Endocrine Histo Flashcards
Define endocrine cells.
Cells that secrete hormones into the bloodstream for transport to target organs
What are the 3 types of hormones?
- Steriods - (e.g. gonadal and adrenocortical hormones)
- Small Peptides, proteins, and glycoproteins
- Amino Acid Derivatives (catecholamines) and Iodinated Amino Acids (thyroid hormones) and Arachidonic acid derivatives (prostagladins)
What is the main purpose of hormones?
- Maintain homeostasis
- coordinate growth and development
What are the two ways that hormones can communicate their signal within the cell?
- Cell Surface receptors
2. Intracellular Receptors
T or F: the ovaries, testes, and islets of the pancreas are all have endocrine function.
True
T or F: the pituitary, thyroid, parathyroid, and adrenal glands all have endocrine function.
True
The pituitary is an amalgam of what two tissues?
- structures formed by these
- location
- origin
- Ectoderm
- Rathe’s pouch
- anterior lobe (adenohypophysis)
- grows upward from the roof of the mouth - Neuroectoderm
- no specific name
- posterior lobe (neurohypophysis)
- envaginates from the brain
What two parts make up the posterior lobe?
- Infundibulum
2. Pars Nervosa
What three parts make up the anterior lobe?
- Pars Distalis
- Pars Intermedia
- Pars Tuberalis
What stains lighter in H and E, the anterior or posterior lobe?
Posterior is lighter
Paraventricular nucleus
- What is it?
- Where is it?
- What does it secrete?
- Function of Secretion?
- Soma of a neuron whose nerve fibers contribute to the hypothalmohypopseal tract that travels
- Soma = Hypothalmus (its fibers travel through INFUNDIBULUM to synapse IN the POSTERIOR pituitary
- Secrete ADH (Anti-diuretic hormone aka vasopressin)
- ADH - Regulates body retention of water
How does vasopressin affect retention of water?
- Increases water channels in the walls of kidney connecting ducts
What is caused by inadequate vasopressin levels?
- Diabetes insipidus
- Because you aren’t making channels to reabsorb enough H2O,
- Symptom = intense thirst
Supraoptic nucleus
- What is it?
- Where is it?
- What does it secrete?
- Function of Secretion?
- Soma of a neuron whose nerve fibers contribute to the hypothalmohypopseal tract that travels
- Soma = Hypothalmus (its fibers travel through INFUNDIBULUM to synapse IN the POSTERIOR pituitary
- Oxytocin
- oxytocin - Stimulates Uterus smooth muscle, and Myoepithelial cells in mammary gland
What is formed by the fibers of the paraventricular nucleus and the supraoptic nucleus?
Hypothalmohypopseal Tract
What are Herring Bodies?
- location
- Secretory Vesicles
- Near the end of the paraventricular and supraoptic axon terminal
What surrounds the Herring Bodies?
Pituicytes
What is the difference in the types of hormones secreted by acidophils and basophils?
Acidophils - Growth Hormones
Basophils - Tropic Hormones
What are the 3 types of hormones secreted by Basophils?
- what hormones are part of these types?
- Gonadotropes
- FSH
- LH or ICSH (interstitial cell-stimulating hormone) - Thyrotropes
- TSH (thyroid stimulating hormone) - Corticotropes
- ACTH (adenocorticotropic hormone)
***the “tropes” regulate the activity of other glands
What are the 2 hormones secreted by Acidophils?
- Somatotropes
- GH (growth hormone) - Lactotropes
PRL (prolactin)
What does FSH do?
- Cell type that secretes
Stimulates:
- Follicular developement in ovary
- Spermatogenesis in testes
Gonadotropes => Basophils
What does LH do?
- Cell type that secretes
Stimulates:
- Final maturation of ovarian follicle, ovulation, and copus luteum
- Essential for continued secretion of androgen from Leydig Cells
Gonadotropes => Basophils
What does TSH do?
- Cell type that secretes
Stimulates:
- Growth of thyroid epithelial Cells
- Release of Thyroglobulin and Thyroid hormones
Basophils
What does ACTH do?
-Cell type that secretes
Stimulates:
- Secretion of Glucocorticoids in adrenal gland
What does GH do?
- Cell type that secretes
Stimulates:
- OGF-1 (insulin-like growth factor) production by liver and other organs => Division of Progenitor Cells in growth plates and skeletal muscles
- Net Effect = Growth of the body
What does PRL (prolactin) do?
- Promotes Mammary Gland Developement
- Initiates milk formation
- Stimulates and maintiains secretion of Casein, Lipids, and Carbohydrates in the Milk
What is caused by hypersecretion of GH in tumors?
Gigantism and Acromegaly
Between Pars Intermedia and Pars Tuberalis, which of the following features are common or different?
- Location
- Cell type
- Function
- Tissue surrounds series of small cavities, the residual lumen of Rathke’s pouch
Pars Intermedia:
- Basophils and Chromophils
- Function unclear
- Has Colloid Follicles
Pars Tuberalis:
- cells are immunoreactive for ACTH, FSH, LH
- no cell type or function specified
T or F: the pineal gland, pineal body, and epiphysis cerebri are all the same thing
True
What are the primary cell types of the pineal gland?
