Cellular and Chemical level of Organisation.pptx

The cellular
and chemical
level of
organization
POONAM BHASKAR
PG - 1st year
Department of PAedodontics
RCDS ,BHOPAL
1

CONTENTS
 Introduction to cell
 History of cell
 Types of cell
 Protoplasm
 Physical structure of cell
 Chemical nature of cell
 Specialized cells of oral cavity
 Conclusion
 References
2

Cell
 Basic structural & functional unit of life.
 Smallest living unit of an organism.
 Grow, reproduce , use energy , adapt & respond to their environment.
 In humans , highly specialized in both structure and function.
 100 trillions or more cells are present in a human being.
4
Guyton & hall.Textbook of medical physiology. 10th edition.elsevier publication

CELL ORIGIN
 4.5 billion years ago - Earth formed
 3.5 billion years ago - 1st life prokaryote
(Bacteria
Dominate)
 1.5 billion years ago - Nucleated cells arise
 0.5 billion years ago - Multicellular
Eukaryotes arise
5
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DISCOVERY OF CELLS
 1665- English Scientist, Robert
Hooke, discovered cells while
looking at a thin slice of cork.
 He described the cells as tiny
boxes or a honeycomb
 He thought that cells only
existed in plants and fungi
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ANTON VAN
LEUWENHOEK
 1673- Used a handmade microscope
to observe pond scum & discovered
single-celled organisms
 He called them “animalcules”
 He also observed blood cells from
fish, birds, frogs, dogs, and humans
 Therefore, it was known that cells
are found in animals as well as
plants
 Father of Microscopy
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DEVELOPMENT OF CELL THEORY
 1838- German Botanist, Matthias Schleiden,
concluded that all plant parts are made of cells
 1839- German physiologist, Theodor Schwann,
who was a close friend of Schleiden, stated that
all animal tissues are composed of cells.
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DEVELOPMENT OF CELL
THEORY
 1858- Rudolf Virchow, German physician, after
extensive study of cellular pathology, concluded
that cells must arise from preexisting cells.
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1. All organisms are composed of one or more
cells. (Schleiden & Schwann)(1838-39)
2. The cell is the basic unit of life in all living
things. (Schleiden & Schwann)(1838-39)
3. All cells are produced by the division of
preexisting cells. (Virchow)(1858)
The 3 Basic Components of the
Cell Theory
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MODERN CELL THEORY
Modern Cell Theory contains 4
statements, in addition to the
original Cell Theory:
1. The cell contains hereditary information
(DNA) which is passed on from cell to cell
during cell division.
2. All cells are basically the same in chemical
composition and metabolic activities.
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3. All basic chemical & physiological
functions are carried out inside the
cells.(movement, digestion etc)
4. Cell activity depends on the activities of
sub-cellular structures within the
cell(organelles, nucleus, plasma membrane)
MODERN CELL THEORY
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MODERN MICROSCOPES
Types
Light microscope (400-1000X)
Electron microscope (1000-
10000X)
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 Light microscope
 Can observe living cells in true color
 Magnification of up to ~1000x
 Resolution ~ 0.2 microns – 0.5 microns
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 Electron Microscopes
 Preparation needs killed microorganisms.
 Images are black and white – may be
colorized
 Magnification up to ~100,000
Transmission electron microscope (TEM)
 2-D image
Scanning electron microscope (SEM)
 3-D image 15
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DIVERSITY OF CELLS
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Two Fundamentally Different
Types of Cells 18
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THE PRESENCE OR ABSENCE OF A NUCLEUS
IS IMPORTANT FOR CLASSIFYING CELLS.
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EUKARYOTIC CELL CAN AGAIN BE
CLASSIFIED AS -
 Unicellular - Yeast, Fungus
 M
 Multicellular- Animal cell,Plant cell
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Guyton & hall.Textbook of medical physiology. 10th edition.elsevier publication. www.google.com

Multicellular - Plant Cell ,Animal cell
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• Structural Differences
– Plants have choloroplasts, a large central
vacuole and a cell wall
– Plant cells do not have centrioles
– Plant cells have plasmodesmata
– Animal cells have gap junctions
• Physiological Differences
– Plant cells have photosynthesis in
addition to respiration
– During mitosis a cell plate is formed in
plant cells
– Starch is molecule for energy storage
while in animal cells it is glycogen
– Large central vacuole stores more water
and carbohydrates then animal cell
vacuoles
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Eukaryotic animal cell parts
Two major
parts :
• Nucleus
• Cytoplasm
24

PROTOPLASM
 Different substances that make up the cell
are called PROTOPLASM.
 Includes – 1. water
2. electrolytes/ions
3. proteins
4. lipids
5. carbohydrates
25

1. WATER
• Principal fluid medium of cell.
• Conc. – 70-80% in most cells
• Cellular chemicals either
dissolve or suspend as
particulates in water.
• Chemical reactions take
place among them.
26

2. ELECTROLYTES AND IONS
•Imp. Ions are - K⁺ , Mg⁺⁺ ,
HCO³⁻, PO₄²⁻, SO₄²⁻
•In small amount – Na⁺ , Cl⁻, Ca²⁺
•Provide inorganic chemicals
for cellular reactions
27

3. PROTEINS
 10 – 20 % of cell mass.
 2 types : A) Structural proteins
B) Globular proteins
28

STRUCTURAL PROTEINS
Present in the form of long thin filaments .
Major use – contractile mechanism
of all muscles
 Other types organised into
microtubules – provide the “cytoskeleton “.
Extracellulary – collagen & elastic fibers
in C.T.
29

GLOBULAR PROTEINS
 Composed of individual protein molecules or
combination of few molecules in globular form.
 They are mainly “enzymes of the cell.
 As enzymes they come in contact with other
substances in cell fluid and catalyze reactions.
30

