NEET MDS Synopsis
DEGENERATION
General Pathology
DEGENERATION
Definition: Reversible cell injury.
(1) Water accumulation in the form of
(i) Cloudy swelling.
(ii) Vacuolar degeneration.
.(ill) Hydropic degeneration.
This change is commonly seen in parenchymal cells e.g. kidneys.
Gross appearance: The organ is swollen, soft and pale.
Microscopic appearance: Cells show varying degrees of swelling. Cytoplasm may be granular, vacuolated, homogenously pale and ballooned out.
(2) Fatty change An excessive, demonstrable accumulation of fat is common in parenchymal cells of liver and heart
In the liver, it can be due to: .
(i) Excess fat entry into the liver as occurs in starvation and in steroid excess due to mobilization from stores.
(ii) Excess triglyceride formation
(iii) Reduced phosphorlyation of fat.
(iv) Decreased release as lipoprotein due to protein deficiency.
Causes
(i) Hypoxia as in severe anaemia and venous stasis
(ii) Protein malnutrition.
(iii) Hepatotoxins like CCl4.
(iv) Alcoholism
(v) Metabolic defects like Diabetes mellitus
(vi) Infections.
Gross appearance: The organ is enlarged, soft and greasy, with a pale yellowish colour. It may involve the organ uniformly or patchily ( thrush breast or tabby cat heart)
Microscopic appearance: The cells contain clear vacuoles (stainable by fat-sudan stains on frozen sections). These may be small and dispersed or large, displacing the nucleus peripherally. Several such cells may fuse to form fat cysts.
(3) Hyaline degeneration
In alcoholic liver damage, the cytoplasmic organelles are damaged and give the cytoplasm a deep eosinophilic staining-Mallory hyaline.
Cholelithiasis
General Pathology
Cholelithiasis (Biliary calculi)
- These are insoluble material found within the biliary tract and are formed of bile constituents (cholesterol, bile pigments and calcium salts).
Sites: - -Gall bladder, extra hepatic biliary tract. Rarely, intrahepatic biliary tract.
Predisposing factors:-
- Change in the composition of bile. - It is the disturbance of the ratio between cholesterol and lecithin or bile salts which may be due to Hypercholesterolaemia which may be hereditary or the 4 F (Female, Forty, Fatty, Fertile). Drugs as clofibrate and exogenous estrogen. High intake of calories (obesity).
Increased concentration of bilirubin in bile- pigment stones
Hypercalcaemia:- Calcium carbonate stones.
2- Staisis.
3- Infection.
Pathogenesis i- Nucleation or initiation of stone formation:- The nidus may be cholesterol “due to supersaturation” Bacteria, parasite
RBCs or mucous.
ii- Acceleration:- When the stone remains in the gall bladder, other constituents are added to the
nidus to form the stone.
Complications of gall stones:-
- Predispose to infection.- Chronic irritation leading to
a. Ulceration b. Squamous metaplasia & carcinoma.
Basic Principles of Treatment of a Fracture
Oral and Maxillofacial SurgeryBasic Principles of Treatment of a Fracture
The treatment of fractures involves a systematic approach to restore the
normal anatomy and function of the affected bone. The basic principles of
fracture treatment can be summarized in three key steps: reduction, fixation,
and immobilization.
1. Reduction
Definition: Reduction is the process of restoring the
fractured bone fragments to their original anatomical position.
Methods of Reduction:
Closed Reduction: This technique involves
realigning the bone fragments without direct visualization of the
fracture line. It can be achieved through:
Reduction by Manipulation: The physician uses
manual techniques to manipulate the bone fragments into alignment.
Reduction by Traction: Gentle pulling forces
are applied to align the fragments, often used in conjunction with
other methods.
Open Reduction: In some cases, if closed reduction is
not successful or if the fracture is complex, an open reduction may be
necessary. This involves surgical exposure of the fracture site to directly
visualize and align the fragments.
2. Fixation
Definition: After reduction, fixation is the process of
stabilizing the fractured fragments in their normal anatomical relationship to
prevent displacement and ensure proper healing.
Types of Fixation:
Internal Fixation: This involves the use of devices
such as plates, screws, or intramedullary nails that are placed inside
the body to stabilize the fracture.
External Fixation: This method uses external
devices, such as pins or frames, that are attached to the bone through
the skin. External fixation is often used in cases of open fractures or
when internal fixation is not feasible.
Goals of Fixation: The primary goals are to maintain the
alignment of the bone fragments, prevent movement at the fracture site, and
facilitate healing.
3. Immobilization
Definition: Immobilization is the phase during which the
fixation device is retained to stabilize the reduced fragments until clinical
bony union occurs.
Duration of Immobilization: The length of the
immobilization period varies depending on the type of fracture and the bone
involved:
Maxillary Fractures: Typically require 3 to
4 weeks of immobilization.
Mandibular Fractures: Generally require 4
to 6 weeks of immobilization.
Condylar Fractures: Recommended immobilization
period is 2 to 3 weeks to prevent temporomandibular
joint (TMJ) ankylosis.
