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Histology of Endocrine Organs Flashcards

1
Q

What is the endocrine system represented by?

A

a group of single cells and glands that produce and secrete hormones into the bloodstream to modulate many function of the body

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2
Q

Which glands are regulated by the hypothalamus and the pituitary?

A

Thyroid gland and adrenal glands

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3
Q

What do the parathyroid flands and pancreatic islet of Langerhans respond to?

A

variations in the blood levels of calcium or glucose

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4
Q

There is a massive population of single endocrine cells distributed in several tissues of the body that act independently in response to what?

A

local physiological conditions

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5
Q

How do endocrine hormones function?

A

through cell signaling pathways and changes in gene expression

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6
Q

which hormones and vitamin are lipophilic and therefore readily enter the target cell where they bind to cytoplasmic receptors that are transported to proteins that regulate biochemical and physicological processes?

A

Steriod hormones, thyroid hormone, and vitamin D

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7
Q

What initiates a cascade of second messenger events that can directly act on existing enzymes and proteins or or may activate or induce transcription factors that affect gene expression and ultimately regulate cellular function?

A

peptides and catecholines bind to membrane receptors

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8
Q

What gland is part of the neuroendocrine system that combines functions of the nervous system and the endocrine system aimed at the regulation of several physiological processes?

A

The pituitary gland

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9
Q

What is a key component of the neuroendocrine system , a site where neurons acting as neurosecretory cells, release their neuropeptides into blood vessels to reach the adjacent adjacent hypophysis so they can collectively communicate with their target organs and tissues and receive info through feedback loops?

A

The Hypothalamus

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10
Q

What is considered the “Master” endocrine gland, and consists of two embryologically distinct tissues?

A

The pituitary gland

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11
Q

What are the two distinct tissues of the pituitary gland?

A

1)Anterior pituitary (adenohypophysis) is the glandular portion 2)posterior pituitary ( neurohypophysis)- the neural portion

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12
Q

Where is the Anterior pituitary derived from?

A

an outpouching of the roof of the mouth (Rathke’s pouch)

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13
Q

Where is the Posterior pituitary derived from?

A

an outpouching of the floor of the embryonic brain

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14
Q

What is the posterior pituitary continuous with and via what?

A

continuous with the hypothalamus, via the infundibulum

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15
Q

Neurons in the hypothalamus control the activity of what gland?

A

Pituitary gland

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16
Q

What do the neurons of the supraoptic and paraventricular nuclei of the hypothalamus produce?

A

antidiuretic hormone ( ADH) and Oxytocin

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17
Q

Where are ADH and Oxytocin stored?

A

at the ends of their neurons in the posterior pituitary ( are released directly into blood stream upon appropriate stimulation)

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18
Q

Which neurons produce hormones ( releasing and inhibitory) that control function of the cells of the anterior pituitary gland?

A

Neurons of the dorsal medial, ventral medial and infundibular nuclei of the hypothalamus

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19
Q

Where are the hormones from the dorsal medial, ventral medial and infundibular nuclei of hypothalamus released to?

A

into the hypophyseal portal system and transported to the anterior pituitary.

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20
Q

What are the three types of cells in the anterior pituitary?

A

acidophils, basophils and chromophobes

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21
Q

What color do H&E differentially stain the three types of cells in anterior pituitary?

A

acidophils - (pinkish-red), basophils (bluish purple) and do not stain the chromophobes which may be a transition cell and DO NOT PRODUCE HORMONES.

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22
Q

How can subtypes of acidophils and basophils( in the pituitary) be identified?

A

special stains

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23
Q

What does the posterior pituitary consist of?

A

the terminal ends of hypothalamic axons from the supraoptic and paraventricular nuclei and support cell called s PITUICYTE

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24
Q

What does oxytocin act on?

A

smooth muscle cells of the uterus to cause uterine contraction and on myoepithelial cell of the breast to cause lactation

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25
Q

What does ADH act on?

A

cells of the kidney collecting tubules to increase the permeability of the structures to water which decreased urine production. Also caused constriction of arterioles to increased blood pressure.

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26
Q

What is an example of the anterior lobe of pituitary responding to releasing and inhibitory hormones produced by the hypothalamus?

A

production of growth hormone-releasing hormone( GHRH) by the hypothalamus that stimulate the release of growth hormone by the somatotrophs of the ant pituitary.

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27
Q

Where is Somatostatin produced and what does it do?

A

produced by hypothalamus, inhibits the release of growth hormone.

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28
Q

What maintains homeostasis?

A

The secretion of hormones must be turned on and off as needed

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29
Q

what changes the secretion rate?

A

Hormones induce a physiological response and some component of this “feeds back” directly or indirectly on the gland that secreted the hormone

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30
Q

What else may also feed back to inhibit further hormone release?

