| germ layer | <embryology> A layer of cells produced during the process of gastrulation during the early development of the animal embryo, which is distinct from other such layers of cells, as an early step of cell differentiation. The three types of germ layers are the endoderm, ectoderm, and mesoderm. Diploblastic organisms (e.g. Coelenterates) have two layers, ectoderm and endoderm, triploblastic organisms (all higher animal groups) have mesoderm between these two layers. Germ layers become distinguishable during late blastula/early gastrula stages of embryogenesis and each gives rise to a characteristic set of tissues, the ectoderm to external epithelia and to the nervous system for example: although some tissues contain elements derived from two layers. (18 Nov 1997) |
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| germ layer theory | The developmental biology theory that during early development, the animal embryo divides itself into two or three germ layers, each of which then proceed to further differentiate into organs and tissues specific to that particular layer. (09 Oct 1997) |
| hair cells, inner | Bulbous cells that are medially placed in one row in the organ of corti. In contrast to the outer hair cells, the inner hair cells are fewer in number, have fewer sensory hairs, and are less differentiated. (12 Dec 1998) |
| inner | 1. Further in; interior; internal; not outward; as, an spirit or its phenomena. "This attracts the soul, Governs the inner man,the nobler part." (Milton) 3. Not obvious or easily discovered; obscure. Inner house, the angle formed by the inner edges of a carpenter's square. Origin: AS. Innera, a compar. Fr. Inne within, fr. In in. See In. Source: Websters Dictionary (01 Mar 1998) |
| inner cell mass | A group of cells found in the mammalian blastocyst that give rise to the embryo and are potentially capable of forming all tissues, embryonic and extra embryonic, except the trophoblast. (18 Nov 1997) |
| inner dental epithelium | Inner enamel epithelium, the columnar epithelial layer of enamel matrix, secreting ameloblasts, of the odontogenic organ of a developing tooth. (05 Mar 2000) |
| inner malleolus | The process at the medial side of the lower end of the tibia, forming the projection of the medial side of the ankle. Synonym: malleolus medialis, inner malleolus, internal malleolus. (05 Mar 2000) |
| inner membrane | The smaller of a double membrane. (05 Mar 2000) |
| inner sheath | The material that encases the two central microtubules of the ciliary axoneme. (18 Nov 1997) |
| inner table of skull | The inner compact layer of the cranial bones. Synonym: lamina interna cranii. (05 Mar 2000) |
| Ehrlich's inner body | A round oxyphil body found in the red blood cell in case of haemocytolysis due to a specific blood poison. Synonym: Heinz-Ehrlich body. (05 Mar 2000) |
| germ | 1. <biology> That which is to develop a new individual; as, the germ of a foetus, of a plant or flower, and the like; the earliest form under which an organism appears. "In the entire process in which a new being originates . Two distinct classes of action participate; namely, the act of generation by which the germ is produced; and the act of development, by which that germ is evolved into the complete organism." (Carpenter) 2. That from which anything springs; origin; first principle; as, the germ of civil liberty. <biology> Disease germ, the theory that living organisms can be produced only by the evolution or development of living germs or seeds. See Biogenesis, and Abiogenesis. As applied to the origin of disease, the theory claims that the zymotic diseases are due to the rapid development and multiplication of various bacteria, the germs or spores of which are either contained in the organism itself, or transferred through the air or water. See Fermentation theory. Origin: F. Germe, fr. L. Germen, germinis, sprout, but, germ. Cf. Germen, Germane. Source: Websters Dictionary (01 Mar 1998) |
| germ cell | Cell specialised to produce haploid gametes. The germ cell line is often formed very early in embryonic development. (18 Nov 1997) |
| germ cells | The reproductive cells in multicellular organisms. (12 Dec 1998) |
| germ cell tumour | A type of brain tumour. (12 Dec 1998) |