L1 Bone Structure

Question 1

what are the 3 primary functions of bone?

Answer 1

1. provide support where rigidity is needed eg// levers for locomotion, protection
2. houses haemopoietic tissue
3. calcium homeostasis

Question 2

what are the 3 classifications of bones? give examples

Answer 2

1. long bones - limbs eg/ femur
2. flat bones - skull
3. short bones - vertebrae

Question 3

fill in the blanks; ALL bones are comprised of _______ bone and _______ bone

Answer 3

a) cortical bone

b) trabecular bone

Question 4

describe cortical bone

Answer 4

dense compact bone

Question 5

describe trabecular bone

Answer 5

cancellous, porous network for marrow

Question 6

what is the periosteum?

Answer 6

connective tissue covering the outer surface of bone EXCEPT at articular surfaces

Question 7

what is the endosteum?

Answer 7

all surfaces within the bone

Question 8

describe the regions of long bones incl. what kind of bone is found within the region

Answer 8

epiphysis; each end of bone - trabecular bone, + thin shell of cortical bone
metaphysis; b/w diaphysis and epiphysis - transition frmo mostly cortical to mostly trabecular
diaphysis; shaft region - cortical bone only

Question 9

what are the three arteries supplying the bone?

Answer 9

nutrient artery
metaphysical arteries
epiphyseal arteries

Question 10

where does the nutrient artery enter the bone?

Answer 10

through the nutrient foramen in the SHAFT

Question 11

the epiphyseal and metaphyseal vessels anastomose in a mature lamellar bone, why do they not in an immature woven bone?

Answer 11

obstruction by cartilage growth plate

Question 12

where do venues in the cortical bone drain to?

Answer 12

periosteum

Question 13

bone tissue is composed of?

Answer 13

cells and mineralised extra-cellular matrix

Question 14

what does the bone matrix contain?

Answer 14

1. type I collagen
2. glycoproteins - bind calcium
3. hydroxyapatite

Question 15

how is the collagen within the bone matrix organised in lamellar vs woven bone?

Answer 15

lamellar = organised in layers
woven = disorganised

Question 16

LIST the bone cells

Answer 16

1. osteoblasts
2. osteoclasts
   3.osteocytes
3. bone lining cells
   + blood vessels; endothelium & bone marrow; haemopoietic + adipose cells

Question 17

what is an osteoblast? what does it secrete?

Answer 17

• cuboidal bone forming cell on tissue surface, secrete OSTEOID = mineralised

Question 18

what is an osteocyte? where do they sit within the bone and what is their function?

Answer 18

• mature osteoblast, found in lacunae surrounding been matrix they secreted
• fine processes extending into canaliculi, forming tight junctions w/ other osteoblasts and -cytes.
• function in detecting mechanical strain

Question 19

what is a bone lining cell?

Answer 19

flat cell, capable of diff into osteoblast on surface

Question 20

what is an osteoclast? what is there function? are they present in large numbers?

Answer 20

• large multinucleate cell
• sparsely scattered// not many
• secrete H+ and lysosomal enzymes = DEGRADE bone matrix

Question 21

how is cortical bone organised?

Answer 21

• into harvesian systems (osteons)

Question 22

what are harvesian systems? how are they linked?

Answer 22

• longitudinal cylinders consisting of concentric bone lamellae surrounding central blood vessels
• linked to each other by transverse volkman’s canals

Question 23

what are osteoblasts, bone lining cells and osteocytes derived from?

Answer 23

mesenchymal stem cells

Question 24

what happens to an osteoblast once it has stopped secreting osteoid?

Answer 24

• differentiates into osteocytes or bone lining cells
  OR
• apoptosis

Question 25

what are osteoclasts derived from?

Answer 25

monocyte/macrophage lineage, originally form mononucleate and fuse to form multinuclear

Question 26

what are the two categories of bone development?

Answer 26

1. intramembranous ossification

2. endochondral ossification

Question 27

what kind of bones form via intramembranous ossification?

Answer 27

flat bones ie/ skull bones

Question 28

how does bone form via intramembranous ossification?

Answer 28

condensation of embryonic mesenchyme –> differentiation to osteoblast –> secretion osteoid