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S3 B2 Histology > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

How are signals carried through the endocrine system?

A

hormones that travel through the blood, lymph and connective tissue

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2
Q

What are the 2 types of feedback systems utilized by the endocrine syste?

Describe each of them.

A
  • Negative feedback
    • response diminishes original stimulus
  • Positive feedback
    • response enhances original stimulus
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3
Q

Where is the pituitary gland located?

A

base of the brain within a depressin in the skull called sella turcica

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4
Q

What structure connects the pituitary to the hypothalamus?

A

infundibular stalk

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5
Q

What are the 3 major goals of the endocrine system?

A
  1. production of hormones
  2. communication between body systems
  3. coordination of growht and development
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6
Q

What is the major difference between endocrine and exocrine glands?

A

endocrine glands have no ducts!

they are discrete glands

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7
Q

The capsule surrounding the pituitary is composed of what material?

A

dense irregular connective tissue

continuation of the dura mater of the brain

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8
Q

What are the two functional components of the pituitary & where are their embryologic origin?

They are composed of what types of tissue respectively?

A
  • adenohypophysis
    • anterior lobe
    • oral ectoderm (Rathke’s pouch)
    • glandular epithelial tissue
  • neurohyophysis
    • posterior lobe
    • downgrowth of neurectoderm of diencephalon
    • neural secretory tissue
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9
Q

Describe the organization of cells found in the adenohypophysis

A

organized into clumps & cords around fenestrated capillaries

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10
Q

What are the 3 components of the adenohypophysis?

Describe the defining features of each part.

A
  • Pars distalis
    • bulk of anterior lobe
  • Pars intermedia
    • thin remnant of wall of Rathke’s pouch
    • remnant of the lumen = Rathke’s cysts
  • Pars tuberalis
    • collar or sheath around infundibular stalk
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11
Q

Rathke’s cysts are lined with what type of epithelium?

A

cuboidal

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12
Q

What are the 4 distinct types of cells located in the adenohypophysis?

Identify how each received their respective names.

A
  1. Chromophiles
    • secretory granules that pick up dye
  2. Chromophobes
    • do not have intensely staining secretory granules
  3. Basophils
    • granules stain with basic dyes
  4. Acidophils
    • granules stain with acidic dyes
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13
Q

Acidophils in the anterior pituitary represent what tyo cell types?

What products do they secrete?

A
  • Somatotropes
    • secrete somatotropin
  • Lactoropes
    • secrete prolactin
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14
Q

How is the release of somatotropin controlled?

A

Under the control of the hypothalamus via release of growth hormone releaseing hormone (GHRH) and somatostatin

GHRH stimulates production & release

somatostatin inhibits the release

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15
Q

What cell type is the most abundant endocrine cell in the adenohypophysis?

A

somatotropes

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16
Q

How is the release of prolactin controlled?

A

tonically inhibited by dopamine produced in the hypothalamus

Thyrotropin releaseing horomone (TRH) stimulate synthesis of prolactin

Dopamine antagonists (antipsychotics) & estrogens (birth control) stimulate prolactin secretion

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17
Q

What happens to lactotropes during pregnancy & lactation?

How can you tell if a person has given birth 2 or more times?

A

increase in size & number

larger size of pituitary in multiparous (given birth 2 or more tiems) individuals

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18
Q

Basophils in the anterior pituitary are represented by what 3 cell types?

A
  1. Corticotropes
    • produce adrenocorticotropic hormone (ACTH)
  2. Gonadotropes
    • secrete follicle-stimulating hormone (FSH)
    • secrete Luteinizing hormone (LH)
  3. Thyrotropes
    • produce thyrotropic hormone (TSH)
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19
Q

How is release of ACTH controlled & what is its bodily function?

A

controlled by corticotropin-releasing hormone (CRH) produced in the hypothalamus

acts on the adrenal cortex

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20
Q

How is release of FSH and LH controlled & what are their bodily functions?

A

controlled by gonadotropin-releasing hormone (GnRH) produced in the hypothalamus

two main hormones that act on the reproductive system

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21
Q

How is release of TSH controlled & what is its bodily function?

A

controlled by TRH, produced in they hypothalamus

acts on the thyroid gland

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22
Q

What part of the pituitary is connected to the hypothalamus?

It attaches to what part of the hypothalamus?

