Endocrine System

李立仁 副教授 解剖學暨細胞生物學科 基醫大樓六樓 617室 [email protected] Endocrine glands - Ductless - Rich vascular supply - Fenestrated capillaries

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https://www.organiclifestylemagazine.com Pituitary gland

- Two lobes of different origins - Anterior lobe: -- stimulated by tropic from the -- hypophyseal portal system - Posterior lobe: -- neural tissue that release hormones produced by the hypothalamus

17-5 www.vivo.colostate.edu/.../hy popit/sagpitbig.jpg Anterior lobe (adenohypophysis) Glandular epithelial tissue

Pituitary gland www.vivo.colostate.edu/.../hy popit/sagpitbig.jpg Posterior lobe (neurohypophysis) Neural secretary tissue

Pituitary gland Pituitary gland Development Pituitary gland Blood supply

Hypothalamic neurons

Nerve ending in primary capillary network

Hypothalmo- hypophyseal portal circulation (portal vein)

Secondary capillary network in adenohypophysis Anterior lobe of pituitary gland Three subdivisions: Pars distalis (pars infundibularis) Secret: Growth (somatotropes) Prolactin (lacto/mammotropes) ACTH (corticotropes) FSH, LH (gonadotropes) TSH (thyrotropes) Pars Distalis Anterior lobe of pituitary gland Cell Cord / sinusoids (capillaries) Chromophils ( ) and Chromophobes ( ) Pars Distalis Anterior lobe of pituitary gland Classification of cell types Histochemical features: Basophils (15%), acidophils (35%) and chromophobes (50%), or periodic-acid-Schiff reagent (PAS) for glycoproteins Immunocytochemical features: Specific antibody to each hormone or key molecule EM features: Size/shape of granules, cell shape, organelles, nuclear features Pars Distalis Anterior lobe of pituitary gland HE: acidophils (red) , basophils (blue) , chromophobes Pars Distalis Anterior lobe of pituitary gland Cell types Acidophils (35%): Somatotrope (GH), Lactotrope/Mammotrope (prolactin, PRL) Basophils (15%): Corticotropes (ACTH), Gonadotrope (FSH, LH), Thyrotrope (TSH), Chromophobes (50%): Cells without secretory granules (follicular cells, stellate cells) and/or degranulatedcells Pars Distalis Anterior lobe of pituitary gland

Immunohistochemistry

Cells in the sections

Rabbit anti-LH Ab

Peroxidase-goat anti-rabbit IgG

Substrate reaction

Immunohistochemistry for LH Pars Distalis Somatotropes Acidophilic Densely packed granules (350 nm) Produce growth hormone (somatotropin) Enhance body growth - dwarfism - gigantism - acromegaly

Stimulated by exercise 17-16 Pars Distalis Lactotropes Acidophilic Small granules (200 nm) at rest and enlarged (600 nm) during pregnancy and Produce prolactin Promote mammary development and lactation in female Play roles in paternal behaviors and reproductive functions in male

17-17 Pars Distalis Corticotrope Basophilic Granules of variable size (100-300 nm) Produce ACTH and related peptides Control the secretion of glucocorticoids

17-18 Pars Distalis Gonadotrope Basophilic Granules of intermediate size (200-250 nm) and varied electron density Produce follicle-stimulating hormone (FSH) and (LH) In female: FSH initiates the development of ovarian follicles and LH triggers ovulation In male: FSH stimulates sperm production and LH triggers testosterone secretion 17-19 Pars Distalis Thyrotropes Basophilic Small granules (<150 nm) Produce thyroid- stimulating hormone Stimulates follicular cells to produce thyroxine (T4) and triiodothyronine (T3) Feedback regulated by thyroid function

https://www.semanticscholar.org/paper/Two-types-of-thyrotropes-(TSH-cells)-in-the- of-the-Iwama-Hasegawa/5cf428720f0b69c98896cf286d36f9c566958e21/figure/317-20 Pars Distalis Anterior lobe of pituitary gland Pars Intermedia Anterior lobe of pituitary gland Intermediate lobe

Isamine blue /eosin Contains basophils and chromophobes Basophils extend into pars nervosa Unclear function in humans Anterior lobe of pituitary gland Pars tuberalis Highly vascular Clusters of basophils (ACTH, LH, FSH)

www.vivo.colostate.edu/.../pitgranules.jpg Posterior lobe of pituitary gland

Three subdivisions: Median eminence Infundibular stem Pars nervosa

Secret: (ADH)

17-24 Pars nervosa Posterior lobe of pituitary gland Posterior lobe of pituitary gland

Pituicytes (neuroglial cells): irregular cell shape with many branches, oval nucleus, possess glial fibrillar acidic protein (GFAP) intermediate filaments Unmyelinated nerve fibers Axons containing neurosecretory granules Fenestrated capillaries Fibroblasts, mast cells Pars nervosa Posterior lobe of pituitary gland

Nerve fibers

Pituicytes Neurosecretory granules Axons from supraoptic and paraventricular nuclei form the hypothalamo-hypophyseal tract. Neurosecretory granules () contain oxytocin, vasopressin (ADH), and carrier proteins. Pars nervosa Posterior lobe of pituitary gland

Pituicytes

Secretions are released to fenestrated capillary ( ) via exocytosis. Oxytocin and ADH neurons Pars nervosa Posterior lobe of pituitary gland Herring bodies The dilated portions of the axons due to the accumulation of secretory granules. Pars nervosa Posterior lobe of pituitary gland

Fenestrated capillary

Also called epiphysis or the "third eye" Covered by pia mater (CT)) Septa----lobulation----lobules Parenchyma 1. 2. Glial cells (interstitial cells) 3. sand () Pineal gland

