Bones Flashcards
(18 cards)
What are the main functions of bones (5)
- Blood cell production
- Calcium store + phosphate store
- Protection
- Leverage
- Yellow bone marrow acts as an energy store for triglycerides
What is the periosteum and where is it found
Surrounding the bone but bottle objective tissue
Osteoprogenator cells- describe them
Unspecialised stem cells derived from Mesenchyme
They produce osteoblasts
Found in the periosteum and endosteum
What are osteoblasts
Bone forming cells found in the periosteum and Endosteum
What are osteocytes
They are mature osteoblasts that no longer secrete bone matrix
What are osteoclasts
They are found on the inside of bone and they degrade bone using powerful lysosomal enzymes
How much blood flows through bones ever minute
200ml/ minute
How is the bone matrix structured
Collagen fibres surrounded by hydroxyapatite
What is the canaliculi
The horizontal channels connecting lacunae
Describe the process by which bone grows in length
The cartilage at the end of the bone undergoes mitosis
- Zone of resting- nothing grows here
- Proliferation zone- chondrocytes undergo mitosis
- Hypertonic zone- cells mature and increase length of diaphysis
- Calcified cartilage- dead chondrocytes get calcified
Describe the steps for increased bone width
- Periosteal cells deferentiate into osteoblasts
- These secrete collagen fibres so bone forms around them
- Ridges fuse together
- Periosteum becomes Endosteum- central canal
- Bone lining in the medullary cavity is degraded by osteoclast
What percentage of calcium is stored in bones
What is the blood concentration of calcium
99%
2.5mmol/L
Location of secretion of parathyroid hormone and how it effects blood calcium levels
Secreted by the chief cells in the thyroid gland in response to low calcium levels
- increase osteoclast activity
- increase calcium from bone
- increase renal excretion of phosphate
- increase active vitamin D
Where is vitamin D3 produced and what does it do
Steroid hormone which is ingested in the skin
Pro hormone is connected to its active state by kidney and liver
Vitamin D3 and PTH- what does it do
Calcium and phosphate absorption in the SI
Release of Ca2+ in bone
What does calcitonin do and where is it produced
Produced by the C-cells is b the thyroid glands in response to increase blood calcium levels
Decreased osteoclast activity
Increased osteoblast activity
Factors the effect bone growth (3)
Nutrition
Steroids
Insulin growth factor
What is the make up of bones
25% of water
25% protein
50% minerals calcium phosphate and calcium carbonate- hydroxyapatite
