Physiology of Bone Repair Flashcards
What are the two main
causes/determinants of bone remodelling?
Calcium homeostasis
Mechanical stress
Which of the following is a symptom/sign of acute hypocalcemia
> Constipation >Fatigue > Low mood >Muscle spasms >Neuromuscular depression
Muscle spasms
Hypocalcaemia induces hyper-excitability
All of the following are symptom/signs of chronic hypocalcaemia EXCEPT Carpopedal spasm Delayed dentition Scoliosis Short stature Enlarged iliac crest
Enlarged iliac crest
Which of the following is a symptom/sign of acute hypercalcemia Chvostek’s sign Rales Joint pains Diarrhoea Arrhythmias
Arrhythmias
Name 5 functions of the skeleton
Maintaining body structure locomotion haematopoiesis ca2+/mineral homeostasis protection of inner organs,
Name three organs that are affected by PTH
Bone, Kidney, Gastrointestinal tract
Name 5 symptoms of chronic hypocalcaemia
Delayed dentition, short stature, pigeon chest, scoliosis, easily fractured bones, etc.
Name 5 symptoms of hypercalcaemia
neuromuscular depression. And calcium deposition
groans (constipation), moans (psychotic noise), bones (bone pain, especially if PTH is elevated), stones (kidney stones), and psychiatric overtones (including depression and confusion).
What is the cause of autosomal dominant osteopetrosis?
bone resorption is reduced compared to mineralisation
This is due to failure of osteoclasts
Osteoclasts cannot secrete acid
Either acid pump or chloride channel is mutated
Name 5 signs of autosomal dominant osteopetrosis AND for each one explain how osteopetrosis leads to this symptom.
Increased bone density (compromised bone resorption due to failure of osteoclasts),
Deafness (nerves compromised when skull foramina filled),
Blindness (skull foramina filled),
Frail bones (bone remodelling is not directional),
Anaemia (bone spaces for haematopoiesis compromised)
How do osteoclasts resorb bone: how do they position themselves, what do they secrete, and why are these two functionally connected?
They create a ruffled border with integrins to surround the region of resorption,
They create a lysosome-like space extracellularly where they secrete acid (to digest hydroxyapatite), and proteases (to digest the matrix proteins such as collagen),
The ruffled border is necessary to prevent dilution of the acid and loss/misapplication of the proteases
Name 5 differences between osteoblasts and osteoclasts with regard to: mitosis, genetic material, size, overall function, and developmental origin
Blasts cannot divide, are mononucleate, smaller than clasts, lay down bone, and develop from mesenchyme.
Clasts are multinucleate, can proliferate, are substantially bigger than blasts, reabsorb bone, and are derived from haematopoietic tissue
Name 5 differences between osteoblasts and osteocytes with regard to: location, shape, size/shape, overall function, and developmental origin
Blasts are on endosteal surface, cigar-shaped, the same size as cytes, they lay down bone and they are mesenchymal.
Cytes are within osteoid, they are stellate (star) shaped with many extended processes, they maintain osteoid, and they are derived directly from osteoblasts that are trapped inside osteoid
Describe PTH in terms of: chemical class, origin, effects at bone, effects at GI tract, effects at kidney
PTH is a peptide hormone, Origin from parathyroid glands, Net effect of resorption, Minor effect on increasing GI calcium absorption, Increases Ca2+ resorption at kidney.
Describe Vitamin D in terms of: chemical class, origin, effects at bone, effects at GI tract, effects at kidney
Vitamin D is a broken steroid,
It is created in skin and is further modified by enzymatic actions derived from the liver, and kidney,
It indirectly stimulates osteoclasts (via effects on osteoblasts),
Strong effect on increasing GI absorption of Ca2+.
Vitamin D’s effects on Ca2+ resorption at Kidney are controversial.
Name 4 classes of molecular constituents in bone matrix
Hydroxyapatite (Ca-phosphate),
Collagen (and other structural proteins such as elastin),
Glycosaminoglycans,
Growth factors,
Name 3 symptoms of acute hypocalcaemia
BAD-CATS: Bleeding, Anaesthesia, Dysphagia, Convulsions, Cardiac arrhythmias, latent tetany, spasms, stridor
What is this entire microscopic structure in bone called
Haversian system, or an individual area is an osteon
Give 3 reasons why you need bone resorption.
Bone resorption is essential for repair of broken bones, remodelling of bones as person grows (ie from child to adult), remodelling of bone for specific stresses, and plasma calcium homeostasis.
How is hydroxyapatite (e.g. calcium phosphate crystals) resorbed when bone is being remodelled? (3)
Hydroxyapatite is brought into solution by
A) acid, which makes calcium phosphate less soluble,
B) phagocytosis of calcium phosphate by osteoclasts, and
C) digestion of proteins etc that nucleate crystallisation by acid hydrolases (eg by Cathepsin K)