11.13 (dr. hemant kumar) cell surface modifications

these are all those lectures which u see in your class different frm online lectures

1. DR HEMANT KUMARDR HEMANT KUMAR
LECTURER LECTURER
ANATOMY DEPT:ANATOMY DEPT:
SINDH MEDICAL COLLEGE SINDH MEDICAL COLLEGE
& DOW UNIVERSITY OF & DOW UNIVERSITY OF
HEALTH SCIENCES, HEALTH SCIENCES,
KARACHIKARACHI..

2. CELL SURFACE CELL SURFACE
MODIFICATIONSMODIFICATIONS
MICROVILLIMICROVILLI
CILIACILIA
FLAGELLAFLAGELLA

3. Cilia, Flagella, and MicrovilliCilia, Flagella, and Microvilli
CiliaCilia move substances over the surface of move substances over the surface of
cellscells
FlagellaFlagella are much longer than cilia and are much longer than cilia and
propel sperm cellspropel sperm cells
MicrovilliMicrovilli increase the surface area of cell increase the surface area of cell
and aid in absorption and secretionand aid in absorption and secretion

4. MICROVILLIMICROVILLI
They are microscopic projections of the They are microscopic projections of the
free surface and are found in most free surface and are found in most
epithelia.epithelia.
They are numerous, often regularly They are numerous, often regularly
arranged and uniform in length.arranged and uniform in length.
Well developed in the lining of the small Well developed in the lining of the small
intestine and other absorptive epithelia.intestine and other absorptive epithelia.

5. MICROVILLIMICROVILLI
Microvilli of the intestine collectively Microvilli of the intestine collectively
appear vertically striated under L/M, so appear vertically striated under L/M, so
apical surface has been termed as striated apical surface has been termed as striated
border.border.
E/M reveal that the microvilli composing E/M reveal that the microvilli composing
the border are cell membrane covered the border are cell membrane covered
cytoplasmic extensions about 2 cytoplasmic extensions about 2
micrometer long.micrometer long.

6. MICROVILLIMICROVILLI
Each microvillus has a core of fine Each microvillus has a core of fine
filaments apparently anchored at the tip filaments apparently anchored at the tip
and extending into the terminal web.and extending into the terminal web.
They provide structural support.They provide structural support.
They are composed of a form of They are composed of a form of
contractile protein actin.contractile protein actin.
They may interact with myosin molecules They may interact with myosin molecules
of the terminal web.of the terminal web.

7. MICROVILLIMICROVILLI
They provide subtle degrees of microvillar They provide subtle degrees of microvillar
movement.movement.
Microvilli increase the surface area of the Microvilli increase the surface area of the
cells in correlation with absorptive cells in correlation with absorptive
functions.functions.
They are also numerous on the free They are also numerous on the free
surfaces of the PCT of the kidney as brush surfaces of the PCT of the kidney as brush
border. border.

8. .

9. CILIACILIA
They are large, often motile appendages, They are large, often motile appendages,
found on the apex of cells.found on the apex of cells.
May present singly or in massive numbers.May present singly or in massive numbers.
5-10 micrometer in length and 0.2 5-10 micrometer in length and 0.2
micrometer in diameter.micrometer in diameter.
Readily seen in light microscope.Readily seen in light microscope.
Internal structure can be resolved by E/M.Internal structure can be resolved by E/M.

10. CILIACILIA
E/M reveals that the shaft or free part of E/M reveals that the shaft or free part of
each cilium is enclosed by a plasma each cilium is enclosed by a plasma
lemma continuous with that of the cell.lemma continuous with that of the cell.
Each cilium contains longitudinal Each cilium contains longitudinal
microtubules, typically arranged in a microtubules, typically arranged in a
constant and orderly manner.constant and orderly manner.
Most cilia have two single central Most cilia have two single central
microtubules and nine peripheral pairs of microtubules and nine peripheral pairs of
fused double microtubules or doublets.fused double microtubules or doublets.

11. CILIACILIA
Microtubules extend from near the tip of Microtubules extend from near the tip of
cilium to its base.cilium to its base.
A basal body is located in the cytoplasm A basal body is located in the cytoplasm
just inside the free surface of the cell.just inside the free surface of the cell.
Each basal body is a modified centriole Each basal body is a modified centriole
constituted of a wall of nine triplet constituted of a wall of nine triplet
microtubules.microtubules.
It is similar to centriole which is needed It is similar to centriole which is needed
for cell division.for cell division.

12. CILIACILIA
Cilia are found in the epithelial lining of Cilia are found in the epithelial lining of
respiratory tract, female reproductive system.respiratory tract, female reproductive system.
Cilia beat in the coordinated rhythmical wave like Cilia beat in the coordinated rhythmical wave like
manner, promoting movement of materials over manner, promoting movement of materials over
the cell surfaces.the cell surfaces.
Beating of the cilia in the trachea produces an Beating of the cilia in the trachea produces an
upward movement of mucus with its entrapped upward movement of mucus with its entrapped
dust particles thus preventing the blockage of dust particles thus preventing the blockage of
lower respiratory tract. lower respiratory tract.

14. FLAGELLAFLAGELLA
Also have same axial structure as cilia but Also have same axial structure as cilia but
are much larger.are much larger.
Usually are present one or two per cell.Usually are present one or two per cell.
Present in the tail of the spermatozoon.Present in the tail of the spermatozoon.
Usually beat random whip or wave like Usually beat random whip or wave like
motion.motion.

15. FLAGELLAFLAGELLA
In certain locations of the body, ciliary In certain locations of the body, ciliary
projections are highly modified to serve projections are highly modified to serve
sensory receptor functions like in the outer sensory receptor functions like in the outer
segment of the rods and cones of retina segment of the rods and cones of retina
and in some of the hair cells of sensory and in some of the hair cells of sensory
portions of the inner ear. Such ciliary portions of the inner ear. Such ciliary
processes are usually not motile and lack processes are usually not motile and lack
the central pair of microtubules.the central pair of microtubules.
Nine doublets are however retained. Nine doublets are however retained.

16. STEREOCILIASTEREOCILIA
Are usually long microvilli.Are usually long microvilli.
Found in part of male reproductive system Found in part of male reproductive system
(epididymis) and in sensory regions of the inner (epididymis) and in sensory regions of the inner
ear.ear.
They donot have the structural characteristics of They donot have the structural characteristics of
the true cilia or flagella.the true cilia or flagella.
They increase the surface area of the apical cell They increase the surface area of the apical cell
membrane and may aid in secretion and membrane and may aid in secretion and
absorption (epididymis), reception and absorption (epididymis), reception and
transduction of vibratory stimuli (in the inner transduction of vibratory stimuli (in the inner
ear)ear)

19. Centrioles and Spindle FibersCentrioles and Spindle Fibers
Centrioles: Centrioles: cylindrical cylindrical
organelles located in the organelles located in the
centrosomecentrosome
–Pinwheel array of nine triplets of Pinwheel array of nine triplets of
microtubulesmicrotubules
–Centrosome:Centrosome: a specialized zone a specialized zone
of the cytoplasmof the cytoplasm
the site of microtubule formationthe site of microtubule formation
–Microtubules called Microtubules called spindle spindle
fibersfibers extend out in all directions extend out in all directions
from the centrosomefrom the centrosome
Spindle fibers are involved in the Spindle fibers are involved in the
separation of chromosomes during separation of chromosomes during
cell divisioncell division
–Form the bases of cilia and Form the bases of cilia and
flagellaflagella
Fig. 3.22

20. THANKS…….THANKS…….