Cristae (singular; crista)
The inner membrane of the mitochondria is responsible for creating a proton gradient that is essential for ATP production through oxidative phosphorylation. It contains the electron transport chain and ATP synthase complexes, which are key components of the energy production process in mitochondria.
The inner fold pleura closest to lung tissue is called the visceral pleura.
The third eyelid on a frog is called a nictitating membrane.
The "epicanthic fold" -- also called epicanthus -- is a fold of skin on the upper eyelid that partially covers the inner corner of the eye. Some people with Down syndrome manifest such a fold.
The process is called phagocytosis.
The thin fold of mucous membrane that extends from the floor of the mouth to the underside of the tongue is called the lingual frenulum. It helps to limit the movement of the tongue and is involved in speech and eating functions.
The cristae are fold in the mitochondria which increase its' surface area so that it can produce ADP + P=ATP.
The cristae are folds in the inner membrane of mitochondria where most ATP synthesis occurs through the process of oxidative phosphorylation. This is where enzymes and molecules involved in the electron transport chain are located, allowing for efficient production of ATP.
ep·i·can·thic foldn.A fold of skin of the upper eyelid that partially covers the inner corner of the eye. Also called epicanthus.Source: http://www.answers.com/topic/epicanthal-fold?cat=health
Pleura.
hymen
The double baglike fold of serous membrane which incloses the heart.