2 letters:
az, cd, ct, em, gd, hb, ki, pm, qi, ra, rf, tb

3 letters:
act, ass, bar, bed, bod, bot, bow, bum, can, cat, chi, dip, don, egg, fat, gee, gsr, hip, ice, kip, law, lit, mao, mar, mut, pit, pku, sea, set, sun, trm, tub, vas, wbc

4 letters:
able, arse, axis, axon, back, ball, band, bank, bath, beat, belt, boar, bump, buns, buss, butt, cape, chub, clay, coat, coil, crab, crew, curl, cyst, dace, drag, duck, eggs, epos, fall, feel, flab, flap, form, full, g-jo, gain, gang, give, glow, goby, grip, hair, harm, head, hide, hull, hurt, jury, kiss, lake, land, lave, left, lens, lien, lock, lute, mach, main, mass, mime, mola, moth, neck, ness, pack, pass, pelt, pick, pool, port, post, prat, pump, pyre, rank, rear, rest, ride, rtlt, rule, rump, sail, salp, sari, seat, sell, shot, side, size, skin, slug, snap, soma, star, sumo, tail, talc, text, trim, tube, tush, uvea, vest, void, vole, vote, warm, wash, wasp, wave, wear, work, year, ymir, yoga

5 letters:
axone, banjo, barge, bathe, belly, blade, bleed, block, boned, brass, break, briny, build, bunch, burke, bursa, busty, buxom, canon, caput, carry, cavum, chest, class, clean, cling, close, comet, corps, crawl, cream, creed, creep, crowd, culex, curvy, cutis, decay, delta, drain, drape, drink, egest, eject, empty, epoch, expel, fanny, ferry, fever, field, flesh, flood, frail, frame, fruit, girth, gland, grade, graft, graze, heart, humor, inlet, inner, juice, knead, lemna, local, mouth, mucin, mucus, mummy, nates, nerve, ocean, orbit, order, outer, ovule, palsy, patch, pavis, phase, pieta, pinch, plate, point, polyp, probe, purge, quick, right, rings, rubor, salpa, saree, scale, scaly, sever, shade, shaft, shake, shape, shave, sheet, shirt, shock, shore, shunt, sinus, skink, snare, sonsy, sound, spore, squid, staff, state, stent, stern, stiff, stoma, stone, stoop, tabes, tapir, taxis, thill, torah, torso, touch, tract, trunk, tunic, ulama, ulema, upset, varus, vigor, vital, wagon, waist, whale, whole, zombi

6 letters:
abduct, abseil, accept, action, adduct, aecium, annals, artery, assume, astral, atrial, banded, behind, biopsy, biotin, bodied, bodily, bosomy, bottom, bowing, cancer, candle, carnal, caudal, cavity, cervix, charge, chorea, chorus, church, codify, coffin, colony, cootie, corpse, crouch, cuttle, cyborg, defect, deform, deluge, dibbuk, digest, distal, dorsum, douche, dragon, dredge, dybbuk, egress, embalm, estate, expose, extend, fathom, fiddle, figure, fixing, fusion, gospel, grouse, health, hoenir, huitre, humour, impact, infuse, injury, intake, karate, lagoon, laguna, lagune, lather, limbus, limply, lobata, maimed, masora, matrix, meatus, medusa, member, mesial, mucosa, mullet, muscle, mutton, nation, nekton, nervus, occult, octant, oyster, pastel, pavise, pectus, pelage, people, person, pickup, pigeon, pineal, plaque, plenum, public, puddle, puffer, puppet, purana, pushup, put on, rappel, recess, reflux, reject, remora, riddle, rising, sarong, scaled, scaley, school, seated, sector, serine, serosa, shiner, shower, slater, somite, sonsie, sphinx, spider, spinal, spleen, splint, sponge, sticky, strain, stream, stress, stroke, succus, sunken, system, tampon, tantra, thorax, ticker, tickle, tights, tracer, trauma, tunica, typhus, unguis, uptake, valgus, venter, vessel, vigour, violin, viscus, waggon, wander, wasted, weaken, wearer, weasel, wivern, wyvern, zombie

