Chapter 7: Skeletal System: Bone Structure Flashcards
Bone classifications
- long
- short
- flat
- irregular
Regions of a long bone
- diaphysis
- medullary cavity
- epiphysis
- articular cartilage
- metaphysis
- epiphyseal plate
Diaphysis
elongated, usually cylindrical shaft
Medullary cavity
hollow space within the diaphysis
Epiphysis
knobby region at each end of the long bone; composed of outer compact bone and inner spongy bone
Articular cartilage
thin layer of hyaline cartilage that covers the joint surface
Metaphysis
region where bone widens and transfers weight between the diaphysis and epiphysis
Epiphyseal plate (growth plate)
thin layer of hyaline cartilage located within metaphysis; the epiphyseal line is boney remnant of the epiphyseal plate
Hematopoiesis
process of blood cell production; occurs in red bone marrow connective tissue
Bone cells
- osteoprogenitor cells
- osteoblasts
- osteocytes
- osteoclasts
Osteoprogenitor cells
“ancestral” cells; stem cells
Osteoblasts
“bone builder” cells; produce new bone matrix
Osteocytes
“mature” bone cells; maintain bone matrix
Osteoclasts
“bone cleaver/cutter of cells”; break down (resorb) bone matrix
Process of intramembranous ossification
1- ossification centers form within thickened regions of mesenchyme
2- osteoid undergoes calcification
3- woven bone and surrounding periosteum form
4- lamellar bone replaces woven bone, as compact and spongy bone form
Process of endochondral ossification
1- fetal hyaline cartilage develops
2- cartilage calcifies and a periosteal bone collar forms around diaphysis
3- primary ossification center forms in the diaphysis
4- secondary ossification centers form in diaphysis
5- bone replaces cartilage, except for the articular cartilage and epiphyseal plates
6- epiphyseal plates ossify and form epiphyseal lines
Describe the steps involved in interstitial growth
1- a chondrocyte with a lacuna begins to exhibit mitotic activity
2- two cells (now called chondroblasts) are produced by mitosis from one chondrocyte and occupy one lacuna
3- each cell produces a new matrix and begins to separate from its neighbor. each cell is now called a chondrocyte
4- cartilage continues to grow internally
Describe the steps involved in appositional growth
1- mitotic activity occurs in stem cells within the perichondrium
2- new undifferentiated stem cells and committed cells that differentiate into chondroblasts are formed
3- chondroblasts produce a new matrix at the periphery
4- as a result of matrix formation, the chondroblasts push apart and become chondrocytes
5- chondrocytes continue to produce more matrix at the periphery
Hormones that promote bone growth
- growth hormone
- thyroid hormone
- calcitonin
- sex hormones
- parathyroid hormone
- calcitriol
Growth hormone
stimulates liver to produce the hormone IGF (insulin-like growth factor), which causes cartilage proliferation at epiphyseal plate and resulting bone elongation
Thyroid hormone
stimulates bone growth by stimulating the metabolic rate of osteoblasts
Sex hormones
stimulate osteoblasts; promote epiphyseal plate growth and closure
Hormones that regulate blood calcium levels
parathyroid hormone, calcitriol, and calcitonin
How do the parathyroid hormones and calcitriol regulate blood calcium levels?
together, PTH and calcitriol target various effectors to ultimately instigate a ride in blood calcium levels and return to homeostasis
Calcitonin
promotes calcium deposition in bone and inhibits osteoclast activity
