In human anatomy

Human anatomy

Human anatomy is primarily the scientific study of the morphology of the human body. Anatomy is subdivided into gross anatomy and microscopic anatomy. Gross anatomy is the study of anatomical structures that can be seen by the naked eye...

, the eponychium [Greek epi (on, upon) + onychion (little claw)], also known as the cuticle, is the thickened layer of skin

Skin

-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...

 surrounding fingernails and toenails

Nail (anatomy)

A nail is a horn-like envelope covering the dorsal aspect of the terminal phalanges of fingers and toes in humans, most non-human primates, and a few other mammals. Nails are similar to claws, which are found on numerous other animals....

. Beneath the cuticle is a thin layer of a membrane known as the pterygium

Pterygium

Pterygium most often refers to a benign growth of the conjunctiva. A pterygium commonly grows from the nasal side of the sclera. It is usually present in the palpebral fissure. It is associated with, and thought to be caused by ultraviolet-light exposure , low humidity, and dust...

. The function is to protect the area between the nail and epidermis from exposure to harmful bacteria. The vascularization pattern is similar to that of perionychium.

Similarly, in hoofed animals

Ungulate

Ungulates are several groups of mammals, most of which use the tips of their toes, usually hoofed, to sustain their whole body weight while moving. They make up several orders of mammals, of which six to eight survive...

, the eponychium is the deciduous

Deciduous

Deciduous means "falling off at maturity" or "tending to fall off", and is typically used in reference to trees or shrubs that lose their leaves seasonally, and to the shedding of other plant structures such as petals after flowering or fruit when ripe...

 hoof capsule in fetus

Fetus

A fetus is a developing mammal or other viviparous vertebrate after the embryonic stage and before birth.In humans, the fetal stage of prenatal development starts at the beginning of the 11th week in gestational age, which is the 9th week after fertilization.-Etymology and spelling variations:The...

es and newborn foal

Foal

A foal is an equine, particularly a horse, that is one year old or younger. More specific terms are colt for a male foal and filly for a female foal, but these terms are used until the horse is age three or four. When the foal is nursing from its dam , it may also be called a suckling...

s, and is a part of the permanent hoof in older animals.