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True or false: Bone is not a type of connective tissue.
- a bone stem cell
- the precursor to all the other cell types
What are osteoblasts?
they are dividing cellsthey are responsible for laying down the components of bonewe can disstinguish them from other cells which all start with "osteo-" by remembering that they are bone building blasts.
What is the funciton of osteocytes?
they maintain bone integrity within spaces inside of bone
- constsnly tunnel through bone, dissolving the bone matrix as they go.
- They are followed by osteoblasts
- in this way bone is constantly renewed and can sytrengthen when needed.
Both _________ and _________ play an important role in keeping blood ________ and phosphorus within normal limits so they are controlled by _________.
osteoblasts, osteoclasts, calcium, hormones
What are the four cell types found in bone?
- osteogenic cell: precursor to other cell types
- Osteoblast: forms bone (bone building osteoblasts)
- osteocyte: maintains bone tissue
- osteoclast: break down bone (bone chewing osteoclast)
- osteoblasts and osteoclasts are regulated by hormones
What are the two components of bone?
inorganic and organic
- The ionorganic portion of bone
- a compound of calcium, phosphate and hydroxyl groups
- its chemicla formula is : Ca10(PO4)6(OH)2
- This forms the rigid, brittle inorganic matrix of bone.
Bone also has an organic matrix, made up of mostly _______ ____ __.
collagen type I
Bone is natures _________ material. Just like the skin of amodern jet fightyer is composite material of metal and non-metal, ______ depends on the proper mixture of _______ and ________ components.
composite, inorganic, organic
True or False: If bones have to little mineral, it becomes brittle and fractures easily.
False. If bones have to much mineral, it becomes brittle and fractures easily.- This happens in the disease osteogenesis imperfecta, or "brittle bone disease".
What causes children with rickets and adults with osteomalacia to have soft and pliable bones?
If the bones have to much collagen
Why is it nessesary to have both mineral (inorganic) and collagen (organic) components working together?
- Mineral alone is to brittle
- -Osteogenesis imperfecta
- Organic alone is to flexible
- -rickets or osteomalacia
Graphic objective 3. Compare and contrast compact and spongy bone.
If blood _________ is low, the body breaks down ________ _______ to release calcium into the bloodstream. If blood calcium is high, the body stores ______ in ______for future needs.
calcium, mineralized bone, calcium, bone
True or False: A balance between osteoblasts and osteoclasts is critical, and is under hormonal control.
If you have low blood calcium...
- the body withraws calcium from its calcium "bank": bone tissue
- Parathyroid hormone is released from a set of small pea-shaped glands next to the thyroid
- this increased osteoclasts activity
- Osteoclasts break down the mineral portion of bone and calcium is released into the bloodstream.
If blood calcium is too high...
- Calcitonin is made by parafolicular cells (C cells) in the thyroid gland
- -it is released when calcium is high and stimulates osteoblasts
- Theses absorb calcium form the bloodstream and dposit it as hydroxyapatite in bone.
What are the three hormones involved in hormonal control of the blood?
- 1. Calcitonin
- 2. Parathytroif hormone (PTH)
- 3. Calcitriol
- inhibirs osteoclasts
- stimulates osteoblasts
- decreases blood calcium
- increases bone formation
Parathyroid hormone (PTH)
- stimulates osteoclasts
- inhibits osteoblasts
- increase blood calcium
- decrease bone formation
- not directly invoved with bone however,
- PTH stimulates kidneys to release calcitriol, which increases absorption of calciumfrom food
There are two D vitamins. Vitamin D2 (___________) and vitamin D3 (___________) are made in the skin with the help of UV-B light (i.e. ______ _______).
ergocalciferol, cholecalciferol, natural sunlight
True or false: Vitamin D is importand in the intestinal absoption of calcium.
In the absences vitamin D...
- blood calcium levels drop and bones become soft and flexible (bones are nostly colagen because mineral portion is lacking)
- In children this results in rickets
- In adults, inability to form mineralized bone
- May result from metabolic disturbances, cancer, or cancer chemotherapy
- Scan shows radioactiv 99Tc concentrating in areas that are making organic bone matrix but not the inorganic materialized porttionof bone.