300+ medical terms, defined.

Haloperidol is a high-potency, typical (first-generation) antipsychotic that blocks dopamine D2 receptors in the CNS. It's highly effective for positive symptoms of schizophrenia and acute agitation but carries high risk of extrapyramida...

Erythropoiesis is the process of red blood cell production in the bone marrow, primarily regulated by erythropoietin (EPO) from the kidneys in response to tissue hypoxia. This process takes approximately 7 days and involves stem cell dif...

Type IV collagen is the primary structural component of basement membranes, forming a sheet-like network that provides support for epithelial and endothelial cells. It is composed of α3, α4, and α5 chains in the glomerular basement membr...

The right coronary artery (RCA) is one of the two main coronary arteries that supplies blood to the heart muscle. It typically supplies the right ventricle, inferior wall of the left ventricle, and posterior wall, and gives rise to the p...

Placenta accreta is abnormal placental implantation where chorionic villi invade the myometrium due to deficient decidua basalis. It occurs most commonly with prior cesarean sections and placenta previa, causing life-threatening postpart...

The Haldane effect describes the increased ability of deoxygenated blood to carry CO2 compared to oxygenated blood. As hemoglobin releases oxygen in tissues, its affinity for CO2 increases, facilitating CO2 transport from tissues to lungs.

Truncus arteriosus is a rare congenital heart defect where a single large vessel arises from the heart and gives rise to the systemic, coronary, and pulmonary circulations. It represents failure of the truncus arteriosus to separate into...

Gray baby syndrome is a potentially fatal condition caused by chloramphenicol toxicity in neonates, characterized by gray skin discoloration, cardiovascular collapse, and high mortality. It occurs due to immature hepatic glucuronyl trans...

An embolus is an intravascular mass (thrombus, air, fat, amniotic fluid, or foreign material) that travels through the bloodstream and lodges in a distant vessel, causing vascular occlusion. Most commonly consists of dislodged thrombi fr...

Overactive bladder (OAB) is a symptom complex characterized by urinary urgency with or without urge incontinence, usually accompanied by frequency and nocturia. It affects approximately 10-15% of adults and significantly impacts quality...

Leukotrienes are pro-inflammatory lipid mediators derived from arachidonic acid via the 5-lipoxygenase pathway. They play crucial roles in asthma, allergic reactions, and inflammatory responses by causing bronchoconstriction, increased v...

Small cell lung cancer (SCLC) is an aggressive neuroendocrine tumor comprising ~15% of lung cancers, strongly associated with smoking. It has rapid growth, early metastasis, and initial responsiveness to chemotherapy but poor overall pro...

Toxocara canis is a roundworm that causes visceral larva migrans (VLM) in humans, primarily children. Infection occurs through ingestion of embryonated eggs from contaminated soil or fomites. The larvae migrate through various organs cau...

Pharyngeal pouches are endodermal outpouchings that develop between the pharyngeal arches during embryogenesis (weeks 4-5). They give rise to important structures including the thymus, parathyroid glands, palatine tonsils, and contribute...

The lectin pathway is an alternative complement activation route triggered by mannose-binding lectin (MBL) and ficolins binding to pathogen carbohydrates. It bypasses C1 but converges with classical pathway at C4, leading to C3 convertas...

Organogenesis is the process of organ formation during embryonic development, occurring primarily during weeks 3-8 of human gestation. This critical period involves the differentiation of the three primary germ layers into specific organ...

Autosomal recessive polycystic kidney disease (ARPKD) is a rare inherited disorder caused by mutations in the PKHD1 gene, characterized by bilateral enlarged cystic kidneys and congenital hepatic fibrosis. It typically presents in infanc...

Cerebral palsy is a group of permanent movement and posture disorders caused by non-progressive brain injury occurring before, during, or shortly after birth. It is the most common cause of childhood physical disability, characterized by...

Eptifibatide is a synthetic cyclic peptide that reversibly inhibits platelet glycoprotein IIb/IIIa receptors, preventing platelet aggregation. It's used as an antiplatelet agent in acute coronary syndromes and percutaneous coronary inter...

Tirofiban is a non-peptide glycoprotein IIb/IIIa receptor antagonist used as an antiplatelet agent in acute coronary syndromes. It reversibly blocks the final common pathway of platelet aggregation by preventing fibrinogen binding to act...

Abciximab is a glycoprotein IIb/IIIa receptor antagonist that prevents platelet aggregation by blocking fibrinogen binding. It's used during percutaneous coronary interventions (PCI) to reduce thrombotic complications. Major side effect...

Alcohol dehydrogenase (ADH) is the primary enzyme responsible for ethanol metabolism, converting ethanol to acetaldehyde in the liver. It follows zero-order kinetics at high alcohol concentrations and is the rate-limiting step in alcohol...

Omalizumab is a humanized monoclonal antibody that binds to free IgE, preventing it from binding to mast cells and basophils. It is used primarily for moderate to severe persistent asthma and chronic idiopathic urticaria that are inadequ...

Succinate dehydrogenase is a key enzyme in both the citric acid cycle and electron transport chain, converting succinate to fumarate while reducing FAD to FADH2. It is unique as the only enzyme that participates in both processes and is...