4. LIPIDS
 Constitute 2% of cell mass .
 Soluble in fat solvents.
 Imp. Lipids are – phospholipids
cholesterol
 Some cells in addition also contains large
amount of triglycerides /neutral fat ( fat cells )
 Fat cells – main store house of energy giving
nutrient.
31

5. CARBOHYDRATES
• Main nutritive & little structural function.
• Present as – dissolved “ glucose “ in ECF.
insoluble “ glycogen “ within cell
32

PHYSICAL STRUCTURE OF THE CELL
Membranous Structures Of The Cell :
Membranes within cell include:
1. Cell membrane/ plasma membrane .
2. Nuclear membrane.
3. Membrane of ER.
4. Membrane of mitochondria.
5. Membrane of GA.
6. Membrane of lysosomes , secretory vesicles
33

 Membranes are made up of both lipids and
proteins
 Selectively permeable/ semi permeable.
 Provides communication within the cell and with
external environment
34

CELL MEMBRANE/PLASMA MEMBRANE
 In 1972, S.J. Singer & G. Nicolson
proposed the “ FLUID MOSAIC “ model to
describe the structure of cell membrane
Outside
of cell
Inside
of cell
(cytoplasm)
Cell
membrane
Proteins
Protein
channel Lipid bilayer
Carbohydrate
chains
35

OVERVIEW
 Cell membrane separates living cell from
nonliving surroundings
thin barrier = 7.5-10 nm thick.
Pliable , elastic sructure.
 Controls traffic in & out of the cell
selectively permeable
allows some substances to cross more
easily than others.
Self seal if punctured. 36

APPROXIMATE COMPOSITION
 Proteins – 55%
 Phospholipids – 25%
 Cholesterol – 13%
 Other lipids – 4%
 Carbohydrates – 3%
37

38

CELL MEMBRANE LIPIDS-
 Basic structure – lipid bilayer
 Composed of phospholipids –
phosphatidylcholine &
phosphatidylethanolamine.
 In addition also contains – glycosphingolipids,
sphingomyelin & cholesterol.
 Lipid bilayer – fluid not a solid
39

Phospholipid Bilayer
• Lipids
– Organic compounds
– Fats + Oils
– Non-polar
– Insoluble in water (Not attracted to
water)
Phosphate Head
– Polar
– Water-soluble (Attracted to water)
Phosphate
Group
Glycerol
Backbone
Here is what a phospholipid
bi-layer looks like as a sphere
FATTY
ACIDS
POLARHE
AD
40

ROLE OF CHOLESTEROL MOLECULE
 Degree of permeability of lipid bilayer to
water soluble constituents.
 Controls the fluidity of membrane .
 At normal body temp. – provides strength.
 At low temperature – becomes fluid
41

CELL MEMBRANE PROTEINS
 Present as globular masses.
 Mainly “ glycoproteins “.
 2 types –
peripheral proteins
Located on the outer surface of the membranes.
integral proteins
Located in the inner surface of the membrane .
Transmembrane proteins
Extending through the membrane.
42

FUNCTIONS OF PROTEINS
 Intrinsic proteins serve mainly as
“enzymes.”
 Extrinsic proteins contribute to the
cytoskeleton ( framework of the cell).
 Transmembrane proteins serve as :
a) Channels
b) Carriers
c) Pumps
d) Receptors
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1 – ION CHANNELS /PORES
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2- CARRIER MOLECULES
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CELL MEMBRANE CARBOHYDRATES – THE
CELL “GLYCOCALYX”
 Present in form of – glycoproteins
( integral proteins ) or
as glycolipids ( abt. ¹⁄₁₀th lipids )
 The glyco portion protrudes
outside of the cell – forms a
loose CBH coat “ glycocalyx”.
48

FUNCTIONS
 1- Play a key role in cell-cell recognition.
 2- acts as receptor substances.
 3- electrically negatively charged hence repels negative
objects .
 4-helps in attachment of cells to one another.
 5-basis for rejection of foreign cells by immune system.
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Transport Across Membranes
50

 Passive Transport
 Simple diffusion
 diffusion of nonpolar, hydrophobic molecules
 lipids
 high  low concentration gradient
 Facilitated transport
 diffusion of polar, hydrophilic molecules
 through a protein channel
 high  low concentration gradient
 Active transport
 diffusion against concentration gradient
 low  high
 uses a protein pump
 requires ATP
51

Transport Across Membranes: PASSIVE
DIFFUSION
The movement of molecules or ions from a region
where they are at a high concentration to a region of
lower concentration
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• Gases (oxygen, carbon
dioxide)
• Water molecules (rate
slow due to polarity)
• Lipids (steroid
hormones)
• Lipid soluble molecules
(hydrocarbons,
alcohols, some
vitamins)
• Small noncharged
molecules (NH3)
SIMPLE DIFFUSION
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• Ions
(Na+, K+, Cl-)
• Sugars (Glucose)
• Amino Acids
• Small water soluble
molecules
• Water (faster rate)
FACILITATED DIFFUSION
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– Osmosis is the diffusion of water across a differentially
permeable membrane.
– Osmotic pressure is the pressure that develops in a
system due to osmosis.
OSMOSIS
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ACTIVE TRANSPORT
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Endocytosis
Vesicles form as a way to transport molecules into
a cell
a. Phagocytosis
Large,particulate matter (Bacteria, viruses, and
aged or dead cells).
b. Pinocytosis
Liquids and small particles dissolved in liquid
58

Exocytosis
Vesicles form as a way to transport
molecules out of a cell
59

Cytoplasm & Its Organelles
2 main components –
a.Cytosol
b.Organelles
60
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CYTOSOL :
 The clear fluid portion of the cytoplasm in
which the particles are dispersed is called
cytosol.
 Known as intracellular fluid or cytoplasmic
matrix.
 In eukaryotes this liquid is seperated by
membranes from the content of the
organelles.
 It is a complex mixture of substances
dissolved in water (75-90% ).
61

