háræðanna

Háræðanna refers to the smallest blood vessels in the circulatory system. These microscopic vessels form a network that connects arterioles, which are small arteries, to venules, which are small veins. The primary function of háræðanna is to facilitate the exchange of substances between the blood and the surrounding tissues. Their thin walls, often only one cell thick, are ideally suited for this vital process.

Through their permeable walls, oxygen and nutrients are delivered from the blood to the body's cells, while carbon dioxide and waste products are picked up from the cells to be transported away. This exchange is crucial for maintaining cellular function and overall organismal health. The diameter of háræðanna is so small that red blood cells often have to pass through in single file.

There are two main types of háræðanna: continuous and fenestrated. Continuous háræðanna are found in most tissues and have a complete, uninterrupted wall. Fenestrated háræðanna, on the other hand, have small pores or windows within their walls, which allow for a more rapid passage of fluids and small solutes. These are typically found in organs where rapid exchange is necessary, such as the kidneys and the small intestine. The intricate network of háræðanna ensures that every cell in the body has access to the necessary resources and can efficiently remove waste.