NEET MDS Lessons
General Pathology
OEDEMA
Excessive accumulation of fluid in the extra vascular compartment (intersttitial tissues). This includes ascites (peritoneal sac), hydrothorax (pleural cavity) hydropericardium (pericardial space) and anasarca (generalised)
Factors which tend to accumulate interstitial fluid are:
- Intravascular hydrostatic pressure
- Interstitial osmotic pressure.
- Defective lymphatic drainage.
- Increased capillary permeability.
Factors that draw fluid into circulation are:
- Tissue hydrostatic-pressure (tissue tension).
- Plasma osmotic pressure,
Oedema fluid can be of 2 types:
A. Exudate.
It is formed due to increased capillary permeability as in inflammation.
B. Transudate
Caused by alterations of hydrostatic and osmotic pressures.
|
|
Exudate |
Transudate |
|
Specific Gravity |
>1.018 |
1.012 |
|
Protein Content |
High |
Low |
|
Nature of Protein |
All Plasma Protein |
Albumin mostly |
|
Spontaneous Clotting |
High(Inflammatory Cells) |
Low |
Local Oedema
1. Inflammatory oedema. Mechanisms are.
- Increased capillary permeability.
- Increased vascular hydrostatic pressure.
- Increased tissue osmotic pressure.
2.Hypersensitivity reactions especially types I and III
3. Venous obstruction :
- Thrombosis.
- Pressure from outside as in pregnancy, tourniquets.
4. Lymphatic obstruction:
- Elephantiasis in fillariasis
- Malignancies (Peau de orange in breast cancer).
Generalized Oedema
1. Cardiac oedema
Factors :Venous pressure increased.
2. Renal oedema
- Acute glomerulonephritis
- Nephrotic syndrome
3. Nutritional (hypoproteinaemic) oedema. it is seen in
- Starvation and Kwashiorkor
- Protein losing enteropathy
4. Hepatic oedema (predominantly ascites)
Factors:
- Fall in plasma protein synthesis
- Raised regional lymphatic and portal venous pressure
5. Oedema due to adrenal corticoids
As in Cushing's Syndrome
Pulmonary oedema
- Left heart failure and mitral stenosis.
- Rapid flv infusion specially in a patient of heart failure.
Hepatitis D virus—can only infect cells previously infected with hepatitis B.
Delta hepatitis (HDV) is associated with a 35-nm RNA virus composed of a delta antigen-bearing core surrounded by HBV's Ag coat;
HDV requires HBV for replication.
Delta hepatitis can cause quiescent HBV states to suddenly worsened . Its transmission is the same as that of HBV.
Hepatitis E virus—a high mortality rate in infected pregnant women.
Hepatitis E (HEV) is caused by a single-stranded RNA virus. The disease is typically self-limited and does not evolve into chronic hepatitis; it may, however, be cholestatic.
Pregnant women may develop fulminant disease.
Transmission is by the fecal oral route.
HEV occurs mainly in India, Nepal, Pakistan, and Southeast Asia.
Parkinson’s disease
a. Characterized by the degeneration of neurons in the basal ganglia, specifically the substantia nigra and striatum.
b. Histologic findings in affected neurons include Lewy bodies.
c. Clinically, the disease affects involuntary and voluntary movements. Tremors are common. Symptoms include pin-rolling tremors, slowness of movements, muscular rigidity, and shuffling gait.
Hematological examination
This is a method by which abnormalities of the cells of the blood and their precursors in the bone marrow are investigated to diagnose the different kinds of anemia & leukemia.
Keloids
1. Characterized by a progressively enlarging scar.
2. Caused by an abnormal accumulation of collagen at the site of injury.
3. More common in African-Americans.
NEOPLASIA
An abnormal. growth, in excess of and uncoordinated with normal tissues Which persists in the same excessive manner after cessation of the stimuli which evoked the change.
Tumours are broadly divided by their behaviors into 2 main groups, benign and malignant.
|
Features |
Benign |
Malignant |
|
General Rate of growth Mode of growth |
Slow Expansile |
Rapid Infiltrative |
|
Gross Margins
Haemoeehage |
Circumscribed often Encapsulated Rare |
III defined
Common |
|
Microscopic Arrangement Cells
Nucleus Mitosis |
Resemble Parent Tissues Regular and uniform in shape and size Resembles parent Cells Absent or scanty |
Varying degrees of structural differentiation Cellular pleomorphism
Hyper chromatic large and varying in shape and size Numerous and abnormal |
Through most tumours can be classified in the benign or malignant category . Some exhibits an intermediate behaviours.
CLASSIFICATION
|
Origin |
Benign |
Malignant |
|
Epithelial Surface epithelium Glandular epithelium Melanocytes |
Papilloma Adenoma Naevus |
Carcinoma Adenoca cinoma Melanocarcinoma(Melanoma) |
|
Mesenchymal
Adipose tissue Fibrous tissue Smooth tissue Striated muscle Cartilage Bone Blood vessels Lymphoid tissue |
Lipoma Fibroma Leiomyoma Rhabdomyoma Chondroma Osteoma Angioma
|
Liposarcoma Fibrosarcoma Leimyosarcoma Chondrosarcoma Osteosarcoma Angiosarcoma Lymphoma |
Some tumours can not be clearly categorized in the above table e.g.
- Mixed tumours like fibroadenoma of the breast which is a neoplastic proliferation of both epithelial and mesenchmal tissues.
- Teratomas which are tumours from germ cells (in the glands) and totipotent cells
(in extra gonodal sites like mediastinun, retroperitoneum and presacral region). These are composed of multiple tissues indicative of differentiation into the derivatives of the three germinal layers.
- Hamartomas which are malformations consisting of a haphazard mass of tissue normally present at that site.
Pleural effusion is a medical condition where fluid accumulates in the pleural cavity which surrounds the lungs, making it hard to breathe.
Four main types of fluids can accumulate in the pleural space:
Serous fluid (hydrothorax)
Blood (hemothorax)
Lipid (chylothorax)
Pus (pyothorax or empyema)
Causes:
Pleural effusion can result from reasons such as:
- Cancer, including lung cancer or breast cancer
- Infection such as pneumonia or tuberculosis
- Autoimmune disease such as lupus erythematosus
- Heart failure
- Bleeding, often due to chest trauma (hemothorax)
- Low oncotic pressure of the blood plasma
- lymphatic obstruction
- Accidental infusion of fluids
Congestive heart failure, bacterial pneumonia and lung cancer constitute the vast majority of causes in the developed countries, although tuberculosis is a common cause in the developing world.
Diagnosis:
- Gram stain and culture - identifies bacterial infections
- Cell count and differential - differentiates exudative from transudative effusions
- Cytology - identifies cancer cells, may also identify some infective organisms
- Chemical composition including protein, lactate dehydrogenase, amylase, pH and glucose - differentiates exudative from transudative effusions
- Other tests as suggested by the clinical situation - lipids, fungal culture, viral culture, specific immunoglobulins