- Pinealocytes (95% of total)
2. Interstitial (glial) Cells
What is Brain Sand?
Calcium, phosphates, and carbonates plus protein
What is the pineal gland?
- function (what does it respond to?)
- hormones
- Photosensitive Organ that regulates circadian rhythms in the body by obtaining information about light and dark cycles (endocrine)
- Daylight inhibits Melatonin output
- Sympathetic nn. Stimulated at night
Melatonin
- How does it work?
- Disorders?
- Inhibits gonadotropin releasing hormone from the hypothalmus and may promote sleepiness
- Involved in Seasonal Affective Disorder
What are tumors in the pineal gland associated with?
Percocious Puberty
What is the functional unit of the thyroid?
- Size
- Arrangment
- Hormone production
Thyroid Follicle (Follicular cells + Colloid)
- 0.2 - 1.0 mm in diameter
- Colloid surrounded by follicular cells
- Capillary networks (extensive) surround
Follicular cells
- Produce T4 and T3
Colloid
- Thyroglobulin (inactive storage of T4 and T3)
What is the purpose of T3 (triiodothryronine) and T4 (tetraiodothryonine)?
- Describe formation
** Regulate Basal Metabolism
- Thyroglobulin is released from follicular cells and goes outside the apical side of the cell
- It binds iodine outside and Pre-T3 and Pre-T4 are made
- Follicular cell endocytoses Pre-T3 and Pre-T4 into vesicles
- Vesicle fuses with lysosome which degrades the vesicle to produce T3 and T4
- Vesicles fuse on basal side and T3 and T4 go into bloodstream
What is the structure of T3 and T4, which is more abundant?
T4 more abundant
- they consist of 3 or 4 iodine atoms attached to 2 molecules of tyrosine
T or F: Thyroid gland function is essential for normal growth and development
True
What happens if there is a thyroid deficiency during fetal life?
Severe CNS damage
What causes hypothyroidism?
- symptoms
- Insufficient dietary Iodine
- auto immune dieseases (Hashimoto’s thyroiditis)
symptoms:
Mental and Physicial sluggishness and edema of CT
What causes hyperthyroidism (Graves’ disease)?
-symptoms
- Excessive hormones in circulation
- autoimmune disease - abnormal levels of antibodies bind to and stimulate FOLLICULAR cells to produce increased levels of thyroid hormones
symptoms:
Bulging eye balls (increased CT behind them)
Increased sympathetic activity
What hormones are released from the thyroid gland?
- T3 and T4
- Calcitonin
What produces Calcitonin and what is its function?
- location of cells
- where does it get deposited
- Parafollicular Cells (c-cells) - adjacent to follicular cells
- Calcitonin - lowers blood calcium
- NOT deposited into the colloid of follicles, secretion is carried by blood to the CT
What 4 small endocrine glands are closely associated with the thyroid gland?
Parathyroid Gland
What two cell types exist in the parathyroid glands and what are their features?
- Which is more numerous
- function of cell types
Principal and Oxyphil Cells
Principal (Chief) cells:
- More numerous
- small
- less cytoplasm
- Secretes PTH
Oxyphil cells:
- larger
- eosinophilic cytoplasm
- organized into clumps
- LOTs of Mitochondria
- UNKNOWN function
**Sometimes oxyphil cells can have low levels of PTH synthesis
What does PTH do once secreted by principal (Chief) cells?
- how does it do this?
- Regulates Ca2+ and Phosphate levels in blood
How:
- increases Ca2+ by production in the kidney
- Bone Resorption
- Urinary phosphate excretion
What are the 3 kinds of cells in the islets of langerhans and what do they secrete?
- A cells - secrete glucagon
- B cells (70%) - secrete insulin
- D cells - secrete somatostatin
Where are A cells normally located in the islets?
Near the boundary of the islets
**NOTE with H and E you can’t really differentiate between the different cells in the islets
What is the function of each of the islet hormones?
- Insulin
- stimulates glucose uptake
- storage of glucose
- stimulates EXOcrine secretion of the pancreas via local effects - Glucagon
- Stimulates glycogen breakdown
- Gluconeogenesis
- Inhibits exocrine secretion of the pancreas via local effects - Somatostatin
- Inhibits both insulin and glucagon secretion
- NO CLEAR FUNCTION IN ISLETS
What 3 zones make up the adrenal cortex?
- Zona Glomerulosa
- Zona Fasciculata
- Zona Reticularis
What is the blood supply to the adrenal cortex and medulla?
Cortex:
- Lots of Small arteries from Supra Renal vessels
- Vessels organize adrenal gland structure
Medulla - DUAL BLOOD SUPPLY:
- Arterial Blood via Medullary arterioles
- Venous blood from cortical Sinusoidal Capillaries
In general what is secreted by the Adrenal Cortex?
Steriods
What is secreted by each of the 3 layers of the Adrenal Cortex?
