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MLSCI 250 > LECTURE - The Endocrine System > Flashcards

LECTURE - The Endocrine System Flashcards

1
Q

hormones may be comprised of … (4)

A

proteins, peptide molecules, cholesterol derived steroids, or amino acid derivatives

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2
Q

endocrine cells have three possible anatomical distributions:

A
  • endocrine cells gathered together = specialized endocrine gland organ (eg. thyroid, pituitary, parathyroids, and adrenals)
  • endocrine cells form discrete clusters in another specialized organ (eg. pancreas, ovary, testis)
  • endocrine cells dispersed amongst other cells in epithelial tissues = diffuse neuroendocrine system; occurs particularly in the GI tract and respiratory system; action of hormones occur locally
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3
Q

bean shaped gland situated in the sella turcica at the base of the brainq

A

pituitary gland

- secretion controlled by the hypothalamus

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4
Q

the pituitary gland is anatomically divided into two main parts:

A
  • adenohypophysis (anterior)

- neurohypophysis (posterior)

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5
Q

pituitary portal system

A

superior arteries form the external plexus close to nerve endings of cells located in hypothalamus
=> parallel capillary network which runs down the pituitary stalk to form portal vessels
=> capillaries run forward into the anterior pituitary, providing a direct vascular link between hypothalamus and cells of the anterior pituitary

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6
Q

this is derived from an epithelial outgrowth of the foregut (oral cavity) called Rathke’s pouch

A

anterior pituitary
> cord + clumped; surrounded by a fine capillary network, which brings blood from the hypothalamus (brings either inhibitory or secretory factors that affect secretion of hormones from anterior pit)
> darker than posterior

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7
Q

three components of the adenohypophysis

A
  • pars distalis: forms most of the anterior pituitary
  • pars intermedia: tends t be less defined in humans
  • pars tuberalis: layer or extension of the anterior pit that surrounds the neural stalk of the hypothalamus
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8
Q

where do the secretions from the anterior pituitary cell diffuse into?

A

the vascular network, which eventually drains into the systemic circulation

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9
Q

this part of the anterior pituitary is responsible for the synthesis and secretion of melanocyte-stimulating hormone (MSH)

A

pars intermedia

- generally considered rudimentary in humans

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10
Q

five cell types found in the anterior pituitary and what they secrete:

A
  • somatotrophs - growth hormone; 50%
  • mammotrophs - prolactin; 25%
  • corticotrophs - corticotrophin - ACTH (adrenocorticotropic hormone); 15-20%
  • gonadotrophs - FSH + LH; 5-10%
  • thyrotrophs - thyrotrophin - TSH); 5%
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11
Q

posterior pituitary

A
  • continuation of hypothalamus
  • comprised of axons of neuronal cells (lies in the supraoptic and paraventricular nuclei of hypothalamus) + supporting glial cells = pituicytes
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12
Q

oxytocin

A

secreted from the paraventricular nucleus in hypothalamus

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13
Q

vasopressin

A
  • ADH

- secreted from supraoptic nucleus in hypothalamus

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14
Q

Herring bodies

A

oxytocin and vasopressin travel to posterior pituitary in neurosecretory granules via axons
- hormones stored in terminal ends of axons which appear as bulb like projections called herring bodies

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15
Q

neurosecretion and Herring bodies

A

when hormones need to be released, hypothalamus sends nervous impulses through axons = neurosecretion

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16
Q

where is the thyroid located?

A
  • anterior neck, just in front of the trachea

- H-shaped, lobulated

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17
Q

T or F. The thyroid is encapsulated

A

T.

septae = lobules; blood vessels, nerves, and lymphatic channels; within gland = capillaries also surround follicles

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18
Q

how did the thyroid gland develop?

A
  • in part as a downgrowth from fetal tongue (follicular epithelium)
  • and in part from the fourth branchial pouch = calcitonin cells
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19
Q

function of the thyroid

A
  • T4 (thyroxine): influence basal metabolic rate
  • T3 (triiodothyronine): influence growth + development; regulated by TSH/thyrotrophin from anterior pituitary
  • calcitonin: decreases calcium levels by inhibiting bone resorption; PTH antagonist; levels dependent on blood Ca
20
Q

structure of thyroid

A
  • capsule = thin, collagenous with internal septae, forms irregular lobules
  • stroma = composed of connective tissue, blood vessels, and nerves
21
Q

functional unit of thyroid gland

A

thyroid follicles

  • tightly packed
  • irregular
  • single layer of cells resting on basement membrane
  • simple cuboidal epithelium
22
Q

the thyroid __________ cells synthesize and secrete hormones. how is this achieved?

A

follicular cells

  • achieved by concentrating iodide from bloodstream, converting it to idine then secreting it into the follicular lumen
  • production of T3 and T4 = controlled by TRH and TSH
  • iodine combines w tyrosine residues in thyroglobulin (colloid) to form T3/T4 in their inactive form
  • thyroglobulin synthesized in Rough ER
23
Q

where are inactive T3 and T4 hormones stored?

