B Raghunath Arts Commerce and Science College Parbhani

B. Raghunath Arts, Commerce and Science College, Parbhani Dr. Anil M. Khole (MSc, Bed, M. Phil, Ph. D) Head, Department of Zoology B. Raghunath College, Parbhani

UNIT – I PAPER - IX ENDOCRINOLOGY, ANATOMY & BIOCHEMISTRY Endocrine Glands § Endocrine glands are glands of the endocrine system that secrete their products, hormones, directly into the blood rather than through a duct. § The major glands of the endocrine system include the pineal gland, pituitary gland, pancreas, ovaries, testes, thyroid gland, parathyroid gland, hypothalamus and adrenal glands.

ENDOCINOLOGY § The hypothalamus and pituitary gland are neuroendocrine organs. § Local chemical messengers, not generally considered part of the endocrine system, include autocrines, which act on the cells that secrete them, and paracrines, which act on a different cell type nearby. § The ability of a target cell to respond to a hormone depends on the presence of receptors, within the cell or on its plasma membrane, to which the hormone can bind. § Blood levels of hormones reflect a balance between secretion and degradation/excretion.

ENDOCRINOLOGY Control of hormone release § The endocrine glands belong to the body's control system. The hormones which they produce help to regulate the functions of cells and tissues throughout the body. § Endocrine organs are activated to release their hormones by humoral, neural or hormonal stimuli. § Negative feedback is important in regulating hormone levels in the blood. § The nervous system, acting through hypothalamic controls, can in certain cases override or modulate hormonal effects.

ENDOCRINOLOGY HORMONES § The first hormone was discovered by the English physiologist William M. Baylies and Ernest H. Starling in 1903. The term hormone was introduced by Starling in 1905. § A hormone may be defined as a specific product (organic substance) of an endocrine gland secreted into the blood which carries it to specific part of the body where it produces a definite physiological effect. This effect may be either excitatory or inhibitory in its action. § Endocrine glands have no ducts and liberate hormones directly into the bloodstream. For this reason, the endocrine glands are referred to as the ductless glands.

ENDOCRINOLOGY PROPERTIES OF HORMONES§ Hormones are produced by specialized glands and are secreted directly into the blood stream. § Hormones are transported by the blood stream from the endocrine cells to serve as chemical messengers who act on target cells or organs by regulating the rates of specific metabolic reactions. § Hormones are required in very small amounts and their effect may be excitatory or inhibitory depending upon their concentration and the physiological state of the responding tissue. § A hormone belongs to different types of chemical structure. They may be steroids, proteins, peptides of amino acid derivatives.

ENDOCRINOLOGY CHEMICAL NATURE OF HORMONES All the hormones are organic substances of varying structural complexity. Chemically, they may belong to any of the following categories. a) Steroid Hormones b) Proteineous Hormones c) Catecholamine d) Amino acid derivatives e) Peptide Hormones

PITUITARY GLAND (Hypophysis) – § The pituitary gland or hypophysis cerebri is one of the well protected glands of the body. § It is unpaired organ located in the sella turcica, a concavity in the sphenoid bone.

PITUITARY GLAND – § The pituitary gland or hypophysis cerebri is one of the well protected glands of the body. It is unpaired organ located in the sella turcica, a concavity in the sphenoid bone. § The gland is closely applied to the floor of the fare brain (hypothalamus) and remains attached to it by means of a stalk containing nerve fibers and blood vessels. § In adult the pituitary gland consists of two distinct adjacent lobes called the adenohypophysis anterior pituitary and the neurohypophysis posterior pituitary.

PITUITARY GLAND § Your pituitary gland is about the size of a pea and is situated in a bony hollow, just behind the bridge of your nose. It is attached to the base of your brain by a thin stalk. § It secretes hormones from both the front part (anterior) and the back part (posterior) of the gland. Hormones are chemicals that carry messages from one cell to another through your bloodstream. § If your pituitary gland is not producing sufficient amounts of one or more hormones this is called hypopituitarism.

PITUITARY GLAND Structure § The pituitary gland is pea-sized gland sits in a protective bony enclosure called the sella turcica. It is composed of three lobes. § In animals these three lobes are distinct. In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary which is an extensionof the ventral diencephalon or Hypothalamus.

PITUITARY GLAND § The pituitary gland is pea-sized gland sits in a protective bony enclosure called thesella turcica. It is composed ofthree lobes. § In animals these three lobes are distinct. § In all animals, the fleshy, glandular anterior pituitary is distinct from the neural composition of the posterior pituitary which is an extension of the ventral diencephalon or Hypothalamus.

