Week 3 - Skeletal Systems 2 Flashcards
(18 cards)
What is appositional bone growth?
Growth in bone thickness through osteoblast activity in the periosteum forming new osteons.
What is interstitial bone growth?
Growth in bone length at the epiphyseal plate via endochondral ossification.
Where does appositional growth occur?
On the outer surface of bone; osteoblasts build externally, osteoclasts resorb internally.
Where does interstitial growth occur?
At the epiphyseal growth plate of long bones during childhood.
What do osteoblasts do in bone remodeling?
Form new bone by depositing bone matrix.
What do osteoclasts do in bone remodeling?
Break down bone by resorbing bone matrix.
What are the four phases of bone remodeling?
Activation, resorption, reversal, and formation.
What controls bone remodeling?
Hormones (PTH, calcitonin), mechanical stress, and calcium levels.
Why is mechanical stress important for bones?
It stimulates osteoblasts to strengthen bone and prevents resorption.
What happens to bone without stress or exercise?
Bone resorption exceeds formation, leading to bone weakening.
How is bone remodeling linked to calcium homeostasis?
Remodeling allows calcium to be released or stored in bone as needed.
What does calcitonin do to blood calcium levels?
Lowers blood calcium by inhibiting osteoclasts and increasing excretion.
What does parathyroid hormone (PTH) do to blood calcium levels?
Increases blood calcium by stimulating resorption and calcium absorption.
How does calcitonin affect the kidneys?
Increases calcium excretion in urine.
How does PTH affect the kidneys?
Increases calcium reabsorption, reducing calcium loss in urine.
How does calcitonin affect bone?
Inhibits resorption and promotes bone deposition.
How does PTH affect bone?
Stimulates resorption and inhibits deposition.
What role does calcitriol (active vitamin D) play in calcium balance?
Promotes calcium absorption from the GI tract and supports PTH action.
