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(A) Dorsal view. (B) Lateral view. (C) Ventral view. (D) Mouth structure. [1] Gosner stage is a generalized system of describing stages of embryonal and larval development in anurans (frogs and toads). The Gosner system includes 46 numbered stages, from fertilized embryo (stage 1) to the completion of metamorphosis (stage 46).
The dermatome is the dorsal portion of the paraxial mesoderm somite which gives rise to the skin . In the human embryo, it arises in the third week of embryogenesis . [ 2 ] It is formed when a dermomyotome (the remaining part of the somite left when the sclerotome migrates), splits to form the dermatome and the myotome. [ 2 ]
A sagittal crest is a ridge of bone running lengthwise along the midline of the top of the skull (at the sagittal suture) of many mammalian and reptilian skulls, among others. The presence of this ridge of bone indicates that there are exceptionally strong jaw muscles.
This tissue derives from the unsegmented paraxial mesoderm and prechordal mesoderm. Tissues derived from the head mesoderm include connective tissues and the muscles of the face. The head mesoderm forms through a separate signaling circuit than the segmented paraxial mesoderm, though also involving BMP and fibroblast growth factor signaling.
These two terms, used in anatomy and embryology, describe something at the back (dorsal) or front/belly (ventral) of an organism. [2] The dorsal (from Latin dorsum 'back') surface of an organism refers to the back, or upper side, of an organism. If talking about the skull, the dorsal side is the top. [38]
Cranial kinesis is the term for significant movement of skull bones relative to each other in addition to movement at the joint between the upper and lower jaws. It is usually taken to mean relative movement between the upper jaw and the braincase. [1] Most vertebrates have some form of a kinetic skull. [1]
The primitive streak is a structure that forms in the early embryo in amniotes. [1] In amphibians, the equivalent structure is the blastopore. [2] During early embryonic development, the embryonic disc becomes oval shaped, and then pear-shaped with the broad end towards the anterior, and the narrower region projected to the posterior.
The neural fold is a structure that arises during neurulation in the embryonic development of both birds and mammals among other organisms. [1] [2] This structure is associated with primary neurulation, meaning that it forms by the coming together of tissue layers, rather than a clustering, and subsequent hollowing out, of individual cells (known as secondary neurulation).