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Microanatomy 2 > Endocrine System > Flashcards

Endocrine System Flashcards

1
Q

What are Ductless glands

A

Pituitary
Thyroid
Parathyroid
Adrenal
Pineal

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2
Q

Endocrine

A

Hormone released into blood and acts on distant cells

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3
Q

Paracrine

A

Hormone is diffused locally and acts on neighboring cells

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4
Q

Autocrine

A

Acts on the cell that is producing it

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5
Q

What are Hormones

A

Hormones are chemical messengers that are carried via the blood to distant target cells.

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6
Q

What are types of hormones

A

Hormones include water-soluble proteins/glycoproteins and lipid soluble steroid hormones.

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7
Q

Water-soluble hormones

A

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

meaning, they bind with cell membrane receptors and then activate the second messenger

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8
Q

How do Lipid soluble steroid hormones bind to cell membrane

A

Diffuse across the cell membrane, bind to nuclear receptors, and activate the transcription of DNA.

Meaning, they cross the cell membrane and bind with cytoplasmic or nuclear receptors and then activate DNA Transcription

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9
Q

Major Endocrine Organs

A

Organs whose sole function is to synthesize and secrete hormones

Pituitary, Thyroid, Adrenal

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10
Q

Endocrine Components within other Organs

A

Endocrine cells are distributed within organs which also have non-endocrine functions such as:

Islets of langerhans in the pancreas
Leydig cells in the testis
Granulosa and theca cell in the ovary
JG cells in the kidney

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11
Q

Diffuse Endocrine cells

A

These endocrine cells are distributed individually or in small groups within epithelium of the digestive system

Argentaffin cells

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12
Q

Pituitary gland

A

A major endocrine organ that is connected with the hypothalamus

Ductless gland

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13
Q

Two subdivisions of the Pituitary gland

A

Adenohypophysis (anterior pituitary)
Neurohypophysis (posterior pituitary)

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14
Q

Adenohypophysis (anterior pituitary)

A

pars distalis
pars tuberalis,
and pars intermedia

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15
Q

Neurohypophysis (posterior pituitary)

A

median eminence,
infundibulum,
and pars nervosa.

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16
Q

Species differences in gross positions of different parts of the pituitary

A

For humans, the classical division of the pituitary gland into anterior lobe and posterior lobe is true only in humans and to some extent in the bovine and porcine

In equine,felines, canines, the pituitary gland is compressed dorso-ventrally

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17
Q

Development of the Adenohypophysis of the pituitary gland

A

Develops from an ectodermal derivative of the stomodeum which is called the Rathke’s pouch

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18
Q

Development of the Neurohypophysis of the pituitary gland

A

Develops from an evagination of the diencephalons

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19
Q

What is the Pars Distalis

A

Part of the Adenohypophysis(anterior lobe) of the pituitary gland

Cells arranged in irregular cords that lie adjacent to sinusoids

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20
Q

What are the two cell types of the Pars Distalis

A

Chromophils
Chromophobes

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21
Q

What are Chromophils

A

Cytoplasm stained cells in the pars distalis:
Acidophils
Basophils

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22
Q

Acidophils

A

Are PAS -ve
Secrets protein hormones
Somatotroph
Lactotroph/ Mammotroph

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23
Q

Somatotrophs

A

Makes up 50% of chromophils
Secretes protein hormone GH (Growth Hormone)

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24
Q

Mammotrophs/ Lactotrophs

A

Makes up 20% of chromophils
Secretes the protein hormone Prolactin

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25
Q

Basophils

A

PAS +ve
Secretes glycoprotein hormones
Gonadotroph
Corticotroph
Thyrotroph

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26
Q

Thyrotrophs

A

Makes up 5% of chromophils
Secretes the glycoprotein TSH (Thyroid Stimulating Hormone)

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27
Q

Gonadotrophs

A

Makes up 5% of chromophils
Secretes the glycoproteins LH ( Luteinizing Hormone) and FSH (Follicle stimulating Hormone)

