The body abounds with tubes of various diameters.

• The tubes most often seen in histological sections are blood vessels and their accompanying lymphatics (the tubes that carry lymph).
• Also, many glands are furnished with tubular ducts that carry their secretions.
• Tubes are not difficult to recognize if they are cut transversely.
• But if they are cut longitudinally or obliquely, or if they are cut at a site where they curve, it is important to think in three dimensions to recognize them as tubes.

Examine a specimen such as kidney with many tubes in many different orientations. Identify tubular structures cut transversely, longitudinally, and obliquely.

Interpreting microscopic structures in histological sections.