Endocrine Glands Waqas Nawaz

11-arid-975 Group A-1

Endocrine glands are ductless organs that secrete special substances termed HORMONES.

These hormones are released into circulatory system and transported to distant receptor organ.

Hormones are produced by parenchymal cells,which can be found as single,aggregate or organized as endocrine glands.

Endocrine Glands:

Pituitary Gland Pineal Gland Thyroid Gland Parathyroid Glands Adrenal Gland Pancreas Gonads

Glands of Endocrine System:

Called “Master gland” of the body. Plays major regulatory role in entire

endocrine system.

Pituitary Gland

Situated at the base of skull. Suspended below diencephalon,in the

hypophyseal fossa of sphenoid bone. Connected to hypothalamus by pituitary

stalk.

Location:

Morphology:

Pituitary gland is an un-paired organ. Has size only of pea.

Anatomically pituitary gland is made up of following 3 parts……..

Adenohypophysis (anterior pituitary) Neurohypophysis (posterior pituitary) Intermediate lobe

Anatomy of Pituitary Gland:

Consists of endocrine cells, numerous blood vessels & very few nerve fibers.

The pituitary stalk contains a special portal system,organised in same manner as portal venous system in liver,with two capillary networks following each other.

Adenohypophysis:

Vessels from first capillary network convey blood to anterior pituitary.

While second capillary system surrounds the hormone producing cells.

Blood supply to adenohypophysis:

Hormones of adenohypophysis:

Hormone Effect

Somatotropin Growth via secretion of IGF-I

Thyroid stimulatin hormone (TSH)

Secretion of thyroid hormone

Adenocorticotopic Hormone (ACTH)

Secretion of glucocorticoids and androgens

Prolactin (PRL) Production of milk

Gonadotropin:- Follicle stimulating hormone

(FSH) Luteinzing hormone (LH)

Production and maturation of spermatozoa and oocyte.

Secretion of sex hormone

Second part of pituitary gland. It is a part of central nervous system.

Neurohypophysis:

Located caudal to adenohypophysis. It is a neural outgrowth of hypothlamus.

Location:

It consists of a stalk which connects the pituitary gland to tuber cinereum of hypothalamus and distal,major part of neurohypophysis.

Anatomy of neurohypophysis:

Contains no hormone producing cells. Instead the hormones are secreted by the

neurons which have their cell bodies into hypothalamus.

Because the posterior pituitary hormones are produced in hypothalamus.

So it is not entirely accurate to call posterior as endocrine gland,rather it acts as hormone storage store.

Mode of secretion:

Conti……..

Neurohypophysis stores and releases hormones produced by the neurosecretory cells of supraoptic and paraventricular nuclei of hypothalamus.

Conti..

Hormone Effect

Oxytocin Elicit milk let down Increase uterine

contractions

Antideuratic Hormone

Reabsorption of water in kidneys

Hormones of posterior pituitary:

Hormones of both lobes:

The portion of adenohypophysis, in direct contact with distal part of neurohypophysis is termed as intermediate lobe.

Intermediate lobe is present between two major parts of pituitary gland, which thing gives it its name.

During embryonic development intermediate lobe develops from epithelial tissue.

Intermediate lobe:

Intermediate lobe extends around neurohypophysis and the anterior lobe is separated from the intermediate lobe by the hypophyseal cleft which is also known as cavum hypophysis.

Anatomy of intermediate lobe:

The intermediate lobe of pituitary gland produces melanocyte stimulating hormone.

Which regulates the skin colour. This hormone regulates the skin colour only

in lower vertebrates but the function of this hormone is not known in mammals and birds, although it is secreted.

Hormones of intermd. lobe: