NEET MDS Synopsis
LUNG ABSCESS
General Pathology
LUNG ABSCESS Lung abscess is a localised area of necrosis of lung tissue with suppuration.
It is of 2 types:
- Primary lung abscess that develops in an otherwise normal lung. The commonest cause is aspiration of infected material.
- Secondary lung abscess that develops as a complication of some other disease of the lung or from another site
ETIOPATHOGENESIS.
The microorganisms commonly isolated from the lungs in lung abscess are streptococci, staphylococci and various gram-negative organisms. These are introduced into the lungs from one of the following mechanisms:
1. Aspiration of infected foreign material.
2. Preceding bacterial infection.
3. Bronchial obstruction.
4. Septic embolism.
5. Miscellaneous (i) Infection in pulmonary infarcts, (ii) Amoebic abscesses, (iii) Trauma to the lungs. (iv) Direct extension from a suppurative focus.
Abscesses may be of variable size from a few millimeters to large cavities, 5 to 6 cm in diameter. The cavity often contains exudate. An acute lung abscess is initially surrounded by acute pneumonia and has poorly-defined ragged wall. With passage of time, the abscess becomes chronic and develops fibrous wall.
Microscopic Examination
The characteristic feature is the destruction of lung parenchyma with suppurative exudate in the lung cavity. The cavity is initially surrounded by acute inflammation in the wall but later there is replacement by exudate of lymphocytes, plasma cells and macrophages. In more chronic cases, there is considerable fibroblastic proliferation forming a fibrocollagenic wall.
Autonomic Nervous System
Physiology
The Autonomic Nervous System (ANS) Controls the Body's Internal Environment in a Coordinated Manner
The ANS helps control the heart rate, blood pressure, digestion, respiration, blood pH and other bodily functions through a series of complex reflex actions
These controls are done automatically, below the conscious level
To exert this control the activities of many different organs must be coordinated so they work to accomplish the same goal
In the ANS there are 2 nerves between the central nervous system (CNS) and the organ. The nerve cell bodies for the second nerve are organized into ganglia:
CNS -> Preganglionic nerve -> Ganglion -> Postganglionic nerve -> Organ
At each junction neurotransmitters are released and carry the signal to the next nerve or organ.
The ANS has 2 Divisions, Sympathetic and Parasympathetic
Comparison of the 2 systems:
Anatomical
Location
Preganglionic
Fibers
Postganglionic
Fibers
Transmitter
(Ganglia)
Transmitter
(Organs)
Sympathetic
Thoracic/
Lumbar
Short
Long
ACh
NE
Parasympathetic
Cranial/
Sacral
Long
Short
ACh
ACh
The Sympathetic is the "Fight or Flight" Branch of the ANS
Emergency situations, where the body needs a sudden burst of energy, are handled by the sympathetic system
The sympathetic system increases cardiac output and pulmonary ventilation, routes blood to the muscles, raises blood glucose and slows down digestion, kidney filtration and other functions not needed during emergencies
Whole sympathetic system tends to "go off" together
In a controlled environment the sympathetic system is not required for life, but it is essential for any stressful situation
The Parasympathetic is the Rest and Digest Branch of the ANS
The parasympathetic system promotes normal maintenance of the body- acquiring building blocks and energy from food and getting rid of the wastes
It promotes secretions and mobility of different parts of the digestive tract.
Also involved in urination, defecation.
Does not "go off" together; activities initiated when appropriate
The vagus nerve (cranial number 10) is the chief parasympathetic nerve
Other cranial parasympathetic nerves are: III (oculomotor), VII (facial) and IX (glossopharyngeal)
The Hypothalamus Has Central Control of the ANS
The hypothalamus is involved in the coordination of ANS responses,
One section of the hypothalamus seems to control many of the "fight or flight" responses; another section favors "rest and digest" activities
The Adrenal Medulla is an Extension of the Sympathetic Nervous System
The adrenal medulla behaves like a combined autonomic ganglion and postsynaptic sympathetic nerve (see diagram above)
Releases both norepinephrine and epinephrine in emergency situations
Releases a mixture of epinephrine (E = 80%) and norepinephrine (NE = 20%)
Epinephrine = adrenaline
This action is under control of the hypothalamus
Sympathetic & Parasympathetic Systems
Usually (but not always) both sympathetic and parasympathetic nerves go to an organ and have opposite effects
You can predict about 90% of the sympathetic and parasympathetic responses using the 2 phrases: "Fight or Flight" and "Rest and Digest".
