Bone

Question 1

what tissue does bone originate from

Answer 1

• mesenchyme

Question 2

what is the first bone to ossify/when

Answer 2

• the clavicle

- 6 weeks gestation

Question 3

define osteocyte

Answer 3

mature bone cell that turns over bone mineral and assists in repair

Question 4

define osteoblast

Answer 4

• immature bone cell that secretes organic matrix

Question 5

define osteoprogenitor cell

Answer 5

• stem cell that divides to produce osteoblasts

Question 6

define osteoclast

Answer 6

• multinucleated cell that secretes acids/enzymes to dissolve bone matrix

Question 7

outline the steps of intramembranous ossification

Answer 7

• cells unite in center of mesenchyme and form the blastemal
• osteogenic cells then become osteoblasts
  osteoblasts lay down ossified tissue matrix
• osteoblasts get caught in lacunae and become mature osteocytes

Question 8

What types of bones grow intramembranously

Answer 8

• flate bones: bones of the skull, scapula

Question 9

Describe the two ways in which the skull grows in childhood

Answer 9

• appositional/depositional growth via osteoblasts on the outer surface causes a lateral & outward expansion.
• Reabsorption by osteoclasts enlarges the internal cavity making room for the growing brain

Question 10

What bone utilizes both endochondrial and intramembranous growth?

Answer 10

the jaw

Question 11

What is the result of too much growth hormone before vs after puberty?

Answer 11

• before: Increase in height with normal proportions

- after: thickening of bone and overgrowth of connective tissue

Question 12

what are the steps involved with endochondral ossification

Answer 12

• mesenchymal clump > cartilaginous model
• osteoblasts begin ossification from the center of the cartilaginous model and move outwards
• cartilage remains at articulating surfaces

Question 13

give examples of endochondral ossification

Answer 13

• short bones: Carpals, tarsals

- Long bones: tibia, femur, humerus

Question 14

Describe the 5 steps of long bone ossification

Answer 14

(a) Mesenchymal cells differentiate into chondrocytes. (b) The cartilage model of the future bony skeleton and the perichondrium form. (c) Capillaries penetrate cartilage. Perichondrium transforms into periosteum. Periosteal collar develops. Primary ossification center develops. (d) Cartilage and chondrocytes continue to grow at ends of the bone. (e) Secondary ossification centers develop. (f) Cartilage remains at epiphyseal (growth) plate and at joint surface as articular cartilage.

Question 15

what is the functional unit of bone

Answer 15

• osteon

Question 16

where are osteocytes housed

Answer 16

lacunae

Question 17

through what structure do osteocytes communicate

Answer 17

• canaliculi

Question 18

at how many weeks of gestation would we see endochondral ossification begin

Answer 18

• 9 weeks

Question 19

What two methods were developed to determine skeletal age

Answer 19

• Atlas method by Greulich and Pyle (American)
• TW2 method by tanner and whitehouse (british) (better reliability)
• Atlas will give a lower rating than TW2 for a given individual

Question 20

What body part is used to study skeletal age most often; why?

Answer 20

• The hands

- There are many bones present therefore many ossification centres to look at

Question 21

What happens to bone development if there’s a decrease in HGH and gonadotrophins; give an example

Answer 21

• delayed & stunted growth; will not reach full potential
• turner syndrome, 45 X0; deficiency in HGH and estrogen result in stunted growth and lack of female qualities

Question 22

How does the environment affect bone

Answer 22

• Exposure to different stressors and strain modifies the shape, size and strength of bones
• These modifications follow mathematical laws

Question 23

Simplified Wolff’s Law

Answer 23

• Relates to exercise and the impact of movement on bone

Question 24

What are the effects of exercise on bone growth

Answer 24

• increased bone density