Paper - A model of the left half of the human mandible at the 17 mm CRL stage

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Fawcett E. A model of the left half of the human mandible at the 17 mm CRL stage. (1930) J Anat Physiol. 47(2): 225-34. PMID:17104287 | PMC1250145

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This historic 1930 brief note by Fawcett is an early description of the development of the human mandible using a model reconstruction.



See also by this author: Fawcett E. The development and ossification of the human clavicle. (1913) J Anat Physiol. 47(2): 225-34. PMID:17232952 | PMC1289013


Modern Notes: Musculoskeletal_System_-_Bone_Development_Timeline

Prenatal

Week 6 - Intramembranous ossification center develops lateral to Meckel's cartilage.

Week 7 - Coronoid process begins differentiating.

Week 8 - Coronoid process fuses with main mandibular mass.

  • Stage 21
    • bone-formation has taken place and formed a plate on the lateral side of Meckel's cartilage
    • plate is in the substance of, and is surrounded by, that mesodermal condensation that outlines the mandible and precedes the formation of bone.
    • plate of bone is confined to the region of what approximately corresponds to the future body of the mandible
    • mesodermal condensation can be traced further backwards always on the lateral side of Meckel's cartilage and the associated branches of the mandibular nerve.
    • beyond the limit of bone-formation the lateral pterygoid muscle can be seen running into and outlining the terminal part of the mesodermal condensation.
    • rudimentary condylar area - Meckel's cartilage with the inferior dental and lingual nerves on its upper surface lies medial to this area and inferior to the lateral pterygoid muscle.

Week 10 (approx) - Both condylar and coronoid processes are recognizable and anterior portion of Meckel's cartilage begins to ossify.

Weeks 12-14 - Secondary cartilages for the condyle, coronoid, and symphysis appear.

Weeks 14-16 - Deciduous tooth germs start to form.


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1853 Bone | 1885 Sphenoid | 1902 - Pubo-femoral Region | Spinal Column and Back | Body Segmentation | Cranium | Body Wall, Ribs, and Sternum | Limbs | 1901 - Limbs | 1902 - Arm Development | 1906 Human Embryo Ossification | 1906 Lower limb Nerves and Muscle | 1907 - Muscular System | Skeleton and Limbs | 1908 Vertebra | 1908 Cervical Vertebra | 1909 Mandible | 1910 - Skeleton and Connective Tissues | Muscular System | Coelom and Diaphragm | 1913 Clavicle | 1920 Clavicle | 1921 - External body form | Connective tissues and skeletal | Muscular | Diaphragm | 1929 Rat Somite | 1932 Pelvis | 1940 Synovial Joints | 1943 Human Embryonic, Fetal and Circumnatal Skeleton | 1947 Joints | 1949 Cartilage and Bone | 1957 Chondrification Hands and Feet | 1968 Knee


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A Model of the left half of the Human Mandible at the 17 mm CRL stage

Edward Fawcett
Edward Fawcett

By Professor Fawcett, M.D., F.R.S.


The sections from which this model was made were stained with Mallory’s stain, the most delicate known to me for bone. Fig. 1 shows the ossified mandible (M) as well as many other structures, e.g. Meckel’s cartilage, which is partially chondrified (M C1) and towards its anterior end unchondrified (M C2); the tongue (T) is also shown near its tip for topographical purposes: finally, the associated nerves, e.g. the mandibular (MN), the lingual (LN) with the submaxillary ganglion (SG), the inferior dental (I DN ), and the mental nerves (MN), are. introduced.


Fawcett1930 fig01.jpg

Fig. 1. Reconstruction of left mandible and annexes of a 17 millimetre human embryo viewed from above.

During the drawing for the production of the necessary wax plates a careful lookout was kept for tooth buds, but none were found. Furthermore, no sign of an incisive branch of the inferior dental nerve occurred, so the true termination of the inferior dental nerve would appear to be in the mental nerve and not a bifurcation into mental and incisive branches.


The mandible has ossified in the interval between the mental nerve and the unchondrified part of Meckel’s cartilage, and it reaches from not far from the middle line to just beyond the mental nerve, which is lodged in a groove on the upper margin of the bone. The groove is the mental groove (MG).

The bone is a simple plate of bone with no processes. Meckel’s cartilage is unchondrified from the front, back to the region of the mental groove.

The embryo from which this model was made I owe to the kindnessof my colleague, Prof. D. C. Rayner.


Cite this page: Hill, M.A. (2019, April 21) Embryology Paper - A model of the left half of the human mandible at the 17 mm CRL stage. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_A_model_of_the_left_half_of_the_human_mandible_at_the_17_mm_CRL_stage

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