[PF1] ENDOCRINE - Thyroid Gland

Thyroid Gland consists of ___ and ____

thyroid follicle, thyroid colloid

What is the functional unit of the thyroid gland?

Thyroid Follicle

What determines the type of lining epithelium in a thyroid follicle?

Its activity

What type of epithelium lines an active thyroid follicle?

Low columnar to cuboidal

What type of epithelium lines a hypoactive thyroid follicle?

Simple squamous

Can the thyroid gland become completely inactive?

No, only less active or hypoactive

What is the substance found inside the thyroid follicle?

Thyroid Colloid

What does the thyroid colloid contain?

Thyroglobulin

What is thyroglobulin a precursor of?

Thyroid hormones (T3 and T4)

What region of Adrenal gland thyroid gland may present some vacuolations or may appear retracted from the follicular cells

thyroid colloid

Where may some cells be found embedded in the thyroid?

Within the colloid

Which thyroid gland has tall columnar thyrocytes and scalloped colloid?

Active Thyroid Gland

What do tall columnar cells and scalloped colloid indicate?

Active synthesizing thyroid gland

Which thyroid gland has simple, fat, or cuboidal epithelial cells?

Inactive Thyroid Gland

What does an inactive thyroid gland contain in stored form?

Thyroglobulin (colloid)

The thyroid gland contains several blood vessels, how many for arteries to the thyroid

2

The thyroid gland contains several blood vessels, how many for veins to the thyroid

3

What are the cells lining the thyroid follicle called?

Follicular Cells / Thyrocytes

Which thyroid cells are smaller than C cells?

Follicular Cells / Thyrocytes

Which thyroid cells are darker stained than C cells?

Follicular Cells / Thyrocytes

Thyroid cells - derived from the 1st & 2nd pharyngeal pouch of foregut endoderm

Follicular Cells / Thyrocytes

What do follicular cells secrete?

T3 and T4

Thyroid cells Found in between the thyroid follicles (interfollicular)

Parafollicular cells

Which thyroid cells are larger than chief cells?

Parafollicular Cells

Which thyroid cells are pale-staining and may occur singly or in clumps?

Parafollicular Cells

Thyroid Cells derived from Neural crest cells (ectoderm)

Parafollicular cells

What hormone do parafollicular cells secrete?

Calcitonin

What hormone lowers blood calcium by inhibiting osteoclast activity

calcitonin

Parathyroid gland have ___appearance (fat-filled with nucleus pushed to the periphery)

signet ring

How many lobules formed in parathyroid gland

none

What gland is pale-staining, glandular, and very cellular

parathyroid gland

Embryonic origin of the superior parathyroid

4th pharyngeal pouch

Embryonic origin of the inferior parathyroid

3rd pharyngeal pouch

Parathyroid gland contains ___ cells

adipocytes/fat

What is the main cell type of the parathyroid gland?

Principal / Chief Cells

Which parathyroid cells are the most numerous?

Principal / Chief Cells

Which parathyroid cells have pale cytoplasm?

Principal / Chief Cells

Which parathyroid cells have a closely-packed, vesicular nucleus?

Principal / Chief Cells

Which parathyroid cells produce parathormone / parathyroid hormone (PTH)?

Principal / Chief Cells

Which hormone raises blood calcium levels?

Parathyroid hormone (PTH)

Which parathyroid cells are relatively larger than chief cells?

Oxyphil / Acidophilic Cells

Which parathyroid cells have a bigger acidophilic cytoplasm?

Oxyphil / Acidophilic Cells

Which parathyroid cells have a smaller, denser nucleus?

Oxyphil / Acidophilic Cells

Which parathyroid cells increase in number with age?

Oxyphil / Acidophilic Cells

Which parathyroid cells form small groups or may appear singly interspersed between the principal cells

Oxyphil / Acidophilic Cells

What increases osteoclast activity, causing elevation of blood calcium levels?

Parathyroid hormone (PTH)

What cells secrete parathyroid hormone (PTH)?

Chief cells

What is not affected by hormones from the pituitary gland?

Parathyroid gland

What does the activity of the parathyroid gland depend on?

Levels of calcium in the blood