NEET MDS Synopsis
General chromosome abnormalities
General Pathology
General chromosome abnormalities
The normal human cell contains 46 chromosomes, including 22 homologous pairs of autosomes and one pair of sex chromosomes (XX for female and XY for male). A somatic cell is diploid, containing 46 chromosomes. Gametes are haploid, containing 23 chromosomes.
Aneuploidy
(a) Any deviation in the number of chromosomes, whether fewer or more, from the normal haploid number of chromosomes.
(b) Nondisjunction—a common cause of aneuploidy. It is the failure of chromosomes to pass to separate cells during meiotic or mitotic cell division.
(c) Often seen in malignant tumors.
Deletion: loss of a sequence of DNA from a chromosome.
Translocation: the separation of a chromosome and the attachment of the area of separation to another chromosome.
EPITHELIUMS
Anatomy
EPITHELIUMS
Epithelial Tissue Epithelial tissue covers surfaces, usually has a basement membrane, has little extracellular material, and has no blood vessels. A basement membrane attaches the epithelial cells to underlying tissues. Most epithelia have a free surface, which is not in contact with other cells. Epithelia are classified according to the number of cell layers and the shape of the cells.
Epitheliums contain no blood vessels. There is normally an underlying layer of connective tissue
Almost all epitheliums lie on a basement membrane.The basement membrane consists of a basal lamina and reticular lamina. The reticular lamina is connected to the basal lamina by anchoring fibrils. The reticular lamina may be absent in which case the basement membrane consist only of a basal lamina. The basal lamina consists of a - lamina densa in the middle (physical barrier) with a lamina lucida on both sides (+charge barrier),The basement membrane is absent in ependymal cells.The basement membrane is not continuous in sinusoidal capillaries.
Epitheliums always line or cover something
Epithelial cells lie close together with little intercellular space
Epithelial cells are strongly connected to one another especially those epitheliums that are subjected to mechanical forces.
Functions of Epithelium:
→ Simple epithelium involved with diffusion, filtration, secretion, or absorption
→ Stratified epithelium protects from abrasion
→ Squamous cells function in diffusion or filtration
INFARCTION
General Pathology
INFARCTION
Definition : a localized area of ischaemic necrosis in an organ infarcts may be:
Pale :as in
→ Arterial obstruction.
→ solid organs.
Red as in
→ Venous occlusion
→ Loose tissue.
Morphology
Gross: infarcts are usually wedge shaped the apex towards the occluded vessel They are
separated from the surrounding tissue by an hyperemic inflammatory zone
Microscopic:
- An area of coagulative necrosis with a rim of congested vessels and acute inflammatory infiltration of the tissue .
- The polymorphs ale later replaced by mononuclear cells and granulation tissue.
- With time, scar tissue replaces necrosed tissue.
Mucosal protective agents
Pharmacology
Mucosal protective agents.
These are locally active agents that help heal gastric and duodenal ulcers by forming a protective barrier between the ulcers and gastric acid, pepsin, and bile salts. They do not alter the secretion of gastric acid. These drugs include sucralfate and colloid bismuth compounds. (e.g. tripotassium, dicitratobismuthate). Colloidal bismuth compounds additionally exert bactericidal action against H.pylori. Also, Prostaglandins have both antisecretory and mucosal protective effects.
Example: Misoprostol- used for prevention of NSAID – induced ulcer.
- Drugs that exert antimicrobial action against H.pylori such as amoxicillin, metronidazole, clarithromycin and tetracycline are included in the anti-ulcer treatment regimens.
Classification
Anatomy
Classification
Epitheliums can be classified on appearance or on function
Classification based on appearance
- Simple - one layer of cells
- Pseudostratified - looks like more than one layer but is not
- Stratified - more than one layer of cells
Simple epitheliums
Simple squamous epithelium
Cells are flat with bulging or flat nuclei. Lines the insides of lung alveoli and certain ducts in the kidney
Forms serous membranes called mesothelium that line cavities like: pericardial , peritoneal, plural
Lines blood vessels - known as endothelium
Simple cuboidal epithelium
It appears square in cross section, Found in: - Ducts of salivary glands, Follicles of the thyroid gland, Pigment layer in the eye, Collecting ducts of the kidney, In the middle ear is ciliated type.
