{{Unreferenced, date=December 2009
A typhlosole is an internal fold of the intestine or intestine inner wall. Typhlosoles occur in bivalve mollusks,
lamprey
Lampreys (sometimes inaccurately called lamprey eels) are an ancient extant lineage of jawless fish of the order Petromyzontiformes , placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like s ...
echinoderm
An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...
s.
In
earthworm
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...
s, it is a dorsal flap of the intestine that runs along most of its length, effectively forming a tube within a tube, and increasing the absorption area by that of its inner surface. Its function is to increase intestine surface area for more efficient absorption of digested nutrients. In different
earthworm
An earthworm is a terrestrial invertebrate that belongs to the phylum Annelida. They exhibit a tube-within-a-tube body plan; they are externally segmented with corresponding internal segmentation; and they usually have setae on all segments. T ...
families, the typhlosole appears to have multiple origins. The Lumbricidae, for example, have a typhlosole which is an infolding of all layers of the intestine wall, whereas in some other families (e.g.
Megascolecidae
The Megascolecidae is a taxonomic family of earthworms which is native to Madagascar, Australia, New Zealand and both South East Asia and North America. All species of Megascolecidae belong to the Clitellata class. Megascolecidae are a large fami ...
), it is an infolding of only the inner layer, and in many earthworms it is absent.
See also
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body cavity
A body cavity is any space or compartment, or potential space, in an animal body. Cavities accommodate organs and other structures; cavities as potential spaces contain fluid.
The two largest human body cavities are the ventral body cavity, and ...