1500+ medical terms, defined.

PPROM (Preterm Premature Rupture of Membranes) is the rupture of fetal membranes before 37 weeks gestation and prior to the onset of labor. It is a leading cause of preterm birth and increases risk of maternal and fetal infection, cord p...

The growth plate (physis) is a hyaline cartilage disc located between the epiphysis and metaphysis of long bones, responsible for longitudinal bone growth during childhood and adolescence. It closes and is replaced by bone (epiphyseal fu...

Anaplasia refers to the loss of cellular differentiation, a hallmark feature of malignant neoplasms. Anaplastic cells lack normal structure and function, resembling primitive or undifferentiated cells. This feature is associated with agg...

The frontal lobe is the largest lobe of the cerebral cortex, located anterior to the central sulcus. It governs executive function, personality, voluntary motor control, and expressive language (Broca's area). Damage produces disinhibiti...

Autoimmune hepatitis (AIH) is a chronic immune-mediated liver disease characterized by hepatocyte destruction due to loss of self-tolerance, predominantly affecting young to middle-aged women. It presents with elevated transaminases, hyp...

Fenofibrate is a fibrate-class lipid-lowering drug primarily used to treat severe hypertriglyceridemia and mixed dyslipidemia. It works via PPAR-alpha activation, increasing lipoprotein lipase activity, which significantly lowers triglyc...

A nasogastric (NG) tube is a flexible tube inserted through the nose into the stomach, used for decompression, feeding, or medication administration. Common indications include bowel obstruction, ileus, GI bleeding evaluation, and short-...

Indirect (unconjugated) bilirubin is the lipid-soluble, water-insoluble form of bilirubin produced from heme breakdown, bound to albumin in the blood, before being conjugated by the liver enzyme UGT1A1. Elevated levels cause jaundice and...

The inguinal canal is an oblique passage through the anterior abdominal wall, extending from the deep (internal) inguinal ring to the superficial (external) inguinal ring. It transmits the spermatic cord in males or round ligament of the...

Dry gangrene is a form of coagulative necrosis of tissue, typically affecting extremities, caused by chronic ischemia (usually from arterial occlusion) in the absence of infection. It presents as dry, shriveled, dark brown-black tissue w...

An obligate aerobe is a microorganism that requires oxygen for growth and survival because it relies on aerobic respiration (oxidative phosphorylation) to generate ATP. These organisms possess catalase and/or superoxide dismutase to deto...

Dubin-Johnson syndrome is a benign, autosomal recessive disorder causing conjugated (direct) hyperbilirubinemia due to a defect in the hepatocyte canalicular multidrug resistance protein 2 (MRP2/cMOAT), which impairs excretion of conjuga...

Hepatic fibrosis is the excessive accumulation of extracellular matrix (ECM) proteins, primarily collagen, in the liver in response to chronic injury. It results from activation of hepatic stellate cells into myofibroblast-like cells tha...

Plummer-Vinson syndrome is a triad of iron deficiency anemia, esophageal webs, and dysphagia, often accompanied by glossitis (atrophic tongue). It predominantly affects middle-aged women and is associated with an increased risk of esopha...

An anaerobe is a microorganism that does not require oxygen for growth and, in the case of obligate anaerobes, is often harmed by oxygen due to lack of enzymes like catalase and superoxide dismutase (SOD) that detoxify reactive oxygen sp...

The brush border is the microvilli-covered apical surface of absorptive epithelial cells, most notably in the small intestine and proximal renal tubule, that maximizes surface area for absorption and digestion. It contains key membrane-b...

Crypts of Lieberkühn (intestinal glands) are tubular invaginations of the mucosa between intestinal villi in both the small and large intestine. They contain stem cells, Paneth cells, and other differentiated cells responsible for epithe...

The amygdala is an almond-shaped nucleus located in the medial temporal lobe, part of the limbic system, primarily responsible for processing emotions—especially fear, anxiety, and aggression—and for emotional memory formation. It plays...

Fentanyl is a synthetic opioid agonist, roughly 50-100 times more potent than morphine, used for anesthesia and severe pain management. It acts primarily on mu-opioid receptors, providing rapid onset and short duration of action. It carr...

Neural tube defects (NTDs) result from failure of neural tube closure during the 3rd-4th week of embryonic development, leading to malformations such as spina bifida, anencephaly, and encephalocele. They are strongly associated with fola...

The processus vaginalis is a peritoneal outpouching that precedes testicular descent through the inguinal canal into the scrotum. It normally obliterates after birth, leaving the tunica vaginalis. Its failure to close is the embryologic...

Omeprazole is a proton pump inhibitor (PPI) that irreversibly inhibits the H+/K+ ATPase in gastric parietal cells, profoundly suppressing gastric acid secretion. It is used to treat GERD, peptic ulcer disease, H. pylori eradication (as p...

The cardinal (Mackenrodt's) ligament is a dense fibrous connective tissue band extending from the lateral cervix and upper vagina to the pelvic sidewall, providing primary support to the uterus and cervix. It runs within the base of the...

A tracheostomy is a surgical procedure creating an opening (stoma) through the neck into the trachea, typically between the 2nd-3rd or 3rd-4th tracheal rings, to establish an airway. It is used for prolonged mechanical ventilation, upper...

Intestinal-type gastric adenocarcinoma is a histologic subtype of gastric cancer characterized by gland-forming, well-differentiated tumor cells that resemble intestinal epithelium. It typically arises from a background of chronic atroph...

