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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
Portal vein
Vein interposed between two capillary networks Hypophseal vein interposed between primary capillary plexus and secondary capillary plexus
26
What are the anterior pituitary hormones?
GnRH CRH TRH PRH GHRH
27
GnRH
Pituitary hormone: LH, FSH Target: reproductive system Effects: stimulates production of sex hormone by gonads, stimulates production of sperm and eggs
28
TRH
Pituitary hormone: TSH Target: thyroid gland Effects stimulates release of thyroid hormone, regulates metabolism
29
PRH
Inhibited by PIH Pituitary hormone: PRL Target: Mammary glands Effects: promotes milk production
30
GHRH
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
31
CRH
Pituitary hormone: ACTH Target: Adrenal glands Effects induces targets to produce glucocorticoids, regulate metabolism and stress response
32
What is the posterior pituitary hormone?
ADH Pituitary hormone: stores ADH Target: kidneys, sweat glands, circulatory system Effects: water balance
33
Dwarfism, Gigantism, and acromegaly
Lower GH before puberty Higher GH before pubert Higher GH after puberty
34
Hypo or hyperthyroidism
Lower TSH or higher TSH
35
Cushing’s syndrome and Addisons disease
Higher ACTH Lower ACTH
36
Prolactinemia
Higher prolactin due to tumor of mammotrophs Common in humans Leads to male infertility
37
Diabetes insipidus
Lower ADH
38
Thyroid gland
2 lobes connected by isthmus that envelope from endoderm Made of follicles Filled with thyroglobulin glycoprotein (colloid)
39
What is the follicle of the thyroid gland lined by?
Simple cuboidal epith. that contains follicular cells (98%) and parafollicular cells (2%)
40
What is unique about the thyroid gland?
Only endocrine gland where secretion is first stored extracellularly in lumen then reabsorbed and secretes into blood
41
What stain is used for parafollicular cells?
Immunicytochemical stain
42
Follicular cells epithelium
Cuboidal then columnar when stimulated by TSH and squamous when inactive
43
What are follicular cells involved in?
The synthesis and release of thyroid hormones T4 (abundant) and T3 (more potent)
44
Resting follicle
Large Lined by squamous with microvilli Dark nucleus Large amount of acidophillic colloid in lumen
45
Active follicle
Small Lined by cuboidal to low columnar with more microvilli Pale nucleus Little colloid with scalloped border
46
What are the steps involved in synthesis and release of thyroid hormone
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
TRH
Thyrotropic releasing hormone Stimulates TSH secretion from pituitary
48
TSH
Thyroid stimulating hormone Stimulates thyroid gland to secrete T3 and T4
49
What does the release of T3 and T4 cause?
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
Simple Goiter (hypothyroid)
Enlarged thyroid gland due to iodide deficiency Follicle is filled with thyroglobulin without iodination Blood test: low T3, T4 and high TSH
51
What are other names for simple goiter?
Myxedema in adults Cretinism in young
52
Graves’ disease (exopthalmic goiter, hyperthyroid)
Autoimmune disease from binding of autoimmune antibodies to TSH receptors on follicle cells Increase synthesis and secretion of T3 and T4
53
What are the symptoms of Graves’ disease?
Weight loss, bulging eyes, nervous excitability Blood test: high T3 and T4 and low TSH
54
What are the 2 cells in the parathyroid gland?
Chief cells and oxyphil cells
55
Chief cells
Most numerous Secrete parathyroid hormone to raise blood calcium levels and stimulate osteoclast activity
56
How do chief cells worK?
