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Endocrine System Flashcards

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USMLE® Step 1 flashcards
1
Q

What are considered to be the “classical” endocrine glands?

A 
Hypothalamus
Anterior and posterior lobes of pituitary
Thyroid
Parathyroid
Adrenal Cortex
Adrenal Medulla
Gonads
Placenta
Pancreas (both endocrine and exocrine)
Pineal gland
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2
Q

(T/F) The kidney also has important endocrine functions

A

True

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3
Q

Steroid hormones are derived from what general precursor?

A

Cholesterol

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4
Q

Peptide and protein hormones are synthesized from what?

A

Amino Acids

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5
Q

Peptides modified by addition of carbohydrate groups are known as what?

A

Glycoproteins

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6
Q

Amine hormones are modified derivatives of what amino acids?

A

Tyrosine or Tryptophan

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7
Q

The pituitary gland is also known as what?

A

Hypophysis

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8
Q

What are two parts of the pituitary gland?

A

Adenohypophysis (anterior lobe)

Neurohypophysis (posterior lobe)

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9
Q

The anterior lobe of the pituitary gland is also known as what?

A

Adenohypophysis

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10
Q

The posterior lobe of the pituitary gland is also known as what?

A

Neurohypophysis

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11
Q

Synthesis and secretion of all pituitary hormones is controlled by what part of the brain?

A

Hypothalamus

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12
Q

The pituitary gland lies in a shallow depression known as the _______, which is a saddle-shaped part of the ________ bone.

A

Sella Turcica;

Sphenoid bone

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13
Q

How is the adenohypophysis connected to the hypothalamus

A

Blood vessels: Hypophysial portal circulation

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14
Q

The pituitary gland lies beneath the…

A

Hypothalamus

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15
Q

The adenohypophysis is embryologically derived from what?

A

Rathke Pouch

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16
Q

Why do endocrine gland typically have a large blood supply?

A

Blood supply is method of delivery of hormones to distant target tissues

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17
Q

What are some examples of steroid hormones?

A

Estradiol
Testosterone
Cortisol
Aldosterone

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18
Q

What are some examples of peptide and protein hormones?

A

Prolactin
Growth Hormone
Insulin
Vasopressin

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19
Q

What are some examples of glycoprotein hormones?

A

LH
FSH
TSH

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20
Q

What are examples of amine hormones derived from tyrosine?

A

Thyroid Hormone
Norepinephrine
Epinephrine

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21
Q

What are examples of amine hormones derived from tryptophan?

A

Melatonin

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22
Q

What is Rathke’s pouch?

A

Hypophysial diverticulum: An evagination of the oral ectoderm that extends upward from the roof of the primordial oral cavity to form the Adenohypophysis

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23
Q

The neurohypophysis is embryologically derived from

A

Neurohypophysial diverticulum: a down growth from the floor of the diencephalon

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24
Q

The neurohypophysial diverticulum is a down growth from the floor of what?

A

Diencephalon

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25
Q

The diencephalon is made up of what parts?

A

Thalamus
Hypothalamus
Pineal Body

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26
Q

What is the name of the downgrowth of the hypothalamus?

A

Median Eminence of Hypothalamus

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27
Q

What are the subdivisions of the adenohypophysis?

A

Pars distalis
Pars intermedia
Pars tuberalis

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28
Q

What is the main body of the neurohypophysis also known as?

A

Pars nervosa

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29
Q

Cell types of the Pars distalis are divided into two categories, what are they?

A

1) Chromophil Cells

2) Chromophobe Cells

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30
Q

Chromophil cels, a type of cell within the Pars distalis of the adenohypophysis, can be further divided into two cell types. What are they?

A
  • Acidophils

- Basophils

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31
Q

Acidophil cells within the Pars distalis can be described as what?

A
  • Most numerous cell type

- Red-staining cytoplasmic granules

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32
Q

There are two types of acidophilic chromophil cells, what are they?

A
  • Somatotrophic cells

- Mammotrophic cells

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33
Q

Somatotrophic cells synthesize and secrete what?

A

Growth Hormone - the most important hormone for normal growth; also has important effects on protein, carbohydrate, and fat metabolism.

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34
Q

What do the mammotrophic cells of the Pars Distalis synthesize and secrete?