Special cases:
Occasionally the 2 systems work together: in sexual intercourse the parasympathetic promotes erection and the sympathetic produces ejaculation
Eye: the sympathetic response is dilation and relaxation of the ciliary muscle for far vision (parasympathetic does the opposite)
Urination: the parasympathetic system relaxes the sphincter muscle and promotes contraction of muscles of the bladder wall -> urination (sympathetic blocks urination)
Defecation: the parasympathetic system causes relaxation of the anal sphincter and stimulates colon and rectum to contract -> defecation (sympathetic blocks defecation)
Organ
Parasympathetic Response
"Rest and Digest"
Sympathetic Response
"Fight or Flight"
Heart
(baroreceptor reflex)
Decreased heart rate
Cardiac output decreases
Increased rate and strength of contraction
Cardiac output increases
Lung Bronchioles
Constriction
Dilation
Liver Glycogen
No effect
Glycogen breakdown
Blood glucose increases
Fat Tissue
No effect
Breakdown of fat
Blood fatty acids increase
Basal Metabolism
No effect
Increases ~ 2X
Stomach
Increased secretion of HCl & digestive enzymes
Increased motility
Decreased secretion
Decreased motility
Intestine
Increased secretion of HCl & digestive enzymes
Increased motility
Decreased secretion
Decreased motility
Urinary bladder
Relaxes sphincter
Detrusor muscle contracts
Urination promoted
Constricts sphincter
Relaxes detrusor
Urination inhibited
Rectum
Relaxes sphincter
Contracts wall muscles
Defecation promoted
Constricts sphincter
Relaxes wall muscles
Defecation inhibited
Eye
Iris constricts
Adjusts for near vision
Iris dilates
Adjusts for far vision
Male Sex Organs
Promotes erection
Promotes ejaculation
EPHEDRINE
Pharmacology
EPHEDRINE
It act indirectly and directly on α and β receptors. It increases blood pressure both by peripheral vasoconstriction and by increasing the cardiac output. Ephedrine also relaxes the bronchial smooth muscles.
Ephedrine stimulates CNS and produces restlessness, insomnia, anxiety and tremors.
Ephedrine produces mydriasis on local as well as systemic administration.
Ephedrine is useful for the treatment of chronic and moderate type of bronchial asthma, used as nasal decongestant and as a mydriatic without cycloplegia. It is also useful in preventing ventricular asystole in Stokes Adams syndrome.
N. meningiditis
General Pathology
N. meningiditis
Major cause of fulminant bacteremia and meningitis. Has a unique polysaccharide capsule. It is spread person to person by the respiratory route. Frequently carried in nasopharynx, and carriage rates increased by close quarters. Special risk in closed populations (college dorms) and in people lacking complement. Sub-saharan Africa has a “meningitis belt.”
Pathogenesis is caused by adherence factors that attach to non-ciliated nasopharyngeal epithelium. These factors include pili which promote the intial epithelial (and erythrocyte) attachment, and Opa/Opc surface binding proteins.
Adherence stimulates engulfment of bacteria by epithelial cells. Transported to basolateral surface.
The polysaccharide capsule is a major virulence factor that prevents phagocytosis and lysis.
A lipo-oligosaccharide endotoxin also contributes to sepsis.