By increasing the reabsorption of calcium and decreasing reabsorption of phosphates at the PT of the kidney
57
Oxyphil cells
Lightly stained and few In horse and large ruminants, rare in other species
58
Hypocalcemia
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
Hypercalcemia
Stimulates parafollicular cells to increase calcitonin secretion —> inhibits osteoclasts —> stimulates calcium deposition in bones —> reduce calcium uptake in kidney —> decreased blood calcium level
60
Adrenal Gland
Located at the anterior pole of each kidney Covered by a capsule with a cortex and medulla Parenchymal cells
61
Parenchymal cells
Secrete steroid hormones Abundant SER, mitochondria with tubular cristae and lipid droplets
62
Cortex of the adrenal gland
Originates from mesoderm Divided into Zona glomerulosa, fasciculata and resticularis
63
Zona Granulosa
Secretes aldosterone and regulates electrolyte balance Stimulated by hypovolemia, hyponatremia and hyperkalemia
64
What is ZG hormone production stimulated by?
Angiotensin II and ACTH (limited control)
65
How is ZG arranged?
Arranged in arches for horses, carnivores and pigs Clusters for ruminants and man
66
Zona fasciculata
Largest region (80% of vol) Regulate carb metabolism Stimulated by ACTH
67
How is ZF useful?
In treating stress, autoimmune diseases, chronic inflammation and promoting acceptance of heterologous grafts
68
What are the 3 side effects of long-term glucocorticord therapy?
Lymphopenia, eosinopenia and neutrophilia
69
Outer fasciculata
Spongiosa (spongiocytes) because cells appear empty due to high lipid (vacuolated)
70
Inner fasciculata
Secretes glucocorticoids (cortisol and corticosterone)
71
Zona Reticularis
Deepest layer of the cortex (7%) Secretes androgens and small amount of glucocorticoids stimulated by ACTH
72
What is the important role of ZR?
Onset of puberty in humans especially in growth of pubic and axillary hairs
73
What controls the 3 layers of the adrenal gland?
Renin-angiotenson controls ZG Hypothalamus- pituitary control ZR and ZF
74
Medulla of the adrenal gland
Originates from ectodermal neural crest cells (modified postgang. sympathetic neurons)
75
Medulla location (adrenal gland)
Present as a second organ in lower vertebrates Randomly mixed with cortical tissue in birds Centrally located in mammals
76
What does the medulla secrete? (Adrenal gland)
Epinephrine and some norepinephrine Catecholamine release under nervous control (pregang sympath)
77
Cortical capillaries
Fenestrated sinusoids Drain into medullary vein
78
Medullary artery
Drain into medullary and suprarenal vein
79
Clin sigs of adrenal gland
Cushing's: Higher ACTH and Cortisol Addison's: Lower ACTH, aldosterone, and cortisol Hirsutism or Virilization (F): Higher ACTH and adrogens
80
Pineal Gland
From root of diencephalon Composed of pinealocytes and neuroglia cells
81
What are pinealocytes function?
Secrete melatonin responsible for seasonal cyclicity in horses (long) and sheep and goats (short-day breeder)
82
Enteroendocrine (argentaffin) cells
In basal area of the crypt Released into adjacent capillaries Chromaffin-positive
83
What do enteroendocrine (argentaffin) cells secrete?
Gastrin, secretin, CCK, somatostatin, vasoactive intestinal peptide
84
Islets of Langerhans (pancreas)
Alpha (20%)- glucagon Beta (70%)- insulin Delta (5%)- somatostatin
85
JG cells
Secrete renin in repsonse to low BP, hypovolemia, or hyponatremia
86
Erythropoietin
Secreted in response to decreased oxygen supply to the kidney
87
Leydig and Sertoli cells
Secrete testosterone Secrete estrogen and inhibin
88
Theca interna
Have LH receptors and secrete testosterone
89
Granulosa cells
Have FSH receptors and convert T into estrogen (released into antrum and blood)
90
Endometrial cups
Consists of modified chronic epithelial cells that secrete eCG (FSH-like)
91
What happens when pregnancy doesn't occur?
Endometrium secretes PGF2-alpha that causes corpus lutem and begins the new estrus cycle
92
Chorionic epithelium
Secretes HcG (LH-like)
93
Placenta
Secretes estrogen and progesterone

2. Microanatomy (16 decks)

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