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Chapter 12 Endocrine System

Chapter 12 Endocrine System. 1. Components : ---small gland or endocrine cell: islet of pancreas and corpus luteum ---endocrine gland: Thyroid gland Parathyroid gland Adrenal gland Pituitary gland(hypophysis) Pineal body. 2. General structure ---capsule: CT

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Chapter 12 Endocrine System

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  1. Chapter 12 Endocrine System

  2. 1.Components: ---small gland or endocrine cell: islet of pancreas and corpus luteum ---endocrine gland: • Thyroid gland • Parathyroid gland • Adrenal gland • Pituitary gland(hypophysis) • Pineal body

  3. 2.General structure ---capsule: CT ---parenchyma: endocrine cells arranged into nest, cord, cluster or follicle, secrete hormones ---interstitium: CT, rich in capillaries

  4. * According to hormones ---nitrogenous-hormone secreting cell: • RER • Golgi • secretory granules ---steroid-hormone secreting cell: • SER • mitochondria: with tubular-vesicular cristae • lipid droplet: raw materials

  5. 3. Thyroid gland ---largest endocrine gland, 15-40g ---two-lobes, connect to each other by isthmus

  6. 1)General structure: ---capsule of LCT: insert into parenchyma to separate them into lobules ---parenchyma: lobules • follicles • interstitium: CT

  7. 2)follicle: ---spherical, 0.02-0.9mm ---epi + colloid

  8. ① Epithelium: simple cuboidal epi ---structure: LM: • cuboidal: flattened(inactive) or columnar ( more active) • basophilic cytoplasm • spherical centrally-located N

  9. EM: • microvilli • RER, Golgi, secretory granules • lysosome, endocytotic vesicles

  10. ---function: synthesize and release thyroid hormones • thyroxine(T4) • triiodothyronine(T3) a. processes: i.synthesis of thyroglobulin ii.Iodination of thyroglobulin iii.Release of thyroid hormones

  11. b. function of thyroid hormones • increase the basal metabolism rate • promote the cell growth • raise body temperature • increase heart rate • play a role in foetal and neonatal development of CNS

  12. ② Colloid: iodinated thyroglobulin HE: eosinophilic, homogeneous structure

  13. 3)parafollicular cell ---single between follicular cell ---in small groups in interstitial tissue ---structure: LM: /ovoid, polygonal /larger /pale-stained: eosinophilic /argyrophilic granules

  14. EM: /nitrogenous-hormone secreting cell feature /granules: contain calcitonin ---function: i. secret calcitonin to promote activity of osteoblast and suppressing the absorption of Ca++ in gastrointestinal tract and renal tubule ii. secret calcitonin gene related peptide, CGRP(act upon heart and small BV) and somatostatin

  15. 4.Adrenal gland ---paired, situated on the upper poles of kidney ---capsule: CT ---cortex: yellow, derived from mesoderm ---medulla: reddish-brown, derived from neuroectoderm

  16. 1) adrenal cortex: ---constitutes 80-90% of total volume ---three zones

  17. ①zona glomerulosa: 5-10% of cortex volume ---structure: LM: /small, low columnar or polygonal cell /arranged into nest or cluster /deep stained

  18. EM: /steroid-hormone secreting cell feature /scattered lipid droplets ---function: mineralocorticoid-aldosterone (reabsorb Na+ and release K+)

  19. ②zona fasciculate: 78% ---structure: LM: /large, polygonal or columnar cell /arranged into cords /appear vacuolated(formy)-empty

  20. EM: /steroid-secreting cell feature /more lipid droplets ---function: secret glucocorticoid-cortisol or corticosterone /promote protein and fat transfer into glucose /impair immune reactive

  21. ③zona reticularis: 7% ---structure: LM: /polygonal(hedral), small cell /arranged into cord to form network /acidophilic cytoplasm

  22. EM: /steroid-secreting cell feature /less lipid droplet and more lipofuscin pigment ---function: secret androgen(testosterone) and small amount of oestrogen

  23. 2) Adrenal medulla ①medullary cell: chromaffin cell ---structure: LM: /polyhedral, cord /brownish cytoplasm granules- when fixed by bichromate-containing fixative

