Skeleton

Question 1

Bone growth in length is called what? Bone growth in width is called what?

Answer 1

longitudinal growth; appositional growth

Question 2

Where does longitudinal growth start?

Answer 2

the epiphyseal plate

Question 3

What are the 2 sides of the epiphyseal plate?

Answer 3

the diaphysis side and the epiphyseal side

Question 4

What are the 4 steps to longitudinal growth?

Answer 4

1.) cells on the diaphysis side of the plate start to replicate and push the epiphyseal plate upwards
2.) as new cells are pushed up, old cells below calcify and die
3.) the dead, calcified cells form the spongy bone
4.) osteoclasts digest the spongy bone to lengthen the medullary cavity and turn it into compact bone

Question 5

What are the 3 steps to appositional growth?

Answer 5

1.) osteoblasts on the bone side of the periosteum deposit bone on the external surface
2.) osteoclasts on the endosteal surface break down bone
3.) the medullary/marrow becomes enlarged

Question 6

What 2 activities are part of bone remodeling?

Answer 6

bone deposition and bone resorption

Question 7

T/F: bone remodeling only happens after a fracture

Answer 7

False; bone remodeling is continuously happening

Question 8

Describe bone deposition

Answer 8

osteocytes produce an empty matrix (osteoid seam) and calcium and phosphate ions soon move into it; the ions accumulate and form the salt, hydroxyapatite; the calcium salts are then crystalized and become a solid

Question 9

What is hydroxyapatite?

Answer 9

a salt formed in the osteoid seam from combination of calcium and phosphate ions

Question 10

T/F: the osteoid seam is empty

Answer 10

True

Question 11

Describe bone resorption

Answer 11

T-lymphocytes activate osteoclasts which release special enzymes contained within the cells; the enzymes digest the matrix; at the same time, osteoclasts secrete HCl (acid) which converts calcium salts to a water-soluble form; the digested matrix (which contains the dissolved calcium salts) is released into interstitial fluid on the outside of the bone; this eventually makes it to the blood stream

Question 12

What are T-lymphocytes

Answer 12

a type of cell that activates osteoclasts - seen in bone resorption

Question 13

What are 3 factors that affect bone growth? Why is each important?

Answer 13

1.) Diet - must have calcium and phosphate in our diet
2.) Vitamins - must have Vitamin D in order for calcium to be absorbed (we get this from the sunlight)
3.) Hormones - PTH and calcitonin