Calcium balance Flashcards
What are the main players that control Ca flux
Calcitonin
Vitamin D3
Parathyroid Hormone,
Parathyroid-hormine related protein (PTHrP)
What are the key organs responsible for Calcium regulation
The parathyroid gland
The intestines
The kidneys
The bones
The skin
What form is Calcium found in bone
Hydroxyapatite
______ amount of calcium is released from bone
A very little
_____ is the major reservoir of Calcium in the body
Bones
Which type of bone has the most calcium turnover
Trabecular bone
What are the three types of bone cells
Osteoblasts
Osteoclasts
And Osteocytes
What is the primary composition of inorganic bone
Hydroxyapatite
What is the major composition of organic bone
Collagen
WHat is the osteoid made of
an organic matric made of collagen fibrils
What is responsible for synthesizing collagen to make up the osteon
Osteoblasts
What are the two mechanism for bone resorption
Osteocytic osteolysis
Osteoclasstic resorption
What is osteocytic osteolysis
The transfer of calcium from the canaliculi to the extracellular matrix
What cell is responsible for osteocytic osteolysis
Osteocytes
Between the two mechanisms of Calcium resorption which is the quickest
Osteocytic osteolysis
Apart from the time taken what a major difference between osteocytic osteolysis and osteoclastic resorption
Osteocystic Osteolysis does not lead to a decrease in bone mass
What cell is responsible Osteoclastic resorption
Osteoclasts
What is the name of reduced bone density and mass
Osteoporosis
How is the Parathyroid hormone related to calcium levels
Increasing it by increasing to bone resorption
How is Calcitonin relate Ca levels
It decreases it by inhibiting resorption and increasing bone formation
How is vitamin D related to Ca levels
Vitamin D leads to increased absorption of Ca from the Gut, increasing Bone resorption and Kidney resorption, henced inceased Ca
How is Vitamin D synthesized and in what form
Vitamin D is synthesized in the skin in an inactive form
How is Vitamin D activated
it is first hydroxylated in the liver and secondly in the Kidney to form 1,25-dihydroxy Vitamin D
What enzyme is the main point of regulation of Vitamin D synthesis
1α-hydroxylase
______ inhibit 1α- hydroxylase
Phosphates
_______ stimulates 1α- hydroxylase
Parathyroid Hormone
How does Vitamin D increase Ca absorption in the intestine
It binds to steroid receptors which increase the transcriptionn of certain proteins including Calcium Binding Proteins(CaBP)
This allow further absorption of Ca against a high Ca gradient from initial absorption
How does vitamin D cause Bone resorption
They act on osteoblasts which then signal osteoclasts for resorption
What is the difference between primary and secondary hyperthyroidism
Primary has to do with over production by the parathyroid gland, where as secondory has to do with lack of feedback inition of the parathyroid gland
What are the main causes of the Secondary hyperparathyroidism
Renal failure lading to oversecretion of Ca
Decreased receptors for Ca and Vit D3
Increased phosphur leading to in uremia induced parathyroid gland hyperplasia