Simple columnar
Lines the gastrointestinal tract from the stomach to the anal canal, Some columnar cells have a secretory function – stomach, peg cells in the oviduct, Some columnar cells have microvilli on their free border (striated border) – gall bladder, duodenum
Microvilli increase the surface area for absorption
Some columnar cells have cilia – oviduct, smaller bronchi
Cilia transport particles
Pseudostratified
Appears as stratified epithelium but all cells are in contact with the basement membrane. Has a thick basement membrane. Different cell types make up this epithelium, Cells that can be found in this type of epithelium are:
Columnar cells with cilia or microvilli.
Basal cells that do not reach the surface.
Goblet cells that secrete mucous.
Found in the trachea, epididymus, ductus deferens and female urethra
Stratified epithelium
Classified according to the shape of the surface cells
Stratified squamous epithelium
Has a basal layer that varies from cuboidal to columnar cells that divide to form new cells. Two types are found:
Keratinized: Mostly forms a dry covering, The middle layers consists of cells that are forming- and filling up with keratin. The superficial cells form a tough non living layer of keratin, Keratin is a type of protein, The skin is of this type has thick skin - found on the hand palms and soles of the feet, thin skin - found on the rest of the body
Non-keratinized: Top layer of cells are living cells with nuclei Forms a wet covering, The middle layers are polyhedral, The surface layer consists of flat squamous cells
Is found in: mouth, oesophagus, vagina
Stratified cuboidal epithelium
Found: - in the ducts of sweat glands
Stratified columnar epithelium
Found at the back of the eyelid (conjunctiva)
Transitional epithelium
- Sometimes the surface cells are squamous, sometimes cuboidal and sometimes columnar
- The superficial cells are called umbrella cells because they can open and close like umbrellas, when the epithelium stretch and shrink
- Umbrella cells can have 2 nuclei
- Found in the bladder and ureter
Salivary Factors and Their Mechanisms
PedodonticsSalivary Factors and Their Mechanisms
1. Buffering Factors
Buffering factors in saliva help maintain a neutral pH in the oral cavity,
which is vital for preventing demineralization of tooth enamel.
HCO3 (Bicarbonate)
Effects on Mineralization: Acts as a primary buffer
in saliva, helping to neutralize acids produced by bacteria.
Role in Raising Saliva or Plaque pH: Increases pH
by neutralizing acids, thus promoting a more favorable environment for
remineralization.
Urea
Effects on Mineralization: Releases ammonia (NH3)
when metabolized, which can help raise pH and promote mineralization.
Role in Raising Saliva or Plaque pH: Contributes to
pH elevation through ammonia production.
Arginine-rich Proteins
Effects on Mineralization: Releases ammonia, which
can help neutralize acids and promote remineralization.
Role in Raising Saliva or Plaque pH: Increases pH
through ammonia release, creating a less acidic environment.
2. Antibacterial Factors
Saliva contains several antibacterial components that help control the growth
of pathogenic bacteria associated with dental caries.
Lactoferrin
Effects on Bacteria: Binds to iron, which is
essential for bacterial growth, thereby inhibiting bacterial
proliferation.
Effects on Bacterial Aggregation or Adherence: May
promote clearance of bacteria through aggregation.
Lysozyme
Effects on Bacteria: Hydrolyzes cell wall
polysaccharides of bacteria, leading to cell lysis and death.
Effects on Bacterial Aggregation or Adherence: Can
indirectly promote clearance by breaking down bacterial cell walls.
Peroxidase
Effects on Bacteria: Produces hypothiocyanate
(OSCN), which inhibits glycolysis in bacteria, reducing their energy
supply.
Effects on Bacterial Aggregation or Adherence: May
help in the aggregation of bacteria, facilitating their clearance.
Secretory IgA
Effects on Bacteria: Neutralizes bacterial toxins
and enzymes, reducing their pathogenicity.
Effects on Bacterial Aggregation or Adherence:
Binds to bacterial surfaces, preventing adherence to oral tissues.
Alpha Amylase
Effects on Bacteria: Produces glucose and maltose,
which can serve as energy sources for some bacteria.
Effects on Bacterial Aggregation or Adherence:
Indirectly promotes bacterial aggregation through the production of
glucans.
3. Factors Affecting Mineralization
Certain salivary proteins play a role in the mineralization process and the
maintenance of tooth enamel.
Histatins
Effects on Mineralization: Bind to hydroxyapatite,
aiding in the supersaturation of saliva, which is essential for
remineralization.
Effects on Bacteria: Some inhibition of mutans
streptococci, which are key contributors to caries.
Proline-rich Proteins
Effects on Mineralization: Bind to hydroxyapatite,
aiding in saliva supersaturation.
Effects on Bacteria: Promote adherence of some oral
bacteria.
Cystatins
Effects on Mineralization: Bind to hydroxyapatite,
aiding in saliva supersaturation.
