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Overview of the endocrine system

Learn about the components, characteristics, and functions of endocrine glands, focusing on the thyroid and parathyroid glands as well as the adrenal cortex and medulla. Gain insights into hormone secretion, structure, and related diseases in an overview of endocrinology. |

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Overview of the endocrine system

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  1. Overview of the endocrine system Zhihua Gao

  2. Components of the endocrine system

  3. Characteristics of endocrine glands A. Ductless-Cells are arranged in cord, follicle, aggregation or net-like structure, rich in blood vessels

  4. B. Secrete hormones at a specific time and in small amounts, which act on target organ, tissue or cells. C. The secretion activity is often regulated by other hormones or nerve impulses. D. Make up an endocrine organ, or exist in other organs as tissue or dispersed cells.

  5. Types of endocrine cells 1. Peptide-secreting cells: Well developed Golgi apparatus, RER and secreting granules. Release hormone that chemically contains amino acids.

  6. 2. Steroid-secreting cells: Foamy cytoplasmic appearance under LM. Rich in SER, lipid droplets and MT containing tubular-like cristae. Secrete hormone that chemically contains steroids.

  7. Thyroid The largest endocrine gland in the body. General structure: Fibrous capsule protrudes and divides the parenchyma into lobules containing follicles and rich capillaries.

  8. Epithelium B. Follicle: Colloid is surrounded by singer layer epithelium. 1. Epithelium: Simple squamous (hypoactive), cuboidal or columnar (hyperactive), depending upon the functional status. Function: synthesize and secret throid hormone

  9. Epithelial cells rich in rough RER, Golgi, secreting granules, microvilli, phagosomes, LYS, iodide pump, and receptors for thyrotropin (TSH).

  10. Epithelium Parafollicular cells 2. LCT around follicles (滤泡旁结缔组织):Rich incapillaries. Parafollicular cells: Situated often in groups among follicles, or among follicular epithelium cells but are not adjacent to colloid. Argyrophilic.Lightly stained. Rich in RER and secretory granules. Secrete calcitonin, which can decrease the blood Ca2+ level by inhibiting the activity of osteoclasts.

  11. colloid Epithelium Parafollicular cells Colloid (胶质): Homogeneous secretion of epithelium. Acidophilic and PAS (+). Contains iodated thyroglobulin (碘化的甲状腺球蛋白).

  12. 甲状腺激素的合成与分泌 摄碘 碘化甲状腺球蛋白-储存 重吸收 碘化 溶酶体 分泌小泡 胶质小泡 合成甲状腺球蛋白 摄取氨基酸 Ｔ4 Ｔ3

  13. Formation of triiodothyronine (T3) &tetraiodothyronine (T4):

  14. Function of thyroid hormones (T3, T4) a. elevates the basal metabolic rate. b. influence the body growth and nervous system development during fetal life. Modulation of T3, T4 secretion: hypothalamus-pituitary-thyroid axis.

  15. 甲状腺素分泌的影响因素 • 外界因子作用 主要是抑制碘的吸收、转运和浓缩和活化各个过程。 • 高碘 过氧化物酶的功能过多的被占用，影响酪氨 酸氧化，因而碘的有机化过程受阻，甲状腺代偿性肿大。 • 遗传与免疫 过氧化物酶、去卤化酶的缺陷及碘酪氨酸偶联缺陷等。

  16. Thyroid related diseases

  17. 克汀病或呆小症（cretinism） 由于地方性缺碘，在胎儿和婴儿期从母体获得或合成甲状腺素不足或缺乏，导致生长发育障碍，表现为大脑发育不全、智力低下、表情痴呆，骨形成及成熟障碍，四肢短小，形成侏儒。

  18. 甲 状 腺 功 能 亢 进

  19. 成龙赴台湾宣传新片 承认自己患甲状腺肿瘤

  20. Parathyroid gland Chief cells (主细胞)：HE切片上呈圆形或多边形，胞质着色浅，合成、分泌甲状旁腺激素(parathyroid hormones)，增强破骨细胞的溶骨作用，促进骨盐溶解刺激骨细胞性溶骨，升高血钙。 嗜酸性细胞(oxyphil cell)，功能不清。

  21. Adrenal gland (肾上腺)

  22. Cortex: 3 layers are not sharply defined. Cells in cortex produce and release steroid-like hormone only upon demand. Zona glomerulosa(球状带) Zona fasciculata (束状带) Zona reticularis (网状带) Medulla-Centrally located, derived from ectoderm and surrounded by mesoderm-derived cortex and fibrous capsule.

  23. 球状带分泌盐皮质激素， 促进肾脏远曲小管和集合管吸钠排钾。 盐皮质激素的分泌受肾素-血管紧张素系统的调控。 1. Zona glomerulosa (球状带): Cells (quite small) are arranged in clusters beneath the capsule. The secretion, the mineralocorticoids (盐皮质激素) (e.g. aldosterone), participates in electrolyte balance regulation. Its secretion activity is regulated by renin-angiotensin system.

