Endocrine System (Troyer) Flashcards

1
Q

Location of the Pituitary Gland?

A

IN the sphenoid bone of the skull

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2
Q

Origin of the Pituitary Gland?

A

2 Parts

  • ectoderm from roof of oral cavity that grows upward as Rathke’s pouch =becomes anterior pituitary
  • neuroectoderm from diencephalon that grows downward = becomes posterior pituitary
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3
Q

What is a portal system?

A

series of veins that are interposed between two sets of capillaries

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4
Q

How does the hypothalamus “control” the adenohypophysis?

A
  • Releasing and Inhibiting factors (hormones) are synthesized by special secretory neurons in hypothalamus
  • Hormones are transported to and stored in axon terminals ending in the median eminence
  • After receiving appropriate stimulus, hormones are discharged into capillaries and travel into hypophyseal portal system to capillaries in pars distalis
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5
Q

What is the median eminence?

A

hypothalamic tissue extending into the pituitary (infundibular) stalk

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6
Q

Pars distalis

A

parenchyma of cords or clusters of cells associated with sinusoids

part of adenohypophysis

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7
Q

Where is the pars tuberalis?

A

forms collar around neural stalk of pituitary gland

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8
Q

What is secreted by the pars intermedia?

A
  • MSH - melanocyte stimulating hormone

- ACTH

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9
Q

What does CRH release?

A

ACTH or corticotropin

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10
Q

What does TRH release?

A

TSH or thyroid stimulating hormone

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11
Q

What does GnRH release?

A

gonadotropins

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12
Q

What does somatostatin do?

A

inhibits somatotropic hormone release

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13
Q

Origin of the Thyroid?

A

outgrowth from the floor of the buccal cavity

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14
Q

How many lobes are in the thymus?

A

two lobes that are usually connected by an isthmus

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15
Q

T/F: Dogs have an isthmus

A

False

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16
Q

Follicular Cells in the Thymus

A
  • cuboidal epithelium
  • microvilli on apical edge
  • held together by tight junctions
17
Q

Parafollicular Cells in the Thymus

A
  • found in isolated clusters beside the follicle
  • larger, paler cells than follicular cells
  • produce calcitonin which lowers serum calcium levels
18
Q

What does calcitonin do?

A

lowers serum calcium levels

19
Q

Function of the Thymus?

A
  • endocrine

- ‘storage’ phases of production (unusual among endocrine glands)

20
Q

Follicular Cells and storage phases

A

synthesize and secrete thyroglobulin

21
Q

Where is thyroglobulin stored?

A

extracellularly in lumen of follicle, where it is partially iodinated

22
Q

Follicular Cells and endocrine phase

A
  • stored thyroglobulin = taken up by follicular cells
  • broken down by lysosomal enzymes to active thyroid hormone
  • TH then released into blood
23
Q

What is T4?

A
  • thyroxine or tetraiodothyronine
  • prohormone = one iodine is removed to make T3
  • most abundant form
24
Q

What is T3?

A
  • triiodothyronine
  • active hormone
  • less abundant than T4
25
Where can T4 become T3?
- liver, kidney, and muscles | - deiodinase removes one iodine
26
What does T3 do?
- increases metabolic rate of target cells | - increases numer of mitochondria = hence mitochondrial respiration
27
Colloid
- made up of thyroglobulin, a glycoprotein - tyrosine amino acyl residues of thyroglobulin are iodinated - represents storage phase of secretion
28
Location of Parathyroid Glands
In or around thyroid gland external parathyroids = vary from cranial to thyroids to level of thoracic inlet internal parathyroids = embedded in, on, or near thyroid
29
Structure of Parathyroid Glands
- capsule of internal parathyroids is areolar CT of thyroid | - parenchyma: cords, clusters w/ numerous capillaries
30
What is the predominant cell type of the parathyroid glands? Are they subdivided in any way?
Chief cells Yes = dark and light chief cells Dark cells produce parathyroid hormone
31
In what species are oxyphil cells found? What is the function?
Found in humans, ox, and horses Exact function unknown
32
What is the function of parathyroid hormone (PTH)? How is this function carried out?
raise blood calcium levels increases osteoclast activity to tear down bone to release calcium
33
Origin and location of adrenal gland
``` cortex = from mesoderm medulla = from neural crest ``` Location: cranial pole of kidney
34
Structure of the Adrenal Glands
capsule around adrenal sends trabeculae into the parenchyma also fine reticular fibers within the parenchyma
35
Three regions of adrenal gland cortex
- zona glomerulosa - zona fasciculata - zona reticularis
36
What is produced in the zona glomerulosa of the adrenal cortex? What's the function? How is it stimulated?
Mineralocorticoids act on kidney to retain Na+ and water Mostly stimulated by angiotensin
37
What is produced in the zona fasciculata of the adrenal cortex? How is it stimulated?
glucocorticoids stimulated by ACTH
38
What is produced in the zona reticularis?
weak androgens
39
Secretions of the Pineal Gland?
- melatonin | - serotonin