The cellular and chemical level of organization

1. THE CELLULAR AND CHEMICAL
LEVEL OF ORGANIZATION
Somya Jain
PG – 1st year
Department of Pedodontics
RCDS & RC,BHOPAL
1

2. 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

3. Structural organization of human body
Atoms and molecules
Cells
Tissues
Organelles
Organs
Organ system
Organism
3

4. Cell
 Basic structural & functional unit of life.
 Smallest living unit.
 Grow, reproduce , use energy , adapt & respond to
their environment.
 In humans , highly specialized.
4

5. The History of the Cell
 Discovery made possible by the invention of the
microscope
 1600’s.
 Anton van Leeuwenhoek
first described living cells
as seen through a
simple microscope.
5

6.  Robert Hooke used the first compound
microscope to view thinly sliced cork cells.
 Hooke was the first to use the term “cell”.
6

7.  1830’s.
 Mathias Schleiden identified the first
plant cells and concluded that all plants
made of cells.
 -Thomas Schwann made the same
conclusion about animal cells.
7

8. Cell Theoryby :Schleidenand
Schwannproposedthecelltheoryin1838
 All organisms are made up of one or more
cells.
 The cell is the basic unit of organization of
all organisms.
 All cells come from other cells all ready in
existence.
8

9. Cell Examination
 Key tool for examination – Microscope
light microscope electron microscope
resolution upto 0.2 μm upto 0.002 μm
9

10. Types of cells
1.On the basis of nucleus –
A ) Prokaryotes – no nuclei present
B ) Eukaryotes – nuclei present
10

11. Eukaryotic cell can again be classified as -
1) Unicellular 2 ) multicellular
yeast , fungi plant cell animal cell
11

12. 12

13. Eukaryotic animal cell parts
 2 major parts :
1- nucleus
2- cytoplasm
13

14. Protoplasm
 Different substances that make up the cell
are called PROTOPLASM.
 Includes – 1. water
2. electrolytes/ions
3. proteins
4. lipids
5. carbohydrates
14

15. 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.
15

16. 2. Electrolytes /ions -
• Imp. Ions are - K⁺ , Mg⁺⁺ , HCO³⁻, PO₄²⁻, SO₄²⁻
• In small amount – Na⁺ , Cl⁻ , Ca²⁺
• Provide inorganic chemicals
for cellular reactions .
16

17. 3 . Proteins –
• 10 – 20 % of cell mass.
• 2 types : A) Structural proteins
B) Globular proteins
17

18. 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.
18

19. Globular proteins-
 Composed of individual molecule or combination of
molecules in globular form .
 Mainly “ enzymes “ of the cell.
 As enzymes they catalyze chemical reactions .
19

20. 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.
20

21. 5 . Carbohydrates –
• Main nutritive & little structural function.
• Present as – dissolved “ glucose “ in ECF.
insoluble “ glycogen “ within cell.
21

22. Physical structure of the cell
Membranous structures of the cell –
Membrane within cell includes –
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
22

23.  Membranes are made up of both lipids and
proteins .
 Selectively permeable/ semi permeable.
 Provides communication within the cell and with
external environment.
23

24. Cell membrane/plasma membrane
24

25. 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.
25

26.  In 1972, S.J. Singer & G. Nicolson proposed
the “ FLUID MOSAIC “ model to describe the
structure of cell membrane.
26
It’s like a fluid…
It’s like a mosaic…
It’s the
Fluid Mosaic Model!

27. Approximate composition-
 Proteins – 55%
 Phospholipids – 25%
 Cholesterol – 13%
 Other lipids – 4%
 Carbohydrates – 3%
27

28. 28
Membrane is a collage of proteins & other molecules
embedded in the fluid matrix of the lipid bilayer
Glycoprotein Extracellular fluid
Cytoplasm
Transmembrane
proteins
Glycolipid
Phospholipids
Filaments of
cytoskeleton
Cholesterol
Peripheral
protein

29. 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
29

30. 30
Phospholipids
 Fatty acid tails
 hydrophobic
 Phosphate group head
 hydrophilic
 Arranged as a bilayer
Fatty acid
Phosphate

31. Phospholipid bilayer-Amphipathic molecule
31
polar
hydrophilic
Heads ( phosphate
portion)
nonpolar
hydrophobic
Tails ( fatty acid
portion )
polar
hydrophilic
heads

32. 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.
32

33. Cell membrane proteins
 Present as globular masses.
 Mainly “ glycoproteins “.
 2 types –
peripheral proteins
loosely bound to surface of membrane
integral proteins
penetrate lipid bilayer, usually across whole
membrane
 transmembrane protein
 transport proteins
33

