Medicine

This deck is a friendly starting point for learning the basics of human anatomy and physiology. The cards walk you through the body's major organs, the systems they belong to, and how those systems work together to keep you alive. From the heart and lungs to the brain, bones, and immune system, it covers the foundational building blocks that any student of health or biology is expected to know.

It is well suited for beginners, whether you are preparing for a school exam, considering a career in healthcare, or simply curious about how your own body functions. Because the questions focus on core facts and definitions, the deck works as a quick refresher for medical and nursing students, and as a gentle introduction for anyone who has never studied the subject before.

To get the most out of your study sessions, try to picture the part of the body each card describes rather than just memorizing the words. Reviewing a little each day works far better than cramming, and connecting one system to another, for example linking the circulatory system to the lungs, will help the information stick longer. With steady practice, these basics will quickly start to feel like second nature.

The human body is organized into hierarchical systems that work together to maintain life. The largest organ is the skin, part of the integumentary system, covering approximately 1.5–2 m² in adults and serving as a barrier against infection, regulator of temperature, and sensory interface. The adult skeleton contains 206 bones, divided into the axial skeleton (80 bones: skull, spine, ribs) and the appendicular skeleton (126 bones: limbs, shoulders, pelvis). Three types of muscle tissue perform different mechanical roles: skeletal muscle enables voluntary movement, cardiac muscle drives involuntary heart contractions, and smooth muscle produces involuntary contractions in organs and blood vessels.

The body's internal environment relies on homeostasis, the active maintenance of stable internal conditions such as temperature, pH, blood sugar, and fluid balance despite external fluctuations. This regulation depends on feedback loops involving sensors that detect changes, control centers (often the hypothalamus) that integrate information, and effectors that carry out corrective responses. Body temperature is one well-regulated variable: the hypothalamus acts as a thermostat, triggering sweating and peripheral vasodilation when core temperature rises, and shivering with vasoconstriction when it falls. Normal body temperature is approximately 36.5–37.5°C (97.7–99.5°F), with fever generally defined at 38°C (100.4°F) or higher.

The major organ systems each have specialized roles. The digestive system includes the mouth, esophagus, stomach, small intestine, large intestine (colon), rectum, and anus, with accessory organs (liver, gallbladder, pancreas) that aid digestion. The respiratory and circulatory systems cooperate closely: the lungs exchange gases in tiny air sacs called alveoli, where oxygen diffuses into the blood and carbon dioxide diffuses out, a process called gas exchange. The heart, with its four chambers (right atrium, right ventricle, left atrium, left ventricle) and four valves (tricuspid, pulmonary, mitral, aortic), pumps blood through pulmonary circulation to the lungs and systemic circulation to the body in approximately 60 seconds. The brain, divided into cerebrum, cerebellum, and brainstem, controls all bodily functions, while the spinal cord relays signals between brain and body and controls reflexes. The lymphatic system, including lymph nodes, spleen, and thymus, drains excess tissue fluid and houses immune cells. The kidneys filter blood to produce urine, regulate electrolytes, maintain acid-base balance, and produce hormones such as erythropoietin and renin.

The cardiovascular system centers on the heart and blood vessels. Arteries carry oxygenated blood away from the heart (except the pulmonary arteries) under high pressure and have thick muscular walls, while veins return deoxygenated blood to the heart under lower pressure with valves that prevent backflow. Coronary artery disease (CAD), caused by atherosclerotic plaque narrowing the coronary arteries, can lead to angina, heart attacks, or heart failure. A heart attack (myocardial infarction) occurs when a clot blocks a coronary artery, causing heart tissue to die; symptoms include chest pain or pressure, shortness of breath, nausea, and pain radiating to the arm or jaw. Cardiac arrest, by contrast, is an electrical problem in which the heart suddenly stops beating and requires immediate CPR and defibrillation. Heart failure is a chronic condition where the heart cannot pump adequately to meet body needs, producing shortness of breath, fatigue, and swelling.

