2,701 articles
Ocular dominance
Ocular dominance: behavioral preference for one eye and its cortical counterpart, ocular dominance columns in V1, described by Hubel and Wiesel; covers critical-period plasticity, deprivation, amblyopia, and the unsupported link to reading skill.
Ocular motor nerve palsies
Ocular motor nerve palsies are deficits of cranial nerves III, IV, and VI causing diplopia. Also called third, fourth, sixth nerve palsy. Causes include microvascular ischemia, inflammation, aneurysm, tumor; pupil-involving third palsy is an emergency.
Ocular surface squamous neoplasia
Ocular surface squamous neoplasia (OSSN), also called conjunctival intraepithelial neoplasia spectrum, is a dysplasia-to-invasive-squamous-cell-carcinoma continuum of the conjunctiva and cornea, linked to UVB, HPV, and HIV, treated by excision or topical interferon, 5-FU, or mitomycin C.
Oculomotor nerve
Oculomotor nerve (cranial nerve III): midbrain motor nerve supplying four extraocular muscles, levator palpebrae, and pupil constriction via Edinger-Westphal fibers; palsy causes ptosis, diplopia, down-and-out eye, pupil-involving from aneurysm or herniation.
Oculomotor nerve palsy
Oculomotor nerve palsy (third cranial nerve palsy, CN III palsy) causes ptosis, diplopia, and a down-and-out eye; pupil involvement signals aneurysm and urgent imaging, while pupil sparing suggests microvascular ischemia.
Off-pump coronary artery bypass
Off-pump coronary artery bypass (OPCAB, OPCABG) is beating-heart coronary bypass grafting without cardiopulmonary bypass, first performed by Goetz in 1960, revived in the 1980s, offering less stroke but more repeat revascularization than on-pump CABG.
Old age
Old age: the later stage of human life, WHO threshold 60 years; not a disease in ICD-11, renamed 'Ageing associated decline in intrinsic capacity'; 1 billion people 60+ in 2019 rising to 2.1 billion by 2050.
Olecranon
Olecranon: the proximal ulnar projection forming the bony tip of the elbow, triceps insertion site; prone to fracture (Mayo classification, ORIF or tension band wiring) and olecranon bursitis.
Olfactory bulb
Olfactory bulb: first central processing station for smell in the forebrain, receiving olfactory nerve input in glomeruli (100-200 um) and relaying via mitral and tufted cells to piriform cortex; site of adult neurogenesis and a marker in neurodegenerative disease.
Olfactory nerve
The olfactory nerve, or CN I, is the first cranial nerve, carrying smell signals from the roof of the nasal cavity to the olfactory bulbs of the brain.
Olfactory receptor cell
Olfactory receptor cell, also called olfactory receptor neuron or olfactory sensory neuron: bipolar neuron in the nasal olfactory epithelium that detects odorants via GPCR-cAMP transduction in its cilia and sends unmyelinated axons to the olfactory bulb; each expresses one odorant receptor and turns over throughout life.
Oligodendrocyte
Oligodendrocyte, also called oligodendroglia: CNS glial cell forming myelin sheaths around multiple axons (up to 1–40), unlike single-axon Schwann cells; arises from OPCs, supports axons metabolically, and enables remyelination in multiple sclerosis.
Oligodendrocyte precursor cell
Oligodendrocyte precursor cells (OPCs), also called NG2 glia or polydendrocytes, are CNS glia that generate myelinating oligodendrocytes, receive synaptic input, remodel synapses, support the blood-brain barrier, and drive remyelination in multiple sclerosis.
Oligodendroglioma
Oligodendroglioma, also known as an oligodendroglial tumor, is a brain tumor defined by an IDH mutation and 1p/19q codeletion, most common between ages 35 and 44 and often first causing seizures.
Oliver Sacks
Oliver Sacks (1933–2015), British-born neurologist and author in New York, wrote Awakenings and The Man Who Mistook His Wife for a Hat; known for narrative case histories, L-dopa work at Beth Abraham, and later accuracy controversies.
Olivocochlear system
Olivocochlear system: brainstem-to-cochlea efferent pathway from the superior olivary complex, divided into medial (MOC, outer hair cells, cholinergic gain reduction) and lateral (LOC) divisions, studied via otoacoustic emissions for protection and speech-in-noise roles.
Omohyoid muscle
The omohyoid muscle (musculus omohyoideus) is a paired infrahyoid muscle of the anterior neck running from the upper scapula to the hyoid bone, which it depresses after swallowing.
Oncotic pressure
Oncotic pressure (colloid osmotic pressure) is the osmotic pull of plasma proteins, mainly albumin (up to 80%), across capillary walls; a Starling force revised by the endothelial glycocalyx model, central to edema and fluid therapy.
Onda 10
Onda 10 (no.10, CVCL_3075) is a human glioblastoma/anaplastic glioma cell line established by Onda et al. from the left parietal lobe of a 62-year-old Japanese man, TP53-mutant, GFAP-positive early on, distributed as JCRB IFO50368.
Ophthalmic Administration
Ophthalmic administration: delivering drugs to the eye via topical, intravitreal, periocular, systemic, intracameral, and suprachoroidal routes, shaped by ocular barriers and low topical bioavailability.
Ophthalmic artery
Ophthalmic artery: first branch of the internal carotid artery, supplying the eye and orbit via the central retinal and ciliary arteries; variant origins in 2–3%, occlusion is a sight-threatening emergency.
Ophthalmology
Ophthalmology, the medical and surgical specialty for eye and visual system disorders; ophthalmologists train 12-13 years, board certified since 1916, distinct from optometrists (OD).
Opioid receptor
Opioid receptors (MOP/MOR, DOP/DOR, KOP/KOR, and the opioid-related NOP) are Gi/o-coupled GPCRs for endorphins, enkephalins, and dynorphins, mediating analgesia, reward, and respiratory depression; key targets of morphine, fentanyl, naloxone, and biased agonists like oliceridine.
Opsin
Opsin: light-sensitive seven-transmembrane GPCR apoprotein that binds retinal via a Schiff base; forms rhodopsin and visual pigments (Type II animal opsins), distinct from Type I microbial opsins used in optogenetics.
Optic chiasm
Optic chiasm: brain-base structure where optic nerves partially decussate, nasal retinal fibers crossing (about 53:47 crossed-to-uncrossed), enabling binocular vision; pituitary tumor compression causes bitemporal hemianopia.
Optic disc
Optic disc (optic nerve head): retinal site where ganglion cell axons exit as the optic nerve; no photoreceptors, so it forms the blind spot; central retinal vessels pass through it; key glaucoma and papilledema landmark.
Optic disc swelling
Optic disc swelling (disc edema, papilledema when from raised intracranial pressure) is axoplasmic-stasis swelling of the optic nerve head, distinguished from pseudoedema such as optic disc drusen by OCT and fundus findings.
Optic nerve
Optic nerve (cranial nerve II, nervus opticus): the CNS white-matter tract of about 1.2 million retinal ganglion cell axons carrying vision from retina to chiasm and brain; myelinated by oligodendrocytes, afferent limb of the light reflex, limited regeneration.
Optic nerve avulsion
Optic nerve avulsion (ONA, Evulsio nervi optici) is traumatic disinsertion of optic nerve fibers at the lamina cribrosa after blunt ocular trauma; rare, causes permanent severe vision loss, no effective treatment.
Oral mucosa
The oral mucosa, also called the mouth mucosa, is the moist tissue lining the inside of the mouth, protecting it from mechanical, chemical, thermal, and microbial damage.