Endocrine System Flashcards
What other organs have endocrine functions?
Adipose tissue
Pancreas
DNES in GI
What are the 5 glands in the endocrine system?
- Pituitary
- Thyroid
- Parathyroid
- Adrenal
- Pineal
What coordinates the majority of endocrine processes?
Hypothalamus
What do endocrine, paracrine, and autocrine cells act on?
Endocrine - cells at a distance
Paracrine - neighboring cells
Autocrine - self
What are the hypothalamus and pituitary gland connected by?
Hypothalamalhypophysial -
- poral system = vasculature
- tract = nervous system
What is the infundibulum?
Part of the posterior pituitary that connects it to the hypothalamus
What is the bulk of the posterior pituitary called?
Pars Nervosa
What is the medium eminence?
Part of the hypothalamus, connects with the infundibulum
What is the bulk of the anterior pituitary called?
Pars Distales
What is the anterior and posterior pituitary separated by?
Interglandular cleft
What type of tissue is the anterior pituitary derived from?
Ectodermal Tissue
What type of tissue is the posterior pituitary made of?
Neural secretory tissue
What part of the anterior pituitary is in direct contact with the posterior pituitary?
pars Intermedia
What type of tissue is the anterior pituitary made of?
Grandular tissue
What are Rathke’s Pouches?
Leftover patches of where the ectodermal tissue was in the anterior pituitary before it was developed
Both lobes of the pituitary gland are housed in what bone?
Sphenoid bone
What are the two sets of vessels that provide blood to the pituitary gland? Which parts of the pituitary gland do they support?
- Superior hypophyseal arteries; pars tuberalis, median eminence, and infundibulum
- Inferior hypophyseal arteries; pars nervosa
Which arteries have primary and secondary capillary plexuses?
Superior hypophyseal arteries
What arteries do the superior hypophyseal arteries arise from? What about the inferior hypophyseal arteries?
Superior; internal carotid and posterior communicating artery
Inferior; internal carotid arteries
What is the importance of the hypothalamohypophyseal portal system?
Allows for direct communication from the hypothalamus to the anterior pituitary gland
Where is the primary capillary plexus of the superior hypophyseal arteries located?
Located in the region of pars tuberalis, medium eminence, and infundibulum
Talk me through the movement of hormones from the hypothalamus to the anterior pituitary
Hypothalumus > medium emenince > primary capillary plexus > hypophysial portal veins > drain into secondary capillary plexus > pars distales
What are the three pieces of the anterior pituitary gland?
- Pars distales
- Pars intermedia
- Pars tuberalis
What is the pars tuberalis?
The neck region of the anterior pituitary
Wraps around the infundibulum
What are the two pieces of the posterior pituitary gland?
- Pars nervosa
2. Infundibulum
How is the pars distalis arranged?
Arranged in cords with interweaving capillaries
What are the three cell types in the pars distalis based on staining?
- Basophils - basic dye
- Acidophils - acidic dye
- Chromophobes - lack staining
What are chromophobes?
Cells in the pars distalis that have recently released all their cytoplasmic contents
Is the pars distalis abundant in capillaries? What type of capillaries? Why this type?
Abundant in capillaries
Fenestrated capillaries
Allow hormones to pass through
What are the 5 cell types in the pars distalis based on function? What hormone do they produce?
- Somatotropes: GH
- Lactotropes: prolactin
- Corticotropes: ACTH
- Gonadotropes: FSH and LH
- Thyrotropes: TSH
What does Growth Hormone (GH) do?
Stimulates the liver + others > release IGF-I > stimulated bone growth, including the growth of epiphyseal plate cartilage
What does prolactin do?
Promotes mammary gland and milk formation
What does ACTH do?
ACTH > adrenal cortex > release of glucocorticoids and gonadocorticoids > ??
What do FSH and LH do?
Stimulate follicular development, spermatogenesis, important in pregnancy
What does TSH do?
Directly acts on follicle cells in the thyroid > release thyroxin
What hormones from the hypothalamus control GH release?
