Necrosis Vs Apoptosis

Q. Mention differences between necrosis and apoptosis.

Ans : Though both necrosis and apoptosis are events of cell death, they do differ in various ways. The differences can be observed under following parameters :

a) Cell Size
The cell is enlarged (swelling) in necrosis whereas the cell is reduced (shrinkage) in apoptosis.

b) Fate of Nucleus
In necrosis, nucleus undergoes series of changes like pyknosis ( irreversible condensation of chromatin in the nucleus of a cell ) , karyorrhexis (fragmentation of nucleus) and karyolysis (complete dissolution of the chromatin of a dying cell due to the enzymatic degradation). But, in Apoptosis, nucleus undergoes fragmentation into nucleosome size fragments

c) Plasma Membrane
The plasma membrane is disrupted and is full of leakages in case of necrosis but, it is intact in cells undergoing apoptosis. Only the orientation of lipids in plasma membrane is altered in apoptosis.

d) Cellular contents
Due to ruptured plasma membrane, cellular contents undergo digestion and may leak out of the cell in necrosis. But, the cellular contents are intact in case of apoptosis. However, they may be released in apoptotic bodies.

e) Adjacent inflammation
There is no any adjacent inflammation seen in apoptosis whereas adjacent inflammation can be seen in necrosis.

f) Physiologic or pathologic role
Apoptosis is often physiologic but necrosis is always pathologic.

Necrosis : Definition, Types and Examples

Q. Define Necrosis. Enlist its types with an example of each.

Ans: Necrosis is the type of cell death that is associated with loss of membrane integrity and leakage of cellular contents culminating in dissolution of cells, largely resulting from the degradative action of enzymes on lethally injured cells.

Types of Necrosis:
i) Coagulative Necrosis
- underlying tissue architecture is preserved,

- affected tissues take on a firm texture

- characteristic of infarcts in all of the solid organs except the brain

ii) Liquefactive Necrosis
- seen in focal bacterial or fungal (occasionally) infections

- the dead cells are digested completely, transforming the tissue into a liquid viscous mass

- seen often in hypoxic death of cells within CNS

iii) Caseous Necrosis (Caseous = Cheese like)
- Encountered most often in foci of tubercular infection

- friable yellow white appearance of the necrotic region

- area of caseous necrosis is often enclosed within a distinctive inflammatory border; this appearance is characteristic of a focus of inflammation known as a granuloma


iv) Fat Necrosis
- focal areas of fat destruction

- seen in Acute Pancreatitis

- grossly visible chalky white areas can be seen

v) Fibrinoid Necrosis
- special form of necrosis visible by light microscopy

- usually in immune reactions in which complexes of antigens and antibodies are deposited in the walls of arteries.

- a bright pink and amorphous appearance on H&E preparations called fibrinoid (fibrin-like) by pathologists

- seen in  immunologically mediated diseases (e.g. polyarteritis nodosa)

vi) Gangrenous Necrosis
- mostly the affected organ has lost its blood supply and has undergone coagulative necrosis involving multiple tissue layers

- When bacterial infection is superimposed, coagulative necrosis is modified by the liquefactive action of the bacteria and the attracted leukocytes (resulting in so-called wet gangrene)

- e.g. necrosis of a limb (mostly lower)

World Oral Health Day - 20th March 2017 - Live Mouth Smart

Poster for Oral Health Awareness : World Oral Health Day 2017 , Designed By: Raman Dhungel, BPKIHS,Dharan, Nepal.

FDI World Dental Federation (Federation Dentaire Internationale), has decided to celebrate 20th March 2017 as the world oral health day with a theme "Live mouth Smart".

The first World Oral Health Day was celebrated on 20th March 2013 by FDI World Dental Federation. Since then, every year , on 20th March it is celebrated across the globe by organising various campaigns and programs to raise Oral health awareness.

The themes for World Oral Health Day till date are:
2013: Healthy Teeth for Healthy Life
2014: Brush for a Healthy Mouth!
2015: Smile For Life!
2016: It all Starts Here. Healthy Mouth. Healthy Body
2017: Live Mouth Smart.


Good oral health leads to good overall health.
Share the message of World Oral Health Day and spread Oral Health Awareness.

MCQs on Oral Histology - Dentin Part 5

# During the formation of primary teeth:
A. Enamel forms more cervically than dentin
B. Enamel forms faster than dentin
C. Dentin forms faster than enamel
D. Processes of their cells remain in content with each other

# Matrix vesicles :
A. Are found in mantle dentin
B. Contain collagen
C. Produce alkaline phosphatase
D. Inhibit mineralization

# Transmission of stimulus across dentin is:
A. Direct activation of nerve endings
B. Correlated with the innervation density of the dentin
C. Stimulus induced fluid flow
D. There is no transmission of stimulus across dentin

# During hydrodynamic theory movement of fluids in dentinal tubules cause:
A. Movement of odontoblasts
B. Touch the nerves of the pulp to cause pain
C. Minimum effect on odontoblast
D. Stimulation of odontoblastic process


# Which of the areas of the tooth is most sensitive during cavity preparation :
A. Enamel (anterior teeth)
B. Enamel (posterior teeth)
C. Dentin
D. Dentinoenamel junction

# Matrix vesicles play important role in the mineralization of :
A. Dentin
B. Enamel
C. Pulp
D. Periodontal ligament

# False statement regarding interglobular dentin is :
A. The term interglobular dentin refers to organic matrix that remains unmineralized because the mineralising globules fail to coalesce
B. This occurs most often in the circumpulpal dentin just below the mantle dentin
C. Where the pattern of mineralization is likely to be appositional than globular
D. Large areas of interglobular dentin is a characteristic feature of childhood hypophosphatasia

