Endocrine System Flashcards
What are considered to be the “classical” endocrine glands?
Hypothalamus Anterior and posterior lobes of pituitary Thyroid Parathyroid Adrenal Cortex Adrenal Medulla Gonads Placenta Pancreas (both endocrine and exocrine) Pineal gland
(T/F) The kidney also has important endocrine functions
True
Steroid hormones are derived from what general precursor?
Cholesterol
Peptide and protein hormones are synthesized from what?
Amino Acids
Peptides modified by addition of carbohydrate groups are known as what?
Glycoproteins
Amine hormones are modified derivatives of what amino acids?
Tyrosine or Tryptophan
The pituitary gland is also known as what?
Hypophysis
What are two parts of the pituitary gland?
Adenohypophysis (anterior lobe)
Neurohypophysis (posterior lobe)
The anterior lobe of the pituitary gland is also known as what?
Adenohypophysis
The posterior lobe of the pituitary gland is also known as what?
Neurohypophysis
Synthesis and secretion of all pituitary hormones is controlled by what part of the brain?
Hypothalamus
The pituitary gland lies in a shallow depression known as the _______, which is a saddle-shaped part of the ________ bone.
Sella Turcica;
Sphenoid bone
How is the adenohypophysis connected to the hypothalamus
Blood vessels: Hypophysial portal circulation
The pituitary gland lies beneath the…
Hypothalamus
The adenohypophysis is embryologically derived from what?
Rathke Pouch
Why do endocrine gland typically have a large blood supply?
Blood supply is method of delivery of hormones to distant target tissues
What are some examples of steroid hormones?
Estradiol
Testosterone
Cortisol
Aldosterone
What are some examples of peptide and protein hormones?
Prolactin
Growth Hormone
Insulin
Vasopressin
What are some examples of glycoprotein hormones?
LH
FSH
TSH
What are examples of amine hormones derived from tyrosine?
Thyroid Hormone
Norepinephrine
Epinephrine
What are examples of amine hormones derived from tryptophan?
Melatonin
What is Rathke’s pouch?
Hypophysial diverticulum: An evagination of the oral ectoderm that extends upward from the roof of the primordial oral cavity to form the Adenohypophysis
The neurohypophysis is embryologically derived from
Neurohypophysial diverticulum: a down growth from the floor of the diencephalon
The neurohypophysial diverticulum is a down growth from the floor of what?
Diencephalon
The diencephalon is made up of what parts?
Thalamus
Hypothalamus
Pineal Body
What is the name of the downgrowth of the hypothalamus?
Median Eminence of Hypothalamus
What are the subdivisions of the adenohypophysis?
Pars distalis
Pars intermedia
Pars tuberalis
What is the main body of the neurohypophysis also known as?
Pars nervosa
Cell types of the Pars distalis are divided into two categories, what are they?
1) Chromophil Cells
2) Chromophobe Cells
Chromophil cels, a type of cell within the Pars distalis of the adenohypophysis, can be further divided into two cell types. What are they?
- Acidophils
- Basophils
Acidophil cells within the Pars distalis can be described as what?
- Most numerous cell type
- Red-staining cytoplasmic granules
There are two types of acidophilic chromophil cells, what are they?
- Somatotrophic cells
- Mammotrophic cells
Somatotrophic cells synthesize and secrete what?
Growth Hormone - the most important hormone for normal growth; also has important effects on protein, carbohydrate, and fat metabolism.
What do the mammotrophic cells of the Pars Distalis synthesize and secrete?
Prolactin - the major hormone responsible for milk production; also important in normal development of breast glandular tissue.
How would you describe basophillic Chromaphil cells of the pars distalis?
-Less numerous, blue-staining cytoplasmic granules
What are the types of Basophillic Chromophil cells of the Pars Distalis?
- Thyrotrophic cells
- Corticotrophic cells
- Gonadotrophic cells
What do the thyrotrophic basophilic chromophil cells synthesize and secrete?
synthesize/secrete thyroid stimulating hormone (TSH), which stimulates growth and activity of thyroid hormone-secreting cells of the thyroid gland
What do corticotrophic cells synthesize and secrete?
synthesize/secrete adrenocorticotrophic hormone (ACTH), which stimulates growth and activity of steroid hormone-secreting cells of the adrenal cortex
What do gonadotrophic cells synthesize and secrete?
synthesize/secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH), which regulate growth and activity of ovaries and testes, including secretion of the sex steroids, estrogen and testosterone
How would you describe Chromophobe cells of the Pars Distalis?
exhibit only faint/weak staining, and probably represent committed stem cells and immature forms of acidophils and basophils, as well as degranulated acidophils/basophils
Cells of the pars distalis are arranged in “__________” surrounded by numerous _____________ and _________ fibers
- clumps
- fenestrated capillaries (plus other small vessels)
- thin connective tissue
What type of capillaries are found in the pars distalis?
fenestrated
How would you describe the Pars Intermedia of the Adenohypophysis?
