HSF 3 - Unit 2 Histology: Endocrine Glands Flashcards
how does the endocrine system communicate with other parts of the body?
via chemical messengers (hormones) that are secretory products of endocrine cells, which are carried via the bloodstream to the target tissue that contains receptors
what are endocrine organs composed of? type of cell, cell characteristics, and their origin?
secretory cells from epithelial origin, prominent nuclei and numerous organelles; lack ducts so secrete hormones into surrounding interstitial space
what is special about the blood supply of endocrine organs?
rich supply with fenestrated capillary network: good for absorbing and secreting hormones
what important function does the hypothalamus have?
coordinates endocrine functions of the body by being an intermediary between the ANS and endocrine system
what do most endocrine glands form and where are these found?
discreet organs, found in pancreas where the endocrine and exocrine tissue is intermixed
what is another name for the pituitary gland?
hypohpysis
where is the pituitary gland found and how big is it?
1 cm, lies beneath the 3rd ventricle of the brain within the sella turcica of the sphenoid bone
what controls secretions of the pituitary?
the hypothalamus
what is the blood supply of the pituitary? what does this allow?
complex: contains hypophyseal portal system, allows communication between hypothalamus and pituitary
what are the different kinds of hormones secreted by the pituitary gland?
trophic and direct acting
what are trophic hormones? which ones are they?
the target organ of the hormone is another endocrine gland, TSH, ACTH, FSH, LH
what are direct-acting hormones? which ones are they?
the target organ is non-endocrine; GH, ADH, MSH, oxytocin, prolactin
what are the glands that are pituitary-dependent?
thyroid, adrenal cortex, and gonads
how is the pituitary divided?
into posterior and anterior portions functionally, anatomically, and embryologically
what kind of tissue is found in each division of the pituitary?
anterior: glandular epithelial tissue
posterior: neural secretory tissue
what is the anterior pituitary known as?
master gland = adenohypophysis = pars distalis = pars anterior
what is the embryological origin of the tissue of the anterior pituitary?
arises from evagination of the ectoderm from the oral cavity in the pharynx in the Rathke’s pouch region
what are the divisions of the developed Rathke’s pouch?
pars distalis (bulk; secretes most hormones, some of each kind) pars intermedia (between anterior and posterior pituitary) pars tuberalis (stalk/infundibulum)
what does the pars intermedia do? what special feature can be found here?
secretes MSH and ACTH; cystic remnants of Rathke’s pouch
what hormones are secreted by the pars distalis?
GH and prolactin (direct-acting)
TSH, ACTH, FSH, LH (trophic)
how does the hypothalamus influence pituitary secretions?
controls via hypothalamic regulating factors (hormones); releasing and inhibitory factors
what are the different types of cells within the anterior pituitary?
2 kinds of secretory cells: chromophils (stain) and chromophobes (don’t stain)
how do chromophils stain?
acidophils (acidic dye and turn pink in H&E) and basophils (basic dye and turn pale blue-purple in H&E)
how do chromophobes stain? what do they represent?
don’t take up dye, clear on H&E and represent inactive cells
what are the different kinds of acidophils?
somatotrophs and mammotrophs
somatotrophs
make up 50% of cells, secrete GH
mammotrophs
= lactotrophs, make up 20% of cells, secrete prolactin
what are the different kinds of basophils?
thyrotrophs, gonadotrophs, corticotrophs
thyrotrophs
5% of cells, secrete TSH (Thyrotropin)
gonadotrophs
5% of cells, secrete FSH and LH
corticotrophs
20% of cells, secrete ACTH, MSH, and endorphins
what is another name for the posterior pituitary? where is it located?
neurohypophysis, pars nervosa; located ventral to the hypothalamus, connects with infundibulum which contains axons of neurosecretory origin that communicate with hypothalamus
what kind of tissue makes up the posterior pituitary?
nervous tissue from the floor of diencephalon (3rd ventricle), consists of pituicytes (support cells) and neurosecretory nerve axons
what do the axons of the posterior pituitary do?
store and release products from nerve cell bodies in the hypothalamus (neurosecretion)
what is neurosecretion regulated by?
hypothalamic hypophyseal feedback loop
what hormones are secreted by the posterior pituitary?
secreted by hypothalamus via posterior: oxytocin and ADH (vasopressin)
how are hormones stored in the posterior pituitary?
stored in neurosecretory granules in dilations of axons = Herring bodies
ADH
controls blood pressure by altering permeability of renal collecting tubes
what happens when you decrease ADH?
increase urine production as in diabetes indipidus
where is ADH synthesized?
