| hypodontia | A condition of having fewer than the normal complement of teeth, either congenital or acquired. Synonym: oligodontia, partial anodontia. Origin: hypo-+ G. Odous, tooth (05 Mar 2000) |
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| half and half nail | Division of the nail by a transverse line into a proximal dull white part and a distal pink or brown part; seen in uraemia. (05 Mar 2000) |
| tooth-and-nail syndrome | <syndrome> Hypodontia associated with absent or very small nails at birth. Common among Dutch Mennonites in Canada. (05 Mar 2000) |
| gonadal dysgenesis | <embryology, genetics> A rare genetic disorder in women that is characterised by the absence of an X chromosome. This disorder inhibits normal sexual development and causes infertility. Features include webbing of the neck, short stature, retarded development of secondary sex characteristics, absence of menses, coarctation of the aorta, low hairline, eye abnormalities (drooping eyelids) and skeletal deformities. Treatment include oestrogen supplementation at puberty. Growth hormone replacement may be necessary in some cases. Cardiac surgery may be necessary to correct coarctation of the aorta. Incidence: 1 in 3,000 births. (10 Oct 1997) |
| gonadal dysgenesis, 46,xy | A syndrome characterised by "streak gonads" in a phenotypic female with a 46,xy karyotype. It is due to a mutation which inhibits the function of the y-borne determinant that would normally cause the indifferent embryonic gonad to differentiate into a testis. The streak gonad is incapable of ovulation or oestrogen secretion. The syndrome is sometimes called "pure gonadal dysgenesis," but this designation may also refer to the presence of streak gonads with a 46,xx karyotype. (12 Dec 1998) |
| gonadal dysgenesis, mixed | A syndrome of gonadal dysgenesis in which there is a testis on one side and a "streak gonad" on the other. The phenotype is generally male, but may be female since the individual is a mosaic. Various karyotypes have been identified, including 45,xo/47,xyy; 45,xo/46,xy; and 45,xo/46,xyo. (12 Dec 1998) |
| seminiferous tubule dysgenesis | A disorder in which the seminiferous tubules exhibit an abnormal cytoarchitecture and extensive hyalinization; the testes are small, and few spermatozoa are formed; the body habitus may be eunuchoid, and gynaecomastia may be present; urinary gonadotropin output is usually high, and the incidence of mental deficiency and illness increased; sex chromatin may be male or female, and androgen secretion ranges from subnormal to normal. It is a constant feature of (and is often used synonymously with) Klinefelter's syndrome. Synonym: germinal aplasia. (05 Mar 2000) |
| hybrid dysgenesis | The inability of certain strains of the fruit fly Drosophila melanogaster to interbreed with each other because they produce offspring that are all sterile or offspring which have a high number of harmful mutations. (09 Oct 1997) |
| dysgenesis | Defective development. (18 Nov 1997) |
| iridocorneal mesodermal dysgenesis | Mesodermal dysgenesis of cornea and iris, producing pupillary anomalies, posterior embryotoxon, and secondary glaucoma. Synonym: Rieger's anomaly. (05 Mar 2000) |
| testicular dysgenesis | A congenital derangement of seminiferous tubular structure and function, resulting in male infertility; the defect in spermatogenesis may be incomplete, as in maturational arrest or premature sloughing, or spermatogenesis may be completely absent, as in the Sertoli-cell-only syndrome. (05 Mar 2000) |
| body of nail | The exposed portion of the nail distal to its root. Synonym: corpus unguis. (05 Mar 2000) |
| racket nail | A broad flat thumbnail resulting from a congenital shorter and wider distal phalanx of the thumb. (05 Mar 2000) |
| germinative layer of nail | The deeper layer of the nail that is continuous with the stratum germinativum of the surrounding skin and from which the nail plate is continuously formed. Synonym: germinative layer of nail. (05 Mar 2000) |
| parrot-beak nail | A markedly curved fingernail. (05 Mar 2000) |