34. Proteinsdomainsanchormolecule
 Within membrane
 nonpolar amino acids
 hydrophobic
 anchors protein
into membrane
 On outer surfaces of membrane
 polar amino acids
 hydrophilic
 extend into extracellular fluid
& into cytosol
34
Polar areas
of protein
Nonpolar areas of protein

35. Functions of proteins –
35
 1 – ion channels /pores

36.  2- carrier molecules -
36

37.  3- pumps -
37

38.  4 – enzymes
 5 – as cell identity markers
38

39.  6- as linkers
 7- as receptors
39

40. 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”.
40

41. 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.
41

42. 42
Movement across
the Cell Membrane

43. 43
 What molecules can get through directly?
 fats & other lipids
 What molecules can
NOT get through
directly?
 polar molecules
 H2O
 ions
 salts, ammonia
 large molecules
 starches, proteins

44.  PassiveTransport
 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
44

45.  Transport summary
45
simple
diffusion
facilitated
diffusion
active
transport
ATP

46. 46
How about large molecules?
 Moving large molecules into & out of cell
 through vesicles & vacuoles
 endocytosis
 phagocytosis = “cellular eating”
 pinocytosis = “cellular drinking”
 exocytosis
exocytosis

47. 47
Endocytosis
phagocytosis
pinocytosis
receptor-mediated
endocytosis
fuse with lysosome
for digestion
non-specific
process
triggered by
molecular signal

48. Cytoplasm & its organelles
 2 main componenets – 1. cytosol
2. organelles
48

49. Cytosol :
 Also k/w as intracellular fluid / cytoplasmic
matrix.
 Entire cell – nucleus = cytoplasm.
 Complex mixture of substances dissolved in
water (75-90%).
 Ions conc. Different in cytosol than ECF –
helps in osmoregulation & cell signaling.
 Contains large amt. of macromolecules
which can alter molecules behaviour-
MACROMOLECULAR CROWDING .
49

50. ORGANELLES PRESENT -
1- mitochondria
2- endoplasmic reticulum
3- ribosomes
4-golgi apparatus
5-lysossomes
6-peroxisomes
7-cytoskeleton
50

51. 1- MITOCHONDRIA
51
POWERHOUSE OF
THE CELL.

52.  Structure -
Sausage shaped
organelle .
DNA – ds circular
Contains approx.
16500 base pairs.
52

53. Functions -
 1. ATP generation via oxidative phosphorylation.
 2. cofactor in krebs cycle .
 3. calcium ion storage .
 4. apoptosis .
53

54. Mitochondrial DNA
54
 Maternal inheritance.
 Responsible for certain key components of
the pathway for oxidative phosphorylation.
 Ineffective DNS repair system.
 Mutation rate 10 times than nDNA.

55. 2- ENDOPLASMIC RETICULUM
55

56.  Structure
 Complex series of tubules & vesicles in
cytoplasm.
 Covered by lipid bilayer membrane &
proteins .
 Inner limb – continuation of a segment of
nuclear membrane.
56

57. Types :
 A) RER/Rough ER/ Granular ER
 B) SER/Smooth ER/Agranular ER
57

58. Functions -
 A) Rough ER :
 Protein synthesis- glycoproteins
 Also produces secretory , membrane & organelle proteins
 Initial folding of polypeptide chains with disulfide bond
formation.
58

59.  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.
59

60.  Transport vesicles/ ER vesicles
To check the ER from growing beyond the needs of cell.
60

61. 3- Ribosomes
61

62.  Structure :
 Composed of mixture of RNA & proteins.
 approx. – 22*32nm
 Made up of 2 subunits :
 larger subunit – 60 ‘S’
 Smaller subunit– 40 ‘S’
62

63.  Types :
A) Attached to ER
B) Free ribosomes
63

64.  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 .
64

65. 65

66. 4-Golgi Apparatus/Complex/Body
66

67.  Structure –
 Composed of stacks of membrane bound
structures k/w as cisternae.
 Usually 6-7 cisternae present.
 Polarised structure .
 Cisternae has 2 sides – cis side & trans side.
67

68.  Functions –
 A) Modifying , sorting & packaging of
macromolecules for cell secretion or use within cell.
68

69.  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.
69

70.  In this respect, GA is thought of as similar
to a “post office” ; packages & labels items
& send it to different parts of cell.
70

71.  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.
71

72. 5- LYSOSOMES
72

73.  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.
73

74.  Interior is more acidic than rest of the
cytoplasm due to the action of Proton Pump or
H⁺ , ATPase.
74

75.  Hydrolytic enzymes present are capable of
splitting an organic compound into 2 or more
parts.
75
substances Hydrolysed into
Proteins Amino acids
glycogen Glucose
lipids Fatty acids & glycerol