Phenylalanine hydroxylase (PAH) is a liver enzyme that converts phenylalanine to tyrosine using tetrahydrobiopterin (BH4) as a cofactor. Deficiency of PAH causes phenylketonuria (PKU), an autosomal recessive disorder leading to phenylala...

Atezolizumab is a humanized monoclonal antibody that inhibits PD-L1, blocking its interaction with PD-1 and B7.1 receptors on T cells, thereby enhancing anti-tumor immune responses. It is used in treating various cancers including non-sm...

The suspensory ligament of the ovary (infundibulopelvic ligament) is a fold of peritoneum that connects the ovary to the pelvic wall and contains the ovarian artery, ovarian vein, lymphatics, and nerves. It is a critical surgical landmar...

Apixaban is an oral, direct factor Xa inhibitor used for anticoagulation. It is FDA-approved for stroke prevention in nonvalvular atrial fibrillation, treatment/prevention of DVT/PE, and VTE prophylaxis after hip/knee replacement. It doe...

Durvalumab is a human IgG1 monoclonal antibody that inhibits PD-L1, blocking its interaction with PD-1 and B7.1, thereby restoring T-cell mediated antitumor immunity. It is FDA-approved for unresectable stage III non-small cell lung canc...

The infundibulopelvic (IP) ligament, also known as the suspensory ligament of the ovary, is a fold of peritoneum that connects the ovary to the lateral pelvic wall. It contains the ovarian artery, ovarian vein, lymphatics, and nerves sup...

Aldolase B is a liver enzyme that catalyzes the cleavage of fructose-1-phosphate in the fructose metabolism pathway; its deficiency causes hereditary fructose intolerance. Serum aldolase (muscle isoform) is also used as a nonspecific mar...

Risperidone is a second-generation (atypical) antipsychotic used to treat schizophrenia, bipolar disorder, and irritability associated with autism. It acts primarily as a dopamine D2 and serotonin 5-HT2A receptor antagonist, giving it a...

BRCA2 is a tumor suppressor gene located on chromosome 13q that plays a critical role in DNA double-strand break repair via homologous recombination. Germline mutations significantly increase lifetime risk of breast, ovarian, prostate, a...

The alveolar sac is a cluster of alveoli that share a common opening into an alveolar duct, forming the terminal air-filled structures of the respiratory tree where gas exchange occurs. It represents the final generation of the respirato...

Osteomalacia and rickets result from defective mineralization of bone matrix (osteoid), most commonly due to vitamin D deficiency. Rickets occurs in children with open growth plates, causing skeletal deformities, while osteomalacia occur...

The zona fasciculata is the middle layer of the adrenal cortex, primarily responsible for synthesizing and secreting glucocorticoids, mainly cortisol, in response to ACTH stimulation. It comprises the largest portion of the cortex and is...

Dupuytren contracture is a fibroproliferative disorder of the palmar fascia leading to progressive flexion contractures of the fingers, most commonly the ring and little fingers. It is associated with alcoholism, cirrhosis, diabetes mell...

The Winter formula predicts the expected respiratory compensation (PaCO2) for a primary metabolic acidosis: Expected PaCO2 = 1.5(HCO3-) + 8 ± 2. It helps determine if a mixed acid-base disorder is present alongside the primary metabolic...

The optic cup is the central, pale depression within the optic disc where retinal ganglion cell axons converge to exit the eye as the optic nerve. The cup-to-disc (C/D) ratio, normally ≤0.3-0.4, is a key clinical measurement used to asse...

The cerebral aqueduct (aqueduct of Sylvius) is a narrow channel in the midbrain that connects the third ventricle to the fourth ventricle, allowing cerebrospinal fluid (CSF) flow. It is a common site of obstruction leading to noncommunic...

The thyroid follicle is the basic functional unit of the thyroid gland, consisting of a spherical structure lined by follicular epithelial cells and filled with colloid, which stores thyroglobulin. These follicles are the site of thyroid...

The pseudoglandular period (weeks 5–17 of fetal development) is a stage of lung development characterized by branching of bronchioles into terminal bronchioles, giving the lung a gland-like histological appearance. No respiratory bronchi...

Essential amino acids (EAAs) are amino acids that cannot be synthesized endogenously by the human body and must be obtained through diet. There are 9 essential amino acids in humans: Phenylalanine, Valine, Tryptophan, Threonine, Isoleuci...

Negative selection is a process in T cell development in the thymus in which T cells that bind too strongly to self-antigens presented on MHC molecules are eliminated via apoptosis. This process occurs at the corticomedullary junction an...

Famotidine is a histamine H2-receptor antagonist used to reduce gastric acid secretion, commonly prescribed for GERD, peptic ulcer disease, and stress ulcer prophylaxis. It works by blocking H2 receptors on gastric parietal cells, decrea...

Variant angina (Prinzmetal angina) is chest pain caused by transient coronary artery vasospasm rather than fixed atherosclerotic obstruction. It classically occurs at rest, often in the early morning hours, and causes transient ST-segmen...

The HPG axis is a hormonal feedback system regulating reproduction and sexual development. GnRH from the hypothalamus stimulates pituitary release of LH and FSH, which act on the gonads to produce sex steroids and gametes. This axis is c...

Pepsin is a proteolytic enzyme secreted by gastric chief cells as inactive pepsinogen, then activated by HCl in the stomach's acidic environment. It cleaves proteins into smaller peptides, initiating protein digestion. It functions optim...

The urogenital sinus is a transient embryonic structure formed by division of the cloaca that gives rise to the bladder, urethra, and parts of the reproductive tract. It develops after the urorectal septum separates the cloaca into the u...