PITUITARY GLAND § The anterior lobe of the pituitary can be divided into the pars tuberalis and pars distalis that constitutes 80% of the gland. § The posterior lobe develops as an extension of the hypothalamus.

PITUITARY GLAND § The simple arrangement differs sharply from that of the adjacent anterior pituitary, which does not develop from the hypothalamus. § The release of pituitary hormones by both the anterior and posterior lobes is under the control of the hypothalamus. § The pituitary gland has three distinct parts – i) The anterior lobe or pars anterior or adenohypophysis ii)The middle lobe or intermediate lobe or pars intermedia iii) The posterior lobe or pars nervosa or neurohypohysis

PITUITARY GLAND Hormones of the anterior lobe or pars anterior or adenohypophysis 1) Somatotrophic Hormone or Growth Hormone § The growth hormone stimulates growth of all the body cells including the skeletal and muscular tissue. § It promotes protein metabolism, the absorption of calcium from the bowel and the conversion of glycogen to glucose.

PITUITARY GLAND 2) Thyrotrophic Hormone or Thyroid Stimulating Hormone (TSH) – § This hormone controls the growth and activity of the thyroid gland. § It influences the uptake of iodine, the synthesis of the hormones, thyroxine and tri-iodothyronineby the thyroid gland the release of stored hormones into the blood stream.

PITUITARY GLAND 3) Adrenocorticotrophic Hormone (ACTH) – This hormone stimulates the cortex of the adrenal glands to produce its hormones. 4) Prolactin Hormone (PRL) – § The prolactin hormone has a direct effect upon the breasts or mammary glands immediately after delivery of a baby and the expulsion of the placenta. § In conjunction with other hormone it stimulates the breasts to secrete milk. It also stimulates the corpus luteum of the ovary to secrete progesterone hormone.

PITUITARY GLAND 5) Gonadotrophic Hormones These are as follows – (i) Follicle-stimulating hormone (FSH) – It stimulates growth of ovarian follicles and their secretion of oestrogens in the female, and spermatogenesis (formation of sperms) in the male. (ii) Interstitial-cell stimulating hormones (ICSH) – It activates the Leydig’s cells of the testis to secrete androgens. In female, it stimulates the corpus luteum of the ovary to secrete progesterone.

PITUITARY GLAND Hormones of the Intermediate lobe or Pars intermedium § The secretion of the posterior lobe is known as pituitrin and it contains two hormones. Oxytocin (OT) – § Oxytocin promotes contraction of the uterine muscle and contraction of the myoepithelial cells of the lactating breast, squeezing milk into the large ducts behind the nipple. § In late pregnancy the uterus becomes very sensitive to oxytocin.

PITUITARY GLAND Antidiuretic hormone (ADH) or Vasopressin – This hormone has two functions. (a) Antidiuretic effect. It increases the reabsorption of water in the distal convoluted tubule, collecting tubules and collecting ducts of the nephrons of the kidney. (a) Pressor effect. Involuntary muscles in the walls of the intestine, gall bladder, urinary bladder and blood vessels are stimulated to contract by ADH. Contrraction of the walls of the blood vessels raises the blood pressure and this may be its most important pressor effect.

PITUTARY GLAND PITUITARY DISORDERSPituitary Dwarfism – § It is caused by the deficiency of growth hormones (GH) from childhood. It is characterized by small but well proportioned body and sexual immaturity. § The dwarfs produced by the deficiency of growth hormone are different from those which are formed from the deficiency of thyroid hormone in having normal intelligence.

PITUTARY GLAND Gigantism – It is caused by excess of growth hormone from early age. It is characterized by large and well proportioned body. If size of pituitary gland increases, it affects optic chiasma and ultimately affects vision. Acromegaly – It is caused by excess of growth hormone after adult size is reached. It is characterized by disproportionate increase in size of bones of face, hands and feet.

PITUTARY GLAND Diabetes insipidus – It is caused by the deficiency of ADH. It is characterized by excessive excretion of dilute urine. High blood level of ADH – It is caused by excessive secretion of ADH. It is characterized by excessively dilute blood and low plasma sodium.

EXAMPLES OF PITUITARY DISORDERS PITUITARY DWARFISM

EXAMPLES OF PITUITARY DISORDERS GIGANTISM

EXAMPLES OF PITUITARY DISORDERS ACROMAGLY

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