Common cardiovascular conditions include atrial fibrillation (an irregular, often rapid atrial rhythm that increases stroke risk and is treated with anticoagulants), arrhythmias (abnormal rhythms diagnosed by ECG/EKG), cardiomyopathy (diseases of the heart muscle), endocarditis (infection of the heart's inner lining), and valve disorders such as aortic stenosis, mitral regurgitation, and mitral valve prolapse. Hypertension (blood pressure consistently above 130/80 mmHg) is called the "silent killer" because it usually has no symptoms but increases the risk of heart attack, stroke, and kidney disease. Hypertensive crisis (above 180/120 mmHg) with organ damage is a medical emergency. Treatment of cardiovascular disease relies on several drug classes: ACE inhibitors and ARBs block the renin-angiotensin-aldosterone system, beta-blockers slow the heart rate and reduce blood pressure, statins lower LDL cholesterol, anticoagulants prevent clotting, and diuretics reduce fluid volume. Procedures such as angioplasty with stenting, coronary artery bypass grafting (CABG), pacemaker and ICD implantation, and cardiac catheterization restore or support cardiovascular function.

The respiratory system exchanges gases and is vulnerable to chronic and acute diseases. Chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis (exflammation with excess mucus) and emphysema (destruction of alveoli), is primarily caused by smoking. Asthma is a chronic inflammatory condition with reversible airway narrowing, causing wheezing and shortness of breath, treated with bronchodilators and inhaled corticosteroids. Other respiratory conditions include pneumonia, tuberculosis (caused by Mycobacterium tuberculosis), pulmonary embolism (a clot blocking a pulmonary artery), pulmonary fibrosis, pleural effusion, pneumothorax (collapsed lung), sleep apnea, and acute respiratory distress syndrome (ARDS). Diagnostic tools include spirometry (which measures FEV1 and FVC to distinguish obstructive from restrictive patterns), pulse oximetry (SpO2 normally 95–100%), chest X-ray, CT pulmonary angiography (the gold standard for pulmonary embolism diagnosis), and arterial blood gas analysis. Lung cancer, the leading cause of cancer death, has two main types: non-small cell (NSCLC, more common) and small cell (SCLC, more aggressive), with smoking as the predominant risk factor.

The digestive tract breaks down food mechanically and chemically, absorbing nutrients primarily in the small intestine and water in the large intestine. Common conditions include gastroesophageal reflux disease (GERD), in which stomach acid frequently backflows into the esophagus; peptic ulcers (sores in the stomach or duodenum most often caused by H. pylori infection or NSAID use); inflammatory bowel diseases (Crohn's disease, which can affect any part of the gastrointestinal tract with patchy deep inflammation, and ulcerative colitis, which causes continuous superficial inflammation of the colon and rectum); irritable bowel syndrome (a functional disorder causing pain, bloating, and altered bowel habits); celiac disease (autoimmune damage to intestinal villi triggered by gluten); and lactose intolerance (inability to digest milk sugar due to lactase deficiency). Other significant disorders include appendicitis, gallstones, pancreatitis, hepatitis (inflammation of the liver caused by viruses A, B, C, D, or E), cirrhosis (irreversible liver scarring), and fatty liver disease. Diagnostic and screening procedures include colonoscopy (recommended starting at age 45), upper endoscopy, and ultrasound.

The urinary system filters blood and maintains fluid and electrolyte balance. A urinary tract infection (UTI), most often caused by E. coli and more common in women, produces frequent and burning urination, cloudy urine, and pelvic pain; treatment requires antibiotics. Kidney stones (usually calcium oxalate) cause severe flank pain and hematuria. Chronic kidney disease (CKD), staged by glomerular filtration rate (GFR), is commonly caused by diabetes and hypertension and may progress to end-stage renal disease requiring dialysis (hemodialysis or peritoneal dialysis) or kidney transplant. Other important concepts include the nephrotic syndrome (heavy protein loss, edema, hyperlipidemia), nephritic syndrome (hematuria, hypertension, RBC casts), acute kidney injury (sudden decline in kidney function), polycystic kidney disease, and renal artery stenosis.

