrae are formed when loose and dense portions of adjacent somites fuse, and the notocord eventually becomes the nucleus pulposus. primary ossification centers in the vertebrae form the bone that ossify from 3-5 years of age, while secondary ossification centers are at the edge of the vertebrae and are active during bone growth during puberty.
the skull bones are developed from lateral plate mesoderm, neural crest cells, somitomeres, and somites. in contrast to the spine, skull bones are formed by intramembranous ossification, which is direct formation of bone without a cartilage model. fontanelles are the spaces between the developing bones that eventually develop into the sutures. the growth of the skull bones is halted in the mid teens when the spheno-occipital joint and the spheno-ethmoidal joint close. finally, the spheno-occipital synchondrosis is the junction between the sphenoid and the basioccipital bone, and can determine the jaw morphology; a large angle at the synchondrosis can cause overbite and a small angle can cause underbite.
below the skull bones lie the meninges, the connective tissue coverings of the brain- dura mater, arachnoid mater, and pia mater. dura mater is the outermost, and includes a falx cerebri septa that separates the two brain hemispheres, as well as a tentorium cerebelli septa that separates the occipital lobes from the cerebrum. the arachnoid mater is the next layer down, and has a subdural layer right underneath the dura mater which is made up of thick connective tissue, and a "subarachnoid space" which is filled with trabeculae. these connect to the innermost layer, pia mater, which is loose connective tissue that aids in anchoring the blood vessels of the brain.
the epidural space is the space between the dura mater and the skull bones and is the site of epidural hematomas, where the middle meningeal artery (the artery that branches off the external carotid and supplies blood to the bones and dura) ruptures and fills the epidural space with blood. the subdural space is the space between the dura and the arachnoid mater; this can be the site of an subdural hematoma, where blood returning from veins in the brain to dural sinuses rupture and fill the subdural space. epidural hematomas are much more severe and occur faster because of the higher arterial blood pressure.
questions
bones of neurocranium...
1. what are the bones of the neurocranium?
2. what are the two portions of the temporal bone?
3. what are four anatomical features of the temporal bone?
4. what are some anatomical features of the body of the sphenoid bone?
5. what are the bones that make up the cranial base?
sutures and junctions...
6. what are sutures?
7. where is the coronal suture?
8. where is the sagittal suture?
9. where is the lamboidal suture?
10. where is the squamosal suture?
11. where is the bregma junction?
12. where is the lambda junction?
13. where is the pteryion junction?
spine development...
14. describe the development of the spine from the somites.
15. how are intersegmental vertebrae formed?
16. notocord becomes the...
17. what is the explanation for the fact that we have 8 cervical nerves with only 7 cervical vertebrae?
18. describe endochondral ossification of the vertebrae.
19. what is the difference between primary and secondary ossification centers?
skull development...
20. what are the skull bones and cartilage derived from?
21. vault bones are formed by...
22. skull form determined by...
23. what are fontanelles?
24. describe the development of the cranial base.
25. how does the longitudinal growth of the skull end during the mid teens?
26. what is the spheno-occipital synchondrosis?
27. what is a large angle of the spheno-occipital synchondrosis associated with?
28. what is a small angle of the spheno-occipital synchondrosis associated with?
meninges...
29. what are the three layers in the meninges?
30. what are the dura mater septa and what do they separate?
31. what are the two portions to the arachnoid mater?
32. describe the pia mater layer.
33. what is the epidural space?
34. what is the subdural space?
35. what is the subarachnoid space?
blood supply...
36. where is the middle meningeal artery? what does it supply?
37. where is the middle meningeal artery most susceptible to damage?
38. what is a subdural hematoma?
39. what is an epidural hematoma?
40. which type of hematoma develops faster and why?
answers
1. frontal, parietal, occipital, temporal, sphenoid.
2. the squamous portion, which forms part of the neurocranium, and the petrous portion.
3. internal/external meatus, styloid process, mastoid process, zygomatic process.
4. the sellae turcica, dorsum sellae, sphenoid sinuses
5. frontal, sphenoid, temporal (petrous portion), occipital, ethmoid
6. fibrous joints between skull bones that ossify with age.
7. between frontal and parietal bones.
8. between parietal bones.
9. between parietal and occipital bones.
10. between the temporal and parietal bones.
11. between the coronal and sagittal sutures.
12. between the lamboidal sutures and sagittal suture.
13. the junction between the frontal, temporal, parietal, and sphenoid bones.
14. sclerotome cells migrate medially, surround neural tube, and form spinal column.
15. fusion of dense and loose tissues of adjacent somites.
16. nucleus pulposus
17. cranial nerve I is above C1- would have been below the "8th" cervical vertebrae, which divided into the dens of C2 and part of the basioccipital bone early in development.
18. the mesoderm begins to differentiate into a cartilage "model" around the notocord, and eventually is replaced by bone.
19. primary ossification centers form bone that fuse between 3-5 years. secondary ossification centers lie on the periphery of vertebrae and are active in puberty.
20. lateral plate mesoderm, neural crest, somitomeres, somites
21. intramembranous ossification.
22. soft tissues.
23. the cartilage between the vault bones that eventually forms the sutures.
24. cranial base is formed by the intramembranous cartilage that joins to form the chondrocranium.
25. the sphenooccipital and sphenoethmoidal joints close.
26. the fusion of the sphenoid and the basioccipital bone that closes around 12-16 years.
27. square jaws or overbite.
28. wide angled mandibles, protrusion of mandibles.
29. dura mater, arachnoid mater, pia mater.
30. the falx cerebri separates the hemispheres and the tentorium cerebelli separates the cerebellum from the occipital lobes.
31. the thick subdural portion and the subarachnoid space, which contains arachnoid trabeculae, which connect to the pia mater.
32. thin CT layer that supports blood vessels on the surface of the brain.
33. the potential space between the dura and the bone.
34. potential space between dura and arachnoid mater.
35. CSF between arachnoid and pia mater.
36. it branches off the external carotid, comes through the foramen spinosum, and supplies blood to the bone and dura.
37. near pterion.
38. cerebral veins that drain into dural sinuses rupture and blood fills the subdural space.
39. meningeal arteries rupture and blood fills the epidural space.
40. external hematomas, because of the higher arterial pressure.
No comments:
Post a Comment