NEET MDS Synopsis
Cell, or Plasma, membrane
PhysiologyCell, or Plasma, membrane
Structure - 2 primary building blocks include
protein (about 60% of the membrane) and lipid, or
fat (about 40% of the membrane).
The primary lipid is called phospholipids, and molecules of phospholipid form a 'phospholipid bilayer' (two layers of phospholipid molecules). This bilayer forms because the two 'ends' of phospholipid molecules have very different characteristics: one end is polar (or hydrophilic) and one (the hydrocarbon tails below) is non-polar (or hydrophobic):
Functions include:
supporting and retaining the cytoplasm
being a selective barrier .
transport
communication (via receptors)
Seborrheic dermatitis
General Pathology
Seborrheic dermatitis is a scaly dermatitis on the scalp (dandruff) and face.
- due to Pitysporium species
- can be seen in AIDS as an opportunistic infection
Water Acid Bases & Buffers
Biochemistry
Keq, Kw and pH
As H2O is the medium of biological systems one must consider the role of this molecule in the dissociation of ions from biological molecules. Water is essentially a neutral molecule but will ionize to a small degree. This can be described by a simple equilibrium equation:
H2O <-------> H+ + OH-
This equilibrium can be calculated as for any reaction:
Keq = [H+][OH-]/[H2O]
Since the concentration of H2O is very high (55.5M) relative to that of the [H+] and [OH-], consideration of it is generally removed from the equation by multiplying both sides by 55.5 yielding a new term, Kw:
Kw = [H+][OH-]
This term is referred to as the ion product. In pure water, to which no acids or bases have been added:
Kw = 1 x 10-14 M2
As Kw is constant, if one considers the case of pure water to which no acids or bases have been added:
[H+] = [OH-] = 1 x 10-7 M
This term can be reduced to reflect the hydrogen ion concentration of any solution. This is termed the pH, where:
pH = -log[H+]
Periodontal Bone Grafts
PeriodontologyPeriodontal Bone Grafts
Bone grafting is a critical procedure in periodontal surgery, aimed at
restoring lost bone and supporting the regeneration of periodontal tissues.
1. Bone Blend
Bone blend is a mixture of cortical or cancellous bone that is procured using a trephine or rongeurs, placed in an
amalgam capsule, and triturated to achieve a slushy osseous mass. This technique
allows for the creation of smaller particle sizes, which enhances resorption and
replacement with host bone.
Particle Size: The ideal particle size for bone blend is
approximately 210 x 105 micrometers.
Rationale: Smaller particle sizes improve the chances of
resorption and integration with the host bone, making the graft more effective.
2. Types of Periodontal Bone Grafts
A. Autogenous Grafts
Autogenous grafts are harvested from the patient’s own body, providing the
best compatibility and healing potential.
Cortical Bone Chips
History: First used by Nabers and O'Leary in 1965.
Characteristics: Composed of shavings of cortical
bone removed during osteoplasty and ostectomy from intraoral sites.
Challenges: Larger particle sizes can complicate
placement and handling, and there is a potential for sequestration. This
method has largely been replaced by autogenous osseous coagulum and bone
blend.
Osseous Coagulum and Bone Blend
Technique: Intraoral bone is obtained using high-
or low-speed round burs and mixed with blood to form an osseous coagulum
(Robinson, 1969).
Advantages: Overcomes disadvantages of cortical
bone chips, such as inability to aspirate during collection and
variability in quality and quantity of collected bone.
Applications: Used in various periodontal
procedures to enhance healing and regeneration.
Intraoral Cancellous Bone and Marrow
Sources: Healing bony wounds, extraction sockets,
edentulous ridges, mandibular retromolar areas, and maxillary
tuberosity.
Applications: Provides a rich source of osteogenic
cells and growth factors for bone regeneration.
Extraoral Cancellous Bone and Marrow
Sources: Obtained from the anterior or posterior
iliac crest.
Advantages: Generally offers the greatest potential
for new bone growth due to the abundance of cancellous bone and marrow.
