CHAPTER 7/8 TEST REVIEW Flashcards
types of bones (% bone mass)
Compact bone
* Dense or cortical bone
* 80% of bone mass
* Spongy bone
* Cancellous or trabecular bone
* Located internal to compact bone
* Appears porous
* 20% of bone mass
functions of bones
Support and protection
Levers for movement
Hematopoiesis
* Blood cell production
* Occurs in red bone marrow CT
Storage of mineral and energy reserves
Calcium and phosphate
4 classes of bone…..shape/examples
Long bones
* Greater in length than width; for example femur, humerus
Short bones
* Length nearly equal to width; for example carpals and
tarsals
Flat bones
* Flat, thin surfaces, may be slightly curved; for example
cranial bones
Irregular bones
* Elaborate, sometimes complex shapes; for example
vertebrae
4 types of bone cells (functions)
- Osteoprogenitor cells
- Osteoblasts
- Osteocytes
- Osteoclasts
what is the function of osteoprogenitor cells
Stem cells derived from mesenchyme
* Cellular division yields another stem cell and a “committed
cell”
* Matures to become an osteoblast
* Located in periosteum and endosteum
what is the function of Osteoblasts
Form from osteoprogenitor stem cells
* Synthesize and secrete osteoid
* Initial semisolid organic form of bone matrix
* Osteoid later calcifies
* Become entrapped within the matrix
* Differentiate into osteocytes
what is the function of Osteocytes
Mature bone cells derived from osteoblasts
* Detect stress on bone; trigger new bone formation
what is the function of Osteoclasts
Large, multinuclear, phagocytic cells
* Derived from fused bone marrow cells
* Ruffled border increases surface area exposed to bone
* Located within/adjacent to a depression/pit on bone
surface
* Resorption lacuna
* Involved in bone resorption (breakdown of bone)
epiphyseal plate/line
Maintains thickness during childhood
* At maturity, rate of cartilage production slows
* Remnant is an internal thin line of compact bone
* Epiphyseal line
clinical view —–slide 75 Achondroplastic Dwarfism
Achondroplasia
* Characterized by abnormal conversion of hyaline cartilage
to bone
* Most common, achondroplastic dwarfism
* Long bones of limbs stop growing in childhood
* Other bones continue normal growth
* Short in stature but large head
* Failure of chondrocytes in epiphyseal plate to grow and
enlarge
* Inadequate endochondral ossification
amount of bone replaced yearly
20% of skeleton replaced yearly
hormones that influence bone growth/remodeling
Growth hormone
Thyroid hormone
Sex hormones
Glucocorticoids
Serotonin
clinical view—-slide 89 Rickets
Disease caused by vitamin D deficiency in childhood
Characterized by deficient calcification of osteoid tissue
Bowlegged appearance
Disturbances in growth, hypocalcemia, and tetany (cramps
and twitches)
* Caused by low blood calcium
Occurs in some developing nations
Incidence increasing in urban U.S. children
clinical view—-slide 95 Osteoporosis
Results in decreased bone mass, weakened bones prone to
fracture
Linked to age, onset of menopause, Caucasian race,
smoking, family history, and sedentary lifestyle
Postmenopausal women at most risk
Increased incidence of fracture
* Especially at wrist, hip, vertebral column
Best treatment is prevention with diet and physical activity in
young adults
Medical treatments involve
* Slowing rate of bone loss
* Attempting to stimulate new bone growth
Fig. 7.16—types of fractures/descriptions
steps of fracture repair
Fracture hematoma forms
* Blood vessels torn within periosteum
2) Fibrocartilaginous (soft) callus forms
* Fracture hematoma reorganized into a CT procallus
* Fibroblasts produce collagen fibers
* Chondroblasts form dense regular CT
* Procallus becomes fibrocartilaginous (soft) callus
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3) Hard (bony) callus forms
* Osteoblasts adjacent to callus produce trabeculae
* Replaces callus
* Forms a hard (bony) callus
* Continues to grow and thicken
4) Bone is remodeled
* Final phase of fracture repair
* Osteoclasts remove excess bony material
* Compact bone replaces primary bone
* Usually leaves a slight thickening of bone