A

neurohypophysis

median eminence of the hypothalamus

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23
Q

What are the two parts of the neurohypophysis?

A
  1. Pars nervosa
  2. Infundibulum
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24
Q

What cell types are located in the posterior lobe of the pituitary?

They secrete what substances?

A

pituicytes: axons of hypothalamic neurons & glial cells - terminals located in pars nervosa

hypothalmic neurons secrete oxytocin and antidiuretic hormone (ADH) into neurohypophysis

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25
Q

What is the name of the large axon terminals found in the pars nervosa that stain pink with eosin?

A

Herring bodies

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26
Q

What is the function of oxytocin?

A

causes uterine contractions & ejection of milk

affects smooth muscle and myepithelial cells

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27
Q

What is the function of ADH?

A

acts on the renal tubules and collecting ducts causing reabsorption of water

constricts arterioles increasing peripheral vascular resistance

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28
Q

The blood supply to the pituitary comes from what sources?

A

superior and inferior hypophyseal arteries

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29
Q

The superior hypophyseal arter supplies what specific structures?

A

pars tuberalis

infundibulum

meidan eminence

pars distalis

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30
Q

The inferior hypophyseal artery supplies what structure?

A

pars nervosa

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31
Q

Describe how the superior hypophyseal artery is responsible for systemic hormone circulation.

A
  • Superior hypophyseal artery forms the primary capillary plexus upon arrival at the pituitary
    • running through the infundibulum & median eminence it pickus up horomones produced in the hypothalamus
  • the blood is collected into hypophyseal portal veins & taken to pars distalis
    • it forms the secondary capillary plexus
    • delivering hormones produced in the hypothalamus to the pars distalis
    • hormones produced by the pars distalis enter the bloodstream
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32
Q

The secondary capillary plexus is composed of what type of capillaries?

A

fenestrated sinusoidal capillaries

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33
Q

Where is the pineal gland located?

A

posterior end of the third ventricle of the brain

covered by the cerebral hemisphere

34
Q

What is the major function of the pineal gland?

How is this function different from that in lower vertebrates?

A

coordinating daily and seasonal cycles with the environmental light-dark cycle

in lower vertebrates, it is light-sensitive & acts as a “third eye”

35
Q

The pineal gland is derived from what embryological structure?

A

outgrowth from the diencephalon

36
Q

The capsule of the pineal gland is composed of what type of material?

The capsule forms what additioanl structures?

A

pia mater

connective tissue septa extend into the gland from this capsule; blood vessels run with the septa

37
Q

What are corpora arenacea?

They are related to what variables?

A

“brain sand”

aggregates of calcium phosphate found in the pinela gland

size & number increase with age

38
Q

What two types of cells exist in the pineal gland?

What do they look like?

A
  1. pinealocytes (principal cells)
    • modified neuronal cells
    • occur in poorly-defined clumps
    • large euchromatic nuclei with prominent nucleolus
    • microtubule-containing processes extend from cell body
  2. glial cells (interstitial cells)
    • ​​nuclei are smaller and more heterochromatic
39
Q

What structures exist between the clumps of pinealocyttes?

A

axons

pinealocyte cell processes

blood vessels

corpora arenacea

40
Q

Pinealocytes secrete what substance?

What is the function of this substance?

Its release is controlled by what substance?

A

melatonin

circadian rhythm to synthesis/secretion

very little secreted during day & secretion peaks in the middle of the night

controlled by norepinephrine

41
Q

How does information about ligh & dark reach the pineal gland?

A

through the retinothalmic tract

connects the suprachiasmic nucleus wiht the sympathetic neural tract

42
Q

Where are the adrenal glands located?

Surrounded by what substances?

A

superior pole of the kidneys

embedded in adipose tissue & covered with connective tissue capsule

43
Q

What are the two sections of the adrenal parenchyma?

How do they appear on a fresh sample?

Embryological origins?

A
  • external cortex
    • yellow peripheral layer
    • mesenchyme (mesoderm)
  • internal medulla
    • central reddish-brown layer
    • neural crest (ectoderm)
44
Q

How are cells organized within the adrenal gland?

A

cords of secretory cells arranged along fenestrated capillaries

45
Q

The capsule of the adrenal glands is formed from what substance?

It continues to form what structues?

A

dense connective tissue

sends thin traveculae into the parenchyma of the gland

46
Q

What hormones are produced in the cortex of the adrenal gland?