Diabetic retinopathy is a progressive microvascular complication of diabetes mellitus affecting retinal blood vessels, leading to vision impairment and potential blindness. It progresses from nonproliferative (background) to proliferativ...

Cerebroside is a sphingolipid composed of ceramide linked to a single sugar molecule (glucose or galactose). It's a major component of myelin sheaths and cell membranes, particularly abundant in nervous tissue. Deficiency in cerebroside...

Supine refers to a body position where the patient lies flat on their back with face upward. This position is fundamental in clinical examination, surgical procedures, and has specific physiological implications including supine hypotens...

The anterior corticospinal tract is a small motor pathway (10-15% of corticospinal fibers) that descends ipsilaterally in the anterior funiculus of the spinal cord before crossing at segmental levels. It primarily innervates axial and pr...

Sagittal refers to an anatomical plane that divides the body into left and right portions, running from anterior to posterior. The midsagittal (median) plane divides the body into equal left and right halves, while parasagittal planes cr...

The cerebral cortex is the outermost layer of gray matter in the brain, consisting of neuronal cell bodies organized into six layers. It is responsible for higher-order functions including consciousness, language, memory, and executive f...

Negative feedback is a regulatory mechanism where the output of a system inhibits or reduces the initial stimulus, maintaining homeostasis. It's the most common type of feedback loop in the human body, exemplified by hormone regulation l...

The anterior communicating artery (ACoA) is a short vessel connecting the two anterior cerebral arteries, completing the anterior portion of the Circle of Willis. It's the most common site of intracranial aneurysms and rupture can cause...

The choroid plexus is a highly vascularized structure in the brain ventricles that produces cerebrospinal fluid (CSF). It consists of specialized ependymal cells and fenestrated capillaries that form the blood-CSF barrier, producing appr...

The carotid body is a small chemoreceptor organ located at the bifurcation of the common carotid artery that detects changes in blood oxygen, carbon dioxide, and pH levels. It plays a crucial role in respiratory and cardiovascular homeos...

Secondary immunodeficiency is acquired impairment of immune function due to external factors, in contrast to primary (congenital) immunodeficiencies. Most commonly caused by HIV infection, but also results from malnutrition, medications,...

Secondary hemochromatosis is iron overload caused by external factors rather than genetic mutations. Most commonly results from repeated blood transfusions, chronic hemolytic anemia, or excessive iron supplementation. Unlike primary hemo...

Peyer patches are organized lymphoid follicles located in the ileum that serve as key immune surveillance sites for intestinal antigens. They contain specialized M cells that sample luminal contents and present antigens to underlying imm...

Primary ciliary dyskinesia (PCD) is a rare autosomal recessive disorder caused by defects in ciliary structure and function, leading to impaired mucociliary clearance. Classic triad includes chronic sinopulmonary infections, situs invers...

Staphylococcal scalded skin syndrome (SSSS) is a toxin-mediated skin condition caused by exfoliative toxins from S. aureus, primarily affecting neonates and young children. It presents with widespread erythema, superficial blistering, an...

The zona reticularis is the innermost layer of the adrenal cortex that primarily produces androgens (DHEA, androstenedione) under ACTH stimulation. It plays a crucial role in adrenarche and contributes to secondary sexual characteristics...

Bipolar I disorder is characterized by at least one manic episode lasting ≥1 week (or requiring hospitalization), often with depressive episodes. Manic episodes involve elevated mood, grandiosity, decreased need for sleep, and impaired j...

Oncogenes are mutated or overexpressed versions of normal cellular genes (proto-oncogenes) that promote cell growth and division. When activated inappropriately, they contribute to cancer development by driving uncontrolled cell prolifer...

Hyperpolarization is when a cell's membrane potential becomes more negative than its resting potential, moving further from the threshold needed for action potential generation. This typically occurs due to K+ efflux or Cl- influx, makin...

The parietal pleura is the outer layer of the pleural membrane that lines the inner chest wall, diaphragm, and mediastinum. It is innervated by somatic nerves (intercostal and phrenic) making it sensitive to pain, unlike the visceral ple...

Parainfluenza viruses (PIV) are enveloped RNA viruses that cause respiratory tract infections, particularly in children. They are a leading cause of croup (laryngotracheobronchitis) and can cause bronchiolitis, pneumonia, and upper respi...

Parvovirus B19 is a single-stranded DNA virus that causes erythema infectiosum (fifth disease) in children, characterized by a 'slapped cheek' rash. It has tropism for erythroid precursor cells and can cause transient aplastic crisis in...

Cardiac index (CI) is cardiac output normalized for body surface area, calculated as CO/BSA with normal values 2.5-4.0 L/min/m². It provides a more accurate assessment of cardiac performance than cardiac output alone by accounting for pa...

Pulmonary capillaries are the microscopic blood vessels in the lungs where gas exchange occurs between alveolar air and blood. They form an extensive network around alveoli, with walls so thin (0.5 micrometers) that they allow rapid diff...

The left circumflex artery (LCX) is one of the two main branches of the left main coronary artery, supplying the lateral and posterior walls of the left ventricle. Occlusion typically causes lateral wall MI with characteristic ECG change...

Immune complex deposition occurs when antigen-antibody complexes accumulate in tissues, triggering complement activation and inflammatory responses. This mechanism underlies Type III hypersensitivity reactions and causes diseases like sy...