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28
Q

Corticotrophs

A

Makes up 20% of chromophils
Secretes the glycoprotein ACTH

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29
Q

Chromophobes

A

Stem cells for chromophils
Their cytoplasm is unstained

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30
Q

What is Pars Intermedia

A

Part of the adenohypophysis of the pituitary gland
Contains colloid-containing cysts which represents remnants of the Rathke’s Pouch

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31
Q

What types of cells are in Pars intermedia

A

Melanotrophs
Corticotrophs

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32
Q

Melanotrophs

A

Secretes MSH (Melanin Stimulating Hormone)

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33
Q

Clinical significance of Corticotrophs in the Pars Intermedia

A

These cells can hypertrophy or under go hyperplasia especially i the horse, leading to excessive secretion of ACTH, which in turn, causes excessive secretion of cortisol from the adrenal cortex

LEADS TO CUSHING’S SYNDROME

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34
Q

What is the Pars Nervosa of the pituitary gland

A

Part of the Neurohypophysis (Posterior lobe).
Contains the unmyelinated axons of neurosecretory cells whose cell bodies located in the supraoptic and paraventricular nuclei of the hypothalamus.
Besides unmyelinated axons, pituicytes (glia-like cells) are present in pars nervosa.

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35
Q

What hormone does the Supraoptic Nuclei secrete

A

Vasopressin (ADH)
Target site:

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36
Q

What hormone does the Paraventricular Nuclei secrete

A

Oxytocin
Target site:Mammary Gland, Uterus

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37
Q

Where are the hormones that are secreted by the supraoptic and paraventricular nuclei transported to

A

Are transported to the distal ends of hypothalamo-hypophyseal axons and is the site where these hormones are stored in accumulations known as Herring bodies.

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38
Q

Hypothalamic hypophyseal portal system

A

Primary capillary plexus comes off the superior hypophyseal artery, is in the median eminence where stored hypothalamic neurosecretory hormones (releasing and inhibitory) enter the blood; is drained by hypophyseal portal veins, which enter the pars distalis and empty into a secondary capillary plexus that consists of sinusoids surrounding cells of the pars distalis

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39
Q

Hormones of the pars distalis

A

Somatotropin (GH), prolactin, ACTH, FSH, LH, and TSH.

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40
Q

Hormones of the pars nervosa

A

Oxytocin, vasopressin (ADH).
Note: these hormones are only stored here but are secreted by SO and PV nuclei of the hypothalamus.

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41
Q

Hormones of the hypothalamus entering the pars distalis

A

GH-RH, GnRH, CRH, TRH, GH-IH (somatostatin), and PIH (dopamine).

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42
Q

Clinical Considerations of the Pituitary Gland

A

Pituitary tumors are not uncommon, are treated by surgical removal.

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43
Q

Thyroid Gland

A

A major endocrine organ that consists of two lobes connected by the isthmus

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44
Q

Development of the Thyroid Gland

A

Develop from the endoderm between the first and second pharyngeal pouches

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45
Q

What is the Thyroid Gland made/ consist of

A

Consist of follicles, spherical structures filled with colloid (iodinated thyroglobulin glycoproteins, precursor of thyroxin),

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46
Q

The follicle of the Thyroid is lined by what type of epithelium

A

Simple Cuboidal Epithelium
(lined by follicular cells (98%) and parafollicular cells (2%, develop from the ultimobranchial body), and are surrounded by fenestrated capillaries)

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47
Q

What are follicular cells of the thyroid

A

Cuboidal in shape but become columnar when stimulated by TSH and squamous when inactive.

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48
Q

What are follicular cells involved in

A

Cells are involved in the synthesis and release of thyroid hormones, T4 and T3, the former is abundant, but the latter is more potent.

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49
Q

Steps involved in the synthesis and release of thyroid hormone:

A

1) synthesis of thyroglobulin

2) uptake of iodide

3) oxidation of iodide

4) tyrosine iodination

5) resorption of thyroglobulin and release of T4 and T3 into the circulation.