-contains colloid-filled follicles/vesicles (remnants of lumen of Rathke’s pouch) and melanoyte stimulating hormone (MSH) secreting cells –MSH is a relatively unimportant hormone in humans
How would you describe the Pars Tuberalis of the Adenohypophysis?
surrounds the infundibular stem, contains some cell types in common with the pars distalis and a few other cell types with unknown function
Which portion of the Adenohypophysis represents remnants of the lumen of Rathke’s pouch?
Pars Intermedia
The median eminence of the hypothalamus contains what?
Hypothalamic neurons with terminals in the median eminence. These neurons secrete regulatory hormones for anterior pituitary cells.
Which artery supplies the pars tuberalis of the adenohypophysis?
Super Hypophysial artery
Immuno-staining allows for the identification of what?
Hormone-specific cell types
Where does the blood supply come from that reached the anterior pituitary?
Hypothalamus
Primary capillary plexus surrounding median eminence -> hypophysial portal veins -> capillary plexus of pars distalis
The primary capillary plexus is a dense capillary plexus surrounding what?
Median Eminence of the Hypothalamus
How do hormones secreted by cells of the pars distalis reach the rest of the body?
Venous Drainage into systemic circulation
The hypothalamohypophyseal tract contains the unmyelinated axons of __________ whose cells bodies are located in the ________ and _________ of the hypothalamus.
Neurosecretory cells
Supraoptic
Paraventricular nuclei
What does the hypothalamohypophyseal tract transport to the pars nervosa?
Oxytocin Antidiuretic hormone (ADH; vasopressin)
The pars nervosa contains the distal ends of what?
hypothalamohypophyseal tract axons and is the site where neurosecretory granules in these axons are stored in accumulations known as Herring Bodies
The axon terminals of the Neurohypophysis are supported by glial cells called what?
Pituicytes
What is the blood supply which primarily supplies the pars nervosa?
Inferior hypophysial artery
What are stored in Herring Bodies?
vasopressin
oxytosin
The cell bodies which synthesize and secrete Vasopressin/Antidiuretic hormone (ADH) are predominantly found where?
In the Supraoptic nuclei of the hypothalamus
The cell bodies which synthesize and secrete Oxytocin are found where?
In the Paraventricular nuclei of the hypothalamus
What are the main actions of vasopressin?
- Regulation of plasma osmolarity through changing water permeability in the collecting tubules of the kidneys
- Constriction of arterioles (smooth muscle contraction)
What are the main actions of oxytocin?
- Stimulate myoepithelial cells contraction in milk let-down reflex
- Stimulate contraction of uterine smooth muscle during labor
What causes gigantism?
Growth-hormone secreting adenomas in adenohypophysis present before closure of growth plates
or
acromegaly when they develop after long bone growth has ceased
What causes Cushing’s disease?
ACTH-secreting adenomas resulting in continuous stimulation of the adrenal cortex (hypercortisolism)
What is galactorrhea?
Milk oozing from nipples
What causes galactorrhea?
Prolactin-secreting adenomas
Besides galactorrhea, what else do prolactin-secreting adenomas cause?
Hypogonadism/infertility in both males and females.
What is panhypopituitarism?
Failure of all anterior lobe hormone producing cells
Isolated hGH deficiency in children results in what?
Decreased rate of linear growth, short stature, mild obesity, and often delayed puberty
What does Vasopressin (ADH) deficiency lead to?
Central (neurogenic) diabetes insipidus–in the absence (or severe deficiency) of ADH, the collecting ducts cannot reabsorb water, so excess water is excreted in urine (as much as 10-12 liters per day). When water is being excreted faster than it can be replaced (by drinking), the salts/minerals in extracellular fluids (like plasma) become increasingly concentrated, resulting in hyperosmolarity.
In general, what are the functions of thyroid hormones?
- regulation of metabolism and basal metabolic rate
- effects on growth and development
- cardiovascular function
- maturation of the CNS
What cells are scattered between thyroid follicles?
