Endocrine System Flashcards
7 parts/organs glands of endocrine system?
- Pituitary= adenohypophysis
- adrenal=hypophysis
- Pineal gland
- Thyroid
- Paraythyroid
- Islet of langerhans
- Diffuse neuroendocrine system
Location of pituitary gland? Other name?
Below the hypothalamus attached by INFUNDIBULUM.
Also functionally attached to hypothalamus.
AKA hypophysis
Pituitary divisions (formal names) and their embryological origin.
Adenohypophysis= Anterior. From Rathke's pouch (ectoderm of stomodeum= oral cavity) /3 parts Neurohypophysis = posterior. From neuroectoderm /2 parts
Adenohypophysis- parts?
Anterior pituitary- 3 parts
- Pars distalis
- pars intermedia
- Pars tuberalis
Neurohypophysis- Parts
- Infundibulum (continuous with hypothalamus)
- Pars nervosa (main body)
- hypothalamohypophyseal tract
Anterior lobe of pituitary **according to Turek notes, not BRS
Pars distalis (from adenohypophysis) + pars tuberalis (from adenohypophysis)
Posterior lobe of pituitary **according to Turek notes, not BRS
Pars intermedia (from adenohypophysis) + pars nervosa (from neurohypophysis)
T/F Glands in the endocrine system have ducts
FALSE- Ductless glands
Regulation of pituitary gland
Peptide hormones from the hypothalamus are released into the capillaries of the infundibulum and travel to the pituitary to stimulate or inhibit release of of hormones from the ANTERIOR PITUITARY
Hormones that regulate pituitary hormones
Thyrotropin Gonadotropin Somatostatin Growth Hormone Corticotropin Inhibitor of prolactin release (dopamine)
Pars distalis- structural components
connective tissue capsule and framework.
Hormones (from hypothalamus) enter pars distalis via secondary capillary plexus exit from the fenestrated capillaries and act on parenchymal cells.
Infundibulum- parts
Median eminence + stem
Blood route through pituitary
2 Main Arteries
(R&L) Superior hypophyseal a. = infundibulum(=median eminence + stem)
(R&L) Inferior hypophyseal a. = pars nervosa
Superior hypophyseal a –> primary capillary plexus (in INFUNDIBULUM) –>hypophyseal portal veins (descend through infundibulum to adenohypophysis, located in pars tuberalis) –> secondary capillary plexus (pars distalis)
Types of cells in pars distalis
Chromophils (acidophils (x2) and basophils(x3)) and chromophobes (3- degranulated, undiffer, CT/Follicular)
Chromophobes- general characteristic–types?
Parenchymal cells in the pars distalis of pituitary. Stain poorly. Few to no granules.
Types:
1. Undifferentiated
2. Degranulated- few granules
3. CT/Follicular- form stromal network to support chromophil cells.
??May contain acidophilic staining chromophiles???
Acidophils-
- staining
- Cell types?
- basic characteristics?
- Do not stain with PAS. Stain with eosin and orange G.
- Somatotrophs and Mammotrophs
- smaller than basophils. Release peptide hormone
Somatotrophs
- Location
- Secretion
- Function
- Regulated by?
- acidophilic cells of pars distalis
- Somatotropin= Growth Hormone
- Increases metabolism in most cells, stimulates production of liver somatomedins (insulin-like growth factors)–> long bone and epiphyseal plate growth
- ——somatostatin (growth hormone inhibiting factor)
++++++Growth hormone releasing factor
What supports chromophils?
Chromophils= pars distalis
CT/Follicular cells are chromophobes that create stromal network to support. Some phagocytic action.
Mammotrophs
- Location
- Secretion
- Function
- Regulated by?
- acidophilic cells of pars distalis (in pit)
- prolactin
- stimulates and maintains lactation
- Lactation increases number.
+++++Thyrotropin-releasing factor (TRF)
—–Prolactin inhibiting factor (dopamine)
Basophilic cells
- staining
- cell types?
- general characteristics?
- PAS positive. Basophilic staining
- (3 types) Corticotrophs, gonadotrophs, thyrotrophs
- Larger than acidophils, fewer granules
Gonadotrophs
- Location
- Secretion
- Function
- Regulated by?
