Tuesday 13 March 2012

BRANCHIOSTOMA-ATRIUM

The atrial is large body space other than coelom. It is formed by a pair of metapleural folds,on either side above the gill-slits of embryo,growing downwards and united ventrally by a transverse folds. In branchiostoma the gill-slits open intothe atrium and not directly to the exterior as in other chordates.The atrium projects into each dorsal coelomic canal on either side of pharynx forming the brown funnel or atriocoelomic canal whose function is unknown. The atrium projects the delicate pharyngeal region.

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