The reproductive system produces hormones and supports conception and childbirth. Common conditions include uterine fibroids (benign smooth muscle growths), endometriosis (uterine-lining tissue growing outside the uterus), polycystic ovary syndrome (PCOS, an endocrine disorder with irregular periods and excess androgens), and pelvic inflammatory disease. Pregnancy complications include preeclampsia (hypertension and proteinuria after 20 weeks), gestational diabetes, ectopic pregnancy (implantation outside the uterus, usually in a fallopian tube), and miscarriage. Cervical cancer, almost always caused by persistent high-risk HPV infection, can be prevented by HPV vaccination and detected early by Pap smear screening. Breast cancer is the most common cancer in women; risk factors include age, family history (BRCA mutations), and hormonal influences, and screening is performed by mammography. In men, benign prostatic hyperplasia (BPH) causes urinary symptoms in older men and is treated with alpha-blockers and 5-alpha reductase inhibitors, while prostate cancer is the most common male cancer and testicular cancer, though rare, affects young men and is highly curable. Sexually transmitted infections (chlamydia, gonorrhea, syphilis, HIV, HPV) are prevented by barrier protection, vaccination, and screening.

The endocrine system is a network of glands producing hormones that regulate metabolism, growth, reproduction, and mood. Major glands include the pituitary (the "master gland" controlling other endocrine organs), thyroid (producing T3 and T4 to regulate metabolism), parathyroid (controlling calcium via PTH), adrenal glands (producing cortisol, aldosterone, and adrenaline), and the pancreas (producing insulin and glucagon). Diabetes mellitus results from insulin problems: Type 1 is an autoimmune destruction of insulin-producing beta cells requiring lifelong insulin, while Type 2 involves insulin resistance and relative deficiency and is initially managed with metformin and lifestyle changes. Both can lead to acute complications such as diabetic ketoacidosis (DKA, mainly in Type 1) and hyperosmolar hyperglycemic state (HHS, mainly in Type 2). Chronic complications include diabetic neuropathy, nephropathy, and retinopathy. HbA1c testing reflects average blood sugar over 2–3 months (normal below 5.7%; diabetes at 6.5% or higher).

Thyroid disorders are common and well-defined. Hypothyroidism (underactive thyroid, most often caused by Hashimoto's thyroiditis) causes fatigue, weight gain, and cold sensitivity, treated with levothyroxine. Hyperthyroidism (overactive thyroid, most often caused by Graves' disease) causes weight loss, rapid heart rate, and heat intolerance, treated with antithyroid drugs, radioactive iodine, or surgery. Other endocrine disorders include Cushing's syndrome (excess cortisol causing weight gain and high blood sugar), Addison's disease (adrenal insufficiency requiring lifelong hormone replacement), pheochromocytoma (a catecholamine-secreting adrenal tumor producing episodic hypertension), diabetes insipidus, hyperparathyroidism, acromegaly (excess growth hormone in adults), PCOS, and gestational diabetes. Metabolic syndrome, defined by central obesity, high triglycerides, low HDL, hypertension, and high fasting glucose, raises the risk of cardiovascular disease and Type 2 diabetes.

The nervous system includes the central nervous system (brain and spinal cord) and the peripheral nervous system, transmitting signals through neurons. Common neurological conditions include stroke (ischemic from a clot or hemorrhagic from a ruptured vessel, identified by the FAST mnemonic: Face drooping, Arm weakness, Speech difficulty, Time to call emergency services), transient ischemic attacks (TIAs, "mini-strokes"), seizures and epilepsy, Parkinson's disease (loss of dopamine-producing neurons causing tremor and rigidity), multiple sclerosis (autoimmune attack on myelin), Alzheimer's disease and other dementias, meningitis (inflammation of the meninges), encephalitis, migraine headaches, peripheral neuropathy, and amyotrophic lateral sclerosis (ALS). The musculoskeletal system supports and moves the body; common disorders include osteoarthritis (wear-and-tear cartilage breakdown), rheumatoid arthritis (autoimmune joint inflammation), gout (uric acid crystal deposition), herniated discs, sciatica, scoliosis, carpal tunnel syndrome, fibromyalgia, osteoporosis (low bone density diagnosed by DEXA scan), and fractures. Ligaments connect bone to bone (injured in sprains), while tendons connect muscle to bone (injured in strains and tendinitis).

