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HRM > Pineal, Thyroid, and Parathyroid Histology > Flashcards

Pineal, Thyroid, and Parathyroid Histology Flashcards

1
Q

What is the small pine cone-shaped body (5-8 mm in humans)
Attached by stalk to roof of third ventricle between 2 hemispheres?

It has a Rich capillary plexus
Not separated by blood-brain barrier
it is Largest in first decade of life, does not grow throughout life

A

Pineal Gland

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2
Q

What cell types make up the pineal gland?

A

Pinealocytes
(95% of cells)

Glial cells (Interstitial cells)
Cannot identify using light microscopy
Astrocytes (supportive role) – similar to pituicytes of posterior pituitary

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3
Q

Pinealocytes produce what hormone and when?

A

Produce melatonin at night

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4
Q

What are the concretions of calcium phosphate & carbonate on carrier proteins that accumulate with age?

No known function
Radiological marker for the pineal gland
(displacement of pineal from midline is evidence of cerebral tumors)

A

Brain sand (corpora arenacea)

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5
Q

What is the pineal gland nerve supply?

A

Sympathetic nerve fibers

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6
Q

Post-ganglionic fibers from superior cervical ganglion
End on pinealocytes and
Release what?

A

epinephrine

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7
Q

Give the series of events that produce Melatonin during low light periods

A

Light/dark signals (photoreceptors) from the eye
suprachiasmatic nucleus (SCN)
paraventricular nuclei (PVN)
spinal cord
superior cervical ganglia
pineal gland
Suppresses gonadotrophin (FSH & LH) secretion via hypothalamus inhibition

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8
Q

Other pineal gland functions

A

Retards gonadal growth and function
(Melatonin inhibits hypothalamic GnRH
Inhibits FSH & LH in anterior pituitary)

Possibly alters emotional responses to changes in day length

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9
Q

In thyroid development, what gestational week does the Pharyngeal endoderm thickens and forms the thyroglossal duct and the
Ducts descends toward trachea and divides to form 2 lobes

A

4th gestational week

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10
Q

In thyroid development, what gestational week do Epithelial cells of fourth branchial pouch, ultimobranchial bodies, migrate toward thyroid gland, differentiate to parafollicular cells and scatter in lobes

A

7th gestational week

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11
Q

In thyroid development, what gestational week do Endodermal cells differentiate to follicular cells

A

9th gestational week

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12
Q

In thyroid development, what gestational week do Well developed follicles contain colloid in lumen

A

14th gestational week

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13
Q

What gland is on the Anterior neck adjacent to larynx and upper trachea
Two lateral lobes connected by isthmus
Connective tissue capsule
Follicles are functional unit
Fenestrated capillaries surround follicles

A

Thyroid gland

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14
Q

What are the 2 types of cells found in the thyroid gland

A 
Follicular cells (Principal cells)
Parafollicular cells (C-Cells)
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15
Q

What are the Structural units of thyroid?

A

Simple epithelium
(cuboidal, squamous, columnar)

Colloid contains thyroglobulin
(Gel-like, sometimes rippled)

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16
Q 
These thyroid cells ...
Apical ends of cells adjacent to colloid
have microvilli that extend into colloid
Basal ends of cells rest on basement membrane
Junctional complexes between cells
Slightly basophilic cytoplasm
Round nuclei, prominent nucleoli
Synthesize thyroid hormones
A

Follicular Cells

17
Q 
These thyroid cells ...
“Resting”
Producing basal levels of thyroglobulin
Low cuboidal to squamous
Few mitochondria; small Golgi
Some rough ER in base of cells
A

Inactive Follicular Cells

18
Q 
These Thyroid cells ...
Stimulated by TSH from pituitary
Columnar cells
Numerous mitochondria; enlarged Golgi
Increased rough ER
Lipid droplets and PAS-positive (polysaccharide) 
Colloid resorption by endocytosis
Apical lysosomes
Release T3, T4 on basal surface
A

Active Follicular Cells

19
Q

These thyroid cells …
Occur singly or in small groups
Between follicular cells and basement membrane (not on lumen)
Also within interfollicular connective tissue
Slightly stained in H&E stains
Neuroendocrine
Synthesize calcitonin

A

Parafollicular Cells (C-Cells)

20
Q

What are the actions of Calcitonin?

A

Lowers blood calcium by inhibiting bone resorption

Decreases osteoclast motility & numbers

Promotes excretion of calcium and phosphate from kidneys

21
Q

Colloid contains what?

A

thyroglobulin

22
Q

Oxidation to iodine at cell surface convers Iodide  Iodine via what enzyme?

A

thyroid peroxidase (TPO)

23
Q

Iodination of thyroglobulin occurs extracellularly at the
Tyrosine residues only

This process is Catalyzed by what enzymes on the follicular cell surface?

A

thyroid peroxidase (TPO)

24
Q

This process produces what hormone?

Pinocytosis of thyroglobulin in colloid –>
Fusion with lysosomes –>
Thyroglobulin proteolysis –>
Eventual formation and release of _________ to cytoplasm and diffusion to capillaries

A

T3 and T4

bound to carrier proteins

25
Q

What gland consists of Two pairs located on posterior surface of each lateral lobe of thyroid

  • Derived from pharyngeal endoderm
  • Connective tissue capsules separate it from thyroid
A

Parathyroid gland

26
Q

Parathyroid gland is made up of what 3 cell types?

A

Chief (Principal) cells
Oxyphil cells
Fat cells

27
Q

What parathyroid cell is responsible for Parathyroid hormone (PTH) production
which Regulates circulating calcium and phosphate levels

A

Chief (Principal) Cells

28
Q

What Peptide hormone is
Involved in regulation of calcium and phosphate levels

This Increases blood calcium

A

Parathyroid hormone

29
Q

What hormone stimulates increase in osteoclast numbers indirectly by stimulating osteoblasts to produce osteoclast stimulating factor (RANKL)

(Osteoclasts do not have PTH receptor, Osteoblasts have PTH receptor)

(Bone resorption increases blood calcium)

A

Parathyroid hormone

30
Q

These parathyroid cells …

Larger than chief cells
Smaller and darker-staining nuclei
Large eosinophilic cytoplasm that is finely granular
Many mitochondria
Unknown function(s)
A

Oxyphil Cells

HRM (8 decks)

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