cytology.ppt
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BASICS OF CELLULAR STUDY
Limits on Cellular Growth
• Cells must have enough cytoplasm to function!
• Can’t have too much!– Some
structural “leeway” in size
– Ability to compensate isn’t infinite
A Single Cell!
http://en.wikivisual.com/images/3/35/Raw_egg.jpg
THE FIRST KEY THE FIRST KEY DEFINITIONDEFINITION
•CELL:CELL: A mass of protoplasm A mass of protoplasm surrounded by a membrane surrounded by a membrane and containing a nucleus and and containing a nucleus and organellesorganelles– The fundamental unit of lifeThe fundamental unit of life
–CELLS DO NOT EXIST AS CELLS DO NOT EXIST AS INDEPENDENT ENTITIESINDEPENDENT ENTITIES
(No, not even in blood…as we’ll see later!)(No, not even in blood…as we’ll see later!)
THE SECOND KEY THE SECOND KEY DEFINITIONDEFINITION
• TISSUE:TISSUE: An aggregation of cells An aggregation of cells and intercellular materials and intercellular materials specialized for specific functionsspecialized for specific functions– Cells are Cells are alwaysalways part of a tissue part of a tissue– Tissue’s function determines what Tissue’s function determines what
cells are presentcells are present– Cells make tissue function possibleCells make tissue function possible– Structure of Structure of cellscells often predictable often predictable
based on based on tissuetissue function & function & vice vice versaversa
FOUR “BASIC
TISSUES”• EPITHELIUMEPITHELIUM• CONNECTIVE CONNECTIVE
TISSUETISSUE• MUSCLEMUSCLE• NERVOUS NERVOUS
TISSUETISSUE– OrgansOrgans made up made up
of theseof these– At least 2 basic At least 2 basic
tissues in any tissues in any organorgan
THE THIRD KEY THE THIRD KEY DEFINITIONDEFINITION
ORGANS: ORGANS: • Aggregations of Aggregations of
cells, tissues, and cells, tissues, and intercellular intercellular materials materials specialized for specialized for specific functionsspecific functions– Tissues Tissues are not are not
autonomousautonomous – AlwaysAlways integrated integrated
with with other tissuesother tissues to form organsto form organs
• Separation of Separation of tasks tasks and of cells and of cells & tissues& tissues is a is a hallmark of hallmark of organsorgans
DifferentiatioDifferentiationn
• Process by which Process by which cellscells come to have come to have different characteristics & capabilitiesdifferent characteristics & capabilities
• Differentiated Differentiated cells produce cells produce different different proteins than their progenitorsproteins than their progenitors– Not all capabilities expressedNot all capabilities expressed
• Not limited in timeNot limited in time– Continues throughout lifeContinues throughout life, , e.g.e.g., wound , wound
healing & hemopoiesishealing & hemopoiesis
• Usually a Usually a precursor or “stem” cell typeprecursor or “stem” cell type is involvedis involved– Reserve stem cells often present in Reserve stem cells often present in
tissues/organstissues/organs
• Differentiation of Differentiation of cells & cell lines cells & cell lines determines determines organorgan function & function & physiologyphysiology
Teased nerve fibers, OsO4 stain
SIZE RANGE IN ANIMAL CELLS
• Smallest: 3-4 m– Some cells of
blood, e.g. quiescent lymphocytes
• Largest: 100-150 m– Some neurons– Monocytes– Skeletal muscle
SMALL CELLS HAVE SMALL CELLS HAVE LIMITATIONSLIMITATIONS
• Typically very little cytoplasmTypically very little cytoplasm– Limits functionsLimits functions– May have inactive inclusionsMay have inactive inclusions– Nuclear material condensedNuclear material condensed– May be “transformed” to an active stateMay be “transformed” to an active state
Lymphocyte in a smear, Wright’s Stain, 1000x
Differentiation:How We Get From….
Here to Here
DifferentiatioDifferentiationn
• Process by which Process by which cellscells come to have come to have different characteristics & capabilitiesdifferent characteristics & capabilities
• Differentiated Differentiated cells produce cells produce different different proteins than their progenitorsproteins than their progenitors– Not all capabilities expressedNot all capabilities expressed
• Not limited in timeNot limited in time– Continues throughout lifeContinues throughout life, , e.g.e.g., wound , wound
healing & hemopoiesishealing & hemopoiesis
• Usually a Usually a precursor or “stem” cell typeprecursor or “stem” cell type is involvedis involved– Reserve stem cells often present in Reserve stem cells often present in
tissues/organstissues/organs
• Differentiation of Differentiation of cells & cell lines cells & cell lines determines determines organorgan function & function & physiologyphysiology
Teased nerve fibers, OsO4 stain
CELL DEATH• Many cells are pre-
programmed to die– Major mechanism of
morphogenesis– Shapes and sculpts limbs,
etc.– Timing is exact and
preprogrammed
• Many embryonic structures only temporary – Removes the “scaffold” from
the “building”
• Examples: – Formation of paws– Wound healing
Stem Cells
• A general term• A population of
“reserve” cells– Quiescent– Can be
stimulated – Undergo
differentiation– One stem may
produce several cell lines
THE PLASMA THE PLASMA MEMBRANEMEMBRANE
• Defines Defines cell’s limitscell’s limits
• Controls Controls passage of passage of materials materials between between interior & interior & exteriorexterior
• Site of Site of receptors, receptors, markers, markers, etc.etc.
