Cell Deaths: Necrosis😊

Cell Deaths: Necrosis

• Definition: Pathological cell death.
• Always occurs with disease.
• Never a normal physiological process.
• Always associated with inflammation.

Coagulative Necrosis:

• Most common type (Q1)

• Affects Solid Organs (Q2):
• Kidney, Heart, Liver
• Heart is most common organ
• NOT seen in Brain, Pancreas

• Mechanism (MOA) (Q3):
• Denaturation of proteins

• Features:
• Tissue architecture preserved (Q4)
• Numerous "GHOST cells" (Q5)
• Outline preserved, details lost
• Tombstone appearance

• Synonymous with Dry gangrene

Dry Gangrene

• Desiccated Tissue:
• Due to Gradual Slowing of Blood

• Good Line of Demarcation

• If Bone Involved: Conical Stump

 

Liquefactive (Colliquative) Necrosis:

• Affects: Brain, Pancreas
• Due to richness in hydrolytic enzymes
• Fungal infection (marrow)
• Abscess (marrow)

• Characteristics:
• Tissue architecture NOT preserved
• Results in liquid mass / forms abscess

• Synonymous with Wet gangrene

Wet Gangrene

• Due to Venous Blockade or Superadded Infection

• Poor Line of Demarcation

• Can be Proximal Due to Extension of Infection

Laws in Sensory Physiology

Bell–Magendie Law

• Dorsal root → Sensory

• Ventral root → Motor

• Mnemonic: Door (Dorsal) bell (Bell megendie) is ventrally (Ventral)

Law of Specific Nerve Energies (Müller’s Doctrine)

• Each receptor detects a specific sensation

• Examples:
• Pain receptor → Pain
• Touch receptor → Touch
• Cold receptor → Cold

• Mnemonic: Kayyil mulli → athoru specific sensation ayirunnu

Law of Projection

• Stimulation of a receptor
• Cortex projects sensation back to the lowest receptor level
• where the sensation originated

Cortical Plasticity

• Cortical reorganization by adjacent areas following injury.

• Example: Hand amputation → Hand area in cortex taken over by arm area → Arm pain felt as hand pain (Phantom limb pain)
• Primary somatosensory area = 4

• Mnemonic: Plastic prosthesis → Hand amputation

Weber–Fechner Law

• Magnitude of sensation ∝ log of initial stimulus intensity

• Mnemonic: SpiderWeb to skin → no intensity → no sensation

 

Caseous Necrosis:

• "Caseous" means cheesy (Q2)
• Gross appearance: Cheesy white material

• Coagulative >> liquefactive necrosis

• Primarily associated with:
• Tuberculosis (TB) (Q3)
• Fungal infections (Histoplasmosis, Coccidioidomycosis) (Q3)

Fat Necrosis:

• Involves: Death/breakdown of fat tissue
• Fat  breakdown → fatty acid + Ca²⁺

• Causes/Locations:
• Breast (due to trauma)
• Omentum (due to pancreatitis → increased lipase)

• Appearance:
• Chalky white areas (due to saponification from fatty acids and calcium)

Fibrinoid Necrosis:

• Affects: Blood vessels (BV)

• Caused by: Antigen-Antibody (Ag-Ab) complex formation

• Seen in:
• PAN (Polyarteritis Nodosa)
• RHD (Rheumatic Heart Disease) → Aschoff Bodies
• SLE (Systemic Lupus Erythematosus)
• HTN (Malignant Hypertension)

• Mnemonic: ashum () malayum () panil () ittitt fibre () vach ketti

Gangrene:

• Nature: A clinical diagnosis (used by clinicians/surgeons).
• Not primarily a pathology term.

• Definition: Describes black, foul-smelling tissue.

• Types and Pathological Basis:
• Dry Gangrene → Coagulative necrosis.
• Wet Gangrene → Liquefactive necrosis.

Zenker's Degeneration:

• Nature: Also a clinical term.

• Coagulative necrosis.

• Associated Condition:
• Typhoid fever 

• Affected Organs:
• Primarily affects skeletal muscle.
• rectus abdominis 
• diaphragmatic muscle.

• Mnemonic: Zenker → shankaran Koa (Coagulative) → thengi keri (Typhoid) → Vayaru idich veenu (skeletal muscle → rectus abd and diaphragm)