NEET MDS Synopsis
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.
Immunofluorescence
General MicrobiologyImmunofluorescence
This is precipitation or complement fixation tests. The technique can detect proteins at concentrations of around 1 µg protein per ml body fluid. Major disadvantage with this technique is frequent occurrence of nonspecific fluorescence in the tissues and other material.
The fluorescent dyes commonly used are fluorescein isothocyanate (FITC). These dyes exhibit fluorescence by absorbing UV light between 290 and 495 nm and emitting longer wavelength coloured light of 525 nm which gives shining appearance (fluorescence) to protein labelled with dye. Blue green (apple green) fluorescence is seen with FITC and orange red with rhodamine.
Enzyme Immunoassays
These are commonly called as enzyme linked immunosorbent assays or EL1SA. It is a simple and versatile technique which is as sensitive as radioimmunoassays. It is now the
technique for the detection of antigens, antibodies, hormones, toxins and viruses.
Identification of organisms by immunofluorescence
Type of agent Examples
Bacterial Neisseria gonorrhoeae, H. influenzae ,Strept pyogenes, Treponema pallidum
Viral Herpesvirus, Rabiesvirus, Epstein-Barr virus
Mycotic Candida albicans
Enzymatic activity results in a colour change which can be assessed visibly or quantified in a simple spectrophotometer.
Esophagus pathology
General Pathology
ESOPHAGUS Pathology
Congenital malformations
1. A tracheoesophageal fistula (the most prevalent esophageal anomaly) occurs most commonly as an upper esophageal blind pouch with a fistula between the lower segment of the esophagus and the trachea. It is associated with hydramnios, congenital heart disease, and other gastrointestinal malformation.
2. Esophageal atresia is associated with VATER syndrome (vertebra1 defects, anal atresia, tracheoesophageal fistula, and renal dysplasia)
3. Stenosis refers to a narrowed esophagus with a small lumen. lt may be congenital or acquired, e.g., through trauma or inflammation.
Inflammatory disorders
Esophagitis
most often involves the lower half of the esophagus. Caused by the reflux of gastric contents (juices) into the lower esophagus. One of the most common GI disorders.
Clinical features.
Patients experience substernal burning associated with regurgitation, mild anemia, dysphagia, hematemesis, and melena. Esophagitis may predispose to esophageal cancer.
Etiology
- Reflux esophagitis is due to an incompetent lower esophageal sphincter that permits reflux of gastric juice into the lower esophagus.
- Irritants such as citric acid, hot liquids, alcohol, smoking, corrosive chemicals, and certain drugs, such as tetracycline, may provoke inflammation.
- Infectious etiologies include herpes, CMV, and C. albicans. The immunocompromised host is particularly susceptible to infectious esophagitis.
Although chronic or severe reflux disease is uncommon, consequences of these conditions can lead to Barrett’s esophagus, development of a stricture, or hemorrhage.
Pathology
-Grossly, there is hyperemia, edema, inflammation, and superficial necrosis.
Complications include ulceration, bleeding, stenosis, and squamous carcinoma.
Treatment: diet control, antacids, and medications that decrease the production of gastric acid (e.g., H blockers).
Barrett's esophagus,
gastric or intestinal columnar epithelium replaces normal squamous epithelium in response to chronic reflux.- A complication of chronic gastroesophageal reflux disease.
- Histologic findings include the replacement of squamous epithelium with metaplastic columnar epithelium.
- Complications include increased incidence of esophageal adenocarcinoma, stricture formation, or hemorrhage (ulceration).
Motor disorders.
Normal motor function requires effective peristalsis and relaxation of the lower esophageal sphincter.
Achalasia is a lack of relaxation of the lower esophageal sphincter (LES), which may be associated with aperistalsis of the esophagus and increased basal tone of the LES.
Clinical features. Achalasia occurs most commonly between the ages of 30 and 50. Typical symptoms are dysphagia, regurgitation, aspiration, and chest pain. The lack of motility promotes stagnation and predisposes to carcinoma.
Hiatal hernia is the herniation of the abdominal esophagus, the stomach, or both, through the esophageal hiatus in the diaphragm.
Scleroderma is a collagen vascular disease, seen primarily in women, that causes subcutaneous fibrosis and widespread degenerative changes. (A mild variant is known as CREST syndrome which stands for calcinosis. raynaud's phenomenon , esophageal dysfunction, sclerodactyly and telengectseia. esophagus is the most frequently involved region of the gastrointestinal tract.
