Transcript 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
---parenchyma: endocrine cells arranged
into nest, cord, cluster or follicle, secrete
hormones
---interstitium: CT, rich in capillaries
* 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
3. Thyroid gland
---largest endocrine gland, 15-40g
---two-lobes, connect to each other by
isthmus
1)
General structure:
---capsule of LCT: insert into parenchyma
to separate them into lobules
---parenchyma: lobules
follicles
interstitium: CT
2)
follicle:
---spherical, 0.02-0.9mm
---epi + colloid
① Epithelium:
simple cuboidal epi
---structure:
LM:
cuboidal:
flattened(inactive)
columnar ( more active)
basophilic cytoplasm
spherical centrally-located N
or
EM:
microvilli
RER, Golgi, secretory granules
lysosome, endocytotic vesicles
---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
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
② Colloid: iodinated thyroglobulin
HE: eosinophilic, homogeneous structure
3)
parafollicular cell
---single between follicular cell
---in small groups in interstitial tissue
---structure:
LM:
/ovoid, polygonal
/larger
/pale-stained: eosinophilic
/argyrophilic granules
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
4. Adrenal gland
---paired, situated on the upper poles of
kidney
---capsule: CT
---cortex: yellow, derived from mesoderm
---medulla: reddish-brown, derived from
neuroectoderm
1) adrenal cortex:
---constitutes 80-90% of total volume
---three zones
①zona glomerulosa: 5-10% of cortex volume
---structure:
LM:
/small, low columnar or polygonal cell
/arranged into nest or cluster
/deep stained
EM:
/steroid-hormone secreting cell feature
/scattered lipid droplets
---function: mineralocorticoid-aldosterone
(reabsorb Na+ and release K+)
② zona fasciculate:
78%
---structure:
LM:
/large, polygonal or columnar cell
/arranged into cords
/appear vacuolated(formy)-empty
EM:
/steroid-secreting cell feature
/more lipid droplets
---function: secret glucocorticoid-cortisol or
corticosterone
/promote protein and fat transfer into
glucose
/impair immune reactive
③ zona reticularis: 7%
---structure:
LM:
/polygonal(hedral), small cell
/arranged into cord to form network
/acidophilic cytoplasm
EM:
/steroid-secreting cell feature
/less lipid droplet and more lipofuscin
pigment
---function: secret androgen(testosterone)
and small amount of oestrogen
2) Adrenal medulla
① medullary cell:
chromaffin cell
---structure:
LM:
/polyhedral, cord
/brownish cytoplasm granules- when fixed by
bichromate-containing fixative
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
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
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
1) The pars distalis
---cell: nest or cord-nitrogenous-hormone
secreting cell feature
---CT: rich in sinusoids
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
ii. mammotroph:
-less, largest granules
-600-700nm
-lactogenic
hormone(LTH)
or
prolactin(PR): promote the growth and
secreting of mammory gland
② basophil:
LM:
less, large cell
ovoid or polygonal
basophilic granules
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)
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
③ chromophobe cell
---structure:
LM:
/more, small, pale
/no clear boundary
EM: less granules
Function:
i. degranulated cell
ii. under-development cell
3) The pars intermedia
---structure:
/chromophobe cell
/basophil
/follicle: simple cuboidal epi. + colloid
*basophil:
melanotroph-melanocyte
stimulating hormone(MSH)
4) Neurohypophysis
a.unmyelinated NF: axons of hypothalamus
cells
*hypothalamus: neuroendocrine cell
supraoptic nucleus
paraventricular nucleus
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
b. pituicyte: special glial cell
irregular with processes
cytoplasm contain pigment granules
function: support and nurish NF
c. capillaries(sinusoid)
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
---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)
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