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The nictitating membrane of a masked lapwing as it closes over the left eye, originating from the medial canthus. The nictitating membrane (from Latin nictare, to blink) is a transparent or translucent third eyelid present in some animals that can be drawn across the eye from the medial canthus to protect and moisten it while maintaining vision.
The majority of the tooth structure is formed from dentin, and the enamel serves as the superficial layer of the crown while the cementum serves to cover the root. In the mid-1990s, however, it was discovered that a very thin layer of enamel actually exists between the dentin and cementum on the roots of adult human teeth.
Fetal pigs are unborn pigs used in elementary as well as advanced biology classes as objects for dissection. Pigs, as a mammalian species, provide a good specimen for the study of physiological systems and processes due to the similarities between many pig and human organs.
Only one species of primate, the Calabar angwantibo, is known to have a functioning nictitating membrane. [ 44 ] The orbitalis muscle is a vestigial or rudimentary nonstriated muscle (smooth muscle) of the eye that crosses from the infraorbital groove and sphenomaxillary fissure and is intimately united with the periosteum of the orbit.
The membrane works to protect and moisten the eyelid while maintaining visibility. It also contributes to the aqueous portion of the tear film and possibly immunoglobulins. [ 14 ] Humans and some primates have a much smaller nictitating membrane; this may be because they do not capture prey or root vegetation with their teeth, so that there is ...
Teeth clipping in pigs is a management practice in which the sharp tips of newborn piglets' teeth are trimmed or filed to reduce the risk of injury to sows during nursing and minimize aggression-related injuries among piglets.
of or pertaining to teeth Latin dens, dentis, tooth dentifrice, dentist, dentition, dental dermat(o)-, derm(o)-of or pertaining to the skin Greek δέρμα, δέρματος (dérma, dérmatos), skin, human skin dermatology, epidermis, hypodermic, xeroderma -desis: binding Greek δέσις (désis) arthrodesis: dextr(o)-right, on the right side
Histologic slide showing a tooth bud. A: enamel organ B: dental papilla C: dental follicle. The tooth germ is an aggregation of cells that eventually forms a tooth. [2] These cells are derived from the ectoderm of the first pharyngeal arch and the ectomesenchyme of the neural crest.