B. Bone Allografts
Bone allografts are harvested from donors and can be classified into three
main types:
Undermineralized Freeze-Dried Bone Allograft (FDBA)
Introduction: Introduced in 1976 by Mellonig et al.
Process: Freeze drying removes approximately 95% of
the water from bone, preserving morphology, solubility, and chemical
integrity while reducing antigenicity.
Efficacy: FDBA combined with autogenous bone is
more effective than FDBA alone, particularly in treating furcation
involvements.
Demineralized (Decalcified) FDBA
Mechanism: Demineralization enhances osteogenic
potential by exposing bone morphogenetic proteins (BMPs) in the bone
matrix.
Osteoinduction vs. Osteoconduction: Demineralized
grafts induce new bone formation (osteoinduction), while
undermineralized allografts facilitate bone growth by providing a
scaffold (osteoconduction).
Frozen Iliac Cancellous Bone and Marrow
Usage: Used sparingly due to variability in
outcomes and potential complications.
Comparison of Allografts and Alloplasts
Clinical Outcomes: Both FDBA and DFDBA have been
compared to porous particulate hydroxyapatite, showing little difference in
post-treatment clinical parameters.
Histological Healing: Grafts of DFDBA typically heal
with regeneration of the periodontium, while synthetic bone grafts (alloplasts)
heal by repair, which may not restore the original periodontal architecture.
THE PITUITARY GLAND
General Pathology
THE PITUITARY GLAND
This is a small, bean-shaped structure that lies at the base of the brain within the confines of the sella turcica. It is connected to the hypothalamus by a "stalk," composed of axons extending from the hypothalamus. The pituitary is composed of two morphologically and functionally distinct components: the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The adenohypophysis, in H&E stained sections, shows a colorful collection of cells with basophilic, eosinophilic or poorly staining ("chromophobic") cytoplasm.
FAT-SOLUBLE VITAMINS
Biochemistry
FAT-SOLUBLE VITAMINS
The fat-soluble vitamins, A, D, E, and K, are stored in the body for long periods of time and generally pose a greater risk for toxicity when consumed in excess than water-soluble vitamins.
VITAMIN A: RETINOL
Vitamin A, also called retinol, has many functions in the body. In addition to helping the eyes adjust to light changes, vitamin A plays an important role in bone growth, tooth development, reproduction, cell division, gene expression, and regulation of the immune system.
The skin, eyes, and mucous membranes of the mouth, nose, throat and lungs depend on vitamin A to remain moist. Vitamin A is also an important antioxidant that may play a role in the prevention of certain cancers.
One RAE equals 1 mcg of retinol or 12 mcg of beta-carotene. The Recommended Dietary Allowance (RDA) for vitamin A is 900 mcg/ day for adult males and 700 mcg/ day for adult females.
Vitamin A Deficiency
Vitamin A deficiency is rare, but the disease that results is known as xerophthalmia.
Other signs of possible vitamin A deficiency include decreased resistance to infections, faulty tooth development, and slower bone growth.
Vitamin A toxicity The Tolerable Upper Intake Level (UL) for adults is 3,000 mcg RAE.
VITAMIN D
Vitamin D plays a critical role in the body’s use of calcium and phosphorous. It works by increasing the amount of calcium absorbed from the small intestine, helping to form and maintain bones.
Vitamin D benefits the body by playing a role in immunity and controlling cell growth. Children especially need adequate amounts of vitamin D to develop strong bones and healthy teeth.
RDA From 12 months to age fifty, the RDA is set at 15 mcg.
20 mcg of cholecalciferol equals 800 International Units (IU), which is the recommendation for maintenance of healthy bone for adults over fifty.
Vitamin D Deficiency
Symptoms of vitamin D deficiency in growing children include rickets (long, soft bowed legs) and flattening of the back of the skull. Vitamin D deficiency in adults may result in osteomalacia (muscle and bone weakness), and osteoporosis (loss of bone mass).
Vitamin D toxicity
The Tolerable Upper Intake Level (UL) for vitamin D is set at 100 mcg for people 9 years of age and older. High doses of vitamin D supplements coupled with large amounts of fortified foods may cause accumulations in the liver and produce signs of poisoning.
