Notes, summaries, assignments, exams, and problems for Biology

Xerophyte Adaptations

(Plants adapted to dry/arid environments – e.g., cactus, Opuntia)

1. Structural Adaptations

• Thick cuticle to reduce water loss.
• Sunken stomata to trap moisture and reduce transpiration.
• Reduced leaves (spines) to minimize water loss.
• Thick stems that store water (succulent stems).
• Deep or widespread roots to access water from deeper soil layers.

2. Physiological Adaptations

• CAM photosynthesis (in some) to open stomata at night.
• High osmotic pressure to absorb water quickly.
• Fewer stomata in number or present only on the lower surface.

Hydrophyte Adaptations

(Plants adapted to aquatic environments – e.g., lotus, water hyacinth)

1. Structural Adaptations

• Thin cuticle or absent cuticle as water is abundant.
• Large air spaces (aerenchyma)

1. Brain Abscess

• Gross Morphology

  Localized area of liquefactive necrosis filled with yellow pus, surrounded by a thin fibrous capsule and edematous, inflamed brain tissue.

• Pathology

  Caused by hematogenous spread of bacterial infection, direct trauma, or contiguous spread (e.g., from sinuses). Represents focal suppurative inflammation of the brain.

2. Neurinoma (Schwannoma)

• Gross Morphology

  Well-circumscribed, encapsulated globoid mass with a soft, tan “fish-flesh” appearance, often with cysts or hemorrhage. Cut surface may show yellow patches.

• Pathology

  A benign tumor of Schwann cells, often seen in cranial nerves (especially CN VIII) and associated with neurofibromatosis type 2. Grows slowly and may compress adjacent structures.

3. Fibrinous

Maxillary Radiolucent Landmarks

• Intermaxillary Suture (Incisor Region)

  Appears radiolucent (RL) with a radiopaque (RO) border. Often misinterpreted as a fracture; however, true fractures are irregular and lack a radiopaque border. Located at the midline between the two premaxillae.

• Nasal Fossa (Incisor & Canine Region)

  A pear-shaped radiolucency. Visible in the canine, incisor, and posterior regions.

• Incisive Foramen (Incisor Region)

  A radiolucency located at the midline of the palate, behind the central incisors. Differential Diagnosis: Consider an incisive canal cyst if its size exceeds 1 cm.

• Lateral Fossa (Canine Region)

  A depression appearing as a radiolucency near the canine and lateral incisor.

• Nasolacrimal Canal

  Appears radiolucent, located

Response to Orthodontic Pressure

Light Pressure (<1 second to Hours)

• Less than 1 second: PDL fluid is incompressible; alveolar bone bends, and a piezoelectric signal is generated.
• 1-2 seconds: PDL fluid is expressed; the tooth moves within the PDL space.
• 3-5 seconds: Blood flow within the PDL is partially compressed on the pressure side and dilated on the tension side.
• Minutes: Blood flow is altered, and oxygen tension begins to change.
• Hours: Metabolic changes and chemical messengers affect cellular activity.
• Less than 4 hours: Cellular differentiation begins within the PDL.
• 2 days: Tooth movement occurs as osteoclasts and osteoblasts remodel bone.

Heavy Pressure (<1 second to 7-14 days)

• Less than 1 second: PDL fluid is incompressible; alveolar

Aggressive Periodontitis: Localized vs. Generalized

This section outlines the key similarities and differences between Localized Aggressive Periodontitis (LAP) and Generalized Aggressive Periodontitis (GAP).

Localized Aggressive Periodontitis (LAP)

• Circumpubertal onset.
• Robust serum antibody response to infecting agents.
• Localized first molar/incisor presentation with interproximal attachment loss on at least two permanent teeth, one of which is a first molar.
• Lack of clinical inflammation.
• Presence of deep periodontal pockets.
• Amount of plaque inconsistent with the amount of periodontal destruction.
• Plaque forms a thin biofilm, rarely mineralizing into calculus.
• Distolabial migration and diastema formation.
• Increasing mobility of first molars.
• Sensitivity

First Line of Defense:

• 1) Mechanical Barriers & Surface Secretions:
  • A) Skin
  • B) Mucus Membrane:
    • 1) Sticky Mucus Membrane
    • Cilia
    • Mechanical Cleansing Action: Saliva, Tears, Urine
    • Low pH Stomach
    • Tears & Saliva: Lysozyme
    • Peristalsis in GIT
• 2) Normal Bacterial Flora
• 3) Naturally Occurring Antimicrobial Substances:
  • A) Type I Interferon: Antiviral Effect
  • B) Lysozyme: Lysis of Bacteria
  • C) Complement System: Responsible for Lysing Microorganisms
• 4) Body Hormones
• 5) Genetic Predisposition
• 6) Body Temperature: Pyrexia
• 7) Oxygen Tension
• 8) Inflammation

Serum Soluble Proteins:

• 1) C-Reactive Protein: Binds bacteria, activates complement, causes bacterial lysis (opsonin)
• 2) Ceruloplasmin: Oxidizes iron, inhibiting microbe iron uptake
• 3) Haptoglobin: Binds hemoglobin, inhibiting

Mineral Trioxide Aggregate (MTA) Applications

Pulp Therapy

• Pulp capping
• Furcation repair
• Strip perforation repair
• Root resorption repair
• Immature teeth
• Root end filling material

Elements of Pulp Regeneration

Therapy for exposed dental pulps using stem cells and a biofunctional scaffold, inhibiting or eliminating infection to facilitate pulp generation.

Nickel-Titanium (NiTi) Rotary Instruments

Advantages of NiTi Reciprocation

• Mimics manual movement
• Reduces risks associated with continuous rotation in curved canals

Types of Posts

1. Carbon fiber epoxy resin posts
2. Zirconia posts
3. Glass fiber reinforced posts
4. Ultra-high strength polyethylene fiber reinforced posts

Advantages of NiTi Rotary

• Gradual, evenly tapered radicular preparation
• Fewer instruments required
• Reduced

Metabolic and Biochemical Processes

BMI Calculation: BMI = Kg/M². Interpretation: <25 = Normal, 25-30 = Overweight, >30 = Obese. Ethanolamine (Ethan-NH₃), Choline = N(CH₃)₃

Leptin and Adipose Tissue

Leptin is released from adipose tissue when mass is high. It travels through the blood to the arcuate nucleus, binds to neuronal cells, and activates the JAK-STAT pathway. This increases gene expression of POMC, which produces alpha-MSH (a neurotransmitter). Alpha-MSH reaches neurons connected to adipose tissue, releasing norepinephrine. Norepinephrine binds to beta-adrenergic receptors on adipose tissue, promoting an increase (via the G-protein coupled receptor pathway and activation of PKA). This leads to upregulation of UCP1 expression and... Continue reading "Metabolic Pathways and Liposome Drug Delivery" »

Synaptic Transmission Fundamentals

• Synapse: The gap between neurons (synaptic cleft).
• Synaptic Knob: The terminal structure containing vesicles.
• Neurotransmitters: Chemicals that transmit signals.
  • Acetylcholine: Activates muscles.
  • Monoamines: Involved in cognitive processes (emotion, arousal, memory).
  • Amino Acids, Peptides, and Estrogen.
• Vesicles: Store neurotransmitters.
• Axon Hillock: Essential for initiating the firing of a neuron (action potential generation).

Postsynaptic Potentials (EPSP and IPSP)

• EPSP (Excitatory Postsynaptic Potential): Moves the membrane potential toward the threshold.
• IPSP (Inhibitory Postsynaptic Potential): Moves the membrane potential away from the threshold.

Vision and Refractive Errors

• Nearsightedness (Myopia):
  • The eyeball

Atherosclerosis: Pathogenesis & Complications

A chronic inflammatory disease of medium and large arteries, caused by endothelial injury and lipid accumulation.

Key Risk Factors:

• Hypertension
• Hyperlipidemia
• Smoking
• Diabetes

Lesions evolve from fatty streaks → fibrous plaques → complicated plaques.

Common Complications:

• Myocardial Infarction (MI)
• Stroke
• Aneurysm
• Peripheral Artery Disease

Histologically, it shows lipid cores, calcification, and fibrous caps.

Hypertensive Disease: Organ Damage & Malignant Forms

Chronic blood pressure (BP) elevation causes vascular and organ damage.

Consequences Include:

• Arteriolosclerosis
• Left Ventricular (LV) hypertrophy
• Stroke
• Chronic Kidney Disease

Malignant hypertension (diastolic BP >120 mmHg) causes fibrinoid necrosis... Continue reading "Essential Pathology Topics: Systemic Diseases & Neoplasms" »