NEET MDS Synopsis
Doxycycline
Pharmacology
Doxycycline
Commonly prescribed for infections and to treat acne. treat urinary tract infections, gum disease, and other bacterial infections such as gonorrhea and chlamydia., as a prophylactic treatment for infection by Bacillus anthracis (anthrax). It is also effective against Yersinia pestis and malaria.
Alcoholic cirrhosis
General Pathology
Alcoholic (nutritional, Laennec’s) cirrhosis
Pathology
Liver is at first enlarged (fatty change), then return to normal size and lastly, it becomes slightly reduced in size (1.2 kg or more).
- Cirrhosis is micronodular then macronodular then mixed.
M/E
Hepatocytes:- show fatty change that decreases progressively. Few hepatocytes show increased intracytoplasmic haemochromatosis.
b. Fibrous septa:- Regular margins between it and regenerating nodules.
-Moderate lymphocytic infiltrate.
– Slight bile ductular proliferation.
Prognosis:- It Progresses slowly over few years.
Flucloxacillin
Pharmacology
Flucloxacillin, important even now for its resistance to beta-lactamases produced by bacteria such as Staphylococcus species. It is still no match for MRSA (Methicillin Resistant Staphylococcus aureus).
The last in the line of true penicillins were the antipseudomonal penicillins, such as ticarcillin, useful for their activity against Gram-negative bacteria
Intraligamentary Injection
Oral and Maxillofacial SurgeryIntraligamentary Injection and Supraperiosteal Technique
Intraligamentary Injection
The intraligamentary injection technique is a simple and effective
method for achieving localized anesthesia in dental procedures. It
requires only a small volume of anesthetic solution and produces rapid
onset of anesthesia.
Technique:
Needle Placement:
The needle is inserted into the gingival sulcus, typically on
the mesial surface of the tooth.
The needle is then advanced along the root surface until
resistance is encountered, indicating that the needle is positioned
within the periodontal ligament.
Anesthetic Delivery:
Approximately 0.2 ml of anesthetic solution is deposited into
the periodontal ligament space.
For multirooted teeth, injections should be made both mesially
and distally to ensure adequate anesthesia of all roots.
Considerations:
Significant pressure is required to express the anesthetic solution
into the periodontal ligament, which can be a factor to consider during
administration.
This technique is particularly useful for localized procedures where
rapid anesthesia is desired.
Supraperiosteal Technique (Local Infiltration)
The supraperiosteal injection technique is commonly used for
achieving anesthesia in the maxillary arch, particularly for
single-rooted teeth.
Technique:
Anesthetic Injection:
For the first primary molar, the bone overlying the tooth is
thin, allowing for effective anesthesia by injecting the anesthetic
solution opposite the apices of the roots.
Challenges with Multirooted Teeth:
The thick zygomatic process can complicate the anesthetic
delivery for the buccal roots of the second primary molar and first
permanent molars.
Due to the increased thickness of bone in this area, the
supraperiosteal injection at the apices of the roots of the second
primary molar may be less effective.
Supplemental Injection:
To enhance anesthesia, a supplemental injection should be
administered superior to the maxillary tuberosity area to block the
posterior superior alveolar nerve.
This additional injection compensates for the bone thickness and
the presence of the posterior middle superior alveolar nerve plexus,
which can affect the efficacy of the initial injection.
NEUROHISTOLOGY
Anatomy
NEUROHISTOLOGY
The nervous system develops embryologically from ectoderm, which forms the neural plate
Successive growth and folding of the plate results in the formation of the primitive neural tube.
The neuroblasts in the wall of the tube differentiates into 3 cell types:
Neurons: conduction of impulses
Neuroglial cells: connective tissue and support of CNS
Ependymal cells: Lines the lumen of the tube.
- Specialized neuro-ectodermal cells which lines the ventricles of the adult brain
- Essentially also a neuroglial cell
Basic Unit = neuron
Exhibits irritability (excitability) and conductivity
A typical neurons consists of:
Cell body : Has nucleus (karyon) and surrounding cytoplasm (perikaryon) which contains organelles cell's vitality
Dendrites: Several short processes
Axon:One large process
Terminates in twig like branches (telodendrons)
May also have collateral branches projecting along its course. These exit at nodes of Ranvier
Axon enveloped in a sheath, and together forms the nerve fiber
Classification:
May be done in different ways, i.e.
Functional = afferent, efferent, preganglionic, postganglionic, etc.