  24. EM: /electron-dense granules: • adrenaline cell: 80% i.increase the heart rate ii.dilate BV • noradrenaline cell: 20% i.increase blood pressure ii.increase the flow speed of blood

  25. Function: i.secrete adrenaline and noradrenaline ii.secrete some polypeptides(galanin, neuropeptide Y, enkephalin) ② ganglial cell: polypolar neurons- large, 2-3 in groups ③ central vein

  26. 4.Pituitary gland ---ovoid, flattened organ, 0.5X1X1cm, 0.5g in weight, in pituitary fossa of sphenoid bone ---capsule: CT ---adenohypophysis: • the pars distalis • the pars intermedia • the par tuberalis ---neurohypophysis: • the pars nervosa • infundibular stalk

  27. 1) The pars distalis ---cell: nest or cord-nitrogenous-hormone secreting cell feature ---CT: rich in sinusoids

  28. ① acidophil: 40% LM: • round, ovoid • eosinophilic g EM: According to granules i.somatotroph: -filled with round, electron-dense granules -350nm -somatotropic hormone(STH) or growth hormone(GH): promote the growth and metabolism of bone

  29. ii.mammotroph: -less, largest granules -600-700nm -lactogenic hormone(LTH) or prolactin(PR): promote the growth and secreting of mammory gland

  30. ②basophil: LM: • less, large cell • ovoid or polygonal • basophilic granules

  31. EM: according to granules • i.thyrotroph: -less, round, smallest granules -150-200 nm, peripheral distributed -thyroid stimulating hormone(TSH) • ii.corticotroph: -round, less, different electron density -200-250nm, under plasmalemma -adrenocorticotropic hormone(ACTH) -lipotropin, or lipotrophic hormone(LPH)

  32. iii.gonadotroph -medium-sized, round granules -200-300 nm -follicle stimulating hormone(FSH): • Female: development of ovarian follicle • Male: spermatogenesis in testis -luteinizing hormone(LH): • Female: ovulation and formation of corpus luteum, secretion of progesterone • Male: interstitial cell-stimulating hormone(ICSH), regulate the secretion of androgen by Leydig cell in testis

  33. ③chromophobe cell ---structure: LM: /more, small, pale /no clear boundary EM: less granules Function: i.degranulated cell ii.under-development cell

  34. 3) The pars intermedia ---structure: /chromophobe cell /basophil /follicle: simple cuboidal epi. + colloid *basophil: melanotroph-melanocyte stimulating hormone(MSH)

  35. 4) Neurohypophysis a.unmyelinated NF: axons of hypothalamus cells *hypothalamus: neuroendocrine cell • supraoptic nucleus • paraventricular nucleus

  36. secrete: antidiuretic hormone (ADH) (vasopressin) increasing reabsorption of water in renal tubule and causing the constriction of arterioles to increase blood pressure *Herring bodies: LM: acidophilic, irregular structure EM: axon where dilated portion with secreting granules accumulate in

  37. b. pituicyte: special glial cell • irregular with processes • cytoplasm contain pigment granules • function: support and nurish NF c. capillaries(sinusoid)

  38. 5) Relationship between hypothalamus and adenohypophysis, and hypophyseal portal system ---arcuate nucleus of hypothalamus: /neuroendocrine cell: • secrete releasing hormone(RH)-GRH,PRH,TRH,GnRH,CRH,MSRH • secrete release inhibition hirmone(RIH)-SOM, PIH, MSIH • their axons end in infundibular stalk and release hormones into primary capillaries

  39. ---hypophyseal portal system: • Superior hypophyseal arteries(arisig from the cerebral arterial circle)→primary capillary plexus(infundibular stalk) →hypophyseal portal veins→secondary capillary plexus(the pars distalis) →vein sinusoids(small vein)

  40. 6. diffuse neuroendocrine system,DNES ---scattered single endocrine cells /synthesize and secrete amine-amine precursor uptake and decarboxylation cell, APUD cell /also secrete peptide /secretions are secreted by neurons-so called DNES ---components: /cells of hypothalamus and hypophysis /endocrine cells of digestive tract, respiratory system, pancreas and so on /parafollicular cell of thyroid gland and medullary cell of adrenal gland

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