NEET MDS Lessons
General Pathology
Glycogen storage diseases (glycogenoses)
1. Genetic transmission: autosomal recessive.
2. This group of diseases is characterized by a deficiency of a particular enzyme involved in either glycogen production or degradative pathways.
Diseases include:
on Gierke disease (type I)
(a) Deficient enzyme: glucose-6-phosphatase.
(b) Major organ affected by the buildup of glycogen: liver.
Pompe disease (type II)
(1) Deficient enzyme: α-glucosidase(acid maltase).
(2) Major organ affected by the buildup of glycogen: heart.
Cori disease (type III)
(1) Deficient enzyme: debranching enzyme (amylo-1,6-glucosidase).
(2) Organs affected by the buildup of glycogen: varies between the heart, liver, or skeletal muscle.
Brancher glycogenosis (type IV)
(1) Deficient enzyme: branching enzyme.
(2) Organs affected by the buildup of glycogen: liver, heart, skeletal muscle, and brain.
McArdle syndrome (type V)
(1) Deficient enzyme: muscle phosphorylase.
(2) Major organ affected by the buildup of glycogen: skeletal muscle.
CONGESTION
Congestion or hyperaemia means an increase in the content of blood in an organ. It may be :
A. Active - due to increased arterial flow to the organ with dilatation of micro vessels as in
- Inflammation.
- Increased metabolic activity.
- Neurogenic blushing.
B. Passive - due to decreased venous drainage resulting in pooling of blood. There is always an associated element of oedema.
THROMBOPHLEBITIS AND PHLEBOTHROMBOSIS
- The deep leg veins account for more than 90% of cases (DVT)
- the most important clinical predispositions are: congestive heart failure, neoplasia, pregnancy, obesity, the postoperative state, and prolonged bed rest or immobilization
- local manifestations: distal edema, cyanosis, superficial vein dilation, heat, tenderness, redness, swelling, and pain
- migratory thrombophlebitis (Trousseau sign): hypercoagulability occurs as a paraneoplastic syndrome related to tumor elaboration of procoagulant factors
Valvular disease
A. Generally, there are three types:
1. Stenosis—fibrotic, stiff, and thickened valves, resulting in reduced blood flow through the valve.
2. Regurgitation or valvular insufficiency— valves are unable to close completely, allowing blood to regurgitate.
3. Prolapse—“floppy” valves; may occur with or without regurgitation. The most common valvular defect.
Monocytosis:
Causes
-Infections causing lymphocytosis, especialy tuberculosis and typhoid.
-Monocytic leukaemia.
-Some auto immune diseases.
Str. Pneumoniae
Probably the most important streptococci. Primary cause of pneumonia. Usually are diplococci. Ste. pneumoniae are α-hemolytic and nutritionally fastidious. Often are normal flora.
Key virulence factor is the capsule polysaccharide which prevents phagocytosis. Other virulence factors include pneumococcal surface protein and α-hemolysin.
Major disease is pneumonia, usually following a viral respiratory infection. Characterized by fever, cough, purulent sputum. Bacteria infiltrates alveoli. PMN’s fill alveoli, but don’t cause necrosis. Also can cause meningitis, otitis, sinusitis.
There are vaccines against the capsule polysaccharide. Resistance to penicillin, cephalosporins, erythromycins, and fluoroquinalones is increasing.
THE ADRENAL GLANDS
ADRENAL CORTEX
The adrenal cortex synthesizes three different types of steroids:
1. Glucocorticoids (principally cortisol), which are synthesized primarily in the zona fasciculata
2. Mineralocorticoids, the most important being aldosterone, which is generated in the zona glomerulosa; and
3. Sex steroids (estrogens and androgens), which are produced largely in the zona reticularis.
ADRENAL MEDULLA
The adrenal medulla is populated by cells derived from the neural crest (chromaffin cells) and their supporting (sustentacular) cells.
They secrete catecholamines in response to signals from preganglionic nerve fibers inthe sympathetic nervous system.