A

Prolactin - the major hormone responsible for milk production; also important in normal development of breast glandular tissue.

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35
Q

How would you describe basophillic Chromaphil cells of the pars distalis?

A

-Less numerous, blue-staining cytoplasmic granules

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36
Q

What are the types of Basophillic Chromophil cells of the Pars Distalis?

A
  • Thyrotrophic cells
  • Corticotrophic cells
  • Gonadotrophic cells
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37
Q

What do the thyrotrophic basophilic chromophil cells synthesize and secrete?

A

synthesize/secrete thyroid stimulating hormone (TSH), which stimulates growth and activity of thyroid hormone-secreting cells of the thyroid gland

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38
Q

What do corticotrophic cells synthesize and secrete?

A

synthesize/secrete adrenocorticotrophic hormone (ACTH), which stimulates growth and activity of steroid hormone-secreting cells of the adrenal cortex

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39
Q

What do gonadotrophic cells synthesize and secrete?

A

synthesize/secrete luteinizing hormone (LH) and follicle stimulating hormone (FSH), which regulate growth and activity of ovaries and testes, including secretion of the sex steroids, estrogen and testosterone

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40
Q

How would you describe Chromophobe cells of the Pars Distalis?

A

exhibit only faint/weak staining, and probably represent committed stem cells and immature forms of acidophils and basophils, as well as degranulated acidophils/basophils

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41
Q

Cells of the pars distalis are arranged in “__________” surrounded by numerous _____________ and _________ fibers

A
  • clumps
  • fenestrated capillaries (plus other small vessels)
  • thin connective tissue
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42
Q

What type of capillaries are found in the pars distalis?

A

fenestrated

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43
Q

How would you describe the Pars Intermedia of the Adenohypophysis?

A

-contains colloid-filled follicles/vesicles (remnants of lumen of Rathke’s pouch) and melanoyte stimulating hormone (MSH) secreting cells –MSH is a relatively unimportant hormone in humans

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44
Q

How would you describe the Pars Tuberalis of the Adenohypophysis?

A

surrounds the infundibular stem, contains some cell types in common with the pars distalis and a few other cell types with unknown function

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45
Q

Which portion of the Adenohypophysis represents remnants of the lumen of Rathke’s pouch?

A

Pars Intermedia

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46
Q

The median eminence of the hypothalamus contains what?

A

Hypothalamic neurons with terminals in the median eminence. These neurons secrete regulatory hormones for anterior pituitary cells.

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47
Q

Which artery supplies the pars tuberalis of the adenohypophysis?

A

Super Hypophysial artery

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48
Q

Immuno-staining allows for the identification of what?

A

Hormone-specific cell types

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49
Q

Where does the blood supply come from that reached the anterior pituitary?

A

Hypothalamus

Primary capillary plexus surrounding median eminence -> hypophysial portal veins -> capillary plexus of pars distalis

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50
Q

The primary capillary plexus is a dense capillary plexus surrounding what?

A

Median Eminence of the Hypothalamus

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51
Q

How do hormones secreted by cells of the pars distalis reach the rest of the body?

A

Venous Drainage into systemic circulation

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52
Q

The hypothalamohypophyseal tract contains the unmyelinated axons of __________ whose cells bodies are located in the ________ and _________ of the hypothalamus.

A

Neurosecretory cells
Supraoptic
Paraventricular nuclei

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53
Q

What does the hypothalamohypophyseal tract transport to the pars nervosa?

A 
Oxytocin
Antidiuretic hormone (ADH; vasopressin)
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54
Q

The pars nervosa contains the distal ends of what?

A

hypothalamohypophyseal tract axons and is the site where neurosecretory granules in these axons are stored in accumulations known as Herring Bodies

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55
Q

The axon terminals of the Neurohypophysis are supported by glial cells called what?

A

Pituicytes

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56
Q

What is the blood supply which primarily supplies the pars nervosa?

A

Inferior hypophysial artery

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57
Q

What are stored in Herring Bodies?

A

vasopressin

oxytosin

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58
Q

The cell bodies which synthesize and secrete Vasopressin/Antidiuretic hormone (ADH) are predominantly found where?

A

In the Supraoptic nuclei of the hypothalamus

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59
Q

The cell bodies which synthesize and secrete Oxytocin are found where?

