Life and health

External cephalic version

External cephalic version (ECV) is a manual obstetric procedure in which a clinician presses on the pregnant woman's abdomen to turn a breech fetus head-down, performed from 36 to 37 weeks.

External dacryocystorhinostomy

External dacryocystorhinostomy (external DCR, EX-DCR) is an ophthalmic surgical procedure that treats nasolacrimal duct obstruction by creating a new tear-drainage pathway from the lacrimal sac into the nasal cavity.

External fertilization

External fertilization: union of sperm and eggs outside the parents' bodies, via spawning in water. Used by most fish, amphibians, corals, and many invertebrates; ancestral to internal fertilization, requiring synchronized release and huge gamete numbers.

External fixation

External fixation is a surgical technique that stabilizes broken bones with pins or wires through the skin, connected by an adjustable external frame, leaving soft tissues accessible.

Oct 20, 2026

External Fixators

An external fixator is an orthopedic device that stabilizes fractures with pins or wires through the bone, connected to a frame outside the skin that allows wound access.

External hirudiniasis

External hirudiniasis (leech infestation of the skin; ICD-11 1G02, ICD-10-CM B88.3) is painless skin attachment by bloodsucking leeches, causing prolonged bleeding from hirudin, itching, and possible allergic or Aeromonas infection; distinct from internal hirudiniasis (B83.4).

External morphology of Odonata

External morphology of Odonata: body structure of dragonflies and damselflies (Anisoptera, Zygoptera), covering compound eyes, wing venation with nodus and pterostigma, basal complex, secondary male genitalia, and suborder differences.

External quality assessment

External quality assessment, also known as proficiency testing, is a laboratory medicine procedure in which an external organization sends blinded specimens to laboratories and evaluates their results.

Externalizing disorder

An externalizing disorder is a mental disorder involving outward-directed behavior such as aggression, impulsivity, and rule breaking, spanning conditions like ADHD, conduct disorder, and antisocial personality disorder.

Extinct arthropods of North America

Extinct arthropods of North America: trilobites of Laurentia (521 to 252 million years ago, over 22,000 species), Burgess Shale-type soft-bodied Cambrian arthropods, giant Arthropleura, eurypterids, and Quaternary insects from caves and packrat middens.

Extinct in the wild

Extinct in the Wild (EW) is an IUCN Red List category for species surviving only in captivity, cultivation, or naturalized populations outside their past range; 73 species held the status in 2019, with recoveries including Arabian oryx and scimitar-horned oryx.

Extinct stony coral genera

Extinct stony coral genera: extinct genera of Scleractinia, aragonite-skeletoned corals first appearing ~241 Myr; ~30% of Maastrichtian genera died out at the K-T boundary, with deep-water, cosmopolitan, non-symbiotic, solitary genera surviving.

Extinction

Extinction: the permanent disappearance of a species or taxon. Covers background versus mass extinction, the Big Five events, Cuvier's 1812 proof, IUCN assessment, and the contested sixth mass extinction.

Extinction event

Extinction event (mass extinction): a geologically short interval when at least 75% of species die out. Five Big Five events in 500 million years; a debated human-driven sixth is under discussion.

Extinction events in rugose and tabulate coral history

Extinction events in rugose and tabulate coral history: end-Ordovician, Late Devonian (Kellwasser), Carboniferous, and end-Permian crises that shaped and finally eliminated the Paleozoic Rugosa and Tabulata.

Oct 20, 2026

ExTINGUISH trial

ExTINGUISH (NCT04372615) is the first NIH-funded phase 2B randomized, double-blind, placebo-controlled trial of inebilizumab 300 mg, an anti-CD19 antibody, added to first-line therapy in 116 participants aged 12+ with moderate-to-severe anti-NMDAR encephalitis, primary endpoint mRS change at 16 weeks.

Extra marker chromosomes

Extra marker chromosomes, or small supernumerary marker chromosomes (sSMC), are tiny structurally abnormal extra chromosomes, usually no larger than chromosome 20, found in 0.043% of newborns and characterized by FISH or array CGH.

Extracapsular cataract extraction

Extracapsular cataract extraction is cataract surgery that removes the lens nucleus and cortex through a 10 mm limbal incision while leaving the capsule intact, usually followed by lens implantation.

Extracellular fluid

Extracellular fluid (ECF), all body water outside cells, about one third of body fluid volume, divided into interstitial fluid, plasma, and transcellular fluid; sodium-dominated, osmolality 280-295 mOsm/kg, regulated by vasopressin, thirst, and the renin-aldosterone system.

Extracellular matrix

Extracellular matrix (ECM): the protein and polysaccharide network between cells, including collagens, fibronectin, laminins, and proteoglycans, that supports tissue structure, signals through integrins, drives wound healing, and underlies ECM-based biomaterials.

Extracellular matrix organization

Extracellular matrix organization (GO:0030198; Reactome R-HSA-1474244): the cellular process of assembling, arranging, and disassembling the ECM of collagens, elastin, fibronectin, laminins, and proteoglycans, remodeled by MMPs and ADAMTS.

Extracellular membrane protein, CFEM domain

CFEM domain (Common in Fungal Extracellular Membrane, PF05730, IPR008427): a fungus-specific ~60-amino-acid, eight-cysteine extracellular protein domain of Ascomycota and Basidiomycota, involved in heme acquisition, pathogenesis, and host penetration.

Extracellular serine/threonine protein kinase four-jointed, N-terminal

Four-jointed (Fj; FJX1 in mammals), N-terminal region of a secretory pathway serine/threonine protein kinase, first identified in Drosophila in 1943; phosphorylates extracellular cadherin domains of Fat and Dachsous in the Golgi lumen.

Extracellular signal-regulated kinases

Extracellular signal-regulated kinases ERK1/ERK2 (MAPK3/MAPK1), terminal kinases of the RAS-RAF-MEK-ERK cascade, activated by TEY-motif dual phosphorylation, proline-directed S/TP kinases, functionally redundant, dysregulated in ~30% of cancers.

Extracellular sulfatase

Extracellular sulfatases are secreted or cell-surface enzymes, encoded in mammals by SULF1 and SULF2 (the Sulfs), that edit heparan sulfate sulfation to control signaling, with opposing roles in cancer.

Extracorporeal anastomosis

Extracorporeal anastomosis is a surgical technique in which two segments of intestine are joined outside the body during laparoscopic or robotic surgery, most often after removal of part of the colon.

Extracorporeal carbon dioxide removal

Extracorporeal carbon dioxide removal (ECCO2R) is a critical care technique that removes carbon dioxide from blood via a membrane, easing ventilation in severe ARDS and COPD.

Extracorporeal cardiopulmonary resuscitation

Extracorporeal cardiopulmonary resuscitation (ECPR) is a resuscitation technique that starts VA-ECMO during cardiac arrest unresponsive to conventional CPR, buying time to diagnose and treat the cause of the arrest.

Extracorporeal Circulation

Extracorporeal circulation (ECC), or cardiopulmonary bypass, diverts blood through an external circuit with a pump and oxygenator to replace heart and lung function, enabling open-heart surgery since Gibbon's 1953 operation and extended support as ECMO.