Morphological = shape, processes, etc
A typical morphological classification is as follows
a. Unipolar: Has one process only Not found in man
b. Bipolar (so-called ganglion cell):Has two processes Found in sensory systems, e.g. retina olfactory system
c. Multipolar: Has several process Most common in CNS
Cell bodies vary in shape, e.g. stellate (star) , pyramidal
d. Pseudo-unipolar: Essentially bipolar neurons, but processes have swung around cb and fused with each other. They therefore enter and leave at one pole of the cell.
Typical neuron:
- Has 2 or more dendrites
Close to the cb the cytoplasm of dendrites has Nissl granules as well as mitochondria
Only one axon Arises from axon hillock, Devoid of Nissl granules, Encased in myelin sheath
No additional covering except for occasional foot processes of neuroglial cells
May branch at right angles
Branches at a node of Ranvier is known as a collateral
Ends of axons break up into tree-like branches, known as telodendria
Axons may be short (Golgi Type II) e.g. internuncial long (Golgi Type I) e.g. pyramidal neuron
Nucleus Central position Large and spherical
Chromatin is extended and thus not seen in LM. This allows the nucleolus to be prominent
Cytoplasm (perikaryon)
Surrounds nucleus May be large or small, shape may be round, oval, flattened, pyramidal, etc
Contains aggregates Nissl granules(Bodies) which is also sometimes referred to as rhomboid flakes
aggregation of membranes and cisternae of rough endoplasmic reticulum (RER)
numerous ribosomes and polyribosomes scattered between cisternae
(Polyribosome = aggregate of free ribosomes clumped together)
responsible for ongoing synthesis of new cytoplasm and cytoplasmic substances
needed for conduction of impulses
highly active in cell protein synthesis
resultant loss of power to divide which is characteristic of neurons
- Golgi network surrounding nucleus (seen in EM only)
- Fibrils made up of:
- neurofilaments
- microtubules
Tubules involved in:
1. plasmic transport
2. maintenance of cell shape
3. essential for growth and elongation of axons and dendrites
Neurofilament:
1. provide skeletal framework
2. maintenance of cell shape
3. possible role in axonal transport
(Axonal [axoplasmic; plasmic] transport may be antero- or retrograde. Anterograde transport via neurotubules is fast and moves neurotransmitters. Retrograde transport is slow and is the reason why viruses and bacteria can attack and destroy cell bodies. E.g. polio in the ventral columns and syphilis in the dorsal columns).
- Numerous mitochondria
- Neurons lack ability to store glycogen and are dependent for energy on circulating glucose
Impulses are conducted in one direction only
Dendrites conduct towards the cb
Axons conduct away from cb
Synapses:
- Neurons interconnect by way of synapses
- Normally the telodendria of an axon synapse with the dendrites of a succeeding axon
axo-dendritic synapse
This is usually excitatory
- Other types of synapses are:
axo-axonic
May be excitatory and/or inhibitory
axo-somatic
May be excitatory and/or inhibitory
dendrodendritic
Usually inhibitory
- Synapses are not tight junctions but maintain a narrow space the so-called synaptic cleft
- The end of an telodendron is usually enlarged (bouton) and contains many synaptic vesicles,
mitochondrion, etc. Its edge that takes part in the synapse is known as the postsynaptic membrane and no
vesicles are seen in this area
- Synapses may be chemical (as above) or electrical as in the ANS supplying smooth muscle cells subjacent to adjacent fibres
Gray and White Matter of Spinal Cord:
- Gray matter contains:
- cb's (somas) of neurons
- neuroglial cells
- White matter contains:
- vast number of axons
- no cb's
- colour of white matter due to myelin that ensheathes axons
Myelin:
- Non-viable fatty material contains phospholipids, cholesterol and some proteins
- Soluble and not seen in H&E-sections because it has become dissolved in the process, thus leaving empty spaces around the axons
- Osmium tetroxide (OsO4) fixes myelin and makes it visible by staining it black. Seen as concentric rings in cross section
- Myelin sheath (neurolemma) is formed by two types of cells
- Within the CNS by Oligodendrocytes
- On the peripheral neurons system by Schwann cells
- Sheath is formed by being wrapped around the axon in a circular fashion by both types of cells
Neuroglial Cells:
- Forms roughly 40% of CNS volume
- May function as: 1. support
2. nurture ("feeding")
3. maintain
Types of glial cells:
Oligodendrocytes:
- Small dark stained dense nucleus
- Analogue of Schwann cell in peripheral nervous system
