72,234 articles
Human resources for health
Human resources for health (HRH), also called the health workforce, is the stock of people engaged in protecting and improving health, a core building block of health systems.
Human serum albumin
Human serum albumin (HSA, ALB), the most abundant plasma protein (66 kDa, ~600 μM), maintains oncotic pressure, carries fatty acids, bilirubin, and drugs at Sudlow sites I and II, and is given intravenously for volume expansion.
Human sex pheromones
Human sex pheromones, also called putative human pheromones (androstenone, androstenol, androstadienone, estratetraenol), are claimed chemical sexual signals between humans; no bioassay-led evidence supports any candidate, and the human vomeronasal organ is nonfunctional.
Human skeleton
Human skeleton: the body's bony framework, 206 named adult bones in axial (80) and appendicular (126) divisions, about 270 at birth, with support, protection, movement, blood cell production, and mineral storage functions.
Human skin
Human skin, the body's largest organ (about 6 pounds, 18 square feet), has three layers: epidermis, dermis, and hypodermis; it provides barrier, sensory, thermoregulatory, and vitamin D functions and hosts a diverse microbiome.
Human skin color
Human skin color is melanin-based pigmentation shaped by UV radiation via the vitamin D–folate hypothesis: dark equatorial skin conserves folate, depigmented high-latitude skin aids vitamin D synthesis, evolving polygenically across SLC24A5, SLC45A2, MC1R, and KITLG.
Human subject research
Human subject research: systematic investigation involving living people contributing data or samples. Governed by the 1991 U.S. Common Rule (45 CFR 46), the 1979 Belmont Report, informed consent, and IRB review; FDA regulates clinical investigations separately.
Human T-lymphotropic virus 1
HTLV-1 (human T-lymphotropic virus 1, human T-cell leukemia virus type 1) is the first discovered human retrovirus, transmitted sexually, via breastfeeding, needles, and blood, causing adult T-cell leukemia/lymphoma and HAM/TSP in 5-10% of the 5-10 million infected; no vaccine or cure exists.
Human taxonomy
Human taxonomy: the scientific classification of Homo sapiens (NCBI TaxID 9606) as Eukaryota, Animalia, Chordata, Mammalia, Primates, Hominidae, Homo; Linnaeus 1758; no recognized human subspecies; race is not a biological category.
Human thermoregulation
Human thermoregulation: maintenance of core body temperature by balancing heat generation and loss, controlled by the preoptic hypothalamus via sweating, vasodilation, and shivering.
Human threats to spiders
Human threats to spiders are the pressures people place on spider populations, chiefly habitat destruction, pesticides, climate change, collection for trade, and invasive species; as of 2021, 99.34% of spider species had no IUCN assessment.
Human tooth
Human tooth: the mineralized organ in the jaws, made of enamel, dentin, cementum, and pulp; humans have 20 primary and 32 permanent teeth, and enamel is the body's hardest, non-remodeling tissue.
Human tooth development
Human tooth development (odontogenesis) is the bud-cap-bell-root formation of teeth from oral epithelium and neural crest mesenchyme, regulated by Wnt, BMP, FGF, SHH, and EDA signaling, producing 20 deciduous and 32 permanent teeth; agenesis genes include MSX1, PAX9, WNT10A, AXIN2.
Human uses of Cladonia lichens
Cladonia lichens, the shrub-like genus including reindeer lichens, serve as reindeer forage, sources of medicinal and dye compounds, and decorative material for crafts, models, and floral arrangements.
Human uses of scorpions
Human uses of scorpions: traditional Chinese medicine (Quanxie/Scorpio, Buthus martensii), venom milking for drug research and probes, antivenom production, food in Asia, folk-medicine trade, and unproven blue scorpion cancer products.
Human vaginal size
Human vaginal size: measurable length and width of the vaginal canal, also called vaginal dimensions. MRI baselines: 62.7 mm undistended length, widths 26–33 mm, large inter-individual variation; size does not affect sexual function.
Human vestigiality
Human vestigiality is the retention in the human body of structures and behaviors that have lost some or all of their ancestral function over evolutionary time.
Human waste
Human waste (human excreta) is feces and urine from human metabolism. Distinguished by pathogen load, nutrient content (4.5 kg N per person yearly), and sanitation systems: safely managed coverage reached 58% by 2024.
Human Y-chromosome DNA haplogroup
Human Y-chromosome DNA haplogroup: a branch of the paternal-line Y chromosome tree defined by SNPs, named under the 2002 YCC system, used in genealogy, population history, and forensics, with African origin and regional frequency differences from drift.
Human–animal hybrid
Human–animal hybrid, or chimera: an organism or embryo containing cells of both human and animal origin, distinct from true gamete hybrids. Key work includes the 2021 20-day human-monkey embryo; main goal is growing transplantable human organs, mainly in pigs.
Human–canine bond
Human–canine bond: the reciprocal human–dog relationship, also called the human–dog bond. Began via commensal wolf domestication over 14,000 years ago; studied through attachment theory, oxytocin, and mixed health-benefit evidence.
Humanitarian League
Humanitarian League, British pressure group (1891–1919) founded by Henry S. Salt; distinct from the League of Nations and League Against Cruel Sports; campaigned against blood sports, vivisection, and corporal punishment on a principle of humaneness for all sentient beings.
Humanzee
The humanzee, also known as a human-chimpanzee or human-ape hybrid, is a hypothetical human-chimp hybrid; the only documented experiments, by Soviet zoologist Ilya Ivanov in the 1920s, failed.
Humberto Fernández-Morán
Humberto Fernández-Morán (1924–1999) was a Venezuelan biophysicist who invented the diamond knife, founded what is now the Venezuelan Institute for Scientific Research, and built the first electron cryomicroscope with superconducting lenses.
Humboldt squid
Humboldt squid (Dosidicus gigas), jumbo flying squid, a large eastern Pacific ommastrephid squid reaching 2 m and 50 kg, with a ~1-year life, up to 32 million eggs, hypoxia-tolerant vertical migration, and the world's largest squid fishery.
Humerus
Humerus: the single long bone of the upper arm, largest bone of the upper limb, articulating with the scapula at the shoulder and radius and ulna at the elbow; fracture-prone at the surgical neck, radial groove, and supracondylar region.
Hummingbird
Hummingbird (Trochilidae), tiny New World bird related to swifts; about 340 species, 2–20 g, the only vertebrates capable of sustained hovering, fueled by nectar and using torpor to survive nights.
Hummingbird hawk-moth
Hummingbird hawk-moth (Macroglossum stellatarum), a day-flying Eurasian sphingid moth that hovers at flowers with 70–85 Hz wingbeats and a 26 mm proboscis, mimicking hummingbirds; migrant to Britain, larvae feed on bedstraw.
Humoral immunity
Humoral immunity: the antibody-mediated arm of adaptive immunity, driven by B cells and plasma cells, protecting extracellular spaces; includes germinal center affinity maturation, five immunoglobulin classes, active versus passive immunity, and its 19th-century origins with Behring and Ehrlich.
Humorism
Humorism (humoralism, four humors): ancient Greek-Roman medical system of blood, phlegm, yellow bile, black bile; health as balance, disease as imbalance; Hippocrates, Galen, Avicenna; dominant until 19th-century germ theory; survives in Unani medicine.