Properties of cardiac muscle
Physiology
Properties of cardiac muscle
Cardiac muscle is a striated muscle like the skeletal muscle , but it is different from the skeletal muscle in being involuntary and syncytial .
Syncytium means that cardiac muscle cells are able to excite and contract together due to the presence of gap junctions between adjacent cardiac cells.
Cardiac muscle has four properties , due to which the heart is able to fulfill its function as a pumping organ. Studying and understanding these properties is essential for students to understand the cardiac physiology as a whole.
1. Rhythmicity ( Chronotropism )
2. Excitability ( Bathmotropism )
3. Conductivity
4. Contractility
TRIMETHOPRIM
Pharmacology
TRIMETHOPRIM
It is a diaminopyrimidine. It inhibits bacterial dihydrofolate reductase( DHFRase).
In combination with sulphamethoxzole it is called Co-trimoxazole.
Spectrum of action
S. Typhi. Serratia. Klebsiela and many sulphonamide resistant strains of Staph.aureus. Strep pyogens
Adverse effects
Megaloblastic anemia. i.e.. due to folate defeciency.
Contraindicated in pregnancy.
Diuretics if given with co-trimoxazole cause thrombocytopenia.
Uses
I. UTI. 2. RTI. 3. Typhoid. 5. Septicemias. 5. Whooping cough
LOCATION OF THE TEETH
Dental Anatomy
LOCATION OF THE TEETH
Normally, a human receives two sets of teeth during a lifetime.
The first (deciduous or primary) set consists of 20 teeth ("baby" teeth).
The second (permanent) set usually consists of 32 teeth. In each quadrant, there are eight permanent teeth: two incisors, one cuspid, two bicuspids, and three molars
The tooth positioned immediately to the side of the midline is the central incisor, so called because it occupies a central location in the arch.
To the side of the central incisor is the lateral incisor. Next is the cuspid, then the two bicuspids (the first bicuspid, followed by the second bicuspid). The last teeth are three molars. After the second bicuspid comes the first molar, followed by the second molar, followed by the third molar or more commonly called the "wisdom tooth."
Another method of describing the location of teeth is to refer to them as anterior or posterior teeth .
Anterior teeth are those located in the front of the mouth, the incisors, and the cuspids. Normally, these are the teeth that are visible when a person smiles.
The posterior teeth are those located in the back of the mouth-the bicuspids and molars.
Nomenclature for stereoisomers
Biochemistry
Nomenclature for stereoisomers: D and L designations are based on the configuration about the single asymmetric carbon in glyceraldehydes
For sugars with more than one chiral center, the D or L designation refers to the asymmetric carbon farthest from the aldehyde or keto group.
Most naturally occurring sugars are D isomers.
D & L sugars are mirror images of one another. They have the same name. For example, D-glucose and L-glucose
Other stereoisomers have unique names, e.g., glucose, mannose, galactose, etc. The number of stereoisomers is 2 n, where n is the number of asymmetric centers. The six-carbon aldoses have 4 asymmetric centers, and thus 16 stereoisomers (8 D-sugars and 8 L-sugars
An aldehyde can react with an alcohol to form a hemiacetal
Similarly a ketone can react with an alcohol to form a hemiketal
Pentoses and hexoses can cyclize, as the aldehyde or keto group reacts with a hydroxyl on one of the distal carbons
E.g., glucose forms an intra-molecular hemiacetal by reaction of the aldehyde on C1 with the hydroxyl on C5, forming a six-member pyranose ring, named after the compound pyran
The representations of the cyclic sugars below are called Haworth projections.
Fructose can form either:
a six-member pyranose ring, by reaction of the C2 keto group with the hydroxyl on C6
a 5-member furanose ring, by reaction of the C2 keto group with the hydroxyl on C5.
Cyclization of glucose produces a new asymmetric center at C1, with the two stereoisomers called anomers, α & β
Haworth projections represent the cyclic sugars as having essentially planar rings, with the OH at the anomeric C1 extending either:
below the ring (α)
above the ring (β).
Because of the tetrahedral nature of carbon bonds, the cyclic form of pyranose sugars actually assume a "chair" or "boat" configuration, depending on the sugar
Aspirin
Pharmacology
Aspirin
Mechanism of Action
ASA covalently and irreversibly modifies both COX-1 and COX-2 by acetylating serine-530 in the active site Acetylation results in a steric block, preventing arachidonic acid from binding
Uses of Aspirin
Dose-Dependent Effects:
Low: < 300mg blocks platelet aggregation
Intermediate: 300-2400mg/day antipyretic and analgesic effects
High: 2400-4000mg/day anti-inflammatory effects
Often used as an analgesic (against minor pains and aches), antipyretic (against fever), and anti-inflammatory. It has also an anticoagulant (blood thinning) effect and is used in long-term low-doses to prevent heart attacks
Low-dose long-term aspirin irreversibly blocks formation of thromboxane A2 in platelets, producing an inhibitory affect on platelet aggregation, and this blood thinning property makes it useful for reducing the incidence of heart attacks
Its primary undesirable side effects, especially in stronger doses, are gastrointestinal distress (including ulcers and stomach bleeding) and tinnitus. Another side effect, due to its anticoagulant properties, is increased bleeding in menstruating women.