Flashcards in Endocrine System Deck (75):
What are the primary organs of the endocrine system?
Pituitary gland, hypophysis cerebri
Pineal gland, epiphysis cerebri
What are the secondary endocrine organs?
pacreas, Testes, Ovaries, Kidneys, Stomach, Intestines, Thymus, Heart, Placenta, Adipose Tissue
What are the functions of the endocrine system?
- growth and development
- Internal environment
- Energy production, storage, and utilization
What are the characteristics of the endocrine organs?
- Epithelial origin
- highly vascular
- control or effect mediated by hormones
What is autocrine signalling?
extracellular signal produced by the cell binds to receptors on ITSELF (target sites on same cell)
What is paracrine signalling?
extracellular signal produced by the cell bind to receptors sites on adjacent cells.
What is endocrine signalling?
hormone is secreted into the blood stream by a cell and is then carried via the blood to distant target cells
What can a hormone be? (What are they made of?)
Proteins eg: insulin, glycoproteins, polypeptides
Amino acids eg: T3, T4, catecholamines
Steroids eg: testosterone, estrogen, progesterone
How do hormones travel?
Through the bloodstream to target cells
How do most hormones bind to target cells?
Bind to receptors on the surface of the target cell
How do steroid hormones act on the target cell?
They pass through the plasma membrane of the target cell and bind to the nucleus
What kind of response does a hormone typically give?
Slow sustained responses
What is the hypothalamus?
Portion of the brain that links the nervous system to the endocrine system via the pituitary gland/hypophysis
What do hypothalamic nuclei do?
Control distant cells via hormones through two pathways
- Production of releasing hormones - released into "portal system" to target cells in the adenohypophysis
- hormones axon ally transported and stored in the neurohypophysis, then released in the blood to target distant sites
What is another name for the pituitary gland?
The hypophysis cerebri
What is another name for the posterior pituitary?
What is another name for the anterior pituitary?
What are the developmental origins of the pituitary gland?
Posterior pituitary/Neurohypophysis = neuronectoderm ( from diencephalon)
Anterior pituitary/Adenohypophysis = epithelial (from roof of pharynx)
What are the three portions of the Neurohypophysis?
Pars nervosa (pars posterior)
Infundibular stalk (infundibulum)
Eminentia mediana - small attachment between the hypophysis and infundibulum
What are the three parts of the adenohypophysis?
Pars tube rails
What do the cell bodies of large neurons found in hypothalamus nuclei produce?
Anti diuretic hormone (ADH) and oxytocin
What are herring bodies?
Swellings along the hypothalamic neurons which are the site in which hormones are accumulated.
- storage site for ADH and oxytocin
Where are herring bodies found?
Neurohypophysis (posterior pituitary gland) pars nervosa
What do the axons of the neurohypophysis pars nervosa terminate on?
Which nucleus is associated with ADH?
supraoptic nucleus (SON)
which nucleus is associated with oxytocin?
Paraventricular nucleus (PVN)
What does Antidiuretic hormone do (ADH)
Increases water reabsorption and concentrates urine in the kidneys
What does oxyotcin do?
stimulates contraction of myoepithelial cells for milk let down/release
Which part of the pituitary gland is the glandular part?
What does the adenohypophysis require to work?
a releasing hormone from the hypothalamus
What is the biggest part of the adenohypophysis? What does it do?
the pars distalis -> secretes the majority of hormones
The pars intermedia is a source of what?
melanocyte-stimulating hormone (MSH)
What are the acidophils of the adenohypophysis pars distalis? What do they produce?
- Somatotropes - growth hormone
- Mammotropes - prolactin
What are the basophils of the adenohypophysis pars distalis? What do they produce?
- Thyrotropes - Thyroid stimulating hormone (TSH)
- Gonadotropes (Sigma(?)1 basophils)- Follicle stimulating hormone (FSH)
- Gonadotropes (sigma(?)2 basophils) - Luteinizing hormone (LH)
- Adrenocorticotropes - ACTH
What secretion from the hypothalamus stimulates the release of FSH and LH?
What do neurosecretory cells in the hypothalamus do?
produce releasing hormones into portal vessels
Where do releasing hormones secreted by the neurosecretory cells of the hypothalamus go and what do they do?
they travel to the adenohypophysis (especially pars distalis) where they stimulate acidophils or basophils to produce another hormone
What is the chief target cell of growth hormone? What hormone is then released by this organ?
All cells, Hepatocytes
Hepatocytes release insulinlike growth factor I (IGF-I)
What is the chief target cell of Prolactin?
mammary duct/alveolar epitheliocyte (mammary glands and testes)
What is the chief target cell of Thyroid stimulating hormone? What hormone is then released by this organ?
