PMDC National Licensing Examination Basic Medical Sciences Syllabus

Which muscle is the only one that opens the jaw, and what nerve supplies the muscles of mastication?

The lateral pterygoid opens the jaw (protrusion/depression). All four muscles of mastication (masseter, temporalis, medial and lateral pterygoid) are supplied by the mandibular division of the trigeminal nerve (CN V3).

Describe the blood supply of the brain via the Circle of Willis.

It is formed by the anterior cerebral arteries connected by the anterior communicating artery, and the posterior cerebral arteries connected to the internal carotid system via the posterior communicating arteries. It links the internal carotid (anterior) and vertebrobasilar (posterior) circulations.

What deficits result from a lesion of the hypoglossal nerve (CN XII)?

It supplies all intrinsic and most extrinsic tongue muscles. A lower motor neuron lesion causes the tongue to deviate toward the side of the lesion on protrusion ('lick your wounds'), with ipsilateral atrophy and fasciculations.

What are the three germ layers and a key derivative of each?

Ectoderm (epidermis, nervous system), Mesoderm (muscle, bone, cardiovascular, urogenital, connective tissue), and Endoderm (epithelial lining of GI and respiratory tracts, liver, pancreas).

What is gastrulation and on what day/week does it occur?

Gastrulation is the process during the 3rd week where the bilaminar disc becomes a trilaminar disc (ectoderm, mesoderm, endoderm) through the formation of the primitive streak and migration of epiblast cells.

What does the notochord become in the adult, and what is its primary inductive role?

The notochord persists as the nucleus pulposus of the intervertebral disc. Its primary role is inducing the overlying ectoderm to form the neural plate (neurulation) and establishing the body axis.

Differentiate the timing/effects of teratogen exposure during the pre-embryonic, embryonic, and fetal periods.

Weeks 1-2 (pre-embryonic): 'all or none' effect (spontaneous abortion or no effect). Weeks 3-8 (embryonic/organogenesis): most susceptible to major structural anomalies. Week 9 onward (fetal): functional defects and minor anomalies.

What is the fate of the paramesonephric (Mullerian) ducts and mesonephric (Wolffian) ducts in females?

Paramesonephric (Mullerian) ducts form the uterus, fallopian tubes, cervix, and upper vagina. The mesonephric (Wolffian) ducts regress in females due to the absence of testosterone.

What is the embryological cause of a tracheoesophageal fistula and its most common type?

It results from improper division of the foregut by the tracheoesophageal septum. The most common type (about 85%) is esophageal atresia with a distal tracheoesophageal fistula, presenting with polyhydramnios and choking on feeds.

Explain the embryological origin of a Meckel's diverticulum and its 'rule of 2s'.

It is a persistent remnant of the vitelline (omphalomesenteric) duct. Rule of 2s: 2% of population, 2 feet from the ileocecal valve, 2 inches long, 2 types of ectopic tissue (gastric and pancreatic), presents before age 2.

What congenital anomaly results from failure of the neural tube to close, and what marker is elevated?

Neural tube defects (e.g., spina bifida, anencephaly) result from failure of neuropore closure. Maternal serum and amniotic alpha-fetoprotein (AFP) are elevated. Folic acid supplementation reduces the risk.

What is the embryological basis of a cleft lip versus a cleft palate?

Cleft lip results from failure of fusion of the maxillary prominence with the medial nasal prominence. Cleft palate results from failure of fusion of the palatal shelves (lateral palatine processes) with each other or the nasal septum.

List the four basic tissue types and their general functions.

1) Epithelial (covering/lining and secretion), 2) Connective (support and binding), 3) Muscular (contraction/movement), 4) Nervous (conduction of impulses).

Differentiate the three types of cartilage by their matrix fibers and a location of each.

Hyaline cartilage (type II collagen; articular surfaces, trachea). Elastic cartilage (elastic fibers; epiglottis, external ear). Fibrocartilage (type I collagen, dense; intervertebral discs, pubic symphysis).

Compare the three types of muscle tissue: skeletal, cardiac, and smooth.

Skeletal: striated, multinucleate, voluntary, peripheral nuclei. Cardiac: striated, branched, single central nucleus, involuntary, has intercalated discs. Smooth: non-striated, single central nucleus, involuntary, spindle-shaped.

Name the cells of bone and their functions.

Osteoblasts (form/secrete osteoid bone matrix), osteocytes (mature cells in lacunae that maintain bone), osteoclasts (multinucleated cells that resorb bone, derived from monocytes), and osteoprogenitor (stem) cells.

What are the three types of capillaries, and where is each found?

Continuous (uninterrupted endothelium; muscle, brain/BBB, lung). Fenestrated (have pores; kidney glomerulus, intestine, endocrine glands). Sinusoidal/discontinuous (large gaps; liver, spleen, bone marrow).

Describe the histological layers (tunics) of the GI tract from lumen outward.

1) Mucosa (epithelium, lamina propria, muscularis mucosae), 2) Submucosa (contains Meissner's plexus), 3) Muscularis externa (inner circular, outer longitudinal, with Auerbach's/myenteric plexus between), 4) Serosa/adventitia.

What histological features distinguish the trachea from the esophagus?

Trachea: pseudostratified ciliated columnar epithelium with goblet cells, C-shaped hyaline cartilage rings, and trachealis (smooth) muscle. Esophagus: non-keratinized stratified squamous epithelium with mucous glands and (in lower third) smooth muscle.