Clinical features are mainly dysphagia and heartburn due to reflux oesophagitis caused by aperlistalsis and incompetent LES.
Rings and webs
1. Webs are mucosal folds in the upper esophagus above the aortic arch.
2. Schatzki rings are mucosal rings at the squamocolumnarjunction below the aortic arch.
3. Plummer Vinson Syndrome consist of triad of dysphagia, atrophic glossitis, and anemia. Webs are found in the upper esophagus. The syndrome is associated specifically with iron deficiency anemia and sometimes hypochlorhydria. Patients are at increased risk for carcinoma of the pharynx or esophagus.
Mallory-Weiss syndrome
Mallory-Weiss tears refers to small mucosal tears at the gastroesophageal junction secondary to recurrent forceful vomiting. The tears occur along the long axis an result in hematemesis (sometimes massive).
- Characterized by lacerations (tears) in the esophagus.
- Most commonly occurs from vomiting (alcoholics).
- A related condition, known as Boerhaave syndrome, occurs when the esophagus ruptures, causing massive upper GI hemorrhage.
Esophageal varices
- The formation of varices (collateral channels) occurs from portal hypertension.
Causes of portal hypertension include blockage of the portal vein or liver disease (cirrhosis).
- Rupture of esophageal varices results in massive hemorrhage into the esophagus and hematemesis.
- Common in patients with liver cirrhosis.
Diverticula
are sac-like protrusions of one or more layers of pharyngeal or esophageal wall.
Tumors
- Benign tumors are rare.
- Carcinoma of the esophagus most commonly occurs after 50 and has a male:female ratio of 4.1.
Etiology: alcohal ingestion, smoking, nitrosamines in food, achalasia , web ring, Barrettes esophagus, and deficiencies of vitamins A and C , riboflavin, and some trace minerals
Clinical features include dysphagia (first to solids), retrosternal pain, anorexia, weight loss, melena, and symptoms secondary to metastases.
Pathology
- 50% occur in the middle third of the esophagus, 30% in the lower third, and 20% in the upper third. Most esophageal cancers are squamous cell carcinomas.
Adenocarcinomas arise mostly out of Barrett's esophagus.
Prognosis
is poor. Fewer than 10% of patients survive 5 years, usually because diagnosis is made at a late stage. The most common sites of metastasis are the liver and lung. The combination of cigarette smoking and alcohol is particularly causative for esophageal cancer (over l00% risk compared to nondrinkers/nonsmokers).
STRUCTURE AND SOME PROPERTIES OF IG CLASSES AND SUBCLASSES
General Microbiology
STRUCTURE AND SOME PROPERTIES OF IG CLASSES AND SUBCLASSES
A. IgG
1. Structure
All IgG’s are monomers (7S immunoglobulin). The subclasses differ in the number of disulfide bonds and length of the hinge region.
2. Properties
IgG is the most versatile immunoglobulin because it is capable of carrying out all of the functions of immunoglobulin molecules.
a) IgG is the major Ig in serum – 75% of serum Ig is IgG
b) IgG is the major Ig in extra vascular spaces
c) Placental transfer – IgG is the only class of Ig that crosses the placenta. Transfer is mediated by a receptor on placental cells for the Fc region of IgG. Not all subclasses cross equally well; IgG2 does not cross well.
d) Fixes complement – Not all subclasses fix equally well; IgG4 does not fix complement
e) Binding to cells – Macrophages, monocytes and neutrophils and some lymphocytes have Fc receptors for the Fc region of IgG. A consequence of binding to the Fc receptors on such cells is that the cells can now internalize the antigen better. The antibody prepares the antigen for killing by the phagocytic cells. The term opsonin is used to describe substances that enhance phagocytosis. (Coating of the surface of pathogen by antibody is called opsonization).IgG is a good opsonin. Binding of IgG to Fc receptors on other types of cells results in the activation of other functions.
IgM
1. Structure
IgM normally exists as a pentamer (19S immunoglobulin) but it can also exist as a monomer. In the pentameric form all heavy chains are identical and all light chains are identical. Thus, the valence is theoretically 10. IgM has an extra domain on the mu chain (CH4) and it has another protein covalently bound via a S-S bond called the J chain. This chain functions in polymerization of the molecule into a pentamer.
