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unit 15 Flashcards

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1
Q

what are endocrine glands

A

tissues in which hormone secreting cells make up most of the parenchyma

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2
Q

where are hormones exerting endocrine action released

A

into the interstitial and then enter the blood stream for transport

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3
Q

where are aggregates of secretory cells embedded

A

in highly vascularized CT, no ducts are associated with secretory cells

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4
Q

what is different about secretory cells

A

resemble epithelial cells but lack free surface

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5
Q

how are secretory cells usually arranged

A

into cords or clusters and surrounded by an extensive capillary network

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6
Q

where are secretory cells derived from

A

most from CNS, neural crest, or gut tube epithelium, a few have mesenchymal origin

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7
Q

what are the four types of hormones

A

glycoproteins (mostly water-soluble)
protein or peptide (water)
amino acid derivatives (water)
steroids (lipid)

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8
Q

anterior pituitary

A

composed of glandular, densely packed epithelium
derived from ectoderm
stains darkly
not directly attached to the hypothalamus
aka adenohypophysis

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9
Q

posterior pituitary

A

composed of neural secretory tissue
derived from neuroectoderm
less cellular, appears streaky, stains lightly
directly attaches to the hypothalamus
aka neurohypophysis

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10
Q

pituitary development

A
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11
Q

regions of the posterior pituitary

A

pars nervosa - larger portion
infundibulum - continuous with median eminence

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12
Q

anterior pituitary regions

A

pars distalis
pars intermedia
pars tuberalis

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13
Q

pars distalis

A

bulk of anterior pituitary, arises from thickened anterior wall of Rathke’s pouch
composed of strongly staining secretory cells surrounded by fenestrated capillaries and minimal CT with reticular fibers

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14
Q

pars intermedia

A

thin remnant of posterior wall of Rathke’s pouch, abuts the pars distalis

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15
Q

pars tuberalis

A

sheath of tissue around infundibulum, developed from thickened lateral wall of Rathke’s pouch

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16
Q

what are the 3 cell types found in pars distalis

A

acidophils (40%), basophils (10%), chromophobes (50%)

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17
Q

what are chromophobes

A

heterogeneous group of cells including stem/progenitor cells and degranulated acidophils & basophils

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18
Q

what are the two types of acidophils

A

somatotrophs and lactotrophs

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19
Q

somatotrophs

A

secrete somatotropin (aka GH)
GH increases metabolic rate, induces liver to produce insulin-like growth factor 1 (IGF-1), stimulate bone and muscle growth

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20
Q

what affects somatotrophs

A

stimulated by GHRH, inhibited by somatostatin

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21
Q

lactotrophs

A

secrete prolactin
promotes androgen secretion in males and mammary gland development/lactation in female
large polygonal cells with oval nuclei

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22
Q

what affects lactotrophs

A

no dedicated releasing hormone, various factors promote secretion though
dopamine inhibits secretion

