Acrania


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Related to Acrania: exencephaly

acrania

[ā′krān·ē·ə]
(medicine)
Partial or complete absence of the cranium at birth.

Acrania

[ā′krān·ē·ə]
(zoology)
A group of lower chordates with no cranium, jaws, vertebrae, or paired appendages; includes the Tunicata and Cephalochordata.

Acrania

 

a subphylum of lower chordate animals, as opposed to the subphylum of Craniata, or Vertebrata. Acrania have the following characteristics: the head section of the body is not separate; there is no skull (hence the name); the whole body is segmented, including some internal organs, the excretory system, and the sexual glands; the sensory organs are primitive (there are only sensory cells, lying in the skin and along the neural tube); and there is no heart, only a pulsating ventral blood vessel. There are two families. The family Branchiostomatidae includes 19 species, of which the best-known is the lancelet. The family Amphioxididae comprises three species. These three species are small (up to 1 cm) and live at great depths in the equatorial zone of the oceans.

References in periodicals archive ?
Exencephaly (differential diagnosis includes acrania, acalvaria, anencephaly, large encephalocele or amniotic band syndrome.
A trained clinician in fetal imaging may be able to identify acrania, anencephaly, and encephalocele, for example.
In addition to the CVS, the anatomical survey detected 2 fetuses with acrania, 2 with multi-structural abnormalities, and 4 with multi-structural abnormalities that were characteristic of trisomy 13, trisomy 18, trisomy 21 and Turner's syndrome, respectively.