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List of neurological conditions and disorders
Neurological conditions and disorders, also called nervous system diseases, affect the brain, spinal cord, and nerves; over 600 exist, including stroke, epilepsy, migraine, Alzheimer's, Parkinson's, and multiple sclerosis, the leading global cause of disability.
List of Nobel laureates in Physiology or Medicine
List of Nobel laureates in Physiology or Medicine: annual prize awarded 116 times to 232 laureates 1901-2025, first to Emil von Behring; selected by the Nobel Assembly at Karolinska Institutet; 2026 went to Deisseroth, Hegemann, and Nagel for optogenetics.
List of organs of the human body
List of organs of the human body: catalogs the body's roughly 78 to 80 organs across 11 organ systems, including vital organs (brain, heart, lungs, liver, kidneys) and recent additions the mesentery (2016) and interstitium (2018).
List of regions in the human brain
Regions of the human brain: cerebrum, cerebellum, brainstem (midbrain, pons, medulla), diencephalon, six cerebral lobes, cortical areas, and modern atlas parcellations such as AHRAv2 and Brodmann areas.
Little finger
Little finger (pinky, fifth digit, digit V): the smallest, ulnar-most finger of the human hand. Contributes about 15% of individual grip force; its exclusion cuts grip strength 33%; fifth metacarpal fractures (boxer's fractures) are about one-third of adult hand fractures.
Littoral cell hemangioma of the spleen
Littoral cell hemangioma of the spleen, also called littoral cell angioma (LCA), is a rare splenic vascular tumor of littoral cells, first described by Falk in 1991, usually benign, diagnosed by histology and immunohistochemistry.
Live Birth
A live birth is the delivery of an infant who breathes or shows any sign of life, such as a heartbeat, regardless of pregnancy length, per the WHO definition.
Liver
The liver is the body's largest internal organ and gland, a 1.2–1.5 kg wedge in the right upper abdomen with dual portal-venous and arterial blood supply, hundreds of metabolic functions, unique full-size regeneration, and a long history from Babylonian divination to transplantation.
Livor mortis
Livor mortis, also called postmortem hypostasis or lividity, is the gravity-dependent reddish-purple skin discoloration after death; onset within 20 minutes to 2 hours, fixed after 8 to 12 hours, useful for timing death and detecting body movement.
Lobes of the brain
Lobes of the brain: the six conventional divisions of each cerebral hemisphere (frontal, parietal, temporal, occipital, insula, limbic), their sulcal and imaginary-line boundaries, lobe-level functions, and the history and limits of functional localization.
Lobulated kidney
Lobulated kidney, or persistent fetal lobulation (renculation), is a benign anatomical variant where fetal renal lobules fail to fuse fully, leaving surface indentations between pyramids; found in about 10% of adults, it mimics tumors or scars on ultrasound but enhances like normal parenchyma on CT and MRI.
Local anesthesia
Local anesthesia: numbing a limited body area with sodium-channel-blocking drugs while the patient stays conscious. From cocaine (Koller, 1884) and Bier's 1898 spinal to lidocaine, bupivacaine, LAST management, and local-versus-general outcome comparisons.
Local Field Potential Measurement
Local field potential (LFP) measurement records low-frequency extracellular brain voltage, below about 300 Hz, from intracerebral microelectrodes; also called micro- or depth EEG. It reflects summed synaptic currents of neuronal populations and is used in adaptive deep brain stimulation.
Local interneuron
Local interneuron (local circuit neuron): a neuron with a locally confined axon; in cortex, GABAergic cells (~20-30% of neurons) in PV, SST, and 5HT3aR classes, born in ganglionic eminences, linked to epilepsy, schizophrenia, autism.
LOCATION trial
LOCATION trial (NCT07388030), a 2x2 factorial randomized trial in China comparing intravascular lithotripsy versus balloon angioplasty and OCT- versus angiography-guided stenting in 3,060 patients with severely calcified coronary lesions; primary endpoint 3-year target vessel failure.