A

In the Paraventricular nuclei of the hypothalamus

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60
Q

What are the main actions of vasopressin?

A
  • Regulation of plasma osmolarity through changing water permeability in the collecting tubules of the kidneys
  • Constriction of arterioles (smooth muscle contraction)
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61
Q

What are the main actions of oxytocin?

A
  • Stimulate myoepithelial cells contraction in milk let-down reflex
  • Stimulate contraction of uterine smooth muscle during labor
62
Q

What causes gigantism?

A

Growth-hormone secreting adenomas in adenohypophysis present before closure of growth plates
or
acromegaly when they develop after long bone growth has ceased

63
Q

What causes Cushing’s disease?

A

ACTH-secreting adenomas resulting in continuous stimulation of the adrenal cortex (hypercortisolism)

64
Q

What is galactorrhea?

A

Milk oozing from nipples

65
Q

What causes galactorrhea?

A

Prolactin-secreting adenomas

66
Q

Besides galactorrhea, what else do prolactin-secreting adenomas cause?

A

Hypogonadism/infertility in both males and females.

67
Q

What is panhypopituitarism?

A

Failure of all anterior lobe hormone producing cells

68
Q

Isolated hGH deficiency in children results in what?

A

Decreased rate of linear growth, short stature, mild obesity, and often delayed puberty

69
Q

What does Vasopressin (ADH) deficiency lead to?

A

Central (neurogenic) diabetes insipidus–in the absence (or severe deficiency) of ADH, the collecting ducts cannot reabsorb water, so excess water is excreted in urine (as much as 10-12 liters per day). When water is being excreted faster than it can be replaced (by drinking), the salts/minerals in extracellular fluids (like plasma) become increasingly concentrated, resulting in hyperosmolarity.

70
Q

In general, what are the functions of thyroid hormones?

A
  • regulation of metabolism and basal metabolic rate
  • effects on growth and development
  • cardiovascular function
  • maturation of the CNS
71
Q

What cells are scattered between thyroid follicles?

A

Parafollicular cells (C-cells)

72
Q

Where are parafollicular cells derived from and what do they secrete?

A
  • Derivation: Neural Crest

- Secrete: Calcitonin (calcium homeostasis)

73
Q

What type of epithelium are thyroid follicular epithelial cells?

A

Simple cuboidal epithelium

74
Q

What are the thyroid hormones?

A

T3 (tri-iodothyronine)

T4 (Thyroxine)

75
Q

The thyroid hormones contain what?

A

contain iodine, so sufficient iodine must be supplied by diet and most of this iodine must be “trapped” in the thyroid gland

76
Q

Where are T3 and T4 stored?

A

extracellularly attached to thyroglobulinin colloid until the gland is stimulated to secrete. When secretion is stimulated, the hormones must first be brought back into follicular cells by endocytosis and then secreted across the basilar membrane and absorbed into capillaries.

77
Q

Low power view of the thyroid gland shows many_________ –lined by___________ cells and containing _______ (homogenously pale staining). Collagenous _______ (mostly sheared apart in this section) divide the gland into lobules and convey blood vessels, lymphatics.

A

follicles
thyroid follicular
colloid
septae

78
Q

What happens to the epithelium as thyroid follicles become more or less active?

A

More active = height increases (cuboidal to columnar)

Less active = height decreases

79
Q

What is the normal stimulus for follicular cell activity of the Thyroid gland?

A

TSH

80
Q

What is Thyroglobin (TG)? Where is it synthesized? Where is it secreted?

A

a glycoprotein containing large quantities of tyrosine, is synthesized on the RER and Golgi apparatus of follicular cells ——-> secreted across the apical membrane into the follicular lumen

81
Q

T3 binds to what in target cells?

A

Nuclear receptors

82
Q

Why are heart arrhythmias and increased cardiac oxygen demand among effects of hyperthyroidism?

A

If essentially all cells are going to increase energy usage, then it stands to reason that the cardiovascular system must be “turned up” by thyroid hormone in order to deliver more oxygen and energy substrate to the rest of the body.

83
Q

Thyroid hormone is also necessary for ____________ –untreated hypothyroidism in childhood results in _______, despite normal hGH.

