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2. Microanatomy > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

What are the different types of endocrine organs?

A

Pituitary, thyroid, parathyroid, adrenal, pineal
Sole function is to synthesize and secrete hormones

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2
Q

Hormones

A

Chemical messengers that are carried via blood to distant target cells

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3
Q

Water-soluble hormones

A

Act via specific cell-surface receptors, then activate a second messenger

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4
Q

Lipid soluble hormones

A

Diffuse across the cell membrane

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5
Q

Endocrine hormones

A

Hormones released into the blood and acts on distant cells (pituitary hormones)

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6
Q

Paracrine hormones

A

Hormones diffused locally and acts on neighboring cells (NTs)

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7
Q

Autocrine hormones

A

Acts on cell that is producing it (T lymphocyte proliferation)

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8
Q

Where are diffuse endocrine cells distributed?

A

Individually or in small groups within the epithelium of the digestive system
(argentaffin cells)

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9
Q

Pituitary is connected via ________ with the hypothalamus

A

Infundibulum (funnel-like structure)

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10
Q

Adenohypophysis (anterior lobe)

A

Develops from Rathke’s pouch (pharyngeal ectoderm)
Consists of Pars distalis, tuberalis and intermedia

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11
Q

Neurohypophysis (posterior lobe)

A

Hypothalamus invagination (diencephalons)
Consists of Pars nervosa and infundibulum

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12
Q

What is the space between the pars intermedia and distalis?

A

A remnant of the cavity of Rathke’s Pouch

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13
Q

Where is the only true division of the anterior and posterior lobe?

A

Human and to some extent bovine and porcine

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14
Q

Pars distalis

A

Cells arranged in irregular cords that lie adjacent to sinusoids
Two cell types: chromophils (acidophils and basophils) and chomophobes

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15
Q

Acidophils

A

PAS negative with protein secretion
Somatotroph (GH) and lactotroph/mammotroph (prolactin)

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16
Q

Basophils

A

PAS positive with glycoprotein secretion
Gonadotroph (FSH and LH), thyrotroph (TSH) and corticotroph (ACTH)

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17
Q

Percentage of different cell types

A

Somototroph 50%
Mammotroph 20%
Corticotroph 20%’
Gonadotroph 5%
Thyrotroph 5%

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18
Q

Pars intermedia

A

Melanotrophs secrete MSH
Contain colloid-containing cysts (remannt of Rathke’s pouch)

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19
Q

What other cells does pars intermedia have?

A

Coricotrophs
Can hypertrophy/ hyperplasia in horse –> excessive secretin of ACTH –> excessive secretion of cortisol from adrenal cortex –> Cushing’s syndrome

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20
Q

Where are MSH, ACTH and B endorphin derived from?

A

Pro-opiomelanocortin

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21
Q

Pars nervosa

A

Contains axons of supraoptic (SO) and paraventricular nuclei (PV) whose cells bodies are in the hypothalamus

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22
Q

Pars nervosa cells

A

Oxytocin and vasopressin transported to distal ends of axons stored in sites called Herring bodies

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23
Q

What are axons of pars nervosa surrounded by?

A

Oligodendrocyte called pituicyte

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24
Q

Hypothalamic hypophyseal portal system

A
  1. Hypothalmic secretions (GnRH, GHRH, CRH) enter capillary plexus
  2. Drain into hypothalamus-hypophyseal portal vein
  3. Drained into a secondary capillary plexus with surrounding acidophils and basophils
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25
Q

Portal vein

A

Vein interposed between two capillary networks
Hypophseal vein interposed between primary capillary plexus and secondary capillary plexus

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26
Q

What are the anterior pituitary hormones?

A

GnRH
CRH
TRH
PRH
GHRH

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27
Q

GnRH

A

Pituitary hormone: LH, FSH
Target: reproductive system
Effects: stimulates production of sex hormone by gonads, stimulates production of sperm and eggs

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28
Q

TRH

A

Pituitary hormone: TSH
Target: thyroid gland
Effects stimulates release of thyroid hormone, regulates metabolism

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29
Q

PRH

A

Inhibited by PIH

Pituitary hormone: PRL
Target: Mammary glands
Effects: promotes milk production

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30
Q

GHRH

A

Inhibited by GHIH

Pituitary hormone: GH
Target: Liver, bone, muscle
Effects: induces targets to produce insulin-like GF! Stimulate body growth and higher metabolic rate

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31
Q

CRH

A

Pituitary hormone: ACTH
Target: Adrenal glands
Effects induces targets to produce glucocorticoids, regulate metabolism and stress response

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32
Q

What is the posterior pituitary hormone?