ORGANELLES PRESENT
1- mitochondria
2- endoplasmic reticulum
3- ribosomes
4-golgi apparatus
5-lysossomes
6-peroxisomes
7-cytoskeleton
62

Mitochondria
POWERHOUSE OF THE CELL
63
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 Sausage shaped organelle.
 Composed of 2 lipid bilayer-
protein membrane.
 Inner membrane has foldings
to form shelves called cristae
 Contain DNA –double
stranded circular molecule
containing approx. 16,500
base pairs.
64

MITOCHONDRIAL DNA
 Maternal inheritance.
 Responsible for certain key components of
the pathway for oxidative phosphorylation.
 Ineffective DNA repair system.
 Mutation rate 10 times more than n DNA.
65

The Functions of
mitochondrion
•Production of ATP through
oxidative phosphorylation
•Cofactor in krebs cycle.
•Calcium ion storage.
•Apoptosis
66

ATP BIOSYNTHESIS
Guyton & hall.Textbook of medical physiology. 10th edition.elsevier publication 67

2- ENDOPLASMIC RETICULUM
68
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STRUCTURE
69
 Complex series of tubules
and flat vesicular
structures ,interconnecting
with one another.
 Tubule walls are made up
of lipid bilayer containing
large amount of proteins.
 Space inside ER is
connected with the space
between the two
membrane surfaces of the
nuclear membrane.

TYPES :
 A) RER/Rough ER/ Granular ER
 B) SER/Smooth ER/Agranular ER
70

FUNCTIONS
A) Rough ER :
 Protein synthesis- glycoproteins
 Also produces secretory , membrane &
organelle proteins
 Initial folding of polypeptide chains with
disulfide bond formation.
71

B) SMOOTH ER
 Synthesis of lipids & steroids.
 Metabolism of carbohydrates.
 Regulation of calcium concentration – as
sarcoplamic reticulum in muscles .
 Drug detoxification.
 Attachment of receptors on cell membrane
proteins.
 Steroid metabolism
72

3- RIBOSOMES
73
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Structure :
 Composed of mixture of RNA & proteins.
 approx. – 22*32nm
 Made up of 2 subunits :
 larger subunit – 60 ‘S’
 Smaller subunit– 40 ‘S
74

Types :
A) Attached to ER
B) Free ribosomes
75

FUNCTIONS –
 Attached ribosomes – synthesize
proteins mainly transmembrane proteins ,
secreted proteins, proteins stored in golgi
apparatus, lysosomes & endososmes.
 Free ribosomes – synthesize
cytoplasmic proteins like Hb & proteins
stored in peroxisomes & mitochondria
76

4-GOLGI APPARATUS/COMPLEX/BODY
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Structure –
Composed of stacks of membrane bound
structures known as cisternae.
Usually 6-7 cisternae present.
Polarised structure .
Cisternae has 2 sides – cis side & trans side
79

Functions –
 A) Modifying , sorting & packaging of
macromolecules for cell secretion or use
within cell
80

After modification proteins are released in 2
forms –
1. Secretory vesicles & lysosomes - fuse with cell
membrane & empty their substances to the exterior
( endocytosis ).
2. Intracellular vesicles – fuse with the membranes of
other organelles & thereby increases the expanse
of these membranes
81

Synthetic functions of GA –
 Synthesizes certain CBH’s that cannot be formed by ER.
 Synthesizes large polysaccharide molecules bound with
small amt. of proteins- HYALURONIC ACID &
CHONDROITIN SULFATE
82

5- LYSOSOMES
83
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Structure –
 Vesicular organelles budding off from GA.
 Ard. 250-750 nm dia.
 Surronded by lipid bilayer membrane.
 Filled with granules ard 5-8 nm dia.
 Granules are protein aggregates of as many as
40 different hydrolase (digestive) enzymes
84

 Interior is more acidic than rest of the
cytoplasm due to the action of Proton
Pump or H⁺ , ATPase.
 Hydrolytic enzymes present are capable
of splitting an organic compound into 2 or
more parts.
substances Hydrolysed
into
Proteins Amino acids
glycogen Glucose
lipids Fatty acids & glycerol
85

 Enzymes present in lysosomes
86
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Functions –
 Provides intracellular digestive system
87

 A) digest unwanted matter such as bacteria
88

 Digest cellular structures
89

 C) digest food particles that have been
ingested by cell
90

 Lysososmal storage diseases –
when lysosomal enzymes are congenitally
absent , the lysosome become engorged with
the material that the enzymes normally
degrades leading to lysosomal storage disorders
91

Disease Enzyme deficient
Fabry’s ds. Α galactosidase A
Gaucher’s ds. Β galactocerebrosidase
Niemann pick ds. sphingomyelinase
Krabb’s ds. galactocerebrosidase
Tay sach’s ds. Hexosaminidase A
Pompe’s ds. Acid malatase
Metachromatic leuco dystrophy Aryl sulfatase A
92

6- PEROXISOMES
93
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 Structure similar to lysososmes.
 Ard. 0.5 µm in dia. surronded by
membrane
94

 Peroxisomes contain enzymes like oxidases &
catalases which can either produce hydrogen
peroxide or break it down.
 Matrix contains - >40 enzymes which along with
other enzymes catalyze a variety of anabolic &
catabolic rxnz.
 Peroxisome membrane contains no. of
peroxisome specific proteins – concerned with
transport of substances in & out of the matrix
95

FUNCTIONS -
 They participate in the metabolism of fatty acids
and many other metabolites.
 Peroxisomes harbor enzymes that rid the cell of
toxic peroxides.
 Import proteins into the organelles and aid in
proliferation.
 Peroxisomes also play a role in the production of
bile acids and proteins
96

PEROXINS -
 Protein chaperons , which acts as unique
signal sequence , to direct proteins to
peroxisomes.
97