A

normal growth

decreased linear growth

84
Q

Thyroid hormone is also necessary for ___________ during a critical period in the first months after birth.

A

normal maturation of the CNS

85
Q

Undiagnosed / untreated congenital hypothyroidism results in irreversible ____________.

A

failure of CNS maturation (cretinism)

86
Q

Grave’s disease is caused by what?

A

Hyperthyroidism

87
Q

TSH receptors on thyroid cells are also activated by what?

A

Thyroid stimulating immunoglobuins

-antibodies against the TSH receptor –> immunoglobulin G (lgG) fraction of plasma proteins

88
Q

What effect do “thyroid stimulating immunoglobulins have on TSH receptors?

A

Same as TSH itself (increased cAMP) —> results in continuous stimulation of the thyroid gland, just as if TSH levels were continuously elevated –> increased T3/T4 synthesis and secretion, hypertrophy/hyperplasia of the gland –> hyperthyroidism and goiter (enlarged thyroid).

89
Q

A patient who comes to you with exopthalmos, thyroid stare, and diffusely enlarged thyroid gland most likely has what?

A

Grave’s disease

90
Q

Histologically, how does a section of a normal thyroid differ from one with Grave’s disease?

A

Grace’s disease thyroid shows:

follicular cell hyperplasia and crowding, depletion and scalloping of colloid

91
Q

What does dietary deficiency of iodine cause?

A

Hypothyroidism

- cannot synthesize thyroid

92
Q

Lack of ________ results in persistent elevation of ______. Thyroid follicular cells respond by ________ and storing ___________ in follicles which leads to __________ of the thyroid gland or goiter

A 
negative feedback
TSH
growing/dividing
thyroglobulin
diffuse enlargement
93
Q

What is Hashimoto’s Thyroiditis?

A

Common form of thyroiditis (inflammation of the thyroid gland

94
Q

Treatment of hypothyroidism includes…

A

treatment of the underlying cause (if possible) and thyroid hormone replacement –given by mouth as T4 (thyroxine).

95
Q

What are parafollicular cells (C-cells)?

A

Larger, pale-staining cells found adjacent to / between thyroid follicles

96
Q

Regarding the parathyroid gland, there are normally _____ superior parathyroids from __________ and _____ inferior parathyroids from ________.

A

4 to 2
4th pharyngeal pouch
2
3rd pouch

97
Q

What is the location of the the parathyroid glands?

A

Posterior surface of the thyroid gland

98
Q

What does the Parathyroid gland synthesize/secrete? Which does what?

A

Synthesize/secrete parathyroid hormone (parathormone or PTH) -increases free ionized calcium concentration in blood –PTH is critical for calcium regulation

99
Q

As people age, what can be found scattered throughout the parathyroid glands?

A

Adipocytes

100
Q

The main cells seen in the parathyroid glands are________ or________ cells, which are small cells with ________staining cytoplasm. These are the cells which are known to detect blood ___________ concentration and synthesize/secrete _______.

A

“principal” / “chief”
scant blue
calcium
PTH

101
Q

A second cell type in the parathyroid, besides chief cells, are _______, which can also be readily seen as clusters of ________ cells with __________ cytoplasm. The functional significance of these cells are poorly understood.

A

oxyphil cells
larger
abundant pink-staining

102
Q

What types of sensor do cheif cells have on their cell membranes?

A

Calcium sensors

103
Q

Cheif cells secrete what?

A

PTH

104
Q

What target tissues are PTH receptors found on?

A

Osteoblasts

Renal tubular epithelial cells

105
Q

What effect does PTH have on osteoblasts?

A

after PTH binding, osteoblasts stimulate osteoclasts to reabsorb bone, mobilizing calcium and phosphate

106
Q

What effect does PTH have on renal tubular epithelial cells?

A

a) PTH binding promotes decreased urinary calcium excretion, increased phosphate excretion
b) PTH up-regulates the renal enzyme for activation of Vit D, increases GI absorption of calcium and phosphate

107
Q

primary hyperparathyroidism causes what?

