Meckel's cartilage
| Meckel's cartilage | |
|---|---|
 Head and neck of a human fetus at eighteen weeks, with Meckel's cartilage and hyoid bar exposed. | |
 Mandible of human fetus 95 mm (3.7 in) long. Inner aspect. Nuclei of cartilage stippled. | |
| Details | |
| Precursor | First pharyngeal arch |
| Gives rise to | Incus,malleus |
| Identifiers | |
| Latin | cartilago arcus pharyngei primi |
| TE | cartilage_by_E4.0.3.3.3.1.3 E4.0.3.3.3.1.3 |
| Anatomical terminology | |
In humans, the cartilaginous bar of themandibular archis formed by what are known asMeckel's cartilages(right and left) also known asMeckelian cartilages;above this theincusandmalleusare developed. Meckel's cartilage arises from the firstpharyngeal arch.
The dorsal end of each cartilage is connected with the ear-capsule and is ossified to form themalleus;the ventral ends meet each other in the region of thesymphysis menti,and are usually regarded as undergoingossificationto form that portion of themandiblewhich contains theincisor teeth.
The intervening part of the cartilage disappears; the portion immediately adjacent to the malleus is replaced by fibrous membrane, which constitutes thesphenomandibular ligament,while from the connective tissue covering the remainder of the cartilage the greater part of the mandible is ossified.
Johann Friedrich Meckel, the Youngerdiscovered this cartilage in 1820.
Related:- Crypta Magna (Remnant of 2nd pharyngeal pouch from which develops the intratonsillar crypt).
Evolution
[edit]Meckel's cartilage is a piece ofcartilagefrom which the mandibles (lower jaws) ofvertebratesevolved. Originally it was the lower of two cartilages which supported the firstbranchial archin earlyfish.Then it grew longer and stronger, and acquired muscles capable of closing the developing jaw.[1]
In early fish and inchondrichthyans(cartilaginous fish such assharks), the Meckelian Cartilage continued to be the main component of the lower jaw. But in the adult forms ofosteichthyans(bony fish) and their descendants (amphibians,reptiles,birds,andmammals), the cartilage is covered in bone – although in theirembryosthe jaw initially develops as the Meckelian Cartilage. In alltetrapodsthe cartilage partially ossifies (changes to bone) at the rear end of the jaw and becomes thearticularbone, which forms part of the jaw joint in all tetrapods exceptmammals.[1]
In some extinct mammal groups likeeutriconodonts,the Meckel's cartilage still connected otherwise entirely modern ear bones to the jaw.[2]
Additional images
[edit]-
Vertical section of the mandible of an early human fetus. X 25.
References
[edit]
This article incorporates text in thepublic domainfrompage 66of the 20th edition ofGray's Anatomy(1918)
- ^abThe Gill Arches: Meckel's Cartilage,palaeos.Retrieved 4 December 2014.
- ^Meng, Jin (December 2014)."Mesozoic mammals of China: implications for phylogeny and early evolution of mammals".National Science Review.1(4): 521–542.doi:10.1093/nsr/nwu070.
