Term
| what is the function of the endocrine system? |
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Definition
Produces hormones released into the bloodstream.
Maintains homeostasis, coordinates growth and development.
Functions with the nervous system in that the hypothalamus of the brain coordinates and regulates most endocrine function. |
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Term
| what are the 3 classes of hormones? describe each |
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Definition
Steroids – cholesterol derived
Synthesized and secreted by the gonads and adrenal cortex
Transported by carrier proteins
Peptides, small proteins, and glycoproteins
Produced by the hypothalamus, pituitary, thyroid, parathyroid, pancreas, scattered enteroendocrine cells in gut and respiratory system as well as some neurons.
Do not require transporter proteins
Amino acid analogues and derivatives
Catecholamines (epinephrine, norepinephrine)
Secreted by some neurons and adrenal medulla |
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Term
| what are the major components of the endocrine system? |
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Definition
Pituitary
Pineal
Thyroid
Parathyroids
Adrenal (suprarenal) gland
Endocrine pancreas |
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Term
| what is the pituitary (hypophysis) and where is it attached? |
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Definition
Small, peas-sized gland located at the base of the brain on the sella turcica just posterior to the optic chiasm.
Attached to the hypothalamus by the infundibulum (pituitary stalk). |
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Term
| what are the 2 functional components of the pituitary? |
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Definition
Anterior lobe – adenohypophysis – derived from Rathke’s pouch, an evagination of developing oral cavity ectoderm
Pars distalis
Pars intermedia
Pars tuberalis
Posterior lobe – neural lobe – derived from developing CNS
Pars nervosa
Infundibulum |
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Term
| what composes rathke's pouch in pituitary development? |
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Definition
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Term
| where is the neuroectoderm derived in pituitary development? |
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Definition
| from the floor of the developing 3rd ventricle |
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Term
| what is the hypothalamohypophyseal portal system? |
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Definition
Modified blood supply allows hypothalamus to regulate adenohypophysis.
Superior arteries supply the pars tuberalis, median eminence and the infundibular stem.
Here there is a primary capillary plexus of fenestrated capillaries.
Primary capillary plexus drains into hypophyseal portal veins.
Portal veins carry blood to a secondary capillary plexus within the pars distalis.
Posterior lobe (pars nervosa) has its own, separate blood supply. |
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Term
| what does the adenohypophysis regulate and produce? |
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Definition
Regulates other endocrine glands and some, non-endocrine tissues.
Produces:
Adrenocorticotropic hormone (ACTH)
Stimulates adrenal cortex
Thyroid stimulating hormone (TSH)
Stimulates thyroid gland
Follicle stimulating hormone (FSH)
Stimulates Sertoli cells of testis and follicular cells of ovary
Leutinizing hormone (LH)
Stimulates Leydig cells of testis and theca interna cells of ovary
Growth hormone (GH)
Stimulates liver and other tissues to produce insulin-like growth factor I (IGF-I)
IGF-I stimulates growth
Prolactin (PRL)
Promotes mammary gland development and milk production |
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Term
| what are the 3 identifiable cell types of the adenohypophysis? |
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Definition
Three cell types identifiable based on staining with H and E.
Acidophils (40%)
Somatotropes
Lactotropes
Basophils (10%)
Gonadotropes
Corticotropes
Chromophobes (50%) |
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Term
| describe how the hypothalamus regulates the adenohypophysis |
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Definition
The hypothalamus has neurons that, via the hypothalamo-hypophyseal portal system, regulate release of anterior pituitary cells.
Hypothalamic regulatory neuropeptides secreted near fenestrated capillaries in the median eminence.
There are hypothalamic releasing and inhibiting polypeptides.
Ex: Hypothalamic dopamine tonically inhibits PRL. |
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Term
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Definition
Excessive secretion of HGH
HGH stimulates IGF-1 (somatomedin C) secretion by the liver, which, in turn, stimulates growth of bone and other tissues
Acromegaly is an adult condition
Hands, feet, jaw and soft tissues enlarge
Long bones cannot grow in length, but can grow by appositional growth.
