Structure & function of bone

Question 1

Name the different bone cells

Answer 1

Osteoblast - lays down bone matrix
Osteoclast - resorbs bine from monocyte/macrophage lineage
Osteocyte - maintains matrix
Osteoprogenitor cell - gives rise to osteoblast

Question 2

Describe the structure and function of connective tissue

Answer 2

Support tissue of the body
Comes from embryonic mesoderm
Contains 95% eco and 5% cells
Contains cells (fibroblasts, mast cells, macrophage), fibres and ECM

Question 3

What is ECM composed of

Answer 3

collagen and elastin
ground substance

Question 4

Describe the function of collagen

Answer 4

Forms aggregates with or without ECM
Provide tensile strength
Reduced tensile strength from collagen disorders cause tissue laxity, joint hyper mobility and susceptibility to injury e.g Elhers dances syndrome

Question 5

Where is type I collagen found

Answer 5

Bone, tendon and skin

Question 6

Where is type II collagen found

Answer 6

Hyaline and elastic cartilage

Question 7

Where is type III collagen found

Answer 7

reticular lamina of basement membrane

Question 8

Where is type IV collagen found

Answer 8

basal lamina

Question 9

Where is type V collagen found

Answer 9

amino and chorion in fetus

Question 10

Name the structure and function of bone

Answer 10

Has specialised connective tissue
For support and protection
Reservoir for calcium and phosphate in body for calcium homeostasis
Supports haematopoesis

Question 11

Describe the structure and function of woven bone

Answer 11

Immature
Haphazard fibre arrangement
Mechanically weak
For foetal development or fracture repair

Question 12

Describe the structure and function of lamellar bone

Answer 12

Remodlled woven bone
Regular parallel collagen
Strong

Question 13

Describe the structure and function of bone matrix

Answer 13

Made of 25% organic and 66% non-organic component . Rest is water
90% collagen
Contains osteocalcin and osteonectin

Question 14

Describe the structure and function of osteoblasts

Answer 14

Secretes organic bone matrix
Mediates mineralisation of osteoid
Cuboidal cell with rough endoplasmic reticulum and Golgi

Question 15

Describe the structure and function of mineralisation

Answer 15

Osteoblasts secrete collagen and matrix vesicles
Matrix vesicles contain enzyme and protein to control availability of calcium and phosphate
Has to increase to a level where hydroxyapatite is precipitated

Question 16

Describe the structure and function of osteocytes

Answer 16

Mature osteoblasts surrounded by mineralised matrix
Long cytoplasmic processes connecting to each other and osteoblasts
In lacunae surrounded by EBF to allow nutrient diffusion through bony channels

Question 17

Describe the structure and function of osteoclasts

Answer 17

Bone reabsorbing cell
Work with osteoblast to regulate bone turnover and remodelling
Forms howships lacuna
Has an actin clear zone and ruffled border

Question 18

Describe the relationship between osteoblasts and osteoclasts

Answer 18

1. Osteoblasts needed for osteoclast activation
2. PTH stimulates bone resorption by osteoclasts
3. Receptors for PTH located on osteoblasts
4. Osteoclast precursors have RANK receptors on cell membrane
5. Osteoblasts have RANKL on their cell membrane
6. PTH unregulated RANKL which binds to RANK and stimulates the differentiation of osteoclasts