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50
Q

Step 1 of thyroid hormone synthesis: Synthesis of Thyroglobulin

A
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51
Q

Step 2 of thyroid hormone synthesis: Uptake of iodide

A
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52
Q

Step 3 of thyroid hormone synthesis:

A
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53
Q

Step 4 of thyroid hormone synthesis:

A
54
Q

Step 5 Step 1 of thyroid hormone synthesis

A
55
Q

Physiological effects of T4 and T3

A

Increase the basal metabolic rate and thus promote heat production, have broad effects on gene expression and induction of protein synthesis.

56
Q

What are parafollicular cells

A

Surround follicular cells, found in small clusters between the follicular cells and basal lamina.

57
Q

What do parafollicular cells secrete

A

Synthesize and secrete calcitonin (thyrocalcitonin), a polypeptide hormone which is released in response to high blood calcium level (hypercalcemia)

58
Q

What is the function of Calcitonin

A

Function is to lower blood calcium level by inhibiting osteoclastic activity.

59
Q

Clinical significances of the thyroid

A

1) Graves’ disease

2) Simple goiter

Myxedema and cretinism (hypothyroidism)

60
Q

Grave’s Disease

A

Characterized by exophthalmos (exophthalmic goiter), hyperexcitability (nervous symptoms), enlargement of thyroid gland, excessive production of thyroxine, decreased level of TSH.

Caused by the binding of autoimmune IgG antibodies to TSH receptors.

61
Q

Simple Goiter

A

Enlargement of the thyroid gland caused by insufficient iodine in the diet, treated by dietary iodine.

Myxedema and cretinism (hypothyroidism).

62
Q

Where is the Parathyroid Located

A

Located on the caudal surface of the thyroid gland, as well as embedded in its capsule; develop from ventral diverticula of third and fourth pharyngeal pouches.

63
Q

What are the two types of cells in the Parathyroid

A

Chief Cells
Oxyphil

64
Q

Chief Cells

A

Present in all species and numerous

65
Q

What do Chief Cell secrete

A

Secrete parathyroid hormone

66
Q

Function of Parathyroid hormone

A

Raise blood calcium levels by stimulating osteoclastic activity and by increasing reabsorption of calcium and decreasing reabsorption of phosphates at the proximal tubules of the kidney. Parathyroid hormone is antagonistic to calcitonin hormone.

67
Q

Oxyphil compared to Chief cells

A

Relatively larger in size, few, present in horse and large ruminants but rare in other species.

68
Q

Clinical significance of parathyroid

A

Hyperparathyroidism

69
Q

Where is the Adrenal Gland

A

Located at the anterior pole of each kidney

70
Q

The development of the Adrenal gland

A

Derived from two embryonic sources: cortex from the mesoderm and medulla from the ectodermal neural crest cells.

71
Q

Where is the medulla of the Adrenal Gland present in animals

A

The medulla is present as a separate organ in lower vertebrates, randomly mixed with cortical tissue in birds, and centrally located in mammals.

72
Q

How is the Adrenal cortex divided for mammals

A

Cortex in mammals is divided into three regions:
zona glomerulosa (ZG)
zona fasciculata (ZF)
zona reticularis (ZR).

73
Q

How are the parenchymal cells of the Adrenal Gland arranged

A

Parenchymal cells are arranged in longitudinal cords/columns, which are surrounded by longitudinally oriented sinusoidal capillaries

74
Q

What do the parenchymal cells of the adrenal gland secrete

A

All cells secrete steroid hormones.

75
Q

How are adrenal cells characterized

A

Hence, these cells are characterized by mitochondria with tubular cristae, abundant SER, and lipid droplets.

