NEET MDS Synopsis
The Nasopharynx
AnatomyThe Nasopharynx
The nasal part of the pharynx has a respiratory function.
It lies superior to the soft palate and is a posterior extension of the nasal cavity.
The nose opens into the nasopharynx via to large posterior apertures called choanae.
The roof and posterior wall of the nasopharynx form a continuous surface that lies inferior to the body of the sphenoid bone and the basilar part of the occipital bone.
In the mucous membrane of the roof of the posterior wall of the nasopharynx is a collection of lymphoid tissue, known as the pharyngeal tonsil (commonly known as the adenoids).
The pharyngeal orifice of the auditory tube is on the lateral wall of the nasopharynx, 1 to 1.5 cm posterior to the inferior concha, and level with the superior border of the palate.
The orifice is directed inferiorly and has a hood-like tubal elevation over it called the torus of the auditory tube or the torus tubarius (L. torus, swelling).
Extending inferiorly from the torus is a vertical fold of mucous membrane, known as the salpingopharyngeal fold.
The collection of lymphoid tissue in the submucosa of the pharynx, posterior to the orifice of the auditory tube, is known as the tubal tonsil.
Posterior to the torus and the salpingopharyngeal fold, there is a slit-like lateral projection of the pharynx called the pharyngeal recess.
It extends laterally and posteriorly.
COMPOSITE RESINS -Components
Dental Materials
COMPOSITE RESINS
Components
Filler particles-colloidal silica, crystalline silica (quartz), or silicates of various particle sizes (containing Li, AI, Zn, Yr)
Matrix-BIS-GMA (or UDMA) with lower molecular weight diluents (e.g., TEGDMA) that correct during polymerization
Coupling agent- silane that chemically bonds the surfaces of the filter particles to the polymer matrix
The Sublingual Glands
AnatomyThe Sublingual Glands
These are the smallest of the three paired salivary glands and the most deeply situated.
They are almond-shaped and lie in the floor of the mouth between the mandible and the genioglossus muscle.
The paired glands unite to form a horseshoe-shaped glandular mass around the lingual frenulum.
Numerous small ducts (10 to 12) open into the floor of the mouth.
Sometimes one of the ducts opens into the submandibular duct.
The nerves the accompany the submandibular and sublingual glands are derived from the lingual and chorda tympani nerves and from the sympathetic nerves.
The parasympathetic secretomotor fibres are from the submandibular ganglion.
LIPOPROTIENS
Biochemistry
LIPOPROTIENS
Lipoproteins Consist of a Nonpolar Core & a Single Surface Layer of Amphipathic Lipids
The nonpolar lipid core consists of mainly triacylglycerol and cholesteryl ester and is surrounded by a single surface layer of amphipathic phospholipid and cholesterol molecules .These are oriented so that their polar groups face outward to the aqueous medium. The protein moiety of a lipoprotein is known as an apolipoprotein or apoprotein,constituting nearly 70% of some HDL and as little as 1% of Chylomicons. Some apolipoproteins are integral and cannot be removed, whereas others can be freely transferred to other lipoproteins.
There re five types of lipoproteins, namely chylomicrons, very low density lipoproteins(VLDL) low density lipoproteins (LDL), high density Lipoproteins (HDL) and free fatty acid-albumin complexes.
Osteomyelitis of the Jaw (OML)
Oral and Maxillofacial SurgeryOsteomyelitis of the Jaw (OML)
Osteomyelitis of the jaw (OML) is a serious infection of the bone that can
lead to significant morbidity if not properly diagnosed and treated.
Understanding the etiology and microbiological profile of OML is crucial for
effective management. Here’s a detailed overview based on the information
provided.
Historical Perspective on Etiology
Traditional View: In the past, the etiology of OML was
primarily associated with skin surface bacteria, particularly Staphylococcus
aureus. Other bacteria, such as Staphylococcus epidermidis and
hemolytic streptococci, were also implicated.
Reevaluation: Recent findings indicate that S.
aureus is not the primary pathogen in cases of OML affecting
tooth-bearing bone. This shift in understanding highlights the complexity of
the microbial landscape in jaw infections.
Microbiological Profile
Common Pathogens:
Aerobic Streptococci:
α-Hemolytic Streptococci: Particularly Streptococcus
viridans, which are part of the normal oral flora and can
become pathogenic under certain conditions.
Anaerobic Streptococci: These bacteria thrive in
low-oxygen environments and are significant contributors to OML.