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23
Q

what do acidophils contain

A

cytoplasmic secretory vesicles containing peptide! hormone product

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24
Q

what are the 3 types of basophils

A

corticotrophs, gonadotrophs, thyrotrophs

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25
corticotrophs
synthesize POMC, precursor to ACTH ACTH stimulates synthesis & release of hormones from adrenal cortex
26
what affects corticotrophs
secretion stimulated by CRH, inhibited by high plasma cortisol levels
27
gonadotrophs
secrete FSH and LH stimulate follicle growth, ovulation, sex hormone production
28
gonadotrophs location
small oval cells with round eccentric nuclei, scattered throughout pars distalis
29
what affects gonadotrophs
secretion stimulated GnRH, inhibited by high plasma levels of sex hormones
30
thyrotrophs
secrete thyrotropin (TSH), acts on follicular cells of the thyroid gland to stimulate production of thyroid hormones
31
what affects thyrotrophs
secretion stimulated by TRH, inhibited by high plasma thyroid hormone levels
32
pars intermedia
contains colloid-filled cysts (Rathke cysts) lined by cuboidal cells and clusters of basophil-like cells
33
what are Rathke cysts
remnants of Rathke pouch
34
pars tuberalis
highly vascular area containing large vessels if the hypothalamohypophyseal portal system with associated small clusters/cords of cells associated with BVs contains nests of squamous cells and small follicles lined by cuboidal cells
35
what does the superior hypophyseal portal system supply directly
pars tuberalis, infundibulum, median eminence (contains termini of neurosecretory neurons producing releasing inhibitory hormones
36
what does the superior hypophyseal artery form
primary fenestrated capillary plexus
37
where does the primary capillary plexus drain
hypophyseal portal veins
38
what do hypophyseal portal veins form
secondary capillary plexus in pars distalis
39
what surrounds acidophils, basophils, chromophobes
fenestrated capillaries
40
what acts on pars distalis
releasing/inhibitory hormones
41
where does the secondary capillary plexus drain
into hypophyseal veins
42
is the posterior lobe of pituitary an endocrine gland
NO
43
what is the infundibulum continuous with? what does it contain?
median eminence axons of hypothalamic neurosecretory cells traveling as hypothalamic hypophyseal tract
44
what does the pars nervosa contain
axons and termini of hypothalamic neurosecretory cells; axons terminate near capillaries of capillary plexus of nervosa
45
where are peptide hormones produced? what is well developed in these cells?
in supraoptic nucleus and paraventricular nucleus cell bodies Nissl bodies are well developed
46
where are peptide hormones packed into? how are they transported?
into secretory granules transported along axons and stored near and at axon termini in pars nervosa
47
what are accumulations of secretory granules in the pars nervosa seen as
visible distentions, Herring or neurosecretory bodies, along axons and at termini axons appear as streaks
48
what are Herring bodies
groups of secretory vesicles containing granules of antidiuretic hormone (vasopressin) or oxytocin
49
what are pituicytes
neuroglia cells that surround and support axons extending from hypothalamus most abundant in pars nervosa have round/oval nucleus irregularly shaped cells with many branches
50
antidiuretic hormone or vasopressin
increases permeability of collecting tubules to water and has an arteriolar vasoconstrictive action mediated by cAMP
51
where does pars nervosa receive blood from? what do these arteries form?
inferior hypophyseal and trabecular arteries capillary plexus in pars nervosa
52
how do hormones released by Herring bodies enter the blood circulation
through capillary plexuses of inferior hypophyseal and trabecular arteries
53
where does the pineal gland develop from
neuroectoderm of the posterior roof of diencephalon and remains attached via a small stalk
54
what does the pineal gland do
relates light intensity/duration to endocrine activity, regulates circadian rhythm produces melatonin
55
what covers the pineal gland
capsule of pia mater CT trabeculae extend from capsule into substance of gland, divide into lobules
56
pinealocytes
melatonin producing cells, arranged in clumps/cords within lobules
57
interstitial glial cells
closely resemble astrocytes, have elongated nuclei that stain more heavily the pinealocytes found in perivascular areas and between groups of pinealocytes
58
corpora arenacea
brain sand calcified concretions
59
thyroid gland structure
2 lobes connected via isthmus, surrounded by thin fibrous capsule which send septa deeply into gland
60
hormones produced by thyroid
thyroid hormones T3, T4- control basal metabolic rate calcitonin - helps regulate calcium and phosphate metabolism
61
thyroid follicle
spherical, cyst like structures lined by simple epithelium (follicular epithelium) structural and functional unit of thyroid
62
