Lecture 18- Endocrine System Flashcards
What do all endocrine glands have in common (or what defines an endocrine gland?
They secrete hormones into the blood
What is paracrine secretion?
Hormone to a target cell
What is autocrine secretion?
Hormone to self
What makes up the posterior pituitary gland?
- infundibulum or pituitary stalk
- pars nervosa
- tissue develops from brain
What makes up the anterior pituitary gland?
- pars tuberalis
- pars intermedia
- pars distalis
- tissue derived from ectoderm
What are sinusoids?
Essentially giant capillaries
What are degranulated cells?
Cells that turn back into an acidophil or basophil
What are progenitor cells?
Cells that go on to produce other cell types
What are chromophobes?
Either degranulated cells or progenitor cells
What are the acidophils?
- somatotropes (growth hormone)
- mammotropes (prolactin)
What are the basophils?
- gonadotropes (FSH and LH)
- thyrotropes (TSH)
- corticotropes (POMC) cleaves to (ACTH)
What is the best way to differentiate these cells?
- immunohistochemistry
The blood supply to the median eminence, infundibulum, and anterior pituitary is a portal system? What does that mean
Two capillary beds
What does the pars tuberalis secrete?
mainly basophilic gonadotropes
What does the pars intermedia secrete?
basophilic cortico tropes. POMC cleaved to melanocyte stimulating hormone. In pars distalis POMC cleaved to ACTH
What does oxytocin do?
- milk let down
- uterine contraction during labor
What are pituicytes?
Glial cells that surround the unmyelinated axons
What are herring bodies?
Cells that store the hormone
Where are the neuronal cell bodies for the posterior pituitary?
hypothalamus
Where are the alpha cells located in the islets of langerhans?
Along the periphery- glucagon- raises blood glucose
Where are the beta cells located in the islets of langerhans?
On the interior- insulin that lowers blood glucose
Where is the adrenal gland found?
On top of the kidney, suprarenal gland
What are the three layers of the adrenal gland?
- capsule
- cortex derived from mesoderm
- medulla derived from neural crest
What are the three layers of the cortex?
- zona glomerulosa
- zona fasciculata
- zona reticularis
They precursor to hormones produced in the adrenal cortex is cholesterol. What does this tell you?
Lipid soluble, hydrophobic
What is secreted in the zona glomerulosa?
aldosterone
What are mineralocorticoid and give an example.
aldosterone, influence salt and water balance
What does aldosterone do?
Released from the adrenal gland under low BP to stimulate Na+ retention and for the kidney to release renin and angiotensin II
What effect does aldosterone have on blood K+ levels?
increases secretion of K+ in the collecting duct to lower blood K+
What does the zona fasciuluta release?
glucocorticoids (eg cortisol), washed out lipid droplets that contained steroids
What signals the release of cortisol?
ACTH
What effect does cortisol have on the hypothalamus?
negative feedback
What effects does cortisol have on the body?
- immunosuppressive
- anti- inflammatory
What is released in the zona reticularis?
androgens- lipid soluble steroids, wide capillaries or sinusoids
What induces the release of androgens from the adrenal gland?
ACTH
Where are chromaffin cells?
adrenal medulla, derived from the neural crest
What effect does the sympathetic pre-ganglionic neuron have on the adrenal medulla?
release epinephrine
If the sympathetic pre-ganglionic synapses on a post ganglionic neuron, what will be secreted?
norepinephrine
What are the main parts of the thyroid?
- capsule
- septa
- thyroid follicles
What are the follicular cells?
Simple epithelium, cuboidal or columnar
What is the colloid filled lumen?
thyroglobulin
What is stored in the C cells?
Calcitonin
If the follicular cells are inactive (No TSH) they are more?
squamous
If the follicular cells are active, they are…
more cuboidal or columnar, thyroid hormone
What are three effects of thyroid hormone?
- increase basal metabolic rate
- increase lipid metabolism
- increase in carbohydrate metabolism
Which cell has secretory granules?
C cells
What effect does the caclitonin from the secretory granules have on the body?
inhibit osteoclasts
What does thyroglobulin help store?
Iodine in T3 and T4
What stimulates the production and release of thyroid hormone from the thyroid gland?
TSH from anterior pituitary
What shuts off TSH release from the pituitary?
Thyroid Stimulating Hormone
What shuts off TSH release from the pituitary?
Thyroid Hormone, negative feedback
What would the cells look like if a test revealed elevated serum TSH levels?
Follicular cell hyperplasia but with little colloid
What cells are found in the parathyroid gland?
- chief cells
- oxyphil cells
What do chief cells secrete?
Parathyroid hormone, purple nuclei with pale but acidophilic cytoplasm
Low blood calcium levels stimulate parathyroid hormone secretion. How does PTH raise blood Ca++ levels?
Increases Ca++ reabsorption in the kidney tubule
What does PTH do in the kidney?
increases the synthesis of 1-ahydroxylage in the PCT of the kidney. Activates Vitamin D to enable Ca++ absorption from the gut
What does the pineal gland secrete?
melatonin
What does melatonin do?
regulates circadian rhythm, darkness promotes the release of melatonin
What is a corpora arenacea?
brain sand, Ca, Mg salts.
What are the other cells found in the pineal gland?
- pinealocytes
- astrocytes
- corpora arenacea
- septa
Some groups recommend stopping fluoride treatment because they could possibly contribute to the calcification of what structure?
pineal gland
