In most vertebrates, this original one-layered structure quickly transforms into a two-layered tissue; a temporary outer layer, the periderm, which is disposed once the inner basal layer or stratum germinativum has formed.This inner layer is a germinal epithelium that gives rise to all epidermal cells. It divides to form the outer spinous layer (stratum spinosum). The cells of these two layers, together called the Malpighian layer(s) after Marcello Malpighi, divide to form the superficial granular layer (Stratum granulosum) of the epidermis.The cells in the stratum granulosum do not divide, but instead form skin cells called keratinocytes from the granules of keratin. These skin cells finally become the cornified layer (stratum corneum), the outermost epidermal layer, where the cells become flattened sacks with their nuclei located at one end of the cell. After birth these outermost cells are replaced by new cells from the stratum granulosum and throughout life they are shed at a rate of 30 - 90 milligrams of skin flakes every hour, or 0.720 - 2.16 grams per day.Epidermal development is a product of several growth factors, two of which are:
Transforming growth factor Alpha (TGFα) is an autocrine growth factor by which basal cells stimulate their own division. Keratinocyte growth factor (KGF or FGF7) is a paracrine growth factor produced by the underlying dermal fibroblasts in which the proliferation of basal cells is regulated. Function
Barrier
The epidermis serves as a barrier to protect the body against microbial pathogens, oxidant stress (UV light), and chemical compounds, and provides mechanical resistance to minor injury.
Tongue-tie, tongue tied or tongue-tied can refer to:

ankyloglossia, a medical condition in which the lingual frenulum (a membrane that connects the tongue to the floor of the mouth) is unusually short, causing restricted movement of the tongue.Other uses include:

Literature
Tongue-Tied, a 1997 novel by Liselotte Marshall
Tongue-Tied (short story collection), a 2002 collection of short stories by Paul Jennings
"Tongue-Tied" a short story included in the collection
Tongue-Tied: How a Tiny String Under the Tongue Impacts Nursing, Speech, Feeding, and More, a 2018 non-fiction book by Dr. Richard Baxter

Music
Tongue Tied (Red Dwarf song), a song by Danny John-Jules in character as the Cat which was featured in the Red Dwarf episode "Parallel Universe" in 1988
"Tongue Tied" (Boom Crash Opera song), 1995
"Tongue-Tied", a song by Earshot from their 2004 album Two
"Tongue Tied" (Eve 6 song), a single from their 1998 album, Eve 6
"Tongue Tied" (Faber Drive song), 2007
"Tongue Tied" (Grouplove song), 2011
"Tongue Tied" (Marshmello, Yungblud and Blackbear song), 2019
"Tongue Tied", a song by Status Quo from their 2007 album In Search of the Fourth Chord

Other uses
Tongue-tie (tack), a piece of equipment sometimes used on racehorses
"Tongue-Tied" (Orange Is the New Black), a 2015 television episode
Miley Cyrus: Tongue Tied, a 2014 short film starring Miley Cyrus