NEET MDS Lessons
General Pathology
Salivary gland pathology
Inflammation
a. Sialolithiasis produces a secondary inflammatory reaction to obstruction and the resultant enlargement of ducts by stones. It may be complicated by actual infection with mouth flora.
b. Sialadenitis is a primary inflammatory reaction, but it is not always infectious. It may be part of an autoimmune disease (e.g., Sjogren's syndrome), or the result of bacterial or virals (e.g., mumps) infection.
Sjögren’s syndrome
a. An autoimmune disease of the salivary and lacrimal glands.
b. Autonuclear antibodies (ANAs) against salivary ducts may be seen.
c. Triad of symptoms include:
(1) Xerostomia—from decreased saliva production.
(2) Keratoconjunctivitis sicca (dry eyes)—from decreased tear production.
(3) Rheumatoid arthritis.
(4) Enlargement of the salivary or lacrimal glands, known as Mikulicz syndrome, may also be observed.
d. Histologically, a dense infiltration of the gland by lymphocytes is observed.
Tumors
The parotid gland accounts for more than three-quarters of these tumors, most of which are benign. Of the remainder, more occur in the submandibular gland than in the sublingual, and most of these are malignant. Many are surgically, cured, but local recurrence is common.
a. Pleomorphic adenoma is generally benign and accounts for approximately three-quarters of all salivary gland tumors. If is composed of multiple epithelial and mesenchymal cell types. Complications may arise due to involvement of cranial nerve VII.
(a) The most common salivary gland tumor.
(b) Is benign.
(c) Prognosis is good after proper surgical excision.
b. Warthin's tumor (adenolymphoma) is also benign, occuring almost exclusively in the parotid gland. It is grossly cystic.
Microscopic examination reveals cell types suggestive of branchial cleft origin embedded in a lymphoid matrix.
c. Mucoepidermoid tumors also occur primarily in the parotid and have a high rate of malignant transformation.The malignant component is usually squamous cell. Prognosis of tumor depends on grade and stage of disease.
d. Cylindroma (adenoid cysticc. Mucoepidermoid tumors carcinoma) is more common in the minor salivary glands found in the oral mucosa, and metastases are more common than in other tumors of the salivary glands. Facial nerve complications are frequent.
(1) Grossly, the tumor forms multiple lobules surrounded by a capsule.
(2) Microscopically, small cells form glands containin mucoid material
HYPERPLASIA
It is the increase in the size of an organ or tissue due to increase in the number of its constituent cells. This is seen in organs made up of labile and stable cells.
Causes
I. Increased demand:
- Bone marrow in hypoxia and haemolytic states.
- Thyroid gland in puberty
2. Persistant Trauma:
- Acanthosis of the epidermis in chronic inflammations and in warts.
- Hyperplasia of oral mucosa due tooth and denture trauma.
- Mucosa at the edges of a gastric ulcer.
3. Endocrine target organ:
- Pregnancy hyperplasia of breast.
- Prostatic hyperplasia.
4. Compensatory:
Hyperplasia of kidney when the other kidney has been removed.
5. Idiopathic:
Endocrine organs like thyroid, adrenals, pituitary etc. can undergo hyperplasia with no detectable stimulus. .
Acute viral hepatitis
Clinical features. Acute viral hepatitis may be icteric or anicteric. Symptoms include malaise, anorexia, fever, nausea, upper abdominal pain, and hepatomegaly, followed by jaundice, putty-colored stools, and dark urine.
In HBV, patients may have urticaria, arthralgias, arthritis, vasculitis, and glomerulonephritis (because of circulating immune complexes). Blood tests show elevated serum bilirubin (if icteric), elevated transaminases, and alkaline phosphatase.
The acute illness usually lasts 4-6 weeks.
Pathology
(1) Grossly, there is an enlarged liver with a tense capsule.
(2) Microscopically, there is ballooning degeneration of hepatocytes and liver cell necrosis.
INFLAMMATION
Response of living tissue to injury, involving neural, vascular and cellular response.
ACUTE INFLAMMATION
It involves the formation of a protein .rich and cellullar exudate and the cardinal signs are calor, dolor, tumour, rubor and function loss
The basic components of the response are
Haemodynamic changes.
Permeability changes
Leucocyte events.
1. Haemodynamic Changes :
- Transient vasoconstriction followed by dilatation.
- Increased blood flow in arterioles.
- More open capillary bed.
- Venous engorgement and congestion.
- Packing of microvasculature by RBC (due to fluid out-pouring)
- Vascular stasis.
- Change in axial flow (resulting in margination of leucocytes)
.2. Permeability Changes:
Causes.
- Increased intravascular hydrostatic pressure.
- Breakdown of tissue proteins into small molecules resulting in
- increased tissue osmotic pressure.
- Increased permeability due to chemical mediators, causing an
- immediate transient response. .
- Sustained response due to direct damage to microcirculation.
3. White Cell Events:
.Margination - due to vascular stasis and change in axial flow.
Pavementing - due to endothelial cells swollen and more sticky.
Leucocytes more adhesive.
Binding by a plasma component
Emigration - of leucocytes by amoeboid movement between endhothe1ial cells and beyond the basement membrane. The passive movement of RBCs through the gaps created during emigration is called diapedesis
Chemotaxis - This is a directional movement, especially of polymorphs and monocytes towards a concentration gradient resulting in aggregation of these cells at the site of inflammation. .Chemotactic agents may be:
- Complement components. (C3and C5 fragments and C567)
- Bacterial products.
- Immune complexes, especially for monocyte.
- Lymphocytic factor, especially for monocyte.
Phagocytosis - This includes recognition, engulfment and intracellular degradation. It is aided by .Opsonins., Specific antibodies., Surface provided by fibrin meshwork.
Functions of the fluid and cellular exudate
1. Dilution of toxic agent.
2. Delivers serum factors like antibodies and complement components to site of inflammation.
3. Fibrin formed aids In :
- Limiting inflammation
- Surface phagocytosis
- Framework for repair.
4. Cells of the exudate:
Phagocytose and destroy the foreign agent.
Release lytic enzymes when destroyed, resulting in extracellular killing of organisms- and digestion of debris to enable healing to occur
Alzheimer’s disease
a. The most common cause of dementia in older people.
b. Characterized by degeneration of neurons in the cerebral cortex.
c. Histologic findings include amyloid plaques and neurofibrillary tangles.
d. Clinically, the disease takes years to develop and results in the loss of cognition, memory, and the ability to ommunicate. Motor problems, contractures, and paralysis are some of the symptoms at the terminal stage.
Urinary tract infection
Most often caused by gram-negative, rod-shaped bacteria that are normal residents of the enteric tract, especially Escherichia coli.
Clinical manifestations:
frequent urination, dysuria, pyuria (increased PMNs), hematuria, and bacteriuria.
May lead to infection of the urinary bladder (cystitis) or kidney (pyelonephritis).
Wuchereria bancrofti, Brugia malayi (Filariasis)
- the microfilaria of Wuchereria bancrofti or Brugia malayi (nematodes) are transmitted to man by the bite of infected mosquitoes (Anophele, Aedes, Culex).
- microfilaria characteristically circulate in the bloodstream at night and enter into the lymphatics, where they mature and produce an inflammatory reaction resulting in lymphedema (elephantiasis) of the legs, scrotum, etc.