7- CYTOSKELETON
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 System of fibers .
 Maintains the structure of cell; also permits
the cell to change shape and move.
 Made up of – a) microtubules
b) intermediate filaments
c) microfilaments
99

A) MICROTUBULES-
 Structure –
 Long hollow structures
 15nm dia. Cavity surrounded by 5 nm wall.
 Made up of 2 globular protein – 1) α tubulin
 2)b tubulin
100

 Interaction with GTP required for formation.
 Polar structure – assembly at ‘+’ end &
disassembly at ‘-’ end .
 Because of constant assembly and
disassembly – dynamic portion of cell
skeleton.
101

FUNCTIONS -
 Provide tracks along which different molecular
motors move transport vesicles , organelles like
secretory granules , mitochondria from 1 part of
cell to another.
102

 Forms spindles which move the
chromosomes in mitosis.
103

CLINICAL IMPORTANCE -
 Several drugs disrupts cellular function thru
interaction with microtubules.
 Eg: Colchicine & vinblastin – prevents assembly
of microtubules.
 Paclitaxel ( Taxol ) – binds with microtubules &
makes it stable mitotic spindles are not formed
cell dies .
104

B) INTERMEDIATE FILAMENTS
 8-14 nm dia.
 Made up of various subunits.
 Proteins that make them up are cell specific
therefore used as “cell markers”.
 Forms flexible scaffolding for cells.
 Helps the cell to resist external pressure.
 Absence – cells rupture easily.
 Abnormal – blistering of skin .
105

C) MICROFILAMENTS
 Long solid fibers 4-6 nm dia.
 Made up of actin subunits .
 2 types – filamentous (F) actin – intact microfilaments
 globular (G) actin – unpolymerized.
106

FUNCTIONS -
 Maintains cell shape by resisting tension ( pull).
 Moves cells via muscle contraction or cell crawling.
 Moves organelles and cytoplasm in plants , fungi and
animals .
107

CENTROSOMES -
 Present near the nucleus in cytoplasm.
 Made up of – 2 centrioles & surronding amorphous
pericentriolar material.
 Small cylinders at right angles to each other.
108

 Centrioles are made up of microtubules which
are present in group of 3 , run longitudinally in
the walls of each centriole & 9 such triplets are
present around the circumference.
109

NUCLEUS
110
BRAIN OF THE CELL
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 Control centre/ brain of the cell.
Structure 1) nuclear envelopemembrane
2) nuclear pore complexes
3) nucleolus
4) chromatin & genes
111

1- NUCLEAR ENVELOPE/ MEMBRANE
 Surronds the nucleus .
 Double membrane – outer membrane continous with ER.
 Spaces b/w 2 folds – perinuclear cisterns/space.
 Permeable to only small molecules.
112

2- NUCLEAR PORE COMPLEXES
 8 fold symmetry; abt 9 nm in dia.
 Made up of abt. 100 proteins organised to form a tunnel thru
which transport of proteins & mRNA occurs.
 Proteins importins & exportins have been identified for transport
pathways.
113

3- NUCLEOLUS
 Patchwork of granules rich in RNA & proteins.
 May be 1 or more.
 Most prominent and numerous in growing cells.
 Site of synthesis of ribosomes.
114

4 – CHROMATIN
 Nucleus is made up of large part of CHROMOSOMES
– giant molecule of DNA.
 DNA strand is abt 2mm long, but can fit in as it is
wrapped ard. a core of histone proteins to form
NUCLEOSOME at intervals.
115

 Abt. 25 million nucleosome present in each nucleus .
 Thus, chromosomes appear as strings of beads.
 Beads – nucleosome
 Strings – linker DNA chromatin ( DNA & proteins )
116

 Chromosomes – complete blueprint for all the
heritable species & indivual characteristics of
animals.
 Paired ; except in germ cells.
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GENES
 Portion of DNA molecule.
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 Ultimate unit of heredity.
 DNA is used for specific protein synthesis.
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PROTEIN SYNTHESIS
Transcription ( DNA RNA )
Translation ( RNA Proteins)
Proteins
121

THE BODY AS AN ORGANIZED
“SOLUTION”
In an average young adult male –
123
Body wt. % Substance
18% Proteins & related
substances
7% minerals
15% fat
60% Water ( fluid)
Guyton & hall.Textbook of medical physiology. 10th edition.elsevier publication Kim E. Barret , Susan M. Barman,Scott
Boitano.Ganong’s review of medical physiology .24th edition.Lange basic science.

WATER -
Because of high surface tension, high heat
capacity & high electrical capacity – ideal
solvent.
124
Guyton & hall.Textbook of medical physiology. 10th edition.elsevier publication Kim E. Barret , Susan M.
Barman,Scott Boitano.Ganong’s review of medical physiology .24th edition.Lange basic science.

60%
Water(fluid )
20% body wt.
ECF
15% body wt./
75% ECF
Interstitial fluid
5% body
wt./25% ECF
Blood Plasma
40% body wt.
ICF
125
Kim E. Barret , Susan M. Barman,Scott Boitano.Ganong’s review of medical physiology .24th edition.Lange basic science

126

Total body water
1/3rd extracellular 2/3rd intracellular
 All cells live in essentially same environment –
the ECF. Therefore ECF is called the
“ internal environment” of body or “milieu
interieur” ( term by Claude Bernard ) .
127
Guyton & hall.Textbook of medical physiology. 10th edition.elsevier publication Kim E. Barret , Susan M.
Barman,ScottBoitano.Ganong’s review of medical physiology .24th edition.Lange basic science.

