40A - Lecture - Chapter #6 Flashcards
Support function of skeletal system
Framework which support skeletal muscle attachment
Functions of Bone and Skeletal System
- Support
- Protection
- Movement
- Mineral homeostasis
- Blood cell reproduction
- Triglyceride storage
Protection function of skeletal system
Protects internal soft tissue
Ex: skull -> brain
Movement function of skeletal system
Skeletal muscles contract (work, shorten). Puts tension on tendon that is attached to skeleton to move skeletal framework
Mineral homeostasis function of skeletal system
Store and release minerals; specifically calcium and phosphate
Blood cell reproduction function of skeletal system
In certain areas of long bones there is red bone marrow
Hemopoiesis
Process to make Red blood cell. Gives rise to all blood cells within long bones
Triglyceride storage function of skeletal system
Yellow bone marrow within medullary cavity in long bones
Diaphysis
Middle section of long bone
Epiphysis
Proximal and distal end of long bones
Spongy bone internally
RBM fills area in spongy bone
Metaphysis
Between diaphysis and epiphysis in long bones
Made of spongy bone
Contains epiphyseal plate and eventually epiphyseal line
Growth plate
When plate is present one can grow in height
Eventually will ossify from hyaline cartilage to bone tissue
Periosteum
Goes around entire bone except articulation area
Contains outer fibrous layer and inner osteogenic layer
Outer fibrous layer
Part of periosteum
This is where tendons and ligaments will attach
Inner osteogenic layer
Part of periosteum
Bone cells arise and growth in width
Medullary cavity
Hallow space within diaphysis
Contains yellow bone marrow in adults
This cavity will lower weight of bone
Endosteum
Lines medullary cavity
Growth in width
Calcification
The process in which minerals will be deposited and crystallized on collagen fibers and bone tissue hardness and strengthens
Osteoprogenitor cells
Originate from mesenchyme and can undergo cell division
Osteoblasts
Forms organic portion of ECM
Differentiates
Osteocytes
Maintain bone tissue
Where are osteoprogenic cells are located
- Inner osteogenic layers of periosteum
- Endosteum that lines medullary cavity
- Lining canals where blood vessels are present
- In spongy bone within RBM
Osteoclasts
Different from other 3
Causes bone resorption
Derived from WBC
Multi-nucleated
When do osteoclasts remodel bone
- Normal development
- Growth
- Maintenance
- Repair
Products that osteoclasts make
- Enzymes
- Acid
- Hormones
Enzymes (made my osteoclasts)
Digest the organic protein collagen (*collagen gives flexibility to bone without bones becoming brittle)
Acid (made by osteoclasts)
Remove minerals (calcium and phosphate) Bones become soft when minerals are removed
Hormones (made my osteoclasts)
Thyroid gland: product is calcitonin
Parathyroid gland: product is parathyroid hormone; can increase blood calcium levels
Compact bone
~80%
Major unit is osteon, has no gaps, contains YBM, has periosteum
Spongy bone
~20%
Major unit is trabeculae, has gaps, contains RBM, no blood vessels, contains osteocytes and osteoclasts
4 Ossification Principle Situations
- Initial formation of bone in embryo (1-2m) and fetus (3-9m)
- Growth of bones in infancy, childhood, and adolescence until adult
- Remodeling of bone: older bone tissue replacing newer bone tissue
- Repair fractures
2 methods of ossification
Intramembranous ossification and endochondral ossification
Intramembranous ossification
Starts as mesenchyme and forms sheet like layer of membrane
Process:
1. Vascularized therefore can bring osteoprogenitor cells. Will give rise to osteoblasts
2. Collagen fibers then initiates calcification and will differentiate into osteocytes
3. Makes spongy bone first and remodel into compact bone
Enochondral ossification
Starts as mesenchyme. Forming bone and starts as cartilage and replaces it in most area.
Process:
1. Avascular; chondroblasts (can still divide) and forms chondrocytes (can still divide). Starting in the middle chondrocytes will hypertrophy and then become calcified cartilage
2. Becomes vascularized which brings in a blood supply and creates a primary ossification center (starts making bone towards both epiphysis)
3. Due to a blood supply osteoprogenitor cells are brought in and are still able to divide
4. Osteoblasts are made through division and will differentiate into osteocytes
Appositional growth
Growth in width and diameter
Bone destroyed by osteoclasts inside and bone forms by osteoblasts on the outside
Interstitial growth
Involves epiphyseal plate. Growth in long bones of proximal and distal ends
Epiphyseal zones
- Zone of resting cartilage
* 2. Zone of proliferating cartilage - Zone of hypertrophic cartilage
- Zone of calcified cartilage
Zone of resting cartilage
Closest to epiphysis
Anchors epiphyseal line to epiphysis
*Zone of proliferating cartilage
Chondrocytes are going to divide
As long as this zone is present one will grow in height
Zone of hypertrophic cartilage
Hypertrophy means cells will enlarge or increase in size
Zones of calcified cartilage
Near diaphysis
Minerals will bring calcium and phosphate
Kills of chondrocytes, bring blood supplies and bones cells will convert into spongy bone
Remodeling of bone is involved in where?
Bone resorption: breaking down bone by osteoclasts
Bone deposition: make new bone. Osteoblasts will make collagen fiber and bring minerals
Factors that affect bone growth and remodeling
- Minerals
- Vitamins
- Hormones
Vitamins that affect bone growth and remodeling
Vitamin A: increase osteoblasts activity
Vitamin C: increase protein synthesis trying to make collagen fibers
Vitamin D: helps absorb calcium
Vitamin K and B12: same as vitamin C
Hormones affecting bone growth and remodeling
Males testes make testosterone
Female ovaries make estrogen
These increase osteoblasts activity and decrease osteoclasts activity
Human growth hormone (hGH)
Made by pituitary gland. Major role is to increase insulinlike growth factor
Insulinlike growth factor (IGF)
Made by liver. Will target zone #2 proliferation of chondrocytes.
IGF will increase osteogenic of periosteum
Women cell activity before menopause
Increase estrogen
Increase osteoblasts
Decrease activity
Bone formation > bone resorption
Women cell activity after menopause
Decrease estrogen
Decrease osteoblasts activity
Increase osteoclasts activity
Bone resorption > bone formation = osteoporosis
Open / compound fracture
breaks open skin
Closed / Simple fracture
Skin is intact
Green stick fracture
Occurs within children
Not complete break in bone, bone is flexible and not fully calcified
Stress fractures
Ex: shin splints
Process to recover
- Reactive phase
2a. Reparative phase
2b. Reparative phase - Bone remodeling phase
Reactive phase
Blood clot, area is avascular, formation of fracture hemotoma
Reparative phase (2a)
Fibrocartilaginous callus formation area is still avascular, bridge 2 ends together
Reparative phase (2b)
Bony callus formation, starts making bone because it becomes vascularized
Osteoporosis
Bone resorption outpaces bone formation
Cause: depletion of calcium and vit D
Treatment: increase calcium, vit d and exercise
Rickets
Disease in children bones, becomes soft and rubbery
Cause: vit d and calcium deficiency
Treatment:
Increase vitamin d and calcium
Osteomalacia
Adult form of rickets
New bone fails to ossify
Causes: vit d and calcium deficiency
Treatment: increase vitamin d and calcium
