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Histology > Thyroid, Parathyroid and Adrenal Gland > Flashcards

Thyroid, Parathyroid and Adrenal Gland Flashcards

1
Q

Primary Endocrine Glands

A
  • Pineal
  • Pituitary
  • Thyroid
  • Parathyroid
  • Thymus
  • Adrenals
  • Islets of Langerhans
  • Ovaries
  • Testes
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2
Q

Secondary Endocrine Organs

A
  • Heart
  • Liver
  • kidneys
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3
Q

Effects of hypophyseal hormones on Target Organs

A

PIC

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4
Q

How many lobes does Throid Gland Have?

A

2

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5
Q

Thyroid Gland Development

A

The foramen cecum of the tongue marks where the thyroid diverticulum originates at week 4 and it is formed by week 7(PIC)

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6
Q

What is the functional and structural unit of the thyroid gland?

A

Thyroid Follicle

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7
Q

____ Is the only endocrine gland that stores the hormone it produces in large quantities extracellular in the colloid of the follicles

A

The Thyroid

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8
Q

Follicular Cells purpose

A

In charge of producing thryoid hormone- typical secretory cells that contain microvilli and RER

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9
Q

Parafollicular cells (C Cells) Produce…

A

Produce Calcitonin

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10
Q

Where do C Cells derive from and where can they be found?

A

Derived from NEURAL CREST CELLS and can be found within the FOLLICULAR EPITHELIUM or as clusters between follicles

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11
Q

Is Throid highly vascularized?

A

YES, commonly in secretion organs

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12
Q

T3

A

Triiodothyronine (thyroid hormones)–more active than T4

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13
Q

T4

A

Thyrozine (thyroid hormones)–Less Active than T3

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14
Q

T3 and T4

A
  • Produces, stored, absorbed, and secreted by FOLLICULAR CELLS
  • Increase basal metabolic rate (mitochondrial number, their cristae density and activity)-Cause OxPhos
  • Influence body growth and nervous system development at fetal state
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15
Q

Calcitonin

A
  • Produced and secreted by PARAFOLLICULAR (C CELLS)
  • Induced by increases in blood calcium levels
  • Lowers blood calcium by inhibiting bone resorption (osteoclasts)
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16
Q

What happens when blood has too much calcium in blood?

A

Osteoclasts destroy bone locally and adjust calcium availability

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17
Q

What is needed to produce T3 and T4

A

Follicular cells have IODIDE PUMPS (transporters) that concentrate iodide in the thyroid gland

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18
Q

Radioactive Iodine Scan

A

After injection of radioactive iodide, 40% is in thyroid gland within 10 MINS

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19
Q

First Step of Synthesis of Thyroid Hormones

A

Synthesis of THYROGLOBULIN (660 kDA) and secretion into the follicles

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20
Q

Second Step of Synthesis of Thyroid Hormones

A

Uptake of circulating iodide by follicular cells via Na/I symporter in their basolateral membrane

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21
Q

Third Step of Synthesis of Thyroid Hormones

A

Oxidation of iodine by THYROID PEROXIDASE and transport of oxidized iodine into the follicle cavity by PENDRIN, an anion transporter

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22
Q

Fourth Step of Synthesis of Thyroid Hormones

A

IODINATION OF TYROSINE residues of thyroglobulin by thyroid peroxidase generates T4, T3, fiiodotyrosine and monoiodotyrosine

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23
Q

Thyroid Feedback Loop- How Thyroid is regulated

A

By hypothalamus- which stimulates pituitary gland

  • Releasing TSH
  • T3 and T4 are released in bloodstream and goes to target cells
  • Negative Feedback loop tells hypothalamus to stop releasing hormones

