The part of an organ, such as a seed or a kidney, where blood vessels, nerves, and other structures enter or exit.

A type of joint that allows movement in one plane, like the elbow or knee, enabling flexion and extension.

A chemical involved in immune responses, particularly inflammation and allergic reactions, which causes blood vessels to dilate.

An amino acid that is important in enzyme function and as a precursor to histamine.

Molecules present on the surface of cells that help the immune system recognize foreign versus self cells, playing a key role in organ transplantation.

A scientist who specializes in the study of tissues, typically through the use of microscopy.

The study of the structure and function of tissues at the microscopic level.

Proteins that help package and organize DNA into a compact structure known as chromatin, playing a role in gene regulation.

The dissection or cutting of tissues for examination or research purposes.

Human immunodeficiency virus, the virus that causes acquired immunodeficiency syndrome (AIDS) by attacking the immune system.