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A historical chemical test producing characteristic crystals from a hemoglobin derivative. It establishes neither human origin nor the donor's identity.

The hamstrings are posterior thigh muscles with important actions at the hip and knee. In the usual human grouping they include semitendinosus, semimembranosus and the long head of biceps femoris. Their multi-joint geometry links hip position to knee-flexion mechanics.

A heart valve permits predominantly one-way blood flow through the heart. Leaflet motion follows changing pressure differences and structural constraints. The four main human valves occupy different chamber or outflow boundaries, so valve dysfunction has location-specific consequences.^[ref]

A researcher who coauthored adaptive-optics imaging and densitometry of human cone mosaics. Measuring variation among individuals connected retinal sampling with trichromatic vision without assuming one fixed cone ratio for every observer.^[ref]

Human leukocyte antigen, the human MHC system. Particular HLA molecules restrict which peptides a conventional T-cell receptor can recognise.

Here is an explicitly synthetic mathematical model of a warming disturbance and its compensatory cooling. It is a teaching analogy for thermoregulation, not a measured human heat budget. Write $x=(T-T_r)/\Delta T$, where $T$ is a lumped internal temperature, $T_r$ is a fixed reference and $\Delta T>0$ is a chosen temperature scale. Let $d$ be an additional heating rate and $u$ an additional cooling rate, both scaled to the same reference rate. All three are dimensionless variables, while $\tau >0$ is a time constant in the chosen time units. The ordinary differential equation isThe term $-x$ idealizes increased passive heat transfer with increased internal temperature, around the baseline. The term $-u$ opposes warming through proportional control with feedback gain $k$. This local signed model does not treat a negative $u$ as negative sweating: it would represent decreased cooling relative to baseline. Changes of the environment and multiple body compartments are omitted.

For a constant disturbance $d=D$ and initial condition $x(0)=0$, the exponential function solution isSubstitution checks the ordinary differential equation directly. Increasing $k$ reduces the lasting offset and, in this instantaneous model, shortens the response time constant to $\tau /(1+k)$. It does not make $x_{\ast }$ zero for a nonzero disturbance and finite $k$: a persistent cooling command requires a persistent displacement under proportional control. At the equilibrium point, the extra heating is balanced by passive loss $x_{\ast }$ plus active cooling $u_{\ast }$. Zero change of temperature means balanced rates, rather than zero rates, consistent with conservation of energy.

The first diagram uses $D=1$, $\tau =4$, and a pulse from $t=2$ to $t=10$, comparing $k=0$ with $k=3$. The latter approaches $x_{\ast }=1/4$ during the pulse, compared with $1$ without active feedback control. After the pulse ends, each displacement decays as $x(10)e^{-(1+k)(t-10)/\tau }$. These are computed curves, not physiological measurements. The $k=0$ curve still has passive loss; it is not a claim that an unregulated body warms without limit.

Real physiological effectors take time to respond. To isolate that issue, set $\tau =1$ and replace the instantaneous command by another ordinary differential equation:Here the disturbance remains $1$ from $t=0$ onward and the effector time constant is also $1$. The equilibrium point is still $(x_{\ast },u_{\ast })=(1/5,4/5)$, but the characteristic polynomial is $(\lambda +1{)}^2+4$. Its eigenvalues $-1\pm 2i$ give decaying oscillations and asymptotic stability. The exact response isIn particular, $\dot{x}=e^{-t}\cos (2t)$, so the first maximum occurs at $t=\pi /4$, with $x=1/5+(2/5)e^{-\pi /4}\simeq 0.3824$. The response exceeds its eventual displacement while remaining above its baseline. The return has the same negative sign as before; the extra state changes the timing. A finite effector time constant is distinct from the fixed time lag in the delayed negative feedback model.

In the human-evolution usage adopted here, a member of the human lineage after its separation from Pan. Usage and formal tribal boundaries should be stated because classifications differ.

The living human species. Its population history includes African ancestral structure, dispersal, demographic change and genetic admixture.

The house mouse, Mus musculus, is a small rodent associated with human environments and widely used in experimental biology. Laboratory strains provide controlled inherited backgrounds, while wild populations reveal variation shaped by ecology and ancestry.

A human is a member of Homo sapiens, the living species of Homo. Our anatomy combines inherited vertebrate organization with derived features such as habitual bipedalism. Variation among individuals and populations is part of the biology of one species.

A mouse modified to contain selected human biological components, such as immune biological cells. Humanization is partial and does not automatically reproduce all human immune interactions.

A larval cyst; human hydatid cysts commonly involve the liver or lungs.

A human in the earliest postnatal period. Research reports should specify chronological age and, where relevant, gestational or corrected age; an infant sample does not establish performance across the whole period.

A species moved by humans beyond its natural geographic range. Introduction is defined relative to location, not only national boundaries.

Researcher in human evolution. Hershkovitz and collaborators investigated fossil evidence for early modern humans outside Africa, connecting anatomical identification with the chronology of dispersal.^[ref]

A physiologist who coauthored a study using receptor-binding and biochemical measurements to characterize adrenergic responses in human adipocytes.^[ref]

Coauthor of Anatomy and Physiology 2e by J. Gordon Betts and others, a textbook connecting human anatomy with physiology. Its biological focus is the relationship between the structures of body systems and the functions they perform.^[ref]

A researcher who coauthored the cloning and comparison of genes encoding human visual pigments. Relating their sequences helped connect molecular variation to the different spectral sensitivities underlying colour vision.^[ref]

Coauthor of Anatomy and Physiology 2e by J. Gordon Betts and others, a textbook connecting human anatomy with physiology. Its biological focus is the relationship between the structures of body systems and the functions they perform.^[ref]

Researcher in genetic recombination. Xu and collaborators studied human RAD51 filaments during strand exchange, connecting structures at different catalytic stages with the mechanism of homologous recombination.^[ref]