by neuron cell bodies in supraoptic nucleus of hypothalamus
oxytocin
promotes smooth muscle contraction in uterus and breasts, especially during labor and lactation
where is oxytocin synthesized?
by neuron cell bodies in paraventricular nucleus of hypothalamus
what is the shape, location, and embryological origin of the thyroid gland?
bilateral, lobulated endocrine gland on ventral neck, with right and left lobes connected by a narrow isthmus, embryologically derived from epithelial downgrowth of fetal tongue
what is the thyroid surrounded by?
loose CT capsule with a fine CT septa
what is unique about the thyroid gland?
storage of large amounts of inactive hormone called thyroglobulin
what are the characteristics of thyroglobulin? where is it stored?
eosinophilic glycoprotein; stored in extracellular follicles
what are extracellular follicles?
structural units of gland, lined by simple cuboidal
what is the extracellular follicles’ role in thyroid secretion of hormones?
concentrates iodine 30-40x blood levels and secrete it as thyroglobulin via the apical microvilli
what does iodination do to hormones?
activates
what are the active hormones of the thyroid?
T3 and T4
T3
triiodothronine, more biologically active and potent form
T4
tetraiodothyronine, gets deiodinated in the liver to make T3
what do thyroid hormones do?
regulate BMR and growth and development of nervous system
what happens if there is a thyroid deficiency during fetal development?
impairs neural development and myelination so causes physical stunting and mental retardation (cretinism)
what are Ccells?
secondary secretory cells in the thyroid gland, also called parafollicular cells or clear cells
where are Ccells and what do they do?
located at the periphery of follicles or scattered within CT, in lower vertebrates makes up a separate organ; secrete calcitonin
what does calcitonin do and what is its secretion regulated by?
regulates blood Ca levels along with parathyroid hormone, decreased levels inhibit osteoclasts; synthesis, storage, and release of thyroid hormones under control of TSH from the anterior pituitary
what are the different thyroid pathologies?
goiter, which can be caused by hyper and hypothyroidism
hypothyroidism
autoimmune reaction, decreased size of the gland; can cause goiter by insufficient dietary intake of iodine, leading to decreased thyroid hormone production and possible hypertrophy with non-functional thyroglobulin
hyperthyroidism
increase in size and number of follicle cells
what is the parathyroid gland? where is it? what is its embryological origin?
small, oval endocrine glands that are associated with the thyroid on the posterior surface, 2 pairs (superior and inferior); 3rd and 4th branchial (pharyngeal) pouches
what does the parathyroid gland do? what does this secretion stimulate?
secretes PTH, which regulates serum Ca and P, which are antagonists to calcitonin; works slower than calcitonin
how does PTH change serum calcium?
increases by…
1) increasing osteoclast activity by inhibiting osteoblast activity
2) increasing renal tubular absorption of cain kidneys (and inhibiting absorption of P)
3) Ca absorption from gut via vitamin D
what is PTH secretion stimulated by?
low blood calcium
what can change the integrity of the parathyroid gland?
damage or removal causes hypoparathyroidism; hyperparathyroidism can cause excess PTH production
what are the secretory cells of the parathyroid gland?
Chief cells and oxyphil cells
chief cells
most abundant cells in parathyroid, secrete PTH, stain clear to light pink, with dark nuclei and moderate amount of cytoplasm
oxyphil cells
larger and less numerous cells in the parathyroid, stain dark pink, more cytoplasm, occur in clusters, contain large numbers of mitochondria but have no secretory function; function is unknown
what can happen to the parathyroid gland with age?
fatty infiltration
where is the adrenal gland? what tissue surrounds it?
superior to kidneys, covered by a thin CT capsule
what is the embryological origin of the adrenal cortex?
mesodermal
what is the regulation of the adrenal cortex?
ACTH secreted by the anterior pituitary
what are the functional classes of the adrenal gland hormones?
mineralocorticoids, glucocorticoids, sex hormones
mineralocorticoids and an example
control electrolyte and fluid balance by regulating Na and K levels via Na pumps, especially in renal tubules, regulates BP via JGA; aldosterone
glucocorticoids and an example
stimulate gluconeogenesis and glycogenolysis, which both increase blood glucose; also increases metabolism and breakdown of proteins, carbs, and lipids; cortisol
sex hormones and an example
very small amount of adrenal hormones, supplement gonadal production; androgens
what are the layers of the adrenal cortex superficial to deep?