A

ADH

Pituitary hormone: stores ADH
Target: kidneys, sweat glands, circulatory system
Effects: water balance

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33
Q

Dwarfism, Gigantism, and acromegaly

A

Lower GH before puberty
Higher GH before pubert
Higher GH after puberty

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34
Q

Hypo or hyperthyroidism

A

Lower TSH or higher TSH

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35
Q

Cushing’s syndrome and Addisons disease

A

Higher ACTH
Lower ACTH

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36
Q

Prolactinemia

A

Higher prolactin due to tumor of mammotrophs
Common in humans
Leads to male infertility

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37
Q

Diabetes insipidus

A

Lower ADH

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38
Q

Thyroid gland

A

2 lobes connected by isthmus that envelope from endoderm
Made of follicles
Filled with thyroglobulin glycoprotein (colloid)

39
Q

What is the follicle of the thyroid gland lined by?

A

Simple cuboidal epith. that contains follicular cells (98%) and parafollicular cells (2%)

40
Q

What is unique about the thyroid gland?

A

Only endocrine gland where secretion is first stored extracellularly in lumen then reabsorbed and secretes into blood

41
Q

What stain is used for parafollicular cells?

A

Immunicytochemical stain

42
Q

Follicular cells epithelium

A

Cuboidal then columnar when stimulated by TSH and squamous when inactive

43
Q

What are follicular cells involved in?

A

The synthesis and release of thyroid hormones T4 (abundant) and T3 (more potent)

44
Q

Resting follicle

A

Large
Lined by squamous with microvilli
Dark nucleus
Large amount of acidophillic colloid in lumen

45
Q

Active follicle

A

Small
Lined by cuboidal to low columnar with more microvilli
Pale nucleus
Little colloid with scalloped border

46
Q

What are the steps involved in synthesis and release of thyroid hormone

A
  1. Synthesis of thyroglobulin
  2. Uptake of iodide
  3. Oxidation of iodide
  4. Tyrosine iodination
  5. Resorption if thyroglobulin and release of T4 and T3 into circulation
47
Q

TRH

A

Thyrotropic releasing hormone
Stimulates TSH secretion from pituitary

48
Q

TSH

A

Thyroid stimulating hormone
Stimulates thyroid gland to secrete T3 and T4

49
Q

What does the release of T3 and T4 cause?

A

Increase the basal metabolic rate of almost all cells of the body
Promotes heat production
Broad effects of gene expression and induction of protein synthesis

50
Q

Simple Goiter (hypothyroid)

A

Enlarged thyroid gland due to iodide deficiency
Follicle is filled with thyroglobulin without iodination
Blood test: low T3, T4 and high TSH

51
Q

What are other names for simple goiter?

A

Myxedema in adults
Cretinism in young

52
Q

Graves’ disease (exopthalmic goiter, hyperthyroid)

A

Autoimmune disease from binding of autoimmune antibodies to TSH receptors on follicle cells
Increase synthesis and secretion of T3 and T4

53
Q

What are the symptoms of Graves’ disease?

A

Weight loss, bulging eyes, nervous excitability
Blood test: high T3 and T4 and low TSH

54
Q

What are the 2 cells in the parathyroid gland?

A

Chief cells and oxyphil cells

55
Q

Chief cells

A

Most numerous
Secrete parathyroid hormone to raise blood calcium levels and stimulate osteoclast activity

56
Q

How do chief cells worK?

A

By increasing the reabsorption of calcium and decreasing reabsorption of phosphates at the PT of the kidney

57
Q

Oxyphil cells

A

Lightly stained and few
In horse and large ruminants, rare in other species

58
Q

Hypocalcemia

A

Stimulates chief cells to increase parathyroid hormone secretion —> stimulates osteoclasts —> stimulates calcium uptake in kidney —> increases calcium uptake in intestine —> increases blood calcium level

59
Q

Hypercalcemia

A

Stimulates parafollicular cells to increase calcitonin secretion —> inhibits osteoclasts —> stimulates calcium deposition in bones —> reduce calcium uptake in kidney —> decreased blood calcium level

60
Q

Adrenal Gland

A

Located at the anterior pole of each kidney
Covered by a capsule with a cortex and medulla
Parenchymal cells

61
Q

Parenchymal cells

A

Secrete steroid hormones
Abundant SER, mitochondria with tubular cristae and lipid droplets

62
Q

Cortex of the adrenal gland

A

Originates from mesoderm
Divided into Zona glomerulosa, fasciculata and resticularis

63
Q

Zona Granulosa

A

Secretes aldosterone and regulates electrolyte balance
Stimulated by hypovolemia, hyponatremia and hyperkalemia

64
Q

What is ZG hormone production stimulated by?

