Biomedical Sciences: Anatomy, Physiology, Biochemistry, Pathology, Microbiology and Pharmacology
What you must know
Biomedical questions reward systematic recall across five strands. Anatomy: bony landmarks of maxilla and mandible, the temporomandibular joint, muscles of mastication, the trigeminal divisions (V1 ophthalmic, V2 maxillary, V3 mandibular - only V3 carries motor fibres, to the masticatory muscles plus mylohyoid, anterior digastric and tensor veli palatini), and the five terminal branches of the facial nerve (temporal, zygomatic, buccal, marginal mandibular, cervical). Physiology: calcium homeostasis (parathyroid hormone raises serum calcium and lowers phosphate), salivary flow and buffering, and the nociceptive pathway. Biochemistry: enamel hydroxyapatite, the Stephan curve and the critical pH of about 5.5. Pathology: acute versus chronic inflammation, radicular granuloma versus cyst, dysplasia versus neoplasia. Microbiology: mutans streptococci and lactobacilli in caries; the anaerobic Gram-negative biofilm of periodontitis; blood-borne virus transmission. Pharmacology: local anaesthetic pKa and onset, maximum doses, vasoconstrictors, antibiotics, NSAIDs and bisphosphonate-related osteonecrosis of the jaw.
Traps
Candidates muddle V2 and V3 sensory territories, confuse the facial artery with the maxillary artery, and forget that PTH is phosphaturic. Vivid distractors swap the pKa rule (higher pKa means less unionised base at tissue pH, therefore slower onset). Antibiotic questions punish reflexive amoxicillin answers: metronidazole covers anaerobes in periodontal infection, and antibiotics never substitute for debridement.
Worked rule of thumb: maximum local anaesthetic dose
Lidocaine with adrenaline: 7 mg/kg (ceiling 500 mg); plain lidocaine 4.4 mg/kg. For a 60 kg adult with 2% lidocaine plus 1:100,000 adrenaline: 60 × 7 = 420 mg allowed. A 2% solution holds 20 mg/mL, so 420 ÷ 20 = 21 mL. Always check the cartridge volume and the vasoconstrictor before quoting a figure.