Hemostasis is the number of reactions that are initiated to stop bleeding. Hemostasis means prevention of blood loss. Hematopoiesis is the formation of blood cells. Coagulation is the process of blood clotting that results in a fibrin mass. The intrinsic pathway is one of two pathways that initiate blood clotting. Hemophilia is a X-linked disorder that is caused by the absence of a clotting factor. 

Basophils are classified as granulocytes. Their granules release enzymes during an allergic response. Baspophils are similar to mast cells and release histamine and heparin. Eosinophils play an important role in parasitic infections. Neutrophils are the body's first line of defense against invading bacteria. They search out, kill, and phagocytize bacteria that are involved in infection. Platelets are fragments of a larger cell called a megakarocyte. Platelets help form blood clots and prevent blood loss. Lymphocytes are involved in specific immune responses and include natural killer cells, b-lymphocytes, and t-lymphocytes.

The lymphatic system is part of the circulatory system and carries fluid called lymph, via lymphatic vessels, toward the heart. The lymphatic system functions to remove interstitial fluid from tissues, transport lipids as chyle from the digestive system, and defend the body against infection and the spread of tumors.

The circulatory system transports oxygen and nutrients to body tissues. Most nutrients are absorbed directly into the blood from the small intestine. Fats are the exception, and are transported into the lymph via lacteals.

The correct answer is returns excess interstitial fluid to blood. The other choices are functions of the urinary system, not the lymphatic.

The lymph capillaries in the lymphatic system pick up excess interstitial fluid and proteins and becomes lymph. If excess fluid is built up in the tissue spaces, blood volume and pressure will decrease. The lymph is returned to the blood in the veins (venous blood) to prevent this from occurring and also to minimize edema (swelling) from the fluid build-up.

The other choices are functions of the urinary system. Red blood cell production is controlled with the secretion of the hormone erythropoietin. Blood pressure is regulated by the secretion of the enzyme renin. The volume and composition of body fluids is maintained within normal limits by regulating the amount of water excreted in urine. The urinary system also acts to maintain concentrations of electrolytes in fluids and normal pH of blood.

Lymph flow is controlled by the contraction of skeletal muscle, smooth muscle cells around lymphatics, respiration, and gravity.

Osmosis is used to transport fluids into the lymph, but cannot be used to control lymphatic flow.

There are three main groups of lymph nodes that provide lymphatic drainage in the thoracic area. There are the sternal nodes, intercostal nodes, and phrenic nodes.

The sternal nodes, also known as the parasternal nodes, drain the areas of the medial part of the breast, the intercostal areas, the diaphragm, and the area above found above the umbilicus. They drain into the meeting point of the internal jugular and subclavian veins. The intercostal nodes also drain the area of the intercostal spaces and the pleura, emptying into the thoracic duct. The phrenic nodes collect lymphatic fluid from the pericardium, liver, and diaphragm. They empty into the posterior mediastinal lymph nodes. The axillary nodes drain into the apical nodes, which then empty into the subclavian vein.