What is terminal web of cell?
The terminal web is a zone or a region located at the base of the microvilli in certain specialized epithelial cells (such as intestinal epithelial cells). The actin filaments in the terminal web are stabilized by spectrin. They anchor the terminal web to the apical cell membrane.
What is terminal web in histology?
The terminal web is a filamentous structure found at the apical surface of epithelial cells that possess microvilli. It is composed primarily of actin filaments stabilized by spectrin, which also anchors the terminal web to the apical cell membrane. This spreading apart of the microvilli aids cells in absorption.
Do cilia have terminal bars?
The portion of the cell below and perpendicular to the cilia seen in pap-stained smears of ciliated columnar cells, which corresponds to the belt desmosomes, actin filaments and other proteins aggregated at the apical end of the cells.
Are microtubules associated with terminal web?
Within the core of the microvillus are microtubules that contribute to the maintenance of its structure and integrity. These microtubules extend into the dense terminal web region located subjacent to the microvillus.
What is a junctional complex?
Junctional complexes are symmetrical structures formed between adjacent cells and consist of three components: Firstly, a band of tight junctions, forming an occluding zone in the top position (zonula occludens, ZO, cf. also Fig.
What is the tight junction?
Tight junctions are intercellular adhesion complexes in epithelia and endothelia that control paracellular permeability. This paracellular diffusion barrier is semipermeable: it is size- and charge-selective. Paracellular ion permeability at tight junctions is largely determined by their claudin composition.
What is a terminal bar epithelium?
Terminal bar is a histological term given to the unresolved group of junctional complexes that attach adjacent epithelial cells on their lateral surfaces: the Zonula Occludens, Zonula Adherens, Macula Adherens and Macula Communicans.
What is the purpose of a terminal web?
The terminal web can function as a contractile structure that influences the spatial distribution of microvilli as well as the development and morphogenesis of tissues containing polarized epithelial cells.
What are the 3 cell junctions?
Cell junctions fall into three functional classes: occluding junctions, anchoring junctions, and communicating junctions. Tight junctions are occluding junctions that are crucial in maintaining the concentration differences of small hydrophilic molecules across epithelial cell sheets.
Where is the terminal web located in the cell?
(September 2015) ( Learn how and when to remove this template message) The terminal web is a filamentous structure found at the apical surface of epithelial cells that possess microvilli. It is composed primarily of actin filaments stabilized by spectrin, which also anchors the terminal web to the apical cell membrane.
What are the filaments of the terminal web composed of?
It is composed primarily of actin filaments stabilized by spectrin, which also anchors the terminal web to the apical cell membrane. The presence of myosin II and tropomyosin helps to explain the contractile ability of the terminal web.
What happens when the terminal web is contracted?
When contracted, the terminal web causes a decrease in diameter of the apex of the cell, causing the microvilli, which are anchored into the terminal web through their stiff actin fibers, to spread apart. This spreading apart of the microvilli aids cells in absorption. ^ Hirokawa N, Tilney LG, Fujiwara K, Heuser JE (1982).
What makes a bus bar different from a terminal block?
Unlike a terminal block, a bus bar gangs all the studs or terminals together into one ‘bus’. This makes one electrical ‘node’ of the same potential (voltage level). A bus bar is designed to make a solid connection point from one source to many branch circuits.