| Zone of polarizing activity | |
|---|---|
 The apical ectodermal ridge is a thickened epithelium at the most distal end of the limb bud. The zone of polarizing activity is at the posterior part of the limb bud. | |
| Details | |
| Identifiers | |
| Latin | zona activitatis polarisantis |
| Acronym(s) | ZPA |
| TE | of polarizing activity_by_E5.0.3.0.0.1.5 E5.0.3.0.0.1.5 |
| Anatomical terminology | |
The zone of polarizing activity (ZPA) is an area of mesenchyme that contains signals which instruct the developing limb bud to form along the anterior/posterior axis. Limb bud is undifferentiated mesenchyme enclosed by an ectoderm covering. Eventually, the limb bud develops into bones, tendons, muscles and joints. Limb bud development relies not only on the ZPA, but also many different genes, signals, and a unique region of ectoderm called the apical ectodermal ridge (AER). Research by Saunders and Gasseling in 1948 identified the AER and its subsequent involvement in proximal distal outgrowth.[1] Twenty years later, the same group did transplantation studies in chick limb bud and identified the ZPA. In 1993, Todt and Fallon showed that the AER and ZPA are dependent on each other.[2]
- ^ Saunders JW (December 1998). "The proximo-distal sequence of origin of the parts of the chick wing and the role of the ectoderm. 1948". The Journal of Experimental Zoology. 282 (6): 628–68. doi:10.1002/(SICI)1097-010X(19981215)282:6<628::AID-JEZ2>3.0.CO;2-N. ISSN 0022-104X. PMID 9846378.
- ^ Todt WL, Fallon JF (1 November 1987). "Posterior apical ectodermal ridge removal in the chick wing bud triggers a series of events resulting in defective anterior pattern formation". Development. 101 (3): 501–15. ISSN 0950-1991. PMID 3502993.