 Difference b/w ECF & ICF –
 ECF – contains large amt. of Na+, Cl¯,
HCO³¯
nutrients like glucose , O2 , AA’s,
FA’s, waste products & CO2.
 ICF – contains large amt. of K⁺ , Mg²⁺ , PO₄¯
 This difference in ion concentration
maintained by special mechanisms for
transporting ions through the cell membranes
(Na⁺- K⁺ ATPase)
128

Some imp. Constituents & physical characteristics of
ECF ,the normal range of control & approx. non- lethal
limits for short periods -
129
constituent Normal value Normal range Approx. non
lethal limits
units
oxygen 40 35-45 10-1000 mmHg
CO2 40 35-45 5-80 mmHg
Na⁺ 142 138-146 115-175 mmol/L
K⁺ 4.2 3.8-5.0 1.5-9.0 Mmol/L

Ca²⁺ 1.2 1.0-1.4 0.5-2.0 mmol/L
Cl¯ 108 103-112 70-130 mmol/L
HCO₃¯ 28 24-32 8-45 mmol/L
glucose 85 75-95 20-1500 mg/dl
Body
temperat
ure
98.4(37) 98.0-98.8 65-110
(18.3-
43.3 )
ºF ( ºC)
Acid –
base
7.4 7.3-7.5 6.9-8.0 pH
130

• K⁺ ions –
when conc. decrease - paralysis
when conc. increase - depresses heart
muscles
 Ca²⁺ -
when conc. decrease - tetanic conc. Of
muscles all
through out the body.
 Glucose –
when conc. Falls – extreme mental
irritability & sometimes
convulsions.
131

Thus , most important are the limits of
concentrations beyond which a vicious circle
of increasing cellular metabolism starts that
literally destroys the cell.
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132

Life span of selected human cells
.Granulocytes -- 10 hours to 3 days
.Stomach lining cells -- 2 days
.Sperm cells -- 2-3 days
.Colon cells -- 3-4 days
.Epithelia of small intestine -- 1 week or less
.Platelets -- 10 days
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•Skin epidermal cells -- 2 - 4 weeks
•Lymphocytes -- 2 months - a year
•Red blood cells -- 4 months
•Stomach lining cells -- 2 days
•Macrophages -- months - years
•Endothelial cells -- months - years
•Pancreas cells -- 1 year or more
•Bone Cells -- 25 - 30 year
www.google.com 134

CELLS OF THE SPECIALISED TISSUE
Kidneys :
Various distinct cell types are seen as when structure of kidney
is viewed under microscope :
 Kidney glomerulus parietal cell
 Kidney glomerulus podocyte
 Kidney proximal tubule brush border cell
 Loop of Henle thin segment cell
 Thick ascending limb cell
 Kidney distal tubule cell
 Kidney collecting duct cell
 Interstitial kidney cells
135
B. Sivapathasundharam Shafer’s textbook of Oral Pathology .7th edition.Elsevier.

Brain cells :
 The brains of all species
are composed primarily of
two broad classes of
cells: neurons and glial
cells. Glial cells (also
known as glia or neuroglia)
come in several types, and
perform a number of
critical functions, including
structural support,
metabolic support,
insulation, and guidance of
development.
136
www.google.com

Heart cells or Cardiac muscle
cell :
 There are two types of cells within
the heart: the cardiomyocytes and
the cardiac pacemaker cells.
 Cardiomyocytes make up
the atria (the chamber in which
blood enters the heart)
and ventricles (where blood is
pumped out of the heart) of the
heart.
 Cardiac pacemaker cells carry the
impulses that are responsible for
the beating of the heart.
137
www.google.com B. Sivapathasundharam Shafer’s textbook of Oral Pathology .7th edition.Elsevier

Liver cells
 A hepatocyte is a cell of the main
tissue of the liver. Hepatocytes
make up 70-85% of the
liver's cytoplasmic mass. These
cells are involved in:
 Protein synthesis
 Protein storage
 Transformation of carbohydrates
 Synthesis of cholesterol, bile
salts and phospholipids
 Detoxification, modification, and
excretion of exogenous and
endogenous substances
 The hepatocyte also initiates
formation and secretion of bile.
138
www.google.com B. Sivapathasundharam Shafer’s textbook of Oral Pathology .7th edition.Elsevier

SPECIALISED CELLS OF THE ORAL
CAVITY
139
S.N Bhaskar.Orban’s Oral histology & Embryology.11th edition.Mosby publication

CLASSIFICATION OF CELLS ON THE BASIS
OF ORIGIN
From ectoderm - OMM
Enamel
Dentin
Mesoderm – Pulp
Cementum
Periodontal ligament
Alveolar bone
140

1- AMELOBLASTS
 Cells forming the enamel.
141

Structure –
 polarized , tall columnar cells.
 4-5 µm in dia. ; 40 µm in length.
 hexagonal in cross section.
 secretory end is a six sided pyramid like projection
k/w as TOME’S PROCESSES.
142

Functions –
 Control ionic & organic composition of
enamel.
 Secretory ameloblasts - Secretes
enamel proteins enamelin & amelogenin
which later mineralizes to form enamel.
 Transitional ameloblasts – resorption
of enamel matrix proteins ( lysososmal
enzymes)
 Maturation ameloblasts-massive
influx of minerals calcium and
phosphates & selective loss of enamel
proteins & water.
143

CLINICAL CONSIDERATIONS-
ENAMEL HYPOPLASIA
144
www.google.com

2- ODONTOBLASTS
 Cells forming dentin .
 Most specialized cells of dentin pulp complex.
146

STRUCTURE -
 Form a layer lining the periphery of the pulp .
 Cell bodies from crown to cervix to root apex.
 Cell bodies are columnar in crown portion, cuboidal in
mid portion of the pulp, and flattened in apical part.
147

 Polarized cell – nucleus aligned away from newly
formed dentin.
 Nucleus – large with upto 4 nucleoli.
 cell rich in RER , mitochondria, golgi complex.
148

ODONTOBLASTIC PROCESSES
 One or more several processes arise from the
apical end of the cell in contact with the basal
lamina to form odontoblastic processes.
 These processes form dentinal tubules.
149