7 letters:
abdomen, abortus, aliment, anatomy, anguish, apanage, arteria, atresia, attract, autopsy, azimuth, bandage, batfish, bathing, bathtub, bearing, benthal, benthic, bivalve, blemish, blessed, boxfish, cachexy, cadaver, candela, cannula, capsule, capture, carcase, carcass, carrion, caspian, centrum, channel, charged, chassis, chimera, ciliary, cleanse, closure, cloture, college, commune, corslet, council, country, cuirass, curl up, cuticle, cyclops, daphnia, deterge, dilator, discerp, display, distend, draw in, draw up, dualism, eccrine, echelon, eclipse, empyema, enation, energid, epilate, excreta, excrete, faculty, fistula, flannel, fleshly, flowage, frailty, g-force, general, gesture, gravity, griffin, gryphon, gudgeon, guereza, habitus, hansard, harness, harvest, healing, healthy, history, ice bag, imaging, incline, inertia, ingesta, ingress, jacuzzi, jet lag, keister, lateral, leaders, leotard, leprosy, liturgy, locally, massage, midline, militia, mollusc, mollusk, mortify, mummify, myiasis, octopus, outpost, palpate, passage, perfuse, perturb, phalanx, poacher, pochard, posture, pyrexia, pyrogen, radical, rattail, rebirth, recline, redhead, redness, release, remains, rigidly, rounded, rubbing, sapless, scincid, section, sensual, setting, shiatsu, singlet, sitting, snapper, somatic, sow bug, statute, stomach, stretch, stypsis, styptic, succuss, suction, sunfish, surgery, sweater, sweeper, syringe, tension, thallus, tooshie, topical, torpedo, toucher, tractor, transit, uncover, unitard, unitize, upstart, urinary, ventral, vesture, warming, warm up, washrag, wasting, watcher

8 letters:
abducent, ablation, acidosis, activity, adducent, adenosis, air mass, alderman, alluvion, anatomic, anteater, anterior, antibody, apoapsis, appanage, ascidian, ascocarp, asynergy, athletic, attitude, autosome, autotomy, avulsion, backside, bareness, blastema, blocking, blowfish, bodiless, bodywork, body bag, bow down, brooding, buttocks, cachexia, calculus, canonist, carriage, caseworm, catheter, caudally, centesis, cestidae, chartism, chimaera, clothing, codified, compress, contempt, corporal, corselet, cosmetic, crawling, creeping, cremains, crossing, cryonics, cuticula, database, debility, dendrite, depilate, derriere, diaspora, diplegia, docetism, doliolum, dressage, dulcimer, emersion, emission, enlarged, evacuate, excision, executed, extensor, ferritin, fixation, flatfish, flatworm, friction, fuselage, gag rule, get down, get into, glycogen, governed, hairtail, halfbeak, harmonic, headfish, headlock, heavenly, hinduism, hind end, hookworm, hysteric, ice pack, incision, inoculum, invasion, invasive, ischemia, lace bug, latitude, leanness, lifeless, lungfish, mantiger, massager, metamere, midplane, milliped, minotaur, momentum, muscular, musculus, mushroom, myriapod, necropsy, nematode, nucleole, numbfish, numbness, oliguria, organism, osculate, ostracod, pangolin, parazoan, particle, peduncle, personal, phthisis, physical, physique, pill bug, pinniped, pipefish, podetium, position, pregnant, press-up, prolapse, prorogue, puffball, reaction, reappear, rear end, reformed, reptilia, republic, rub down, rudiment, scissors, sea bass, sea hare, sea lily, sea slug, secretor, shake up, shoulder, skeleton, soreness, soundbox, stenosed, stenotic, stigmata, stonefly, sunbathe, tail end, tegument, thinness, topology, torulose, touching, traction, tunicate, unbodied, unformed, urochord, vegetate, victuals, vivisect, vocation, waterway, wet suit

