Physiology of bone and calcium homeostasis Flashcards
How is soft tissue growth measured?
By weight
How is bone growth measured?
By height
What does tissue and bone growth require?
Multiple hormones and paracrines
What are the 2 effects hormones and paracrines have on tissue and bone growth?
Direct or permissive effects on growth
Which hormones are required for bone protein and cell division?
GH and IGF
What role do thyroid hormones play in tissue and bone growth?
Permissive role
What does thyroid hormone directly contribute to?
Nervous system development
What role does insulin play in bone and soft tissue growth?
Supports growth
Provides glucose energy
Which steroids play a role in bone and soft tissue growth?
Sex steroids
What does bone growth require?
Adequate dietary calcium and protein
What is bone growth impacted by?
Hormonal control of calcium homeostasis
What do calcium phosphate crystals precipitate and attach to?
Collagen fibre lattice
What is the most common calcium phosphate?
Hydroxyapatite (Ca10(PO4)6(OH)2)
What do bone cells occupy?
Spaces within the matrix, and are well supplied with blood
Which layer is compact/cortical bone?
On the outer surface of the bone
What does the compact/cortical bone provide?
Strength
Which layer is trabecular bone?
Inner spongy layer
What is trabecular bone?
Open, cell‐filled spaces between struts of calcified lattice
Is bone marrow found in all bones?
No, just some
What does bone growth require regarding the matrix?
That matrix is deposited faster than it is broken down (resorbed)
What are osteoblasts?
Modified fibroblasts that are specialised bone-forming cells
What do osteoblasts produce?
Enzymes & osteoid (collagen & protein mix)
What binds to the enzymes and osteoid produced by osteoblasts?
Hydroxyapatite
Which proteins are produced by osteoblasts?
Osteocalcin and osteonectin
What do osteocalcin & osteonectin do?
Aid in deposition
What will matrix deposit on outer surface of bone result in?
Bone diameter increase
What is the epiphyseal plate the site of?
Linear growth of long bone growth
What is the diaphysis?
End of bone shaft
Where are chondrocytes found?
Near epiphysis
What are chondrocytes?
Collagen-producing cells of cartilage
How do chondrocytes produce collagen?
Continuously dividing columns, increasing length
Collagen layer thickens & old chondrocytes disintegrate leaving spaces
What do osteoblasts do?
Lay down bone on top of cartilage base where chondrocytes degenerated
Shaft lengthens, epiphyseal plate is active
What happens to osteoblasts when they complete work?
Revert to less active form
What does bone serve as a depot for?
Stored calcium
