parathyroid anatomy/physio

Question 1

Small nests of parathyroid cells in the neck, ____________, can result from developmental variation or from seeding after parathyroid surgery

Answer 1

parathyromatosis

Question 2

A _____________ in plasma Ca++ is sensed by the calcium sensing receptors in
the Chief cells of the parathyroid gland and leads to inaction of
receptor signaling, but an ____________ in PTH secretion

Answer 2

A decline in plasma Ca++ is sensed by the calcium sensing receptors in
the Chief cells of the parathyroid gland and leads to inaction of
receptor signaling, but an increase in PTH secretion

Question 3

PTH signals through a G protein coupled receptor to stimulate bone
reabsorption indirectly by stimulating ___________ and __________ production from
osteoblasts.

Answer 3

M-CSF and RANKL

Question 4

In the kidney, PTH stimulates Ca++ __________, but phosphate __________.
It also stimulates vitamin D activation in the kidney.

Answer 4

In the kidney, PTH stimulates Ca++ reuptake, but phosphate excretion.
It also stimulates vitamin D activation in the kidney.

Question 5

The active form of vitamin D (1,25 Vitamin D3 or calcitriol) is produced
from vitamin D2 or D3 by the sequential action of 25 alpha hydroxylase
in the ______ and 1-alpha hydroxylase in the ___________.

Answer 5

The active form of vitamin D (1,25 Vitamin D3 or calcitriol) is produced
from vitamin D2 or D3 by the sequential action of 25 alpha hydroxylase
in the liver and 1-alpha hydroxylase in the kidney.

Question 6

Activated vitamin D acts through a steroid family receptor to stimulate
calcium and phosphate ___________ in the intestinal tract and calcium
__________ in the kidney.

Answer 6

Activated vitamin D acts through a steroid family receptor to stimulate
calcium and phosphate uptake in the intestinal tract and calcium
reuptake in the kidney.

Question 7

Calcitonin has actions opposite to that of _____, but its significance to
normal calcium physiology in humans is unclear.

Answer 7

PTH

Question 8

FGF-23 is made in ___________ and causes phosphate secretion and loss through the kidney. Mutations may cause autosomal dominant ___________________

Answer 8

FGF-23 is made in osteocytes and causes phosphate secretion and loss through the kidney. Mutations may cause autosomal dominant hypophosphatemic rickets.

Question 9

upper pair pf parathyroids descend with thyroid from _____ pharyngeal pouch and lower pair from _____ pharyngeal pouch with thymus

Answer 9

upper pair pf parathyroids descend with thyroid from pharyngeal pouch and lower pair from 3rd pouch with thymus

Question 10

type of bone?

  - found in the interior of bone
  - made of spicules or plates
  - major site of bone remodeling

Answer 10

trabecular (spongy) bone 20%

Question 11

type of bone?

forms the outer layer
Dense bone arranged in cylindrical osteons
cells are osteocytes that are interconnected by cellular processes that permit the transfer of nutrients and Ca++ to each other and to surface

Answer 11

cortical bone 80%

Question 12

Osteoblasts: promote bone formation by secreting osteoid, a complex matrix of proteins that includes:
(3)

Answer 12

1. type I collagen
2. osteocalcin
3. osteonectin

Question 13

binds to hydroxylapatite and collagen fibers

Answer 13

Osteonectin:

Question 14

binds Ca++ and hydroxylapatite, the crystalline mineral of bone [Ca10(PO4)6OH2]

Answer 14

Osteocalcin:

Question 15

assembles into fibers that are highly ordered in the osteoid and provide a scaffolding for the nucleation of bone minerals

Answer 15

Type I collagen:

Question 16

Osteoblasts _____________Ca++ and phosphate into the osteoid to promote crystal nucleation and growth.

Answer 16

exocytose

Question 17

what does FGF-23 regulates?

Answer 17

to decrease phosphate

Question 18

what does calcitonin regulates?

Answer 18

to decrease calcium

Question 19

what does PTH regulates?