• Can be Can be inferred but inferred but not directly not directly seen with seen with LMLM
• Easily Easily visible with visible with electron electron microscopymicroscopy
Two adjacent P.M.’s (arrows) define the limits of cells A & B. The space between is in neither cell: it’s the “intercellular compartment.
CONCEPTUAL MODEL OF THE P.M.
• A “fluid mosaic model”: a lipid bilayer with “islands” of protein to control movement; surface markers of protein, glycolipids & glycoproteins for recognition & signalling
Image from Histology by Gartner & Hyatt
PLASMA MEMBRANE
MICROVILMICROVILLILI
• In LM seen as “brush border”– Not individually
resolvable– Uniform length
& height– Intestine,
kidney, some other sites• Places where
absorption is vital
The refractile fringe of microvilli as seen in the light microscope is referred to as a “brush border”; this example is from the intestine
MICROVILLI
• Filled with cytoplasm, surrounded with PM• May contain actin filaments• May be arranged for maximum # per unit area• Fairly small structures
PM ADAPTATION FOR PM ADAPTATION FOR ABSORPTION/SECRETIONABSORPTION/SECRETION
• BASAL FOLDS • “Reverse” of
microvilli– Basal end of
cell, not apex– Infolds of PM
containing cytoplasm
• Often contain mitochondria
• Associated with active transport– Slower
transfer rate– Transporting
“finished goods”
P.M. ADAPTATIONS FOR P.M. ADAPTATIONS FOR MOVEMENT:CILIA & FLAGELLAEMOVEMENT:CILIA & FLAGELLAE
• Cell migration • Movement of materials
on cell surface• Always involves
microtubules– Cilia and flagellae– Amoeboid motion
• Entire cell or only parts of it may be affected
• Directional• Energy from ATP• Interact with aqueous
environment – Respiratory, reproductive
systems• An ancient development
– The only solution!
Cilia on the cells lining the tracheaCilia on the cells lining the trachea
CILIA & FLAGELLAE
STRUCTURE OF CILIA
Don’t Confuse Cilia & Don’t Confuse Cilia & Microvilli!Microvilli!
• An An order of magnitude difference in sizeorder of magnitude difference in size• Cilia can be 10-100 Cilia can be 10-100 m long, and at least 10 m long, and at least 10 m m
thickthick• Microvilli rarely exceed 1.0 Microvilli rarely exceed 1.0 m thick and 10 m thick and 10 m longm long
Cilia MV
Image from Bloom & Fawcett, A Textbook of Histology
ADAPTATIONS FOR MAINTAINING SHAPE
• Odd shapes crucial to function– Internal
“scaffolding”– May serve other
needs• Internal routing of
materials• “Wiring” for
information transfer
• Disruption causes problems– Chemotherapy
agents• e.g. Colchicine
MICROTUBULES & MICROTUBULES & MICROFILAMENTSMICROFILAMENTS
• Vital to movement normal architecture
• Ubiquitous and variable in makeup– May be contractile
• Cilia, flagellae, and amoeboid movement
– May be “stiff” – May be for internal
transport – Polymeric structures
• Shorten & lengthen by adding dimers
• Principal component is tubulin
• May contain ATPase, dynein
MICROTUBULES• 20-50 nm (200-500 Å)• Cytoskeleton
– Mitotic spindle, cilia, flagella
CYTOSKELETAL MICROTUBULES• Maintenance of shape of odd cells, e.g. neurons
MICROFILAMENTS
• Intermediate filaments– Internal
structural “scaffold”
– Anchor nucleus– Connect
cytoskeleton to PM
– Maintain shape of nuclear envelope
• Thin microfilaments– Mainly actin for
intracellular contractility• Amoeboid motion,
division, etc.