VITAMIN E: TOCOPHEROL
Vitamin E benefits the body by acting as an antioxidant, and protecting vitamins A and C, red blood cells, and essential fatty acids from destruction.
RDA One milligram of alpha-tocopherol equals to 1.5 International Units (IU). RDA guidelines state that males and females over the age of 14 should receive 15 mcg of alpha-tocopherol per day.
Vitamin E Deficiency Vitamin E deficiency is rare. Cases of vitamin E deficiency usually only occur in premature infants and in those unable to absorb fats.
VITAMIN K
Vitamin K is naturally produced by the bacteria in the intestines, and plays an essential role in normal blood clotting, promoting bone health, and helping to produce proteins for blood, bones, and kidneys.
RDA
Males and females age 14 - 18: 75 mcg/day; Males and females age 19 and older: 90 mcg/day
Vitamin K Deficiency
Hemorrhage can occur due to sufficient amounts of vitamin K.
Vitamin K deficiency may appear in infants or in people who take anticoagulants, such as Coumadin (warfarin), or antibiotic drugs.
Newborn babies lack the intestinal bacteria to produce vitamin K and need a supplement for the first week.
Rheumatoid Arthritis
Orthopaedics
- The hallmark feature of rheumatoid arthritis is persistent symmetric polyarthritis (synovitis) of hands and feet.
- The spontaneous onset of excruciating pain, edema, and inflammation in the metatarsalphalangeal joint of the great toe (podagra) is highly suggestive of acute crystal-induced arthritis.
- Podagra is the initial joint manifestation in 50% of gout cases and is eventually involved in 90%.
- RA is a chronic autoimmune multisystem disease having inflammatory arthritis and systemic manifestation.
Pathogenesis –
1. Women (30 to 50 years) are more commonly affected
2. HLA-DR 4 Q is a risk factor for RA.
3. Initial site of disease is synovial membrane
Initiation phase – It is due to non – specific inflammation
Amplification phase – Due to T cell activation
Chronic inflammatory phase – Due to cytokines IL – 1, TNF- alpha (AIPG 2009) and IL – 6
Diagnostic criteria
Four of seven criteria are required
1. Morning stiffness – lasting 1 hour before maximal improvement
2. Arthritis of 3 or more joint areas – 14 possible joint areas are right or left PIP MCP, wrist, elbow, knee, ankle and MTP joints
3. Arthritis of hand joints.
4. Symmetrical arthritis.
5. Rheumatoid nodules.
6. Positive Serum rheumatoid factor
7. Radiographic changes – including erosions or unequivocal bong decalcification localized in or most marked adjacent to the involved joint.
Tooth Polishing and Cleansing Agents
Dental Materials
Tooth Polishing and Cleansing Agents
1. Cleansing-removal of exogenous stains, pellicle, materia alba, and other oral debris without causing undue abrasion to tooth structure
2. Polishing-smoothening surfaces of amalgam, composite, glass ionomers, porcelain, and other restorative materials
Factors influencing cleaning and polishing
- Hardness of abrasive particles versus substrate
- Particle size of abrasive particles
- Pressure applied during procedure
- Temperature of abrasive materials
Structure
Composition
-contain abrasives, such as kaolinite, silicon dioxide, calcined magnesium silicate, diatomaceous silicon dioxide, pumice. Sodium-potassium
-aluminum silicate, or zirconium silicate; some pastes also may contain sodium fluoride or stannous fluoride, but they have never been shown to produce positive effects
Reactions-abrasion for cleansing and polishing
Properties - Mechanical
- Products with pumice and quartz produce more efficient cleansing but also generate greater abrasion of enamel and dentin
-Coarse pumice is the most abrasive
-The abrasion rate of dentin is 5 to 6 times faster than the abrasion rate of enamel, regardless of the product
-Polymeric restorative materials, such as denture bases, denture teeth, composites, PMMA veneers, and composite veneers, can be easily scratched during polishing
-Do not polish cast porcelain restorations (e.g., Dicor) that are externally characterized or the color will be lost