- pars distalis of pituitary
- FSH, LH (also called interstitial cell stimulating hormone)
- FSH- a) stimulates dev of ovarian follicles and stimulates sertoli cells to produce androgen binding protein
LH- stimulates steroidogenesis in ovarian follicles and corpus luteum. Regulator of leydig cells (testosterone pdt) - stimulated by gonadotropin releasing hormone (GnRH)
Corticotrophs
- Location
- Secretion
- Function
- Regulated by?
- pars distalis of pituitary
- ACTH (Adrenocorticotropic hormone) and LPH (lipotropic hormone)
- ACTH- stimulates growth and steroid synthesis in adrenal gland (zona reticularis, fasiculata, and glomerulosa=all of adrenal cortex)
LPH- precursor of b-endorphin - CRH- corticotropin releasing hormone
Thyrotrophs
- Location
- Secretion
- Function
- Regulated by?
- pars distalis of pituitary (only 5% of cells)
- TSH
- TSH= causes thyroid to make T3 and T4
- Thyrotropin releasing hormone
Thyrotropin releasing hormone regulates?
- prolactin release from mammotrophs (acidophilic cell of pars distalis)
- TSH release from thyrotrophs (basophilic cell of pars distalis)
Paracrine regulation of pars distalis (not in notes)
- Cell type?
- Function(s)
- folliculostellate cells between the chromophobes and chromophils. form gap junctions with other folliculostellate cells.
- Regulate hormone production in pars distalis via production of paracrine peptides
Pars Nervosa Contents
- Has the distal ends of axons (NON MYELINATED) from hypothalamus with their herring bodies
- Pituicytes (25% of content in pars nervosa)
- fenestrated capillaries (located near the neuron ends)
Herring bodies–
- What are they? Where are they found?
- Cell bodies of (1) are located…?
- Accumulation of neurosecretory granules in non-myelinated axons in the pars nervosa of pituitary .
- paraventricular and suproptic nuclei of the hypothalamus
Pituicytes
25% of pars nervosa
astrocyte-like glial cells–SUPPORT AXONS IN PARS NERVOSA.
contain glial fibrillary acidic proteins(GFAP- type of intermediate filament, works with vimentin), lipid droplets, and pigments.
Function of pars nervosa?
Hypothalamic axons release oxytocin and ADH near capillary plexus.
Oxytocin
- production and release?
- function
- produced in paraventricular nucleus (some made in supraoptic nucleus) of hypothalamus and released by axons located in the pars nervosa of the pituitary.
- stimulates milk ejection and uterine contractions during childbirth
ADH
- production and release?
- function
- produced mainly in supraoptic nucleus (some in para ventricular nucleus) and released by axons located in pars nervosa of hypothalamus.
- Stimulates water reabsorption by the renal medullary collecting ducts
hypothalamohypophyseal tract
part of the neurophysis
transports ADH and Oxytocin (using neurophysin) and ATP to pars nervosa
Neurophysin
Binding/carrier protein for oxytocin and ADH. Moves them from cell bodies to the axon terminals in the pars nervosa of the pars nervosa (of posterior pituitary)
pars intermedia contents
- basophilic and chromophobic cells,
2. Rathke’s cysts= cuboidal lined epithelial cavities
Pars intermedia function
- basophilic cells (which can extend into pars nervosa) secrete pro-hormone proopiomelanocortin (POMC)
POMC cleaved into melanocyte stimulating hormone = regulator of inflammatory response and fat storage
Function of supraoptic nucleus vs para ventricular nucleus (of hypothalamus)
Supraoptic- mainly ADH production
Paraventricular nucleus- mainly oxytocin production
Pars tuberalis
surrounds hypophyseal stalk
Cords of mainly cuboidal basophilic cells along capillary network.
Acromegaly
excessive growth hormone (somatotrophs=acidophils of pars distalis)
Prolactin secreting tumors
no ovulation= infertility
Most common cause of hypopituitarism in adults
pituitary tumors/adenoma
Primary pituitary destruction
= intrinsic pit destruction
hormone secreting cells in anterior pituitary are destroyed
level of destruction varies.
Poor anterior lobe function
failure of lactation, amenorrhea, poor thyroid function, adrenal insufficiency
Posterior lobe insufficiency
diabetes insipidus= polyuria, polydipsia
No water reabsorption
KNOW THIS (BRS)**
Pineal gland-
1-3. facts about structure/location
4. innervation
5. cell characteristics
- covered by pia matter.