76
Q

How are steroid hormones different from protein/glycoprotein hormones

A

Steroid hormones are not stored, but are secreted as soon as they are synthesized

Protein/glycoprotein hormones are stored intracellularly before being secreted into the blood

77
Q

Where is the Zona glomerulosa (ZG) of the Adrenal Gland located

A

Is located just beneath the capsule

78
Q

How the cells in the Zona glomerulosa (ZG) arranged in horses, carnivores, and pigs

A

Cells are arranged in the form of arches

79
Q

How the cells in the Zona glomerulosa (ZG) arranged in ruminants and man

A

Cells are arranged in the form of clusters

80
Q

What do the cells in Zona glomerulosa (ZG) secrete

A

Secretes mineralocorticoids (aldosterone), regulates electrolyte balance.

81
Q

How are the hormones in the Zona glomerulosa (ZG) stimulated

A

Angiotensin II (mainly) and ACTH (limited control).

82
Q

What conditions stimulate aldosterone secretion directly

A

Hypovolemia, hyponatremia, and/or hyperkalemia can stimulate aldosterone secretion directly and/or via the renin-angiotensin system

83
Q

A tumor of corticotrophs will have a minimal effect on aldosterone secretion; explain why?

A
84
Q

What is the Zona Fasciculata (ZF)

A

Is the largest region of the adrenal cortex

Constitutes up to 80% of its volume, can be divided into outer (cells more vacuolated and are referred to as spongiocytes) and inner fasciculata; secretes glucocorticoids (cortisol and corticosterone);

85
Q

How is the Zona Fasciculata Divided

A

Can be divided into outer (cells more vacuolated and are referred to as spongiocytes)
and inner fasciculata

86
Q

What do the cells in the Zona Fasciculata secrete

A

Secretes glucocorticoids (cortisol and corticosterone)

87
Q

Function of Glucocorticoids

A

secretes glucocorticoids (cortisol and corticosterone); regulate carbohydrate metabolism by promoting gluconeogenesis; are useful in treating stress, autoimmune diseases, chronic inflammation, and in promoting acceptance of heterologous grafts; secretion is stimulated by ACTH

88
Q

Side Effects of long term Glucocorticoid therapy

A

lymphopenia, eosinopenia, and neutrophilia.

89
Q

Zona Reticularis (ZR)

A

Is the deepest layer of the cortex, constitutes only 7% of its total volume

90
Q

What do the cells in the Zona Reticularis (ZR) of the Adrenal cortex secrete

A

Secretes weak androgens (dehydroepiandrosterone, and some androstenedione) and small amounts of glucocorticoids

91
Q

How is the hormone production stimulated in the ZR

A

hormone production is stimulated by ACTH.

Adrenal androgens play an important role in the onset of puberty in humans, especially in the growth of pubic and axillary hairs.

92
Q

The medulla of the Adrenal gland contains

A

Contains chromaffin cells, which are modified postganglionic sympathetic neurons and are innervated by the preganglionic sympathetic (cholinergic) fibers

; physiological effects include “fight-or-flight response”, increased blood pressure, faster heart rate, faster breathing rate, and elevated blood glucose level.

93
Q

What do Chromaffin cells secrete

A

Secrete mostly epinephrine and some norepinephrine (different cell types)

physiological effects include “fight-or-flight response”, increased blood pressure, faster heart rate, faster breathing rate, and elevated blood glucose level

94
Q

Difference between epinehrine cells and norepiniehrine cells histologicially (slide 26)

A
95
Q

What mediates Catecholamine release

A

Catecholamine release is under nervous control, mediated by the preganglionic sympathetic fibers

96
Q

Blood Supply to the Adrenal Gland

A

Cortical blood capillaries are fenestrated sinusoids;

medullary artery passes through the cortex and breaks into capillaries in the medulla;

both cortical sinusoids and medullary capillaries drain into medullary veins;

the latter join the suprarenal vein.

97
Q

Clinical significance of adrenal gland

A

Cushing’s syndrome, characterized by hypersecretion of glucocorticoids: Addison’s disease, characterized by hyposecretion of adrenocortical hormones, is life threatening.

98
Q

What is Addison’s disease

A

Characterized by hyposecretion of adrenocortical hormones, is life threatening.

