Page 14 - Headlines Histology2024_Neat

• The Actin (thin filaments) is found in muscle cell, in the core of each
microvillus, in motile cells such as macrophages and in developing nerve
cells. Their diameter is about 5 nm.

• The Myosin (thick filaments) occurs mainly in muscle cells in association
with actin filaments. They have a diameter of 15 nm.

• The Intermediate filaments are 10 nm in diameter and include
neurofilaments in neurons, glial filaments in astrocytes and tonofilaments in
epithelial cells.

Microtubules

• They are hollow tubular structures of variable length with a constant
diameter of 25 nm. Microtubules are stable permanent structures in cilia,
flagella, centrioles and basal bodies.

• Each microtubule is made up of protein molecules (tubulin) that appear to
organize into protofilaments that run parallel to the length of the tubule. A
total of 13 protofilaments comprise the wall of a microtubule.

Functions of the cytoskeleton
• It provides the structural support for the plasmalemma, cellular organelles

and some cytosol enzyme system.
• It provides the means for the movement of intracellular organelles within

the cytoplasm.
• It plays an essential role in cell motility as well as provides the framework

of motile structures such as cilia and flagella.
• It is responsible for contractility of the muscle cells.
• It plays an important role in epithelial cell adhesion as well as cell division.

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