NEET MDS Synopsis
Prostaglandines
Pharmacology
Prostaglandines:
Every cell in the body is capable of synthesizing one or more types of PGS. The four major group of PGs are E, F, A, and B.
Pharmacological actions:
stimulation of cyclicAMP production and calcium use by various cells
CVS
PGE2 acts as vasodilator; it is more potent hypotensive than Ach and histamine
Uterous
PGE2 and PGF2α Contract human uterus
Bronchial muscle
PGF2α and thromboxan A2 cause bronchial muscle contraction.
PGE2 & PGI2 cause bronchial muscle dilatation
GIT: PGE2 and PGF2α cause colic and watery diarrhoea
Platelets
Thromboxan A2 is potent induce of platelets aggregation
Kidney
PGE2 and PGI2 increase water, Na ion and K ion excretion (act as diuresis) that cause renal vasodilatation and inhibit
tubular reabsorption
USE
PGI2: Epoprostenol (inhibits platelets aggregation)
PGE1: Alprostadil (used to maintain the potency of arterioles in neonates with congenital heart defects).
PGE2: Dinoproste (used as pessaries to induce labor)
Synthetic analogue of PGE1: Misoprostol (inhibit the secretion of HCl).
Control of processes in the stomach
PhysiologyControl of processes in the stomach:
The stomach, like the rest of the GI tract, receives input from the autonomic nervous system. Positive stimuli come from the parasympathetic division through the vagus nerve. This stimulates normal secretion and motility of the stomach. Control occurs in several phases:
Cephalic phase stimulates secretion in anticipation of eating to prepare the stomach for reception of food. The secretions from cephalic stimulation are watery and contain little enzyme or acid.
Gastric phase of control begins with a direct response to the contact of food in the stomach and is due to stimulation of pressoreceptors in the stomach lining which result in ACh and histamine release triggered by the vagus nerve. The secretion and motility which result begin to churn and liquefy the chyme and build up pressure in the stomach. Chyme surges forward as a result of muscle contraction but is blocked from entering the duodenum by the pyloric sphincter. A phenomenon call retropulsion occurs in which the chyme surges backward only to be pushed forward once again into the pylorus. The presence of this acid chyme in the pylorus causes the release of a hormone called gastrin into the bloodstream. Gastrin has a positive feedback effect on the motility and acid secretion of the stomach. This causes more churning, more pressure, and eventually some chyme enters the duodenum.
Intestinal phase of stomach control occurs. At first this involves more gastrin secretion from duodenal cells which acts as a "go" signal to enhance the stomach action already occurring. But as more acid chyme enters the duodenum the decreasing pH inhibits gastrin secretion and causes the release of negative or "stop" signals from the duodenum.
These take the form of chemicals called enterogastrones which include GIP (gastric inhibitory peptide). GIP inhibits stomach secretion and motility and allows time for the digestive process to proceed in the duodenum before it receives more chyme. The enterogastric reflex also reduces motility and forcefully closes the pyloric sphincter. Eventually as the chyme is removed, the pH increases and gastrin and the "go" signal resumes and the process occurs all over again. This series of "go" and "stop" signals continues until stomach emptying is complete.
Ketone Body
Biochemistry
During fasting or carbohydrate starvation, oxaloacetate is depleted in liver because it is used for gluconeogenesis. This impedes entry of acetyl-CoA into Krebs cycle. Acetyl-CoA then is converted in liver mitochondria to ketone bodies, acetoacetate and b-hydroxybutyrate.
Three enzymes are involved in synthesis of ketone bodies:
b-Ketothiolase. The final step of the b-oxidation pathway runs backwards, condensing 2 acetyl-CoA to produce acetoacetyl-CoA, with release of one CoA.
HMG-CoA Synthase catalyzes condensation of a third acetate moiety (from acetyl-CoA) with acetoacetyl-CoA to form hydroxymethylglutaryl-CoA (HMG-CoA).
HMG-CoA Lyase cleaves HMG-CoA to yield acetoacetate plus acetyl-CoA.
b-Hydroxybutyrate Dehydrogenase catalyzes inter-conversion of the ketone bodies acetoacetate and b-hydroxybutyrate.