Blood consists of red blood cells (carrying oxygen via hemoglobin, vastly outnumbering white blood cells at about 700:1), white blood cells (fighting infection), platelets (enabling clotting), and plasma (the liquid carrying cells, nutrients, hormones, and waste). A normal complete blood count shows WBC 4,500–11,000/μL, hemoglobin 13.5–17.5 g/dL in men and 12.0–16.0 g/dL in women, and platelets 150,000–400,000/μL. Hematologic disorders include anemia (low healthy red blood cells, most commonly from iron deficiency), sickle cell disease (abnormal crescent-shaped hemoglobin causing pain crises and organ damage), hemophilia (genetic clotting factor deficiency), von Willebrand disease (the most common inherited bleeding disorder), thalassemia, leukemia (cancer of blood-forming tissues), lymphoma (cancer of the lymphatic system), and multiple myeloma (plasma cell cancer producing bone lesions and kidney damage). Treatments range from iron supplementation and blood transfusions to bone marrow transplantation and targeted therapies.

The immune system defends against pathogens through two branches: innate immunity (immediate, non-specific defenses including skin barriers, neutrophils, macrophages, and inflammation) and adaptive immunity (delayed but specific, involving T cells and B cells that produce antibodies and generate memory). Antibodies (immunoglobulins) include IgG (most abundant), IgA (mucosal surfaces), IgM (first response), IgE (allergies), and IgD (B cell activation). The four types of hypersensitivity reactions range from immediate IgE-mediated anaphylaxis to delayed T-cell-mediated contact dermatitis. Autoimmune diseases occur when the immune system attacks the body's own tissues, including Type 1 diabetes, rheumatoid arthritis, lupus (SLE), multiple sclerosis, and Hashimoto's thyroiditis.

Infectious diseases are caused by bacteria (single-celled organisms treated with antibiotics), viruses (requiring host cells, treated with antivirals when available), fungi (treated with antifungals), and parasites (treated with antiparasitics). The immune system mounts inflammation, characterized by redness, heat, swelling, pain, and loss of function. Bacterial infections are treated with antibiotics such as penicillins, cephalosporins, macrolides, fluoroquinolones, and tetracyclines; bacterial versus viral infections are distinguished clinically because antibiotics do not work against viruses. Antimicrobial stewardship addresses the growing crisis of antibiotic resistance, in which bacteria like MRSA and multi-drug resistant tuberculosis have evolved to survive standard treatments. Vaccines introduce harmless forms of a pathogen (weakened, inactivated, or a piece of it) to stimulate antibody and memory cell production, allowing the body to fight off the real pathogen quickly upon exposure. Herd immunity protects vulnerable individuals when a sufficient portion of the population is immune, with required thresholds varying by disease (about 95% for measles, 80% for polio).

Vital signs provide rapid assessment of physiological status. A normal resting heart rate for adults is 60–100 beats per minute, with well-trained athletes often having resting rates as low as 40–60 bpm; consistently elevated rates (tachycardia) or low rates (bradycardia) may indicate underlying disease. Normal blood pressure is below 120/80 mmHg, with the systolic (top) number reflecting pressure during heart contraction and diastolic (bottom) number reflecting pressure between beats; stages include elevated (120–129/<80), Stage 1 hypertension (130–139/80–89), and Stage 2 (≥140/≥90). Normal respiratory rate is 12–20 breaths per minute, and normal blood oxygen saturation (SpO2) measured by pulse oximeter is 95–100%, with values below 90% considered hypoxemia.

Common laboratory tests establish baseline health and detect disease. A complete blood count (CBC) measures red blood cells, white blood cells with differential, hemoglobin, hematocrit, and platelets, screening for infection, anemia, bleeding disorders, and blood cancers. The WBC differential distinguishes neutrophils (elevated in bacterial infections), lymphocytes (viral infections), eosinophils (allergies and parasites), monocytes, and basophils. A basic metabolic panel and comprehensive metabolic panel measure glucose, electrolytes (sodium, potassium, chloride, CO2), kidney function (BUN, creatinine), and liver function (ALT, AST, ALP, bilirubin, albumin). A lipid panel evaluates cardiovascular risk, with desirable total cholesterol below 200 mg/dL, LDL below 100 mg/dL (optimal), HDL at 60 mg/dL or higher (protective), and triglycerides below 150 mg/dL. Coagulation studies include PT/INR (extrinsic pathway, used to monitor warfarin) and PTT (intrinsic pathway, used to monitor heparin). Fasting blood sugar of 70–100 mg/dL is normal, with prediabetes at 100–125 and diabetes at 126 or higher on two occasions. The HbA1c test measures average glucose over 2–3 months. C-reactive protein (CRP) is a non-specific marker of inflammation, with high-sensitivity CRP (hs-CRP) used to assess cardiovascular risk. BNP (or NT-proBNP) is elevated in heart failure. Body Mass Index (BMI), calculated as weight in kilograms divided by height in meters squared, classifies underweight (<18.5), normal (18.5–24.9), overweight (25–29.9), and obese (≥30).