what surrounds each follicle
a thin layer of CT containing fenestrated capillaries, epithelium ranges from cuboidal to low columnar
63
what is colloid
gel-like material in center of follicle T3 and T4 bound to thyroglobulin, a glycoprotein that is most abundant component of colloid
64
how does the thyroid store its secretory products
extracellularly
65
colloid volume/follicle size...
inversely correlated with follicle activity
66
thyroid follicular cells
synthesize and secrete T4 and T3 in response to TSH from pituitary
67
thyroid follicular cell structure
apical surface lines follicular lumen, in contact with colloid basal surface rests on basal lamina adjacent to surrounding CT lateral surface contains tight junctions range from squamous to low cuboidal/columnar abundant vesicles at apical surface and in apical cytoplasm
68
where do cells reabsorb colloid? secrete T3/T4?
apical surface basal surface
69
thyroid follicular cells at EM level
apical rER, supranulcear golgi apical microvilli colloid resorption droplets many lysosomes
70
where are parafollicular cells located
found at periphery of follicle in interfollicular stroma, individually or in small clusters
71
what do parafollicular cells contain
small, dense secretory granules containing calcitonin
72
what is calcitonin secretion stimulated by
directly by high levels of calcium in blood, acts to decrease calcium concentration in blood
73
parathyroid glands
4 glands embedded in posterior thyroid, encased in thin capsule which invaginates creating poorly defined lobules
74
how are parathyroid cells organized
into cords/clusters surrounded by reticular fibers, BV, lymphatics, nerves
75
what do parathyroid cells secrete
parathyroid hormone, maintains optimal concentrations Ca in blood and interstitial fluid stimulated by declining serum calcium levels released by exocytosis
76
oxyphil cells
round large cells with relatively smaller nucleus, acidophilic cytoplasm found singly or in clusters function unclear
77
adrenal glands
paired organs covered with dense CT capsule parenchyma composed of secretory cells, stroma mostly reticular fibers, fibroblasts, microvasculature
78
adrenal cortex
originates from mesoderm, parenchymal cells synthesize and secrete steroid hormones
79
adrenal medulla
derived from neural crest produced catecholamines
80
3 concentric zones of adrenal cortex
zona glomerulosa zona fasciculata zona reticularis
81
zona glomerulosa
small columnar/pyramidal cells organized into tightly packed ovoid clusters surrounded by capillaries hormones secrete mineralocorticoids
82
mineralocorticoids
regulate Na and K homeostasis principle secretion is aldosterone (increases Na resorp, stimulates K excretion) regulated by renin-angiotensin aldosterone system
83
zona fasciculata
long cords 1-2 cell layers thick, large columnar or pyramidal cells separated by sinusoidal capillaries abundant cytoplasmic lipid droplets that give cells a vacuolated appearance
84
zona fasciculata hormones
secrete glucocorticoids in response to ACTH from pituitary which regulates gluconeogenesis and glycogenesis principle secretion is cortisol
85
zona fasciculata function
control carbohydrate, fat, and protein metabolism
86
zona reticularis
smaller cells with deeply stained nuclei, arranged in network of irregular cords surrounded by wide capillaries cells often dark, contain few lipid droplets in cytoplasm
87
zona reticularis hormones
secrete weak androgens (DHEA, DHEAS, and androstenedione) secrete some glucocorticoids, responsive to ACTH
88
zona reticularis function
weak, masculinizing hormones
89
adrenal medulla
derived from neural crest functions as a modified sympathetic ganglion
90
chromaffin cells
epitheliod (columnar) secretory cells that produce catecholamines, surrounded by capillaries secrete epinephrine mostly, some norepinephrine modified postgang symp neurons innervated by myelinated, pregang symp nerve terminals
91
ganglion cells
large round cells with prominent nuclei, found in clusters axons extend to adrenal cortex and impact secretory activity, blood vessels and splanchnic nerves
92
how are the effects of epinephrine mediated
by adrenergic receptors, multiple alpha and beta adrenergic receptors expressed in different target tissues
93
what do the suprarenal arteries give rise to
short cortical and long medullary arteries
94
short cortical arteries
form fenestrated arterial capillary plexus in subcapsular space and zona glomerulus converge into cortical sinusoidal capillaries that traverse zona fasciculata, drain into fenestrated venous capillary plexus in zona reticularis and medulla
95
long medullary arteries
traverse cortex and form sinusoidal capillaries in medulla to provide arterial blood
96
what drains into central adrenomedullary veins? why are they unusual?
cortical and medullary capillary plexuses tunica media contains abundant SM cells, contraction enhances efflux of hormones into circulation
97
secretory cells and vasculature

histology (15 decks)

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