- NO BBB
- Capsule (from pia mater) with trabecula that divide it into lobes
- post ganglionic sympathetic nerves from superior cervical ganglion
- cells are basophilic with irregular nuclei and distinct nucleoli
Pineal gland
contents & function & regulation
- pinealocytes-make melatonin= regulation of sleep cyclen (and serotonin during day, according to BRS)
- glial cells (interstitial cells)
- corpora arenacea= calcium phosphate/carbonate
- External lighting (signals from retinal neurons) inhibit secretion of melatonin
Pinealocytes
- production
- regulation
- Make melatonin
2. External light inhibits melatonin secretion
Pineal gland tumor
restrict flow of CSF through aqueduct of sylvius–>hydrocephalus
thyroid gland
- Embryo (why!?)
- Basic structure
- Endoderm of the cephalic portion of the alimentary canal
2. two lobes connected by isthmus
Thyroid lobe-
- basic structure
- Cell types
- Active vs inactive epithelium?
Lobe is made of follicles that have a SIMPLE CUBOIDAL epithelium = follicular cells (aka principal cells) .
.
Active- more columnar looking
Inactive- more squamous looking
Basal lamina separates CT and follicular cells. CT has lymphatic and capillary network (fenestrated)
Thyroid follicle
- structure
- lining
- function
- Filled with acidophilic colloid (iodinated thyroglobulin—inactive)
- Lined by follicular cells. Parafollicular cells are on same side as basal lamina, but do not make contact with colloid.
- Synthesize, store and release thyroid hormones
Parafollicular cells
- AKA? location?
- Produce/release
- Function?
- Regulation?
- C-cells. in follicle of thyroid (not in contact with colloid)
- Release calcitonin into follicular epithelium or between follicles
- calcitonin- prevent bone resorption (inhibits osteoclast activity) Minor role in regulating calcium resorption
- High blood calcium stimulates secretion, low blood calcium inhibits secretion.
Follicular cells
- structure
- organelles
- secretions
- Regulation
- apical vs basal side?
- Normally cuboidal, columnar when active, squamous when inactive (so when are they cuboidal?!). short blunt microvilli on side of colloid.
- large rER, supranuclear golgi complex, lysosomes and mitochondria
- Synthesis and release of T3/T4
- TSH bind G-protein linked receptors on basal surface of follicular cells.
- Apical= facing colloid, short microvilli;
Basal= close to fenestrated capillaries (where T3/T4 is released)
Thyroid hormone production
occurs in follicular cells of thyroid gland.
- Thyroglubulin is made and glycosylated in rER and golgi.
- Iodide is ACTIVELY transported into cytosol and oxidized in cytoplasm. It enters colloid and iodinates tyrosine residue on thyroglobulin. Then it chills there until needed.
Export of thyroid hormone
- Stimulated by TSH (from ant pit) binding g-protein receptor on follicular cell basal membrane.
- On apical surface, a colloid droplet is endocytosed and fuses with lysosome.
- Lysosome digests and releases T3/T4 which exit via basal side.
Thyroxine vs triiodothyronine vs thyroglobulin?
T3=triiodothyronine
T4= thryoxine
Thyroglobulin- pre-cursor to thyroid (before iodination)
Function of thyroid hormone?
- stimulates overall increase in metabolism= heat.
- stimulates transcription of certain genes
- INCREASE carb metabolism, fatty acid synthesis
- DECREASE cholest, phospholipid, TAG synthesis
Hyperthyroidism symptoms.
weight loss, increased heart rate, metabolism, respiraiton and appetite.
can cause muscle tremors, tiredness, frequent or excessive menstrual bleeding
Follicular hyperplasia
- what is it?
- cause?
- Swollen thyroid= goiter
- iodine deficiency= low T3/T4 –> increased TSH –> follicular hyperplasia
(thyroid makes stuff and puts it in colloid, but can’t iodinate it so it’s there forever)
- *not associated with hypo/hyper thyroidism.
- *treated with iodine.
grave’s disease
Immunological disease that makes Ig similar to TSH= hyperthyrdoisism
Hashimoto’s disease
autoimmune destruction of thyroid= hypothyroidism. Germinal centers made of lymphocytes.
