allantoic sac

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al·lan·to·ic sac

the dilated distal portion of the allantois; it forms part of the placenta in many mammals.

allantoic sac

The expanded end of the allantois, well developed in birds and reptiles.
See also: sac


a pouch; a baglike organ or structure. See also conjunctival sac.

air sac
1. alveolar sac.
2. one of the large air-filled diverticula of the respiratory system of birds. See also air sacs.
allantoic sac
alveolar s's
the spaces into which the alveolar ducts open distally, and with which the alveoli communicate.
anal sac
endolymphatic sac
the blind, flattened cerebral end of the endolymphatic duct.
heart sac
the pericardium.
hernial sac
the peritoneal pouch that encloses a herniated viscus or mesentery.
lacrimal sac
see lacrimal sac.
paranal sac
pleural sac
the pleura-lined cavity which contains the lung.
ruminal sac
one of the dorsal and ventral sacs of the rumen which are themselves further subdivided to create a caudodorsal sac and a caudoventral sac.
yolk sac
the extraembryonic membrane connected with the midgut; in vertebrates other than true mammals, it contains a yolk mass. See also yolk sac.