Chapter 12 Endocrine System

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Chapter 12 Endocrine System
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• 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

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

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• 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

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3. Thyroid gland

• ---largest endocrine gland, 15-40g
• ---two-lobes, connect to each other by isthmus

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

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• 2)      follicle
• ---spherical, 0.02-0.9mm
• ---epi colloid

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

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• EM
• microvilli
• RER, Golgi, secretory granules
• lysosome, endocytotic vesicles

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• ---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

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• 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

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• ? Colloid iodinated thyroglobulin
• HE eosinophilic, homogeneous structure

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

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• 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

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4.   Adrenal gland

• ---paired, situated on the upper poles of kidney
• ---capsule CT
• ---cortex yellow, derived from mesoderm
• ---medulla reddish-brown, derived from
  neuroectoderm

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• 1) adrenal cortex
• ---constitutes 80-90 of total volume
• ---three zones

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• ?zona glomerulosa 5-10 of cortex volume
• ---structure
• LM
• /small, low columnar or polygonal cell
• /arranged into nest or cluster
• /deep stained

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

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• ?   zona fasciculate
• 78
• ---structure
• LM
• /large, polygonal or columnar cell
• /arranged into cords
• /appear vacuolated(formy)-empty

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

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• ?  zona reticularis 7
• ---structure
• LM
• /polygonal(hedral), small cell
• /arranged into cord to form network
• /acidophilic cytoplasm

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

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• 2) Adrenal medulla
• ?     medullary cell
• chromaffin cell
• ---structure
• LM
• /polyhedral, cord
• /brownish cytoplasm granules- when fixed by
  bichromate-containing fixative

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• 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

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

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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

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

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• ? 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

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

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• ?    basophil
• LM
• less, large cell
• ovoid or polygonal
• basophilic granules

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• 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)

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• 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

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

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

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

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• 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

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

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• 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

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• ---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)

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• 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