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The apical ectodermal ridge (AER) is a structure that forms from the ectodermal cells at the distal end of each limb bud and acts as a major signaling center to ensure proper development of a limb. After the limb bud induces AER formation, the AER and limb mesenchyme —including the zone of polarizing activity (ZPA)—continue to communicate ...
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. [1] The epidermal layer provides a barrier to infection from environmental pathogens [2] and regulates the amount of water released from the body into the atmosphere through transepidermal water loss.
Snakes are a particularly good example for studying limb loss, as they underwent limb loss and regeneration multiple times throughout their evolution before they finally lost their legs for good. Much of the gene expression during embryonic development is regulated via spatiotemporal and chemotactic signaling, [ 20 ] as depicted by the image to ...
For the average adult human, the skin has a surface area of 1.5–2.0 square metres (15–20 sq ft). The thickness of the skin varies considerably over all parts of the body, and between men and women, and young and old. An example is the skin on the forearm, which is on average 1.3 mm in males and 1.26 mm in females. [4]
In a growing fetus, fingerprints form where the cells of the stratum basale meet the papillae of the underlying papillary layer of the dermis, resulting in the formation of the ridges on the fingers. Fingerprints are unique to each individual and are used for forensic analyses because the patterns do not change with the growth and aging processes.
The epidermal tissue includes several differentiated cell types: epidermal cells, guard cells, subsidiary cells, and epidermal hairs . The epidermal cells are the most numerous, largest, and least specialized. These are typically more elongated in the leaves of monocots than in those of dicots. Diagram of moderate scale leaf anatomy
Retrieved from "https://en.wikipedia.org/w/index.php?title=Epidermal_ridges&oldid=756405634"This page was last edited on 24 December 2016, at 01:01 (UTC). (UTC).
Meckel nerve endings are most numerous beneath the ridges of the fingertips which make up fingerprints, and less so in the palms and forearm. [citation needed] They can be found at a depth of 900 μm in human fingertips. [4] In hairy skin, Merkel nerve endings are clustered into specialized epithelial structures called "touch domes" or "hair ...