Chapter 7: Skeletal System: Bone Structure

Question 1

Bone classifications

Answer 1

• long
• short
• flat
• irregular

Question 2

Regions of a long bone

Answer 2

• diaphysis
• medullary cavity
• epiphysis
• articular cartilage
• metaphysis
• epiphyseal plate

Question 3

Diaphysis

Answer 3

elongated, usually cylindrical shaft

Question 4

Medullary cavity

Answer 4

hollow space within the diaphysis

Question 5

Epiphysis

Answer 5

knobby region at each end of the long bone; composed of outer compact bone and inner spongy bone

Question 6

Articular cartilage

Answer 6

thin layer of hyaline cartilage that covers the joint surface

Question 7

Metaphysis

Answer 7

region where bone widens and transfers weight between the diaphysis and epiphysis

Question 8

Epiphyseal plate (growth plate)

Answer 8

thin layer of hyaline cartilage located within metaphysis; the epiphyseal line is boney remnant of the epiphyseal plate

Question 9

Hematopoiesis

Answer 9

process of blood cell production; occurs in red bone marrow connective tissue

Question 10

Bone cells

Answer 10

• osteoprogenitor cells
• osteoblasts
• osteocytes
• osteoclasts

Question 11

Osteoprogenitor cells

Answer 11

“ancestral” cells; stem cells

Question 12

Osteoblasts

Answer 12

“bone builder” cells; produce new bone matrix

Question 13

Osteocytes

Answer 13

“mature” bone cells; maintain bone matrix

Question 14

Osteoclasts

Answer 14

“bone cleaver/cutter of cells”; break down (resorb) bone matrix

Question 15

Process of intramembranous ossification

Answer 15

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

Question 16

Process of endochondral ossification

Answer 16

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

Question 17

Describe the steps involved in interstitial growth

Answer 17

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

Question 18

Describe the steps involved in appositional growth

Answer 18

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

Question 19

Hormones that promote bone growth

Answer 19

• growth hormone
• thyroid hormone
• calcitonin
• sex hormones
• parathyroid hormone
• calcitriol

Question 20

Growth hormone

Answer 20

stimulates liver to produce the hormone IGF (insulin-like growth factor), which causes cartilage proliferation at epiphyseal plate and resulting bone elongation

Question 21

Thyroid hormone

Answer 21

stimulates bone growth by stimulating the metabolic rate of osteoblasts

Question 22

Sex hormones

Answer 22

stimulate osteoblasts; promote epiphyseal plate growth and closure

Question 23

Hormones that regulate blood calcium levels

Answer 23

parathyroid hormone, calcitriol, and calcitonin

Question 24

How do the parathyroid hormones and calcitriol regulate blood calcium levels?

Answer 24

together, PTH and calcitriol target various effectors to ultimately instigate a ride in blood calcium levels and return to homeostasis

Question 25

Calcitonin

Answer 25

promotes calcium deposition in bone and inhibits osteoclast activity