Anatomy and Physiological Systems

A sound understanding of anatomy and physiology is foundational to all clinical nursing practice in the UAE. Nurses must understand how body systems function normally in order to recognise and respond to abnormalities. For the DOH (UAE) licensure examination, questions on physiology frequently integrate with clinical scenarios — requiring you to apply your knowledge of how organs and systems work to patient care decisions. This is especially important in the UAE, where the high prevalence of metabolic diseases (diabetes, hypertension, obesity) means nurses frequently care for patients with multi-system complications.

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🟢 Lite — Quick Review (1h–1d)

Rapid summary for last-minute revision before your exam.

Key Organ Systems and Their Core Functions:

System	Key Organs	Primary Function
Cardiovascular	Heart, arteries, veins	Circulation, oxygen/nutrient delivery
Respiratory	Lungs, airways	Gas exchange (O₂ in, CO₂ out)
Nervous	Brain, spinal cord, nerves	Control, coordination, sensation
GI/Gastrointestinal	Stomach, intestines, liver	Digestion, absorption, metabolism
Renal/Urinary	Kidneys, bladder	Filtration, excretion, fluid balance
Endocrine	Thyroid, pancreas, adrenals	Hormonal regulation
Musculoskeletal	Bones, muscles, joints	Movement, support, protection
Immune/Lymphatic	Lymph nodes, spleen, WBCs	Defence, immunity

Acid-Base Balance — Quick Reference:

Disorder	pH	PaCO₂	HCO₃⁻	Cause
Respiratory acidosis	↓	↑	Normal	Hypoventilation
Respiratory alkalosis	↑	↓	Normal	Hyperventilation
Metabolic acidosis	↓	Normal	↓	Lactic acidosis, DKA, renal failure
Metabolic alkalosis	↑	Normal	↑	Vomiting, diuretics

⚡ Exam Tip: When interpreting ABGs, read the pH first — it tells you whether the primary problem is acidosis or alkalosis. Then look at what would compensate: in primary respiratory disorders, the kidneys compensate (HCO₃⁻ changes); in primary metabolic disorders, the lungs compensate (PaCO₂ changes).

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🟡 Standard — Regular Study (2d–2mo)

Standard content for students with a few days to months.

1. The Cardiovascular System

Cardiac Conduction System:

1. SA node (sinoatrial — the pacemaker) → 60–100 bpm
2. AV node (atrioventricular) → brief delay for atrial contraction before ventricular contraction
3. Bundle of His → right and left bundle branches
4. Purkinje fibres → ventricular depolarisation

Cardiac Cycle:

• Systole: Atrial contraction (atrial kick — contributes 20–30% of ventricular filling) → Ventricular contraction → Ejection
• Diastole: Ventricular relaxation → Passive filling (majority of ventricular filling) → Atrial contraction (atrial kick)
• Total cycle: ~0.8 seconds at 75 bpm

Stroke Volume (SV) = End-Diastolic Volume (EDV) − End-Systolic Volume (ESV)

• Normal SV: 70 mL
• Cardiac Output (CO) = HR × SV
• Normal CO: 4–8 L/min

Factors Affecting Cardiac Output:

• Preload (venous return/EDV): Increased by IV fluids; decreased by haemorrhage
• Afterload (arterial resistance): Increased by hypertension, vasoconstriction
• Contractility (heart muscle strength): Increased by sympathetic stimulation, catecholamines; decreased by hypoxia, acidosis
• Heart rate: CO increases with HR until ~160–180 bpm (when diastolic filling time is too short)

Coronary Circulation:

• Right coronary artery (RCA): Supplies SA node (~60%), AV node (~90%), right ventricle
• Left coronary artery (LCA) → Left anterior descending (LAD) + Circumflex
• LAD: Supplies anterior wall, anterior 2/3 of interventricular septum — “widow-maker” territory (LAD occlusion = massive MI)
• Most MI occurs in left coronary territory

2. The Respiratory System

Gas Exchange — Alveolar Gas Equation: PAO₂ = FiO₂ × (Patm − PH₂O) − (PaCO₂ ÷ RQ) Where RQ (respiratory quotient) = 0.8

Oxygen Transport:

• 98.5% bound to haemoglobin (as oxyhaemoglobin)
• 1.5% dissolved in plasma (as partial pressure PO₂)
• Each gram of haemoglobin carries 1.34 mL O₂ when fully saturated

Ventilation-Perfusion (V/Q) Mismatch:

• Normal V/Q = 0.8: Ventilation and perfusion are matched
• V/Q = 0 ( shunt): Ventilation present, no perfusion (e.g., pulmonary embolism — perfusion defect)
• V/Q = ∞ (dead space): Perfusion present, no ventilation (e.g., pulmonary embolism — the well-ventilated but non-perfused areas)

Respiratory Mechanics:

• Inspiration: Active process; diaphragm contracts and flattens, external intercostals elevate ribs; intrathoracic pressure drops below atmospheric → air flows in
• Expiration: Passive in normal breathing; elastic recoil of lungs and chest wall; active in forced expiration
• Compliance: Ability of lungs to expand (reduced in pulmonary fibrosis, chest wall deformity; increased in emphysema)
• Resistance: Opposition to airflow (increased in asthma, COPD, bronchospasm)

3. The Renal System

Nephron — Functional Unit of the Kidney:

• Each kidney has ~1 million nephrons
• Each nephron: Glomerulus → Proximal convoluted tubule → Loop of Henle → Distal convoluted tubule → Collecting duct