9 letters:
abducting, abduction, acervulus, adducting, adduction, adductive, alkalosis, apparatus, appendage, armadillo, arthropod, articular, ascension, asynergia, athetosis, atrophied, autogenic, backwater, balalaika, barracuda, benthonic, bilharzia, bloodworm, bob under, bodypaint, branchial, butterfly, canon law, cartwheel, catharsis, cellulite, centipede, citizenry, civil law, cleansing, coalition, coelostat, colostomy, community, corporeal, corticoid, cosmetics, crampfish, cremation, crocodile, crosshead, cubitiere, culminate, cup morel, dead body, deformity, democracy, depressor, devilfish, diathermy, digestion, diplopoda, discharge, disembody, dismember, dominance, dumb show, dyscrasia, ectomorph, ectoplasm, ectotherm, eliminate, enactment, endomorph, endoscopy, enhancive, epidermis, excrement, excretion, expelling, extremity, febricity, febrifuge, ferryboat, fetichism, fetishism, firedrake, frailness, fundament, funiculus, galvanism, gemmation, globefish, goldfinch, grand mal, grenadier, healthful, hierarchy, hindooism, hydrocele, hyperemia, hypertext, immersion, immunogen, inanimate, incarnate, inclusion, incurvate, infection, infirmity, ingestion, injection, innervate, inoculant, intrinsic, introduce, invisibly, irritated, ischaemia, jackknife, katharsis, laterally, lean back, left hand, leucocyte, leukocyte, limber up, lipidosis, live body, lobectomy, loch ness, loosen up, male body, manticora, manticore, medullary, mesomorph, metameric, millepede, millipede, moldering, mutilated, myriapoda, mythology, notochord, nucleolus, nutriment, nutrition, obeisance, operation, operculum, overthrow, palpation, pantomime, paralysis, pelecypod, peninsula, periapsis, personify, pirouette, placoderm, poriferan, posterior, presidium, pudginess, puppy fat, purgation, quickener, razorback, rearguard, rest mass, reticulum, roundworm, salt flat, sartorius, satellite, sea mouse, sea poker, segmental, segmented, segregate, shadiness, shellfish, snipefish, spasmodic, spiritual, stigmatic, stone fly, stretched, structure, submerged, tamponade, tenseness, titillate, topically, top brass, translate, transport, traumatic, trunkfish, tubbiness, uncharged, underbody, underpart, unhealthy, uropygium, varicella, vellicate, vicarious, vitamin e, vitamin h, waistline, war paint, washcloth, watermark, waterside, wholesome, wild boar, woodlouse

10 letters:
absorption, adult body, adventitia, anatomical, antiseptic, arthromere, articulary, assumption, astringent, atmosphere, autogenous, autoimmune, autoplasty, autotomize, backhanded, baffin bay, bald eagle, bee killer, bionic man, black body, blood heat, bluebottle, blue shark, body-build, body armor, body count, body fluid, body louse, body waste, butterfish, canulation, cataphract, cellulitis, chickenpox, choanocyte, chromosome, chubbiness, concretion, congestion, consistory, crab louse, crustacean, curvaceous, cuttlefish, decomposed, dehiscence, dehydrated, derivation, diminished, discomfort, elasticity, electorate, embalmment, enrollment, epimorphic, epithelium, face cloth, feebleness, filariasis, foundation, frost fish, generalise, generalize, glomerulus, glove doll, glycolysis, governance, guitarfish, harvestman, head louse, hematocele, hemiplegia, hemiplegic, hemoglobin, hemorrhage, heterology, heterotaxy, horny frog, hour angle, human body, hyperaemia, hysterical, immunology, incubation, indian red, intubation, inundation, inwardness, irrigation, irritation, kick start, laterality, lay figure, leadership, left brain, levitation, literature, lycoperdon, lymantriid, man's body, mantichora, membership, metastasis, mutilation, needlefish, neural net, nudibranch, opposition, paraplegia, paraplegic, percussion, phocomelia, pig's ears, pinnatiped, pleximeter, postmortem, praesidium, precession, priesthood, pro-choice, profession, prosthesis, prostitute, protoplast, puff adder, regenerate, report out, republican, resorption, ribbonfish, right hand, robber fly, salubrious, sclerotium, seal limbs, sea squirt, settlement, shed blood, sidewinder, side horse, sipunculid, slice into, slow virus, sonography, stigmatist, strengthen, stromateid, succussion, suckerfish, sustenance, sus scrofa, tapotement, tocopherol, tomography, transplant, ultrasound, underbelly, underpants, undershirt, unembodied, unicameral, university, velvet ant, voluptuous, vorticella, vulnerable, waterfront, water flea, water line, white cell, wraparound, yellowbird

