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M cone cell
M cone cell (medium-wavelength-sensitive cone, OPN1MW, green cone): retinal photoreceptor peaking near 543 nm, one of three cone classes enabling human trichromatic vision; X-linked gene, deutan color blindness, olo M-only stimulation.
Macrotia
Macrotia is an abnormally large external ear, defined by ear length and width more than 2 standard deviations above age- and sex-specific means, classified as a minor anomaly of the pinna.
Macular disorders
Macular disorders (ICD-11 9B75, 黄斑障害) are diseases of the macula, the retina's central vision area. They include age-related macular degeneration, macular edema, macular hole, and inherited macular dystrophies, staged by drusen size and treated with anti-VEGF drugs.
Macular edema
Macular edema is fluid accumulation in the macula, the central retina, caused by blood-retinal barrier dysfunction in diabetes, retinal vein occlusion, uveitis, and post-cataract inflammation; treated with anti-VEGF drugs, corticosteroids, and laser.
MADIT-CRT trial
MADIT-CRT (NCT00180271): Boston Scientific-sponsored randomized trial of 1,820 NYHA I-II patients testing CRT-D versus ICD-only; primary endpoint HR 0.66, no mortality benefit, FDA approval extended to LBBB subgroup in 2010.
Madras motor neuron disease
Madras motor neuron disease (MMND) is a rare motor neuron disorder first described in 1970 in Chennai, India, with young onset, distal limb wasting, lower cranial nerve palsies, pyramidal signs, and sensorineural deafness; a variant adds optic atrophy.
Magdi Yacoub
Sir Magdi Habib Yacoub (born 16 November 1935) is an Egyptian cardiothoracic surgeon who established heart transplantation in the UK, performed Europe's first heart-lung transplant in 1983 at Harefield, founded Chain of Hope and the Aswan Heart Centre, and received the Order of Merit in 2014.
Magnetic resonance imaging of the brain
Brain MRI (head MRI) images the brain using a strong magnet, radio waves, and a computer without ionizing radiation. Field strengths of 1.5, 3, and 7 tesla; gadolinium contrast; used for stroke, tumors, and multiple sclerosis.
Magnetoencephalography
Magnetoencephalography (MEG) is a non-invasive brain imaging method recording neuromagnetic fields with SQUID or optically pumped magnetometer sensors, offering millimeter spatial and millisecond temporal resolution for epilepsy localization and presurgical mapping.
Mal de debarquement
Mal de debarquement (MdD) is the rocking or swaying self-motion sensation after passive motion like sea travel; when persistent it is mal de debarquement syndrome (MdDS), a rare female-predominant vestibular disorder with Bárány Society diagnostic criteria and optokinetic stimulation as leading treatment.
Male reproductive system
Male reproductive system: organs producing sperm and testosterone, including testes, epididymis, vas deferens, prostate, and penis; ~64-day spermatogenesis cycle, 100-300 million sperm daily, hormonal HPG-axis control.
Malleolus
Malleolus (plural malleoli): either of the two bony ankle protuberances, the medial malleolus of the distal tibia and lateral malleolus of the fibula, forming the ankle mortise; key landmarks in ankle fracture classification.
Management of acute coronary syndrome
Management of acute coronary syndrome (ACS) covers emergency care of unstable angina, NSTEMI, and STEMI. The 2025 ACC/AHA guideline sets ECG within 10 minutes, hs-cTn 1-2 h rule-out, primary PCI or fibrinolysis within 12 h, and cardiac rehabilitation referral.
Management of lymphedema
Management of lymphedema treats swelling using complete decongestive therapy, compression, skin care, and exercise, with surgery such as lymphovenous bypass reserved for patients who do not respond.
Mandible
Mandible: the largest bone of the human skull, forming the lower jaw; articulates at the temporomandibular joints, develops around Meckel's cartilage, and is a common facial fracture site.
Mandibular nerve
Mandibular nerve (CN V3, nervus mandibularis), largest trigeminal division and the only one with a motor root; exits via foramen ovale, splits into anterior and posterior divisions, supplies mastication muscles, lower teeth, tongue, and is the target of the inferior alveolar nerve block.
Manganese poisoning
Manganese poisoning, also called manganism, is a neurological condition caused by chronic inhalation of manganese dust or fumes, producing tremor, rigidity, slowed movement, and psychiatric disturbance.
Manual lymphatic drainage
Manual lymphatic drainage (MLD), Vodder method, is a light massage technique for lymphedema, a component of complete decongestive therapy; trials show no added volume reduction but possible pain and quality-of-life benefits.
Marginal zone of the spleen
Splenic marginal zone: border region between white and red pulp where SIGNR1/MARCO macrophages and rapid-response marginal zone B cells trap blood-borne pathogens; absent as a distinct compartment in humans, whose loss (asplenia) raises encapsulated-bacteria risk.
Marrow fibroblast
Marrow fibroblast (Cell Ontology CL:0002240): a fibroblast in the bone marrow, subtype of fibroblast and bone marrow stromal cell; the Friedenstein CFU-F lineage that supports hematopoiesis, forms bone, and drives marrow fibrosis.
Martin Pistorius
Martin Pistorius (born 1975, Johannesburg), author of the memoir Ghost Boy, fell into an unexplained locked-in state at age 12 in 1988; aware but unable to move or speak for about 10 years, he communicated via eye-movement computer software from 2001 and now works in assistive technology.
Martin Van Buren Bates
Martin Van Buren Bates, the Kentucky Giant (1837-1919), a 7'9" Confederate captain and circus performer who married the 7'11" giantess Anna Swan in London in 1871 and farmed in Seville, Ohio.
Martinique crinkled retinal pigment epitheliopathy
Martinique crinkled retinal pigment epitheliopathy (MCRPE, MDPT3, patterned macular dystrophy 3) is an ultra-rare autosomal dominant retinal dystrophy from MAPKAPK3 mutations, first described in Martinique, with a dry-desert-land fundus pattern, adult onset, and PCV or CNV complications.
Masseter muscle
Masseter muscle: quadrangular masticatory muscle from zygomatic arch to mandibular angle; elevates and protrudes the jaw; innervated by masseteric nerve (V3); hypertrophy from bruxism is treated with botulinum toxin.
Masters and Johnson
Masters and Johnson: William H. Masters and Virginia E. Johnson, St. Louis sex researchers who observed nearly 10,000 sexual acts, defined the four-phase sexual response cycle, and founded sex therapy.
Mastoid part of the temporal bone
Mastoid part of the temporal bone: posterior temporal bone region containing the mastoid process and mastoid air cells; pneumatizes from the petrous part, serves as a middle-ear air reservoir, and is the site of mastoiditis and mastoidectomy.
Mastoiditis
Mastoiditis is a bacterial infection of the mastoid air cells, usually complicating acute otitis media in young children. Key signs are postauricular swelling with pinna displacement; treated with IV ceftriaxone, sometimes mastoidectomy.
Maternal bond
Maternal bond: the mother's emotional connection to her child, distinct from infant attachment. Measured by tools like the Postpartum Bonding Questionnaire; rooted in oxytocin and dopamine systems; disrupted by postpartum depression.
Mauthner neuron
Mauthner neuron (Mauthner cell, M-cell): a pair of giant reticulospinal hindbrain neurons in fishes and amphibians that triggers the C-start escape response, with ~100 μm somata, segregated sensory dendrites, and mixed electrical-chemical synapses.
Maxilla
Maxilla: paired midfacial bone formed by fused right and left maxillary bones; carries upper teeth, forms orbital floor and hard palate, houses the largest paranasal sinus; key in Le Fort fractures and sinus lift implant surgery.