A

Angiotensin II and ACTH (limited control)

65
Q

How is ZG arranged?

A

Arranged in arches for horses, carnivores and pigs
Clusters for ruminants and man

66
Q

Zona fasciculata

A

Largest region (80% of vol)
Regulate carb metabolism
Stimulated by ACTH

67
Q

How is ZF useful?

A

In treating stress, autoimmune diseases, chronic inflammation and promoting acceptance of heterologous grafts

68
Q

What are the 3 side effects of long-term glucocorticord therapy?

A

Lymphopenia, eosinopenia and neutrophilia

69
Q

Outer fasciculata

A

Spongiosa (spongiocytes) because cells appear empty due to high lipid (vacuolated)

70
Q

Inner fasciculata

A

Secretes glucocorticoids (cortisol and corticosterone)

71
Q

Zona Reticularis

A

Deepest layer of the cortex (7%)
Secretes androgens and small amount of glucocorticoids stimulated by ACTH

72
Q

What is the important role of ZR?

A

Onset of puberty in humans especially in growth of pubic and axillary hairs

73
Q

What controls the 3 layers of the adrenal gland?

A

Renin-angiotenson controls ZG
Hypothalamus- pituitary control ZR and ZF

74
Q

Medulla of the adrenal gland

A

Originates from ectodermal neural crest cells (modified postgang. sympathetic neurons)

75
Q

Medulla location (adrenal gland)

A

Present as a second organ in lower vertebrates
Randomly mixed with cortical tissue in birds
Centrally located in mammals

76
Q

What does the medulla secrete? (Adrenal gland)

A

Epinephrine and some norepinephrine
Catecholamine release under nervous control (pregang sympath)

77
Q

Cortical capillaries

A

Fenestrated sinusoids
Drain into medullary vein

78
Q

Medullary artery

A

Drain into medullary and suprarenal vein

79
Q

Clin sigs of adrenal gland

A

Cushing’s: Higher ACTH and Cortisol
Addison’s: Lower ACTH, aldosterone, and cortisol
Hirsutism or Virilization (F): Higher ACTH and adrogens

80
Q

Pineal Gland

A

From root of diencephalon
Composed of pinealocytes and neuroglia cells

81
Q

What are pinealocytes function?

A

Secrete melatonin responsible for seasonal cyclicity in horses (long) and sheep and goats (short-day breeder)

82
Q

Enteroendocrine (argentaffin) cells

A

In basal area of the crypt
Released into adjacent capillaries
Chromaffin-positive

83
Q

What do enteroendocrine (argentaffin) cells secrete?

A

Gastrin, secretin, CCK, somatostatin, vasoactive intestinal peptide

84
Q

Islets of Langerhans (pancreas)

A

Alpha (20%)- glucagon
Beta (70%)- insulin
Delta (5%)- somatostatin

85
Q

JG cells

A

Secrete renin in repsonse to low BP, hypovolemia, or hyponatremia

86
Q

Erythropoietin

A

Secreted in response to decreased oxygen supply to the kidney

87
Q

Leydig and Sertoli cells

A

Secrete testosterone
Secrete estrogen and inhibin

88
Q

Theca interna

A

Have LH receptors and secrete testosterone

89
Q

Granulosa cells

A

Have FSH receptors and convert T into estrogen (released into antrum and blood)

90
Q

Endometrial cups

A

Consists of modified chronic epithelial cells that secrete eCG (FSH-like)

91
Q

What happens when pregnancy doesn’t occur?

A

Endometrium secretes PGF2-alpha that causes corpus lutem and begins the new estrus cycle

92
Q

Chorionic epithelium

A

Secretes HcG (LH-like)

93
Q

Placenta

A

Secretes estrogen and progesterone

2. Microanatomy (16 decks)

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