NEET MDS Synopsis
NEOPLASIA
General Pathology
NEOPLASIA
An abnormal. growth, in excess of and uncoordinated with normal tissues Which persists in the same excessive manner after cessation of the stimuli which evoked the change.
Tumours are broadly divided by their behaviors into 2 main groups, benign and malignant.
Features
Benign
Malignant
General
Rate of growth
Mode of growth
Slow
Expansile
Rapid
Infiltrative
Gross
Margins
Haemoeehage
Circumscribed often Encapsulated
Rare
III defined
Common
Microscopic
Arrangement
Cells
Nucleus
Mitosis
Resemble Parent Tissues
Regular and uniform in shape and size
Resembles parent Cells
Absent or scanty
Varying degrees of structural differentiation
Cellular pleomorphism
Hyper chromatic large and varying in shape and size
Numerous and abnormal
Through most tumours can be classified in the benign or malignant category . Some exhibits an intermediate behaviours.
CLASSIFICATION
Origin
Benign
Malignant
Epithelial
Surface epithelium
Glandular epithelium
Melanocytes
Papilloma
Adenoma
Naevus
Carcinoma
Adenoca cinoma
Melanocarcinoma(Melanoma)
Mesenchymal
Adipose tissue
Fibrous tissue
Smooth tissue
Striated muscle
Cartilage
Bone
Blood vessels
Lymphoid tissue
Lipoma
Fibroma
Leiomyoma
Rhabdomyoma
Chondroma
Osteoma
Angioma
Liposarcoma
Fibrosarcoma
Leimyosarcoma
Chondrosarcoma
Osteosarcoma
Angiosarcoma
Lymphoma
Some tumours can not be clearly categorized in the above table e.g.
Mixed tumours like fibroadenoma of the breast which is a neoplastic proliferation of both epithelial and mesenchmal tissues.
Teratomas which are tumours from germ cells (in the glands) and totipotent cells
(in extra gonodal sites like mediastinun, retroperitoneum and presacral region). These are composed of multiple tissues indicative of differentiation into the derivatives of the three germinal layers.
Hamartomas which are malformations consisting of a haphazard mass of tissue normally present at that site.
Respiratory system
PhysiologyRespiratory system plays important role in maintaining homeostasis . Other than its major function , which is supplying the cells with needed oxygen to produce energy and getting rid of carbon dioxide , it has other functions :
1 Vocalization , or sound production.
2 Participation in acid base balance .
3 Participation in fluid balance by insensible water elimination (vapors ).
4 Facilitating venous return .
5 Participation in blood pressure regulation : Lungs produce Angiotensin converting enzyme ( ACE ) .
6 Immune function : Lungs produce mucous that trap foreign particles , and have ciliae that move foreign particles away from the lung. They also produce alpha 1 antitrepsin that protect the lungs themselves from the effect of elastase and other proteolytic enzymes
Lateral Pharyngeal Space
Oral and Maxillofacial SurgeryLateral Pharyngeal Space
The lateral pharyngeal space is an important anatomical area in the neck that
plays a significant role in various clinical conditions, particularly
infections. Here’s a detailed overview of its anatomy, divisions, clinical
significance, and potential complications.
Anatomy
Shape and Location: The lateral pharyngeal space is a
potential cone-shaped space or cleft.
Base: The base of the cone is located at the base
of the skull.
Apex: The apex extends down to the greater horn of
the hyoid bone.
Divisions: The space is divided into two compartments
by the styloid process:
Anterior Compartment: Located in front of the
styloid process.
Posterior Compartment: Located behind the styloid
process.
Boundaries
Medial Boundary: The lateral wall of the pharynx.
Lateral Boundary: The medial surface of the mandible
and the muscles of the neck.
Superior Boundary: The base of the skull.
Inferior Boundary: The greater horn of the hyoid bone.
Contents
The lateral pharyngeal space contains various important structures,
including:
Muscles: The stylopharyngeus and the superior
pharyngeal constrictor muscles.
Nerves: The glossopharyngeal nerve (CN IX) and the
vagus nerve (CN X) may be present in this space.
Vessels: The internal carotid artery and the internal
jugular vein are closely associated with this space, particularly within the
carotid sheath.
Clinical Significance
Infection Risk: Infection in the lateral pharyngeal
space can be extremely serious due to its proximity to vital structures,
particularly the carotid sheath, which contains the internal carotid artery,
internal jugular vein, and cranial nerves.
Potential Complications:
Spread of Infection: Infections can spread from the
lateral pharyngeal space to other areas, including the mediastinum,
leading to life-threatening conditions such as mediastinitis.
Airway Compromise: Swelling or abscess formation in
this space can lead to airway obstruction, necessitating urgent medical
intervention.
Vascular Complications: The close relationship with
the carotid sheath means that infections can potentially involve the
carotid artery or jugular vein, leading to complications such as
thrombosis or carotid artery rupture.
Diagnosis and Management
Diagnosis:
Clinical examination may reveal signs of infection, such as fever,
neck swelling, and difficulty swallowing.