FUNCTIONS OF ODONTOBLASTS -
 Aids in secretion of intertubular & peritubular dentin.
 General maintainence of both dentinal fluid & tubules.
 Secretes sclerotic dentin , secondary dentin , reactionary
dentin.
 Secretes proteins required for mineralization - dentin
phosphoprotein ( DPP) osteonectin , osteopontin , gla protein
, proteoglycans .
150

 also secretes phosphophoryn ( unique to
dentin )
 synthesizes type I collagen ; small amt. of
type V.
 also secretes acid phosphatase & alkaline
phosphatase .
151

3- ODONTOCLASTS
 Cells responsible for removal of dental
hard tissue.
 Origin – derived from tartarate resistant
acid phosphatase ( TRAP) positive
circulating monocytes.
152
B. Sivapathasundharam Shafer’s textbook of Oral Pathology .7th edition.Elsevier

STRUCTURE
 Large multinucleated cells.
 Occupies resorption bays on surface of dental hard tissue.
 Cytoplasm vacuolated with high mitochondrial content.
 Surface of cell adjacent to resorbing hard tissue forms “
ruffled” border .
 Ruffled border – extensive folding of cell membrane into
series of invaginations 2 to 3 µm deep.
153

 Adjacent to ruffled border clear zone – in which the
cytoplasm is devoid of organelle but rich in filaments
consisting of contractile proteins actin & myosin.
154

CLINICAL CONSIDERATION -
155
Dentinogenesi
s Imperfecta
www.google.com

4- CELLS OF THE PULP
Include–
A) Fibroblasts
B) Undifferentiated ectomesenchymal cells / pulpal stem cells.
C) defence cells
D) Odontoblasts
156

FIBROBLASTS -
 Most numerous cells of pulp.
 Found more in the coronal portion of pulp which forms
the cell rich zone.
 Tissue specific cells capable of giving rise to cells that
are committed to differentiation if given proper signals.
157

Structure –
 Young pulp – stellate shape with extensive processes.
have abundant of RER , mitochondria,GA enlarges ,
secretory vesicles appear.
 Older pulp – rounded or spindle shaped with short
processes & less organelles, more fibers then termed as
“Fibrocytes”.
158

FUNCTIONS -
 Dual action – synthesis & degradation of pulp
matrix both.
 Role in inflammation – release inflammatory
mediators like cytokines , growth factors.
 Helps in healing – by secreting angiogenic
factors like FGF-2 & VEGF.
159

UNDIFFERENTIATED
ECTOMESENCHYMAL CELLS
 Primary cells in young pulp.
 Larger than fibroblasts.
 Polyhedral in shape with peripheral processes.
 Large oval nuclei.
 Lack RER.
 Found along the pulp vessels ;
in cell rich zone & scattered
throughout the central pulp.
 No. decreases with age.
160

FUNCTION -
 Represents the pool from which connective
tissue cells of the pulp are derived.
 Totipotent cells – can give rise to
odontoblasts , fibroblasts , macrophages
when required .
161

 Dentonin, a peptide from matrix
extracellular phosphoglycoprotein –
stimulate pulp stem cells.
 Growth factors like – TGF beta 1 & BMP
-2 involved in proliferation &
differentiation.
162

DEFENSE CELLS -
163
Includes – 1. histiocytes /
macrophages
2. dendritic cells
3. lymphocytes
4. mast cells
5. plasma cells

HISTIOCYTES/ MACROPHAGES
 They are monocytes that have left bloodstream & entered the tissue.
 Irregularly shaped cells with short blunt processes.
 Contains moderately dense nucleus, RER, mitochondria , free ribosomes.
 Differentiated into various subpopulations.
 A major subpopulation – active in endocytosis & phagocytosis – act as
scavengers , removing extravasated RBC’s , dead cells & foreign bodies from
tissues.
 Another subpopulation – participates in immune rxns by processing antigen &
presenting it to memory T- cells.
164

 Another subpopulation – express lymphatic markers ,
indicating link between macrophages & lymphatic
function and development.
( characterization of the dental lymphatic system & identification of cells immunopositive to
specific lympathic markers – by Berggreen E.Haug , SR Mkony , Blesta A. - Eur J oral sci
2009 )
165

DENDRITIC CELLS/ ANTIGEN PRESENTING
CELLS
 Accessory cells of the immune system.
 Found in close relation to & in contact with cell membranes
of endothelial cells.
 Characterized by dendritic cytoplasmic processes &
presence of class II MHC complexes on their cell surface.
166

 In deciduous teeth – closely associated with
odontoblasts ; no. increases in areas affected by
caries , restorative procedures .
 No. also increases during shedding.
167

Function –
induction of T – cell immunity .
168

LYMPHOCYTES -
 Mainly T- lymphocytes found .
 T8( suppressor) lymphocytes are predominate.
 Found extravascularly in normal pulp.
 No. increases in inflammation.
169

MAST CELLS
 Seldom found in normal pulp.
 Routinely seen in inflamed pulp.
 Have round nucleus ; many dark staining granules in
cytoplasm.
 Granules contain heparin , & histamine as well as many
chemical mediators.
170

PLASMA CELLS
 Seen during pulpal inflammation .
 Nucleus – cartwheel appearance ( chromatin is adherent with nuclear
membrane )
 Cytoplasm – basophilic , golgi zone adjacent to nucleus, densely
packed RER.
 Function –
production of antibodies.
171

5 – CEMENTOBLASTS
 Cells responsible for cementogenesis .
172

Structure –
 Polygonal to cuboidal in shape.
 Large vesicular nucleus with 1 or more nucleoli.
 Numerous mitochondria , well formed GA , RER.
173

 Cells get entrapped in the lacunae of their own matrix –
CEMENTOCYTES.
 Lacunae have canals or canaliculi – oriented toward the
PDL & contains cementocytic processes .
174