Thyroid follicular epitheliocyte
Releases: triiodothyronine (T3) and tetraiodothyronine (T4)
What is the chief target cell of FSH? What hormone is then released by this organ?
Ovarian follicular epitheliocyte Testicular seustentacular cell
Release: estrogen, inhibin, activin
(testes and ovaries)
What is the chief target cell of LH? What hormone is then released by this organ?
-corpus luteum epitheliocyte - Releases: progesterone
-ovarian internal thecal cell - Releases testosterone
-testicular interstitial cell - Releases testosterone
(testes and ovaries)
What is the chief target cell of Adrenocorticotropin (ACTH)? What hormone is then released by this organ?
-Zona glomerulosa epitheliocyte - releases mineralocorticoid
-Zona fasciculata epitheliocyte - releases glucocorticoid
-Zona reticulans epitheliocyte - releases androgen
What does the pars intermedia produce? What does it act on?
melanocyte stimulating hormone - acts on melanocytes in the epidermis
What are the nuclei of the adenohypophysis?
dorsal medial, ventral medial and infundibular nuclei
Where do the axons of the adenohypophysis synapse?
on vessels in the primary capillary plexus
What is the main function of the epiphysis?
regulate daily rhythms of bodily activity
What are the secretory cells of the epiphysis? What do they produce?
pinealocytes - produce the hormone melatonin
What do pinealocytes respond to?
respond to stimuli detected in the retina; darkness stimulates secretion of melatonin -> circadian 24 hr rhythm
What is melatonin exclusively involved in signalling?
the time of day and time of year
When is melatonin secreted? (mainly)
What is melatonin?
an effective antioxidant which also has immune-enhancing and oncostatic properties
What is melatonin important in?
- Long day breeders ( horses) when days get longer (late spring/summer/early fall)
- Short day breeders (sheep/goat/deer/etc) when days get shorter (fall)
What is another name for the pineal gland?
What is corpora arenacea?
brain sand -> pigment build up in the brain tissues (pineal gland) (blackish brown)
What do the follicles of the thyroid gland do?
- lining cells produce thyroglobulin
- stored in follicle lumen (colloid)
- Lining cells endocytose thyroglobulin and convert to active T3/T4 (thyroxine)
What does TSH regulate in the thyroid?
synthesis, iodination, proteolysis of thyroglobulin
What are C or clear cells also know as? What do they do?
also known as parafollicular cells.
- Secrete calcitonin in response to high blood calcium
- Main function is to lower serum calcium
- Targets bone and kidney
What does the parathyroid gland do?
secretes parathormone (PTH) into capillaries
What does parathormone (PTH) do?
- increases intestinal and renal Ca reabsorption
- Stimulates osteoclasts -> bone reabsorption
What are the two parts of the adrenal gland?
cortex and medulla (only seen in mammals)
what does the cortex portion of the adrenal gland do, what does it arise from?
secretes corticosteroids and arises from the mesoderm
What does the medulla of the adrenal gland do and what does it arise from?
secretes catecholamines and arises from the neural crest
What are the three parts of the cortex of the adrenal gland and what do they secrete?
-Zona glomerulosa - releases mineralocorticoids (Aldosterone)
-Zona fasciculata - releases glucocorticoids (Cortisol)
-Zona reticulans - releases weak androgen
From the outer adrenal gland to the medulla, what are the layers of the cortex in order?
Zona glomerulosa -> Zona fasciculata -> Zona reticularis
What is the name of special cells in the adrenal medulla? What do they do?
Chromaffin cells - secrete epinephrine and norepinephrine, stored in secretory granules
-These are columnar to cuboidal cells that do not have distinct vacuoles
What does low blood pressure/renin system activate in the adrenal gland? what does it do?
Angiotensin II (ACTH) - increases blood volume
Is ACTH involved in a negative or positive feedback loop?
What are the main cells of the endocrine pancreas?
the islets of langerhan
What are the types of islets of langerhan cells and what do they secrete?
Alpha - glucagon, CCK, GIP
Beta - insulin, IAPP
Delta - somatostatin
Other - gastrin
What are the endocrine tissues of the gastrointestinal tract and what do they secrete?
- pyloric region of stomach - secretes gastrin
- enteroendocrine cells in epithelium mucosae of SI - secretes hormones such as CCK for gall bladder contraction
- Endocrine cells in SI - secrete secretin and gastric inhibitory polypeptide
What two hormones are produced by the kidneys?
renin and erythropoietin
What does renin do? What is it produced by?
produced by juxtaglomerular cells
- part of renin-angiotensin-aldosterone system (RAAS)
- involved in control of blood pressure
What does erythropoietin do? what is it?
- controls erythropoiesis ( RBC formation)
- It is a cytokine for RBC precursors