– 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:
– sickle cell disease.
– corticosteroid administration.
– radiation therapy.
– chronic alcoholism.
ii) mechanism : interruption of blood supply to bones due to – trauma
2. Lever cell Necrosis:
i) Diffused (submassive to massive)
– Periportal (peripheral)
Refrence: Harsh Mohan textbook of Pathology (seventh edition).
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