2,701 articles
Two-point discrimination
Two-point discrimination (2PD), from Weber's 1834 method, measures the minimum skin separation at which two blunt contacts feel distinct; thresholds range from 1–2 mm at the tongue tip to 20–30 mm on the hand back, but nonspatial cues inflate performance, prompting the two-point orientation discrimination alternative.
Two-streams hypothesis
Two-streams hypothesis: primate visual cortex model with a ventral "what" stream to temporal cortex for perception and a dorsal "where/how" stream to parietal cortex for action; proposed by Ungerleider and Mishkin (1982) and Goodale and Milner (1992), now revised toward interacting streams.
Tympanosclerosis
Tympanosclerosis, also called myringosclerosis when limited to the eardrum, is calcified scar plaque formation in the tympanic membrane and middle ear after infection, surgery, or injury, often causing conductive hearing loss treated with tympanoplasty or hearing aids.
Tympanostomy tube
A tympanostomy tube, also called an ear tube or grommet, is a small tube inserted through the eardrum to drain fluid and ventilate the middle ear.
Type 2 myocardial infarction
Type 2 myocardial infarction (type 2 MI) is heart muscle death caused by an oxygen supply-demand imbalance without atherothrombosis, usually triggered by sepsis, arrhythmia, or anemia.
Type I vestibular sensory cell
Type I vestibular sensory cell (type I hair cell): amniote-only flask-shaped vestibular hair cell enveloped by a calyx afferent terminal, with low-voltage-activated K+ currents and both quantal and non-quantal transmission, unlike bouton-innervated type II cells.
U-138MG
U-138MG, also written U138 or U-138 MG, is a human cancer cell line from a malignant brain glioma, established in 1968 and widely used in glioblastoma research.
U-373MG ATCC
U-373MG ATCC (CVCL_2219, HTB-17) is a human glioblastoma/astrocytoma cell line shown by STR profiling and sequencing to be a U-251MG derivative, not the original 1973 Uppsala U-373MG line; ICLAC-00295, ATCC distribution discontinued.
Uganda Heart Institute
The Uganda Heart Institute is Uganda's national tertiary cardiac referral center at Mulago Hospital in Kampala, founded in 1988 and the only center offering both open-heart surgery and catheterisation.
Ulceration of conjunctiva
Ulceration of conjunctiva (conjunctival ulcer, ICD-11 9A60.30; SNOMED CT 95744009) is a necrotic depressed lesion of the eye's conjunctiva, infective (tuberculosis, herpes) or non-infective (Behçet's, Crohn's, mechanical), diagnosed by fluorescein staining.
Ulna
The ulna is the medial long bone of the human forearm, extending from the elbow to the wrist beside the radius, whose pivot around it produces pronation and supination.
Ulnar artery
The ulnar artery (arteria ulnaris) is the larger terminal branch of the brachial artery, supplying the medial forearm and most blood flow to the hand.
Ulnar claw
Ulnar claw, or claw hand (intrinsic-minus hand), is a deformity with MCP hyperextension and IP flexion of the ring and little fingers from ulnar nerve palsy, causing 60-80% pinch and grip strength loss; treated with splinting and tendon transfers.
Ulnar nerve
Ulnar nerve (nervus ulnaris): terminal branch of the medial cord of the brachial plexus, C8–T1, supplying forearm flexors and most intrinsic hand muscles and medial 1.5 digits; compressed at cubital tunnel or Guyon canal.
Ultrasonography of chronic venous insufficiency of the legs
Duplex ultrasonography (DUS) of chronic venous insufficiency of the legs, also called venous duplex or venous mapping, is the reference-standard ultrasound test for venous reflux, using segment-specific cutoffs (>500 ms superficial, >1 s deep) with the patient standing.
Ultrasonography of deep vein thrombosis
Compression ultrasonography for deep vein thrombosis: first-line ultrasound test using vein noncompressibility, with Wells score and D-dimer, pooled sensitivity about 90-98% for proximal DVT.
Umbilical cord
Umbilical cord: fetal-placental conduit with two arteries and one vein in Wharton jelly, 50–60 cm at term; carries oxygenated blood via the vein; delayed clamping 30–60 seconds is now recommended; single umbilical artery affects under 1% of pregnancies.
Umbilical vein
The umbilical vein is the single cord vessel carrying oxygenated placental blood to the fetus; normally the left of two embryonic veins, it becomes the ligamentum teres after birth and supports neonatal catheterization.
Unipolar neuron
Unipolar neuron (pseudounipolar neuron): a neuron with one process from the soma, typical of PNS sensory neurons in dorsal root and cranial nerve ganglia; develops from bipolar embryonic neurons, with axons up to 1 m or more.
Upper gastrointestinal series
Upper gastrointestinal series, also called barium swallow or UGI, is a fluoroscopic x-ray exam of the esophagus, stomach, and duodenum using drunk barium contrast, with single- and double-contrast forms, used to find ulcers, reflux, hernias, strictures, and tumors.
Upper limb
Upper limb (upper extremity): the shoulder-to-fingers region of the human body, divided into arm, forearm, and hand, with 30 bones per limb, brachial plexus innervation, and manipulation-focused anatomy.
Upper motor neuron
Upper motor neuron: cortical and brainstem neurons of the pyramidal (corticospinal and corticobulbar) tracts that synapse on lower motor neurons; lesions cause spasticity, hyperreflexia, clonus, and a positive Babinski sign.
Upper motor neuron lesion
Upper motor neuron lesion: damage to CNS motor neurons or the corticospinal/corticobulbar tracts above the anterior horn, causing weakness, spasticity, hyperreflexia, clonus, and the Babinski sign, distinct from lower motor neuron lesions.
Ureter
Ureter: muscular tube (Greek oureter) carrying urine from renal pelvis to bladder; about 25 cm, 3–4 mm wide, peristaltic, with anti-reflux intramural segment and UPJ, iliac, UVJ landmarks.
Urinary meatus
Urinary meatus (external urethral orifice): the opening of the urethra to the outside, at the tip of the penis in males and just anterior to the vaginal opening in females; site of hypospadias and meatal stenosis.
Urinary system
Urinary system (urinary tract, renal system): the kidneys, ureters, bladder, and urethra, which filter blood, produce 1-2 quarts of urine daily, store it, and void it; kidneys also regulate blood pressure, erythropoiesis, and vitamin D.
Urination
Urination (micturition, voiding): expulsion of urine from the bladder through the urethra, controlled by pontine and spinal reflexes, parasympathetic pelvic nerves, sympathetic storage pathways, and voluntary cortical control.
Urine
Urine: liquid waste made by the kidneys filtering blood, about 1-2 L/day, pH 4.5-8.0. Also called pee. Basis of urinalysis, pregnancy and drug tests; once thought sterile, now known to host a urobiome.
Uterine arteriovenous malformation
Uterine arteriovenous malformation (uterine AVM, arteriovenous fistula): a rare high-flow vascular shunt between uterine arteries and myometrial veins, usually acquired after curettage, cesarean section, or abortion, causing severe bleeding; diagnosed by Doppler ultrasound, treated by embolization or medication.
Uterine Contraction
Uterine contraction (myometrial contraction), shortening of uterine smooth muscle driven by calcium, MLCK, oxytocin, and prostaglandins; powers labor, and is monitored by tocodynamometry, intrauterine pressure catheter, and electrohysterography.