2,701 articles
Denton Cooley
Denton A. Cooley (1920-2016), Houston cardiac surgeon, founded the Texas Heart Institute, performed the first successful U.S. heart transplant (1968) and the world's first total artificial heart implant (1969), and feuded with Michael DeBakey.
Depolarization
Depolarization is the shift of a cell's membrane potential toward less negative values, mainly via cation influx. Key in action potentials (−70 mV to +30 mV), EPSPs, depolarizing GABA, and spreading depolarization in brain injury.
Dermatome (anatomy)
Dermatome (anatomy): area of skin innervated by one spinal dorsal root, mapped by Keegan and Garrett (1948) and Foerster (1933); adjacent dermatomes overlap, and maps guide radiculopathy and spinal cord injury localization.
Desmoplakin
Desmoplakin (DSP): plakin-family protein anchoring intermediate filaments to cardiac and skin desmosomes. DSP gene mutations cause desmoplakin cardiomyopathy, a left-dominant, fibrotic, inflammation-prone arrhythmogenic cardiomyopathy distinct from PKP2 disease, plus Carvajal and Naxos syndromes.
Desquamation
Desquamation is the shedding of corneocytes from the stratum corneum, driven by kallikrein-mediated corneodesmosome degradation; impaired or excessive shedding causes scaling disorders like ichthyosis and Netherton syndrome.
Development of the human spinal cord
The human spinal cord develops from the neural tube in the fourth week of embryonic life, then ascends within the vertebral canal to end near L1 in adults.
Development of the nervous system in humans
Development of the human nervous system (neurulation): neural tube and neural crest form from ectoderm 2–3 weeks after conception; tube becomes CNS, crest builds PNS; synapses peak at ~150% adult levels in infancy.
Development of the reproductive system
Development of the reproductive system: embryology of gonads, genital ducts, external genitalia, and gonadal descent from intermediate mesoderm. Indifferent stage until week 7; SRY, testosterone, and AMH drive male differentiation; female pathway is hormone-independent.
Development of the thymus
Development of the thymus describes how the thymus arises from the third pharyngeal pouch, descends to the chest, is colonized by T cell precursors, and undergoes fat replacement after puberty.
Development of the urinary system
Development of the urinary system: embryonic formation of kidneys, ureters, bladder, and urethra via pronephros, mesonephros, and metanephros stages, ureteric bud branching morphogenesis, nephron induction, and CAKUT malformations.
Developmental venous anomaly
A developmental venous anomaly, formerly called a venous angioma, is a common benign congenital variant of the brain's venous drainage, in which small veins converge on one collector vein.
Devi Shetty (ದೇವಿ ಪ್ರಸಾದ್ ಶೆಟ್ಟಿ)
Devi Prasad Shetty (ದೇವಿ ಪ್ರಸಾದ್ ಶೆಟ್ಟಿ), born 1953, Indian cardiac surgeon, founder-chairman of Narayana Health; performed India's first neonatal heart surgery, treated Mother Teresa, pioneered Yeshasvini micro-insurance and sub-$2,000 open-heart surgery.
Diabetic cataract
Diabetic cataract: lens opacity occurring earlier and more often in diabetes (2-5 fold risk), driven by polyol-pathway sorbitol and oxidative stress; surgery carries higher complication and retinopathy-progression risks.
Diabetic retinopathy
Diabetic retinopathy, a microvascular complication of diabetes damaging retinal blood vessels, progresses from nonproliferative disease to proliferative DR and diabetic macular edema; treated with anti-VEGF injections, laser photocoagulation, and vitrectomy.
Diad
Diad (cardiac dyad): junction between a cardiomyocyte T-tubule and junctional sarcoplasmic reticulum, about 15 nm cleft, where L-type Ca2+ channels trigger RyR2 calcium-induced calcium release; cardiac counterpart of the skeletal muscle triad.
Diagnosis of brain tumors
The diagnosis of brain tumors is a stepwise workup: CT and contrast-enhanced MRI characterize a suspected mass, and biopsy with molecular profiling assigns type and grade.
Diastole
Diastole: the relaxation and filling phase of the cardiac cycle, opposite systole. Covers its four phases, diastolic blood pressure, diastolic dysfunction grading, and the 2025 ASE echocardiography guidelines.
Diastolic function
Diastolic function is the left ventricle's ability to relax and fill with blood during diastole, assessed mainly by echocardiography and central to heart failure with preserved ejection fraction.
Diffuse axonal injury
Diffuse axonal injury (DAI), also called traumatic axonal injury (TAI), is widespread white-matter axon rupture from acceleration-deceleration forces in TBI; graded by Adams system, best seen on MRI/SWI, diagnosed in 40-50% of hospitalized TBI.
Diffuse capillary malformation with overgrowth
Diffuse capillary malformation with overgrowth (DCMO), ORPHA:714737, is a rare congenital vascular anomaly syndrome with extensive pink reticulated capillary malformations, proportionate overgrowth, and foot anomalies, linked to somatic PIK3CA, GNAQ, or GNA11 variants.
Diffuse Noxious Inhibitory Control
Diffuse noxious inhibitory control (DNIC), termed conditioned pain modulation (CPM) in humans, is a pain-inhibits-pain mechanism described by Le Bars in 1979, mediated by a brainstem spino-bulbo-spinal loop acting on wide dynamic range neurons.
Digastric muscle
Digastric muscle (musculus digastricus), a two-bellied suprahyoid neck muscle joining mandible, hyoid, and temporal bone via an intermediate tendon. Dual innervation: anterior belly CN V3 mylohyoid nerve, posterior belly CN VII; depresses mandible, elevates hyoid.
Digestion
Digestion is the mechanical and chemical breakdown of food into absorbable nutrients in the GI tract, involving the mouth, stomach, small intestine, and accessory organs; differs between monogastric humans and pigs and ruminants like cattle.
Digestion and absorption
Digestion and absorption: the gastrointestinal processes that break food into monosaccharides, amino acids, and fatty acids and move them across the small-intestinal epithelium via paracellular and transcellular transport, and how maldigestion and malabsorption arise.
Digit ratio
Digit ratio (2D:4D) is index finger length divided by ring finger length; lower in males, proposed in 1998 as a prenatal testosterone marker, though large meta-analyses find weak hormone validation.
Digital subtraction angiography
Digital subtraction angiography (DSA): fluoroscopic X-ray technique subtracting a pre-contrast mask image from contrast-filled frames to show vessels; gold standard in neurovascular imaging since 1980.
Dimple
Dimple: a small skin indentation, most often on the cheek, caused by a bifid zygomaticus major muscle tethering the skin during smiling; also chin dimples, genetics, and dimpleplasty.
DIPG trial
DIPG trial: clinical studies for diffuse intrinsic pontine glioma (DIPG), a fatal pediatric brainstem tumor. Key trials include hypofractionated radiotherapy comparisons, BIOMEDE targeted therapy, NCT03620032 re-irradiation, and CAR T studies.
Diplopia
Diplopia (double vision): perception of two images of one object. Monocular diplopia persists with one eye open (cataract, astigmatism); binocular diplopia resolves when either eye closes and signals ocular misalignment, from decompensated phoria to cranial nerve palsy.
Direct tributaries of the portal vein
The direct tributaries of the portal vein are the left and right gastric, cystic, and paraumbilical veins, which join the hepatic portal vein itself rather than its large forming trunks.