A

follicular colloid

  • homogeneous proteinaceous material
  • colloid is engulfed and hydrolyzed by follicular cells
  • hormones can diffuse in bloodstream in their active forms
24
Q

this is found among follicular cells or interfollicular spaces and these secrete calcitonin when Ca levels are increased

A 
parafollicular cells (C or clear cells)
- pale and hard to see in routine light microscopy; use IHC Abs or EM
25
Q

grossly, can appear as coffee coloured lands that are small and ovoid in shape

A

parathyroid glands

26
Q

how did the PTH glands develop and where are they located

A
  • developed from the third and fourth branchial pouches (surrounded by a thin, fibrous capsule; septae)
  • located in the neck where thyroid is; posterior
27
Q

the septae of the PTH gland carries…

A

lymphatics, nerves, and blood vessels

28
Q

three cell types of PTH glands

A
  • chief (principal) cells: PTH; increases Ca levels in blood by promoting bone resorption via osteoclasts; cells are spherical in shape with pale pink to clear cytoplasm + small dark nuclei
  • oxyphil: rare before puberty; increase in # as we age; larger than chief cells; eosinophilic cytoplasm + small, dark nuclei; cytoplasm may be granular due to large #s of mitochondria
  • adipocytes: appear at time of puberty and continue to increase till midlife = remain constant; help to form stroma (found in oxyphil and chief cells)

chief and oxyphil = cord and clump formations

29
Q

two triangular shaped glands located in upper poles of kidneys

A

adrenal glands

30
Q

two distinct endocrine systems found in the adrenal gland

A
  • adrenal cortex (outer) = synthesizes + secrete hormones produced from cholesterol, controlled by the pituitary gland, the hypothalamus, as well as the RAAS
  • adrenal medulla (inner) = vasoactive amines, adrenaline, noradrenaline, controlled by sympathetic nervous system
31
Q

RAAS

A

renin angiotensin aldosterone system

32
Q

layers of the adrenal cortex

A

fourth outermost layer involutes after birth

  • Zona glomerulosa: mineralocorticoids (aldosterone)
  • Zona fasciculata: thickest layer; glucocorticoids (cortisol)
  • Zona reticularis: androgenic steroids (DHEA + DHEA-S) and some glucocorticoids
33
Q

DHEA, DHEA-S

A
  • dehydroepiandosterone

- dehydroepiandrosterone-sulfate

34
Q

hyperadrenalism

A

excess secretion of glucocorticoids = Cushing’s syndrome +

excess secretion of mineralocorticoids = Conn’s syndrome

35
Q

hypoadrenalism

A

hormones of adrenal cortex are not secreted (due to cellular destruction for example = Addison’s disease

36
Q

MATCH: (layers of adrenal cortex)

a) thin layer; cells with eosinophilic cytoplasm (stains darkly); cells may contain lipofuscin pigment
b) thin subcapsular layer; small compact cells w scant lipids arranged in clumps and separated by stroma which is composed of largely thin-walled capillaries in trabeculae
c) occupies most of adrenal cortex; large reticular cells with clear cytoplasm; lots of smooth ER and mitochondria; intracytoplasmic accumulation of lipid droplets (lighter staining cells)

A

a) zona reticularis
b) zona glomerulosa
c) zona fasciculata

37
Q

adrenal medulla

A
  • the center of the gland
  • control via sympathetic nervous system
  • polyhedral cells are large with pale staining nuclei and finely granular, somewhat basophilic cytoplasm
  • cells arranged in clumps + columns with a prominent capillary network
  • cells contain neurosecretory granules where catecholamines (epi/norepi) are stored
38
Q

intense brown colour of adrenal medulla when exposed to strong oxidizing agents (like potassium dichromate)

A

due to high catecholamine content in cells

39
Q

chromaffin cells

A

type of cell that makes neurohormones (chemicals that are made by nerve cells and used to send signals to other cells) and releases them into the blood. Chromaffin cells make epinephrine (adrenaline) and norepinephrine (noradrenaline). They are found in the adrenal glands or in groups of nerve cells called ganglia.

40
Q

major endocrine component of the pancreas

A

Islets of Langerhans
> more numerous in tail
> paler staining
> capillary networks are in close contact ith cells of the islets

41
Q

enterochromaffin cells

A

in pancreas

  • motilin
  • ghrelin
  • serotonin
42
Q

VIP

A

vasoactive inhibitory peptide

43
Q

four main cells in endocrine pancreas

A
  • B = insulin; 70%; lowers blood glucose
  • A = glucagon; 20%; increases blood glucose
  • D = somatostatin; 5-10%; inhibit GI secretions
  • PP = pancreatic polypeptide; 1-2%; increases motility in GI
44
Q

these cells occur throughout the islet and have a well-developed rER, a prominent Golgi and numerous neurosecretory granules

A

insulin secreting cells

45
Q

these cells are located mainly at the periphery of islet

A

glucagon secreting cells

46
Q

disorder wherein cells normally responsive to insulin show resistance to insulin’s effects

A

type II DM

  • B cells of islets are still able to produce insulin
  • treatment = lifestyle modifications such as diet + exercise as well as drug treatment regimens

MLSCI 250 (35 decks)

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