Download Specialization of the cell surface

Specialization of the cell surface
1. Microvili: found in absorptive cell, proximal renal tubule. The glycocalyx is
thicker than it is in most other cell.
The complex of microvillus and glycocalyx may be seen with L.M. and is called
brush or striated border.
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Normal microvilli (right) in contrast of microvilli structure in
coeliac disease (left).
2. Cilia and flagella: cilia are cylindrical motile structure, surrounded by the
cell membrane, cilia inserted into basal bodies at the apical pole of the cell.
Cilia beat in waves that sweep across the surface of an epithelium. Always in
the same direction, they bend forward producing a power stroke that pushes a
long the mucus. In some organs, cilia have lost their motility and assumed
sensory cell (retina of the eye) modified cilium specialized for an absorbing
light.
flagella: long structure the only functional flagellum in humans is
the tail of sperm.
3. Stereocilia: are long non-motile extensions of cells found in epididymis and
ductus differences.
Intercellular junctions
The cells are firmly attached to each other by various kinds of intercellular
junctions
1. desmosomes : junction provides a mechanism for communication between
adjacent cells.
2. Tight junction: junction serves as sites of adhesion and as seals to prevent
the flow of material through the space between epi. Cells.
3. Gap junction : found in nearly all mammalian tissues, skeletal muscle being
a major exception
4. hemidesmosmes : observed in the contact zone between epi cells and basal
lamina that bind the epithelial cells to the subjacent basal lamina tight junction
(zonula occludens) Her the most apical of the junctions zonula refers to the fact
the junction forms a band completely encircling the cell the principal function
of the tight junction is to form a seal that prevents the flow of material between
epi. Cells.