Medicine

Sleep hygiene: practices to improve sleep quality Sleep hygiene Sleep hygiene is a set of behavioral and environmental recommendations designed to promote regular, restorative sleep. It helps mild insomnia and supports overall health but may be…

African trypanosomiasis (sleeping sickness) Sleeping sickness African trypanosomiasis, or sleeping sickness, is a parasitic disease transmitted by tsetse flies that affects the blood and central nervous system; it has two clinical forms, diff…

Small intestine cancer (small bowel cancer): overview, types and care Small intestine cancer Concise encyclopedia entry on small intestine (small bowel) cancer: definition, anatomy, tumor types, symptoms, diagnosis, treatment, prognosis, epidemiology and risk factors.

Small-cell carcinoma (small-cell lung cancer) Small-cell carcinoma Aggressive neuroendocrine carcinoma most commonly of the lung, marked by rapid growth, early spread, and distinctive small-cell histology. Treated mainly with chemotherapy and radi…

Smallpox: variola virus, disease, history, vaccination and eradication Smallpox Contagious viral disease caused by variola virus. Overview of causes, symptoms, history, vaccination and global eradication, plus modern legacy and biodefense concerns.

Social distancing (physical distancing): purpose, measures, history and effects Social distancing Non-pharmaceutical practice to reduce person-to-person spread of respiratory and contact-transmitted infections; covers mechanisms, common measures, history, benefits, harms and di…

Sore throat (pharyngitis): causes, symptoms and care Sore throat Sore throat (pharyngitis) is pain or irritation in the throat. Causes range from viral infections to trauma and tumours. This article explains symptoms, common causes, diagnosis, t…

Spa (thermal baths, wellness and hydrotherapy centers) Spa A spa is a facility focused on hydrotherapy, relaxation and health treatments, from natural hot springs to modern resort services and medical rehabilitation.

Speech and language therapist Health professional who assesses and treats communication and swallowing disorders across the lifespan, using therapy, technology and multidisciplinary care to improve participatio…

Spermicide — non-hormonal contraceptive agents Spermicide A non-hormonal substance applied to the genital tract to immobilize or kill sperm. Used alone it is less reliable than other methods; commonly combined with barrier devices and ass…

Sphenoid bone Central unpaired bone of the skull base that helps form the cranial floor, houses the pituitary fossa, contains the sphenoidal sinuses, and transmits several cranial nerves and ves…

Sphygmomanometer: instrument for measuring blood pressure Sphygmomanometer A sphygmomanometer measures arterial blood pressure by inflating a cuff and recording systolic and diastolic values. Types include mercury, aneroid and digital; proper technique an…

Spinal cord: structure, function, and clinical importance Spinal cord Compact overview of the spinal cord: anatomy, protective coverings, roles in conduction and reflexes, development, and common clinical issues.

Spinal tumor: types, symptoms, diagnosis, and treatment Spinal tumor Overview of spinal tumors, their anatomical classification, common causes, clinical features, diagnostic approach and management options, with distinctions between primary and meta…

Human spleen: anatomy, immune functions, and clinical significance Spleen Comprehensive overview of the human spleen: location and structure, immune surveillance, blood filtration and storage, common disorders, trauma risks, splenectomy implications and…

Splenomegaly (enlarged spleen) Splenomegaly Splenomegaly is an abnormally enlarged spleen with multiple causes. This article summarizes mechanisms, common causes, clinical features, diagnostic approach, treatment options, an…

Sprain (ligament injury) Sprain A sprain is an overstretching or tearing of a ligament. Common in the ankle, wrist and knee, sprains range from mild to complete tears and are managed with rest, support, rehabilit…

St Thomas' Hospital — London teaching hospital with Nightingale legacy St. Thomas’ Hospital Major central London teaching hospital on the Thames, noted for its 19th-century Nightingale nurse training school, medical education, and role in the Guy's and St Thomas' NHS Foun…

Staphylococcal infection Infection caused by Staphylococcus bacteria, ranging from minor skin disease to severe invasive and toxin-mediated illnesses; includes issues of diagnosis, treatment, prevention, a…

Status epilepticus: prolonged seizures and emergency management Status epilepticus Status epilepticus is a medical emergency of prolonged or repeated seizures without recovery. Overview, types, causes, diagnosis, immediate treatment, complications, and prevention…

Stent: definition, types, uses, placement and clinical considerations Stent A stent is a tubular medical device placed inside vessels or ducts to maintain patency. This article explains types, materials, procedures, risks, history and distinctions from rel…

Stethoscope A stethoscope is an acoustic or electronic instrument used in auscultation to listen to internal body sounds—heart, lungs, bowel and blood flow—by clinicians, emergency responders…

Stevens–Johnson syndrome Stevens–Johnson syndrome (SJS) is a rare, severe mucocutaneous reaction—usually drug-related—characterized by widespread epidermal cell death, blistering, and mucosal erosions that…

Stimulant (central nervous system stimulant) Stimulant A stimulant is a substance that increases central nervous system activity, producing wakefulness and alertness. They vary widely in effect, medical use, risks and legal status.

Stomach cancer (gastric cancer): overview, types, causes, diagnosis and treatment Stomach cancer Comprehensive overview of stomach (gastric) cancer: what it is, major types, causes including H. pylori, symptoms, diagnosis, treatment options, prevention and global patterns.

