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The enfolding of a part of the wall of the blastula to form a gastrula.
The act of ensheathing or becoming ensheathed.
The process of burrowing or enfolding to form a hollow space within a previously solid structure, as the invagination of the nasal mucosa within a bone of the skull to form a paranasal sinus.



(1) In embryology, in-pouching, one of the processes of gastrulation, in which part of the wall of the embryo turns into its cavity and forms an inner layer, called the primitive entoderm.

(2) In medical practice, a form of intestinal obstruction in which a section of the gut works its way into (usually) a lower section, producing blockage of the lumen of the intestine. It is most often found in children.

References in periodicals archive ?
It is as much diverged from the spiralian stereotype as the nemertean pilidium, with which Owenia's development indeed shares some traits, including enlarged first quartet micromeres, gastrulation by invagination into a large blas-tocoel, and the formation of a convoluted primary ciliated band from numerous proliferative cells.
Similarities are also seen in the type of invagination, with the postsynaptic element invaginating into the presynaptic cells in both Octopus vulgaris and Aplysia californica (Budelmann and Thies, 1977; Bailey and Thompson, 1979).
We have not observed an actual epidermal invagination associated with the proboscis rudiment, although it is possible that it is present in earlier stages (before hatching).
deep invagination of epidermis that is filled with keratinous material and invagination not related to hair follicle are consistent with the diagnosis of NC.
Gastrulation follows by invagination to form a ciliated, pelagic planula larva.
Retrograde Dunndarm invagination nach Gastroenterostomie," Acta Chirurgica Scandinavica, vol.
The use of mechanical stapler can circumvent the problem; however, it was not used in our study and management was performed successfully by ICT and base invagination by purse-string sutures.
After resuscitation, a CT scan was performed, which showed dilatation of small intestine because of ileocecal invagination.
Basilar invagination in osteogenesis imperfecta and related osteochondrodysplasias: medical and surgical management.
A prominent parakeratotic column within an epidermal invagination that displays loss of the granular layer is found overlaying an eccrine duct with a dilated acrosyringium.
Serous tumours, of which 50% are usually seen in women <40 years of age, [12] develop by invagination of the surface epithelium of the ovary and secrete serous fluid.
Histology of the lesion showed keratin-filled epidermal invagination with parakeratotic columns of keratinocytes denoting cornoid lamella.