H&E Pineal gland Cell types Pinealocytes: 95% cell ratio, large pale cells with well developed rER, sER, Golgi apparatus, mitochondria, expanded, club-like (bulbous) ending associated with capillaries Neuroglial cells (interstitial cells): 5% cell ratio, dark stellate cells with long cell processes Pineal gland Pinealocytes have bulbous expansions Pineal gland Brain sand (corpora arenacea) Recognizable in childhood and increase in number with age X-ray opaque, as midline marker in radiograpophic and computer tomography studies Precipitations of phosphates and carbonates on carrier proteins Goals of this class 1. Understand the differences between endocrine and exocrine glands. 2. Recognize sinusoids and cell cords in the gland. 3. Indentify acidophils, basophils and chromophobes in H&E stained sections of ant. p-gland. 4. Appreciate the cytoarchetecture of the post. p-gland. 5. Know the features of herring bodies in post. p-gland. 6. Comprehend the histological organization of the pineal gland. Thyroid gland

Capsule - septa - lobules Thyroid follicles Follicular lumen containing colloids (thyroglobulin/T3, T4) Parafollicular cells (C cells): Calcitonin, lowers circulating Ca 2+ levels Fenestrated capillaries Thyroid gland Lobulation Thyroid gland Follicles

Capillary network around the follicles Thyroid gland Follicular cells Synthesis and Secretion of T3 and T4

Thyroglobulin/rER

Iodine peroxidation

Iodinated thyroglobulin stored in the follicular lumen

Endocytosis

Lysosomal action

Release of T3, T4 into blood capillaries Follicular cells Thyroid gland

Inactive

Active Thyroid gland Parafollicular cells (calcitonin-producing, C cells) Parafollicular cells of the thyroid gland are located within thyroid follicles between the basal aspects of the follicular cells and the basement membrane of the follicle or are present in a parafollicular position. Parafollicular cells (C cells) Thyroid gland Parafollicular cells (C cells)

Calcitonin – lowering by Ca 2+ levels by stimulating osteoblasts to take Ca 2+ out of the circulation and inhibiting the bone resorption by osteoclasts.

instruction.cvhs.okstate.edu/.../hrendo7.jpg

Capsule - septa - anastomosing cell cords Principal (chief) cells: Product PTH that elevates blood Ca 2+ level Oxyphil cells: large cells with many mitochondria (esoinophilia) Parathyroid gland

http://www.nku.edu/~dempseyd/THE_ENDOCRINE5.htm 17-47 Parathyroid gland Principal (chief) cells Oxyphil cells Oxyphil cells

Principal (chief)17-48 cells Oxyphil cells Principal (chief) cells Parathyroid gland

pathology.mc.duke.edu Principal (chief) cells Parathyroid gland

PTH -- elevates blood Ca 2+ level by promoting Ca 2+ release from bone (activate osteoclasts) and Ca 2+ reabsorption from kidney and intestine.

instruction.cvhs.okstate.edu/.../hrendo7.jpg Principal (chief) cells Parathyroid gland Oxyphil cells Parathyroid gland Blood supply Cortex (15%) Zona fasculata (80%) (5%) Medulla Chromaffin cells Ganglion cells Adrenal gland Adrenal gland Blood circulation Suprarenal arteries

Subcapsularplexus

Short cortical arterioles

Cortical sinusoidal system

Sinusoidal system in medulla

Central vein Adrenal gland Blood circulation Suprarenal arteries

Subcapsularplexus

Long cortical arterioles

Capillary networks in medulla

Central vein Cortex Adrenal gland Zona glomerulosa Upper zone Columnar cells arranged as balls Acidophilic cytoplasm: sER, mitochondria with tubular cristae Secrete mineralocorticoids (aldosterone) Cortex Adrenal gland Steroidogenic cells

Mitochondria with tubular cristae Cortex Adrenal gland Cells arranged into long straight columns Secrete glucocorticoids Spongiocytes Cytoplasm containing many mitochondria, sER and lipid droplets Zona fasciculata Adrenal gland

Spongiocytes in zona fasciculata

Reticular fiber staining Zona fasciculata Adrenal gland Zona reticularis Cell cords in anastomosing network (anatomosing sinusoids) Secrete glucocorticoids and androgens Acidophilic cytoplasm: Lipid droplets, mitochondria, rER, lipofuscin (lipofuchsin) pigments Zona reticularis Adrenal gland Medulla Adrenal gland Adrenal cortex Adrenal medulla Medulla Adrenal gland Medulla Adrenal gland Cell types

Glandular (chromaffin) cells: Modified postganglionic neurons Innervated by preganglionic sympathetic fibers Contain catecholamine granules reacted with chrome solution --- brown granules Fenestrated capillaries Medulla Adrenal gland

Zona reticularis

Chromaffin cells Medulla Adrenal gland Chromaffin cells Medulla Adrenal gland Chromaffin cells Medulla Adrenal gland Ganglionic cells Postganglionic neurons that innervate blood vessels Medulla Adrenal gland Ganglionic cells

reference.findtarget.com Adrenal gland Goals of this class 1. Note the cytoarchetecture of the thyroid and parathyroid glands. 2. Identify follicular and parafollicular cells in the thyroid gland 3. Characterize chief cells and oxyphil cells in H&E stained sections of parathyroid gland.

17-74 Goals of this class

4. Discern the pathways of blood supply in the adrenal gland. 5. Know the features of steroidogenic cells. 6. Identify the cortex and medulla of adrenal gland based on their histological characteristics. 7. Recognize the zones in adrenal cortex. 8. Distinguish the cell types in the adrenal medulla.