(I) Kidney:
1. Kidney produces renin, erythropoietin and calcitriol (calcitriol is the active form of vitamin cholecalciferol (D3).
2. Renin along with angiotensin helps in maintaining the blood pressure in the renal artery by vasoconstriction.
3. Erythropoietin stimulates erythropoiesis.
4. Calcitriol helps in absorbing calcium from the stomach.
(II) Heart:
1. Heart walls secrete Atrial natriuretic hormone /ANE
2. ANF increases sodium excretion [natriuresis] along with water.
3. It acts along with kidneys and reduces blood pressure by lowering blood volume.
