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Glossary - U




U cell

E cell (S)


Formerly called the E cell, this ectoblast forms a portion of the anterior wall of the rectum in the hermaphrodite. In the male, however, the cell acts as a blast cell and divides to produce a lineage whose progeny help establish a connection between the cloaca and the gonad (Sulston and Horvitz, 1977).


Fine structure (S)


The smallest details of cell structure as seen after fixation and staining for high resolution electron microscopy. Usually these features are not observable by light microscopy, even at high magnification.


Uncoordinated phenotype (S)
Locomotion abnormal (S)


Mutations causing an abnormal locomotion phenotype in the animal, which may include subtle twitching or halting behavior, odd jerky motions, curling or kinky motions, constant twitching, shrinking and expanding lengthwise without progress of the body, partial paralysis, or limp or rigid paralysis. Uncoordination is a very common phenotype among genetic mutations in C. elegans, only some of which are numbered among the listed unc mutants. The affected genes may be expressed either in neurons, muscles or even in other tissues affecting the structures required for coordinated movement, including the cuticle (as in Rol mutants). Some of these phenotypes are recognizable as morphological traits or spontaneous defects in movement, while some others are only revealed when the animal is stimulated to move, perhaps by prodding with a fine wire.

See Coiler      
See Kinker phenotype
See Paralysis
See Roller
See Shrinker phenotype
See Twitcher phenotype

Undead cells    

Surviving cells who were fated by lineage to undergo apoptosis, but which for some reason (mutation, random chance) did not die on schedule (White et al., 1991; Avery and Horvitz, 1987). Such surviving cells often exhibit some characteristics of differentiated cells, but rarely seem to contribute any new functionality to the whole animal by their presence. Occasionally they can replace or supplement the function of another existing cell.

See Apoptosis


See Scaffold

Undulate/ Undulatory

Bending back and forth in a smooth, sinusoidal, wave-like motion. This term well describes the locomotion of C. elegans and other nematodes which is similar to the movement of a snake or eel.

Unipolar Multipolar (A)

A neuron with only a single extension from the cell body. For example see the MI neuron.

ut cell

ut1 - ut 4


Uterine toroidal epithelial cells (ut1, ut2, ut3, ut4; each toroid is a multinucleate syncytium) which make up the bulk of the uterus. These four uterine toroid epithelial syncytia join to one another to make up both the anterior and posterior lobes of the uterus.

Uterine epithelia



A complex structure consisting of some 60 cells of multiple cell types which form a variety of (mostly) syncytial cell groups. All derive from the Z1 and Z4 blast cells, via the anchor cell, the DU and VU precursors, and then via the π and ρ precursors.

Uterine layer Oolemma (S)  

That portion of the eggshell that is secreted by the uterine sheath after the oocyte has been fertilized. This layer varies widely in structure and thickness among nematode species (Bird and Bird, 1991) though it is thought to include the vitelline layer, and in some nematode species, such as Ascaris, an outer fibrous glycoprotein layer (Foor, 1967; Lee and Lestan, 1971). The structure has not been well characterized as yet in C. elegans.

See Zona pellucida
Uterine lumen    

The inner space of the uterus through which the fertilized egg passes on its way out of the nematode via the vulva. Prior to the first fertilization event, the space is narrow and blocked by a series of extensions, or fingers, projecting from the uterine wall. The adult uterus inflates to form a much wider "egg chamber”, which houses developing embryos and acts as a passageway for male-produced sperm to travel from the vulva to the spermatheca.   

Uterine muscle





Sex-specific muscles of the hermaphrodite whose contractions squeeze on the uterus to help move eggs towards the vulval opening. These are derived postembryonically from the M lineage and have non-striated muscle characteristics. Each lobe of the uterus has 4 bands of muscles with each band composed of a left/right pair of um1 or um2 muscles. Uterine muscles are covered in a thin basal lamina which is anchored to the muscle via hemi-adherens junctions. Contraction of the muscles squeezes the uterus and moves the egg through the lumen. Muscles are not directly innervated, but are coupled via gap junctions to vulval muscles that are innervated by the egg-laying neurons.

Uterine seam cell utse cell

A large thin H-shaped epithelial cell formed by the fusion of eight π cell progeny with the anchor cell which extends along the lateral edge of the uterus, sealing dorsal and ventral halves to create a unified thin epithelium surrounding the egg chamber. The two sides of the "H" hold the uterus in place by attaching to the lateral seam cells while the central part of the "H" initially forms a "hymen" membrane between the uterine and vulval lumens, but which is broken by passage of the first egg thus creating continuity between the two lumens. Afterwards utse probably acts as a transitional epithelial cell between the uterus and vulva.

Uterine sheath

The portion of the uterine epithelium which surrounds the egg chamber, composed primarily of the ut1-ut4 toroids.

See ut cell

Uterine spermathecal valve sujn cells (S)

See Spermatheca uterine valve

Uterine vulval cell  

These 3 epithelial cells (uv1, uv2, uv3; all mononucleate) form the interface between the uterus and the vulva via a multilayered set of flaps.

Uterine wall toroidal cells    

See Toroidal cells


The portion of the somatic gonad which encloses the fertilized eggs after their passage through the spermatheca. It consists of anterior and posterior lobes which are connected via a central chamber. Eggs are incubated within the uterus until their passage through the vulval lumen and then out of the body via the vulval slit.

utse cell



See Uterine seam cell

uv cell uv1

See Uterine vulval cell

Edited for the web by Laura A. Herndon. Last revision: November 12, 2013. This section should be cited as: Herndon, L.A. and Hall, D.H. 2010. Glossary U. In WormAtlas.  doi:10.3908/wormatlas.6.21