72,234 articles
Human body
Human body: the physical structure of a human organism, studied via anatomy and physiology. Six levels of organization, eleven organ systems, homeostatic control, tens of trillions of cells, and modern cell atlas projects like HuBMAP and the Human Cell Atlas.
Human body weight
Human body weight is the total mass of the body, including muscle, bone, fat, and water. Assessed via BMI (weight/height²), waist circumference, and body composition; obesity at BMI 30+, malnutrition at BMI under 18.5 or 10% unintentional loss.
Human brain
Human brain: the three-pound central organ of the human nervous system, with about 100 billion nerve cells, an 80-percent-of-volume cortex, a restrictive blood-brain barrier, and a threefold size increase over two million years of hominin evolution.
Human brain mapping
Human brain mapping: measuring and charting human brain structure and function with PET, fMRI, EEG, MEG, and related methods; also a Wiley neuroimaging journal founded in 1993.
Human Brain Project
The Human Brain Project was Europe's largest brain research initiative, running from 2013 to 2023 with a goal of simulating the human brain on a supercomputer.
Human challenge study
A human challenge study, also called a controlled human infection study, deliberately infects volunteers with a known pathogen dose to test vaccines and treatments quickly.
Human chorionic gonadotropin
Human chorionic gonadotropin (hCG), the pregnancy hormone, is a placental glycoprotein with alpha and beta subunits that maintains the corpus luteum, marks trophoblastic and some other tumors, and anchors all pregnancy testing.
Human cloning
Human cloning: SCNT-based copying of humans, split into reproductive and therapeutic aims. No human has been cloned; Dolly (1996) proved the method, but low efficiency, epigenetic failures, and bans keep human cloning unrealized.
Human coronavirus 229E
Human coronavirus 229E (HCoV-229E) is an alphacoronavirus that causes common colds; recovered in 1966 at the University of Chicago, it accounts for 15–30% of adult colds.
Human coronavirus HKU1
Human coronavirus HKU1 (HCoV-HKU1) is one of the four seasonal human coronaviruses circulating worldwide, discovered in Hong Kong in 2005, causing typically mild winter respiratory illness and sometimes pneumonia.
Human coronavirus NL63
Human coronavirus NL63 (HCoV-NL63), an alphacoronavirus discovered in the Netherlands in 2004, is one of four endemic human coronaviruses; it uses the ACE2 receptor, diverged from HCoV-229E in the 11th century, and is linked to croup in children.
Human coronavirus OC43
Human coronavirus OC43 (HCoV-OC43) is a betacoronavirus, Embecovirus, first isolated in 1967; one of four seasonal common-cold coronaviruses using 9-O-acetylated sialic acid receptors, likely emerging from bovine coronavirus around 1890, and neurotropic in humans.
Human digestive system
Human digestive system: GI tract (mouth, esophagus, stomach, small and large intestines, anus) plus liver, pancreas, gallbladder; breaks food into amino acids, fatty acids, sugars; peristalsis, hormones, gut bacteria.
Human echolocation
Human echolocation: using reflected sound, especially self-generated mouth clicks, to sense silent objects. Practiced by some blind people and trainable by sighted people; term coined 1944; 10-week training studies show broad learning.
Human ecology
Human ecology is the interdisciplinary study of relationships between humans and their environments, arising in the early 1900s from biology, anthropology, and sociology; known for the Chicago School, the POET model, and sustainability research.
Human embryonic development
Human embryonic development: fertilization to end of week 8, 23 Carnegie stages, implantation about day 6, gastrulation day 14, organogenesis days 21–57; distinct from fetal period and from clinical gestational dating.
Human evolution
Human evolution: the roughly six-million-year process by which Homo sapiens arose from apelike ancestors in Africa, studied through fossils, archaeology, and genetics; key traits include bipedalism over 4 Ma, toolmaking, and recent interbreeding with Neanderthals and Denisovans.
Human eye
The human eye is the paired sensory organ that focuses light onto the retina, converting it into electrical signals sent through the optic nerve to the brain.
Human factors
Human factors (human factors and ergonomics, HFE) is the science of designing systems around human capabilities and limitations. It emerged in World War II; HFES was founded in 1957 and publishes the journal Human Factors (1958).
Human feces
Human feces (stool): bowel waste, 75% water, formed as the colon absorbs ~90% of 1.5–2 L daily ileal effluent; classified by the Bristol Stool Chart, used in stool tests, FMT products, and sanitation.
Human fertilization
Human fertilization is the fusion of sperm and egg forming a diploid zygote, via zona pellucida binding, IZUMO1-JUNO adhesion, PLCζ calcium oscillations, and polyspermy blocks, in vivo or by IVF.
Human genetic enhancement
Human genetic enhancement is genome editing to improve capacities beyond the normal range, distinct from therapy. Also called germline enhancement or designer babies; regulators restrict trials to treatment and prevention of disease.
Human genetic variation
Human genetic variation: DNA sequence differences among people and populations. Genomes are ~99.6% identical; typical genome has ~5 million SNVs, ~600,000 indels, ~25,000 structural variants; cataloged by 1000 Genomes and pangenome projects.
Human genetics
Human genetics: the study of inherited variation in humans, spanning molecular, clinical, population, and statistical genetics. Distinguished from Medical Genetics (MeSH) and from the Springer journal Human Genetics (ISSN 0340-6717, founded 1964 as Humangenetik).
Human genome
Human genome: the complete human DNA instruction set, about 3 billion base pairs in 46 chromosomes with 20,000–25,000 genes; sequenced by the Human Genome Project (1990–2003, 92%) and fully completed by the T2T consortium in 2022.
Human Genome Project
Human Genome Project (HGP): international 1990-2003 effort led by NIH's NHGRI and DOE to sequence the 3-billion-letter human genome for $2.7 billion, with Bermuda Principles open data and ELSI ethics research; completed ahead of schedule, later completed gaplessly by T2T in 2022.
Human genomics
Human genomics studies the human genome's sequence, variation, and function, from the 1990 Human Genome Project and 2003 draft (15% incomplete) to next-generation and long-read sequencing, 41 national genome projects, precision medicine, and equity challenges.
Human hair color
Human hair color is produced by two melanin pigments, eumelanin and pheomelanin, whose quantity and ratio make hair appear black, brown, blond, red, or gray.
Human hair growth
Human hair growth: the cyclical production of keratin fibers by hair follicles through anagen, catagen, telogen, and exogen phases. Scalp hair grows about 0.35 mm/day; anagen is roughly 90% of the cycle; androgens, DHT, minoxidil, and finasteride regulate it.
Human head
Human head: uppermost body region containing the brain, sensory organs, and the 22-bone skull (cranium), divided into neurocranium and viscerocranium; covers anatomy, development, variation, and head injury.