PIC

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24
Q

Thyroid Hormone Secretion First step

A

upon stimulation by thyrotropin, follicular cells take up colloid by endocytosis

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25
Thyroid Hormone Secretion second step
endocytic vesicles are digested by lysosomal enzymes
26
Thyroid Hormone Secretion third step
Proteases cleave the bonds between iodinated tyrosine residues and the thyroglobulin molecule
27
Thyroid Hormone Secretion fourth step
T4 and T3 are liberated to the cytoplasm and secreted basally into the blood
28
Thyroid Hormone Secretion fifth step
Di- and monoiodotyrosines are NOT secreted; their iodine is recycles after cleavage by iodine halogenase
29
Thyroid Hormone Secretion sixth step
T4 is most abundant (90%) but most hormone activity is attributed to T3
30
Throid Gland-Resorption Vesicles- The thyroglobulin (precursor of active hormones) in the colloid is taken back into the follicular cells via...
Pinocytosis
31
Variation in Follicular Activity: | Hyperactive Follicle, Normal Follicle, Hypoactive Follicle
Hyperactive Follicle-Columnar type epithelial Normal Follicle-Cuboidal Epithelium Hypoactive Follicle- Very little colloid use- almost squamous epithelium
32
Goiter (NEED TO KNOW??)
Thyroid gland disorder- referring noly to an enlarged thyroid (proliferation problem)
33
Hyperthyroidism- Graves disease (NEED TO KNOW??)
involves autouimmune Ab which binds to the TSH receptor of the follicular cells.- Ab binding activates the receptor, thereby stimulating thyroid activity
34
Cretinism (NEED TO KNOW??)
Congenital hypothyroidism leads to stunted growth and mental retardation without promt postnatal treament
35
Parathyroid glands derive from...
Parapharyngeal puches
36
Where can Parathyroid glands appear?
in the mediastinum, next to the thymus which derives from the same pouches
37
Parathyroid glands are bounded by...
A connective tissue capsule that send branching septa towards the inside
38
Chief (principle) cells produce Parathyroid hormone (PTH) which promotes...
Bone Reabsorption. The Function of OXYPHIL cells is unknown
39
What are certain histological characteristics of adrenal cortex??
Cell cords
40
Eosinophilia of oxyphil cells is attributable to...
The abundant mitochondria
41
in the bone, which cells have PTH receptors?
Osteoblasts
42
What promotes absorption of calcified bone matrix and the release of calcium to the blood?
PTH binding signals the secretion of osteoclast-stimulating factor, which increases the number and activity of osteoclasts
43
Hyperparathyroidism (NEED TO KNOW??)
Pathological deposits of calcium in organs such as kidneys and arteries. Increased numbers of osteoclasts- multiple bone cavities- OSTEITIS FIBROSA CYSTICS
44
Parathryoid Neoplasia
A functional tumor of the parathyroid gland will lead to excessive levels of PTH
45
Hypoparathyroidism
Bones become dense and more mineralized. Spastic contractions of skeletal muscles plusgeneralizes convusions-TETANY
46
Suprarenal (Adrenal Glands) loaction
Paired organs located near SUPERIOR poles of they kidneys.. Embedded in aipose tissue -flat, half moon shape
47
Cortex of Adrenal Cortex-Color, Location, Development
Yellowish, located in the periphery | Develops from the CELOMIC EPITHELIUM aka. mesothelium derived from MESODERM
48
Medulla of Adrenal Cortex-Color, Location, Development
Red/brown- located centrally | Develops from NEURAL CREST CELLS derived from ECTODERM
49
3 concentric layers of AC with not defined limits
- Zona Glomerulosa-15% under the capsule - Zona Fasciculata-65% in the middle - Zona Reticularis-7% inside
50
Adrenal Gland Vascularization
Dual Blood Supply: - Arterial Blood (via medullary arteries) - Venous Blood (via Cortical Veins)
51
Zona Glomerulosa
Columnar or pyramidal cells that secrete ALDOSTERONE (minteralocorticoid) which acts to stimulate Na+ reabsoprtion in the distal convulated tubules of the kidney.
52
What stimulates Aldosterone Secretion
Angiotensin II
53
Zona Fasciculata
Typically arranged in cords -Secrete predominantly HYDROCORTISONE (cortisol), and suppress the immune system and aid in fat protein and carbohydrate metabolism
54
What is Cortisol
A glucocorticoid that functions to increase blood sugar levels through gluconeogensis
55
Zona Reticulari
Smaller, arranged in irregular cords- secrete DHEA ( weak androgen) which is converted into testosterone somewhere else in body
56
Endocrine control of AC
PIC
57
Adrenal medullary cells are specialized...
Postganglion sympathetic neurons
58
Adrenal Medulla
polyhedral parenchymal cells arranged in cords or clusters that secrete epinephrine (80%) and norepinephrine (20%) in response to sympathetic stimuoation. Also secrete ATP chromogranins
59
Adrenal Medulla recieves a dual blood supply. Cortical arterioles, cappilarries and sinusoids first irrigate...
the cortex
60
Adrenal Medulla recieves a dual blood supply. Medullary Arterioles pass directly though...
the cortex
61
Adrenal Medulla Secretory
PIC
62
Fetal suprarenal galnds are ___ than in adults
10-20x larger (relative to body weight). Secrete sulfate conjugates of androgens that are converted at the placenta into active androgens and estrogens and enter maternal ciculations
63
Short Term stress response
heartbeat and blood pressure increase. Blood glucose level rises. muscles become energized Involving Epinephrine and Norepinephrine
64
Long term stress response
Glucotricoids- proteins and fat metabolsm instead of glucose breakdown. Reduction of inflammation; immune cells are SUPPRESSED Mineralcorticoids: sodium ions and water are reabsorbed by kidney. Blood volume and pressure increase (PPIC)
65
Disorders of Adrenal Function (NEED TO KNOW??)
PIC
66
Cushings Syndrome
Associated with excessive levels of glucocorticoid hormones
67
Conns Syndrome
Hyperaldosteronism (PIC)
68
Pheochromocytoma
Medullary tumors secrete large quantities of catecholamines, and cause hyperglycemia and elevation of blood pressure. (RARE but highly malignant)- Produce steroids
69
The 2 thyroid gland are held together by
Isthmus
70
At what week of development is the thyroid gland seen next to the Larnyx and not Foramen Cecum
7th Week
71
What week does the Thyroid Diverticulum begin to form by the tongue?
4th
72
What are thyroid gland follicles full of?
Colloid-Gelatin Substance
73
What organ is the only endocrine gland that stores the hormone it produces in large quantities extracellularly in the colloid of the follicles
The Thyroid
74
What part of the gland reacts with stress?
Cortical-- becomes hyperactive

Histology (23 decks)

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