11 letters:
able-bodied, ablutionary, acupressure, amphisbaena, antipyretic, archipelago, arthrospore, assimilable, astringency, autoerotism, basidiocarp, bath powder, beach wagon, black morel, body armour, body length, body weight, bombardment, break dance, burmese cat, businessmen, calefacient, cancer body, cannulation, canopic jar, cardiograph, caspian sea, catheterize, centrarchid, chorus line, christendom, circumpolar, classically, coalescence, coalescency, coelenteron, collar cell, conditioner, conic morel, consumption, convictfish, culmination, cutlassfish, cutting out, derangement, disembodied, disfunction, disgustedly, dysfunction, ectothermic, electrolyte, endothelium, excrescence, exteriorize, extirpation, female body, field mouse, fluoroscopy, fomentation, force field, generalised, generalized, genus culex, genus lemna, gray mullet, greenbottle, haemoglobin, half-length, hand puppet, hemopoiesis, holothurian, homothermic, horned toad, human waste, hyperthermy, hypertrophy, hypothermia, ichthyosaur, immigration, innervation, inoculating, intra vires, ipsilateral, iron maiden, ketone body, kinesthesia, kinesthesis, leaf insect, legislation, lipomatosis, lumbar vein, mach number, marsh buggy, martial law, mesomorphic, mesothelium, metastasize, muscle cell, natural law, noninvasive, nourishment, occultation, oligochaete, ostracoderm, outwardness, oxygen debt, peanut worm, pentecostal, pet scanner, plecopteran, prorogation, prosthetics, prostration, pubic louse, pullulation, recognition, red snapper, reincarnate, res publica, right brain, scarlet cup, sea poacher, seed shrimp, shadowiness, shapeliness, somesthesia, somesthesis, sponge bath, statute law, stethoscope, stretch out, sun bathing, superficies, swamp buggy, sympathetic, temperature, thermograph, tiger shark, ultra vires, unsegmented, urochordate, vaccinating, visual area, vortex vein, watercourse, water level

12 letters:
absorptivity, acetone body, alimentation, aplacophoran, assimilation, auscultation, autoimmunity, ballottement, banded gecko, beach waggon, bellows fish, bilharziasis, bionic woman, bloodsucking, bodily fluid, body english, body politic, body process, canopic vase, cantharellus, canulization, carpet shark, chest cavity, child's body, chiropractic, christianity, city council, coat of mail, cold-blooded, comfort zone, commonwealth, common louse, constituency, constriction, criminal law, crossheading, deliberative, discomycetes, discorporate, dorsiflexion, edible fruit, electric eel, electric ray, excitability, exenteration, exteroceptor, fairy shrimp, fatty tissue, feverishness, flying gecko, free radical, full-bosomed, funeral pyre, gluteal vein, heart urchin, hemodialyzer, heterogenous, hindquarters, holocephalan, homeothermic, hygienically, hyperthermia, hypogonadism, implantation, inflammation, infundibulum, insemination, inspectorate, insufflation, interference, interoceptor, irritability, jelly fungus, kick starter, kinaesthesia, kinaesthesis, kinesthetics, labanotation, law merchant, localisation, localization, malformation, mare clausum, mare liberum, maritime law, military law, morphallaxis, moving ridge, muscle-bound, muscle fiber, muscle fibre, muscle sense, nonsegmental, normothermia, nudibranchia, orbit period, order lobata, organisation, organization, parathormone, pars nervosa, pascal's law, phaneromania, pickup truck, platyctenean, poikilotherm, pommel horse, rattail fish, reabsorption, red goatfish, registration, retroflexion, retroversion, rolypoliness, scorpionfish, sea cucumber, sea scorpion, semidiameter, skye terrier, solenogaster, somaesthesia, somaesthesis, statute book, stick figure, stinky squid, straitjacket, stridulation, sucking fish, talking head, thermography, transmigrate, triglyceride, tuberculosis, tussock moth, typhus fever, vena gluteus, walking leaf, warm-blooded, water beetle, well-endowed, white plague, woman's body, zombi spirit