What is the Frank-Starling law of the heart?

The stroke volume of the heart increases in response to an increase in the volume of blood filling the heart (end-diastolic volume/preload). Increased venous return stretches the myocardial fibers, increasing the force of contraction.

Write the formula for cardiac output and define normal resting values.

Cardiac Output (CO) = Heart Rate (HR) x Stroke Volume (SV). Normal: roughly 5 L/min (HR about 70 bpm x SV about 70 mL). Cardiac index = CO / body surface area.

Define the four phases of the cardiac cycle related to ventricular pressure-volume.

1) Isovolumetric contraction (all valves closed, pressure rises), 2) Ventricular ejection (aortic/pulmonary valves open), 3) Isovolumetric relaxation (all valves closed, pressure falls), 4) Ventricular filling (AV valves open).

What ionic events produce the phases of the cardiac ventricular action potential?

Phase 0: rapid Na+ influx (depolarization). Phase 1: transient K+ efflux. Phase 2: plateau (Ca2+ influx balances K+ efflux). Phase 3: K+ efflux (repolarization). Phase 4: resting potential maintained by Na/K ATPase.

Write the equation for mean arterial pressure (MAP) and for systemic vascular resistance.

MAP = Diastolic BP + 1/3(Pulse Pressure), or MAP = CO x SVR. Pulse pressure = Systolic - Diastolic. SVR = (MAP - CVP) / CO.

What is the conduction pathway of the heart's electrical impulse?

SA node (pacemaker) → AV node (delay) → Bundle of His → right and left bundle branches → Purkinje fibers → ventricular myocardium. The SA node has the fastest intrinsic rate (about 60-100/min).

Define tidal volume, residual volume, vital capacity, and functional residual capacity.

Tidal volume (TV): air per normal breath (~500 mL). Residual volume (RV): air left after maximal expiration. Vital capacity = TV + IRV + ERV (max air expelled after max inspiration). Functional residual capacity (FRC) = ERV + RV.

State the alveolar gas equation and its purpose.

PAO2 = FiO2 x (Patm - PH2O) - (PaCO2 / R), where R is the respiratory quotient (~0.8). It calculates alveolar oxygen partial pressure and is used to compute the A-a gradient.

Describe the oxygen-hemoglobin dissociation curve and factors causing a rightward shift.

It is sigmoid-shaped. A rightward shift (decreased O2 affinity, easier unloading) is caused by increased CO2, increased H+ (lower pH, Bohr effect), increased temperature, and increased 2,3-BPG. Mnemonic: 'CADET face Right' (CO2, Acid, 2,3-DPG, Exercise, Temperature).

What is the renal clearance formula, and why is inulin used to measure GFR?

Clearance = (Urine concentration x Urine flow) / Plasma concentration. Inulin is used because it is freely filtered, neither reabsorbed nor secreted, so its clearance equals the glomerular filtration rate (GFR).

Describe the Henderson-Hasselbalch equation and normal blood pH/bicarbonate values.

pH = 6.1 + log([HCO3-] / (0.03 x PaCO2)). Normal arterial pH is 7.35-7.45, bicarbonate (HCO3-) is 22-26 mEq/L, and PaCO2 is 35-45 mmHg.

Classify the four primary acid-base disorders with their primary changes and compensation.

Metabolic acidosis: low HCO3- (compensate with hyperventilation, low PaCO2). Metabolic alkalosis: high HCO3- (compensate with hypoventilation). Respiratory acidosis: high PaCO2 (compensate with renal HCO3- retention). Respiratory alkalosis: low PaCO2 (compensate with renal HCO3- excretion).

Where do aldosterone and ADH act in the nephron, and what are their effects?

Aldosterone acts on the principal cells of the collecting duct/distal tubule, increasing Na+ reabsorption and K+/H+ secretion. ADH (vasopressin) acts on the collecting duct, inserting aquaporin-2 channels to increase water reabsorption.

Outline the renin-angiotensin-aldosterone system (RAAS) pathway.

Low BP/Na+ triggers renin release from the juxtaglomerular cells. Renin converts angiotensinogen to angiotensin I. ACE (in lungs) converts it to angiotensin II, which causes vasoconstriction and stimulates aldosterone release, raising blood pressure and Na+ retention.

Compare the actions of insulin and glucagon on blood glucose.

Insulin (from beta cells) lowers blood glucose by promoting glucose uptake, glycogenesis, and lipogenesis. Glucagon (from alpha cells) raises blood glucose by stimulating glycogenolysis and gluconeogenesis in the liver.

What are the hormones of the anterior pituitary and a target/function of each?

FSH/LH (gonads), ACTH (adrenal cortex/cortisol), TSH (thyroid), Prolactin (milk production), GH (growth/IGF-1). Mnemonic: 'FLAT PiG'. The posterior pituitary stores ADH and oxytocin.

Describe the hormonal control of the menstrual cycle's ovulation.

Rising estrogen from the dominant follicle exerts positive feedback on the anterior pituitary, triggering an LH surge around day 14. This LH surge induces ovulation and converts the follicle into the corpus luteum, which secretes progesterone.

Compare the actions of the thyroid hormones T3/T4 and the effect of calcitonin vs PTH on calcium.

T3/T4 increase basal metabolic rate, heat production, and protein/carbohydrate metabolism. For calcium: PTH (parathyroid) raises serum calcium (bone resorption, renal reabsorption, vitamin D activation), while calcitonin (thyroid C-cells) lowers serum calcium.