A

commonly due to parathyroid adenoma (or chief cell hyperplasia), excess PTH secretion leads to “stones, bones and groans”
Stones –urinary tract stones occur due to increased urinary calcium (even though the direct effect of PTH is to decrease urinary calcium excretion, the plasma calcium rises enough to saturate tubular reabsorption of filtered calcium)
Bones –excess PTH promotes bone demineralization

108
Q

What encloses the Adrenal glands?

A

Renal Fasicia

109
Q

The adrenal glands are surrounded by what?

A

Perirenal fat

110
Q

What hormones are known as the catecholamines?

A

Norepinephrine

Epinephrine

111
Q

What features are common to all three layers of the Adrenal glands?

A

abundant mitochondria, lipids (including vesicles containing cholesterol esters) and smooth endoplasmic reticulum; mitochondria with tubular cristae –features of steroid-producing cells in general.

112
Q

The Z. glomerulosa cells, compared to the fasciculata cells, are characterized by …

A

Less cytoplasm and fewer lipid droplets

113
Q

What is synthesized in the Z. Glomerulosa? What is its action?

A

mineralocorticoids, principally aldosterone –the main action of aldosterone is increased sodium and water reabsorption in renal collecting ducts (results in increased ECF volume —> increased blood pressure)

114
Q

The Zona fasciculata cells of the adrenal gland is the widest of the zones and is arranged how?

A

In parallel cords or plates (typically 2 cells thick) and is separated by capillaries parallel to the plates.

115
Q

What is characteristic about the Zona Fasciculata zone compared to the other zones?

A

More cytoplasm than cells in the other zones and abundant lipid droplets

116
Q

What does the Zona fasciculata cells synthesize and secrete? Which fuctions to do what?

A

Synthesize / secrete glucocorticoids, primarily cortisol –critical for normal carbohydrate metabolism, maintenance of blood sugar between meals/ fasting, adaptation to stress, maintenance of blood pressure (permissive effect on catecholamines)

117
Q

The adrenal cortex is subdivided into what 3 layers?

A

Z Glomerulosa (outermost)
Z. Fasciculata
Z. Reticularis (innermost)

118
Q

The Z Reticularis cells of the Adrenal Cortex are arranged how? And are surrounded by what?

A
  • Arranged in irregular branching network cellular chords

- Surrounded by blood vessels and connective tissue

119
Q

The Z. Reticularis cells of the Adrenal cortex synthesize and secrete what?

A

adrenal androgens

androstenedione and DHEA

120
Q

How would you describe the blood supply of the adrenal gland?

A

The blood supply of the adrenal gland “mirrors” the cell arrangement of the zones
–capillaries: in
“loops” around z glomerulosa clusters, parallel to plates of z fasciculata cells and irregularly branching in the z reticularis;

also bathes successive layers in secretions and intermediates from other layers.

121
Q

What system regulates aldosterone? Which is important for what?

A

renin-angiotensin-aldosterone system (RAAS)

–important response to decreased blood pressure / decreased renal perfusion

122
Q

What is involved in cortisol regulation?

A

hypothalamic-hypophysial-adrenal cortical axis (CRH –> ACTH –> Cortisol)

123
Q

What is involved in adrenal androgen regulation?

A

largely by ACTH (synthesis of androgens is increased when ACTH levels are elevated, as in Cushing’s disease) but not completely understood

124
Q

What is addison’s diease?

A

Destruction of the adrenal cortex (autoimmune, tuberculosis)
All adrenal steroids are affected –mineralocorticoids, glucocorticoidsand androgens –mineralocorticoidsand glucocorticoidsare necessary for life

125
Q

What is Cushing’s diease?

A

ACTH-secreting adenoma of the anterior pituitary

High ACTH –> drives cortisol and androgen synthesis/release

126
Q

What is Cushing’s syndrome?

A

Functional tumor of the adrenal cortex OR administration of glucocorticoids in pharmacological doses (High cortisol –> negative feedback inhibition of pituitary ACTH release)

127
Q

What is Conn’s Syndrome?

A

Adrenal cortical adenoma of glomerulosa cells which leads to Hyperaldosteronemia

128
Q

The suprarenal medulla contains ____________ and large_______draining into a large_________.

A 
medullary cells (pheochromocytes)
venous channels 
central vein.
129
Q

What are Pheochromocytes?

A

Modified post-ganglionic sympathetic nerve cells (neural crest origin) in the suprarenal medulla.

