Thyroid & Parathyroid glands

Question 1

state where thyroid gland stores its hormones

Answer 1

in the lumen and NOT in the cells (intracellular)

Ie in the follicle

Question 2

2 lobes of the Thyroid gland are connected by____

Answer 2

Isthmus (septa)

Question 3

Describe capsule of thyroid gland

Answer 3

• Outer false capsule: made up of pretracheal fascia
• Inner true capsule: firmly adherent to the gland

Question 4

Follicular cells make up _ % of Thyroid follicle

Answer 4

98%

Question 5

Parafollicular (C) cells make up _ % of Thyroid follicle

Answer 5

2%

Question 6

changes in follicular cells during hyperthyroidism

Answer 6

from Cuboidal cells to columnar cells

Question 7

changes in follicular cells during hypothyroidism

Answer 7

from cuboidal cells to flat squamous cells

Question 8

type of cells that are follicular cells

Answer 8

Cuboidal cells

Question 9

LM of follicular cells

Answer 9

• basophilic cytoplasm
• central rounded nuclei

Question 10

EM of follicular cells

Answer 10

• Apex has short microvilli
• mitochondria
• rER
• golgi apperatus (supranuclear)
• ribosomes
• Apical secretory vesicles
• Lysosomes
• pinocytic vesicles

Question 11

function of Follicular cells

Answer 11

secrete Thyroid hormone (T3 & T4)

Question 12

site of parafollicular cells (C cells)

Answer 12

between follicular cells & basement membrane

Question 13

Function of Parafollicular cells

Answer 13

secrete thyrocalcitonin

It is part of APUD cells

Question 14

action of thyrocalcitonin

Answer 14

lowers blood Calcium

Question 15

Interfollicular tissue is formed by____

Answer 15

tangentially cut thyroid follicles in the lab

Question 16

Describe how thyroid hormones are synthesised

Answer 16

1. cells pick up amino acids & iodide from blood
2. synthesis of protein in rER
3. modification of ptn into glycoprotein by golgi appreratus (addition of carbohydrate) + packaging into secretory vesicles
4. Excocytosis of glycoprotein into lumen
5. Iodide is oxidised inside the cell by peroxidase into iodine
6. Iodine is exocytosed into lumen
7. in the lumen, Iodine & glycoprotein form Iodinated thyroglobulin & are stored as colloid
8. pinocytosis of colloid by the cell & lysosome & hydrolytic enzyme action forms T3 & T4 Hormones

Question 17

function of parathyroid cheif cell

Answer 17

secrete parathormone (parathyroid hormone)

Question 18

action of parathormone

Answer 18

increase Ca+2 in blood

Question 19

compare between size and number of chief cells & Oxyphil cells

Answer 19

• cheif cells: small & numerous
• Oxyphil cells: Large & less in number but increase with age

Question 20

compare betweem LM of Cheif cells & oxyphil cells

Answer 20

Cheif cells:
* polygonal cells
* central rounded nuclei
* Basophilic cytoplasm

Oxyphil cells:
* Oval/rounded cells
* eccentric nuclei
* acidophilic cytoplasm
* dark nucleus

Question 21

compare between granules of Cheif cells & Oxyphil cells

Answer 21

• cheif cells: fine secretory granules
• Oxyphil cells: Acidophilic granules (mitochondria packed together)

Question 22

Hyperparathyroidism manifestations & symptoms

Answer 22

• Hypercalcemia
• increase bone cavities (osteoclasts)
• bone more prone to fracture

Question 23

Hypoparathyroidism manifestations & symptoms

Answer 23

• Hypocalcemia
• bone becomes more dense & mineralised
• spastic contractions of muscles (tetanus)

Question 24

effect of low Iodine diet

Answer 24

• hindered thyroid hormone synthesis
• increased TSH (thyrotropin) secretion
• Compensatory increase in size of thyroid gland (Goiters)