Locked-in syndrome
Locked-in syndrome (LIS): rare neurological state of quadriplegia, anarthria, and lower cranial nerve paralysis with fully preserved consciousness, usually from ventral pons stroke; communication via eye movements, eye trackers, or BCIs.
Loeys–Dietz syndrome
Loeys–Dietz syndrome (LDS), or Loeys-Dietz aortic aneurysm syndrome, is an autosomal dominant connective tissue disorder caused by TGF-beta pathway gene variants (TGFBR1/2, SMAD2/3, TGFB2/3, IPO8), marked by aggressive aortic and arterial aneurysms, craniofacial and skeletal features, and allergic disease.
Loin
Loin: the body region on either side of the lower spine between ribs and pelvis, also a cut of meat. From Latin lumbus via Old French loigne; source of lumbar, sirloin, and loin pain.
Long-term depression
Long-term depression (LTD) is a long-lasting weakening of synaptic transmission induced by prolonged low-frequency stimulation, mainly via AMPA receptor internalization; key forms are NMDAR-dependent and mGluR-dependent LTD, studied in hippocampus and cerebellum.
Long-term potentiation
Long-term potentiation (LTP), originally called long-lasting potentiation, is a long-lasting increase in synaptic strength after brief high-frequency stimulation, first reported by Bliss and Lømo in 1973.
Looking
Looking is pointing the eyes toward a location via fixation or smooth pursuit, distinct from covert attention. Covers saccades (20–30 ms), fixations (200–500 ms), gaze following, and eye-tracking methods.
Loop of Henle
Loop of Henle (Henle's loop), the U-shaped nephron segment described by Jacob Henle in 1862; a countercurrent multiplier whose water-permeable descending limb and salt-transporting thick ascending limb build the renal medullary osmotic gradient for urine concentration.
Lower limb atherosclerosis
Lower limb atherosclerosis is the thickening of artery walls from fatty buildup such as cholesterol in the leg arteries, evaluated and treated as peripheral artery disease.
Lower motor neuron
Lower motor neuron: the cholinergic neurons of the spinal cord ventral horn and brainstem motor nuclei whose axons innervate skeletal muscle; Sherrington's final common pathway, forming motor units, with flaccid weakness, hyporeflexia, fasciculations, and atrophy when damaged.
Lown–Ganong–Levine syndrome
Lown–Ganong–Levine (LGL) syndrome, or short PR–normal QRS syndrome, a proposed pre-excitation syndrome described in 1952 with PR under 120 ms, normal QRS, no delta wave, and paroxysmal SVT; now considered an outdated diagnosis.
Lugaro cell
Lugaro cell, or fusiform cell of Lugaro: a GABAergic/glycinergic inhibitory interneuron of the cerebellar cortex, first described by Ernesto Lugaro in 1894 in cat; fusiform soma under the Purkinje cell layer, inhibits Golgi and molecular layer interneurons.
Lumbago with sciatica
Lumbago with sciatica (ICD-11 ME84.20) is low back pain with radiating leg pain, historically called sciatica; usually caused by lumbar disc herniation, now preferably termed radicular pain or radiculopathy.
Lumbar arteries
The lumbar arteries (arteriae lumbales) are usually four pairs of arteries arising from the abdominal aorta that supply the spinal cord and posterior abdominal wall.
Lumbar nerves
Lumbar nerves: five pairs of mixed spinal nerves L1-L5 exiting below their vertebrae, dividing into dorsal and ventral rami, forming the lumbar plexus (T12-L4) and, via the lumbosacral trunk, the sacral plexus.
Lumbar plexus
Lumbar plexus: somatic nerve network from L1-L4 ventral rami (often with T12 subcostal contribution) lying within psoas major; six branches including femoral and obturator nerves; mean variation prevalence 20.1%.