Imaging studies, such as CT scans, are often used to assess the
extent of infection and involvement of surrounding structures.
Management:
Antibiotics: Broad-spectrum intravenous antibiotics
are typically initiated to manage the infection.
Surgical Intervention: In cases of abscess
formation or significant swelling, surgical drainage may be necessary to
relieve pressure and remove infected material.
Itraconazole
Pharmacology
Itraconazole:
The drug may be given orally or intravenously.
Glycogen Metabolism
Biochemistry
Glycogen Metabolism
The formation of glycogen from glucose is called Glycogenesis
Glycogen is a polymer of glucose residues linked mainly by a(1→ 4) glycosidic linkages. There are a(1→6) linkages at branch points. The chains and branches are longer than shown. Glucose is stored as glycogen predominantly in liver and muscle cells
Glycogen Synthesis
Uridine diphosphate glucose (UDP-glucose) is the immediate precursor for glycogen synthesis. As glucose residues are added to glycogen, UDP-glucose is the substrate and UDP is released as a reaction product. Nucleotide diphosphate sugars are precursors also for synthesis of other complex carbohydrates, including oligosaccharide chains of glycoproteins, etc.
UDP-glucose is formed from glucose-1-phosphate and uridine triphosphate (UTP)
glucose-1-phosphate + UTP → UDP-glucose + 2 Pi
Cleavage of PPi is the only energy cost for glycogen synthesis (1P bond per glucose residue)
Glycogenin initiates glycogen synthesis. Glycogenin is an enzyme that catalyzes glycosylation of one of its own tyrosine residues.
Physiological regulation of glycogen metabolism
Both synthesis and breakdown of glycogen are spontaneous. If glycogen synthesis and phosphorolysis were active simultaneously in a cell, there would be a futile cycle with cleavage of 1 P bond per cycle
To prevent such a futile cycle, Glycogen Synthase and Glycogen Phosphorylase are reciprocally regulated, both by allosteric effectors and by covalent modification (phosphorylation)
Glycogen catabolism (breakdown)
Glycogen Phosphorylase catalyzes phosphorolytic cleavage of the →(1→4) glycosidic linkages of glycogen, releasing glucose-1-phosphate as the reaction product.
Glycogen (n residues) + Pi → glycogen (n-1 residues) + glucose-1-phosphate
The Major product of glycogen breakdown is glucose -1-phosphate
Fate of glucose-1-phosphate in relation to other pathways:
Phosphoglucomutase catalyzes the reversible reaction:
Glucose-1-phosphate → Glucose-6-phosphate
Stages of Development
PedodonticsStages of Development
Sensorimotor Stage (0-2 years):
Overview: In this stage, infants learn about the
world primarily through their senses and motor activities. They begin to
interact with their environment and develop basic cognitive skills.
Key Characteristics:
Object Permanence: Understanding that objects
continue to exist even when they cannot be seen.
Exploration: Infants engage in play by
manipulating objects, which helps them learn about cause and effect.
Symbolic Play: Even at this early stage,
children may begin to engage in simple forms of symbolic play, such
as pretending a block is a car.
Example in Dental Context: A child may play with
toys while sitting in the dental chair, exploring their environment and
becoming familiar with the setting.
Pre-operational Stage (2-6 years):
Overview: During this stage, children begin to use
language and engage in symbolic play, but their thinking is still
intuitive and egocentric. They struggle with understanding the
perspectives of others.
Key Characteristics:
Animism: The belief that inanimate objects have
feelings and intentions (e.g., thinking a toy can feel sad).
Constructivism: Children actively construct
their understanding of the world through experiences and
interactions.
Symbolic Play: Children engage in imaginative
play, using objects to represent other things (e.g., using a stick
as a sword).
Example: A child might pretend that a stuffed
animal is talking or has feelings, demonstrating animism.
Concrete Operational Stage (6-12 years):
Overview: In this stage, children begin to think
logically about concrete events. They can perform operations and
understand the concept of conservation (the idea that quantity doesn’t
change even when its shape does).
Key Characteristics:
Ego-centrism: While children in this stage are
less egocentric than in the pre-operational stage, they may still
struggle to see things from perspectives other than their own.
Logical Thinking: Children can organize objects
into categories and understand relationships between them.
Conservation: Understanding that certain
properties (like volume or mass) remain the same despite changes in
form or appearance.
Example: A child may understand that pouring water
from a short, wide glass into a tall, narrow glass does not change the
amount of water.
Formal Operational Stage (11-15 years):
Overview: In this final stage, adolescents develop
the ability to think abstractly, reason logically, and use deductive
reasoning. They can consider hypothetical situations and think about
possibilities.
Key Characteristics:
Abstract Thinking: Ability to think about
concepts that are not directly tied to concrete objects (e.g.,
justice, freedom).
Hypothetical-Deductive Reasoning: Ability to
formulate hypotheses and systematically test them.
Metacognition: Awareness and understanding of
one’s own thought processes.
Example: An adolescent can discuss moral dilemmas
or scientific theories, considering various outcomes and implications.
