ENDOCRINE GLAND

1. ENDOCRINE GLAND PITUITARY GLAND Mrs. Asha r. bidkar dept. – zoology y.c. college, tuljapur

3. Pituitary gland is known as master gland because its harmons control the functions of other endocrine glands. • But the pituitary itself under the control of hypothalamus of brain. • The pituitary gland is ectodermal and endodermal in origin and develops from nervous tissue and epithlial tissue. • So the pituitary is cranioepithalial in origin.

4. Morphology • Pituitary gland is located on ventral side of midbrain behind the optic chiasma in the depression of sphinoid bone called hypophysealfossa. • It is smallest gland pea shaped and measures about 10mm in diameter.It is slightly larger in females. • It is reddish gray in coloured and attached to the hypohtalamous of brain by infundubular stalk of connective stssue, blood capilaries. • The pituitary gland shows two distinct lobes namely adenohypophysis and neurohypophysis

5. Adenohypophysis • Adenohypophysis is anterior lobe of gland conneced to the hypothalamus through pituitary portal vein. • It is edodermal in orgin .It developed from the epithelial out growth of embryonic pharynx called Rathke’s pouch. It is nonnervous and secretary lobe of the gland and contains secretary cells. • This lobe secrets 6 to 7 hormonsi.e.STH,ACTH,TSH,FSH,LH,PL, and MSH. • It is largests lobe of the gland.It divides into three lobes . • 1) pars tubularis 2)pars distalis 3)pars intermedia.

6. Pars tubularis—It is tubular part . It is present anteriorly around the infundibulum. It does not secrets any hormone. • Pars distalis--- It is largest part It is glandular and consists secretary cells. It is enclosed in a collagenous capsules and consists of reticular connective tissue, they are mainly two types 1)chromophils 2) chromophils. • Chromophils are larger cells with secretary activities. These are two types Acidophilic and Basophilic. • Acidophilis –1)Type A-secrets hormone STH. 2)Type B-secrets hormone PL or LTH. Basophils-- 1)Beta- -secrets hormone TSH. 2)Delta- secrets hormone FSH and LH. • Pars intermedia—It is present in between pars distalis and pars nervosa. It is reduced, iess developed and nonfunctionalinhumen being. It secrets hormone MSH or intermdin.

7. Neurohypophysis It is posterior lobe of gland attached by infundibular gland . It is nuroectodermal in origin and developed from down growth of embryonic midbrain of hypothalamus.It is nervous lobe of gland because it contains mainly the axon fibers of neurosecretary cell . The diluted ends of axons are called knobs or herring corpuscles. Axon knobs store two hormons ADH and Oxytocin secreted byneurosecretary cell hypothalamus are released into the blood whenever needed. It is divided into three parts. 1) Median eminence 2) Infundibulum 3)Pars nervosa

8. Horomnes of pituitary gland • 1) Somatotrophichormon (STH or GH)—It is secreted by acidophils. It increases the growth of bone by increasing absorption of Ca from intestine. It increases amino acid uptake and proeinsynthesis.It increase glucose level in blood by decreased secretion of insulin. • Disorders- • Gigantism- Hypersecretion of hormones in childhood leads to gigantism.It shows abnormal increase in hight. • Acromegaly - Hypersecrtion in adult leads to acromegaly. It shows abnormal elongation of long bones of limbs, spines get curved. Abnormal growth of bone of lower jaw. • Dwarfism- Hypersecretion of growth hormones during childhood ieads to dwarfism. Person shows retarded physical growth but patient has normal brain. Frohlics—mentally abnormal. Lorain—mentally normal. • Simmonds type –Hypersecretion in adult. It leads to early sterility, degeneration of sex organs. Skin become dry and wrinkled.

10. 2)Melanocyte Stimulating hormone ( MSH )– It is secrets by pars intermedia. It causes changes in skin colour of lower animals but the function is unknown in humenbeing.It may affect nervous tissue excitability in mammals.In fishes, amphibians and reptiles it controls the synthesis and dispersal of melanin pigments. • Prolaction (PL)—It is secreted by acidophils. It stimulates the synthesis the of milk in mammary gland. It is also called mamotrophic hormone (MTH) This hormone also maintain corpus leutum during pregnancy and stimulate secretion of progesterone from corpus leutum. • Thyroid stimulating hormone (TSH)—It is secreted by basophils It increases iodine uptakefor synthesis of thyroxine in thyroid gland. TSH stimulates the growth and secretion of thyroid gland. Hyposecretion of TSH leads to atrophy . Hypersecretion of TSH produce symptoms of Graves disease.

11. Adrenocorticotrophicharmone (ACTH)-- It is secreted by basophils and agranularchromophobes. It controls the growth and secretion of adrenal cortex to release glucocorticoids and mineralocorticoides. • Hyposecretion of ACTH leads to rhamatoid arthritis and addisonsdisease.Hypersecretion leads to exccivegroth of adrenal cortex and causes cushing syndrome . • Gonadotrophic hormone (GHT)—It is two hormones FSH and LH. These two harmones controls the growth and functions of gonads.

12. FSH—It is also called gametokinetcfactor.It is glycoprotein secreted by both sexes. In female it stimulates the formation of mature Graffian follicles in ovaries. It also stimulates secretion of estrogen from follicular cells which controls the development of secondary sexual characters in female. In males it stimulates the testes for production of sperms. • LH –( luteinizing hormone)-In females it stimulates buresting of graffian follicles to release ovum i.e, ovulation .In male LH is called ICSH (interstitial cells stimulating hormone) because it controls the secretion of interstitials cells of testis and stimulates the secretion of hormone testestrone which control the development of secondary sexual characters in male.

13. Hormones of Neurohypophysis • Hormones are not synthesized by neurohypophysis. This lobe only stores and releases the hormones synthesized by neurosecretary cells of hypothalamus. This lobe release the hormones such as ADH and Oxytocin. These are neurohypophysial hormones. • Antidiuretic hormone (ADH) -- It is also called vasopressin. This hormone is called antidiuretic because it is against dilute urine.It increases the permeability of DCT and CT for absorption of water from filtrate and regulate the water balance. • Deficiency of ADH causes diabetes insipidus. • Oxytocin means quick birth and it controls contraction of smooth muscles of uterus to produce labour pains for normal delivery. It is also milk ejection hormone because it causes release of milk from mammary glands after child birth.

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