Gigantism is the childhood condition
Epiphyseal plates not closed and therefore, long bones grow. |
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Term
| the posterior pituitary (neurohypophysis) is derived from? |
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Definition
| Derived from neuroectoderm of the developing diencephalon. |
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Term
| what does the posterior pituitary contain? |
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Definition
Consists of the pars nervosa and infundibulum.
Contains unmyelinated axons and endings of neurosecretory neurons, the cell bodies of which are in the hypothalamic nuclei, supraoptic and paraventricular. |
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Term
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Definition
| Neurosecretory products, oxytocin and vasopressin or antidiuretic hormone (ADH) travel from the hypothalamic nuclei and are stored in the axon terminals that end adjacent to fenestrated capillaries. These stored products are seen with H and E stain and are called Herring bodies. |
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Term
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Definition
| copious amounts of dilute urine |
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Term
| what are the 2 forms of diabetes insipidus? |
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Definition
Central
Could be damage to the hypophyseal stalk
Might result from head trauma that shears the stalk
Nephrogenic
Gene mutation
Defective ADH receptor and AQP-2 |
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Term
| what does the pineal gland secrete? |
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Definition
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Term
| what are the chief cell type of the pineal gland? |
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Definition
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Term
| what is the function of the pineal gland? |
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Definition
| regulates circadian rhythm and reproductive function |
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Term
| describe the pineal gland |
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Definition
Single, midline gland derived from the posterior diencephalon.
Small, flattened pine cone-shaped gland.
Pinealocytes are chief cell type.
Interstitial cells resemble astrocytes.
Characterized by corpora arenacea or brain sand, calcified concretions that are radiopaque.
Secretes melatonin.
Regulates circadian rhythm and reproductive function. |
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Term
| what 3 important hormones does the thyroid gland produce? |
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Definition
| Produces three important hormone thyroxine (tetraiodothyronine,T4), triiodothyronine (T3) and calcitonin. |
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Term
| describe the structure and development of the thyroid gland |
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Definition
Bi-lobed gland lying in the anterior neck below and lateral to the thyroid cartilage. Lobes are attached by an isthmus.
Begin development during the 4th week of gestation from a thickening of endoderm in the floor of the primitive pharynx.
Grows caudally forming a duct-like invagination called the thyroglossal duct.
Thyroid tissue “migrates” downward leaving a remnant in 40% of adults, the pyramidal lobe of the thyroid. |
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Term
| what type of epithelium lines the thyroid gland? |
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Definition
| Lined by simple cuboidal or simple columnar epithelium |
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Term
| C cells in between follicles in the thyroid gland secrete what? |
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Definition
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Term
| what are the structural units of the thyroid gland? |
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Definition
colloid-filled follicles
Colloid composed mostly of the glycoprotein, thyroglobulin.
Thyroglobulin is an inactive, storage form of thyroid hormones. |
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Term
| describe the steps involved in the production of T3 and T4 in the thyroid gland |
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Definition
Thyroglobulin synthesized and released into colloid.
Iodide transported from blood to colloid.
Thyroglobulin iodinated.
Formation of T3 and T4.
Resorption of colloid.
Release of T3 and T4 into bloodstream.
TSH from the pituitary causes follicular cells to become more active and columnar. Low T3 and T4 stimulates release of TRH by hypothalamus, which in turn stimulates release of TSH. |
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Term
| what is the effect of TSH on follicular cells? |
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Definition
causes them to become more active and columnar
Low free T3 and T4 stimulates release of TRH by hypothalamus, which in turn stimulates release of TSH.