13 letters:
abramis brama, admiralty law, animal starch, anthropometry, auditory area, autoeroticism, aythya ferina, bodily cavity, body covering, body language, bottom feeder, break dancing, bring outside, cannulization, ciliary veins, contact sport, contralateral, elephantiasis, establishment, exteroception, flying dragon, flying lizard, fringed gecko, full radiator, galiella rufa, genus discina, gland disease, gross anatomy, helminthiasis, hematogenesis, hematopoiesis, heterogeneous, heterostracan, heterothermic, homoiothermic, horned lizard, hot-water bag, hypertrophied, immune system, incandescence, incorporation, inertial mass, interoception, iridocyclitis, juvenile body, lamellibranch, material body, mean distance, micronutrient, military post, misshapenness, mummification, mussel shrimp, mutton tallow, ocean sunfish, orbital plane, ovoviviparous, oxyhemoglobin, parliamentary, pecking order, phenylalanine, physical body, plant process, platyhelminth, plectomycetes, porcupinefish, proprioceptor, pyrenomycetes, radius vector, rank and file, razorback hog, real presence, referred pain, refrigeration, retroflection, rickettsiosis, scorpion fish, slice through, somatesthesia, somatic sense, station wagon, statutory law, strangulation, stretched out, student union, suit of armor, swimming hole, toilet powder, total eclipse, trace element, transposition, true puffball, uncomfortably, undercarriage, unwarrantably, vena lumbalis, visual cortex, zombie spirit

14 letters:
adipose tissue, administration, american eagle, antiadrenergic, apocrine gland, bitis arietans, bodily process, body substance, brain mushroom, center of mass, cestum veneris, class reptilia, closed session, commercial law, conglutination, coriolis force, corpus delicti, corticosteroid, corticosterone, curvaceousness, daddy longlegs, diodon hystrix, dusting powder, elastic energy, electric shock, erogenous zone, european bream, external organ, field of force, flying opossum, full-fashioned, genus spadella, governing body, gravity-assist, haematopoiesis, hermaphroditus, immobilisation, immobilization, inclusion body, internal organ, kinetic energy, law of nations, mercantile law, metempsychosis, mullus auratus, neural network, pentecostalist, plethysmograph, poikilothermic, porcupine fish, pressure point, proprioception, red-eyed vireo, representation, rules of order, russell's body, sacred college, salt depletion, sanguification, scaly anteater, scincid lizard, sea gooseberry, securities law, sensory system, solitary vireo, specialisation, specialization, spinus tristis, star earthball, states general, station waggon, straightjacket, suit of armour, test-tube baby, tonic epilepsy, transmigration, venae ciliares, venus's girdle, voluptuousness, vorticose vein, weight gaining

15 letters:
active immunity, adenohypophysis, adult male body, annual parallax, armored catfish, astringent drug, auditory cortex, ballet position, beefsteak morel, bodily function, bodily property, church doctrine, class diplopoda, class myriapoda, colobus guereza, common mackerel, contour feather, coriolis effect, depressor nerve, differentiation, elastic modulus, electric charge, epilepsia major, extensor muscle, family cestidae, flying squirrel, fully fashioned, genus treponema, great salt lake, greenbottle fly, heat exhaustion, horny structure, incompatibility, judicial review, left hemisphere, legal community, legislative act, lepiota naucina, life-sustaining, malignant tumor, mucous membrane, neurohypophysis, old world quail, partial eclipse, phenylketonuria, phthirius pubis, pinniped mammal, plastic surgeon, poikilothermous, power structure, prionace glauca, razorbacked hog, right ascension, schistosomiasis, secretory organ, serous membrane, skeletal system, skirt of tasses, somatatesthesis, standard candle, stromateid fish, the living dead, thoracic cavity, ultrasonography, unknown soldier, vascularization, vascular system, vascular tissue, vena vorticosum, wasting disease, white corpuscle

16 letters:
angular momentum, aplysia punctata, armored searobin, astreus pteridis, aythya americana, basal metabolism, body temperature, cosmetic surgeon, crystalline lens, digestive system, diplomatic corps, disciotis venosa, diurnal parallax, drag coefficient, electrical shock, flying phalanger, genus lycoperdon, genus paramecium, genus vorticella, glans clitoridis, graduating class, great blue shark, ground substance, hansen's disease, heat prostration, hookworm disease, hot-water bottle, hyperventilation, immunodeficiency, legal profession, local anesthesia, local anesthetic, lymphatic system, metastatic tumor, morchella conica, mucous secretion, narrowhead morel, nitrogen balance, nuclear medicine, oligochaete worm, oxylebius pictus, pharmacokinetics, potential energy, religious school, reporting weight, right hemisphere, sartorius muscle, scomber scombrus, somatic delusion, substantia nigra, tension headache, transubstantiate, vireo olivaceous, vireo solitarius, white blood cell

