NEET MDS Synopsis
BONE
Anatomy
BONE
A rigid form of CT, Consists of matrix and cells
Matrix contains:
organic component 35% collagen fibres
inorganic salts 65% calcium phosphate (58,5%), calcium carbonate (6,5%)
2 types of bone - spongy (concellous)
compact (dense)
Microscopic elements are the same
Spongy bone consists of bars (trabeculae) which branch and unite to form a meshwork
Spaces are filled with bone marrow
Compact bone appears solid but has microscopic spaces
In long bones the shaft is compact bone
And the ends (epiphysis) consists of spongy bone covered with compact bone
Flat bones consists of 2 plates of compact bone with spongy bone in-between
Periosteum covers the bone
Endosteum lines marrow cavity and spaces
These 2 layers play a role in the nutrition of bone tissue
They constantly supply the bone with new osteoblasts for the repair and growth of bone
Microscopically
The basic structural unit of bone is the Haversian system or osteon
An osteon consists of a central Haversian canal
- In which lies vessels nerves and loose CT
- Around the central canal lies rings of lacunae
- A lacuna is a space in the matrix in which lies the osteocyte
- The lacunae are connected through canaliculi which radiate from the lacunae
- In the canaliculi are the processes of the osteocytes
- The canaliculi link up with one another and also with the Haversian canal
- The processes communicate with one another in the canaliculi through gap junctions
- Between two adjacent rows of lacunae lie the lamellae, 5-7µm thick
- In three dimensions the Haversian systems are cylindrical
- The collagen fibres lie in a spiral in the lamellae
- Perpendicular to the Haversian canals are the Volkman's canals
- They link up with the marrow cavity and the Haversian canals
- Some lamellae do not form part of a Haversian system
- They are the:
- Inner circumferential lamellae - around the marrow cavity
- Outer circumferential lamellae - underneath the outer surface of the bone
- Interstitial lamellae - between the osteons
Endosteum
Lines all cavities like marrow spaces, Haversian- and Volkman's canals
Consists of a single layer of squamous osteoprogenitor cells with a thin reticular CT layer underneath it
Continuous with the inner layer of periosteum
Covers the trabeculae of spongy bone
Cells differentiate into osteoblasts (like the cells of the periosteum)
Periosteum
Formed by tough CT
2 layers
Outer fibrous layer: Thickest, Contains collagen fibres,
Some fibres enter the bone - called Sharpey's fibres
Contains blood vessels.
Also fibrocytes and the other cells found in common CT
Inner cellular layer
Flattened cells (continuous with the endosteum)
Can divide and differentiate into osteoprogenitor cells
spindle shaped
little amount of rough EPR
poorly developed Golgi complex
play a prominent role in bone growth and repair
Osteoblasts
Oval in shape, Have thin processes, Rough EPR in one part of the cell (basophilic)
On the other side is the nucleus, Golgi and the centrioles in the middle, Form matrix
Become trapped in the matrix
Osteocytes
Mature cells, Less basophilic than the osteoblasts, Lie trapped in the lacunae, Their processes lie in the canaliculi, Processes communicate with one another through gap junctions, Substances (nutrients, waste products) are passed on from cell to cell
Osteoclasts
Very large, Multinucleate (up to 50), On inner and outer surface of bone, Lie in depressions on the surface called Howships lacunae, The cell surface facing the bone has short irregular processes
Acidophylic
Has many lysosomes, polyribosomes and rough EPR
Lysosomal enzymes are secreted to digest the bone
Resorbs the organic part of bone
Histogenesis
Two types of bone development.
- intramembranous ossification
- endochondral ossification
In both these types of bone development temporary primary bone is deposited which is soon replaced by secondary bone. Primary bone has more osteocytes and the mineral content is lower.
CHEMICAL AGENTS
General Microbiology
CHEMICAL AGENTS
Chlorine and iodine are most useful disinfectant Iodine as a skin disinfectant and chlorine as a water disinfectant have given consistently magnificent results. Their activity is almost exclusively bactericidal and they are effective against sporulating organisms also.
Mixtures of various surface acting agents with iodine are known as iodophores and these are used for the sterilization of dairy products.
Apart from chlorine, hypochlorite, inorganic chioramines are all good disinfectants but they act by liberating chlorine.
Hydrogen peroxide in a 3% solution is a harmless but very weak disinfectant whose primary use is in the cleansing of the wound.
Potassium permanganate is another oxidising agent which is used in the treatment of urethntzs.
Formaldehyde — is one of the least selective agent acting on proteins. It is a gas that is usually employed as its 37% solution, formalin.
When used in sufficiently high concentration it destroys the bacteria and their spores.
