Found at points along lymphatic vessels. Have fibrous connective tissue capsule with incoming and outgoing lymphatic vessels. Each nodule contains sinus filled with lymphocytes and macrophages. Located in upper left abdominal cavity just beneath diaphragm. Lobules contain sinuses filled with blood.
White pulp contains mostly lymphocytes.
Both help to purify the blood. Divided into lobules where T lymphocytes mature. Red Bone Marrow i. Site of origin of all types of blood cells. Stem cells continuously divide to produce cells that differentiate into various blood cells. Most bones of children have red blood marrow.