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.
 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).