– Defined as localized area of death of tissue, followed by degeneration of tissue, by hydrolytic enzymes, liberated by dead cells, accomplnied by inflammatory reaction..
– Caused by various agents like hypoxia, chemical agents, physical agents, microbial agents, immunological injury..

1. Coagulative Necrosis:
– common type.
– focal irreversible injury.
             – mostly by ischaemic necrosis. 
              (sudden cessation of blood flow)
             – rarely bacterial and chemical
– organs effected are heart, kidney, spleen.
– Microscopically it is the hallmark for conversion of normal cells into ‘tombstones’. (the cytoplasm and other material disappears but cell wall remains)

2. Liquefaction (colliquative)  Necrosis:
-ischaemic injury or bacterial infection.
-hydrolytic enzymes causes the material to become semi-fluid.

3. Caseous Necrosis:
– shows features of both Coagulative and Liquefaction necrosis.
– found in centers of foci of tuberculous infection.

4. Fat Necrosis:
– usually seen in breast and acute pancreatitis.

5. Fibrenoid Necrosis:
– immunological tissue injury.

1. Avascular Necrosis:
– of bones….. resulting from ischaemia.
– common condition.
     i) common cause:
             – fracture/dislocation.
             – sickle cell disease.
             – corticosteroid administration.
             – radiation therapy.
             – chronic alcoholism.
             – idiopathic.
    ii) mechanism : interruption of blood supply to bones due to – trauma
                                          – compression 
                                          – thromboembolic

2. Lever cell Necrosis:
i)  Diffused (submassive to massive)
ii) Zonal
         – Centrilobular
         – Midzone
         – Periportal (peripheral)
iii) Focal.

Refrence: Harsh Mohan textbook of Pathology (seventh edition).


Structure of Matter and Atom

hi all..
so chemistry is not my forte as such but as few of its topics are in my syllabus I’ll b briefing this small topics for now..

Structure of Matter:
– Matter is defined as “that which occupies space” and comprises a great number of different materials.
– Built up from smaller substances(elements) which cannot be split into smaller materials.
– All other substances are compounds formed by union of two or more elements.
Element: “Basic substance which cannot be split into simpler substances.”
Compound: “Formed by union of two or more elements.”
Molecule: “Smallest partive of any substance, element or compound, that can exist alone.”
Atom: “Smallest particle of element that can take part in chemical reaction.”

Structure of Atom:
1- All atoms are built up from three particles:
i) Proton: particle bearing positive charge of very small mass(1/2,000,000,000,000 of an inch)
ii) Neutron: Same mass as proton but with neutral charge.
iii) Electron:Still smaller with negative charge.
2- The number of protons in an atom is important as it determines the element of which it is in an atom.
eg.: hydrogen- 1,helium- 2,lithium- 3,beryllium- 4 and so on.
3- In small atoms, often the number of neutrons is equal to number of protons. In large atoms, the size in neutrons is more than that of protons.
4- The number of electrons in atom are generally equal hence making it electrically neutral.

Its arrangement is that like a solar systems (planets revolving around the sun) where the central nucleus acts as the sun and the revolving electrons as the planets.
Protons and neutons are held tightly together by strong cohesive force to form central nucleus of atom.

Clayton’s electrotherapy 4th edition

signing off..


Electromagnetic induction

note: this is a brief summary and might contain some errors-plz comment to correct if u find any or for further explanation..

Intro: Faraday and Henry observed that an EMF(electromagnetic force) is produced across the ends of a conductor when the number of magnetic lines of forces associated with the conductor changes. The EMF lasts so long as this change continues. This phenomenon of generating an EMF by changing the number of magnetic lines of forces associated with the conductor is called electro magnetic induction (EMI)
EMF developed is called induced EMF.
if it’s a closed circuit, the current flowing through it is called induced current.
Magnetic flux: number of lines of magnetic induction passing through the area of the coil.
units: Wb (webber)
Factors essential:
-A conductor.
-Magnetic lines of forces.
-Relative movement of conductor and magnetic lines of forces.
Faraday’s experiments:
experiment #1:  Circular insulated wire of one or more turnes connected to a galvanometer.
i) when a strong magnet is passed through the coil, galvanometer shows deflections indicating current is induced in the coil.
ii) deflections are temporary and lasts as long as the motion between the coil and magnet continues.
iii) more deflections when magnet is moved faster and less when it is moved slowly.
iv) direction of deflection is reversed when same pole of magnet is moved in opposite direction.
experiment #2: two coils are set up with one connected to key and battery, and other to a galvanometer. on opening and closing the key, temporary deflections occur in galvanometer. this is because current is induced in coil 2.
conclusion: the cause of EMF induced in a coil is, change in magnet flux linked with the coil.
the amount of magnetic flux linked with the coil must change in order to produce induced EMF in the coil.
Faraday’s laws:
First law: whenever the amount of magnetic flux linked with the circuit changes, an EMF is induced in the circuit. it lasts as long as the vhange in magnet flux continues.
Second law: the magnitude of EMF induced in a circuit is directly proportional to the rate of charge of magnetic flux linked with the circuit.
Strength of induced EMF:
i) rate of change of magnetic field: more rapid the movement and stronger the magnet used, greater is the rate at which the magnetic lines of force cut the conductor and grater the EMI induced.
ii) inductance of the conductor: inductance is the ability of the conductor to have current induced in it. it is constant for any conductor bt high inductance can be designed into a coil by incorporating –
-using many turnes of wire in coil.
– placing the turns closer together.
-winding the coil onto soft iron core.

Lenz’s law: The induced current will appear in such a direction that it opposes the change force responsible for its production.

Fleming’s right hand rule: according to this rule, if we stretch our fore finger, central finger and thumb such that they are perpendicular to each other then the forefinger represents the direction of magnetic field, thumb represents the direction of motion of conductor and central finger represents the direction of induced current.

P.S: more examples can be used for laws and experiments by the scientists.
p.p.s: i studied this yesterday but did not post it as i was sleepy so did this first thing in the morning.. 😜

1) intermediate second year physics by telugu akademi
2) Clayton’s electrotherapy – 8th edition
3) textbook of electrotherapy by jagmohan singh – 2nd edition

singning off..