- Has several processes which forms internodal segments of several fibres (one cell ensheathes more than one axon)
- Provides myelin sheaths in CNS
- Role in nurturing (feeding) of cells
Astrocytes:
Protoplasmic astrocytes:
- found in gray matter
- round cell body
- large oval nucleus with prominent nucleolus
- large thick processes
- processes are short but profusely branched
- perivascular and perineurial foot processes
- sometimes referred to as mossy fibres
Fibrous Astrocytes:
- found in white matter
- polymorphic cells body
- large oval nucleus
- long thin processes
Microglia:
- Neural macrophages
- smallest of the glial cells
- intense dark stained nucleus
- conspicuously fine processes which has numerous short branches
Cerebral Cortex:
Consists of six layers which are best observed in the cortex of the hippocampus
From superficial to deep:
- Molecular layer:
- Has few cells and many fibres of underlying cells
- Outer granular layer:
- Many small nerve cells
- Pyramidal layer:
- Pyramidally-shaped cells bodies
- Inner granular layer:
- Smaller cells and nerve fibres
- Internal (inner) pyramidal layer:
- Pyramidal cells bodies
- Very large in the motor cortex and known as Betz-cells
- Polymorphic layer:
- Cells with many shapes
Cerebellar Cortex:
Consists of three layers
Connections are mainly inhibitory
From superficial to deep
- Outer molecular layer:
- Few cells and many fibres
- Purkinje layer:
- Huge flask-shaped cells that are arranged next to one another
- Inner granular layer:
- Many small nerve cells
Motor endplate:
Seen in periphery on striated muscle fibres
- known as boutons
- has no continuous myelin covering from the Schwann cells
- passes through perimysium of muscle fiber to "synapse"
- multiple synaptic gutter (fold) in sarcoplasma of muscle fiber beneath bouton
- contains numerous synaptic vesicles and mitochondria
Ganglia:
- Sensory Ganglia:
(e.g. trigeminal nerve, ganglia and dorsal root ganglia)
- No synapse (trophic unit)
- pseudo-unipolar neurons
- centrally located nucleus
- spherical smooth border
- conspicuous axon hillock
- Surrounded by cuboidal satellite cells (Schwann cells)
- Covered by spindle shaped capsular cells of delicate collagen which forms the endoneurium
- Visceral and Motor Ganglia (Sympathetic and Parasympathetic):
- Synapse present
- Ratio of preganglionic: postganglionic fibres
1. Sympathetic 1:30
Therefore excitatory and catabolic
2. Parasympathetic 1:2
Therefore anabolic
Except in Meissner and Auerbach's plexuses where ratio is 1:1000 '2 because of parasympathetic component's involvement in digestion
- Preganglionic axons are myelinated (e.g. white communicating rami)
- Postganglionic axon are non-myelinated (e.g. gray communicating rami)
- small multipolar cell body
- excentrally located nucleus
- Inconspicuous axon hillock
- satellite cells few or absent
- few capsular cells
Digit Sucking and Infantile Swallow
PedodonticsDigit Sucking and Infantile Swallow
Introduction to Digit Sucking
Digit sucking is a common behavior observed in infants and young children. It
can be categorized into two main types based on the underlying reasons for the
behavior:
Nutritive Sucking
Definition: This type of sucking occurs during
feeding and is essential for nourishment.
Timing: Nutritive sucking typically begins in the
first few weeks of life.
Causes: It is primarily associated with feeding
problems, where the infant may suck on fingers or digits as a substitute
for breastfeeding or bottle-feeding.
Non-Nutritive Sucking
Definition: This type of sucking is not related to
feeding and serves other psychological or emotional needs.
Causes: Non-nutritive sucking can arise from
various psychological factors, including:
Hunger
Satisfying the innate sucking instinct
Feelings of insecurity
Desire for attention
Examples: Common forms of non-nutritive sucking
habits include:
Thumb or finger sucking
Pacifier sucking
Non-Nutritive Sucking Habits (NMS Habits)
Characteristics: Non-nutritive sucking habits are often
comforting for children and can serve as a coping mechanism in stressful
situations.
Implications: While these habits are generally normal
in early childhood, prolonged non-nutritive sucking can lead to dental
issues, such as malocclusion or changes in the oral cavity.
Infantile Swallow
Definition: The infantile swallow is a specific pattern
of swallowing observed in infants.
Characteristics:
Active contraction of the lip musculature.
The tongue tip is positioned forward, making contact with the lower
lip.
Minimal activity of the posterior tongue and pharyngeal musculature.
