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Pars Distalis 1- Median Eminence

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Pars Distalis 1- Median Eminence HISTOLOGY Endocrine Block – 432 Histology Team Lecture 1: Pituitary Gland Done by: Shroog Al-Harbi Reviewed by: Ibrahim Al-Furaih Color Guide: Black: Slides. Red: Important. Green: Doctor’s notes (Female). Blue: Doctor’s notes (Male). Orange: Explanation. Objectives At the end of this lecture, you should describe the microscopic structure and the function of: 1. The microscopic structure of the different parts of the pituitary gland in correlation with their functions. 2. The hypophyseal portal circulation; components and significance. Mind Map PITUITARY GLAND (A) ADENOHYPOPHYSIS (B) NEUROHYPOPHYSIS CEREBRI (anterior lobe): CEREBRI (posterior lobe): 1- Pars Distalis 1- Median eminence. (pars anterior). 2- Infundibulum: Neural 2- Pars Tuberalis. (Infundibular) Stalk. 3- Pars Intermedia. 3- Pars Nervosa. Pituitary Gland PARS DISTALIS Types of parenchymal cells: 1- Chromophils 2- Chromophobes (pale) A-Acidophils (red): B- Basophils(blue): May represent: 1- Somatotrophs (GH secreting 1- Thyrotrophs (TSH secreting 1- Stem cells. cells). cells). 2- Degranulated 2- Mammotrophs (Prolactin 2- Gonadotrophs chromophils. secreting cells); Increase during (Gonadotropic cells) (FSH, LH). 3- Degenerated cells. lactation and late pregnancy. 3- Corticotrophs (ACTH cells). Blue arrow: Acidophils. Red arrow: Basophils. Yellow arrow: Chromophobes. Y PARS NERVOSA e l CONTENTS: l 4- Fenestrated 1- Unmyelinated axons 2- Herring bodies 3- Pitucytes o blood capillaries w Unmyelinated axons of Are distensions of the Are glial-like cells in secretory neurons situated in axons in pars nervosa. pars nervosa. a supraoptic & paraventricular Structure: r r nuclei (i.e. Axons of Representing Have numerous o hypothalamo-hypophyseal accumulation of cytoplasmic processes. w tract). neurosecretory Function: : Function: granules at axon termini Support the axons of Storage & release of: and along the length of the pars nervosa. c h 1) Vasopressin (ADH; the axons in pars r antidiuretic hormone) nervosa. N.B. No secretory or o By Supraoptic nuclei. neuronal cells in pars m 2) Oxytocin: By Paraventricular nervosa. o nuclei. p h o b e s e l l o w BLOOD SUPPLY 1- Superior Hypophyseal Arteries (Right & Left) 2- Inferior Hypophyseal Arteries (Right & Left) To median eminence & neural stalk. Mainly to pars nervosa Not participating in hypophyseal portal circulation. [ Hypophyseal Portal System ]:- a) 1ry capillary plexus of fenestrated capillaries. b) Hypophyseal portal Veins (or venules). c) 2ry capillary plexus of capillaries in adenohypophysis (mainly in pars distalis). It carries neurohormones from median eminence to adenohypophysis. Summary: By: Shaimaa Alrefaie PITUITARY GLAND Components Blood Supply Adenohypophysis Cerebri Neurohypophysis Cerebri Pars Pars Median Pars distalis Infundibul 1. Superior Hypoph. tuber interme eminen Pars Nervosa Arteries (Rt&Lt): (pars anterior) um alis dia ce To median eminence & Types of parenchymal cells: Neural 1. Unmyelinated axons of neural stalk. 2- stalk. secretory neurons situated in 1- Chromophils Chromophobes supraoptic & paraventricular - 1ry capillary plexus of nuclei fenestrated capillaries. a) Acidophils: 1. Stem cells. - Function: - Hypophyseal portal - Somatotrophs 2. Degranulated storage & release of: veins (venules). (GH). chromophils. * Vasopressin (ADH). - 2ry capillary plexus of - 3. Degenerated * Oxytocin. capillaries in Mammotrophs cells. 2. Fenestrated blood adenohypophysis. (Prolactin) capillaries. Increasing 3. Herring Bodies: { Hypophyseal portal during - Are distensions of the axons system } lactation. in pars nervosa. It carries neurohormones ----- ----- ----- - Representing accumulation from median eminence to b) Basophilic: of neurosecretory granules at adenohypophysis. - Thyrotrophs axon termini. (TSH). 4. Pitucytes: - Gonadotrophs Are glial like cells in Pars 2. Inferior Hypoph. Nervosa. (FSH, LH) Arteries (Rt & Lt): - Structure: - Corticotrophs Mainly to pars nervosa, Neumerous cytoplasmic (ACTH). they are NOT process. participating in - Functions: hypophyseal portal Support the axons of pars circulation. nervosa. N.B. NO secretory or neural cells in pars nervosa. Questions A Q1: Identify structure A in the pic: A. Pars Distalis. B. Pars Intermedia. C. Pars Tuberalis. D. Pars Nervosa. Q2: Which one of the following increase during lactation: A. Mammotrophs. B. Somatotrophs. C. Thyrotrophs. D. Gonadotrophs. Q3: Which one of the following supports the axons of the pars nervosa: A. Herring bodies. B. Pitucytes. C. Thyrotrophs. D. Corticotrophs. Q4: the PARS NERVOSA Store & release: A. GH. B. TSH. C. ADH. D. ACTH. Q5: the Hypophyseal Portal System is formed by: A. Superior hypophyseal arteries. B. Inferior hypophyseal arteries. Answers 1 2 3 4 5 D A B C A If you have any questions or suggestions please do not hesitate to contact us on: [email protected] Histology Team Leaders: Nada Alouda Faisal Alshuwair Best of luck! .
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