bone

Question 1

2 types of bone

Answer 1

cortical and cancellous

Question 2

cortical bone

Answer 2

○ 80% of skeleton mass
○ Hard exterior of bone
○ Packed osteons or haversian systems

Question 3

• Cancellous

Answer 3

(trabecular/spongy)
○ Boney struts organised into a loose network
○ Forms internal bone tissue, porous - contains marrow

Question 4

• Woven bone

Answer 4

○ When bone is initially formed (primary bone) has random collagen weave, mechanically weak (fetal bone development, repaired fractures)

Question 5

• Lamellar bone

Answer 5

○ Is secondary bone created by remodelling of woven bone

○ Has a regular parallel alignment of collagen into sheets (lamellae) and is mechanically strong

Question 6

• Senescence

Answer 6

○ Resorption exceeds formation

○ Skeletal mass decreases

Question 7

• Osteoprogenitor cells

Answer 7

○ Stem cells

Question 8

osteoprogenitor cells located in

Answer 8

§ Located in inner cellular layer of periosteum, endosteum and lining of osteonic canals

Question 9

• Osteoblasts

Answer 9

○ Form bone
○ Derived from osteoprogenitor cells
○ Synthesize organic components of bone matrix
○ Located on surface of bone tissue

Question 10

• Bone formation

Answer 10

○ Active osteoblasts produce and secrete collagen
○ Collagen fibrils form osteoid (organic matrix)
○ This then becomes mineralized - ossification

Question 11

• Osteocytes

Answer 11

○ Mature bone cells

Question 12

osteocytes differentiate from

Answer 12

§ Differentiate from osteoblasts.

Question 13

osteocytes reside in

Answer 13

§ Reside within lacunae, canaliculi contain ECF carrying nutrients to nourish the osteocytes

Question 14

• Osteoclasts

Answer 14

○ Degrade/resorb bone
○ Large, motile, multinucleated, bone resorbing cells
○ Haematopoietic origin

Question 15

resorption

Answer 15

□ osteoclasts Adhere tightyl to established bone matrix

□ Seceret bone degrading chemicals (HCl) and enzymes - collagenase

Question 16

collagenase

Answer 16

bone degrading enzyme

Question 17

bone recycling

Answer 17

□ Degraded mineral and organic components and endocytosed by the osteoclast
□ Delivered to nearly capillaries to the enter the circulation

Question 18

• Intramembranous ossification

Answer 18

○ Bone development from fibrous membranes

Question 19

• Endochondral ossification

Answer 19

○ Bone development from hyaline cartilage

Question 20

• Intramembranous ossification examples

Answer 20

• Formation of flat bones of the skull, the mandible, and the clavicles

Question 21

• Intramembranous ossification process

Answer 21

1. Condensation of mesenchymal cells to form a bone template membrane
   2. Differentiation into osteoblasts at the ossification centre
   3. Osteoblasts secrete the extracellular matrix and deposit calcium - oseoid
   4. Vascularization of the mesenchyme
   5. The spongy bone is remodelled into a thin layer of compact bone on the surface of the spongy bone

Question 22

endochondral ossification

Answer 22

• All of the bones of the body, except for the flat bones

Question 23

endochondral ossification process

Answer 23

○ In long bones, chondrocytes form a template of hyaline cartilage
○ Blood vessels invade the cavities
○ Osteocytes calcify the osteoclasts modify the calcified matrix into spongy bone
○ Osteoclasts create a marrow/medullary cavity
○ Secondary ossification centres form int ehh epiphyses
○ Hyaline cartilage persists until adolescence at the epiphyseal plate that is responsible for the length growth of long bones

Question 24

3 phases of remodelling

Answer 24

1. Activation
   - Osteoclasts recruited
   2. Resorption of bone
   - Osteoclast degrade bone, until reversal
   3. Formation of bone
   i. OB activation and mineralisation

Question 25

• Serum Ca levels

Answer 25

○ Tightly regulated

Question 26

○ Hypercalcaemia

Answer 26

§ Confusion, depression, weakness, kidney stones and abnormal heart rhythm including cardiac arrest
§ Depresses neuromuscular activity

Question 27

○ Hypocalcaemia

Answer 27

§ Impaired clotting, muscle spasms, seizures, confusion, or cardiac arrest
§ Potentiates neuromuscular activity

Question 28

Factors regulating plasma Ca

Answer 28

• Regulated by calcium sensing cells that release calciotropic hormones

Question 29

three calico hormones

Answer 29

PTH
Calcitriol
calcitonin

Question 30

1. PTH

Answer 30

• From parathyroid gland

Question 31

2. Calcitriol

Answer 31

i. From kidney

Question 32

3. Calcitonin

Answer 32

• From thyroid

Question 33

• Too much calcium in bood

Answer 33

○ Release calcitonin hormone

Question 34

• Not enough calcium in blood

Answer 34

○ Release parathyroid hormone