Straitjacket: History, Design, Uses, and Ethical Considerations Straitjacket A straitjacket is a garment designed to restrict arm movement, historically used in psychiatric care. Article covers design, history, modern uses, safety concerns, alternatives, an…

Streptococcal pharyngitis (strep throat) Streptococcal pharyngitis Streptococcal pharyngitis, or strep throat, is a bacterial infection of the throat and tonsils caused by Group A Streptococcus; it causes fever, sore throat, swollen glands and is…

Streptococcus pneumoniae (pneumococcus) Streptococcus pneumoniae A gram-positive, alpha-hemolytic diplococcus that commonly colonizes the human nasopharynx and can cause pneumonia, meningitis, otitis media and sepsis; notable for its polysacchar…

Streptococcus pyogenes: overview, biology, diseases, and clinical importance Streptococcus pyogenes Streptococcus pyogenes (Group A Streptococcus) is a Gram‑positive bacterium that causes strep throat, skin infections and invasive disease; it produces multiple virulence factors a…

Stroke (cerebrovascular accident): causes, signs, treatment and recovery Stroke A stroke occurs when blood flow to part of the brain is interrupted or a vessel ruptures. This article covers types, symptoms, emergency care, diagnosis, prevention and rehabilitat…

Subdural hematoma: causes, presentation, diagnosis and management Subdural hematoma Subdural hematoma (SDH) is blood collecting between the dura and arachnoid layers of the meninges, usually after head injury. This article explains causes, symptoms, diagnosis, tre…

Substance abuse: causes, signs, consequences and responses Substance abuse Substance abuse is harmful, repeated use of psychoactive substances. This article explains patterns, common drugs, health and social impacts, distinctions from dependence, and appr…

Sudden cardiac death: causes, recognition, prevention, and response Sudden cardiac death Sudden cardiac death is an unexpected natural death from cardiac causes, usually within one hour of symptom onset. This article explains mechanisms, risk factors, emergency respons…

Suicidal ideation: causes, signs, assessment and support Suicidal ideation Suicidal ideation refers to thinking about, planning, or preoccupation with ending one’s life. This article explains signs, common causes, assessment, and ways to respond and seek…

Suicide prevention: strategies, risk factors, and community approaches Suicide prevention Overview of suicide prevention: goals, common strategies (means restriction, treatment, crisis response), risk and protective factors, community roles, and notable policy and progr…

Suicide Risk Assessment: Purpose, Procedure, and Clinical Considerations Suicide risk assessment An overview of suicide risk assessment: what it evaluates, common tools and steps, clinical importance, limitations, and legal and training issues for health professionals.

Sulfonamide (medicine): antibacterial class derived from sulfanilamide Sulfonamide (medicine) Sulfonamides are synthetic antimicrobial agents derived from sulfanilamide that inhibit folic acid synthesis in bacteria; historically pivotal, they remain clinically useful in spe…

Sunburn: causes, symptoms, prevention and treatment Sunburn Sunburn is skin injury from excess ultraviolet (UV) radiation. This article explains how sunburn develops, common symptoms, risk factors, prevention strategies and basic home care…

Sunscreen: Uses, Types, Safety, and Environmental Issues Sunscreen Overview of sunscreen: how it protects against UV, types of ingredients, application and safety tips, regulatory status, and environmental concerns including reef-safe debates.

Surgery: definition, methods, history, and modern practice Surgery Comprehensive overview of surgery: what it is, major types and specialties, operating room practices, anesthesia, historical advances and modern trends including access and medical…

Surgical mask: purpose, construction, history and uses Surgical mask Disposable medical face coverings worn to limit emission of respiratory droplets; distinct from respirators and cloth masks. Covers materials, performance, appropriate use, care, e…

Symptom: Definition, Types, Role in Diagnosis and Uses Beyond Medicine Symptom Overview of symptoms: subjective experiences vs objective signs, their classification, role in clinical reasoning and measurement, historical context, and uses outside medicine suc…

Syncope (fainting): causes, diagnosis, and management Syncope Syncope is a temporary loss of consciousness due to reduced blood flow to the brain. This article explains types, common causes, evaluation, treatment, prevention, and when it sign…

Syndrome: definition, causes, examples, and distinctions Syndrome A syndrome is a set of medical or psychological signs and symptoms that occur together. This article explains definitions, causes, diagnostic role, examples, historical notes, and…

Synovial sarcoma Synovial sarcoma is a rare soft-tissue cancer that most often arises near joints in the limbs. It has distinct histology and a characteristic gene fusion; diagnosis and care requir…

Syphilis: causes, stages, diagnosis, treatment and prevention Syphilis Comprehensive overview of syphilis, a bacterial sexually transmitted infection: its cause, stages, diagnosis, treatment, history, complications, and public health considerations.

Tachycardia: causes, types, diagnosis and treatment Tachycardia Tachycardia is an abnormally fast heart rate. This article explains definitions, common forms, causes, diagnosis, treatments, complications and when to seek medical care.

Tacuinum Sanitatis: medieval handbook of health and lifestyle Tacuinum sanitatis A medieval European adaptation of an 11th‑century Arabic health manual by Ibn Butlan, the Tacuinum Sanitatis records diet, plants, and six lifestyle elements for maintaining balanc…