76.  Enzymes present in lysosomes –
76

77.  Functions –
 Provides intracellular digestive system
77

78.  A) digest unwanted matter such as bacteria
78

79.  B) digest cellular structures
79

80.  C) digest food particles that have been
ingested by cell
80

81.  k/w as “Suicidal Bags Of Cell”.
 Membrane surronding acts as a safety
feature.
81

82.  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.
82

83. 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
83

84. 6- PEROXISOMES
84

85.  Structure similar to lysososmes.
 Ard. 0.5 µm in dia. surronded by membrane .
85

86.  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.
86

87. 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.
87

88. Peroxisome Proliferator Activated
Receptors ( PPAR’s)
 Members of nuclear receptor family.
 When combined with synthetic
compounds ,they get activated bind to DNA
& produce changes in production of mRNA’s
leading to peroxisome proliferation.
88

89. Peroxins -
 Protein chaperons , which acts as unique
signal sequence , to direct proteins to
peroxisomes.
89

90. 7- CYTOSKELETON
90

91.  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
91

92. A) Microtubules-
92
 Structure –
 Long hollow structures
 15nm dia. Cavity surronded by 5 nm wall.
 Made up of 2 globular protein – 1) α tubulin
2) β tubulin

93.  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.
93

94. Functions -
 Provide tracks along which different molecular
motors move transport vesicles , organelles like
secretory granules , mitochondria from 1 part of
cell to another.
94

95.  Forms spindles which move the
chromosomes in mitosis.
95

96. 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 .
96

97. 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 .
97

98. 98

99. 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.
99

100. 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 .
100

101. 101

102. Molecular Motors
 These are 100 to 500 kDa ATPases.
 3 superfamilies – a. kinesin
b. dynein
c. myosin
102

103.  Move proteins , organelles & other cell parts
( collectively called “ CARGO” ) to other parts of
cell.
 They convert the energy of ATP into
movement along the cytoskeleton.
103

104. CENTROSOMES -
 Present near the nucleus in cytoplasm.
 Made up of – 2 centrioles & surronding
amorphous pericentriolar material.
 Small cylinders at right angles to each other.
104

105.  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.
 Monitor steps in cell division.
 They are MTOC’s ( δ tubulin)
105

106. Nucleus
106
BRAIN OF THE CELL

107.  Control centre/ brain of the cell.
 Structure – 1) nuclear envelope / membrane
2) nuclear pore complexes
3) nucleolus
4 ) chromatin & genes
107

108. 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.
108

109. 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.
109

110. 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.
110

111. 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.
111

112.  Abt. 25 million nucleosome present in each
nucleus .
 Thus, chromosomes appear as strings of
beads.
 Beads – nucleosome
 Strings – linker DNA chromatin ( DNA &
proteins )
112

113.  Chromosomes – complete blueprint for all
the heritable species & indivual
characteristics of animals.
 Paired ; except in germ cells.
113

114. Genes
 Portion of DNA molecule.
114

115.  Ultimate unit of heredity.
 DNA is used for specific protein synthesis.
115

116. Protein synthesis
Transcription ( DNA RNA )
Translation ( RNA Proteins)
Proteins
116

117. The body as an organized “solution”
 In an average young adult male –
117
Body wt. % Substance
18% Proteins & related
substances
7% minerals
15% fat
60% Water ( fluid)

118. Water -
 Because of high surface tension, high heat
capacity & high electrical capacity – ideal
solvent.
118

119. 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
119

120. 120

121. 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 ) .
121

122.  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 thru the cell
membranes (Na⁺- K⁺ATPase)
122

123.  Some imp. Constituents & physical characteristics of
ECF , the normal range of control & approx. non-
lethal limits for short periods -
123
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

124. 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
temperatu
re
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
124

125.  K⁺ ions –
when conc. - paralysis
when conc. - depresses heart muscles
 Ca²⁺ -
when conc. - tetanic conc. Of muscles all
thru out the body.
 Glucose –
when conc. Falls – extreme mental irritability &
sometimes convulsions.
125

126.  Thus , most important are the limits of
concentrations beyond which a vicious circle
of increasing cellular metabolism starts that
literally destroys the cell.
126

127. Life span of selected human cells
• Granulocytes -- 10 hours to 3 days
•Stomach lining cells -- 2 days
•Sperm cells -- 2-3 days
•Stomach lining cells -- 2 days
•Colon cells -- 3-4 days
•Epithelia of small intestine -- 1 week or less
•Platelets -- 10 days
127