Other Anaerobes:
Peptostreptococcus: A genus of anaerobic
bacteria commonly found in the oral cavity.
Fusobacterium: Another group of anaerobic
bacteria that can be involved in polymicrobial infections.
Bacteroides: These bacteria are also part of
the normal flora but can cause infections when the balance is
disrupted.
Additional Organisms:
Gram-Negative Organisms:
Klebsiella, Pseudomonas, and Proteus species
may also be isolated in some cases, particularly in chronic or
complicated infections.
Specific Pathogens:
Mycobacterium tuberculosis: Can cause
osteomyelitis in the jaw, particularly in immunocompromised
individuals.
Treponema pallidum: The causative agent of
syphilis, which can lead to specific forms of osteomyelitis.
Actinomyces species: Known for causing
actinomycosis, these bacteria can also be involved in jaw
infections.
Polymicrobial Nature of OML
Polymicrobial Disease: Established acute OML is
typically a polymicrobial infection, meaning it involves multiple types of
bacteria. The common bacterial constituents include:
Streptococci (both aerobic and anaerobic)
Bacteroides
Peptostreptococci
Fusobacteria
Other opportunistic bacteria that may contribute to the infection.
Clinical Implications
Sinus Tract Cultures: Cultures obtained from sinus
tracts in the jaw may often be misleading. They can be contaminated with
skin flora, such as Staphylococcus species, which do not accurately
represent the pathogens responsible for the underlying osteomyelitis.
Diagnosis and Treatment: Understanding the
polymicrobial nature of OML is essential for effective diagnosis and
treatment. Empirical antibiotic therapy should consider the range of
potential pathogens, and cultures should be interpreted with caution.
Thalassemia
Pathology
Thalassemias are a heterogeneous group of hereditary blood disorders characterized by faulty globin chain synthesis resulting in defective hemoglobin, which can lead to anemia
Thalassemia provides partial resistance against malaria.
Beta thalassemia
- most commonly seen in people of Mediterranean descent
Etiology
usually due to point mutations in promoter sequences or splicing sites
β-globin locus - short arm of chromosome 11
In a normal cell, the β-globin chains are coded by a total of two alleles . Thus, there are two forms of the disease.
Beta thalassemia minor (trait): one defective allele
Beta thalassemia major (Cooley's anemia): two defective alleles
Pathophysiology
Inefficient erythropoiesis → anemia
Beta thalassemia minor and major: faulty β-globin chain synthesis → ↓ β-chains→ ↑ γ-,δ-chains → ↑ HbF and ↑ HbA2
Alpha thalassemia
most commonly seen in people of Asian and African descent
Etiology
usually due to deletion of at least one out of the four existing alleles
Inheritance pattern: autosomal recessive
In a normal cell, the α-globin chains are coded by a total of four alleles.
Thus, there are four forms of the disease. The severity of alpha thalassemia depends on the number of defective α-globin alleles.
- Silent carrier (minima form): one defective allele (-α/αα)
- Alpha thalassemia trait (minor form) -Two defective alleles ,Cis-deletion is common amongst Asian populations, whereas trans-deletions are more common in African populations
- Hemoglobin H disease: three defective alleles
- Hemoglobin Bart disease (major form): four defective alleles
Pathophysiology
Alpha thalassemia major (HbH disease) and Bart disease: faulty α-globin chain synthesis → ↓ α-chains → ↑ β-, γ-chains → ↑ HbH, ↑ Hb-Bart's
Antiplatelet Drugs
Pharmacology
Antiplatelet Drugs:
Whereas the anticoagulant drugs such as Warfarin and Heparin suppress the synthesis or activity of the clotting factors and are used to control venous thromboembolic disorders, the antithrombotic drugs suppress platelet function and are used primarily for arterial thrombotic disease. Platelet plugs form the bulk of arterial thrombi.
Acetylsalicylic acid (Aspirin)
• Inhibits release of ADP by platelets and their aggregation by acetylating the enzymes (cyclooxygenases or COX) of the platelet that synthesize the precursors of Thromboxane A2 that is a labile inducer of platelet aggregation and a potent vasoconstrictor.
• Low dose (160-320 mg) may be more effective in inhibiting Thromboxane A2 than PGI2 which has the opposite effect and is synthesized by the endothelium.
• The effect of aspirin is irreversible.
Balanced Anesthesia
Pharmacology
Balanced Anesthesia
A barbiturate, narcotic analgesic agent, neuromuscular blocking agent, nitrous oxide and one of the more potent inhalation anesthetic.