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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 ?
The neural plate invaginates beneath the epidermal layer to form the neural tube.
26) Additionally, there may be a role for sinonasal endoscopic treatment for selected patients with a symptomatic arachnoid cyst that abuts or invaginates into the paranasal sinuses.
To regenerate the missing digestive system, the body wall begins to invaginate (Fig.
In the myriapods so far investigated, ganglia form in a different way and can vary somewhat: clusters of tightly packed cells invaginate into the interior of the embryo.
We suppose that the ectodermal epithelium and the invaginate d archenteron are physically continuous during the invagination processes and that the blockage of invagination is mainly due to physical constraint of the ectodermal layer attached to the glass dish.
Proximally, the lateral walls of the diverticulum invaginate to form tracheoesophageal folds, which eventually fuse in the midline.
De-flagellated larval epithelia do not invaginate in a cell sheet, but are disarranged into individual amoeboid cells that each migrate to the inner region of a metamorph by amoeboid movement.
The lining epithelium of inverted papillomas most often is a non-keratinizing, stratified squamous type of epithelium that invaginates in the underlying stroma.
Retrograde gastric intussusception is a rare type of intussusception where a part of the stomach with all layers invaginates into the oesophagus (2).
1) It is a benign tumoral entity covered with columnar or cuboid epithelium with a cystic appearance characterized by proliferation of Von Brunn islets (transitional epithelium which invaginates into lamina propria, a process induced by irritation in chronic cystitis mimicking carcinomatous invasion).
The uterus develops from celomic epithelium during the 6th week of development during which it invaginates to form paramesonephric duct (mullerian duct).
Two tissue layers (endoderm and ectoderm) develop as one side of the embryo invaginates to form the gut.