- function of hormones
- Zona Glomerulosa - MINERALOcorticoids
- Regulate Na and K balance
- H2O homeostatsis
- e.g. Aldosterone - Zona Fasculata - GLUCOcorticoids
- Regulate glucose synth and glycogen formation
- Depress Immune function and Inflammation
- e.g. Cortisol (hydrocortisone) - Zona Reticularis - Weak androgens (sex hormones) and small amount of glucocorticoids
What does the adrenal medulla secrete?
Catecholamines (epinephrine, norepinephrine)
How can the medulla of the adrenal gland be characterized in histological section?
- Large Medullary Veins
- Pale staining Cells
What cell type is predominant in the medulla?
- staining characteristics
Chromaffin (medullary) Cells
- Large Pale Staining Cells
Describe the dual Blood Supply of the medulla of the adrenal gland.
- Sinusoids and arterioles from cortex supply the medulla - VENOUS BLOOD
- Medullary capillaries and arterioles also supply the medulla - ARTERIAL BLOOD
Chromaffin Cells
- Stimulated by
- Contents
- Hormone(s)
- Catecholamine Secreting cells of the Medulla
- They are modified neurons that are Innervated by Sympathetic (Autonomic)
nervous system - Filled with secretory vesicles containing epinephrine and norepinephrine
What differences exist between vesicles containing epinephrine and norepinephrine in chromaffin cells.
Norephinephrine - dense core vesicles
Epinephrine - smaller, clear vesicles
What does epinephrine release cause?
Adrenal Rush
Increased:
heart rate, BP, Sweating, Dilation of Bronchioles,
Decreased:
Blood flow to viscera and skin, digestion (and prod. of digestive enzymes), urine production
Besides Chromaffin cells, what other cells are contained in the medulla?
- Features?
- Amount?
Ganglion Cells
Axons extending into cortex that regulate:
- Secretory Activity
- Innervate Blood Vessels
Relatively few of these compared to chromaffin cells in medulla
How are hormones regulated?
By the hypothalmus and pituitary
Describe the communication between the hypothalmus and pituitary that leads to hormone release.
- Endocrine neurons in HYPOthalamus secrete RELEASING HORMONES/factors.
- Portal Vein transports these to ANTERIOR pituitary
What do releasing hormones do?
- Control the release of Basophils and Acidophils in the ANTERIOR pituitary
**Note: these are released in spurts
What two distinguishing features of the Pars Nervosa?
- Herring Bodies
2. Capillaries
What 3 cell types distinguish the pars distalis?
- which are functionally different, why?
- Acidophils
- Basophils
- Chromophobes
*Acidophils and Basophils are functionally different. Chromophobes are likely acidophiles or basophils that have lost their granules
T or F: endocrine is a relatively slowly moving system
True
Which part of the pituitary is derived from ectoderm?
Anterior Lobe (this makes sense, because it is not the part conducting the nerve fibers like the posterior lobe)
Which of the pituitary lobe has a higher cell density and stains darker?
Anterior pituitary (adenohypophysis)
T or F: the pars tuberalis is part of the infudibulum
False, pars tuberalis is derived from anterior pituitary ectoderm while the infudibulum is part of the posterior pituitary neuroectoderm
Hormones secreted into the blood in the posterior pituitary actually came from where?
- Supraoptic and Paraventricular nuclei
Lack of what pituitary hormone would cause excessive thirst and why?
ADH - posterior pituitary
It upregulates the amount of water channels in the kidney tubules
What are two defining feature of Pars Nervosa in histological section?
- Herring Bodies
- Capillaries
T or F: chromophobes have a distinct function outside of acidophils and basophils
False, they are just an artifact of fixing the histological section
_______ typically has acidophils, basophils, and chromophobes in sections, but _______ typically only has basophils and chromophobes.
Pars Distalis (has all three) Pars Intermedia (only 2)
What feature is specific to Par Intermedia?
Colloid Follicles
What are the two components of a thyroid follicle?
Colloid + Follicular Cells
What is used to treat graves?
- how does this work
Radioactive iodine is used to kill thyroid cells because they absorb iodine
Compare parafollicular cells to follicular cells in histo. section.
Parafollicular are lighter and larger
What cells have a function opposite to that of parafollicular cells?
Prinicpal cell release (ParaThyroid Hormone)
Parafollicular cells release (Calcitonin)
What is located in the zona glomerulosa?
Webbed arterioles
What is located in the zona reticularis?
- Shade of cells relative to zona glomerulosa and zona fasiculata?
Webbed Venules
- Cells are darker
PITUITARY BLOOD FLOW????
??????????
Where do releasing hormones come from?
Hypothalmus
What does GnRH (gonadotropin releasing hormone) do?
- causes release of gonadotropes - FSH and LH
What does TRH (thyroid releasing hormone) do?
- causes release of thyrotropes - TSH
**ALSO stimulates PRL (prolactin) release
What does CRH (corticotropic releasing hormone) do?
- Causes release of corticotropic hormones - ACTH
What hypothalmic hormones regulate Lactrope (PRL-prolactin) release?
- VIP - stimulates release from pituitary
- Dopamine - prevents release from pituitary
What hypothalmic hormones regulate Somatotrope (GH) release?
- GHRH- stimulates release from pituitary
- Somatostain - prevents release from pituitary