Thyroid peroxidase antibodies produced
Prevalence of thyroid cancer in men vs women
women x4
Myxedema
Can occur in hyper or hypo thyroidism
localized skin swelling
Parathyroid gland
- location
- gland characteristics
- types of cells
- blood supply
- Behind thyroid (4 glands)
- Each gland has its own capsule that create septa
- Principal (chief) cells and oxyphil cells
- blood vessels run in septa
Principal cell/Chief cell
- production
- characteristics
- regulation
- Parathyroid hormone
- irregular granules
- inhibited by high blood Ca+2
Oxyphil cells
- characteristics
- Function
- relation to age?
- larger, eosinophilic (due to mitochondria)
- unknown function,
- appear after puberty and increase with age
hyperparathyroidism
- causes (most common)
- Symtpoms
- adenoma (80%), carcinoma (1-2%) and hyperplasia (15)
- high blood calcium, low PO4. Bone cysts can develop, rubbery bones, kidney stones, pancreatitis, peptic ulcers and hypertension
PTH -3 distinct functions to accomplish goal
All increase calcium levels
- calcified bone matrix is resorbed)
- increased calcium resorption in kidney distal tubule, increased phosphate secretion
- Stimulates Vit D synth–>increased synth of calcium binding proteins–> increased calcium absorption in intestines
Hypoparathyroidism
decreased serum Ca and increased PO4
Tetany, muscle cramps, jaw locks, exaggerated tendon reflexes
Adrenal glands
- structural characteristics
- embryological origin
- collagenous capsule embedded in fat-medulla and cortex
- Medulla= from ectoderm neural crest cells
Cortex= mesoderm
Adrenal cortex
3 zones of adrenal cortex (outside–>inside)
zona glomerulosa, zona fasciculata, and zona reticularis
Synthesize and secrete hormones—they are NOT stored
Zona glomerulosa
- secretion
- regulation
- cell characteristics
- blood supply
- mineralocorticoids= aldosterone
- stimulated by angiotensin II and ACTH
- cells have lots of sER and mito with shelf-like cristae
- fenestrated capillary network
Zona fasiculata
- secretion
- regulation
- cell characteristics
- blood supply
- Glucocorticoids= cortisol, corticosterone
- ACTH stimulates production/secretion
- Cell columns with sinusoidal capillaries perpendicular to capsule. Cells are called spongiocytes due to extensive lipid droplets. Mitochondria are spherical with tubular and vesicular cristae. contain LIPOFUSCIN pigment granules
- discontinuous fenestrated capillaries
Zona Reticularis
- secretion
- regulation
- cell characteristics
- blood supply
- gonadocorticoids= DHEA and adrostenedione
- ACTH stimulates
- arranged in anastomosing cords
- discontinuous fenestrated capillaries
lipofuscin pigment granules can be found?
in zona fasciculata and reticularis of adrenal cortex.
Cells of adrenal medulla
- chromaffin cells
2. sympathetic ganglion cells
Chromaffin cells
- function
- staining
- arrangement
- characteristics
(in adrenal medulla)
- Synthesize, store and secrete catecholamines= epinephrine and norepinephrine
- Stain with chromaffin salts
- arranged in short irregular cords with extensive capillary network –reticular fiber support
- Granules containing: catecholamine, ATP, enkephalins, chromogranins
Chromogranins
binding proteins for epinephrine and norepinephrine that are found within the granules of chromaffin cells in the adrenal medulla
Chromaffin cell activation
- emotional stimuli mediated by the preganglionic sympathetic fibers innervating the chromaffin cells.
Blood supply of adrenal medulla
Venous= rich in hormones, reaches via fenestrated capillaries going through the cortex
Arterial= fenestrated network from capsular arteries
Medullary veins join to make suprarenal vein.
Pheochromocytoma
Tumor of the adrenal medulla that causes hyperglycemia and transient BP elevations. most common adrenal tumor in adults
Most common adrenal tumor in adults? children?
pheochromocytoma= adults neuroblastoma= children
Neuroblastoma
tumor in adrenal gland of children, no effect on BP
Cushing syndrome
excess cortisol secretion
can cause hirsutism= male hair
Conn’s Syndrome
Excess Aldosterone production= increased H2O retention–>hypertension and hypokalemia
Addison’s disease
Adrenocortical insufficiency= weakness, nausea, weight loss
High ACTH levels, causes hyperpigmentation
Waterhouse-friderichsen syndrome
Acute cortical destruction. meningococcal sepsis, endotoxic shock.