Answer 19

increase calcium

Question 20

what does 1,25-(OH)2VitD3 regulates?

Answer 20

to increase calcium

Question 21

PTH acts on the (3)

Answer 21

1. kidney to reabsorb calcium
2. bone to reabsorb calcium
3. conversion of Vit D2 in the kidney

Question 22

Binding of Ca++ to a calcium sensing receptor (CaSR) on the chief cells activates PKC which_________ PTH secretion.

Answer 22

inhibits

A drop in plasma Ca++ results in dissociation of the ion from the CaSR and a decrease in PKC activity.

Question 23

PTH is synthesized as __________ containing 115 residues.

Answer 23

preproPTH

Question 24

PTH 1R is coupled to two G protein systems:

Answer 24

1: Gaq which activates PLC to produce DAG and IP3 to activate Ca++-dependent kinases
2: Gas which activates adenylyl cyclase to produce cAMP

Question 25

PTH acts on __________ and ___________ to increase Ca++ reabsorption. Reduces reabsorption of phosphate in both. In __________ it relocates the Na/Pi cotransporter from the luminal membrane to a pool of intracellular vesicles. Induces phosphaturia and lower plasma phosphate.

Answer 25

PTH acts on thick ascending loop of Henle and DCT cells to increase Ca++ reabsorption. Reduces reabsorption of phosphate in both PCT and DCT. In PCT it relocates the Na/Pi cotransporter from the luminal membrane to a pool of intracellular vesicles. Induces phosphaturia and lower plasma phosphate.

Question 26

PTH _________collagen synthesis by osteoblasts and ____________ production of bone matrix proteases.

Answer 26

PTH inhibits collagen synthesis by osteoblasts and promotes production of bone matrix proteases.

Question 27

is also produced by osteoblasts stimulated by estrogens- binds to RANKL receptor, blocking RANKL and protec-ting bone from resorption.

Answer 27

Osteoprotegerin (OPG)

Question 28

PTH promotes synthesis by activating ________in osteocytes which allows transfer of___________ from bone fluid to osteocytes which then transfer it via gap junctions to osteoblasts which pump it into the extracellular matrix on the bone surface: osteocytic osteolysis

Answer 28

PTH promotes synthesis by activating Ca++ channels in osteocytes which allows transfer of Ca++ from bone fluid to osteocytes which then transfer it via gap junctions to osteoblasts which pump it into the extracellular matrix on the bone surface: osteocytic osteolysis

Question 29

______________, produced by many different body tissues, has a marked amino acid homology with PTH on their amino termini. Both hormones bind to PTH 1R but _________ is associated with cartilage growth and development in utero and with Ca++ transport in the placenta.

Answer 29

PTHrp, parathyroid hormone related protein

Question 30

Vit D2 is obtained only from the diet largely from vegetables. (mushrooms, fish oil, tofu)
It differs from D3 only in the double bond between

Answer 30

carbons 22 and 23

Question 31

1,25 (OH)2 VitD3 binds to an ____________ and activates transcription of a variety of proteins.

Answer 31

intracellular receptor (VDR)

Question 32

Vit D acts on __________to increase Ca++ absorption

Answer 32

duodenum

Question 33

The rate-limiting step in phosphate absorption is uptake into the cell via the ______________
Vit D increases synthesis of this transport protein.
The mechanism of baso-lateral transport of phosphate is not known.

Answer 33

NaPi transporter.

Question 34

32 amino acid peptide made in parafollicular cells (aka C cells) in the thyroid gland and stored in secretory granules.
Secretion is triggered by increasing plasma Ca++

Answer 34

calcitonin

Question 35

FGF-23 Binds ____________ which causes phosphate secretion in kidney

Answer 35

alpha Klotho FGF Receptor

Question 36

Normal aging parathyroids show increasing _________ and accumulation of ______ cells

Answer 36

stromal fat and accumulation of oxyphil cells

Can be helpful for distinguishing normal from hyperplasia or neoplasia in small frozen sections