– Myosin usually involved as well
– Gel-like network in cytosol of other thin filaments
MICROFILAMENTS & INTERMEDIATE FILAMENTS
• Smaller than microtubules (6-10 nm) & associated with contractility– Actin & myosin
• May be involved with adhesion structures– Tonofilaments
of desmosomes
• Also a cytoskeletal element
• Variable in size, related to function
MICROFILAMENTS
Astroglial fibers in an astrocyte
MICROFILAMENTS
• Microfilaments & secretory vesicles, rat ovarian granulosa cells
MICROFILAMENTS
Actin & myosin in skeletal muscle
ADAPTATION FOR SURFACE PROTECTION
• Cells are susceptible to damage– May be
unavoidable, e.g. Intestinal cells eroded by digestive juices
– Strategy is to delay it
• Glycocalyx– Expendable &
renewable surface covering
– Resistant to erosion
– Can be “sacrificed”
GLYCOCALYX• Cell surface coat
– Carbohydrate in nature• Glyco = “sweet” calyx
= “husk”– Term coined by John
Luft in 1965• Found on all cells to
some extent• Usually heaviest at free
surface• Not quite “basement
membrane”• Functions usually
protective• Some enzymatic
activity• PAS+ / RR+ in EM• May not be obvious in
routine preps
GLYCOCALYX
• LM image courtesy of Dr. Ihab El-Zhogby
ADAPTATIONS FOR TISSUE INTEGRITY &
FUNCTIONAL COHESION
• Tissues are INTEGRATED both structurally & functionally
• Cells are not independent units• Cells must communicate• Cells must maintain contact
with each other• A whole series of PM
specializations
Occluding (“Tight”) Junctions
• Adjacent PM’s are fused together
OCCLUDING JUNCTION
• Function to separate “inside” from “outside”
• Control passage of materials; forces them to go through a cell
• Used to control osmotic pressure, ion flux, etc.
DESMOSOMES• Most common
membrane specialization
• Found in all types of tissues & organs
• Similar to adhering junction– Also for mechanical
integrity– Distinguished by
dense filamentous component
– Anchor cells to each other
• A “spot weld” versus a “bead weld”
SPECIALIZATIONS FOR COMMUNICATION
• Cells have to know what’s going on around them
• Tissue function depends on this– Smooth muscle– Cardiac muscle– Glandular epithelium– Many other examples
Gap Junction• Limited area of
plasma membrane• Found in all tissues • Not for adhesion but
for communication• Site of lowered or
variable resistance to passage of ions
• Membrane gap is 20Å or so
• “Pores” on either side
• Cell-to-cell communication
Gap Junctions
NUCLEUS & NUCLEAR ENVELOPE
• “Command & Control” center of cell
• All eukaryotic cells have the entire “blueprint”– MOST of it isn’t used– Degree of
specialization affects how much is accessible
– Physiological state determines appearance
• Broken down & reconstructed each cycle
• Nuclear morphology varies with function & state
• Envelope continuous with RER
• Nuclear envelope & RER are continuous– Ribosomes
found on NE outer surface
• Nuclear pores located at turnbacks of the NE
NUCLEUS NUCLEUS & RER& RER
NUCLEAR PORES
• Openings in nuclear envelope
• Allow passage of RNA
• Complex structure to control movement
NUCLEAR PORES
SYNTHESIS & SECRETION
• MOST cells have some synthetic capability
• SOME cells are specialized for it
• ALL use the same structures to do it– Endoplasmic
reticulum– Golgi apparatus
ENDOPLASMIC RETICULUM
• Two types:– Rough ER functions for protein
synthesis•Described many times from LM studies•EM reveals true nature•Porter coined term in 1950’s
– Smooth ER functions in various ways•Lipid synthesis•Enzymatic degradation pathways•Special role in muscle
RIBOSOME
• Functional unit of RER
• Bound & free types exist– Identical
structure– Large &
small subunits
– Entire ribosome complex about 300Å
ROUGH E.R.• Prominent
feature in secretory cells– Pancreatic cells– Plasma cells– Peptic cells
• Amounts vary with cell function
• Usually some present, may be minor amount
• Accounts for LM visible BASOPHILIA
BASOPHILIA & THE RER
GOLGI APPARATUS• Known since
19th Century– Visible in LM– Nature &
existence debated until 1960’s
• Functions to modify & package products of RER for release
• Camillo Golgi (1843-1926)
GOLGI APPARATUS
GOLGI APPARATUS
• Contains enzymes for attaching carbohydrate & lipid moieties to peptides
SMOOTH ENDOPLASMIC RETICULUM
• Visible only in EM• Prominent in cells
making steroids or lipids– Leydig cells– Luteal cells
• Role in detoxification– Large amounts in
hepatocytes
• Collection of interconnected tubules & vesicles
• Membranous but not “studded” with ribosomes
Summary of function
• Membran sel: eksositosis/endositosis• Mitokondria: energy production• RER:sintesa protein, enzym• SER : sintesa hormon,absorbsi/met lipid• Golgi complec:sintesa protein (ekskresi)• Ribosom: mengolah asam amino• Lysosome:fagositosis• Mikrotubuli: transportasi,kerangka sel,
gerakan sel• Sentriol: pembentuk mikrotubuli/mitosis
Thanks!
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