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HEART AS ENDOCRINE GLAND ·  The atrial myocytes secrete a hormone called Atrial Natriuretic Peptide (ANP). ·   Structure ·  Atrial natriuretic peptide is a 28-aminoacid residue polypeptide. ·  It is formed from a larger precursor molecule containing 151 amino acid residues. Biological action ·  Atrial natriuretic peptide, in general, antagonizes the actions of the angiotensin- aldosterone system. a. ANP inhibits the secretion of renin and aldosterone, b . ANP inhibits NaCl reabsorption in the collecting ducts of the kidney, c. ANP inhibits the secretion of ADH and its action on the collecting ducts of the kidney, d. ANP is a vasodilator. ·   Note:   The net effect of ANP will be natriuresis, diuresis and hypotension. ADIPOSE TISSUE AS ENDOCRINE GLAND ·  Adipose tissue, especially visceral fat, is an active endocrine organ. ·  Hormones produced by adipose tissue play an important role in the regu...

Pineal body ·  The  pineal gland or epiphysis cerebri is a small, reddish-grey organ that lies dorsal to the superior colliculi (brain). ·  In the adult, it weighs about 150 mg, is about 8 mm long and 4 mm wide. · In infants, the pineal gland is large and begins to involute before puberty. · So it shows  retrogressive changes. ·  The gland is surrounded by a capsule and is made up of several lobules separated by connective tissue septa. ·  The lobules contain cords and follicles of parenchymal cells called pinealocytes. ·  Several types of pinealocytes are present and are rich in cytosolic organelles concerned with secretory function. ·  In addition, other cell types, like   neuroglia, macrophages are also present. ·  The adult gland shows calcification and is known as  'brain sands'. · They are calcium-containing hydroxyapatite crystals in the extracellular matrix. ·  The pineal gland has a very rich blood supply and the capil...

Pancreas ·  Pancreas is the second-largest gland AFTER lIVER . ·  It is a mixed type of gland, heterocrine in nature because it secretes both hormones and enzymes. ·   Location:  It is located in the curvature of the duodenum. ·   Shape:   Irregular leaf-like shape. ·  Its weight is about 80 gm. ·   Structure:   Pancreas consists of 2 types of cells:  (i) Exocrine cells or acinar cells (98%) of the total volume of the pancreas): they are responsible for the secretion of pancreatic enzymes. (ii) endocrine cells are the specialized glandular cells, found in scattered groups throughout the organs, known as the Islets of Langerhans or small islands (1-2 %). ·  In 1869, Paul Langerhans demonstrated its endocrine functions for the first time. ·  Total islets tissue consists of 1-3 per cent of the whole pancreatic tissue. ·  Pancreatic islets has three types of cells: Alpha, Beta and Gamma Cells. 1. ɑ cells or alpha ce...

1. Location: ·  Adrenal glands are two in number, the Adrenal cortex and the Adrenal medulla. ·  Each lies at the top of each kidney, hence also called the  suprarenal glands. 2. Shape: ·  They are roughly triangular or conical in shape. ·  The right gland is smaller than the left one. ·  Each measure about 150×30-40×10mm. 3. Color:   yellow 4. Weight:  Average weight of each gland is about 5-9gm in adults. 5. Structure: ·  Anatomically, each gland is composed of two distinct parts which are the cortex and the medulla. ·  These two parts are structurally, functionally and embryologically different from each other. A. Adrenal cortex ·  Adrenal cortex is mesodermal in origin. It constitutes 80-90% of the adrenal gland by volume. ·  It consists of three zones:  Zona glomerulosa,  Zona fasciculate,  Zona reticularis. (i) Zona glomerulosa ·  The zona glomerulosa accounts for about 15 per cent of the volume of t...

Thyroid Gland ·  It is the largest endocrine gland, 25 g weight. ·  Location: ·  I t is located in front of the lower half of the larynx and upper five tracheal rings at the level of the fifth  cervical vertebra (C5) to first thoracic   (T1) vertebra. ·  It consists of two symmetrical lobes connected by an isthmus. ·   These lobes are surrounded by the connective tissue capsule. ·  It is endodermal in origin. ·  Histologically made up of a large number of follicles (about five million follicles). ·   Follicles are internally lined by   simple cuboidal epithelium or principle cells. ·   In between the follicles: Parafollicular or C-cells are present. ·  The follicular lumen is filled by a proteinous substance called colloid. ·   Colloid is thyroglobulin or glycoprotein with the molecular weight of 660000 containing 140 tyrosine residues. ·  It is supplied by 2 pairs of thyrocervical arteries, 3 pairs of veins. · ...