Medical imaging provides visualization of internal structures. X-rays are fast and inexpensive, ideal for bones and chest evaluation. Computed tomography (CT) combines multiple X-rays for cross-sectional images and excels in emergencies for detecting bleeding and fractures. Magnetic resonance imaging (MRI) uses magnetic fields and radio waves to produce detailed images of soft tissues (brain, spinal cord, joints) without radiation. Ultrasound uses sound waves for real-time imaging, with no radiation exposure, making it the standard for pregnancy monitoring and many bedside applications. Positron emission tomography (PET) detects metabolically active areas and is widely used in cancer staging. Other specialized tests include arterial blood gas (ABG) analysis for oxygenation and acid-base balance, electrocardiogram (ECG/EKG) for heart rhythm, echocardiogram for cardiac structure and function, spirometry for pulmonary function, colonoscopy for colorectal cancer screening (recommended from age 45), DEXA scan for bone density, and lumbar puncture for cerebrospinal fluid analysis. A screening test detects potential disease in asymptomatic people and prioritizes sensitivity, while a diagnostic test confirms or rules out disease with greater specificity.

Pharmacology encompasses how drugs interact with the body. Pharmacokinetics describes what the body does to a drug through absorption, distribution, metabolism, and excretion (ADME). The half-life of a drug is the time for its blood concentration to decrease by half, with steady state reached after approximately 4–5 half-lives. First-pass metabolism occurs when orally administered drugs are partially metabolized by the liver before reaching systemic circulation, reducing bioavailability; drugs with high first-pass effect may require sublingual, transdermal, or intravenous routes. Pharmacodynamics describes what the drug does to the body, including receptor binding and dose-response relationships. The therapeutic index compares toxic and effective doses; narrow therapeutic index drugs (warfarin, lithium, digoxin, phenytoin) require careful monitoring, while wide therapeutic index drugs have a larger safety margin.

Many drug classes are commonly used in clinical practice. Antibiotics include bactericidal drugs that kill bacteria directly (penicillins, cephalosporins) and bacteriostatic drugs that inhibit bacterial growth and allow the immune system to clear the infection (tetracyclines, macrolides). Amoxicillin, a penicillin-class antibiotic, treats ear infections, strep throat, pneumonia, and urinary tract infections. NSAIDs (ibuprofen, naproxen, aspirin) inhibit cyclooxygenase enzymes to reduce pain, fever, and inflammation, with risks including gastrointestinal bleeding, kidney impairment, and cardiovascular events. Acetaminophen (paracetamol) reduces pain and fever without anti-inflammatory effect and is easier on the stomach but can cause liver damage in overdose. Opioids (morphine, oxycodone, fentanyl) bind to opioid receptors for severe pain but carry risks of addiction, respiratory depression, and overdose death; naloxone reverses overdose. Benzodiazepines (diazepam, lorazepam) enhance GABA activity for anxiety, insomnia, and seizures, with risks of dependence and dangerous interactions with alcohol or opioids. SSRIs (fluoxetine, sertraline) are first-line antidepressants that increase serotonin. Statins (atorvastatin, simvastatin) lower LDL cholesterol by inhibiting HMG-CoA reductase. ACE inhibitors and ARBs lower blood pressure by blocking the renin-angiotensin-aldosterone system. Beta-blockers slow heart rate and reduce blood pressure. Proton pump inhibitors (omeprazole, pantoprazole) suppress stomach acid production. Antihistamines block histamine receptors to relieve allergy symptoms. Corticosteroids reduce inflammation and suppress immunity. Metformin, the first-line oral medication for Type 2 diabetes, lowers blood sugar by reducing hepatic glucose production and improving insulin sensitivity.

