| pili, sex | Filamentous or elongated proteinaceous structures which extend from the cell surface in gram-negative bacteria that contain certain types of conjugative plasmid. These pili are the organs associated with genetic transfer and have essential roles in conjugation. Normally, only one or a few pili occur on a given donor cell. this preferred use of "pili" refers to the sexual appendage, to be distinguished from bacterial fimbriae (fimbriae, bacterial), also known as common pili, which are usually concerned with adhesion. (12 Dec 1998) |
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| collum folliculi pili | The narrowed part of the hair follicle between the hair bulb and the surface of the skin. Synonym: collum folliculi pili. (05 Mar 2000) |
| cuticula pili | A layer of overlapping shingle-like cells that invest the hair cortex and serve to lock the hair shaft in its follicle. Synonym: cuticle of hair. Cuticula vaginae folliculi pili, cuticle of overlapping shingle-like cells lining the follicle of the hair. Synonym: cuticle of root sheath. (05 Mar 2000) |
| scapus pili | The non-growing portion of a hair which protrudes from the skin, i.e., from the follicle. Synonym: scapus pili. (05 Mar 2000) |
| sex pili | <cell biology> Fine filamentous projections (pili) on the surface of a bacterium that are important in conjugation. Often seem to be coded for by plasmids that confer conjugative potential on the host, in the case of the f plasmid, the F pili are 8-9nm diameter and several microns long, composed of pilin. Whether the pili merely serve to establish and maintain adhesive contact between the partners in conjugation or whether DNA is actually transferred through the central core of the pilus is still unresolved, although a simple adhesion role is more generally accepted. (18 Nov 1997) |
| I pili | See: pilus. Pili multigemini, the presence of several hairs in a single follicle. R pili, specialised pili found on bacterial cells, similar to F pili and associated with R plasmids. Pili torti, a condition in which many hair shafts are twisted on the long axis, congenital or acquired as a result of distortion of the follicles from a scarring inflammatory process, mechanical stress, or cicatrizing alopecia; the hair shafts resemble spangles in reflected light, are brittle, and break at varying lengths with many areas appearing bald with a dark stubble; as a developmental defect it can be manifested in such syndromes as Bjornstad's, Crandall's, and Menkes'. Synonym: twisted hairs. (05 Mar 2000) |
| folliculus pili | <dermatology> A tube-like opening in the epidermis where the hair shaft develops and into which the sebaceous glands open (13 Nov 1997) |
| F pili | See: pilus. F pilus, a structure responsible for attachment of individual male (F+) to female (F-) bacteria, forming conjugal pairs. (05 Mar 2000) |