Function –
 Synthesize collagen & protein polysaccharides –
organic matrix of cementum.
 For Differentiation into
cementoblasts–
 Growth factors like TGF β , BMP , transcription factor
core binding factor α1 , signalling molecule EGF
involved .
 PG’s E(2) & F (2α) – enhance differentiation by
activating protein kinase signalling pathway.
175

CLINICAL CONSIDERATION
HYPERCEMENTOSIS
176

PERIODONTAL LIGAMENT CELLS
177

Can be divided into –
• 1- Synthetic cells - fibroblasts
osteoblasts
cementoblasts
• 2- Resorptive cells – fibroblasts
osteoclasts
cementoclasts
• 3- Progenitor cells
• 4- epithelial cells – epithelial rests of malassez
• 5- defense cells – mast cells
macrophages
eosinophils
178

PROGENITOR CELLS
 Cells that have the capacity to undergo mitosis &
form synthetic cells.
 Highest in concentration in location adjacent to blood
vessels.
 Small, close faced nucleus & very little cytoplasm.
179

EPITHELIAL RESTS OF MALASSEZ
 Cuboidal cells.
 Prominent nucleus ; stains deeply.
 Scanty cytoplasm.
 Mitochondria present.
 RER & GA poorly developed.
180

Includes – Osteoblasts
Bone lining cells
Osteocytes
Osteoclasts
182

OSTEOBLASTS
 Mononucleated cells .
 Origin –
undifferentiated pluripotent stromal cells
inducible osteoprogenitor cells ( IOPC’s)
BMP’s , Growth factors
Determined osteoprogenitor cells (DOPC’s)
Systemic & bone derived GF’s
Osteoblasts
Cbfa1( osteoblast specific
transcription factor )
Bone formation
183

Morphology –
• Basophilic , plump cuboidal or slightly
elongated cells .
• Found on the forming surfaces of
growing or remodelling bone.
• Abundant RER & Golgi complex.
184

• Nucleus is situated eccentrically in the
part of cell farthest away from adjacent
bone surface.
• Contain prominent bundles of actin ,
myosin & cytoskeletal protein.
185

Functions –
1 . Formation of new bone via synthesis
of various proteins & polysaccharides .
2. Regulation of bone remodelling &
mineral metabolism .
3.Secrete type I collagen & small amt. of
type V (osteoid).
4. Mineralization of osteoid.
186

OSTEOCYTES
 Osteoblasts entrapped within the matrix they
secrete – OSTEOCYTES.
 No. of osteoblasts that become osteocytes
depend on rapidity of bone formation.
187

 Within the bone matrix – osteocytes
reduce in size , creates a space around
it – osteocytic lacuna.
 Lacunae- ovoid or flatened.
 From lacunae narrow extensions arise –
canaliculi .
188

 Osteocytic processes are present within the canaliculi.
 These processes – bundles of microfilaments & some
SER.
 At distal end ,these processes contact the processes of
adjacent osteocytes.
 Canaliculi penetrate the bone matrix & permit diffusion of
nutrients , gases and waste products b/w osteocytes &
blood vessels.
189

OSTEOCLASTS -
Morphology –
 Large cell approx. 40-100μm in dia. With
ruffled border.
 15-20 closely packed nuclei.
 Variable in shape due to motility.
190

 Extensive mitochondria & golgi complex.
 RER sparse.
 Cathepsin containing vesicles & vacoules
present near ruffled border.
 Lies in resorption bays called “Howship’s
Lacunae”.
191

Function – removes the bone tissue by
removing the mineralized matrix of
bone.
192

CELLS OF ORAL MUCOUS MEMBRANE
Cells of OMM
Non-
keratinocytes
melanocytes
Langerhans
cells
keratinocytes Merkel cells
193

KERATINOCYTES
 Epithelial cells that ultimately keratinize .
 Show cell division, undergo maturation & finally desquamate .
 Increase in volume in each successive layer from basal to granular .
 The cells of each successive layer cover a larger area than do the
layers immediately below.
194

Stratum basale –
 single layer of cuboidal cells.
 show ribosomes & RER .
 synthesize DNA & undergo mitosis.
 Basal cells are made up of 2 populations –
1. Serrated & heavily packed with tonofilaments.
2. Non serrated & composed of slowly cycling stem cells .
195

Stratum spinosum
 Cells are irregularly polyhederal & larger than
basal cells.
 Cells are joined by “intercellular bridges”.
 More active in protein synthesis.
196

Stratum granulosum
 Flatter & wider cells .
 Larger than spinous cell layer.
 Basophilic keratohyaline granules.
 Nuclei shows sign of degradation & pyknosis
197

Stratum corneum
 Keratinized squamae ; larger & flatter than granular cells .
 Nuclei & other organelles like ribosomes & mitochondria
disappeared.
 Acidophilic .
 Keratohyaline granules disappeared.
 Cells contain densely packed filaments , altered & coated
by keratohyaline granule , filaggrin.
198

NON-KERATINOCYTES
 Make up 10% cell population.
 Also k/w as “clear cells”.
Includes-
1) Melanocytes
2) Langerhans cells
3) Merkel cells
4) Inflammatory cells
199

200
function
s
Pigment containing
cells which give
brownish hue to
the gingiva.
Immunologic
function of
recognising &
processing antigenic
material and
presenting it to T –
lymphocytes.
granules release
transmitter across
the synapse.
Sensory and
respond to touch.