High free T3 and T4 inhibits release of TRH by the hypothalamus, which in turn, causes decreased release of TSH by the pituitary. |
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Term
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Definition
| Enlargement of the thyroid gland as a result of hypothyroidism or hyperthyroidism |
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Term
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Definition
Iodine deficiency
Autoimmune disease, Hashimoto’s disease
Antibodies to thyroid peroxidase and thyroglobulin
Tiredness
Sensitivity to cold
Inability to concentrate |
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Term
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Definition
Graves’ disease
Autoimmune disease in which antibodies activate TSH receptors and thereby stimulate thyroglobulin synthesis and T3 and T4 release. |
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Term
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Definition
Hyperthyroidism
Autoimmune disease
Antibodies to TSH receptors stimulate receptors (I.e. act as agonists)
Exopthalmos
Nervousness
Weakness
Weight loss
Heat intolerance |
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Term
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Definition
Characterizes adult onset hypothyroidism
Accumulation of proteoglycans and fluid in the dermis
Puffy face, coarse hair, loss of hair in outer eyebrow |
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Term
| what are the parathyroid glands? |
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Definition
Typically 4 small glands embedded in the posterior thyroid gland.
Chief (principal) cells produce parathyroid hormone or parathormone (PTH).
Oxyphil cells first differentiate around 5-7 years of age.
Function is not known. |
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Term
| what effect does calcitonin have on blood calcium? |
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Definition
Increased blood calcium concentration stimulates calcitonin secretion.
Calcitonin decreases blood calcium concentration.
Effects of calcitonin most important in children and less important in adults |
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Term
| what effect does PTH have on blood calcium? |
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Definition
Decreases calcium excretion by kidneys.
Increases intestinal absorption of calcium.
Indirectly activates osteoclasts to release calcium from bone.
Increases D3 synthesis which stimulates intestinal absorption of calcium. |
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Term
| where are the adrenal glands located? |
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Definition
| Are retroperitoneal organs that rest on the superior poles of the kidneys, hence the other name suprarenal glands |
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Term
| describe the structure of the adrenal glands |
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Definition
Adrenal glands have a cortex and medulla.
Cortex has three distinct zones.
Zona glomerulosa.
Zona fasciculata.
Zona reticulata.
Medulla characterized by neural crest-derived chromaffin cells that secrete catecholamines.
Medulla is like a sympathetic ganglion that releases its products into the blood stream. |
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Term
| what are the 3 zones of the adrenal cortex? |
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Definition
Zona glomerulosa
Secretes mineralocorticoids, predominantly aldosterone.
Controls electrolyte homeostasis.
Zona fasciculata
Secretes glucocorticoids, predominantly cortisol.
Promotes metabolism, resists stress.
Zona reticulata
Secretes gonadacorticoids, most dihydroepiandrosterone
Weak masculization effect.
Normal serum levels have insignificant effects. |
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Term
| what causes cushing's disease? |
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Definition
| Overproduction of ACTH by a basophilic adenoma of the pituitary stimulates oversecretion by adrenal cortex causing Cushing’s disease. |
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Term
| true or false: Most cases of overproduction of ACTH involve ectopic ACTH production by malignancies such as small cell carcinoma of the lung. |
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Definition
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Term
| what is a major cause of cushing syndrome? |
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Definition
| chronic administration of corticosteroids |
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Term
| what are the 3 principal cell types of the endocrine pancreas? |
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Definition
Special stains are required to see the 3 principal cell types.
β (beta) cells – (70%) - insulin secreting
α (alpha) cells – 15-20% - glucagon secreting
δ (delta) cells – 5-10% - somatostatin secreting
Islets of Langerhans scattered throughout pancreas, but are most numerous in the tail.
In H and E stained tissue, islets appear pale staining. |
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Term
| what is diabetes mellitus type I? |
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Definition
Also called insulin-dependent diabetes mellitus (IDDM) or juvenile diabetes.
Widely believed to be an autoimmune destruction of islets.
Circulating antibodies to beta cells.
Patient who die shortly after onset have insulinitis.
Metabolic changes cause widespread multisystem complications. |
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