Lecture 03. Hyophyseal Cerebri or Pituitary Gland. By: Dr Farooq Khan PMC Date: 16 th March. 2018

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1 Lecture 03 Hyophyseal Cerebri or Pituitary Gland By: Dr Farooq Khan PMC Date: 16 th March. 2018

2 The pituitary gland Also called as Hypophyseal Cerebri. Hypo.Under. Physis..Growth Cerebri Cerebrum. Small pea shaped endocrine gland. Situated in relation to the base of skull in the middle cranial fossa in the body of the sphenoid bone.. Often called the Master gland of the body.

3 Location: Lies in the hypophyseal fossa or sella tursica or pituitary fossa. The fossa is roofed by the diaphragma sellae. The gland is divided into two parts: Anterior and Posterior. The posterior pituitary is a lobe of the gland that is functionally connected to the hypothalamus by the median eminence via a small tube called the pituitary stalk. The anterior pituitary is a lobe of the gland that regulates several physiological processes. The pituitary gland secretes nine hormones that regulate homeostasis.

4 The gland is oval in shape, and measures 08 mm anteroposteriorly and 12 mm transvrsely. It weighs about 1500 mg. Relations: Superiorly: Diaphragma Sellae. Optic Chiasma. Tuber Cinerium. Infundibular recess of the 3 rd ventricle. Inferiorly: Irregular venous channels between the two layers of dura. Hypophyseal fossa. Sphenoidal air sinuses. On each side: The cavernous sinus with its contents.

5 Subdivisions The gland consists of two Lobes: 1. Adenohypophysis (anterior lobe). Forms 80% of the gland. Consists of three parts. Pars Anterior (Pars Distalis). Largest part of the anterior portion. Highly vascular. Consists of Chromophil cells and Chromophobe cells. Pars Intermedia. Avascular zone. Poorly developed in the humans. Melanocyte stimulating hormone (MSH). When produced in the intermediate lobe, MSHs are sometimes called "intermedins" Pars Tuberalis. Encircle the infundibulum. Most vascular. Consists of some acidophil and basophil cells

6 2. Neurohypophysis Also called as Posterior lobe or Neural Structure. The posterior pituitary stores and secretes (but does not synthesize) the following important endocrine hormones: ADH (responsible for control of blood osmolarity), and Oxytocin (involved in parturition and milk secretion). Both of these substances are produced in the supraoptic and paraventricular nuclei of the hypothalamus and then subsequently stored in the posterior pituitary gland, ready for release. Pars posterior or pars nervosa: Forms the main Bulk. Infundibulum Arising from medial eminance. Median eminence. Small portion from base of hypothalamus.

7 Development of the pituitary Gland Anterior Pituitary: Oral Ectodermal origin. Projection from the the mouth is called the Rathke s pouch. Upward out pouch from roof of primitive oral cavity. Posterior Pituitary: Neuro ectodermal origin. Lowered out pouching. From Neuroectodermal tissues of central hypothalamus. This extension of the ventral portion of the brain will become the posterior pituitary. Ultimately the two tissues grows into one another and become tightly opposed, but their structures remain distinctly different from each other.

8 Hypophyseal portal system The hypophyseal portal system is a system of blood vessels in the microcirculation at the base of the brain. It connects the hypothalamus with the anterior pituitary. Its main function is to quickly transport and exchange hormones between the hypothalamus arcuate nucleus and anterior pituitary gland. The capillaries in the portal system are fenestrated which allows a rapid exchange between the hypothalamus and the pituitary. The main hormones transported by the system include gonadotropin-releasing hormone, corticotropin-releasing hormone, growth hormone releasing hormone, and thyrotropinreleasing hormone.

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13 Hormones of the anterior Pituitary Gland The anterior pituitary contains several different types of cells that synthesize and secrete hormones. Usually there is one type of cell for each major hormone formed in anterior pituitary. With special stains attached to high-affinity antibodies that bind with distinctive hormone, at least 5 types of cells can be differentiated. S.No. Type of cell Hormone secreted 1. Somatotropes 2. Corticotropes 3. Thyrotropes 4. Gonadotropes human growth hormone (hgh) adrenocorticotropin (ACTH) thyroid stimulating hormone (TSH) gonadotropic hormone i.e., both luteinizing hormone (LH) and follicle stimulating hormone (FSH) Percentage of type of cell 30-40% 20% 3-5% 3-5% 5. Lactotropes prolactin (PRL) 3-5%

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15 Intermediate lobe Although rudimentary in humans (and often considered part of the anterior pituitary), the intermediate lobe located between the anterior and posterior pituitary is important to many animals. For instance, in fish, it is believed to control physiological color change. In adult humans, it is just a thin layer of cells between the anterior and posterior pituitary. The intermediate lobe produces melanocyte-stimulating hormone(msh), although this function is often (imprecisely) attributed to the anterior pituitary. The intermediate lobe is, in general, not well developed in tetrapods. It is entirely absent in birds.

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21 thanks for your patience

22 Best of luck for exams!!!