DR HEMANT KUMARDR HEMANT KUMARLECTURER LECTURER ANATOMY DEPT:ANATOMY DEPT:SINDH MEDICAL SINDH MEDICAL COLLEGE & DOW COLLEGE & DOW UNIVERSITY OF HEALTH UNIVERSITY OF HEALTH SCIENCES, KARACHISCIENCES, KARACHI..

CELL SURFACE CELL SURFACE MODIFICATIONSMODIFICATIONS

MICROVILLIMICROVILLI CILIACILIA FLAGELLAFLAGELLA

Cilia, Flagella, and MicrovilliCilia, Flagella, and Microvilli

CiliaCilia move substances over the move substances over the surface of cellssurface of cells

FlagellaFlagella are much longer than cilia are much longer than cilia and propel sperm cellsand propel sperm cells

MicrovilliMicrovilli increase the surface area of increase the surface area of cell and aid in absorption and cell and aid in absorption and secretionsecretion

MICROVILLIMICROVILLI They are microscopic projections of They are microscopic projections of

the free surface and are found in the free surface and are found in most epithelia.most 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 Well developed in the lining of the small intestine and other absorptive small intestine and other absorptive epithelia.epithelia.

MICROVILLIMICROVILLI Microvilli of the intestine collectively Microvilli of the intestine collectively

appear vertically striated under L/M, appear vertically striated under L/M, so apical surface has been termed as so apical surface has been termed as striated border.striated border.

E/M reveal that the microvilli E/M reveal that the microvilli composing the border are cell composing the border are cell membrane covered cytoplasmic membrane covered cytoplasmic extensions about 2 micrometer long.extensions about 2 micrometer long.

MICROVILLIMICROVILLI Each microvillus has a core of fine Each microvillus has a core of fine

filaments apparently anchored at the filaments apparently anchored at the tip and extending into the terminal tip and extending into the terminal web.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 They may interact with myosin

molecules of the terminal web.molecules of the terminal web.

MICROVILLIMICROVILLI They provide subtle degrees of They provide subtle degrees of

microvillar movement.microvillar movement. Microvilli increase the surface area of Microvilli increase the surface area of

the cells in correlation with the cells in correlation with absorptive functions.absorptive functions.

They are also numerous on the free They are also numerous on the free surfaces of the PCT of the kidney as surfaces of the PCT of the kidney as brush border. brush border.

.

CILIACILIAThey are large, often motile They are large, often motile appendages, found on the apex of cells.appendages, found on the apex of cells.May present singly or in massive May present singly or in massive numbers.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 Internal structure can be resolved by E/M.E/M.

CILIACILIA E/M reveals that the shaft or free part E/M reveals that the shaft or free part

of each cilium is enclosed by a plasma of 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 microtubules and nine peripheral pairs of fused double microtubules or of fused double microtubules or doublets.doublets.

CILIACILIA Microtubules extend from near the tip Microtubules extend from near the tip

of cilium to its base.of cilium to its base. A basal body is located in the A basal body is located in the

cytoplasm just inside the free surface cytoplasm just inside the free surface of the cell.of the cell.

Each basal body is a modified Each basal body is a modified centriole constituted of a wall of nine centriole constituted of a wall of nine triplet microtubules.triplet microtubules.

It is similar to centriole which is It is similar to centriole which is needed for cell division.needed for cell division.

CILIACILIA Cilia are found in the epithelial lining of Cilia are found in the epithelial lining of

respiratory tract, female reproductive respiratory tract, female reproductive system.system.

Cilia beat in the coordinated rhythmical Cilia beat in the coordinated rhythmical wave like manner, promoting movement wave like manner, promoting movement of materials over the cell surfaces.of materials over the cell surfaces.

Beating of the cilia in the trachea produces Beating of the cilia in the trachea produces an upward movement of mucus with its an upward movement of mucus with its entrapped dust particles thus preventing entrapped dust particles thus preventing the blockage of lower respiratory tract. the blockage of lower respiratory tract.

FLAGELLAFLAGELLA Also have same axial structure as Also have same axial structure as

cilia but are much larger.cilia but are much larger. Usually are present one or two per Usually are present one or two per

cell.cell. Present in the tail of the Present in the tail of the

spermatozoon.spermatozoon. Usually beat random whip or wave Usually beat random whip or wave

like motion.like motion.

FLAGELLAFLAGELLA In certain locations of the body, In certain locations of the body,

ciliary projections are highly modified ciliary projections are highly modified to serve sensory receptor functions to serve sensory receptor functions like in the outer segment of the rods like in the outer segment of the rods and cones of retina and in some of and cones of retina and in some of the hair cells of sensory portions of the hair cells of sensory portions of the inner ear. Such ciliary processes the inner ear. Such ciliary processes are usually not motile and lack the are usually not motile and lack the central pair of microtubules.central pair of microtubules.

Nine doublets are however retained. Nine doublets are however retained.

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 (epididymis) and in sensory regions of the inner ear.inner ear.

They donot have the structural They donot have the structural characteristics of the true cilia or flagella.characteristics of the true cilia or flagella.

They increase the surface area of the They increase the surface area of the apical cell membrane and may aid in apical cell membrane and may aid in secretion and absorption (epididymis), secretion and absorption (epididymis), reception and transduction of vibratory reception and transduction of vibratory stimuli (in the inner ear)stimuli (in the inner ear)

Centrioles and Spindle Centrioles and Spindle FibersFibers

Centrioles: Centrioles: cylindrical cylindrical organelles located in the organelles located in the centrosomecentrosome– Pinwheel array of nine Pinwheel array of nine

triplets of microtubulestriplets of microtubules– Centrosome:Centrosome: a specialized a specialized

zone of the cytoplasmzone of the cytoplasm the site of microtubule the site of microtubule

formationformation– Microtubules called Microtubules called spindle spindle

fibersfibers extend out in all extend out in all directions from the directions from the centrosomecentrosome Spindle fibers are involved in Spindle fibers are involved in

the separation of chromosomes the separation of chromosomes during cell divisionduring cell division

– Form the bases of cilia and Form the bases of cilia and flagellaflagella

Fig. Fig. 3.223.22

THANKS…….THANKS…….