A

Hormones produced by the pituitary or peripheral endocrine organs

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31
Q

which feedback is more important and more common?

A

Negative

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32
Q

How many lobes does the thyroid have and where is it located, and what does it look like?

A

bilobed, is bilaterally symmetrical, firm, smooth gland, in anterior neck

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33
Q

what connects the two lobes of the thyroid?

A

isthmus

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34
Q

what does the thyroid gland arise as?

A

as a midline outpouching of the floor of the pharynx

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35
Q

how many follicles does the thyroid gland have?

A

several million

36
Q

what does a single follicle of the thyroid have in it?

A

a ball of cells with a central lumen filled with amorphous, esoinophillic colloid composed of idothyroglobulin

37
Q

What is idodothyroglobulin?

A

the non-active form of thyroid hormone

38
Q

What type of cells line the follice of the thyroid?

A

single layer of cuboidal cells resting on a basement membrane and are referred to a FOLLICULAR CELLS

39
Q

What does the thyroid epithelium do?

A

concentrates iodide from the blood and synthesizes the hormones T3 and T4.

40
Q

which are the cells in the thyroid that are responsible for calcitonin secretion and where are they located?

A

The parafollicular cells (C cells) located in the interstitium around the follicles

41
Q

What are the two phases of synthesis and secretion of thyroid hormones?

A

exocrine and endocrine phases

42
Q

What happens in the Thyroglobulin Sythesis(exocrine phase)?

A

TSH receptors on the follicle cell binds TSH, (1)
iodide taken up from blood via ATP-dependent pump in basal cell membrane (2) iodide diffuses through cell into lumen of follicle (3)in response to TSH stimulation the follicular cell synthesizes thyroglobulin homodimer and thyroid peroxidase that are secreted by exocytosis into the lumen of the follicle (4) iodide is oxidized by the thyroperoxidase to iodine at the apical surface of the cell and released into the follicular lumen (5) iodine is transferred to the tyrosine residues of the thyroglobulin and iodothyroglobulin is stored as the colloid (6)

43
Q

Thyroid Hormone synthesis and Release ( endocrine phase)

A

TSH receptor on the follicle cells binds TSH (1) A droplet of colloid is taken up into the follicular cell by endocytosis (2) The droplet of colloid fuses with a lysosome and the iodothyroglobulin is enzymatically degraded to T3(triiodothyroxine) and T4(thyroxine) (3) Both T3 and T4 are release into blood stream with a ratio of T3 to T4 of 1-20 and bind to serum proteins for transport (4)

44
Q

Which is more active? T3 or T4?

A

T3 more active

45
Q

What is the half life of T3 and T4?

A

T3 half life 18 hours, T4 half life is 5-7 days and may be converted to T3 in target tissues.

46
Q

What do both T3 and T4 do?

A

increased the basal metabolic rate in the adult and influence growth and neurological development in the fetus

47
Q

What does the parafollicular cell of the thyroid gland do in response to high levels of plasma calcium?

A

they secrete calcitonin

48
Q

what does calcitonin do?

A

has effects on osteoclasts of bone to decreased bone turnover as well as effects on the kidney and gut that lead to increased excretion of calcium in the urine and feces

49
Q

What does the parathyroid gland consist of?

A

two pair of glands surrounded by a thin connective tissue capsule that divides the gland into course clumps of cells.

50
Q

what does the stroma of the parathyroid contain?

A

abundant vasculature, nerves, lymphatics and fat

51
Q

what to the parathyroid gland secrete? and what are they essential for?

A

parathyroid hormone (PTH) and are essential for physiologic maintenance of circulating calcium concentrations

52
Q

what two types of cells are present in parenchyma of parathyroid glands?

A

1) chief( principal) cells and 2) oxyphil cells

53
Q

what are chief cells responsible for?

A

form the bulk of the parathyroid and responsible for synthesis and release of PTH ( parathyroid hormone)

54
Q

what do oxyphil cells do?

A

function is uncertain, they stain lighter than Chief cells

55
Q

What stimulates PTH secretion and increases the number of oteoclasts present in bone that results in increased bone turnover and calcium release?

A

decreased serum circulating calcium

56
Q

What effects does PTH have on the gut and kidney with decreased circulating calcium?

A

leads to increased absorption and retention of calcium

57
Q

What are the two cortexes of adrenal gland?

A

inner -medulla, outer - cortex

58
Q

what do the cells in medulla and cortex do?

A

maintenance of homeostasis through the regulation of the body’s adaptive response to stress, regulation of body water, sodium and potassium and control of blood pressure.

59
Q

what type of cells is the medulla composed of and what do they do?

A

chromaffin cells that synthesize and secrete catecholamines (epinephrine and norepinephrine)

60
Q

what is the major secretory product of the medulla and what does it do?

A

epinephrine- increases heart rate and constricts blood vessels ( increase blood pressure).

