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Semen is the fluid discharged by the male reproductive tract during ejaculation. In humans it normally contains sperm suspended in secretions from reproductive glands, including the prostate and seminal vesicles. Semen is therefore a mixture, whereas a sperm is an individual gamete.^[ref]

Fluid volume and the number or movement of sperm describe different properties. A sample can contain fluid but few or no sperm, so visible semen alone does not establish successful gametogenesis or fertilization.

A respiratory RNA virus of rodents used as a model and experimental tool. Its natural host range and laboratory applications should be distinguished from assuming it is an ordinary human respiratory pathogen.

An apparatus capturing, transforming and presenting information through an available sensory channel. Evaluation must distinguish transmitted resolution from human recoverability, and laboratory identification from practical use.

Wastewater containing domestic or other wastes, commonly including human excreta. Treatment separates and transforms contaminants before discharge or reuse, connecting waste handling with protection of water sources.

The shoulder is the region connecting the proximal forelimb to the trunk. In human anatomy, movement involves several linked articulations and the shoulder girdle, rather than only the joint between humerus and scapula.

Cervus nippon, introduced into parts of Britain and Ireland through human management.

Skhul is a Levantine cave locality with early Homo sapiens remains. Together with Qafzeh, it is important for testing the timing and complexity of early human dispersal. A local occurrence does not by itself demonstrate continuous occupation across the entire interval between that deposit and later populations.

A transient thalamocortical oscillatory event, often around 10–16 Hz in humans, with frequency boundaries depending on the measurement convention. Its timing relative to other events can matter beyond its total count.

A sweat gland is a skin gland delivering secretion to the surface or a related follicular route. Eccrine glands are important in human evaporative cooling. Gland activation, fluid transport and environmental evaporation are separate determinants of the cooling achieved.

A tumour-graft model using a genetically compatible host and donor, enabling investigation in an immune-competent setting. It generally uses mouse rather than human tumour biological cells.

This deliberately synthetic differential equation model illustrates response direction and lag. Every plotted number is chosen for teaching; none is a biological measurement or a fitted human parameter. Let externally prescribed, dimensionless $g>0$ represent a glucose stimulus relative to a reference. Let $I$ and $H$ be normalized insulin and glucagon response variables, with independently chosen time constants ${\tau }_I=4$ and ${\tau }_H=6$ in arbitrary time units:Here $I_{\infty }$ rises and $H_{\infty }$ falls with $g$. Their targets add to one by construction; the evolving $I+H$ need not equal one because their time constants differ. Start with $g=1$ and $I=H=1/2$. Set $g=1.6$ from $t=10$ to $40$, $g=0.65$ from $t=40$ to $70$, and $g=1$ otherwise. Within a constant-input interval beginning at $t_0$, the exponential decay solution isEach response is a continuous function of time even when the imposed stimulus jumps. The chosen starting values stay between zero and one, since each solution is a weighted arithmetic mean of its interval's starting value and target.

For an illustrative downstream comparison, define release tendency $R=0.3+0.6H/(1+I)$ and uptake tendency $U=(0.25+0.5I)g$, in the same arbitrary flux units. At the reference target, $R=U=0.5$. At the high-stimulus targets, $R\approx 0.343$ and $U\approx 1.094$; at the low-stimulus targets, $R\approx 0.742$ and $U\approx 0.212$. These chosen functions encode greater uptake with insulin and greater release with glucagon, moderated by insulin; they are not established enzyme kinetics. The $g$ trace is imposed externally, so the figure does not demonstrate self-correction of blood glucose. A closed model would also need a conservation of mass equation, nutrient input, finite glycogen stores, and additional tissue interactions. The qualitative restoring loops are shown separately in the insulin circuit.

The pork tapeworm. Human intestinal adults and tissue cysticerci follow different routes of infection.

A tendency for object decisions to follow local texture rather than global shape under cue conflict. Human–model comparisons on matched conflict images can reveal different strategies despite similar ordinary classification accuracy. Altered training distributions can change the bias without changing the network architecture.^[ref]

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

Researcher in comparative embryology. Boroviak and collaborators compared single-cell expression profiles of human, marmoset and mouse embryos, identifying shared and divergent features of development before implantation.^[ref]

The thumb is the first digit of the human hand. Its basal joint and muscular control permit opposition toward other fingers, supporting precision grasp. Mobility, orientation and sensory control together explain its function more fully than digit length alone.

Researcher in human evolution. White and collaborators investigated Ardipithecus ramidus, connecting fossil anatomy and environmental evidence with the interpretation of early hominin biology.^[ref]

The human whipworm, with its thin anterior end embedded in colonic mucosa.

The uterus is a muscular reproductive organ in which an implanted conceptus develops during human gestation. Its inner endometrium changes during reproductive cycles, while its thick myometrium supplies contractile force. The lower cervix connects its cavity to the vagina.

A human prion disease associated with exposure to the BSE agent. Exposure totals and clinical-onset totals measure different stages of the disease process; incubation periods and ascertainment affect their relationship.