Drug interactions occur when one drug alters the activity of another, potentially increasing toxicity or reducing effectiveness. The cytochrome P450 enzyme system in the liver, especially CYP3A4 and CYP2D6, metabolizes most drugs; inducers (rifampin, carbamazepine, St. John's wort) speed metabolism while inhibitors (ketoconazole, grapefruit) slow it. Pharmacogenomics studies how genetic variations affect drug responses, enabling personalized prescribing. Generic drugs contain the same active ingredient as brand-name drugs at lower cost and must meet the same regulatory standards. A black box warning is the FDA's strongest safety warning, indicating serious or life-threatening risks. Special considerations include polypharmacy (taking five or more medications simultaneously, common in the elderly and associated with drug interactions and falls), loading doses (higher initial doses to rapidly achieve therapeutic levels), and the placebo effect, in which patient belief produces real physiological changes even with inert treatment.

First aid knowledge can be lifesaving in emergencies. For an unresponsive adult requiring CPR, the rescuer should call emergency services, place the person on a firm surface, position hands on the center of the chest, and perform compressions at least 5 cm (2 inches) deep at 100–120 per minute, giving two rescue breaths after every 30 compressions if trained. For a choking person who cannot cough or speak, the rescuer should perform abdominal thrusts (the Heimlich maneuver) by standing behind the person, placing a fist just above the navel, grasping it with the other hand, and applying quick upward thrusts; for infants, back blows and chest thrusts replace abdominal thrusts. Severe bleeding is controlled by applying firm direct pressure with a clean cloth, layering more material without removing soaked-through layers, elevating the injured limb above the heart when possible, and using a tourniquet only as a last resort for life-threatening limb bleeding. For burns, cool water should run over the area for at least 10–20 minutes; ice, butter, and toothpaste should be avoided. Anaphylaxis, a severe allergic reaction with throat swelling and blood pressure drop, requires immediate epinephrine (EpiPen) injection into the outer thigh and a call to emergency services. For suspected fractures, the injured area should be immobilized without attempting realignment, ice applied to reduce swelling, and immediate medical attention sought. The recovery position, with the person on their side, top leg bent for stability, and head tilted back, keeps the airway clear in unconscious but breathing individuals.

Medical ethics guides clinical decisions through four core principles: autonomy (respecting the patient's right to make informed decisions), beneficence (acting in the patient's best interest), non-maleficence ("first, do no harm"), and justice (fair distribution of healthcare resources). Informed consent requires that patients understand the purpose, benefits, risks, and alternatives of a procedure before agreeing. Patient confidentiality, protected by laws such as HIPAA, restricts sharing of health information without consent. Advance directives (living wills and healthcare power of attorney) document patient wishes when they cannot make decisions. A do-not-resuscitate (DNR) order specifies that CPR should not be attempted if the heart or breathing stops. Palliative care focuses on relieving symptoms and improving quality of life in serious illness and can be provided alongside curative treatment, while hospice care provides end-of-life comfort for patients with a prognosis of six months or less who forgo curative therapy. Brain death, defined as irreversible cessation of all brain function including the brainstem, is the legal definition of death in most jurisdictions.

Public health and epidemiology examine disease patterns in populations. Epidemiology uses incidence (new cases over time) and prevalence (total existing cases) to track disease burden, while randomized controlled trials (RCTs) remain the gold standard for evaluating treatments through random assignment and double-blinding. Evidence-based medicine integrates the best research evidence with clinical expertise and patient values, with systematic reviews and meta-analyses providing the highest level of evidence. Health outcomes are strongly influenced by social determinants of health, including income, education, employment, housing, food security, and access to care, accounting for 30–55% of health outcomes. The World Health Organization coordinates international public health efforts, including pandemic response. Quarantine separates exposed individuals to observe for symptoms, while isolation separates those who are already sick. Vaccination schedules provide protection at optimal ages, and childhood milestones such as APGAR scores (assessed at 1 and 5 minutes after birth) evaluate newborn health. Vaccine hesitancy remains a top global health threat, addressed through respectful conversation, evidence sharing, and trust-building. Burnout among healthcare workers, characterized by emotional exhaustion and depersonalization, affects roughly half of physicians and is addressed through systemic workplace changes and peer support.