noun
definition
A complex polysaccharide, a polymer of N-acetylglucosamine, found in the exoskeletons of arthropods and in the cell walls of fungi; thought to be responsible for some forms of asthma in humans.
Examples of chitin in a Sentence
In Lingula the shell is composed of alternate layers of chitin and of phosphate of lime.
They yield chitin in place of chondrin or gelatin - as does also the cartilage of the Cephalopod's endoskeleton.
The parapodia of Chaetopoda are never coated with dense chitin, and are, therefore, never converted into jaws; the primitive " head-lobe " or prostomium persists, and frequently carries eyes and sensory tentacles.
In most cases the organic structure has disappeared, le i tving only a cavity, with perhaps a trace of chitin.
Usually they open into a median vagina, formed by an ectodermal inpushing and lined with chitin.
The cuticle is a dead substance, and is composed in large part of chitin.
In other Cheilostomes the amount of calcification may be much less, the supporting skeleton being largely composed of the organic material chitin.
In its simplest form the exoskeleton of a typical somite is a ring of chitin defined from the rings in front and behind by areas of thinner integument forming moveable joints, and having a pair of appendages articulated to its ventral surface on either side of the middle line.
The rigidity of the integument caused by the deposition of dense chitin upon it is intimately connected with the physiological activity and form of all the internal organs, and is undoubtedly correlated with the total disappearance of the circular muscular layer of the body-wall present in Chaetopods.
They are lined internally by a cuticular deposit of chitin.
Chitin is not exclusively an ectodermal product, but occurs also in cartilaginous skeletal plates of mesoblastic origin (connective tissue).
Instead of being made of bone, insect skeletons are made of a hard material called chitin.
Over three quarters of all known animal species produce chitin.
In Velella the pneumatophore becomes of complex structure and sends air-tubes, lined by a chitin and resembling tracheae, down into the compact coenosarc, thus evidently serving a respiratory as well as a hydrostatic function.
While the fundamental constituent is a cellulose in many Mucorini and other Phycomycetes, in others bodies like pectose, callose, &c., commonly occur, and Wisselingh's researches show that chitin, a gluco-proteid common in animals, forms the main constituent in many cases, and is probably deposited directly as such, though, like the other substances, it may be mixed with cellulose.
Very usually (but not in the Onychophora = Peripatus) all the parapodia are plated with chitin secreted by the epidermis, and divided into a series of joints - giving the " arthropodous " or hinged character.