Hormones of Heart, Kidney and Gastrointestinal Tract

The organised endocrine glands are not the only sources of hormones in the body. Several tissues that are not endocrine glands in the usual sense also release hormones, and these play important regulatory roles in the heart, kidney and digestive tract.

Hormone from the heart

The atrial wall of the heart secretes a peptide hormone called atrial natriuretic factor (ANF), whose job is to lower blood pressure. When blood pressure rises, ANF is released; it causes the blood vessels to dilate (widen), and this widening brings the blood pressure back down.

Hormone from the kidney

The juxtaglomerular cells of the kidney produce a peptide hormone called erythropoietin. This hormone stimulates erythropoiesis, the formation of red blood cells.

Hormones of the gastrointestinal tract

Endocrine cells scattered through different parts of the gastrointestinal tract secrete four major peptide hormones, each controlling a part of digestion:

• Gastrin — acts on the gastric glands and stimulates the secretion of hydrochloric acid and pepsinogen.
• Secretin — acts on the exocrine pancreas and stimulates the release of water and bicarbonate ions.
• Cholecystokinin (CCK) — acts on both the pancreas and the gall bladder, stimulating the secretion of pancreatic enzymes and of bile juice respectively. …