Parafollicular cells (C-cells)
Where are parafollicular cells derived from and what do they secrete?
- Derivation: Neural Crest
- Secrete: Calcitonin (calcium homeostasis)
What type of epithelium are thyroid follicular epithelial cells?
Simple cuboidal epithelium
What are the thyroid hormones?
T3 (tri-iodothyronine)
T4 (Thyroxine)
The thyroid hormones contain what?
contain iodine, so sufficient iodine must be supplied by diet and most of this iodine must be “trapped” in the thyroid gland
Where are T3 and T4 stored?
extracellularly attached to thyroglobulinin colloid until the gland is stimulated to secrete. When secretion is stimulated, the hormones must first be brought back into follicular cells by endocytosis and then secreted across the basilar membrane and absorbed into capillaries.
Low power view of the thyroid gland shows many_________ –lined by___________ cells and containing _______ (homogenously pale staining). Collagenous _______ (mostly sheared apart in this section) divide the gland into lobules and convey blood vessels, lymphatics.
follicles
thyroid follicular
colloid
septae
What happens to the epithelium as thyroid follicles become more or less active?
More active = height increases (cuboidal to columnar)
Less active = height decreases
What is the normal stimulus for follicular cell activity of the Thyroid gland?
TSH
What is Thyroglobin (TG)? Where is it synthesized? Where is it secreted?
a glycoprotein containing large quantities of tyrosine, is synthesized on the RER and Golgi apparatus of follicular cells ——-> secreted across the apical membrane into the follicular lumen
T3 binds to what in target cells?
Nuclear receptors
Why are heart arrhythmias and increased cardiac oxygen demand among effects of hyperthyroidism?
If essentially all cells are going to increase energy usage, then it stands to reason that the cardiovascular system must be “turned up” by thyroid hormone in order to deliver more oxygen and energy substrate to the rest of the body.
Thyroid hormone is also necessary for ____________ –untreated hypothyroidism in childhood results in _______, despite normal hGH.
normal growth
decreased linear growth
Thyroid hormone is also necessary for ___________ during a critical period in the first months after birth.
normal maturation of the CNS
Undiagnosed / untreated congenital hypothyroidism results in irreversible ____________.
failure of CNS maturation (cretinism)
Grave’s disease is caused by what?
Hyperthyroidism
TSH receptors on thyroid cells are also activated by what?
Thyroid stimulating immunoglobuins
-antibodies against the TSH receptor –> immunoglobulin G (lgG) fraction of plasma proteins
What effect do “thyroid stimulating immunoglobulins have on TSH receptors?
Same as TSH itself (increased cAMP) —> results in continuous stimulation of the thyroid gland, just as if TSH levels were continuously elevated –> increased T3/T4 synthesis and secretion, hypertrophy/hyperplasia of the gland –> hyperthyroidism and goiter (enlarged thyroid).
A patient who comes to you with exopthalmos, thyroid stare, and diffusely enlarged thyroid gland most likely has what?
Grave’s disease
Histologically, how does a section of a normal thyroid differ from one with Grave’s disease?
Grace’s disease thyroid shows:
follicular cell hyperplasia and crowding, depletion and scalloping of colloid
What does dietary deficiency of iodine cause?
Hypothyroidism
- cannot synthesize thyroid
Lack of ________ results in persistent elevation of ______. Thyroid follicular cells respond by ________ and storing ___________ in follicles which leads to __________ of the thyroid gland or goiter
negative feedback TSH growing/dividing thyroglobulin diffuse enlargement
What is Hashimoto’s Thyroiditis?
Common form of thyroiditis (inflammation of the thyroid gland
Treatment of hypothyroidism includes…
treatment of the underlying cause (if possible) and thyroid hormone replacement –given by mouth as T4 (thyroxine).
What are parafollicular cells (C-cells)?
Larger, pale-staining cells found adjacent to / between thyroid follicles
Regarding the parathyroid gland, there are normally _____ superior parathyroids from __________ and _____ inferior parathyroids from ________.
4 to 2
4th pharyngeal pouch
2
3rd pouch
What is the location of the the parathyroid glands?
Posterior surface of the thyroid gland
What does the Parathyroid gland synthesize/secrete? Which does what?
Synthesize/secrete parathyroid hormone (parathormone or PTH) -increases free ionized calcium concentration in blood –PTH is critical for calcium regulation
As people age, what can be found scattered throughout the parathyroid glands?