61
Q

what does norepinephrine do?

A

dilates blood vessels and increases glucose release?

62
Q

what are the three layer of the adrenal cortex?

A

zona glomerulosa, zona fasciculata, and zona reticularis

63
Q

where is the glomerulosa layer found, and what does the zone glomerulosa ( of the adrenal gland)look like?

A

outermost layer in the cortex, layer of cells has a foamy appearance due to presence of abundant numbers of lipid droplets in cytoplasm.

64
Q

what is the zone glomerulosa responsible for?

A

producing the MINERALCORTICOID ALDOSTERONE

65
Q

What is aldosterone involved in?

A

reabsorption of sodium and water by salivary glands, sweat glands and the kidney leading to increased blood volume and therefore blood pressure.

66
Q

what is the stimulus for secretion of the zone glomerulosa

A

increased potassium, increased angiotension II levels and decreased plasma volume

67
Q

what does zona fasciculata in the adrenal gland look like and where is it found?

A

cells arranged in long, straight colums, lightly staining cells due to the abundant amt of lipid within the cells.

68
Q

what does the zona fasiculata do?

A

secrete glucocorticoids following ACTH stimulation, 95 percent which is Cortisol

69
Q

what causes increased ACTH production

A

low concentrations of cortisol

70
Q

what do glucocorticoids fron the zona fasiculata do?

A

enhance glucose synthesis by the liver to elevate blood sugar levels, supresses the inflammatory and immune response and causes catabolism ( break down) of proteins, which may lead to muscle wasting.

71
Q

where is the zona reticularis and what does it do?

A

innermost layer within the adrenal cortex, secretes androgens, a less potent form of testosterone, progesterone and estrogen following ACTH stimulation

72
Q

What are the three types of hormones? Give an example of each.

A

`1. Peptides-amino acids

  1. Amines-Tyrosine
  2. Steroids-cholesterol
73
Q

What specific hormones do the acidophils of the anterior lobe of the pituitary make? (2)

A
  1. Growth hormone (somatotrophs)

2. Prolactin (mamotrophs)

74
Q

What specific hormoned do the basophils of the anterior lobe of the pituitary make?

A
  1. Thyroid stimulating hormone (TSH) T3 and T4 (regulation of cellular metabolism)
  2. Follicle stimulating hormone (FSH) progesterone and estrogen (follicle development)
  3. Lutenizing hormone (LH) testosterone (spermatogenesis)
  4. Adrenocorticortophic hormone (ACTH) cortisol/androgen (regulate metabolism, immune responses, and secondary sex characteristics)
75
Q

What do somatotrophs do?

A

They contribute to bone and soft tissue growth

76
Q

Which hormone derived from the anterior pituitary does not use an intermediary of secondary type of hormone?

A

prolactin

77
Q

What do mamotrophs do?

A

they initiate and maintain post partum lactation

78
Q

What do thyrotrophs do? Where are they made

A

They regulate cellular metabolism. They are made in the basophils of the anterior lobe.

79
Q

What control follicle development? Where is this hormone made?

A

Gonadotrophs. Made in the basophils of the anterior lobe.

80
Q

What do gonadotrophs do (2 things)

A
  1. follicle development (via progesterone and estrogen)

2. Testosterone (via lutenizing hormone) for spermatogenesis.

81
Q

What are the three factors released in response to low body temperature.

A

Thyroid hormone releasing hormone (THRH) is released from the hypothalamus and stimulates the thyrotropes of the anterior pituitary to produce Thyroid Stimulating hormone (TSH). TSH Stimulates the follicular cells of the thyroid to produce and release Thyroid hormone (T3 and T4) that increase metabolic activity of target cells to increase the core body temperature.

82
Q

What happens when the body temperature is low?

A
  1. Hypothalamus secretes thyrotropin-releasing hormone
  2. Thyrotropic cells in the anterior pituitary release thyroid stimulating hormone.
  3. TSH stimulates the thyroid gland to release thyroid hormone
  4. TH increases metabolic activity, increasing basal body temp
  5. increased body temp is detected by hypothalamus and secretion of TRH is inhibited. Thyroid hormone blocks thyrotropin releasing hormone and thyrotropic cells, inhibiting synthesis and release of TSH. This dampens TH of the thyroid.
83
Q

What are the general mechanisms for dampening anterior pituitary hormone production?

A

The physiological response to the hormone and/or the increased levels of the pituitary and peripheral endocrine organ hormones.

84
Q

Where are C cells found and what do they do?

A

They are found in the thyroid gland, they are lightly stained. They are responsible for calcitonin secretion. Calcitonin lowers blood calcium levels.

85
Q

What do the follicular epithelium of the thyroid do?

A

They produce T3 andd T4. They are darker stained than C cells and they initiate:
cell growth and differentiation
cellular metabolism
protein, lipid, and carbohydrate metabolism

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