GHRH: positive
Somatostatin: inhibitor
What hormones from the hypothalamus control prolactin release?
Dopamine: inhibitor
What hormones from the hypothalamus control ACTH release?
Corticotropin-releasing hormone: positive
What hormones from the hypothalamus control FSH and LH release?
Gonadotropin-releasing hormone: positive
What hormones from the hypothalamus control TSH release?
Thyrotropin-releasing hormone: positive
How is the pars intermedia characterized?
By colloid-filled follicles
What cells based on staining does the pars intermedia contain?
Basophils and chromophobes
No acidophils
Where is the pars intermedia located?
Between the pars distiles and pars nervosa
Is the pars tuberalis highly vascularized?
Yes, by the hypothalamohypophyseal system
What hormones does the pars tuberalis secrete? What cells does it house? How do they stain
FSH and LH
Gonadotropins
Basophil
Is the posterior pituitary gland an endocrine gland?
No, it only acts as a storage site for hormones but does not produce them
Talk to me about where the cell bodies, axon, and termination occurs for the hypothalamohypophyseal tract
Cell body: supraoptic nuclei and paraventricular nuclei in the hypothalamus
Axon: through the infundibulum
Terminate: fenestrated capillaries in the pars nervosa
What hormones are produced in the hypothalamus and stored in the pars nervosa? (2)
- Anti-diuretic hormone (ADH)
2. Oxytocin
What two specialized cells (ish) are found in the pars nervosa?
- Herring bodies
2. Pituicytes
What are herring bodies? What is their function? Where are they located?
In the pars nervosa
Expanded terminal region of nerve fiber
Houses neurosecretions = ADH, Oxytocin
What does ADH do?
Hypotonic urine
Causes the retention of urine
What does oxytocin do?
Causes strong uteran contractions that occur during childbirth and orgasm
What are pituicytes? Where are they found? What is their function?
In the pars nervosa
Elongated cells with long processes
Support unmyelinated nerve fibers
What is the function of the pineal gland?
Regulated daily body rhythm - the cyrcadian rhythen
What are the two types of parenchymal cells?
- Pinealocytes (95%)
2. Interstitial (glial) cells (5%)
What is the pineal gland characterized by?
Brain Sand (corpora arenacea)
Where is the pineal gland located?
In the posterior region of the 3rd ventricle at the midline of the brain
What hormone does the pineal gland produce?
Melatonin
What are pinealocytes? Where are they located? What tissue type are they?
Located in the pineal gland
Neural tissue
larger, lighter cells
What are interstitial (glial) cells? Where are they located? What is their function?
In the pineal gland
Non-neural cells that support the neuronal cells
What is brian sand? where is it located? What does it do?
In the pineal gland
function: unknown
marker for the 3rd ventricle of the brain
How does the pineal gland act as a photosensitive organ?
Inhibits production of melatonin during the day
Stimulates production of melatonin during darkness
Excess melatonin can contribute to what disorder?
Seasonal Affective Disorder (SAD)
*and also jet lag
What effect could living in Alaska during the summertime have on an individual?
Constant sunlight > little production of melatonin > poor sleep, but elevated mood and energy
Talk me through how light actually affects the pineal gland
Light > retna > superchyasmatic nuclei in hypothalamus > pineal gland > inhibit production of melanin
What are the physical characteristics of the thyroid gland? Shape? Capsule? Avascular or vascular?
Bilobed - looks like a butterfly
Thin CT capsule with trabeculae
Highly vascular - fenestrated capillareis
What is the functional unit of the thyroid gland?
Thyroid follicle
What tissue type is the thyroid follicle? What is it filled with?
Simple cuboidal/columnar epithelium
Filled with colloid
What are the two major cell types in the thyroid gland?
- Follicular cells
2. Parafollicular cells
What hormones do follicular cells produce? Where are they located (specifically) ?
T3 and T4
Thyroid - next to the colloid space
What hormone do parafollicular cells produce? Where are they located (specifically)?