  24. 束状带分泌糖皮质激素，包括皮质醇和皮质酮，束状带分泌糖皮质激素，包括皮质醇和皮质酮， 促进糖异生，降低免疫反应炎症。 2. Zona fasciculata (束状带): Constitutes ~78% of the cortex. Cells are bigger than those in other zones in the adrenal gland. The typical steroid-secreting cells in the body are arranged in straight cords, and run perpendicularly to the capsule, with rich capillaries among them.

  25. Their glucocorticoids release (e.g. Cortisol & Corticosterone), which is regulated by ACTH, influences the protein, fat and carbohydrate metabolism, and impairs the immune responses.

  26. 3. Zona reticularis: Adjacent to medulla with obscure outline. Cells are arranged in net-like structure and contain more lipofuscin pigment granules. 网状带分泌雄激素、少量糖皮质激素和雌激素

  27. B. Medulla: Big medulla cells-also called chromaffin cells (嗜铬细胞) contain chromaffic granules- in the cytoplasmwhen fixed by chromaffic salt. Cells are arranged in cords or clusters, interwined by capillaries.

  28. Ganglion cells Epinephrine(肾上腺素)-secreting cells and norepinephrine(去甲肾上腺素)-secreting cells secrete adrenaline/epinephrine and noradrenaline/norepinephrine, respectively. The cytoplasm contains central vein and sympathetic ganglion.

  29. The hormones, the adrenaline and noradrenaline, which are stored in granules and whose secretion is stimulated by innervating sympathetic nerve, can immediately elevate the heart beating rate and blood pressure, respectively.

  30. Hypophysis/the pituitary gland Weight0.5g. Most important endocrine gland.

  31. General structure • Adenohypophysis (腺垂体) • pars distalis (anterior lobe) • pars tuberalis • pars intermedia. • 2. Neurohypophysis (神经垂体) • pars nervosa (constitute the posterior lobe, together with pars intermedia) + infundibulum. 正中隆起 结节部 漏斗柄 远侧部

  32. B. Adenohypophysis: 1. Pars distalis: Aggregated cells are surrounded by sinusoidal Caps, the secondary Cap network of hypophyseal portal circulation. a. acidophilic cell: 40%. Contains acidophilic secreting granules. The secretions are peptides. 2 types: * somatotrophic cell: secretes somototropin (GH), which can stimulate the growth of bone, muscles and CT, etc. Lack of GH in childhood results in midget. *mammotrophic cell: secretes prolactin, which can stimulate the development of mammary glands.

  33. 其实所有身高超过2米10以上的人都存在着出现这种病症的危险，姚明也曾经处于“腺脑垂体分泌生长激素过多症”的威胁，但是他在身体尚未完全发育好的时候，已经采用了当时最先进的药物控制，所以现在已经基本上不需要再担心。其实所有身高超过2米10以上的人都存在着出现这种病症的危险，姚明也曾经处于“腺脑垂体分泌生长激素过多症”的威胁，但是他在身体尚未完全发育好的时候，已经采用了当时最先进的药物控制，所以现在已经基本上不需要再担心。

  34. 垂体前叶功能低下： 垂体性侏儒症（pituitary dwarfism）：指因垂体前叶分泌生长激素部分或完全缺乏所致儿童期生长发育障碍性疾病，表现为骨骼躯体生长发育迟缓，体型停滞于儿童期，身材矮小，皮肤和颜面可有皱纹，常伴性器官发育障碍，但智力发育正常。

  35. b. basophilic cell: 10%. Larger, containsbasophilic and PAS (+) secreting granules. The secretions are glycoproteins. 3 types: * thyrotropic cell: secretes thyrotropin (TSH). * corticotropic cell: secretes corticotropin (ACTH) * gonadotropic cell: secretes gonadotropin, which includes follicle-stimulating hormone (FSH) that can stimulate the formation of oocyte and sperm, and luteinizing hormone (LH) that can stimulate the release of sex hormone. c. chromophobe: 50%. Smaller and inactive.

  36. 2. Pars intermedia (中间部): Contains follicles. Functions unknown. 3. Pars tuberalis (结节部): Secretes gonadotropin. C. Neurohypophysis (神经垂体): 1. Pars nervosa (神经部): a. pituicytes: specific glial cells.

  37. b. unmyelinated nerve fibers: are the axons of neurons, whose cell bodies locate in paraventricular and supraoptic nuclei in hypothalamus. The axon dilations, the Herring Bodies, are light acidophilic and contain many secretory granules occupied by peptide-containing hormone. The oxytocin, which is produced by paraventricular nuclei, can shrink smooth muscles in uterus when parturition. The antidiuretic hormone (ADH, vasopressin), which is produced by supraoptic nuclei, can facilitate water re-absorption in kidney.

  38. 2. Infundibulum: Composed of median eminence and neural stalk. Contains primary Cap network of hypophyseal portal circulation.

  39. D. Regulation of hormone release in pars distalis: a. the neuroendocrine cells in hypothalamus and endocrine cells in pituitaryare functionally connected by hypophyseal portal circulation.

  40. The neurons in tuberal nuclei in hypothalamus can produce releasing and inhibiting hormone, which are released into the infudibulum, where the primary Cap network of hypophyseal portal circulation exists. b. positive and negative feedback.

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