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MCQs on Oral Histology - Dentin Part 4

# S-Shape of dentinal tubule is due to:
A. Incremental deposition
B. Peritubular dentin
C. Crowding of odontoblasts
D. Due to excess amount of organic component

# The formation of which of the following does not represent normal physiological process of dentin formation?
A. Primary and secondary dentin
B. Secondary dentin and Circumpulpal dentin
C. Tertiary dentin and Sclerotic dentin
D. All of the above

# All of the following is true about dentinal tubules except:
A. Inner pulpal layer contains more dentinal tubules than outer dentin layer
B. The diameter of dentin tubules ranges from 5 to 7 micrometer
C. The diameter of dentinal tubule is more at pulpal layer than outer layer
D. The bonding is more difficult is more difficult on the inner layer of dentin compared to outer surface

# Fluid flow , in and out of the dentinal tubules is proportional to the tubule diameter by:
A. Third power of the diameter
B. Sixth power of the diameter
C. Square of the diameter
D. Fourth power of the diameter

# The average diameter of coronal dentinal tubules near the pulp is :
A. 0.2-0.5 microns
B. 2-3 microns
C. 0.2-0.3 microns
D. 7 microns

# In adult teeth , the type of dentin present underlying dentino-enamel junction is:
A. Predentin
B. Mantle dentin
C. Interglobular dentin
D. Tertiary dentin


# All are the factors governing dentin permeability except:
A. Smear layer
B. Fluid Convention
C. Length of Dentinal tubules
D. Diffusion coefficient

# The most accepted theory for dentin sensitivity is :
A. Transduction theory
B. Direct neural stimulation
C. Hydrodynamic theory
D. Hydrostatic theory

# Compared to intertubular dentin , peritubular dentin is characterized by which of the following ?
A. Greater stainability
B. Lesser content of the inorganic salts
C. Greater content of the inorganic salts
D. Greater content of large collagen fibers

# One of the following statement is unique about circumpulpal dentin :
A. Collagen fibers are oriented perpendicular to DEJ
B. Von Korff fibers are present
C. Contain Phosphophoryn
D. Requires matrix vesicle for mineralisation

<<View Part 3      View Part 5>>>

MCQs on Oral Histology - Dentin Part 3

# Formula of hydroxyapatite crystal is :
A. Ca3(Po4)2.CaCO3
B. 3Ca3(Po4)2. Ca(OH)2
C. CaPo4. Ca(OH)2
D. None of the above

# The type of dentin that is formed prior to root completion is :
A. Inter tubular dentin
B. Peritubular dentin
C. Circumpulpal dentin
D. Secondary dentin

# Accentuated incremental lines in dentin due to disturbances in matrix and mineralisation process is:
A. Incremental lines of Retzius
B. Incremental lines of von Ebner
C. Contour lines of Owen
D. None of the above

# The pain transmission through dentin is :
A. Direct neural stimulation
B. Fluid or hydrodynamic theory
C. Transduction theory
D. All of the above

# Which of the following is correct ?
A. Reparative dentin is characterized by having fewer and more twisted tubules than normal dentin and may include odontoblasts
B. Dead tracts appear black in transmitted and white in reflected light
C. Sclerotic/transparent dentin appears transparent or light in transmitted light
D. All of the above


# First formed dental tissue :
A. Enamel
B. Dentin
C. Cementum
D. Bone

# Dentinal tubules are calcified in:
A. Sclerotic dentin
B. Secondary dentin
C. Primary dentin
D. Interglobular dentin

# Dentin formed throughout the life is:
A. Sclerotic dentin
B. Secondary dentin
C. Repartive dentin
D. All of the above

# Regarding teeth which statement is wrong ?
A. Enamel is harder than dentin
B. Enamel has no cells
C. Ameloblast secrete enamel and dentin
D. Odontoblast produce dentin

<<View part 2       View part 4>>>

MCQs on Oral Histology - Dentin Part 2

# The dentin receptors are unique because:
A. They elicit pain to hot and cold
B. They elicit pain to touch and pressure
C. They elicit pain to chemicals
D. Elicit only pain as a response

# The main bulk of dentin is formed by :
A. Peritubular dentin
B. Mantle dentin
C. Inter tubular dentin
D. Predentin

# The zone of dentin most recently formed and uncalcified is known as:
A. Mantle dentin
B. Circumpulpal dentin
C. Predentin
D. Secondary dentin

# Inter globular dentin results due to:
A. Failure of coalescence of calcospherites
B. Fracture of the dentin
C. Artifact in light microscopy
D. Disturbance in dentinal tubules

# Dentinogenesis by odontoblasts first behins at :
A. Pulpal end
B. Cusp tip
C. Tooth bud stage
D. Cervical area


# Sclerotic dentin has following features :
A. Caries susceptible
B. Insensitive
C. Hypersensitive
D. Resistant to caries

# The microhardness of dentin is about:
A. 1/2 that of enmel
B. 1/7 that of enamel
C. 1/4 that of enamel
D. 1/5 that of enamel

# Shape of the crown and the size of the roots is determined by:
A. Pulp
B. Dentin
C. Enamel
D. Cementum

# Physically and chemically, the dentin is closely related to:
A. Bone
B. Acellular cementum
C. Enamel
D. None of the above

# Organic portion can be separated from the mineral by :
A. Incineration / Organic chelation
B. Decalcification
C. Devitrification
D. Combustion

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