The lymphatic system keeps our tissues from retaining fluid and houses many of the key components of the immune system, like lymph nodes. Learn how this underappreciated body system is organized and how it functions.

This video shows the constant battle between the two main cell types in bone, osteoblasts and osteoclasts. Osteoblasts builds bone while osteoclasts dissolve bone for renovation and remodeling. The video explains how these cells influence the strength of bone throughout life.