The nervous system is a network of specialized cells that coordinate the actions of an animal and send signals from one part of its body to another. 

The digestive system is the system by which ingested food is acted upon by physical and chemical means to provide the body with nutrients it can absorb and to excrete waste products; in mammals the system includes the alimentary canal extending from the mouth to the anus.

Sickle-cell disease, or sickle-cell anaemia (or drepanocytosis), is a life-long blood disorder characterized by red blood cells that assume an abnormal, rigid, sickle shape. Sickling decreases the cells' flexibility and results in a risk of various complications.

histiocytosis: a blood disease characterized by an abnormal multiplication of macrophages