What is their secretion pathway?

A

Steroids

  • mineralocorticoids
  • glucocorticoids
  • androgens

Not stored in cytoplasm - secreted immediately (constitutive pathways)

47
Q

Describe the features of cells found in the cortex of the adrenal glands.

A
  • lipid droplets
  • mitochondria with tubular cristae
  • abundant smooth endoplasmic reticulum
48
Q

The adrenal cortex makes up what percent of the overall adrenal glands?

What are the three zones of the adrenal cortex?

They compose about what percent of the cortex, respectively?

A

Adrenal cortex: (90%)

zona glomerulosa (15%)

zona fasiculata (65%)

zona reticularis (7%)

49
Q

Describe the cellular composition of the zona glomerulosa.

A
  • closely packed cuboidal or pyramidal cells
    • arranged into arched cords / curved columns
    • surrounded by fenestrated sinusoidal capillaries
50
Q

The cells of the zona glomerulosa secret what substances?

What is the funtion of these substances?

A
  • mineralocorticoids - regulate sodium & potassium homeostasis and water balance
    • Aldosterone - acts on kidney tubule, gastric mucosa, salivary glands and sweat glands and causes reabsorption of sodium
51
Q

How isthe secretion of aldosterone regulated?

A

Renin-angiotensin-aldosterone system

Juxtaglomerular apparatus of kidney releases renin in response to low blood pressure

renin catalyzes the conversion of circulating angiotensinogen into angiotensin I

Angiotensin I is converted to Angiotensin II by the ACE

Angiotensin II stimulates cells of the zona glomerulosa to produce aldosterone

52
Q

Describe the cellular composition of the zona fasciculata.

A

one or two cell-thick straigght cords that run at a right angle to hte capsule & have fenestrated capillaries between them

  • large secretory cells: spongiocytes
    • look spongy b/c numerous lipid droplets in cytoplasm
53
Q

Secretory cells of the zona fasciculata produce what substances?

What are the functions of these substances?

A

Glucocorticoids (cortisol & androgen)

  1. increasing metabolism of glucose & fatty acids
  2. depressing the immune & inflammatory response by suppressing production of interleukin-1 (IL-1) and IL-2 by lymphocytes and macrophages, and suppressing lymphoblast mitosis within lymph nodes
54
Q

How is the secretion of glucocorticoids by the zona fasciculata regulated?

A

ACTH produced by anterior pituitary stimulat secretion & production glucocorticoids

55
Q

How does ACTH effect the adrenal glands?

A
  • overall cell growth & increase in blood flow
  • stimulate secretion and production of glucocorticoids by spongiocytes in the zona fasciculata
  • stimulates growth and synthetic activtity of the zona reticularis
56
Q

Describe the cellular composition of the ona reticularis

A
  • relatively small cells arranged into irregular cords taht anastomose to form a network (“reticulum”)
    • contain numerous lipofuscin granules
    • fewere lipid droplets & stain more intensely with eosin
57
Q

What substances are secreted by the zona reticularis?

It is regulated by what hormone?

A

androgens (more than zona fasciculata) & glucocorticoids

regulated by ACTH

58
Q

Describe the cellular composition of the adrenal medulla.

What cells are the prinicpal secretory cells?

A
  • polyhedral cells arranged into clumps or cords
    • supported by network reticular fibers
    • network fenestrated capillaries (from medullary arterioles)
  • Chromaffin cells: principal secreting cell
  • Ganglion cells: modulate the activity of chromaffin cells & innervate blood vessels within the medulla
59
Q

Cromaffin cells are derived from what embryologicla function?

A

neural crest cells

they are modified postsynaptic neurons that lack axons

60
Q

What is the major difference between the chromaffin cells & the cells of the adrenal cortex?

How can you differentiate between to two types of chromaffin cells?

A

chromaffin cells accumulate and store hormones in their secretory granules

  • secrete epinephrine:
    • smaller secretory grandules
    • more abundant (80%)
  • secrete norepinephrine
    • larger secretory granules
61
Q

What trigger causes the chromaffin cells to degranulate?

A
  • Chromaffin cells are innervated by preganglionic sympathetic nerve fibers
    • release of acetylchoine causes degranulation
  • Emotional reactions (ie. fright) can trigger sudden release of catecholamines by chromaffin cells
    • alarm reaction (fight or flight)
  • During normal activity, medulla constantly release _small quantitie_s of this hormone
62
Q

How do chromaffin cells secrete their products?

