Chapt 7 Bone Tissue Flashcards
Five basic functions of skeleton
- Support
- Storage
- Blood cell formation (hemopoisis)
- Protection
- Leverage
Diaphysis
Tubular shaft of the bone
-walls consist of a layer of solid compact bone
Epiphyses
Extended areas at ends of bone
-consists mostly of spongy bone covered in thin layer of compact bone
What’s inside the spaces of spongy bone
Red marrow
Metaphyses
Areas in between the epiphyses and diaphysis
-represents areas where a long bone can grow in length
Marrow cavity
The space within diaphysis that contains yellow marrow in adult long bones
Periosteum
Connective tissue covering the surface of the bone
-contains bone forming cells that allow bones to grow in diameter or thickness (osteoprogenitor)
-protects bone
Endosteum
Lining of marrow cavity which contains some bone forming cells and some connective tissue
Articular cartilage
At ends of long bone, cartilage reduces friction and absorbs shock at the joints
What is bone tissue
Supportive connective tissue containing specialized cells and is surrounded by extracellular fluid
What is the bone matrix composed of
33% collagen fibers
67% inorganic components (mostly calcium salts)
Calcium salts are mainly:
Hydroxyapatite (calcium phosphate and calcium carbonate)
Calcification
Process of bone hardening:
Salts are deposited on framework of collagen fibers and crystallize
Osteoprogenitor (osteogenic) cells
Unspeciallized stem cells of bone tissue
-it divides to form another stem cell and an osteoblast as daughter cells
Osteoblasts
Cells responsible for calcification
-surround themselves in matrix then transform into osteocytes
Osteocytes
Mature bone cells
-no longer secrete matrix
-maintain bone metabolism
-can convert back to osteoblasts or osteoprogenitor if damaged to participate in repair
Osteoclast
Very large cells that function to remove calcium salts and recycle bone matrix
-release acids and enzymes that digest bone matrix as part as normal growth, repair and mineral homeostasis
What does compact bone do?
-Makes up most of the diaphysis and lies over spongy bone tissue in the epiphyses
-forms a protective layer and gives bone more support and resistance to stress
How is compact bone arranged?
In units called osteons with very little space between them, each osteon contains osteocytes arranged in layers around the central canal that contains blood vessels
Why can’t compact bone be bent?
Because osteons are aligned in the same direction along lines of stress
Does spongy bone contain osteons?
No it consists of trabeculae
Trabeculae
Irregular honey comb structure of bone tissue making up spongy bone. Surrounds many red marrow filled spaces
Where is spongy bone found?
Where bones are not heavily stressed, mostly in short, flat, irregular shaped bones
What does spongy bone do?
Supports and protects red bone marrow (where blood formation occurs)
Ossification
Process of bone formation
Epiphyseal plates
Areas where bones can increase in length under the influence of human growth and sex hormones
What bone is the last bone to stop growing
Clavicle
What happens when growth stops?
Epiphyseal plates fade into Epiphyseal lines
Bone growth and remodeling at birth to adolescence
More bone is produced than is lost through bone resorption
Bone growth and remodeling in young adults
Rates of bone production and resportion are about the same
Bone growth and remodeling at middle age to elderly
Bone mass decreases because more bone is resorbed than produced (demineralization)
PTH hormone
Realeased from parathyroid glands when blood calcium is low
PTH hormone acts to:
- Stimulates osteoclasts
- Inhibit osteoblasts
- Inhibit excretion of calcium in the kidneys
- Stimulate the formation of calcium
When is calcitonin released?
When blood calcium is too high, released from thyroid gland
Calcitonin acts to:
- Inhibit osteoclasts
- Stimulate osteoblasts
Osteoporosis
Weakening of the bones due to decreased deposition of calcium salts
-common in elderly
Why re woman more at risk for getting osteoporosis?
-they have less bone mass
-reproduction hormones contribute to bone decomposition
