W28/L5 Flashcards
(20 cards)
Which are the bone-forming cells?
Osteoblasts
Blasts: they build bone
What’s the most common calcium phosphate used in building bone?
Hydroxyapatite
What are the collagen-producing cells of the cartilage?
Chondrocytes
Which are the bone-resorbing cells?
Osteoclasts
Clasts: they chew up the bone
What are some characteristics of osteoclasts?
Large, mobile & multinucleate
What is PTH?
Parathyroid hormone
PTH is secreted in response to:
Decreased plasma Ca2+
What effect does PTH have in the bone?
Bone resorption by osteoclasts (indirect)
What effect does PTH have on the kidney?
Increase calcium reabsorption in the distal nephron
Decreased phosphate reabsorption
What effect does PTH have on the intestine?
Indirectly increases calcium & phosphate absorption vis Vit D activation
T/F: Osteoclasts have PTH receptors that make them start chewing up the bone.
False!
They don’t have any PTH receptors, so the activity is regulated by PTH-induced paracrines
From where is calcitonin released?
C cells of the thyroid
Calcitonin is secreted in response to ____ calcium
V. high
What is active Vit D3 aka?
Calcitriol
What things stimulate calcitriol release?
Drop in calcium
PTH (stimulates synthesis)
Prolactin in lactating women
What does bone demineralisation in children cause?
Rickets
What does bone demineralisation in adults cause?
Osteomalacia
How many parathyroid glands do we have?
4
What are the paracrines that signal foe osteoclast activation?
OPG
RANK-L
Why does PTH have opposite effects on Ca2+ and PO4 reabsorption in the kidney?
The combined concentrations of them has to be kept low to prevent precipitation of them into kidney stones