What is the biological response of this secretion?

A

Epinephrine/norepinephrine delivered into bloodstream thorugh fenestrated capillaries

  • Response
    • vasoconstriction, hypertension, increased heart rate, metabolic effects (ie. elevated blood glucose)
63
Q

Describe the progression of blood supply to the adrenal glands

A
  • Suprarenal arteries
    • Capsular arteries (irrigate capsule)
    • Cortical arteries (branch within cortex)
      • fenestrated cortical sinusoidal capillaries
        • ​drain into adrenomedullary collecting veins
    • medullary arteries (through cortex)
      • fenestrated medullary sinusoidal capillaries
    • adrenomedullary collecting veins (receive blood from smaller blood vessels within the medulla)
      • drain into central adrenomedullary vein
    • central adrenomedullary vein
      • drain into inferior vena cava on right
      • dran into left renal vein on the left
64
Q

Where is the thyroid gland located?

Describe its gross structure.

A

anterior neck adjacent to larynx and trachea

two large lateral lobes connected by a narrow isthmus

surrounded by a thin connective tissue capsule

65
Q

What is the main structural unit of the thyroid gland?

A

thyroid follicle

66
Q
A
67
Q

Describe the structure of a thyroid follicle.

A

spherical structure formed by a layer of simple cuboidal follicular epithelium

the apical surfaces are in contact with a cyst-like central cavity filled with a gel-like substance called the colloid

the basal surfaces rest on a basal lamina, which is surrounded by dense network of fenestrated capillaries

68
Q

Follicular epithelium contains what two types of cells?

A
  • follicular cells (principal cell type)
  • parafollicular cells
69
Q

What is the embryological origin of the follicular cells?

What shape are the follicular cells?

They secrete what substances?

A
  • endodermal origin
  • between squamous and low columnar – most cuboidal
    • taller = more active
  • Synthesize
    1. thyroxine (T4)
    2. thriiodothyronine (T3)
70
Q

Describe the steps involved with synthesis of thyroid hormones.

A
  1. Thyroglobulin is synthesized in RER & Golgi of follicular cells
    • secreted into lumen of the follicle
  2. Iodide transport and oxidation
    • follicular cells actively transport iodide from blood into their cytoplasm
    • iodide is oxidized to iodine on the apical membrane & immediately released into the colloid
  3. Iodination of thyroglobulin leads to the formation of T3 or T4
    • T3 and T4 stay linked to a thyroglobulin molecule & are stored in the lumen of the follicle
  4. In response to TSH, follicular cells reabsorb the colloid & uptake the thyroglobulin
    • thyroglobulin is broken down by lysosomes
    • T3 and T4 are released, cross the plasma membrane & diffuse into the blood
71
Q

What is the overal function of T3 and T4?

A

regulate metabolism and heat production

influence body growth and development

72
Q

What is the main function of parafollicular cells?

A

synthesis of calcitonin

73
Q

What is the function of calcitonin?

How is it regulated

A

lowers blood calcium levels

supressing resorptive activity of osteoclasts & promoting calcium deposition in bones by osteoblasts

Regulated by blood calcium levels

74
Q

Where are the parathyroid glands located?

What surrounds them?

A

small endocrine glands embedded within the thyroid

2 pairs - superior & inferior

surrounded by a thin connective tissue capsule

75
Q

What shape are the parathyroid glands as well as the cells within them?

A

ovoid

cells within it are arranged into cords that follow the fenestated capillaries

76
Q

Cells of the parathyroid are derived from what embryological origin?

A

endoderm

77
Q

The parenchyma of the parathyroid gland contains what 2 types of cells?

which is most numerous?

A
  • parathyroid chief cell (most numerous)
  • oxyphil cell
78
Q

Parathyroid chief cells secrete what substance?

A

parathormone (PRH)

79
Q

What is the function of PTH?

It is regulated by what variable?

A

PTH is the antagonist of calcitonin - it increases blood levels of calcium

bone reorption by osteoclasts, decreased kidney excretion of calcium, increased intestinal absorption of calcium

Regulated by blood calcium levels

80
Q

What is the most distinctive feature of oxyphil cells?

A

presence of large number of mitochondria in teh cytoplasm

stain intensly with acidic dyes

S3 B2 Histology (2 decks)

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