Ch 6: Bones and Skeletal Tissue Flashcards
What are the three cartilage types?
- Hyaline
- Elastic
- Fibrocartilage
What are the functions of hyaline cartilage?
Collagen fibers that provides support, flexibility, and resilience
What are the functions of elastic cartilage?
Elastin that maintains the shape of structure while allowing flexibilty
What are the functions of fibrocartilage?
Thick collagen fibers that allow tensile strength for absorbing compressive shock
What are the functions of fibrocartilage?
Thick collagen fibers that allow tensile strength for absorbing compressive shock
List and describe seven important functions of bones.
- Support: for soft organs and body
- Protection: for brain, spinal cord, and organs
- Movement: levers for muscle action
- Mineral and growth factor storage: Calcium, phosphorus, growth factors
- Blood cell formation (hematopoiesis): red marrow
- Triglyceride (fat) storage: in bone cavities
- Hormone production: osteocalcin
- Bone can buffer acids
What are the 2 types of bone texures?
- Compact
2. Spongy
Describe the structure of irregular and flat bones
- Thin plates fo spongy bone (diploë) covered by compact bone
- No shaft or epiphyses
- No marrow cavity
- Hyaline cartilage covers articular surfaces
Decribe the structue of long bones
Contains tubular diaphysis and epiphyses separated by an epiphyseal line
Where is red marrow found?
In trabelular cavities of spongy bone and diploë of flat bones
What are the 5 major cells of bone tissue?
- Osteogenic cells
- Osteoblasts
- Osteocytes
- Bone lining cells
- Osteoclasts
What is another name for osteogenic cells?
Osteoprogenitor cells
What are osteogenic cells?
- Mitotically active stem cells in peristeum and endosteum
- Can become osteoblasts or bone lining cells
What are osteoblast?
Bone forming cells that are actively mitotic and secrete unmineralized bone matrix
What is another name for bone matrix?
Osteoid
What are osteocytes?
- Mature bone cells in lacunae that maintain the bone matrix
- Senses stress or strain to regulate bone remodeling
What are bone-lining cells?
Flat surface cells that assist the maintenance of the matrix
What’s the difference between periosteal and endosteal cells?
Periosteal: external bone surface
Endosteal cells: internal bone surface
What are osteoclasts?
- Derived from hematopoietic stem cells that became macrophages
- Assists with bone resorption
- Rests in resoption bay and has ruffled borders
What are the organic components of bones?
Cells, osteoid, and collagen
What are organic components of bones for?
Provide structure, tensile strength, and flexibility
Describe what a sacrificial bond is
Bonds in or between collagen that provide resiliency to the bone by stretching and breaking easily to dissipate energy and prevent fractures
Are sacrificial bond permanent?
Bonds re-form
What is an example of inorganic compounds in bone?
Hydroxyapatites (mineral salts)
What are hydroxyapatites’ function?
Tiny calcium phosphate crystals in and around collagen fibers that is responsible for hardness and resistance to compression
What are the 2 types of postnatal bone growth?
- Interstitial (longitudinal) growth
- Appositional growth
What is the difference between interstitial and appositional growth?
Inter: increase in long bone length and occurs at the growth plate
App: increase in bone thickness and width
Describe the process of epiphyseal plate closure
- Bone lengthening ceases
- Epiphysis and diaphysis fuse
- Female: 18, Male: 21
How does the bone widen by appositional growth?
- Osteoblasts beneath periosteum secrete bone matrix on external bone
- Osteoclasts remove bone on endosteal surface
What are the hormones that promote bone growth?
- Growth hormone
- Thyroid hormone
- Testosterone and estrogens
How does growth hormone promote bone growth?
Stimulates epiphyseal plate activity
How does thyroid hormone promote bone growth?
Modulates activity of growth hormone
How does testosterone and estrogen promote bone growth?
- Promote adolescent growth spurts
- Ends growth by inducing epiphyseal plate
What are some elements of bone homeostatsis?
- Recycling 5-7% of bone mass each week
- Older bone becomes more brittle
- Bone remodeling and bone repair
How often in spongy bone replace?
3-4 yrs
How often is compact bone replaced?
10 yrs
How is bone remodeling homeostatic?
Bone deposit and resorption occurs
How is bone remodeling negative feedback?
In response to mechanical and gravitational forces, a negative feedback hormonal loop for Ca2+ homeostasis is activated
How does parathyroid hormone promote control of blood Ca2+?
Removes calcium from bone
How does calcitonin promote control of blood Ca2+?
Produced by parafollicular the cells in the thyroid, it temporarily lowers blood calcium
Explain the negative feedback hormonal loop for blood Ca2+
- Controlled by PTH
- Blood calcium levels drop
- PTH releases stimulating osteoclasts to degrade bone matrix, releasing Ca2+
- Blood Ca2+ levels rise
- PTH release ends
What is the importance of calcium?
- Nerve impulse transmission
2. Muscle contraction
How much calcium is in the body and blood?
1200-1400g; 9-11mg/dL
What is the neuromuscular problem when calcium levels are too low?
Hyperexicitability
What is the neuromuscular problem when calcium levels are too high?
Nonresponsiveness
What is hypercalcemia?
When high blood calcium deposits calcium salt in blood vessels and kidneys
What are the hormones that promote blood Ca2+ levels?
- PTH
2. Calcitonin
What are the hormones that affect bone density?
- Leptin
2. Serotonin
What is leptin?
Released by adipose tissue inhibiting osteoblasts
What is serotonin?
Neurotransmitter that regulates mood and sleep, secreted after eating and interferes with osteoblast activity
What happens when a bone is poorly mineralized creating soft, weak bones and pain upon bearing weight?
Osteomalacia
What disease causes bowed legs due to vitamin D deficiency or insufficient calcium?
Rickets
What occurs when bone resorption outpaces deposit resulting in spongy or porous bone?
Osteoporosis
What occurs when bone resorption outpaces deposit resulting in spongy or porous bone?
Osteoporosis
What are common risk factors for osteoporosis?
Aged, postmenopausal women
Petite body
Smoking
What are some treatments of osteoporosis?
- Calcium
- Vitamin D supplements
- Weight-bearing exercise
- Hormone replacement therapy
What are come new drugs for osteoporosis?
- Bisphosphonates
- Selective estrogen receptor modulators
- Statins
- Denosumab
How does Bisphosphonates treat osteoporosis?
Decreases osteoclast activity and number
How does Statins treat osteoporosis?
Lowering cholesterol and increase bone mineral density
How does SERMS treat osteoporosis?
Mimic estrogen without targeting breast and uterus
How does Denosumab treat osteoporosis?
Improves bone density and provides monoclonal antibodies
What causes Paget’s disease?
The excessive and haphazard bone deposit and resorption
What are some treatments of Paget’s?
- Calcitonin
2. Biphosphonates