Hormones of Heart, Kidney and Gastrointestinal Tract
இதயம், சிறுநீரகம், இரைப்பை-குடல் பாதையின் ஹார்மோன்கள்
Erythropoietin comes from the juxtaglomerular cells of the kidney, not from the bone marrow it acts on. And ANF comes from the heart's atrial wall. Organs that are not 'glands' still make hormones.
The idea
Hormones are also secreted by some tissues which are not endocrine glands. For example, the atrial wall of our heart secretes a very important peptide hormone called atrial natriuretic factor (ANF), which decreases blood pressure. When blood pressure is increased, ANF is secreted, which causes dilation of the blood vessels and thereby reduces blood pressure. The juxtaglomerular cells of the kidney produce a peptide hormone called erythropoietin, which stimulates erythropoiesis (formation of RBC). Endocrine cells present in different parts of the gastro-intestinal tract secrete four major peptide hormones — gastrin, secretin, cholecystokinin (CCK) and gastric inhibitory peptide (GIP). Gastrin acts on the gastric glands and stimulates the secretion of hydrochloric acid and pepsinogen. Secretin acts on the exocrine pancreas and stimulates secretion of water and bicarbonate ions. CCK acts on both the pancreas and the gall bladder and stimulates the secretion of pancreatic enzymes and bile juice, respectively. GIP inhibits gastric secretion and motility. Several other non-endocrine tissues secrete hormones called growth factors, which are essential for the normal growth of tissues and their repairing/regeneration.
Why it matters
Organs sense local conditions best — the heart senses stretch, the kidney senses oxygen supply, the gut senses food — so they release hormones that adjust the body accordingly.
NEET lens
Pairs: ANF — atrial wall of heart, vasodilation, ↓BP; erythropoietin — juxtaglomerular cells of kidney, RBC formation; gastrin — gastric glands (HCl, pepsinogen); secretin — exocrine pancreas (water, bicarbonate); CCK — pancreas and gall bladder (enzymes, bile); GIP — inhibits gastric secretion and motility. In target matching, CCK → pancreas, GIP → gastric gland, ANF → (made in) heart, ADH → kidney.
Clinical significance
Patients with chronic kidney failure become anaemic because the damaged kidney makes too little erythropoietin; synthetic erythropoietin injections correct this. Gastrin-secreting tumours cause excess stomach acid and severe ulcers.
Introduction
Hormones are also made by tissues that are not classical endocrine glands — the heart, kidney and gastrointestinal tract.
Core concept
Heart: atrial wall → ANF (peptide); released when BP rises; dilates blood vessels → ↓BP. Kidney: juxtaglomerular cells → erythropoietin (peptide) → erythropoiesis (RBC formation). GI tract (four peptide hormones): gastrin → gastric glands → HCl and pepsinogen; secretin → exocrine pancreas → water and bicarbonate ions; CCK (cholecystokinin) → pancreas and gall bladder → pancreatic enzymes and bile juice; GIP (gastric inhibitory peptide) → inhibits gastric secretion and motility. Growth factors: from non-endocrine tissues; normal growth, repair and regeneration of tissues.
Go deeper
ANF checks the renin-angiotensin mechanism — the two have opposite effects on blood pressure (see Regulation of Kidney Function).
From Class 10
You may not have thought of the heart or stomach as hormone makers. NEET expects you to know these four GI hormones and two others.