INFLAMMATORY CELLS
 Include lymphocytes commonly; PMNL’s & mast cells also
seen.
 Found at various levels of epithelium.
 Usually seen associated with langerhans cells.
 A few inflammmatory cells can be considered as normal
component of oral mucosa.
201

TASTE BUDS
 Taste buds are sensory organs that are found on tongue
and allow us to experience tastes that are sweet, salty,
sour, and bitter
 The sense of taste called gustation.
 Around 100 taste buds are present in a papilla.
202

Location of Taste Buds
Taste buds contains
sensory receptors found
in the papillae of tongue
and widely distributed in
the epithelium of tongue,
soft palate, pharynx and
epiglottis.
203

STRUCTURE OF TASTE BUDS
 Oval barrel shape 70um*50um.
 Life span- 10 days
 Having opening called taste
pores
 Composed of 5-15 gustatory
receptors cell, 40 supporting
cells or subtentacular cell and
15-20 transitional cells.
204

ELECTRON MICROSCOPIC STRUCTURE
OF TASTE BUDS
205

SALIVARY GLAND CELLS
 Compound exocrine glands
secreting saliva; with ductal and
acinar portions.
 Basic functional unit of salivary
gland is the terminal secretory
unit called ACINI .
 These acini are made up of
epithelial secretory cells , namely
serous cells & mucous cells .
206

 Glandular secretory cells :
1. Serous cells
2. Mucous cells
 Myoepithelial cells: ( contractile
cells)
 Supporting connective tissue
stroma:
1. Fibroblasts ( produce collagen).
2. Fat cells.
3. Plasma cells (produce 207

SEROUS CELLS
 Pyramidal cells -broad base
on basement membrane &
apex faces lumen.
 Spherical nucleus at basal
region.
 Structural feature – typical
protein secreting cell.
 Apical cytoplasm shows
accumulation of secretory
granules.
208

 Granules are zymogen granules
– formed by glycolated proteins
which are released into a
vacoule.
 Show acid phosphates,
esterases, glucuronidase ,
glucosidase & galactosidase
activity.
 Produce proteins and
glycoproteins.
209

 Their watery secretion contains enzymes (amylase, lysozyme),
IgA secretory piece and lactoferrin (iron binding compound).
 The parotid glands are composed entirely of
serous glands.
210

MUCOUS CELLS
 Elongated pyramidal cells
with pale vacuolated
cytoplasm basally located
nuclei.
 Cell shows accumulation of
large amount of secretory
products at apical
cytoplasm.
211

 RER , mitochondria &
other organelle are
located in a narrow band
of cytoplasm along the
base & lateral border of
the cell.
 Golgi apparatus is large
sandwiched between
basal RER & mucous
droplets .
212

 Produce low proteins high in
carbohydrates (mucin).
 ONLY THE PALATINE AND LATERAL
LINGUAL GLANDS ARE ENTIRELY
MUCUS-SECRETING.
213

 PAROTID-serous
 SUBMANDIBULAR -
mixed serous/mucous
 SUBLINGUAL-
mucous/demilunes
214

MYOEPITHELIAL CELLS
 Stellate or spider like cells .
 Flattened nucleus .
 Scanty perinuclear cytoplasm
& long branching processes
that embrace the secretory &
duct cells.
215

 Appearance is reminiscent of a basket cradling the
secretory unit – “basket cells”.
 Contain cytokeratin intermediate filaments & contractile
actin filaments .
 Found around acini and intercalated ducts.
216

FUNCTIONS -
1. Accelerate the initial outflow of saliva from the acini.
2. Reduce luminal volume .
3. Contribute to secretory pressure in acini or duct.
4. Support the underlying parenchyma & reduce the back
permeation of fluid .
5. Help salivary flow to overcome increase in peripheral
resistance of ducts.
217

Stem cells :
undifferentiated biological cells that
can differentiate into specialized cells and
can divide (through mitosis) to produce
more cells .
 They are found in
multicellular organisms. In mammals,
there are two broad types of stem
cells: embryonic stem cells, which are
isolated from the inner cell
mass of blastocysts, and adult stem cells,
which are found in various tissues.
Newer Advances in Cellular studies
218
Vipin Arora /Poojja Arora/Ak Munshi. Banking Stem cells from human exfoliated deciduous teeth
(SHED):Saving for the Future

 In adult organisms, stem cells and progenitor cells act as
a repair system for the body, replenishing adult tissues.
 In a developing embryo, stem cells can differentiate into
all the specialized cells—ectoderm, endoderm and
mesoderm .
 maintain the normal turnover of regenerative organs,
such as blood, skin, or intestinal tissues.
219

Different source of stem cells :
1. DPSC ( Dental pulp stem cells )
2. SHED ( Stem cells from exfoliated deciduous)
3. PLDSCs (Periodontal ligament dental stem cells)
4. SCAP ( Stem cells from apical papilla)
5. DFSCs ( Dental follicle stem cells )
220

 Cells are of a great diagnostic value.
 In exfoliative cytology, cells shed from body
surfaces, such as from the inside of the mouth,
are collected and examined.
 Oral cytology has appeared to be a promising
diagnostic tool for early detection of malignant
lesions.
221
www.google.com

CONCLUSION
 Cells vary in size , shape
& internal organization.
 All cells have a specific
job to do & look and
function best for that job.
222
www.google.com

REFERENCES
1. Guyton & hall.Textbook of medical physiology. 10th edition.elsevier
publication.
2. Kim E. Barret , Susan M. Barman,Scott Boitano.Ganong’s review of
medical physiology .24th edition.Lange basic science.
3. K. Sembulingam & Prema Sembulingam.Essentials of Medical
physiology .6th edition.Jaypee publications.
4. Kenneth M. Hargreaves , Stephen Cohen Cohen’s pathways of the pulp
.10th edition.Elsevier.
5. S.N Bhaskar.Orban’s Oral histology & Embryology.11th edition.Mosby
publication
6. B. Sivapathasundharam Shafer’s textbook of Oral Pathology .7th
edition.Elsevier.
7. Textbook of Dental & Oral Histology with Embryology by Chandra et al.
8. Vipin Arora /Poojja Arora/Ak Munshi. Banking Stem cells from human
exfoliated deciduous teeth (SHED):Saving for the Future
223

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