COMPOSITE RESINS
Dental Materials
COMPOSITE RESINS
Applications / Use
Anterior restorations for aesthetics (class III, IV, V, cervical erosion abrasion lesions)
Low-stress posterior restorations (small class I, II)
Veneers
Cores for cast restorations
Cements for porcelain restorations
Cements for acid-etched Maryland bridges
Repair systems for composites or porcelains
Polymerization--reaction of small molecules (monomers) into very large molecules (polymers)
Cross-linking-tying together of polymer molecules by chemical reaction between the molecules to produce a continuous three-dimensional network
Anticonvulsant Drugs
Pharmacology
Anticonvulsant Drugs
A. Anticonvulsants: drugs to control seizures or convulsions in susceptible people
B. Seizures: abnormal neuronal discharges in the nervous system produced by focal or generalized brain disturbances
Manifestations: depend on location of seizure activity (motor cortex → motor convulsions, sensory cortex → abnormal sensations, temporal cortex → emotional disturbances)
Causes: many brain disorders such as head injury (glial scars, pH changes), anoxia (changes in pH or CSF pressure), infections (tissue damage, high T), drug withdrawal (barbiturates, ethanol, etc.), epilepsy (chronic state with repeated seizures)
C. Epilepsy: most common chronic seizure disorder, characterized by recurrent seizures of a particular pattern, many types (depending on location of dysfunction)
Characteristics: chronic CNS disorders (years to decades), involve sudden and transitory seizures (abnormal motor, autonomic, sensory, emotional, or cognitive function and abnormal EEG activity)
Etiology: hyperexcitable neurons; often originate at a site of damage (epileptogenic focus), often found at scar tissue from tumors, strokes, or trauma; abnormal discharge spreads to normal brain regions = seizure
Idiopathic (70%; may have genetic abnormalities) and symptomatic epilepsy (30%; obvious CNS trauma, neoplasm, infection, developmental abnormalities or drugs)
Neuropathophysiology: anticonvulsants act at each stage but most drugs not effective for all types of epilepsy (need specific drugs for specific types)
Seizure mechanism: enhanced excitation (glutamate) or ↓ inhibition (GABA) of epileptic focus → fire more quickly → ↑ release of K and glutamate → ↑ depolarization of surrounding neurons (=neuronal synchronization) → propagation (normal neurons activated)
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.
Stippling of the Gingiva
PeriodontologyStippling of the Gingiva
Stippling refers to the textured surface of
the gingiva that resembles the skin of an orange. This characteristic is
best observed when the gingiva is dried.
Characteristics:
Location:
The attached gingiva is typically stippled, while the marginal
gingiva is not.
The central portion of the interdental gingiva may exhibit
stippling, but its marginal borders are usually smooth.
Surface Variation:
Stippling is generally less prominent on the lingual surfaces
compared to the facial surfaces and may be absent in some
individuals.
Age-Related Changes:
Stippling is absent in infancy, begins to appear around 5 years
of age, increases until adulthood, and may start to disappear in old
age.
Attached Gingiva
Definition: The attached gingiva is the portion of the
gingiva that is firmly bound to the underlying alveolar bone and extends
from the free gingival groove to the mucogingival junction, where it meets
the alveolar mucosa.
Characteristics:
Structure:
The attached gingiva is classified as a mucoperiosteum, tightly
bound to the underlying alveolar bone.
Width:
The width of the attached gingiva is greatest in the incisor
region, measuring approximately:
3.5 – 4.5 mm in the maxilla
3.3 – 3.9 mm in the mandible
It is narrower in the posterior segments, measuring about:
1.9 mm in the maxillary first premolars
1.8 mm in the mandibular first premolars.
Histological Features:
The attached gingiva is thick and keratinized (or
parakeratinized) and is classified as masticatory mucosa.
Masticatory mucosa is characterized by a keratinized epithelium
and a thick lamina propria, providing resistance to mechanical
forces.
Masticatory vs. Lining Mucosa
Masticatory Mucosa:
Found in areas subject to high compression and friction, such as the
gingiva and hard palate.
Characterized by keratinized epithelium and a thick lamina propria,
making it resistant to masticatory forces.
Lining Mucosa:
Mobile, distensible, and non-keratinized.
Found in areas such as the lips, cheeks, alveolus, floor of the
mouth, ventral surface of the tongue, and soft palate.
Specialized Mucosa:
Found on the dorsum of the tongue, adapted for specific functions
such as taste.