128. •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 years
128

129. Specialised cells of the oral cavity
129

130. Classification of cells on the
basis of origin
 From ectoderm – 1. oral mucous membrane
2. enamel
From mesoderm – 1. dentin
2. pulp
3. cementum
4. periodontal ligament
5. alveolar bone
130

131. 1- Ameloblasts
 Cells forming the enamel.
131

132.  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 asTOME’S PROCESSES.
132

133. Cytologic changes in life cycle of
ameloblasts
133

134.  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.
134

135. Clinical considerations-
HYPOPLASIA
135

136. 136

137. 2- Odontoblasts
 Cells forming dentin .
 Most specialized cells of dentin pulp complex.
137

138. 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.
138

139.  Polarized cell – nucleus aligned away from
newly formed dentin.
 Nucleus – large with upto 4 nucleoli.
 cell rich in RER , mitochondria, golgi complex.
139

140. 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.
140

141. 141

142. Functions of odontoblasts -
 1. aids in secretion of intertubular & peritubular
dentin.
 2. general maintainence of both dentinal fluid &
tubules.
 3. secretes sclerotic dentin , secondary dentin ,
reactionary dentin.
 4. secretes proteins required for mineralization -
dentin phosphoprotein ( DPP)
osteonectin , osteopontin , gla protein ,
proteoglycans .
142

143.  5. also secretes phosphophoryn ( unique to
dentin )
 6. synthesizes type I collagen ; small amt. of
typeV.
 7. also secretes acid phosphatase & alkaline
phosphatase .
143

144. 3- Odontoclasts
 Cells responsible for removal of dental hard
tissue.
 Origin – derived from tartarate resistant acid
phosphatase (TRAP) positive circulating
monocytes.
144

145. 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.
145

146.  Adjacent to ruffled border clear zone – in
which the cytoplasm is devoid of organelle
but rich in filaments consisting of contractile
proteins actin & myosin.
146

147. Clinical consideration -
147
Dentinogenesi
s Imperfecta

148. 4- Cells of the Pulp
 Includes – A) fibroblasts
B) undifferentiated ectomesenchymal cells /
pulpal stem cells.
C) defence cells
D) Odontoblasts
148

149. 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.
149

150.  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”.
150

151. 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.
151

152. 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
thruout the central pulp.
 No. decreases with age.
152

153. 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 .
153

154.  Dentonin, a peptide from matrix extracellular
phosphoglycoprotein – stimulate pulp stem
cells.
 Growth factors like –TGF beta 1 & BMP -2
involved in proliferation & differentiation.
154

155. Defense cells -
 Includes – 1. histiocytes / macrophages
2. dendritic cells
3. lymphocytes
4. mast cells
5. plasma cells
155

156. 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.
156

157.  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 memoryT- cells.
157

158.  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 )
158

159. 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.
159

160.  In deciduous teeth – closely associated with
odontoblasts ; no. increases in areas affected
by caries , restorative procedures .
 No. also increases during shedding.
160

161.  Function –
induction ofT – cell immunity .
161

162. Lymphocytes -
 MainlyT- lymphocytes found .
 T8( suppressor) lymphocytes are
predominate.
 Found extravascularly in normal pulp.
 No. increases in inflammation.
162

163. 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.
163

164. 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.
164

165. 5 – Cementoblasts
 Cells responsible for cementogenesis .
165

166.  Structure –
 Polygonal to cuboidal in shape.
 Large vesicular nucleus with 1 or more
nucleoli.
 Numerous mitochondria , well formed GA ,
RER.
166

167.  Cells get entrapped in the lacunae of their
own matrix –CEMENTOCYTES.
 Lacunae have canals or canaliculi – oriented
toward the PDL & contains cemetocytic
processes .
167

168.  Function –
 Synthesize collagen & protein
polysaccharides – organic matrix of
cementum.
 For Differentiation into cementoblasts–
 Growth factors likeTGF 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.
168

169. Periodontal ligament cells
169

170.  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
170

171. 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.
171

172. Epithelial rests of Malassez
 Cuboidal cells.
 Prominent nucleus ; stains deeply.
 Scanty cytoplasm.
 Mitochondria present.
 RER & GA poorly developed.
172

173. Alveolar bone cells
173

174.  Includes – Osteoblasts
Bone lining cells
Osteocytes
Osteoclasts
174

175. 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 175

176.  Morphology –
• Basophilic , plump cuboidal or slightly
elongated cells .
• Found on the forming surfaces of growing or
remodelling bone.
• Abundant RER & Golgi complex.
176