Adipocytes
The main cells seen in the parathyroid glands are________ or________ cells, which are small cells with ________staining cytoplasm. These are the cells which are known to detect blood ___________ concentration and synthesize/secrete _______.
“principal” / “chief”
scant blue
calcium
PTH
A second cell type in the parathyroid, besides chief cells, are _______, which can also be readily seen as clusters of ________ cells with __________ cytoplasm. The functional significance of these cells are poorly understood.
oxyphil cells
larger
abundant pink-staining
What types of sensor do cheif cells have on their cell membranes?
Calcium sensors
Cheif cells secrete what?
PTH
What target tissues are PTH receptors found on?
Osteoblasts
Renal tubular epithelial cells
What effect does PTH have on osteoblasts?
after PTH binding, osteoblasts stimulate osteoclasts to reabsorb bone, mobilizing calcium and phosphate
What effect does PTH have on renal tubular epithelial cells?
a) PTH binding promotes decreased urinary calcium excretion, increased phosphate excretion
b) PTH up-regulates the renal enzyme for activation of Vit D, increases GI absorption of calcium and phosphate
primary hyperparathyroidism causes what?
commonly due to parathyroid adenoma (or chief cell hyperplasia), excess PTH secretion leads to “stones, bones and groans”
Stones –urinary tract stones occur due to increased urinary calcium (even though the direct effect of PTH is to decrease urinary calcium excretion, the plasma calcium rises enough to saturate tubular reabsorption of filtered calcium)
Bones –excess PTH promotes bone demineralization
What encloses the Adrenal glands?
Renal Fasicia
The adrenal glands are surrounded by what?
Perirenal fat
What hormones are known as the catecholamines?
Norepinephrine
Epinephrine
What features are common to all three layers of the Adrenal glands?
abundant mitochondria, lipids (including vesicles containing cholesterol esters) and smooth endoplasmic reticulum; mitochondria with tubular cristae –features of steroid-producing cells in general.
The Z. glomerulosa cells, compared to the fasciculata cells, are characterized by …
Less cytoplasm and fewer lipid droplets
What is synthesized in the Z. Glomerulosa? What is its action?
mineralocorticoids, principally aldosterone –the main action of aldosterone is increased sodium and water reabsorption in renal collecting ducts (results in increased ECF volume —> increased blood pressure)
The Zona fasciculata cells of the adrenal gland is the widest of the zones and is arranged how?
In parallel cords or plates (typically 2 cells thick) and is separated by capillaries parallel to the plates.
What is characteristic about the Zona Fasciculata zone compared to the other zones?
More cytoplasm than cells in the other zones and abundant lipid droplets
What does the Zona fasciculata cells synthesize and secrete? Which fuctions to do what?
Synthesize / secrete glucocorticoids, primarily cortisol –critical for normal carbohydrate metabolism, maintenance of blood sugar between meals/ fasting, adaptation to stress, maintenance of blood pressure (permissive effect on catecholamines)
The adrenal cortex is subdivided into what 3 layers?
Z Glomerulosa (outermost)
Z. Fasciculata
Z. Reticularis (innermost)
The Z Reticularis cells of the Adrenal Cortex are arranged how? And are surrounded by what?
- Arranged in irregular branching network cellular chords
- Surrounded by blood vessels and connective tissue
The Z. Reticularis cells of the Adrenal cortex synthesize and secrete what?
adrenal androgens
androstenedione and DHEA
How would you describe the blood supply of the adrenal gland?
The blood supply of the adrenal gland “mirrors” the cell arrangement of the zones
–capillaries: in
“loops” around z glomerulosa clusters, parallel to plates of z fasciculata cells and irregularly branching in the z reticularis;
also bathes successive layers in secretions and intermediates from other layers.
What system regulates aldosterone? Which is important for what?
renin-angiotensin-aldosterone system (RAAS)
–important response to decreased blood pressure / decreased renal perfusion
What is involved in cortisol regulation?
hypothalamic-hypophysial-adrenal cortical axis (CRH –> ACTH –> Cortisol)
What is involved in adrenal androgen regulation?
largely by ACTH (synthesis of androgens is increased when ACTH levels are elevated, as in Cushing’s disease) but not completely understood
What is addison’s diease?
Destruction of the adrenal cortex (autoimmune, tuberculosis)
All adrenal steroids are affected –mineralocorticoids, glucocorticoidsand androgens –mineralocorticoidsand glucocorticoidsare necessary for life
What is Cushing’s diease?