2. Properties
a) IgM is the third most common serum Ig.
b) IgM is the first Ig to be made by the fetus and the first Ig to be made by a virgin B cells when it is stimulated by antigen.
c) As a consequence of its pentameric structure, IgM is a good complement fixing Ig. Thus, IgM antibodies are very efficient in leading to the lysis of microorganisms.
d) As a consequence of its structure, IgM is also a good agglutinating Ig . Thus, IgM antibodies are very good in clumping microorganisms for eventual elimination from the body.
e) IgM binds to some cells via Fc receptors.
f) B cell surface Ig
Surface IgM exists as a monomer and lacks J chain but it has an extra 20 amino acids at the C-terminus to anchor it into the membrane . Cell surface IgM functions as a receptor for antigen on B cells.
IgA
1. Structure
Serum IgA is a monomer but IgA found in secretions is a dimer as presented in Figure 10. When IgA exits as a dimer, a J chain is associated with it.
When IgA is found in secretions is also has another protein associated with it called the secretory piece or T piece; sIgA is sometimes referred to as 11S immunoglobulin. Unlike the remainder of the IgA which is made in the plasma cell, the secretory piece is made in epithelial cells and is added to the IgA as it passes into the secretions . The secretory piece helps IgA to be transported across mucosa and also protects it from degradation in the secretions.
2. Properties
a) IgA is the 2nd most common serum Ig.
b) IgA is the major class of Ig in secretions – tears, saliva, colostrum, mucus. Since it is found in secretions secretory IgA is important in local (mucosal) immunity.
c) Normally IgA does not fix complement, unless aggregated.
d) IgA can binding to some cells – PMN’s and some lymphocytes.
IgD
1. Structure
IgD exists only as a monomer.
2. Properties
a) IgD is found in low levels in serum; its role in serum is uncertain.
b) IgD is primarily found on B cell surfaces where it functions as a receptor for antigen.
c) IgD does not bind complement.
E. IgE
1. Structure
IgE exists as a monomer and has an extra domain in the constant region.
2. Properties
a) IgE is the least common serum Ig since it binds very tightly to Fc receptors on basophils and mast cells even before interacting with antigen.
b) Involved in allergic reactions – As a consequence of its binding to basophils and mast cells, IgE is involved in allergic reactions. Binding of the allergen to the IgE on the cells results in the release of various pharmacological mediators that result in allergic symptoms.
c) IgE also plays a role in parasitic helminth diseases. Since serum IgE levels rise in parasitic diseases, measuring IgE levels is helpful in diagnosing parasitic infections. Eosinophils have Fc receptors for IgE and binding of eosinophils to IgE-coated helminths results in killing of the parasite.
d) IgE does not fix complement.
Stationary Relationship
Dental Anatomy
Stationary Relationship
a) .Centric Relation is the most superior relationship of the condyle of the mandible to the articular fossa of the temporal bone as determined by the bones ligaments. and muscles of the temporomandibular joint; in an ideal dentition it is the same as centric occlusion.
(b) Canines may also be used to confirm the molar relationships to classify occlusion when molars are missing; a class I canine relationship shows the cusp tip of the maxillary canine facial to the mesiobuccal cusp of the first permanent molar
c) Second primary molars are used to classify the occlusion in a primary dentition
(d) In a mixed dentition the first permanent molars will erupt into a normal occlusion if there is a terminal step between the distal surfaces of maxillarv and mandibular second primary molars; if these surfaces are flush, a terminal plane exists and the first permanent molars will first erupt into an end-to-end relationship until there is a shifting of space or exfoliation of the second primary molar
MANDIBULAR CUSPIDS
Dental Anatomy
MANDIBULAR CUSPIDS
Mandibular canines are those lower teeth that articulate with the mesial aspect of the upper canine.
Facial: The mandibular canine is noticeably narrower mesidistally than the upper, but the root may be as long as that of the upper canine. In an individual person,the lower canine is often shorter than that of the upper canine. The mandibular canine is wider mesiodistally than either lower incisor. A distinctive feature is the nearly straight outline of the mesial aspect of the crown and root. When the tooth is unworn, the mesial cusp ridge appears as a sort of 'shoulder' on the tooth. The mesial cusp ridge is much shorter than the distal cusp ridge.
