Endocrine Histology Flashcards
what are the 2 embryological origins of the pituitary gland (hypophysis)?
adenohypophysis: derived from oral ectoderm, becomes anterior (pars distalis), intermediate (pars intermedia), and tuberal pituitary regions
neurohypophysis (pars nervosa): derived from neural ectoderm, becomes posterior pituitary
fill in the blanks regarding the neurovascular link between the hypothalamus and pituitary gland:
_______ of blood vessels at the base of the hypothalamus (called the ________) allow secretory products to reach portal veins
blood then reaches the ________ in the anterior pituitary, which bathes the cells of the _______
primary plexus of blood vessels at the base of the hypothalamus (called the median eminence) allow secretory products to reach portal veins
blood then reaches the secondary plexus in the anterior pituitary, which bathes the cells of the adenohypophysis
which (multiple) of the following adenohypophysial cells are basophilic (bind basophilic dyes)?
a. FSH
b. LH
c. TSH
d. MSH
e. ACTH
f. GH
g. PRL
glycoprotein hormones containing sialic acid are basophilic, including:
FSH, LH, and POMC-derived peptides (MSH, ACTH)
acidophilic: GH, PRL
what are the hormones of the anterior (pars distalis) and intermediate (pars intermedia) lobes of the pituitary gland?
FLAT PEG + M:
FSH
LH
ACTH (from POMC)
TSH
PRL
endorphins
GH
MSH (from POMC)
what are the 3 major cell types of the posterior pituitary (neurohypophysis)?
- axonal process of unmyelinated nerves: cell bodies located in paraventricular nuclei (oxytocin) and supraoptic nuclei (vasopressin/ADH) of hypothalamus
- pituicytes: glial-like support cells
- endothelial cells: comprise fenestrated blood vessels
from where do the axonal processes within the posterior pituitary (neurohypophysis) come from? how do they reach the posterior pituitary?
cell bodies of axons located in either paraventricular (oxytocin cells) or supraoptic (vasopressin cells) nuclei of hypothalamus
axonal fibers converge at median eminence to form hypothalamo-hypophyseal tract that enters posterior lobe of pituitary
which 2 hormones are secreted from the posterior pituitary and from where are the cell bodies that produces these hormones?
- paraventricular cells of hypothalamus produce oxytocin
- supraoptic cells of hypothalamus produce vasopressin/ADH
the storage granules found in the terminal portions of the axonal processes within the posterior pituitary are referred to as…
Herring bodies - can be visualized with a specific stain, contain hormones
as precursor molecules, oxytocin (paraventricular nuclei) and vasopressin (supraoptic nuclei) are bound to _____
neurophysins I and II
hormones are cleaved free as they near the end of the axon, before release from Herring body granules
what are the embryological origins of the thyroid gland?
thyroid gland derived from endoderm, begins as evagination from the floor of the mouth
also contains tubules derived from the fifth pharyngeal pouch - contain neural crest derived parafollicular/clear/C cells
what is the function of the parafollicular or clear cells of the thyroid gland?
secrete calcitonin - “tones” down Ca2+ levels in the blood, opposes action of PTH
describe the micro-anatomy of the thyroid gland
simple cuboidal epithelium surrounding ETC accumulation of colloid which is secreted by follicular cells and contains thryoglobulin (TG), the precursor to thyroid hormone
______ is a glycoprotein composed of 2 subunits, which constitutes the major component of ______ that fills the thyroid follicles
THYROGLOBULIN is a glycoprotein composed of 2 subunits, which constitutes the major component of COLLOID that fills the thyroid follicles
which form of thyroid hormone is most biologically active?
T3 (thyroxine) is most biologically active - binds TH receptor with high affinity
T4 (triiodothyronine) is secreted in greater amounts by the thyroid follicular cells, but it is usually metabolized to T3 in peripheral tissues
T3 and T4 secretion are controlled by negative feedback, such that they inhibit secretion of ____ from the hypothalamus and ____ from the anterior pituitary
T3 and T4 secretion are controlled by negative feedback, such that they inhibit secretion of TRH from the hypothalamus and TSH from the anterior pituitary
what is the effect of congenital hypothyroid (previously termed cretins)?
low/absent thyroid hormone or iodination of thyroid hormone —> short stature, cognitive deficits
this is because thyroid hormone is necessary for proper growth
how does a congenital deficiency in thyroid hormone vs growth hormone present?
lack of TH (or iodination) —> short stature, cognitive defects
lack of GH —> dwarfism (defective long bone growth)
how does low dietary intake of iodine cause goiter?
goiter: thyroid gland hypertrophy
lack of iodine induces TSH stimulation of thyroid follicle proliferation —> increase in gland size
Graves’ disease
hyperthyroid condition in which antibodies constitutively activate the thyroid receptor
accompanied by thryotoxicosis and exopthalmia (bulging eyes)
Hashimoto’s disease
autoimmune disease against thryoglobulin (thyroid hormone precursor) or other thyroid components —> resulting hypothyroidism
which 2 cell types are found in the parathyroid glands?
- principal/ chief cells: most abundant, pale-staining, produce/secrete PTH (stored in granules)
- oxyphilic cells: stain intensely acidophilic, lack granules, function unknown
which cells make up the adrenal medulla, from what embryonic tissue are they derived, and what hormones do they secrete?
chromaffin cells (derived from neural crest cells), secrete epinephrine and norepinephrine
cells secreting NE are very granular, cells secreting Epi are more homogenous and stain less densely
explain how the adrenal medulla has a dual blood supply
- superior, middle, and inferior suprarenal arteries form a plexus that distributes blood to the outermost zona glomerulosa via fenestrated capillaries, and blood travels inward to medulla via sinusoids
- medullary arterioles (direct supply)
a single central vein drains the entire adrenal gland, draining into the ______ vein on the left and the _____ on the right
a single central vein drains the entire adrenal gland, draining into the RENAL vein on the left and the VENA CAVA on the right
contrast the functions of the zona glomerulosa, zona fasciculata, and zona reticularis
zona glomerulosa: secretes mineralocorticoids (primarily aldosterone)
zona fasciculata: secretes glucocorticoids (primarily cortisol)
zona reticularis: secretes gonadocorticoids or sex steroid (androgens)
in the adrenal cortex,
_____ secretes aldosterone
_____ secretes cortisol
_____ secretes androgens
zona glomerulosa: secretes mineralocorticoids (primarily aldosterone)
zona fasciculata: secretes glucocorticoids (primarily cortisol)
zona reticularis: secretes gonadocorticoids or sex steroid (androgens)
contrast the histological appearance of the zona glomerulosa, fasciculata, and reticulata
zona glomerulosa - round cells in clusters separated by connective tissue and lipid droplets, dark staining/ acidophilic nuclei
zona fasciculata - arranged in cords one layer thick, separated by connective tissue and capillaries, vacuolated cytoplasms due to high lipid content (“spongiocytes”)
zona reticulata - small cells in irregular network, surrounded by blood vessels and connective tissue