Ketone bodies are transported in the blood to other tissue cells, where they are converted back to acetyl-CoA for catabolism in Krebs cycle
MAXILLARY SECOND BICUSPID
Dental Anatomy
MAXILLARY SECOND BICUSPID
smaller in dimensions. The cusps are not as sharp as the maxillary first bicuspid and have only one root.
Facial: This tooth closely resembles the maxillary first premolar but is a less defined copy of its companion to the mesial. The buccal cusp is shorter, less pointed, and more rounded than the first.
Lingual: Again, this tooth resembles the first. The lingual cusp, however, is more nearly as large as the buccal cusp.
Proximal: Mesial and distal surfaces are rounded. The mesial developmental depression and mesial marginal ridge are not present on the second premolar.
Occlusal: The crown outline is rounded, ovoid, and is less clearly defined than is the first.
Contact Points; When viewed from the facial, the distal contact area is located more cervically than is the mesial contact area.
Management of Skin Loss in the Face
Oral and Maxillofacial SurgeryManagement of Skin Loss in the Face
Skin loss in the face can be a challenging condition to manage, particularly
when it involves critical areas such as the lips and eyelids. The initial
assessment of skin loss may be misleading, as retraction of skin due to
underlying muscle tension can create the appearance of tissue loss. However,
when significant skin loss is present, it is essential to address the issue
promptly and effectively to prevent complications and promote optimal healing.
Principles of Management
Assessment Under Anesthesia: A thorough examination
under anesthesia is necessary to accurately assess the extent of skin loss
and plan the most suitable repair strategy.
No Healing by Granulation: Unlike other areas of the
body, wounds on the face should not be allowed to heal by granulation. This
approach can lead to unacceptable scarring, contracture, and functional
impairment.
Repair Options: The following options are available for
repairing skin loss in the face:
Skin Grafting: This involves transferring a piece
of skin from a donor site to the affected area. Skin grafting can be
used for small to moderate-sized defects.
Local Flaps: Local flaps involve transferring
tissue from an adjacent area to the defect site. This approach is useful
for larger defects and can provide better color and texture match.
Apposition of Skin to Mucosa: In some cases, it may
be possible to appose skin to mucosa, particularly in areas where the
skin and mucosa are closely approximated.
Types of skin grafts:
Split-thickness skin graft (STSG):The most common type, where only the epidermis
and a thin layer of dermis are harvested.
Full-thickness skin graft (FTSG):Includes the entire thickness of the skin,
typically used for smaller areas where cosmetic appearance is crucial.
Epidermal skin graft (ESG):Only the outermost layer of the epidermis is
harvested, often used for smaller wounds.
Considerations for Repair
Aesthetic Considerations: The face is a highly visible
area, and any repair should aim to restore optimal aesthetic appearance.
This may involve careful planning and execution of the repair to minimize
scarring and ensure a natural-looking outcome.
Functional Considerations: In addition to aesthetic
concerns, functional considerations are also crucial. The repair should aim
to restore normal function to the affected area, particularly in critical
areas such as the lips and eyelids.
Timing of Repair: The timing of repair is also
important. In general, early repair is preferred to minimize the risk of
complications and promote optimal healing.
Nance Appliance
OrthodonticsThe Nance Appliance is a fixed orthodontic device used
primarily in the upper arch to maintain space and prevent the molars from
drifting forward. It is particularly useful in cases where there is a need to
hold the position of the maxillary molars after the premature loss of primary
molars or to maintain space for the eruption of permanent teeth. Below is an
overview of the Nance Appliance, its components, functions, indications,
advantages, and limitations.
Components of the Nance Appliance
Baseplate:
The Nance Appliance features an acrylic baseplate that is
custom-made to fit the palate. This baseplate is typically made of a
pink acrylic material that is molded to the shape of the patient's
palate.
Anterior Button:
A prominent feature of the Nance Appliance is the anterior button,
which is positioned against the anterior teeth (usually the incisors).
This button helps to stabilize the appliance and provides a point of
contact to prevent the molars from moving forward.