Calcitonin
Thyroid - never right next to the colloid space
What is in high concentration in the colloid of thyroid follicles?
Thyroglobulin
Talk me through the pathways that is T4 and T3 synthesis
- Na/Iodide symporter in basal membrane > increased concentration of iodide in cell
- Iodide in cell > iodide/cl transporter on apical domain > iodide is oxidized as it moves through the membrane by enzyme thyroid peroxidase in the microvilli > iodine
- Thyroglobulin is produced by the cell > exocytosed into lumen space
- Iodine bind to tyrosine residues on thyroglobulin > mono/di iodinated
- Mono/di combine > di + mono = T3, di + di = T4
- TSH released by thyrotropes in the pituitary gland > stimulates follicular cells > follicular cells to endocytose colloid material = endocytosis of thyroglobulin + T3&T4
- Endosome fuses with lysosome > T3&T4 are liberated > exocytosis of T3&T4 + recycling of thyroglobulin to colloid space
How do thyroid cells change with the synthesis of T3&T4?
Increased synthesis > increase in size
Simple cuboidal > tall columnar
Talk me through the regulation of thyroid hormones
Hypothalamus > TRH > pituitary gland > TSH > follicle cells in thyroid»_space;»> release of T3&T4 into the blood >
- T4 to the liver and kidney to be converted into T3
- Both go back to the hypothalamus for a neg feedback loop
Which is more highly active T3 or T4? Which is more abundant?
T3 is more highly active
T4 is 4x more abundant
What must T3 and T4 cross to reach the hypothalamus? How do they do this?
Must cross the BBB
Use a special transporter
What is hypothyroidism? What is it caused by?
Hypo - no synthesis of thyroid hormone
Caused by insufficient dietary iodine
What is Hashimoto’s thyroiditis? What is it caused by? What can we see histologically?
Autoimmune disease
Antibodies attack thyroglobulin in colloid or attack follicle cells
Destruction of follicles + massive infiltration of lymphocytes + hemorrhaging
What is hyperthyroidism?
Excessive amounts of thyroid hormones
What is Grave’s disease? What is it caused by? What can we see histologically? What can we see on the overall person?
Autoimmune disease
Antibodies bind to follicular cells > increase in the synthesis of thyroid hormones > excess release of TH into the blood
Colloid pulls away, FC become tall and columnar
Increased metabolic rate, weight loss, increased heart rate, building eyes
How is T3&T4 production altered during a pathological state?
T3 and T4 bind to megalin receptor > bypass the fusion with lysosome > release everything bound together = T3 and T4 are inactive
Inactive T3&T4 is a diagnostic marker for thyroid disfunction
What is the parathyroid gland? How is it arranged? Does it have a capsule? How are the cells arranged?
Superior and inferior pars of glands
Thin CT Capsule
Cells arranged in densely packed cords
Where is the parathyroid gland located with respect to the thyroid gland? What are they separated by?
Lie on the posterior surface of the thyroid
Separated by CT capsule
What are the two major cell types in the parathyroid gland?
- Cheif Cells
2. Oxyphil Cells
What is the function of Chief cells? Where are they located?
Synthesize, store, and secrete PTH
Located in the parathyroid gland
What is the function of oxyphil cells? Where are they located?
Minor subset with no secretory function might be defunct chief cells
Located in the parethyroid gland
What does PTH do? What does this mean for your parathyroid gland?
PTH increases blood calcium levels and regulated phosphate levels
You can not live without your parathyroid
What are the three ways PTH increases blood calcium levels
- Indirectly causes osteoclast stimulation = breakdown of bone and release of calcium phosphate
- Kidney distal tubule increase Ca reabsorption so it is not lost in the urine
- Increases formation of active vitamin D in the kidney, which promotes tubular reabsorption of calcium
What would be the expected patient outcome if all parathyroid tissue is removed during a thyroidectomy?
💀💀💀
How do oxyphil cells of the parathyroid stain? Cheif cells?