130
Q

Catecholamines, once made by the adrenal medulla, are packaged and stored in what?

A

Secretory graunles

131
Q

Besides the Pheochromocytes, what other cells are located in the suprarenal medulla? What do they do?

A

two types of medullary cells –most synthesize / secrete epinephrine (E) and a smaller population secretes norepinephrine (NE)

132
Q

How would you histologically describe Pheochromocytes of the Suprarenal medulla?

A

seen as large cells in clusters, with abundant finely granular cytoplasm staining faintly basophilic (blue) with standard H&E stain

133
Q

Pheochromocytes stain a yellow-brown color with _________ (sometimes called “_________ cells”)

A

chromic salts

chromaffin

134
Q

What type of nerves control medullary cells?

A

Preganglionic sympathetic

135
Q

Pheochromocytomas are what? Which produce what?

A

Tumors of suprarenal medullary cells. They produce symptoms related to excess catecholamines (“fight or flight”) including tachycardia / palpitations, elevated blood pressure (sometimes dangerously elevated), chest pain, sweating, constipation, fine tremor, and anxiety.

136
Q

The endocrine cells of the pancreas are arranged in clusters called what?

A

Islets of Langerhans

137
Q

In general, the endocrine pancreas secretes what?

A
  • Two major peptide hormones

- Two minor peptide hormones

138
Q

What are the two major peptide hormones secreted by the endocrine pancreas?

A
  • Insulin from B-cells

- Glucagon from alpha-cells

139
Q

Which cells of the endocrine pancreas secretes insulin?

A

B-cells

140
Q

Which cells of the endocrine pancreas secretes glucagon?

A

Alpha- cells

141
Q

What is the role of insulin secreted from the B-cells of the endocrine pancreas?

A
  • increases glucose movement into cells, -decreases gluconeogenesis,
  • decreases glycogenolysis,
  • increases fat deposition,
  • decreases lipolysis,
  • increases protein synthesis (increases storage of fuels through actions on liver, skeletal muscle and adipose),
  • increases potassium movement into cells;
  • decreases blood glucose, amino acids, fatty acids, keto-acids and potassium
142
Q

What is the role of glucagon secreted from the alpha-cells of the endocrine pancreas?

A
  • increases glycogenolysis and gluconeogenesis,
  • decreases glycogenesis,
  • increases lipolyis (mobilizes stored fuels mainly through action on liver and less important effect on adipose);
  • increases blood glucose, fatty acids and ketoacids
143
Q

What are the two minor peptide hormones released by the endocrine pancreas?

A

-somatostatin (inhibits insulin and glucagon release)
and
-pancreatic polypeptide (functions less well-established)

144
Q

The central core of the islets of Langerhans contains ______, with _______distributed around the outer rim. The __________(somatostatin) are scattered between _______ (suggesting a paracrine function).

A

B-cells
Alpha-cells
Gamma-cells
Alpha and B cells

145
Q

What connects alpha-cells to each other, B-cells to each other, and alpha-cells to B-cells

A

Gap junctions

146
Q

What two cell types are found in the Pineal Gland?

A
  • Pinealocytes (modified neurons)

- Neuroglial cells

147
Q

What can be seen in the pineal gland that is associated with ageing?

A

Pineal Sand

concentric accretions of calcium and magnesium phosphate

148
Q

How would one histologicall describe Pinealocytes (cells in Pineal gland)?

A

large rounded nuclei, prominent nucleoli and branching processes (processes not seen).

149
Q

Secretory granules in pinealocytes of the pineal gland contain what?

A

Melatonin and

Serotonin

150
Q

Melatonin induces__________ in activity of the ___________, __________ and ________ in response to changes in _________.

A 
rhythmic changes
hypothalamus
adenohypophysis
gonads
light reaching the retina
151
Q

Melatonin secretion is inhibited by_____ and increased in _______. The pathway from ______ to pineal is complex involving the spinal cord,__________ nerves and _________nucleus of the__________.

A 
light
darkness
retina
sympathetic
suprachiasmatic
hypothalamus
152
Q

How would one histologically describe the neuroglial cells of the pinal gland?

A

elongated nuclei and are scattered around and between clusters of pinealocytes

Medical Histology (11 decks)

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