What is the medical term for the smallest blood vessel?

The medical term for the smallest blood vessel in the body is capillary. Capillaries are tiny, thin-walled vessels that connect arterioles (the smaller branches of arteries) to venules (the smaller branches of veins). They play a crucial role in the circulatory system by allowing the exchange of oxygen, nutrients, and waste products between blood and surrounding tissues. The structure of capillaries, being only one cell thick, facilitates this process, enabling efficient transport of materials at a cellular level.

In contrast, neuritis refers to inflammation of a nerve or nerves, maxilla denotes the upper jawbone in vertebrates, and goiter is an enlargement of the thyroid gland. These terms relate to different aspects of anatomy or health conditions but do not pertain to the vascular system or blood vessels.