Medicine

Evidence-based medicine (EBM) is the conscientious, explicit, and judicious use of the best available research evidence in making decisions about patient care. It integrates clinical expertise with the best external evidence from systematic research and the patient's own values and preferences. The hierarchy of evidence places systematic reviews and randomized controlled trials at the top, followed by cohort studies, case-control studies, and expert opinion.

Pathophysiology is the study of the disordered physiological processes that cause, result from, or are associated with a disease or injury. It bridges normal physiology and clinical medicine by explaining the mechanisms through which diseases produce signs and symptoms. Understanding pathophysiology is essential for rational diagnosis and treatment.

Pharmacology is the study of how drugs interact with biological systems to produce therapeutic effects. It encompasses pharmacokinetics (what the body does to a drug, including absorption, distribution, metabolism, and excretion) and pharmacodynamics (what the drug does to the body, including receptor binding and downstream effects). Understanding these principles allows physicians to select appropriate drugs, doses, and dosing intervals.

Diagnosis is the process of identifying a disease or condition by evaluating a patient's symptoms, medical history, physical examination findings, and results from laboratory tests and imaging studies. Clinicians develop a differential diagnosis, which is a ranked list of possible conditions that could explain the patient's presentation, and then systematically narrow it down through further investigation.

Vital signs are the fundamental clinical measurements that indicate the status of a patient's essential body functions. The primary vital signs are body temperature, pulse rate, respiratory rate, and blood pressure, with oxygen saturation often considered the fifth vital sign. Deviations from normal ranges provide early warning of physiological deterioration and guide clinical decision-making.

The immune system is a complex network of cells, tissues, and organs that defends the body against infectious agents and abnormal cells. It consists of innate immunity, which provides rapid nonspecific defense through barriers, phagocytes, and inflammation, and adaptive immunity, which generates highly specific responses through T lymphocytes and B lymphocytes that produce antibodies. Immunological memory enables faster and stronger responses upon re-exposure to previously encountered pathogens.

The cardiovascular system consists of the heart, blood vessels, and blood, and is responsible for transporting oxygen, nutrients, hormones, and waste products throughout the body. The heart functions as a dual pump: the right side pumps deoxygenated blood to the lungs for gas exchange, while the left side pumps oxygenated blood to the systemic circulation. Cardiovascular diseases, including coronary artery disease, heart failure, and stroke, are the leading cause of death worldwide.

Infectious diseases are disorders caused by pathogenic microorganisms including bacteria, viruses, fungi, and parasites. Transmission can occur through direct contact, respiratory droplets, fecal-oral routes, vector-borne transmission, or vertical transmission from mother to child. Treatment depends on the causative agent and may include antibiotics, antivirals, antifungals, or antiparasitic agents, while prevention strategies include vaccination, sanitation, and infection control practices.

Medical ethics is the application of moral principles to the practice of medicine. The four foundational principles, as articulated by Beauchamp and Childress, are autonomy (respecting the patient's right to make informed decisions), beneficence (acting in the patient's best interest), nonmaleficence (avoiding harm), and justice (fair distribution of healthcare resources). These principles guide clinicians through complex situations involving informed consent, end-of-life care, confidentiality, and resource allocation.

Preventive medicine focuses on protecting, promoting, and maintaining health and well-being, and on preventing disease, disability, and premature death. It operates at three levels: primary prevention aims to prevent disease before it occurs (e.g., vaccination, lifestyle modification), secondary prevention detects disease in early stages through screening (e.g., mammography, colonoscopy), and tertiary prevention manages established disease to reduce complications and improve quality of life.