2. Pituitary Gland The hypophysis (Gr. hypo, under, + physis, growth), or pituitary gland Weighs about 0.5 g It lies in a cavity of the sphenoid bone—the sella turcica—an important radiological landmark During embryogenesis, the hypophysis develops partly from oral ectoderm and partly from nerve tissue

4. Because of its dual origin, the hypophysis actually consists of two glands: Neurohypophysis Adenohypophysis They are united anatomically but have different functions.  Neurohypohysis (Posterior Pituitary)neural part. Consists of: Pars nervosa Infundibulum(stalk and median eminence)

8. Adenohypophysis(Anterior Pituitary)glandular part: It arises from oral ectoderm. It is subdivided into three portions: Pars Distalis Pars Tuberalis Pars Intermedia.

9. Adenohypophysis Pars Distalis(anterior lobe) : The largest part of adenohypophysis The main components of the pars distalis are cords of epithelial cells. Highly vascular stroma. The hormones produced by these cells are stored as secretory granules. Fibroblasts produce reticular fibers that support the cords of hormone- secreting cells.

10.  The pars distalis accounts for 75% of the mass of the hypophysis.  Common stains allow the recognition of three cell types in the pars distalis:  Chromophobes(Gr. chroma, color, + phobos, fear)  Chromophils (Gr. chroma + philein, to love)  Two types of chromophils: Basophils according to their affinity for basic dyes Acidophils according to their affinity for acid dyes  The subtypes of basophil and acidophil cells are named for the hormones they produce. With the exception of the gonadotropic cell, which produces two hormones, the other cells produce only a single hormone. Chromophobes(degranulated secretory cells) do not stain intensely and, when observed with an electron microscope, show two populations of cells.

11. Secretory Cells of the Pars Distalis Hormone ProducedStain AffinityCell Type Growth hormone (GH, somatotropin)AcidophilicSomatotropic cell Prolactin (PRL)AcidophilicMammotropic cell Follicle-stimulating hormone (FSH) Luteinizing hormone (LH) BasophilicGonadotropic cell Thyrotropin (TSH)BasophilicThyrotropic cell Corticotropin (ACTH α-Melanocyte-stimulating hormone? (α-MSH)) BasophilicCorticotropic cell α-Melanocyte-stimulating hormone? (α-MSH) BasophilicMelanotropes?

13. Pars Tuberalis The pars tuberalis is a funnel-shaped region surrounding the infundibulum of the neurohypophysis. Most of the cells secrete gonadotropins (follicle- stimulating hormone and luteinizing hormone) Are arranged in cords alongside the blood vessels.

15. Pars Intermedia Is a rudimentary region in humans Made up of cords and follicles of weakly basophilic cells that contain small secretory granules. It produces Melanocyte-stimulating hormone (α-MSH).

16. Neurohypophysis (Posterior pituitary)  It consists of Pars nervosa Infundibulum (neural stalk ) stem and median eminence.that connects it to the hypothalamus.

17. The pars nervosa Does not contain secretory cells. Contains nonmyelinated axons and nerve endings of neurosecretory neuron The nerve endings have terminal dilations called Herring bodies

18. Pars Nervosa  Neurosecretory neurons have cell bodies that lie in the supraoptic & paraventricular nuclei in the hypothalamus The secretory neurons have all the characteristics of typical neurons The secretory neurons have well-developed Nissl bodies related to the production of the neurosecretory material  Cells present in Pars Nervosa are: Pituicytes (glial cell) fibroblasts mast cells.

19. Adrenal Glands This gland is found above the kidney. The dense connective tissue capsule covers the adrenal gland & sends thin septae into the gland. Septae support the blood vessels and nerves The stroma consists mainly of a rich network of reticular fibers that supports the secretory cells. The parenchyma consists of cortex and medulla.

20. The cortex is subdivided into 3 concentric zones, according to the arrangement of the cells these zones are called: i.ZonaGlomerulosa. ii. Zona Fasiculata. The cells in this zone are called spongiocyes. iii. Zona Reticularis.