GFR (Glomerular Filtration Rate):

• Normal: 90–120 mL/min/1.73 m²
• Best estimate: Creatinine clearance (Cockcroft-Gault equation) or eGFR (MDRD/CKD-EPI formulas)
• Decreased GFR = impaired kidney function = drug dose adjustment needed

Key Renal Functions:

1. Filtration of blood (glomeruli)
2. Reabsorption of water and solutes (tubules)
3. Secretion of wastes (tubules)
4. Regulation of fluid and electrolyte balance
5. Regulation of acid-base balance (via bicarbonate reabsorption and acid excretion)
6. Hormone production: Erythropoietin (RBC production), Renin (blood pressure), Active Vitamin D (calcium metabolism)

Micturition Reflex:

• Bladder fills (detrusor muscle relaxed; internal sphincter closed)
• At 300–400 mL: Stretch receptors signal brainstem
• Conscious decision to void: Relax external urethral sphincter (pontine storage centre → micturition centre)
• Detrusor contracts → bladder empties

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🔴 Extended — Deep Study (3m+)

Comprehensive coverage for students on a longer study timeline.

4. The Endocrine System — Focus on Gulf Region Conditions

Thyroid Disorders:

• Hypothyroidism (more common in Middle East due to iodine deficiency in some areas): Fatigue, weight gain, cold intolerance, bradycardia, constipation, dry skin, goitre
• Hyperthyroidism (Graves’ disease): Weight loss, heat intolerance, tachycardia, tremor, anxiety, exophthalmos (Graves’特有的)
• Thyroid storm (thyrotoxic crisis): Life-threatening; fever, delirium, tachycardia, heart failure; precipitated by infection, surgery, radioactive iodine
• Management of thyroid storm: Propylthiouracil (PTU) or methimazole; potassium iodide (SSKI); propranolol; hydrocortisone

Diabetes Mellitus — UAE’s Biggest Health Crisis:

• UAE has among the highest Type 2 DM prevalence in the world (~17% adults; much higher in nationals ~20–25%)
• Type 1 DM: Autoimmune destruction of pancreatic beta cells; absolute insulin deficiency; younger patients; prone to DKA
• Type 2 DM: Insulin resistance + relative insulin deficiency; older patients; associated with obesity, sedentary lifestyle; progressive beta-cell failure

Metabolic Syndrome in UAE: Cluster of conditions increasing cardiovascular risk:

• Central obesity (waist circumference: men >102 cm, women >88 cm — adapted for Middle Eastern populations)
• Triglycerides ≥ 150 mg/dL
• HDL: men < 40 mg/dL, women < 50 mg/dL
• Blood pressure ≥ 130/85 mmHg
• Fasting glucose ≥ 100 mg/dL

Adrenal Glands:

• Adrenal medulla: Catecholamines (adrenaline, noradrenaline) → fight or flight
• Adrenal cortex:
  • Zona glomerulosa: Aldosterone (mineralocorticoid — ↑Na⁺, ↓K⁺; regulated by RAAS)
  • Zona fasciculata: Cortisol (glucocorticoid — ↑blood glucose, anti-inflammatory; stress response)
  • Zona reticularis: Androgens (sex hormones)

Adrenal Crisis (Addisonian Crisis):

• Acute adrenal insufficiency from sudden withdrawal of chronic steroid therapy, or primary adrenal failure
• Hypotension, tachycardia, weakness, confusion, hyponatraemia, hyperkalaemia, hypoglycaemia
• Medical emergency: IV hydrocortisone + aggressive fluid resuscitation

5. The Gastrointestinal System

Gastric Secretions:

• Parietal cells secrete HCl and intrinsic factor (for B12 absorption)
• Chief cells secrete pepsinogen (converted to pepsin by HCl)
• G cells secrete gastrin (stimulates acid secretion)
• pH of stomach: 1.5–3.5 (highly acidic)

Liver Functions — Critical in UAE Clinical Context:

1. Bile production and secretion (fat emulsification and vitamin K absorption)
2. Carbohydrate metabolism (glycogen storage, gluconeogenesis)
3. Protein synthesis (albumin, clotting factors, complement)
4. Drug and toxin metabolism (CYP450 system)
5. Urea cycle (excretion of ammonia)
6. Storage (fat-soluble vitamins, iron, copper)
7. Immune function (Kupffer cells remove bacteria from portal blood)

Portal Circulation: Nutrients absorbed from GI tract → portal vein → liver → hepatic veins → IVC

• First-pass metabolism: Drugs and toxins can be partially cleared by liver before reaching systemic circulation
• Clinical relevance: Portal hypertension (cirrhosis) → oesophageal varices, splenomegaly, ascites

Pancreas — Exocrine and Endocrine:

• Exocrine: Pancreatic juice (amylase, lipase, trypsinogen) → neutralises gastric acid, digests carbs, fats, proteins
• Endocrine: Islets of Langerhans → Insulin (beta cells), Glucagon (alpha cells)
• In UAE: Pancreatic cancer and chronic pancreatitis are seen; alcohol-related pancreatitis is increasing

Exam Watch: The DOH exam frequently presents scenarios of patients with electrolyte imbalances (hyperkalaemia, hyponatraemia) or acid-base disturbances in the context of common UAE diseases (diabetes with DKA, heart failure with diuretic use, liver disease with ascites). Understanding the underlying physiology allows you to anticipate complications and prioritise nursing interventions.

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