Classification of chemical sterilizing agents
Chemical disinfectant
Interfere with membrane functions
• Surface acting agents : Quaternary ammonium, Compounds, Soaps and fatty acids
• Phenols : Phenol, cresol, Hexylresorcinol
• Organic solvent : Chloroform, Alcohol
Denatures proteins
• Acids and alkalies : Organic acids, Hydrochloric acid , Sulphuric acid
Destroy functional groups of proteins
• Heavy metals : Copper, silver , Mercury
• Oxidizing agents: Iodine, chlorine, Hydrogen peroxide
• Dyes : Acridine orange, Acriflavine
• Alkylating agents : Formaldehyde, Ethylene oxide
Applications and in-use dilution of chemical disinfectants
Alcohols : Skin antiseptic Surface disinfectant, Dilution used 70%
Mercurials : Skin antiseptic Surface disinfectant Dilution Used 0.1 %
Silver nitrate : Antiseptic (eyes and burns) Dilution Used 1 %
Phenolic compound : Antiseptic skin washes Dilution Used .5 -5 %
Iodine : Disinfects inanimate object, Skin antiseptic Dilution used 2%
Chlorine compounds : Water treatment Disinfect inanimate objects , Dillution used 5 %
Quaternary ammonium Compounds : Skin antiseptic , Disinfects inanimate object, Dilution Used < 1 %
Glutaraldehyde: Heat sensitve instruments, Dilution used 1-2 %
Cold sterilization can be achieved by dipping the precleaned instrument in 2% solution of gluteraldehyde for 15-20 minutes. This time is sufficient to kill the vegetative form as well as spores ofthe organisms that are commonly encountered in the dentistry.
Ethylene oxide is an a agent extensively used in gaseous sterilization. It is active against all kinds of bacteria and their spores. but its greatest utility is in sterilizing those objects which are damaged by heat (e.g. heart lung machine). It is also used to sterlise fragile, heat sensitive equipment, powders as well as components of space crafts.
Evaluation of Disinfectants
Two methods which are widely employed are:
Phenol coefficient test, Kelsey -Sykes test
These tests determine the capacity of disinfectant as well as their ability to retain their activity.
Other coxibs
Pharmacology
Valdecoxib
used in the treatment of osteoarthritis, acute pain conditions, and dysmenorrhoea
Etoricoxib new COX-2 selective inhibitor
VITAMINS
Biochemistry
VITAMINS
Based on solubility Vitamins are classified as either fat-soluble (lipid soluble) or water-soluble. Vitamins A, D, E and K are fat-soluble
Vitamin C and B is water soluble.
B-COMPLEX VITAMINS
Eight of the water-soluble vitamins are known as the vitamin B-complex group: thiamin (vitamin B1), riboflavin (vitamin B2), niacin (vitamin B3), vitamin B6 (pyridoxine), folate (folic acid), vitamin B12, biotin and pantothenic acid.
Valvular disease
General Pathology
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.
Measles (rubeola)
General Pathology
Measles (rubeola)
-incubation period 7 to 14 days
-begins with fever (up to 40 degrees C), cough, conjunctivitis (photophobia is first sign), and coryza (excessive mucous production)Æfollowed by Koplik's spots (red with white center) in the mouth, posterior cervical Lymphadenopathy, and a generalized, blanching, maculopapular, brownish-pink rash (viral induced vasculitis) beginning at the hairline and extending down over the body which gradually resolves in 5 days with some desquamation.
Intubation
General SurgeryIntubation
Intubation is a critical procedure in airway management, and the choice of
technique—oral intubation, nasal intubation, or tracheostomy—depends on the
clinical situation, patient anatomy, and specific indications or
contraindications.
Indications for Each Intubation Technique
1. Oral Intubation
Oral intubation is often the preferred method in emergency situations and
when nasal intubation is contraindicated. Indications include:
Emergent Intubation: Situations such as cardiopulmonary
resuscitation (CPR), unconsciousness, or apnea.
Oral or Mandibular Trauma: When there is significant
trauma to the oral cavity or mandible that may complicate nasal access.
Cervical Spine Conditions: Conditions such as
ankylosis, arthritis, or trauma that may limit neck movement.
Gagging and Vomiting: In patients who are unable to
protect their airway due to these conditions.
Agitation: In cases where the patient is agitated and
requires sedation and airway protection.
2. Nasal Intubation
Nasal intubation is indicated in specific situations where oral intubation
may be difficult or impossible. Indications include:
Nasal Obstruction: When there is a blockage in the oral
route.
Paranasal Disease: Conditions affecting the nasal
passages that may necessitate nasal access.
