W10 - Skeletal System (Lecture) Flashcards
(30 cards)
What two cell types do mesenchymal stem cells become?
Osteoblasts and chondrocytes
What stem cells form osteoclasts?
Hematopoietic
What do osteoblasts become?
Osteocytes
What do osteoblasts/clasts do?
Osteoblast - build bone, osteoclast - reduce bone
Paresthesia and muscle twitching occur when theres low calcium, what is a third symptom?
Numbness
If theres too much calcium, digestive stress, bone pain + muscle weakness occur, what are 4 other symptoms?
Thirst, frequent urination, lethargy, fatigue and cardiac arrhythmia
What three things are balanced during bone maintenance?
Bone formation, resorption and elongation
Do osteoblast/clasts work in reduced/increased blood calcium?
Blast - reduced Ca, Clast - increased Ca
Growth hormone increases length of bones, what 2 other things does it do?
Enhances mineralisation and improves bone density
How does the effects of GH differ between youth and adults?
Youth - growth plate open so adds to length and thickness. Adults - growth plate closed so only adds to thickness
What does thyroxine released by the thyroid do?
It has a +ve effect on GH released from pituitary gland
Sex HMs promote bone formation/maintenance of bone density, what else is promoted?
Closure of growth plate
Estrogen in females causes reduced bone length, how does this happen?
It causes earlier growth plate closure
What happens during menopause?
Bone density is lost
What two receptors are found in the growth plate of the bone?
Androgen and estrogen receptors
Calcitriol is an active metabolite of vitamin D3, what is V D3 derived from?
Cholesterol
What is the function of VD?
Facilitates intestinal absorption of calcium, phosphate and magnesium
VD binds intracellular VDR, as well as a VD binding site there is another binding ssite on VDR, what for?
DNA binding site
VD3-VDR complex stimulates calcium transporters and bone matrix proteins, what does it suppress?
Synthesis of type I collagen
When there is too little calcium, PTH is produced from the parathyroid gland, what 2 things does this have a +ve effect on?
Osteoclast action and conversion of cholecalciferol to calcitriol in the liver
Therefore, what is increased by having too little Ca?
Intestinal uptake of Ca (caused by the increase in calcitriol)
Too much calcium leads to increased calcitonin release from the thyroid gland. What does CT act +vely and -vely on and what overall effect does this have on Ca?
+vely on osteoblasts, -vely on osteoclasts, reducing blood calcium
What is Wolff’s law?
Form follows function
What does mechanical strain lead to?
Re-distribution of Ca2+ between blood and bone tissue