Gingival Crevicular Fluid
PeriodontologyGingival Crevicular Fluid (GCF)
Gingival crevicular fluid is an inflammatory exudate found in the gingival
sulcus. It plays a significant role in periodontal health and disease.
A. Characteristics of GCF
Glucose Concentration: The glucose concentration in GCF
is 3-4 times greater than that in serum, indicating
increased metabolic activity in inflamed tissues.
Protein Content: The total protein content of GCF is
much less than that of serum, reflecting its role as an inflammatory
exudate.
Inflammatory Nature: GCF is present in clinically
normal sulci due to the constant low-grade inflammation of the gingiva.
B. Drugs Excreted Through GCF
Tetracyclines and Metronidazole: These antibiotics are
known to be excreted through GCF, making them effective for localized
periodontal therapy.
C. Collection Methods for GCF
GCF can be collected using various techniques, including:
Absorbing Paper Strips/Blotter/Periopaper: These strips
absorb fluid from the sulcus and are commonly used for GCF collection.
Twisted Threads: Placing twisted threads around and
into the sulcus can help collect GCF.
Micropipettes: These can be used for precise collection
of GCF in research settings.
Intra-Crevicular Washings: Flushing the sulcus with a
saline solution can help collect GCF for analysis.
Space Maintainers
PedodonticsSpace Maintainers: A fixed or removable appliance designed
to maintain the space left by a prematurely lost tooth, ensuring proper
alignment and positioning of the permanent dentition.
Importance of Primary Teeth
Primary teeth serve as the best space maintainers for the permanent
dentition. Their presence is crucial for guiding the eruption of permanent
teeth and maintaining arch integrity.
Consequences of Space Loss
When a tooth is lost prematurely, the space can change significantly within a
six-month period, leading to several complications:
Loss of Arch Length: This can result in crowding of the
permanent dentition.
Impaction of Permanent Teeth: Teeth may become impacted
if there is insufficient space for their eruption.
Esthetic Problems: Loss of space can lead to visible
gaps or misalignment, affecting a child's smile.
Malocclusion: Improper alignment of teeth can lead to
functional issues and bite problems.
Indications for Space Maintainers
Space maintainers are indicated in the following situations:
If the space shows signs of closing.
If using a space maintainer will simplify future orthodontic treatment.
If treatment for malocclusion is not indicated at a later date.
When the space needs to be maintained for two years or more.
To prevent supra-eruption of opposing teeth.
To improve the masticatory system and restore dental health.
Contraindications for Space Maintainers
Space maintainers should not be used in the following situations:
If radiographs show that the succedaneous tooth will erupt soon.
If one-third of the root of the succedaneous tooth is already calcified.
When the space left is greater than what is needed for the permanent
tooth, as indicated radiographically.
If the space shows no signs of closing.
When the succedaneous tooth is absent.
Classification of Space Maintainers
Space maintainers can be classified into two main categories:
1. Fixed Space Maintainers
These are permanently attached to the teeth and cannot be removed
by the patient. Examples include band and loop space maintainers.
Common types include:
Band and Loop Space Maintainer:
A metal band is placed around an adjacent tooth, and a wire loop
extends into the space of the missing tooth. This is commonly used
for maintaining space after the loss of a primary molar.
Crown and Loop Space Maintainer:
Similar to the band and loop, but a crown is placed on the
adjacent tooth instead of a band. This is used when the adjacent
tooth requires a crown.
Distal Shoe Space Maintainer:
This is used when a primary second molar is lost before the
eruption of the permanent first molar. It consists of a metal band
on the first molar with a metal extension (shoe) that guides the
eruption of the permanent molar.
Transpalatal Arch:
A fixed appliance that connects the maxillary molars across the
palate. It is used to maintain space and prevent molar movement.
Nance Appliance:
Similar to the transpalatal arch, but it has a small acrylic
button that rests against the anterior palate. It is used to
maintain space in the upper arch.
2. Removable Space Maintainers
These can be taken out by the patient and are typically used when more
than one tooth is lost. They can also serve to replace occlusal function and
improve esthetics.
Common types include:
Removable Partial Denture:
A prosthetic device that replaces one or more missing teeth and
can be removed by the patient. It can help maintain space and
restore function and esthetics.
Acrylic Space Maintainer:
A simple acrylic appliance that can be used to maintain space.
It is often used in cases where esthetics are a concern.
Functional Space Maintainers:
These are designed to provide occlusal function while
maintaining space. They may include components that allow for
chewing and speaking.
Types of Removable Space Maintainers
Non-functional: Typically used when more than one tooth
is lost.
Functional: Designed to provide occlusal function.
Advantages of Removable Space Maintainers
Easy to clean and maintain proper oral hygiene.
Maintains vertical dimension.
Can be worn part-time, allowing circulation of blood to soft tissues.
Creates room for permanent teeth.
Helps prevent the development of tongue thrust habits into the
extraction space.
Disadvantages of Removable Space Maintainers
May be lost or broken by the patient.
Uncooperative patients may not wear the appliance.
Lateral jaw growth may be restricted if clasps are incorporated.
May cause irritation of the underlying soft tissues.