Effects on Bacteria: Promote adherence of some oral
bacteria.
Statherin
Effects on Mineralization: Bind to hydroxyapatite,
aiding in saliva supersaturation.
Effects on Bacteria: Promote adherence of some oral
bacteria.
Mucins
Effects on Mineralization: Provide a physical and
chemical barrier in the enamel pellicle, protecting against
demineralization.
Effects on Bacteria: Facilitate aggregation and
clearance of oral bacteria.
Prenatal Counseling
Pedodontics Prenatal Counseling for Dental Health
Prenatal counseling is a crucial aspect of establishing a child's dental
preventive program. Initiating this process before the birth of the child allows
parents to prepare for their child's health and well-being effectively. This
period is particularly significant for first-time parents, as they are often
more receptive to health recommendations and eager to learn how to provide the
best care for their child.
Importance of Prenatal Counseling
Timing: The best time to begin counseling is during
pregnancy, as expectant parents are highly motivated to learn about health
practices that will benefit their child.
Parental Awareness: Expectant parents become acutely
aware of their child's dependence on them for nurturing and health care,
fostering a strong instinct to provide the best possible environment for
their child.
Key Counseling Topics
Parental Hygiene Habits:
Role Modeling: Parents should be encouraged to
adopt good oral hygiene practices, as children often emulate their
parents' behaviors.
Impact on Child's Oral Health: Discuss how parents'
oral health can directly affect their child's health, including the
transmission of bacteria that can lead to dental issues.
Pregnancy Gingivitis:
Education: Inform the mother-to-be about the
potential for pregnancy gingivitis, a common condition characterized by
swollen and bleeding gums due to hormonal changes.
Myth Dispelling: Address common myths surrounding
childbirth and dental health, emphasizing the importance of maintaining
oral hygiene during pregnancy.
Infant Dental Care:
Early Care: Provide a review of infant dental care
practices, including:
The importance of cleaning the infant's gums even before teeth
erupt.
Guidelines for the introduction of the first toothbrush and
toothpaste.
Recommendations for regular dental check-ups starting at the age
of one or when the first tooth appears.
Benefits of Prenatal Counseling
Improved Oral Health: By educating expectant parents
about their own oral hygiene and its impact on their child, both the parents
and the child can achieve better oral health outcomes.
Preparation for Parenthood: Counseling helps parents
feel more prepared and confident in their ability to care for their child's
dental health from an early age.
Long-term Health: Establishing good dental habits early
on can lead to a lifetime of healthy oral practices for the child.
Paralleling Technique
PedodonticsParalleling Technique in Dental Radiography
Overview of the Paralleling Technique
The paralleling technique is a method used in dental radiography to obtain
accurate and high-quality images of teeth. This technique ensures that the film
and the long axis of the tooth are parallel, which is essential for minimizing
distortion and maximizing image clarity.
Principles of the Paralleling Technique
Parallel Alignment:
The fundamental principle of the paralleling technique is to
maintain parallelism between the film (or sensor) and the long axis of
the tooth in all dimensions. This alignment is crucial for accurate
imaging.
Film Placement:
To achieve parallelism, the film packet is positioned farther away
from the object, particularly in the maxillary region. This distance can
lead to image magnification, which is an undesirable effect.
Use of a Longer Cone:
To counteract the magnification caused by increased film distance, a
longer cone (position-indicating device or PID) is employed. The longer
cone helps:
Reduce Magnification: By increasing the
distance from the source of radiation to the film, the image size is
minimized.
Enhance Image Sharpness: A longer cone
decreases the penumbra (the blurred edge of the image), resulting in
sharper images.
True Parallelism:
Striving for true parallelism enhances image accuracy, allowing for
better diagnostic quality.
Film Holder and Beam-Aligning Devices
Film Holder:
A film holder is necessary when using the paralleling technique, as
it helps maintain the correct position of the film relative to the
tooth.
Some film holders are equipped with beam-aligning devices that
assist in ensuring parallelism and reducing partial exposure of the
film, thereby eliminating unwanted cone cuts.
Considerations for Pediatric Patients
Size Adjustment:
For smaller children, the film holder may need to be reduced in size
to accommodate both the film and the child’s mouth comfortably.
Operator Error Reduction:
Proper use of film holders and beam-aligning devices can help
minimize operator error and reduce the patient's exposure to radiation.
Challenges with Film Placement:
Due to the shallowness of a child's palate and floor of the mouth,
film placement can be somewhat compromised. However, with careful
technique, satisfactory films can still be obtained.