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Ward- dev of skull
| Question | Answer |
|---|---|
| Viscerocranium | Facial Bones. Develope from mesechyme that migrates to pharyngeal arches under the direction of the Neural Crest cells |
| Neurocranium | Skull bones. Developes from mesenchyme derived from sclerotome of somites. |
| Skull base | Cartilage growth plate at the base of the skull causes skull elongation. |
| Four embryonic bones of the base of the skull | 1.Basioccipital. 2.Basisphenoid. 3.Preshnoid. 4.Mesethmoid. **All formed by endochondral ossification of the mesenchyme from sclerotome of somites |
| Endochondral ossifications contribution to chnage in facial appearance as we age. | It takes place over time, elongation at the epiphyseal growth plates. Causes the Jaw to elongate inferiorly and the face to grow larger. |
| Neotony and Achondroplasia | Neotony is the retention of child-like features. Since the facial bones and cranial base rely on endochondrial ossification to grow, the face will remain smaller in protion to the head and will resemble that of a child. (due to early growth plate closure) |
| Intramembranous Ossification | Direct ossification of embryological tissue. Forms spongy trabecular bone (highly vascular) sandwiched b/w two Lamellar bones and is one reason the skull is so much larger than the face in infants. |
| Sphenobasilar Synchondrosis | Cartilagenous junction of posterior surface of sphenoid bone and the basil portion of occipital bone. Compression may result in impaired cranial rhythmic impulses. Manipulation may aid in CSF movement. |
| Bones formed from Intramembranous ossification | those forming from somatic mesoderm as paired bones of the skull: 1.Frontal. 2.Parietal. 3.Posterior occipital. 4.Parietal region of temporal |
| Calvarium bone growth | Grow through intramembranous ossification from a center of ossification outwards until they hit eachother. |
| Suture formation | Once the fronts of the two bones in contact overlap, signals from the dura below stabilize the sutures while other signals thicken the cranial bones. Suture then communicates to the dura underneath to stop osteogenic signals. |
| Areas of bone growth and resorption | Bone growth occurs in areas of high tension on the periosteum. Bone resorption occurs in areas of high compression of the periostium. **Allows the skull to expand while the cortex grows. Inside it resorpbed while the outside expands. |
| Affect of Aging on sutures | Sutures remained packed with CT throughout life allowing flex. However, they can ossify in old age. |
| What happens if there is a lack of signals from the dura or sutures during suture formation? | The sutures will fuse too early |
| Sutures in neonate/child | Coronal, sagittal, lambdoid, squamous, and metopic. |
| Fontanels in neonate/child | Anterior, Posterior, Anteriolateral (sphenoidal), Posterolateral (mastoid) |
| Premature closure of sutures results in? | Head growing abnormally parallel to the affeted suture. |
| What happens to the Metopic suture? | in 85% of adults, it fuses, creating one singal frontal bone. |
| Trigonocephaly | Premature fusion of the metopic suture which results in a triangular forehead. Causes transverse growth restriction, parallel growth expansion |
| Scaphocephaly | Premature fusion of the sagittal suture. Creates a long, narrow, boat-shaped head. (most common) |
| Plagiocephaly | Many suture involved, causes a flattening of the skull. |
| Adult sutures | 1.Coronal Suture b/w frontal and parietal bones. 2.Sagittal Suture b/w two parietal bones. 3.Lambdoid suture b/w occipital and parietal bones. 4.Squamous suture b/w temporal and parietal bones. |
| Dural Structures involved in dural strains | 1.Falx Cerebri (desecends b/w cerebral hemispheres in the longitudinal fissure). 2.Flax cerebelli. 3. Tentorium Cerebelli (dura b/w inferior occipital lobes and the cerebellum). **strains can compress peripheral nerves' entrance and exit. |
| Changes of the Eustachian tube | Connects middle ear/ mastoid air cells with nasopharynx. Begin horizontal and end more vertical. |
Created by:
WeeG
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