Lingual: The marginal ridges and cingulum are less prominent than those of the maxillary canine. The lingual surface is smooth and regular. The lingual ridge, if present, is usually rather subtle in its expression.
Proximal: The mesial and distal aspects present a triangular outline. The cingulum as noted is less well developed. When the crown and root are viewed from the proximal, this tooth uniquely presents a crescent-like profile similar to a cashew nut.
Incisal: The mesiodistal dimension is clearly less than the labiolingual dimension. The mesial and distal 'halves' of the tooth are more identical than the upper canine from this perspective. In the mandibular canine, the unworn incisal edge is on the line through the long axis of this tooth.
Surgical Approaches in Oral and Maxillofacial Surgery
Oral and Maxillofacial SurgerySurgical Approaches in Oral and Maxillofacial Surgery
In the management of tumors and lesions in the oral and maxillofacial region,
various surgical approaches are employed based on the extent of the disease, the
involvement of surrounding structures, and the need for reconstruction. Below is
a detailed overview of the surgical techniques mentioned, along with their
indications and reconstruction options.
1. Marginal / Segmental / En Bloc Resection
Definition:
En Bloc Resection: This technique involves the complete
removal of a tumor along with a margin of healthy tissue, without disrupting
the continuity of the bone. It is often used for tumors that are
well-defined and localized.
Indications:
No Cortical Perforation: En bloc segmental resection is
indicated when there is no evidence of cortical bone perforation. This
allows for the removal of the tumor while preserving the structural
integrity of the surrounding bone.
Tumor Characteristics: This approach is suitable for
benign tumors or low-grade malignancies that have not invaded surrounding
tissues.
2. Partial Resection (Mandibulectomy)
Definition:
Mandibulectomy: This procedure involves the resection
of a portion of the mandible, typically performed when a tumor is present.
Indications:
Cortical Perforation: Mandibulectomy is indicated when
there is cortical perforation of the mandible. This means that the tumor has
invaded the cortical bone, necessitating a more extensive surgical approach.
Clearance Margin: A margin of at least 1 cm of
healthy bone is typically removed to ensure complete excision of the tumor
and reduce the risk of recurrence.
3. Total Resection (Hemimandibulectomy)
Definition:
Hemimandibulectomy: This procedure involves the
resection of one half of the mandible, including the associated soft
tissues.
Indications:
Perforation of Bone and Soft Tissue: Hemimandibulectomy
is indicated when there is both perforation of the bone and involvement of
the surrounding soft tissues. This is often seen in more aggressive tumors
or those that have metastasized.
Extensive Tumor Involvement: This approach is necessary
for tumors that cannot be adequately removed with less invasive techniques
due to their size or location.
4. Reconstruction
Following resection, reconstruction of the jaw is often necessary to restore
function and aesthetics. Several options are available for reconstruction:
a. Reconstruction Plate:
Description: A reconstruction plate is a rigid plate
made of titanium or other biocompatible materials that is used to stabilize
the bone after resection.
Indications: Used in cases where structural support is
needed to maintain the shape and function of the mandible.
b. K-wire:
Description: K-wires are thin, flexible wires used to
stabilize bone fragments during the healing process.
Indications: Often used in conjunction with other
reconstruction methods to provide additional support.
c. Titanium Mesh:
Description: Titanium mesh is a flexible mesh that can
be shaped to fit the contours of the jaw and provide support for soft tissue
and bone.
Indications: Used in cases where there is significant
bone loss and soft tissue coverage is required.
d. Rib Graft / Iliac Crest Graft:
Description: Autogenous bone grafts can be harvested
from the rib or iliac crest to reconstruct the mandible.
Indications: These grafts are used when significant
bone volume is needed for reconstruction, providing a biological scaffold
for new bone formation.
Calcium Channel Blocking Agents- Antianginal Drugs
Pharmacology
Calcium Channel Blocking Agents
• Act on contractile and conductive tissues of the heart and on vascular smooth muscles
• Prevent movement of extracellular calcium into the cell
– Coronary and peripheral arteries dilate
– Myocardial contractility decreases
– Depress conduction system
Therapeutic Actions
• Inhibit movement of calcium ions across the membranes of myocardial and arterial muscle cells. Altering the action potential and blocking muscle cell contraction
• Depress myocardial contractility
• Slow cardiac impulse formation in the conductive tissues
• Cause a fall in BP