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Merkel cell
Merkel cell (Tastzelle), an epidermal mechanosensory cell in the basal skin layer, forming the Merkel cell-neurite complex with Aβ SA1 fibers for light touch; PIEZO2-dependent, ATOH1-specified, epidermal origin; linked to Merkel cell carcinoma.
Mesentery
Mesentery: continuous double fold of peritoneum attaching the intestines to the posterior abdominal wall, carrying vessels, lymphatics, and nerves; redesignated a single organ in 2016, spanning duodenojejunal flexure to anorectal junction.
Mesolimbic pathway
Mesolimbic pathway: dopamine projection from the ventral tegmental area to limbic structures, chiefly the nucleus accumbens. Central to reward, incentive salience ('wanting'), prediction error learning, addiction, depression, and schizophrenia research.
Metacarpal bones
Metacarpal bones (metacarpals): the five palm bones of each hand connecting wrist to fingers and thumb, numbered 1-5, each with head, neck, shaft, base; commonly fractured, boxer's fracture hits the fifth.
Metachromatic leukodystrophy
Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal storage disease caused by ARSA mutations and arylsulfatase A deficiency, causing sulfatide buildup and demyelination; late-infantile, juvenile, and adult forms; treated with Lenmeldy gene therapy.
Metatarsal bones
Metatarsal bones: the five long bones of the forefoot (ossa metatarsi) between tarsals and phalanges; 1st shortest and widest, 2nd longest, bearing 30-50% of gait load; sites of Lisfranc and march fractures.
Methemoglobin
Methemoglobin (MetHb, ferrihemoglobin) is hemoglobin with heme iron oxidized to Fe3+, unable to bind oxygen; excess causes methemoglobinemia, treated with methylene blue or ascorbic acid.
Miami Project to Cure Paralysis
Miami Project to Cure Paralysis: spinal cord injury research center at University of Miami Miller School of Medicine, founded 1985 by Barth Green and Nick Buoniconti after Marc Buoniconti's injury; Buoniconti Fund has raised over $550 million; housed in Lois Pope LIFE Center; hypothermia and Schwann cell trials.
Michael DeBakey
Michael E. DeBakey (1908–2008), born Michel Dabaghi, American cardiovascular surgeon at Baylor College of Medicine; invented the roller pump for heart-lung machines, pioneered bypass and aneurysm surgery, Dacron grafts, and MASH units, and won the Lasker Award, Medal of Freedom, and Congressional Gold Medal.
Michel Haïssaguerre
Michel Haïssaguerre, French cardiologist born 1955 in Bayonne; Bordeaux electrophysiologist who discovered pulmonary vein triggers of atrial fibrillation, pioneered pulmonary vein isolation, and identified Purkinje triggers of ventricular fibrillation.
Microangiopathy
Microangiopathy: disease of small blood vessels (arterioles, capillaries, venules). Covers diabetic microangiopathy (retinopathy, nephropathy, neuropathy) and thrombotic microangiopathy (TTP, HUS), plus cerebral small-vessel disease.
Microcephaly
Microcephaly: head circumference more than 2 SD below the mean for age and sex, from genetic, infectious (TORCH, Zika), or environmental causes; no cure, supportive therapy only.
Microelectrode array
A microelectrode array (MEA), or multielectrode array, is a device with many microelectrodes on one substrate that record or stimulate neurons, in cell cultures or implanted in living tissue.
Microglia
Microglia are the resident macrophages and innate immune cells of the CNS parenchyma, discovered by Pío del Río-Hortega in 1918, of yolk sac origin, about 10–15% of glial cells, with diverse disease-associated states beyond the obsolete M1/M2 scheme.
Microtia
Microtia is a congenital underdevelopment of the external ear, ranging from a small malformed auricle to anotia; about 1 in 3,800 US births, usually unilateral, treated by rib cartilage or porous polyethylene reconstruction and bone conduction hearing devices.
Midbrain
Midbrain (mesencephalon): the rostral brainstem segment between diencephalon and pons, divided into tectum and tegmentum, containing the substantia nigra, VTA, colliculi, and cerebral aqueduct; central to Parkinson's disease research and organoid models.
Middle cerebral artery
Middle cerebral artery (MCA), arteria cerebri media: major brain artery from the internal carotid supplying the lateral hemisphere; four segments M1–M4, lenticulostriate perforators, and the most common site of ischemic stroke and cerebral aneurysms.
Middle cerebral artery syndrome
Middle cerebral artery syndrome: deficits from occlusion of the MCA, the most common stroke site (50.8% of rehab cohort). Causes contralateral weakness, aphasia or neglect; proximal occlusion has 87% poor outcome untreated; treated by thrombolysis and thrombectomy.
Middle ear
The middle ear (tympanic cavity) is the air-filled space behind the eardrum holding the malleus, incus, and stapes, which transmit and amplify sound to the inner ear, ventilated by the eustachian tube.
Middle ear neuroendocrine tumor
Middle ear neuroendocrine tumor (MeNET), formerly called middle ear adenoma, is a rare tumor of the middle ear causing hearing loss and tinnitus, treated by surgical excision.
Middle Ear Ventilation
Middle ear ventilation, also called tympanostomy or grommet insertion, treats glue ear by inserting tiny tubes through the eardrum to drain fluid and let air in.
Middle meningeal artery
Middle meningeal artery (MMA), arteria meningea media: maxillary artery branch entering via foramen spinosum to supply most of the cranial dura; ruptures at pterion cause epidural hematoma and it is embolized for chronic subdural hematoma.
Mills syndrome
Mills syndrome is a rare, acquired motor neuron disease marked by slowly progressive spastic hemiparesis on one side of the body with no sensory loss, first described in 1900.
Milrinone
Milrinone, formerly sold as Primacor, is a type III phosphodiesterase inhibitor given by intravenous infusion to treat severe heart failure and low cardiac output, including as a bridge to heart transplantation.
Mind uploading
Mind uploading, also called whole brain emulation, is a proposed process for copying a person's memories, personality, and mental attributes from their biological brain onto a computer.
Minimally conscious state
Minimally conscious state (MCS), ICD-11 8E22, is a disorder of consciousness after severe brain injury with definite but inconsistent signs of awareness, defined by 2002 Aspen Workgroup criteria, assessed with the CRS-R, and prone to about 40% misdiagnosis.
Minimally conscious state minus
Minimally conscious state minus (MCS−, ICD-11 8E22.1) is a disorder-of-consciousness subtype with non-language signs of awareness such as visual pursuit or object manipulation, but no command following or language function; proposed 2011, worse prognosis than MCS+.
Minimally conscious state plus
Minimally conscious state plus (MCS+, ICD-11 8E22.0) is a subdivision of the minimally conscious state defined by preserved language behaviors such as command following, intelligible verbalization, or intentional communication, distinguishing it from MCS minus and predicting faster emergence.
Minimally invasive direct coronary artery bypass surgery
MIDCAB: minimally invasive direct coronary artery bypass, LIMA-to-LAD graft via left mini-thoracotomy without sternotomy or bypass, introduced mid-1990s, for isolated LAD disease and hybrid revascularization.
Minimaze procedure
The minimaze procedures, also written mini maze, are minimally invasive cardiac operations intended to cure atrial fibrillation, created through small chest incisions without sternotomy or bypass.