Oxyphil stain light
Cheif cells stain darker
Where is the adrenal (superanal) gland located?
Superior to the kidney
What are the three regions of the adrenal gland?
- Capsule
- Cortex
- Medulla
What are the three regions of the adrenal cortex?
- Zona glomerulosa
- Zona fasciculata
- Zona reticularis
What are the embryonic origins of the adrenal cortex? The medulla?
Adrenal cortex: mesodermal mesenchyme
Medulla: nerural crest cells
What does the medulla of the adrenal gland secrete? What are examples?
Catecholamines
Epinephrin and Norepinephrine
What does the zona glomerulosa of the adrenal gland secrete? What is its function (2)? What is the zona glomerulosa regulated by?
Secrete mineralocoriticoids - aldosterone
1. Electrolyte and osmotic balance
2. Prevents acidosis
Regulated by angiotensin II
Talk me through how aldosterone enacts its function
RAS > angiotensin II > adrenal cortex > aldosterone > act on DCT > increased sodium reabsorption and potassium secretion > increased blood pressure
What does the zona fasciculata of the adrenal gland secrete? What is its function (3)? What is it regulated by?
Secretes glucocorticoids 1. Normal metabolism 2. Stress resistance 3. Suppress inflammation Regulated by ACTH
Talk me through how glucocorticoids enact their function (only 2 steps)
Glucocorticoids > breakdown of glycogen > increased blood glucose levels
Also converts norepi > epi
What does the zona reticularies of the adrenal gland secrete? What is its function (1)? What is it regulated by?
Secretes gonadocorticoids - weak androgens
1. Masculinizing effect
Regulated by ACTH
What cell type is found in the adrenal medulla? What do these cells arise from?
Chromaffin cells
Neural crest > chromaffin cells
What are chromaffin cells innervated by? What are they equivalent to?
Innervated by sympathetic neurons
Equivalent to postsynaptic nerve cells
What do chromaffin cells secrete (2)? What is this regulated by?
Epinephrine (80%)
Norepinephrine (20%)
Post-ganglionic sympathetic neurons act on chromaffin cells > release epi/norepi
Catecholamines and glucocorticoids prepare the body for what?
Fight or flight response
What is the significance of the adrenal medulla having two sources of blood supply?
- One is a direct supply
- The other enter the cortex fist which allows glucocorticoids from the zonula fasciculate. Glucocorticoids convert norepi > epi
What are the three patterns of adrenal blood supply? What do they supply blood to?
- Capsular capillaries - supplies the capsular region
- Fenestrated cortical sinusoidal capillaries - creates secondary plexus in the medulla
- Medullary arterioles = medullary capillary sinusoids - bypass cortex, supplies the medulla
What do all three patterns of the adrenal blood supply drain into?
The central medullary vein
What tissue type is the central medullary vein of the adrenal gland abundant in? (this causes a sponge effect)
Smooth muscle
When the smooth muscle contracts the adrenal gland squeezes releasing a massive amount of blood and hormones
What is hyperfunctional adrenal gland disorder?
Excess release of ACTH
What is Cushing’s disease? What is it caused by? What are the physical symptoms?
Excessive release of ACTH > release of glucocorticoids
Increased body weight, increased adipose tissue, decreased muscle tone
What is Cushing’s syndrome? What is it caused by? What are the physical symptoms?
Long term use of ACTH (steroids) > excessive release of glucocorticoids
Symptoms are same as Cushing’s disease: Increased body weight, increased adipose tissue, decreased muscle tone
What is hypofunctional adrenal gland disorder?
Levels of ACTH are too low
What is Addison’s disease? What is it caused by? What are the physical symptoms?
Destruction of the zona fasticulara in the adrenal cortex due to direct destruction or a problem with the pituitary gland
Destruction of zona fasticulara > destruction of cells producing glucocorticoids
Darkening of skin, fatigue
Which is more potent epinephrine or norepinephrine?
Epinephrine