177. • Nucleus is situated eccentrically in the part of
cell farthest away from adjacent bone
surface.
• Contain prominent bundles of actin , myosin
& cytoskeletal protein.
177

178.  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 typeV
(osteoid).
4. Mineralization of osteoid.
178

179. Osteocytes
 Osteoblasts entrapped within the matrix they
secrete – OSTEOCYTES.
 No. of osteoblasts that become osteocytes
depend on rapidity of bone formation.
179

180.  Within the bone matrix – osteocytes reduce
in size , creates a space around it – osteocytic
lacuna.
 Lacunae- ovoid or flateened.
 From lacunae narrow extensions arise –
canaliculi .
180

181.  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.
181

182. Osteoclats -
 Morphology –
 Large cell approx. 40-100μm in dia.With
ruffled border.
 15-20 closely packed nuclei.
 Variable in shape due to motility.
182

183.  Extensive mitochondria & golgi complex.
 RER sparse.
 Cathepsin containing vesicles & vacoules
present near ruffled border.
 Lies in resorption bays called “Howship’s
Lacunae”.
183

184.  Function – removes the bone tissue by
removing the mineralized matrix of bone.
184

185. Cells of oral mucous membrane
Cells of OMM
Non-
keratinocytes
melanocytes
Langerhans
cells
keratinocytes Merkel cells
185

186. 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.
186

187.  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 .
187

188.  Stratum spinosum
 Cells are irregularly polyhederal & larger than
basal cells.
 Cells are joined by “intercellular bridges”.
 More active in protein synthesis.
188

189.  Stratum granulosum
 Flatter & wider cells .
 Larger than spinous cell layer.
 Basophilic keratohyaline granules.
 Nuclei shows sign of degradation & pyknosis
189

190.  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.
190

191. 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
191

192. 192
functions Pigment containing
cells which give
brownish hue to the
gingiva.
Immunologic function
of recognising &
processing antigenic
material and presenting
it toT – lymphocytes.
granules release
transmitter across
the synapse.
Sensory and respond
to touch.

193. 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.
193

194. Inter relation of keratinocytes &
non- keratinocytes
Keratinocytes
produce
cytokines
CK’s modulate
function of
langerhans
cells
Langerhans
cells produce
CK’S like IL-1
IL-1 activatesT-
lymphocytes &
increases no. of
receptors to
MSH
MSH acts on
melanocytes-
pigmentation
194

195. 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.
 10,000 taste buds are present in its papilla.
 A papilla contains few to 100 taste buds.
195

196.  Location ofTaste 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.
196

197. 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.
197

198. Electron microscopic
structure of taste buds
198

199. 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 .
199

200.  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 immunoglobulins
Ig A).
200

201. 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.
201

202.  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.
202

203.  Their watery secretion contains enzymes
(amylase, lysozyme), IgA secretory piece and
lactoferrin (iron binding compound).
 The parotid glands are composed
entirely of serous glands.
203

204. Mucous cells
 Elongated pyramidal
cells with pale
vacuolated cytoplasm
basally located nuclei.
 Cell shows
accumulation of large
amount of secretory
products at apical
cytoplasm.
204

205.  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 .
205

206.  Produce low proteins high in
carbohydrates (mucin).
 ONLYTHE PALATINE AND LATERAL
LINGUAL GLANDS ARE ENTIRELY
MUCUS-SECRETING.
206

207. 207
 PAROTID-serous
 SUBMANDIBULAR
 mixed
serous/mucous
 SUBLINGUAL-
 mucous/demilun
es

208. Myoepithelial cells
 Stellate or spider like
cells .
 Flattened nucleus .
 Scanty perinuclear
cytoplasm & long
branching processes
that embrace the
secretory & duct cells.
208

209.  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.
209

210. 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.
210

211.  Cells are of a great diagnostic value.
 In exfoliative cytology, cells shed from body
surfaces, such as 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.
211

212. Conclusion
 Cells vary in size ,
shape & internal
organization.
 All cells have a
specific job to do &
look and function
best for that job.
212

213. References
1. Textbook of Medical Physiology by Guyton &
Hall.
2. Ganong’s review of medical physiology by Kim
E. Barret , Susan M. Barman,Scott Boitano.
3. Essentials of Medical physiology by K.
Sembulingam & Prema Sembulingam.
4. Cohen’s pathways of the pulp by Kenneth M.
Hargreaves , Stephen Cohen.
5. Orban’s Oral histology & Embryology.
6. Shafer’s textbook of Oral Pathology .
7. Textbook of Dental & Oral Histology with
Embryology by Chandra et al . 213

214. THANK YOU
214