zona glomerulosa, zona fasciculata, zona reticularis
zona glomerulosa
about 15% of cortex, thin, dark-staining band that secretes mineralocorticoids
zona fasciculata
about 80% of cortex, broad, light-staining band that contains spongiocytes, secretes glucocorticoids, which increases under stress and decreases immune response, small amounts of androgens secreted here as well
zona reticularis
about 5% of cortex, think, dark-staining band that secretes small quantities of androgens and glucocorticoids
what is Addison’s disease?
hypoadrenocorticism; failure of the adrenal cortex to produce hormones (mineralo/glucocorticoids) usually due to atrophy because of an autoimmune disease; results in decreased aldosterone leading to a decreased extracellular fluid and hyponatremia and hyperkalemia, causing mild acidosis which can lead to shock and death (addisonian crisis); a decreased cortisol level decreases blood glucose levels and tx of this condition is to administer mineralocorticoids and glucocorticoids
what is Cushing’s disease? what are the types and their different sx?
hyperadrenocorticism; primary and secondary;
1’: adrenal; due to general adrenal hyperplasia or functional tumor of adrenal cortex that results in excess cortisol secretion
2’: pituitary; due to increased ACTH from the anterior pituitary due to a tumor; increased ACTH leads to adrenal hyperplasia and increased cortisol; can also result from cortisol secreting tumor
what is the embryological origin of adrenal medulla?
neuroectoderm
what cells are in the adrenal medulla?
chromaffin cells: modified, post-ganglionic neuronal cells with secretory function that are epitheloid in apperance; and are controlled by preganglionic nerve fibers; secrete catecholamines (epi and norepi)
where are catecholamines stored within the adrenal medulla?
cytoplasmic granules called dense core granules
what effect does the release of catecholamines have?
systemic effect on adrenergic receptors especially on all types of muscle
what does adrenaline promote?
glycogenolysis in liver as energy source and is responsible for the production of enkephalins
what are enkephalins?
endogenous opioids responsible for pain relief
what is pheochromocytoma?
a generally benign functional tumor of chromaffin cells, so sx usually due to increased epi and norepi secretion: hypertension, headache, cardiac arrythmias, chest pain, anxiety, panic attacks, nausea; tx is surgical removal of the tumor
what are the types of cells in the pancreas? what makes up the majority?
exocrine and endocrine; acini: exocrine cells that secrete digestive products into the gut
how do islets of langerhans form?
during development, endocrine cells migrate from the duct system and aggregate around capillaries of the pancreas; found distributed throughout the exocrine pancreatic tissue
what types of cells are found within islets of langerhans? what are their relative concentrations?
alpha (15-20%), beta (70%), delta (5-10%)
alpha cells of pancreas
secrete glucagon, which increases blood glucose by stimulating glucogenesis and glycogenolysis
beta cells of pancreas
secrete insulin, which decreases blood glucose and stimulates intracellular glycogenesis
delta cells of pancreas
secrete somatostatin, which inhibits both insulin and glucagon production
what other kinds of endocrine cells are found in the pancreas and what do they secrete?
miscellaneous cells secrete VIP and PP (pancreatic polypeptide)
what is pathology of the pancreas?
insulin deficiency or abnormality - Diabetes Mellitus: type I is juvenile onset and due to decreased insulin production
type II is adult onset and due to decrease in insulin receptors or decreased responsiveness
how big is the pineal gland and where is it located?
6-8 mm long and is anterodorsal to the cerebellum
what does the pineal gland develop from?
neuroectoderm as evagination of posterior portion of the 3rd ventricle, from roof of diencephalon
what is the pineal gland’s job?
communicates with the hypothalamus and acts as a photoreceptor in lower vertebrates; translates light intensity and duration (photoperiod) into endocrine activity which is important in circadian rhythms and seasonal reproductive cycles
what does the pineal gland secrete? what does this do?
melatonin; stimulates melanophores, chromatophores (pigment-containing cells), which change in color intensity with reproductive cycle, also has anti-gonadal effect which decreases sex activity; also serotonin which is a vasoconstrictor and neurotransmitter
what does melatonin do?
decreases GNRH from the hypothalamus which decreases sex hormone from gonads
what are the cell types in the pineal gland?
pinealocytes and neuroglial cells
pinealocytes
pineal chief cells; most common, highly modified neurons that secrete melatonin and serotonin
neuroglial cells
interstitial cells; support cells similar to astrocytes
what can be seen in the pineal gland besides the 2 cell types?
corpora arenacea; brain sand which is calcified accretions of Ca and Mg phosphate in aging individuals
what is the embryological origin of endocrine cells in the respiratory and GI systems?
most come from neural crest as highly modified neurons, others from endoderm
what are endocrine cells in the respiratory and GI systems called? what do they secrete?
APUD; secrete peptide and amine hormones