Awake Intubation: In cases where the patient is
cooperative and can tolerate the procedure.
Short (Bull) Neck: In patients with anatomical
challenges that make oral intubation difficult.
3. Tracheostomy
Tracheostomy is indicated for long-term airway management or when other
methods are not feasible. Indications include:
Inability to Insert Translational Tube: When oral or
nasal intubation fails or is not possible.
Need for Long-Term Definitive Airway: In patients
requiring prolonged mechanical ventilation or airway support.
Obstruction Above Cricoid Cartilage: Conditions that
obstruct the airway at or above the cricoid level.
Complications of Translational Intubation: Such as
glottic incompetence or inability to clear tracheobronchial secretions.
Sleep Apnea Unresponsive to CPAP: In patients with
severe obstructive sleep apnea who do not respond to continuous positive
airway pressure (CPAP) therapy.
Facial or Laryngeal Trauma: Structural
contraindications to translaryngeal intubation.
Contraindications for Nasal Intubation
Severe Fractures of the Midface: Nasal intubation is
contraindicated due to the risk of further injury and complications.
Nasal Fractures: Similar to midface fractures, nasal
fractures can complicate nasal intubation and increase the risk of injury.
Basilar Skull Fractures: The risk of entering the
cranial cavity or causing cerebrospinal fluid (CSF) leaks makes nasal
intubation unsafe in these cases.
Contraindications for Oral Intubation
Severe Facial or Oral Trauma:
Significant injuries to the face, jaw, or oral cavity may make
oral intubation difficult or impossible and increase the risk of
further injury.
Obstruction of the Oral Cavity:
Conditions such as large tumors, severe swelling, or foreign
bodies that obstruct the oral cavity can prevent successful
intubation.
Cervical Spine Instability:
Patients with unstable cervical spine injuries may be at risk of
further injury if neck extension is required for intubation.
Severe Maxillofacial Deformities:
Anatomical abnormalities that prevent proper visualization of
the airway or access to the trachea.
Inability to Open the Mouth:
Conditions such as trismus (lockjaw) or severe oral infections
that limit mouth opening can hinder intubation.
Severe Coagulopathy:
Patients with bleeding disorders may be at increased risk of
bleeding during the procedure.
Anticipated Difficult Airway:
In cases where the airway is expected to be difficult to manage,
alternative methods may be preferred.
Contraindications for Tracheostomy
Severe Coagulopathy:
Patients with significant bleeding disorders may be at risk for
excessive bleeding during the procedure.
Infection at the Site of Incision:
Active infections in the neck or tracheostomy site can increase the
risk of complications and should be addressed before proceeding.
Anatomical Abnormalities:
Significant anatomical variations or deformities in the neck that
may complicate the procedure or increase the risk of injury to
surrounding structures.
Severe Respiratory Distress:
In some cases, if a patient is in severe respiratory distress,
immediate intubation may be prioritized over tracheostomy.
Patient Refusal:
If the patient is conscious and refuses the procedure, it should not
be performed unless there is an immediate life-threatening situation.
Inability to Maintain Ventilation:
If the patient cannot be adequately ventilated through other means,
tracheostomy may be necessary, but it should be performed with caution.
Unstable Hemodynamics:
Patients with severe hemodynamic instability may not tolerate the
procedure well, and alternative airway management strategies may be
required.
Retention
OrthodonticsRetention
Definition: Retention refers to the phase following active
orthodontic treatment where appliances are used to maintain the corrected
positions of the teeth. The goal of retention is to prevent relapse and ensure
that the teeth remain in their new, desired positions.
Types of Retainers
Fixed Retainers:
Description: These are bonded to the lingual
surfaces of the teeth, typically the anterior teeth, to maintain their
positions.
Advantages: They provide continuous retention
without requiring patient compliance.
Disadvantages: They can make oral hygiene more
challenging and may require periodic replacement.
Removable Retainers:
Description: These are appliances that can be taken
out by the patient. Common types include:
Hawley Retainer: A custom-made acrylic plate
with a wire framework that holds the teeth in position.
Essix Retainer: A clear, plastic retainer that
fits over the teeth, providing a more aesthetic option.
Advantages: Easier to clean and can be removed for
eating and oral hygiene.
Disadvantages: Their effectiveness relies on
patient compliance; if not worn as prescribed, relapse may occur.
Duration of Retention
The duration of retention varies based on individual cases, but it is
generally recommended to wear retainers full-time for a period (often
several months to a year) and then transition to nighttime wear for an
extended period (often several years).
Long-term retention may be necessary for some patients, especially those
with a history of dental movement or specific malocclusions.