ACTH-secreting adenoma of the anterior pituitary
High ACTH –> drives cortisol and androgen synthesis/release
What is Cushing’s syndrome?
Functional tumor of the adrenal cortex OR administration of glucocorticoids in pharmacological doses (High cortisol –> negative feedback inhibition of pituitary ACTH release)
What is Conn’s Syndrome?
Adrenal cortical adenoma of glomerulosa cells which leads to Hyperaldosteronemia
The suprarenal medulla contains ____________ and large_______draining into a large_________.
medullary cells (pheochromocytes) venous channels central vein.
What are Pheochromocytes?
Modified post-ganglionic sympathetic nerve cells (neural crest origin) in the suprarenal medulla.
Catecholamines, once made by the adrenal medulla, are packaged and stored in what?
Secretory graunles
Besides the Pheochromocytes, what other cells are located in the suprarenal medulla? What do they do?
two types of medullary cells –most synthesize / secrete epinephrine (E) and a smaller population secretes norepinephrine (NE)
How would you histologically describe Pheochromocytes of the Suprarenal medulla?
seen as large cells in clusters, with abundant finely granular cytoplasm staining faintly basophilic (blue) with standard H&E stain
Pheochromocytes stain a yellow-brown color with _________ (sometimes called “_________ cells”)
chromic salts
chromaffin
What type of nerves control medullary cells?
Preganglionic sympathetic
Pheochromocytomas are what? Which produce what?
Tumors of suprarenal medullary cells. They produce symptoms related to excess catecholamines (“fight or flight”) including tachycardia / palpitations, elevated blood pressure (sometimes dangerously elevated), chest pain, sweating, constipation, fine tremor, and anxiety.
The endocrine cells of the pancreas are arranged in clusters called what?
Islets of Langerhans
In general, the endocrine pancreas secretes what?
- Two major peptide hormones
- Two minor peptide hormones
What are the two major peptide hormones secreted by the endocrine pancreas?
- Insulin from B-cells
- Glucagon from alpha-cells
Which cells of the endocrine pancreas secretes insulin?
B-cells
Which cells of the endocrine pancreas secretes glucagon?
Alpha- cells
What is the role of insulin secreted from the B-cells of the endocrine pancreas?
- increases glucose movement into cells, -decreases gluconeogenesis,
- decreases glycogenolysis,
- increases fat deposition,
- decreases lipolysis,
- increases protein synthesis (increases storage of fuels through actions on liver, skeletal muscle and adipose),
- increases potassium movement into cells;
- decreases blood glucose, amino acids, fatty acids, keto-acids and potassium
What is the role of glucagon secreted from the alpha-cells of the endocrine pancreas?
- increases glycogenolysis and gluconeogenesis,
- decreases glycogenesis,
- increases lipolyis (mobilizes stored fuels mainly through action on liver and less important effect on adipose);
- increases blood glucose, fatty acids and ketoacids
What are the two minor peptide hormones released by the endocrine pancreas?
-somatostatin (inhibits insulin and glucagon release)
and
-pancreatic polypeptide (functions less well-established)
The central core of the islets of Langerhans contains ______, with _______distributed around the outer rim. The __________(somatostatin) are scattered between _______ (suggesting a paracrine function).
B-cells
Alpha-cells
Gamma-cells
Alpha and B cells
What connects alpha-cells to each other, B-cells to each other, and alpha-cells to B-cells
Gap junctions
What two cell types are found in the Pineal Gland?
- Pinealocytes (modified neurons)
- Neuroglial cells
What can be seen in the pineal gland that is associated with ageing?
Pineal Sand
concentric accretions of calcium and magnesium phosphate
How would one histologicall describe Pinealocytes (cells in Pineal gland)?
large rounded nuclei, prominent nucleoli and branching processes (processes not seen).
Secretory granules in pinealocytes of the pineal gland contain what?
Melatonin and
Serotonin
Melatonin induces__________ in activity of the ___________, __________ and ________ in response to changes in _________.
rhythmic changes hypothalamus adenohypophysis gonads light reaching the retina
Melatonin secretion is inhibited by_____ and increased in _______. The pathway from ______ to pineal is complex involving the spinal cord,__________ nerves and _________nucleus of the__________.
light darkness retina sympathetic suprachiasmatic hypothalamus
How would one histologically describe the neuroglial cells of the pinal gland?
elongated nuclei and are scattered around and between clusters of pinealocytes