Bands:
The appliance is anchored to the maxillary molars using bands that
are cemented onto the molars. These bands provide the necessary
anchorage for the appliance.
Wire Framework:
A wire framework may be incorporated into the appliance to enhance
its strength and stability. This framework typically consists of a
stainless steel wire that connects the bands and the anterior button.
Functions of the Nance Appliance
Space Maintenance:
The primary function of the Nance Appliance is to maintain space in
the upper arch, particularly after the loss of primary molars. It
prevents the adjacent teeth from drifting into the space, ensuring that
there is adequate room for the eruption of permanent teeth.
Molar Stabilization:
The appliance helps stabilize the maxillary molars in their proper
position, preventing them from moving forward or mesially during
orthodontic treatment.
Arch Development:
In some cases, the Nance Appliance can assist in arch development by
providing a stable base for other orthodontic appliances or treatments.
Indications for Use
Premature Loss of Primary Molars: To maintain space for
the eruption of permanent molars when primary molars are lost early.
Crowding: To prevent adjacent teeth from drifting into
the space created by lost teeth, which can lead to crowding.
Molar Stabilization: To stabilize the position of the
maxillary molars during orthodontic treatment.
Advantages of the Nance Appliance
Fixed Appliance: As a fixed appliance, the Nance
Appliance does not rely on patient compliance, ensuring consistent space
maintenance.
Effective Space Maintenance: It effectively prevents
unwanted tooth movement and maintains space for the eruption of permanent
teeth.
Minimal Discomfort: Generally, patients tolerate the
Nance Appliance well, and it does not cause significant discomfort.
Limitations of the Nance Appliance
Oral Hygiene: Maintaining oral hygiene can be more
challenging with fixed appliances, and patients must be diligent in their
oral care to prevent plaque accumulation and dental issues.
Limited Movement: The Nance Appliance primarily affects
the molars and may not be effective for moving anterior teeth.
Adjustment Needs: While the appliance is generally
stable, it may require periodic adjustments or monitoring by the
orthodontist.
CARIDEX and CARISOLV
PedodonticsCARIDEX and CARISOLV
CARIDEX and CARISOLV are both dental
products designed for the chemomechanical removal of carious dentin. Here’s a
detailed breakdown of their components and mechanisms:
CARIDEX
Components:
Solution I: Contains sodium hypochlorite (NaOCl)
and is used for its antimicrobial properties and ability to dissolve
organic tissue.
Solution II: Contains glycine and aminobutyric acid
(ABA). When mixed with sodium hypochlorite, it produces N-mono
chloro DL-2-amino butyric acid, which aids in the removal of
demineralized dentin.
Application:
CARIDEX is particularly useful for deep cavities, allowing for the
selective removal of carious dentin while preserving healthy tooth
structure.
CARISOLV
Components:
Syringe 1: Contains sodium hypochlorite at a
concentration of 0.5% w/v (which is equivalent to
0.51%).
Syringe 2: Contains a mixture of amino acids (such
as lysine, leucine, and glutamic acid) and erythrosine dye, which helps
in visualizing the removal of carious dentin.
pH Level:
The pH of the CARISOLV solution is approximately 11,
which helps in the dissolution of carious dentin.
Mechanism of Action:
The sodium hypochlorite in CARISOLV softens and dissolves carious
dentin, while the amino acids and dye provide a visual cue for the
clinician. The procedure can be stopped when discoloration is no longer
observed, indicating that all carious dentin has been removed.
Acute viral hepatitis
General Pathology
Acute viral hepatitis
Clinical features. Acute viral hepatitis may be icteric or anicteric. Symptoms include malaise, anorexia, fever, nausea, upper abdominal pain, and hepatomegaly, followed by jaundice, putty-colored stools, and dark urine.
In HBV, patients may have urticaria, arthralgias, arthritis, vasculitis, and glomerulonephritis (because of circulating immune complexes). Blood tests show elevated serum bilirubin (if icteric), elevated transaminases, and alkaline phosphatase.
The acute illness usually lasts 4-6 weeks.
Pathology
(1) Grossly, there is an enlarged liver with a tense capsule.
(2) Microscopically, there is ballooning degeneration of hepatocytes and liver cell necrosis.