Invagination

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invagination

[in‚vaj·ə′nā·shən]
(embryology)
The enfolding of a part of the wall of the blastula to form a gastrula.
(physiology)
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.

Invagination

 

(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 ?
Following gastrulation, the notochord plate invaginates about the axial midline to make a cylindrical rod during tailbud formation, and then the notochord cells are moved toward the midline to form a single row by an event known as convergent extension (Fig.
(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.
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.
The true capsule of the thyroid is a thin, densely adherent fibrous layer that sends out septa that invaginate into the gland, forming pseudolobules.
They subsequently invaginate centrally to become the nasal pits by the fifth week.
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.
The tubule system in these cephalocarid muscles consists of the transverse tubules (t-tubules), which invaginate from the sarcolemma at the level of the 1-band and Z-line, with branches in the A-band region forming part of a triad (Fig.
[4] The capsule at specific regions invaginates the parenchyma of the organ in form of trabeculae.
Under a light microscope, hair showing nodular trichorrhexis is diagnostic (the distal area of hair invaginates toward its proximal area).
Intussusception is a condition wherein one segment of intestine invaginates into another section, similar to the way in which the parts of a collapsible telescope slide into one another.
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).