99
Q

Pineal Gland

A

Known as pineal body or epiphysis, projects from the roof of the diencephalon

100
Q

What is the Pineal Gland Composed of

A

Composed of pinealocytes and neuroglia cells

101
Q

What do pinealocytes secrete

A

Pinealocytes secrete melatonin

102
Q

What is melatonin responsible for

A

Responsible for seasonal cyclicity observed in horses (long-day breeder) and sheep and goats (short-day breeder)

103
Q

Argentaffin Cell secretions

A

Gastrin
CCK
Somatostatin
VIP

104
Q

Where is Gastrin secreted

A

By Argentaffin cells in the:
Duodenum
Jejunum

105
Q

Where is Secretin

A

By Argentaffin cells in the:
Duodenum
Jejunum
Ileum

106
Q

Where is Cholecystokinin (CCK) secreted

A

By Argentaffin cells in the:
Duodenum
Jejunum
Ileum

107
Q

Where is Somatostatin secreted

A

By Argentaffin cells from the:
Stomach to the colon

108
Q

Where is Vasoactive Intestinal polypeptide (VIP) secreted

A

By Argentaffin cells from the:
Stomach to the colon

109
Q

Types of Islet of Langerhans in the Pancreas

A

Beta Cells of Islets of Langerhans: 70%
Alpha cells of Islets of Langerhans:20%
Delta Cells of Islets of Langerhans:5%

110
Q

What do Beta Cells of Islets of Langerhans secrete

A

Insulin

111
Q

What do Alpha cells of Islets of Langerhans secrete

A

Glucagon

112
Q

What do Delta Cells of Islets of Langerhans secrete

A

Somatostatin

113
Q

What do the JG cells in the Kidney Secrete

A

JG cells( Juxtaglomerular cells) secrete Renin

114
Q

1,25 dihydroxycholecalciferols (metabolite of Vitamin D) Erythropoietin

A

It is secreted in the Kidney but what cell is not known

115
Q

What are JG cells

A

Are modified smooth muscle cells of the afferent arteriole and lie adjacent to macula densa

116
Q

When do JG cells secrete renin

A

Jg cells secrete renin in response to low blood pressure or hypovolemia or hyponatremia and help in blood pressure regulation

117
Q

When is Erythropoietin secreted

A

Is secreted in response to a decreased oxygen supply to the kidney

118
Q

What cells in the testis synthesize and secrete hormones

A

Leydig Cells
Sertoli Cells

119
Q

What do Leydig cells secrete

A

Testosterone

120
Q

What do Sertoli cells secrete

A

Estrogen
Inhibin

121
Q

What cells in the Ovary synthesize and secrete Hormones

A

Theca interna Cells
Granulosa Cells
Luteal Cells

122
Q

What do Theca Interna Cells secrete

A

Theca Interna cells have LH receptors and secrete Testosterone

123
Q

What do Granulosa Cells secrete

A

Estrogen
Inhibin

124
Q

Relationship between Granulosa Cells and Theca interna Cells

A

Granulosa cells have FSH receptors which convert Testosterone into estrogen.

The estrogen is released into the antrum and the blood

125
Q

What do Luteal Cells Secrete

A

Progesterone

126
Q

What structures synthesize and secrete hormones in the Placenta

A

Endometrial cups (equine)
Chorionic Epithelium

127
Q

What are Endometrial cups

A

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

128
Q

What do chorionic epithelium in humans secrete

A

hCG(LH-like)

129
Q

What do chorionic epithelium secrete

A

Progesterone
estrogen

Note: Placenta of all species secrete these

130
Q

What in the uterus secretes hormones

A

Endometrium

131
Q

What does the Endometrium do if pregnancy does not occur

A

Secretes prostaglandin F2-Alpha (PGF2-alpha)

which causes lysis of the corpus luteum, and thus the beginning of a new estrous cycle

132
Q

What hormones do nerve synapses/ terminals secrete

A

Acetylcholine, norepinephrine

Microanatomy 2 (6 decks)

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