Endocrine Glands 1

Endocrine

It is the study of endocrine system that co ordinate and integrates. the function of the body by the help of chemical messengers known as hormones .hormones are secreted by ductless glands and released directly into the blood . Pancreas is mixed gland with both exocrine or endocrine.

hormones

- hormones are biologically highly active substance secreted by ductless endocrine glands . the word hormone is derived from a greek words means I excite . Hormone regulates metabolism rowth secretion digestion excretion reproductive system etc .they alter the metabolic process of specialized cells and are known as target cell. Hormone act through following meahanism :-
1 induction protein synthesis at gene level
2 action at membrane level
3 enzyme system of cell
4 ions
- when some hormones work together to control a process this called "synergism". eg FSH and LH . when 2 hormones work against each other to control a process called antagonism .eg insulin and glucagon.Secretion of hormone is controlled by feedback mechanism.

Pituitary gland

- it is the smallest endocrine gland it is also known as the master gland.Because it regulates the secretion of other endocrine glands by secretion activity and inbiting factors . It is ectodermal in origin . Pitutary weigh 0.5 gm . It itself is in control of hypothalamus. so known as hypophyseal gland . It is situated in depression of sphenoid bone known as sella turcia . On the basis of origin it is divided into three:-

Adnohypophysis – it originates from the dorsal wall of stomodeum . it is anterior lobe of pituitary gland and attached with hypothalusm by blood vessels ,hormones secreted by anterios lobe are protein or glycoprotein.they are as followed :-
Somatotropic hormones
it is a polpetide and control growth . It is knon as growth hormones. Hyposecretion is childhood causes retardation of growth ,i.e pituitary Dwarfism . Such dwarf are seen in circus and know as midgets , Simond disease is caused by hyposecretion of puitarty in adult .Hypersecretion is early age causes overgrowth of various parts of body and the person grows gaint ,hepersecrtion in adult cause sincrease in weight and thickness of bone i.e acromegaly .
thyroid stimulating hormones
- It is gkycoprotein in nature and induces thyroid gland. It balance iodine inside our body , factors controlling secretion of TSH in body is T4.
Adrenocorticotropic hormones
it is smallest polypeptides of adenohyophysis and induces adrenal cotes. It stimulate the secretion of corticoids from adrenal cortex.
Follicle stimulatinh hormones
it is glycoprotein in nature . It stimulates the seminiferous tubules for spermatogenesis n male and growth of graffian follicles in female .
luteining hormes
it is glycoprotein and controls growth of corpus leuteum to secrte progesterone and ovulation in female . It stimulates interstitial cell in male to secrete testosterone hormone. Science luteininzing hormone stimulate growth and acivites of gonads these are called gonadotropic hormones.
Prolactine
it is polypeptide and controls secretion of milk . It is therefore reffered to hormones of maternity because, it main physiological effect is to activate growth of breast during pregnancy and secretion of mammary glands after child birth.
Pars intermedia
It is intermediate lobe of pituitary gland and is made up of granular epithelium cell. This lobe is functional in embryo but rudimentary in adult . This lobe has dual blood supply by means of a circle of wills .It secret only melanocytes stimulating hormones.
Neurohypophysis
it is posterior lobe pituitary gland extension of hypothalamus It has spindle shape cells called pituicyetes.
Antidiuretics hormens
its also known as vasopressin or pitressin.It is polpeptide in nature and cause contoacrtinb of arterial wall increasing blood pressure, it also promotes the reabsorption of water from distal convulated tubules of nephronIt deficiency causes Diabetes insipidus when the amount of ADH decreases in blood micturition increases .
Oxytocin
It is also called pitocin . It is poly peptide of 9 amnio acids It helps in parturition by causing contaction of uterine wall so called birth hormones .it also help in laction as well.

thyroid gland

it is lagest endocrine gland located on the ventral aspect of larynx and few treacheal ring it is bilobed gland. i.e right and left the two lobes are connected by isthumus .Thus forming a H-shaped or butterfly shaped structure thyroid gland developed from thyroglossal duct fromed by evagination of floor of phrynx ,between 1^st and 2^nd pharyngeal pouched . Embryological it is endodermal and largest endocrine gland .thyroid gland contains a large number of follicle embed in loose connective tissue .follicle are hollow structure filled with colloidal thyroidglobuline stroma also contains small group of specialized parafoclicaular or c cell .

thyroxine

- it is tetraiodothyronine product of A.A . it regulates the BMr o f the body stimulates heart beat, breathing rates etc . it is lipolytic and can be used for reducing body weight it is catabolic in nature and increase heat production
hypsectetion of thyroid gland gets enlarged due to iodine.
goiter – thyoid gland gets enlarged due to deficiency of iodine.
hyposecretion in childhood causes mental and physical retrardation I,e, cretinism – such dwarf are called cretin they are sexually sterile.
hypo secretion in adult causes deposition of fat and retardation of metabolism.It is condition caused by hypothyroidism characterized by a subnormal basal metabolic rate , dry coarse hair loss of hair , mental dullness anemia and slowed reflexes the disease which is due to minimal secretion of thyroid hormne is called "hashimotos disease".
hypersecretion cause following :-
toxic oiter – also known as plummers disease .
2 exopthalmia – eye ball buldges out eye orbita due to accumulation of mucus – thyroxine was crystallized by kendoll
calcitonin.
1 it is non iodinized hormone secretd by parafolloical cell.
2 it is hypocalamic hormones thus retared bons dissolution and stimulates excretion of calcium in urine.

Parathyroid gland

1 they are two pairs of small glands present embedded in dorsal surface of the lobes of thyroid .
parathyroid gland has 2 types of cell oxyphil and chief cells .
3 they are endodermal in origin.
fuction of parathormone:-
1 it is hypercalcemic hormone hence increases calcium concentration in blood.
2 it reduces phosphorus by metabolisation of calcium from bone and elimination f phosphate in urine.
3 vit D acts as synergetic of parathormone.
4 parathormone is essential for survival because it singnificantly contributes to homeostastis by regulatin the amount of calcium and phosphate ions in ECF.
5 it was discovered by collip so know as collip’s hormones hypersecretion caused tetny .This stage of sustained contraction of thocic and phernic musclkes.
hypersecretion causes osteporisi.

Reference:

Agrawal, sarita. principle of biology. 2nd edition . kathmandu: Asmita book Publication, 2068 ,2069

Mehta, Krishna Ram. Principle of biology. 2nd edition. kathmandu: Asmita, 2068,2069.

Jorden, S.L. principle of biology. 2nd edition . Kathmandu: Asmita book Publication, 2068.2069.