Type of cartilage in ear ossicles
Answers
Answer:
Incus. The incus develops from the first pharyngeal arch cartilage (Meckel's cartilage) and named from the resemblance to an anvil, onsists of a body and two crura.
The incus develops from the first pharyngeal arch cartilage (Meckel's cartilage) and named from the resemblance to an anvil, insists of a body and two crura.
The two crura diverge from one another nearly at right angles.
Gray suggested the incus has more like a "premolar tooth" appearance, with two roots, which differ in length, and are widely separated from each other.
Incus ossification is initiated in the fetal period.
Incus Development
- 16 weeks - force lines start through two cortical fascicles in the long process
- 17 to 20 weeks - two cortical fascicles progressively extend in a rostro-caudal direction
- 21 weeks - occupy the whole extension of the long process
- 22 weeks - fusion of both cortical fascicles begins.
- 30 weeks - strengthened by the crossing of bone trabeculae from one cortical to another. Two fascicles come out of the incus body, surrounding the medullary cavity and going in the direction of the short process.
The newborn and infant incus body normally contains bone marrow, that is eventually replaced by bone.
From recent study of histological sections from 55 human embryos and fetuses at 6 to 13 weeks of development.
- (Carnegie Stage 16) - incus anlage was found at the cranial end of the first pharyngeal arch. At this stage, each of the three anlagen of the ossicles in the middle ear were independent in different locations.
- (Carnegie Stage 16) - a homogeneous interzone clearly defined the incus and malleus anlagen. The cranial end of the incus was located very close to the otic capsule.
- 7 and 8 weeks - the short limb of the incus connecting with the otic capsule.
- 9 weeks - an initial disconnection of the incus from the otic capsule.
- 13 weeks - a cavity appeared between the otic capsule and incus.
