Endocrine - Part 2 Flashcards
describe covering of pineal gland
- pia matter
- no blood brain barrier
what divides the pineal gland into lobules?
CT septa (trabeculae) that extend from the capsule
what type of cells make up the pineal gland?
- pinealocytes
- glial cells (interstitial cells)
what is the major product of pinealocytes and what is it’s function?
melatonin - for regulation of sleep cycle
describe pinealocytes
- slightly basophilic
- irregular lobulated nuclei
- distinct nucleoli
- silver stain: long tortuous branches
what is corpora arenacea?
brain sand - seen in PINEAL gland
- calcium phosphate or calcium carbonate granules
- irregular shaped, often lammelar dark spots
innervation of pineal gland
post ganglionic sympathetic nervs that arise in the superior cervical ganglion
what environmental factor affects pineal gland function?
external lighting - signals from retinal neurons relayed to pineal gland inhibit secretion of melatonin
what can pineal gland tumors cause?
may restrict CSF flow through aqueduct of Sylvius -> cause hydrocephalus
derivation of the thyroid gland
from the cephalic portion of the alimentary canal endoderm
thyroid gland: description, cells, blood/lymph
- 2 lobes connected by isthmus
- lobes made of follicles filled with colloid
- principal cells
- parafollicular/C cells
- extensive blood/lymph capillary network surrounding follicles
describe lining of follicles
simple cuboidal epithelium:
- inactive portions: almost squamous
- active portions: more columnar
what do principal cells secrete?
T3 and T4
what type of vesicles may principal cells have?
colloidal reabsorption droplets
describe colloid
- acidophilic
- glycoprotein thyroglobulin
- inactive storage form of thyroid hormones
what kind of endothelium do the capillaries in the thyroid gland have?
fenestrated
function of parafollicular/C cells
secrete calcitonin
describe C cells
- somewhat larger than follicular cells
- have numerous 100-180 nm granules
- stain poorly in humans (white or clear)
function of calcitonin
- suppresses bone resorption by inhibiting osteoclast activity
- humans: minor role in regulating blood [calcium]
what stimulates calcitonin secretion?
elevated blood calcium levels
what suppresses calcitonin secretion?
when [calcium] falls below normal
what is more important than calcitonin for regulating blood [calcium]?
PTH
describe where thyroglobulin (THY) production, modification, and secretion
synthesized in rER
glycosylated in rER and golgi
vesicles release contents in lumen of follicle
describe the transport/processing of iodide in the thyroid gland
- actively transported into cytosol across basal plasma membrane
- oxidized in cytoplasm
- enters colloid, where it iodinates Tyr residues on thyroglobulin
TSH: where does it come from, what does it bind, then what happens
- released from anterior pituitary
- binds TSH receptors on follicular cells
- cells then endocytose colloid which combines with lysosomes
how are iodinated residues released from thyroid gland?
cleaved from THY, T3, T4 -> released into cytosol, then at plasma membrane
what are the functions of thyroid hormones? (5)
- stimulate transcription of many genes
- cause general increase in cellular metabolism
- stimulate carb metabolism
- decrease synthesis of cholesterol, phospholipids, TGs
- increase synthesis of FA’s
what can excessive production of thyroid hormones lead to?
- weight loss
- increased heart rate, respiration, appetite
- muscle tremors
- tiredness
- frequent or excessive menstrual bleeding
what does iodine deficiency cause?
decreased T3, T4 -> production -> increased TSH -> leads to follicular hyperplasia (goiter)
what does T3 stand for?
triiodothyronine
what does T4 stand for?
thyroxine
what is hyperthyroidism?
graves disease:
-thyroid hyperfunction due to immunologic dysfunction that produces a circulating Ig that has effects similar to TSH
what is Hashimoto’s disease?
autoimmune destruction of thyroid resulting in hypothyroidism
- thyroid peroxidase Abs formed
- thyroid infiltrated with lymphocytes and plasma cells that may organize into germinal centers
which gender gets thyroid cancer more often?
females 3-4x more
what is myxedema? when can you get this?
localized skin disorder - swelling
-present in hypothyroidism
describe the parathyroid glands
- 4 small glands behind thyroid gland
- each w/i a CT capsule w/ septa
what are the two main cell types in parathyroid glands?
- chief/principal cells
- oxyphil cells
describe chief/principal cells of parathyroid
have irregular granules that contain parathyroid hormone (PTH)
function of PTH
- increases calcium in blood by stimulating the number and activity of osteoclasts (calcified bone matrix resorbed and calcium released)
- increased resorption of calcium and excretion of phosphate from kidney distal convoluted tubules
- increased intestinal absorption of calcium by stimulating vitamin D synthesis, which then stimulates synthesis of Ca binding protein in intestine
describe oxyphil cells of parathyroid
- larger than chief cells
- stain intensely w/ eosin (lots of mitochondria)
- appear after puberty
function of oxyphil cells of parathyroid
unclear - potentially transitional chief cells
what are the causes/distribution of causes for hyperparathyroidism?
- adenoma (80%)
- carcinoma (1-2%)
- hyperplasia (15%)
what happens in hyperparathyroidism?
- blood Ca high, PO4 low
- may get bone cysts (osteitis fibrosa cystica)
symptoms of osteitis fibrosa cystica
- rubbery deformed bones
- kidney stones
- pancreatitis
- peptic ulcers
- HTN
what happens in hypoparathyroidism?
blood Ca low, PO4 high
- tetany
- muscle cramps
- exaggerated tendon reflexes
- jaw locks
describe layers of adrenal gland
2 concentric layers:
- cortex
- medulla
derivations of cortex and medulla of adrenal gland
cortex: from mesoderm
medulla: from neural crest
what does the adrenal gland medulla consist of?
cells arranged in cords or clumps supported by a reticular fiber network
-may also see sympathetic ganglionic nerve cells
describe chromaffin cells
- adrenal medullary parenchymal cells
- have numerous secretory granules containing epinephrine or norepinephrine
how can you differentiate b/w epinephrine or norepinephrine secreting chromaffin cells?
cells secreting epinephrine have smaller granules
what are the adrenal gland cortex zones
- zona glomerulosa
- zona fasciculata
- zona reticularis
secretions of zona glomerulosa cells
secrete mineralocorticoids (aldosterone)
what stimulates the synthesis of aldosterone?
angiotensin II and ACTH
secretions of zona fasciculata cells
secrete glucocorticoids (corticol, corticosterone)
describe capillaries of zona fasciculata
sinusoidal capillaries arranged longitudinally b/w columns of parenchymal cells in adrenal gland
secretions of zona reticularis cells
secrete gonadocorticoids (DHEA, androstenedione)
pheochromocytomas
- adrenal medulla tumor
- causes hyperglycemia and transient elevations in blood pressure
what is the most common adrenal tumor in adults?
pheochromocytomas
neuroblastomas
- common tumor in children
- does not affect blood pressure
Cushing’s syndrome
excess secretion of cortisol:
- moon face
- high blood sugar
- diabetes mellitus
- amenorrhea (no period)
- hirsutism (hair everywhere)
- acne
- emotionally labile
Conn’s syndrome
excess production of aldosterone
- excess water retention
- HTN
- hypokalemia
Addison’s disease
adrenocortical insufficiency
- weakness
- nausea
- weight loss
- elevated ACTH levels (causes hyperpigmentation)
Waterhouse-Friderichsen syndrome
acute cortical destruction
- meningococcal sepsis
- endotoxic shock