Posture: The tongue-to-lower lip contact is so
prevalent in infants that it often becomes their resting posture. This can
be observed when gently moving the infant's lip, causing the tongue tip to
move in unison, suggesting a strong connection between the two.
Developmental Changes: The sucking reflex and the
infantile swallow typically diminish and disappear within the first year of
life as the child matures and develops more complex feeding and swallowing
patterns.
Articulations and Movement
Anatomy
Articulations
Classified according to their structure, composition,and movability
• Fibrous joints-surfaces of bones almost in direct contact with limited movement
o Syndesmosis-two bones united by interosseous ligaments
o Sutures-serrated margins of bones united by a thin layer of fibrous tissue
o Gomphosis-insertion of a cone-shaped process into a socket
• Cartilaginous joints-no joint cavity and contiguous bones united by cartilage
o Synchondrosis-ends of two bones approximated by hyaline cartilage
o Symphyses-approximating bone surfaces connected by fibrocartilage
• Synovial joints-approximating bone surfaces covered with cartilage; may be separated by a disk; attached by ligaments
o Hinge-permits motion in one plane only
o Pivot-permits rotary movement in which a ring rotates around a central axis
o Saddle-opposing surfaces are convexconcave. allowing great freedom of motion
o Ball and socket - capable of movement in an infinite number of axes; rounded head of one bone moves in a cuplike cavity of the approximating bone
Bursae
• Sacs filled with synovial fluid that are present where tendons rub against bone or where skjn rubs across bone
• Some bursae communicate with a joint cavity
• Prominent bursae found at the elbow. hip, and knee'
Movements
• Gliding
o Simplest kind of motion in a joint
o Movement on a joint that does not involve any angular or rotary motions
• Flexion-decreases the angle formed by the union of two bones
• Extension-increases the angle formed by the union of two bones
• Abduction-occurs by moving part of the appendicular skeleton away from the median plane of the body
• Adduction-occurs by moving part of the appendicular skeleton toward the median plane of the body
• Circumduction
o Occurs in ball-and-socket joints
o Circumscribes the conic space of one bone by the other bone
• Rotation-turning on an axis without being displaced from that axis
Efficiency in Heat Sterilization
Oral and Maxillofacial SurgeryTests for Efficiency in Heat Sterilization – Sterilization Monitoring
Effective sterilization is crucial in healthcare settings to ensure the
safety of patients and the efficacy of medical instruments. Various monitoring
techniques are employed to evaluate the sterilization process, including
mechanical, chemical, and biological parameters. Here’s an overview of these
methods:
1. Mechanical Monitoring
Parameters Assessed:
Cycle Time: The duration of the sterilization
cycle.
Temperature: The temperature reached during the
sterilization process.
Pressure: The pressure maintained within the
sterilizer.
Methods:
Gauges and Displays: Observing the gauges or
digital displays on the sterilizer provides real-time data on the cycle
parameters.
Recording Devices: Some tabletop sterilizers are
equipped with recording devices that print out the cycle parameters for
each load.
Interpretation:
While correct readings indicate that the sterilization conditions
were likely met, incorrect readings can signal potential issues with the
sterilizer, necessitating further investigation.
2. Biological Monitoring
Spore Testing:
Biological Indicators: This involves using spore
strips or vials containing Geobacillus stearothermophilus,
a heat-resistant bacterium.
Frequency: Spore testing should be conducted weekly to
verify the proper functioning of the autoclave.
Interpretation: If the spores are killed after the
sterilization cycle, it confirms that the sterilization process was
effective.
3. Thermometric Testing
Thermocouple:
A thermocouple is used to measure temperature at two locations:
Inside a Test Pack: A thermocouple is placed
within a test pack of towels to assess the temperature reached in
the center of the load.
Chamber Drain: A second thermocouple measures
the temperature at the chamber drain.
Comparison: The readings from both locations are
compared to ensure that the temperature is adequate throughout the load.
4. Chemical Monitoring
Brown’s Test:
This test uses ampoules containing a chemical indicator that changes
color based on temperature.
Color Change: The indicator changes from red
through amber to green at a specific temperature, confirming that the
required temperature was reached.
Autoclave Tape:
Autoclave tape is printed with sensitive ink that changes color when
exposed to specific temperatures.
Bowie-Dick Test: This test is a specific
application of autoclave tape, where two strips are placed on a piece of
square paper and positioned in the center of the test pack.
Test Conditions: When subjected to a temperature
of 134°C for 3.5 minutes, uniform color development
along the strips indicates that steam has penetrated the load
effectively.