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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



(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.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Goetghebeur (1986) already doubted the value of this trait, but since the invagination above the root cap seemed to be an important characteristic in other embryo types, he distinguished a Websteria-type.
However, in patients who have celiac disease and do not receive any treatment, it has been reported in recent years that invagination is seen as a rare clinical finding of the disease (3).
The deletion of both Fgf3 and Fgf10 has revealed that the development of molar is inhibited prior to the bud stage, suggesting possible compensations between Fgf3 and Fgf10 during invagination of the dental epithelium [79, 80].
Benign causes, such as a relatively more dilated proximal appendiceal lumen relative to the distal portion, mobile appendicular wall resulting in active peristalsis, or invagination of the appendiceal stump following appendectomy, are leading causes of appendiceal intussusception [5].
At stage 17, the Mullerian duct appears via a deep invagination at the level of the 3rd thoracic somite and proceeds to grow caudally towards the Wolffian ducts until fusion in stage 18.
A clinical diagnosis of obstructive defecation syndrome (Wexner constipation score = 14) and anterior anal fissure was made; the patient was then subject to colonoscopy and defecography that showed an anterior rectocele with an ampullary invagination.
Histopathology showed epidermal acanthosis, deep epidermal invagination of a parakeratotic column (cornoid lamella), which is distinctive feature of PEODDN with absent granular layer .
Histological examination showed multiple, keratin-filled invagination, a parakeratotic column (i.e., cornoid lamella), a loss of the granular layer of the underlying epidermis, and dense lympho-histiocytic infiltrate in the dermis, compatible with porokeratosis (Fig.
An intussusception is defined as invagination of one segment of bowel into lumen of adjacent distal segment.
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.
Pediatric surgery consultation with abdominal ultrasonography showed no invagination and surgical pathology was not considered.