17 letters:
absorption factor, acid-base balance, adhesive friction, adult female body, armored sea robin, artificial kidney, calliphora vicina, carcinoma in situ, centrifugal force, centripetal force, common iliac vein, consubstantiation, crotalus cerastes, date of reference, developmental age, electoral college, epithelial tissue, excretory product, executive session, glandular disease, graafian follicle, health profession, holistic medicine, immunosuppressant, immunosuppression, immunosuppressive, international law, local anaesthesia, local anaesthetic, medical community, moment of inertia, monoamine oxidase, painted greenling, parliamentary law, pediculus capitis, pediculus humanus, peziza domicilina, phalangium opilio, point of apoapsis, prosthetic device, pterygoid process, relativistic mass, respiratory tract, sense of movement, spinal anesthesia, terminal velocity, transmission time, tremella foliacea

18 letters:
administrative law, anterior pituitary, bird's-nest fungus, blarina brevicauda, blue point siamese, business community, circulatory system, corps diplomatique, diplomatic service, discina macrospora, ecclesiastical law, external body part, foundation garment, galeocerdo cuvieri, general anesthetic, genus cantharellus, glandular disorder, gravitational mass, heart-lung machine, horned rattlesnake, hypogastric artery, interstitial fluid, laying on of hands, leuciscus cephalus, malignant neoplasm, medical profession, metabolic acidosis, musculus sartorius, newton's first law, occupational group, order nudibranchia, pediculus corporis, physical education, point of periapsis, preinvasive cancer, religious doctrine, short-tailed shrew, somatic chromosome, spinal anaesthesia, steering committee, surgical operation, surgical procedure, temperature change, topical anesthetic, transit instrument, transubstantiation

19 letters:
articulatory system, ballistocardiograph, blackbody radiation, calostoma lutescens, calostoma ravenelii, celestial longitude, chrysophrys auratus, circulatory failure, class plectomycetes, class pyrenomycetes, coefficient of drag, computed tomography, elasticity of shear, estate of the realm, extracellular fluid, feeling of movement, first law of motion, generalized seizure, general anaesthetic, geocentric parallax, gravitational field, gyromitra esculenta, helvella acetabulum, horizontal parallax, hyperparathyroidism, jacksonian epilepsy, lepromatous leprosy, leuciscus leuciscus, long saphenous vein, lutjanus blackfordi, macroscopic anatomy, monoclonal antibody, new world goldfinch, parathyroid hormone, physiological state, posterior pituitary, regional anesthesia, reticular formation, rickettsial disease, subthalamic nucleus, tactual exploration, topical anaesthetic, tourette's syndrome, tremella reticulata

20 letters:
acanthosis nigricans, chartered accountant, cinnabar chanterelle, clinical thermometer, economics profession, floccose chanterelle, great saphenous vein, miliary tuberculosis, orectolobus barbatus, peristedion miniatum, regional anaesthesia, sarcoscypha coccinea, solid body substance, somatosensory system, systemic circulation

21 letters:
acid-base equilibrium, albatrellus dispansus, archimedes' principle, calostoma cinnabarina, cantharellus clavatus, cardiovascular system, community of scholars, external iliac artery, heliocentric parallax, internal iliac artery, liquid body substance, modulus of elasticity, morchella angusticeps, round-trip light time, scleroderma flavidium, subclass discomycetes, tube-shaped structure, white blood corpuscle

22 letters:
anterior cardinal vein, basal body temperature, cantharellus floccosus, electrophorus electric, fetal alcohol syndrome, galvanic skin response, genetic fingerprinting, glucose tolerance test, gymnopilus spectabilis, immunosuppressive drug, kinetic theory of heat, malignant hyperthermia, musculoskeletal system, physiological property, postmortem examination, pseudocolus fusiformis, pulmonary tuberculosis, somatic sensory system

23 letters:
cartilaginous structure, computerized tomography, gastrointestinal system, intercellular substance, parliamentary procedure, posterior cardinal vein, saddle block anesthesia, secondary sex character, truncocolumella citrina

24 letters:
anterior pituitary gland, elastic potential energy, haliaeetus leucocephalus, saddle block anaesthesia

25 letters:
cantharellus cinnabarinus, coefficient of elasticity, computed axial tomography, posterior pituitary gland, ptychozoon homalocephalum

28 letters:
newton's first law of motion, secondary sex characteristic, second law of thermodynamics, zeroth law of thermodynamics

29 letters:
computerized axial tomography

30 letters:
gilles de la tourette syndrome

36 letters:
positron emission tomography scanner