Bone Tissue and microscopic structure

Question 1

How is the force distributed?

Answer 1

Collected from the cancellous bone from multiple directions (weaker when coming from one direction) - down the diaphysis - down to the distal epiphysis cancellous bone - spread across the articulate surface of the knee

Question 2

Osteoprogenitor

Answer 2

• Osteoprogenitor (mesenchymal cells), form daughter cells that turn into osteoblasts, found in the cellular layer of the periosteum and the endosteum (lines the medullary cavity)

Question 3

Osteoblasts

Answer 3

• Osteoblasts (precursor to osteocytes), secretes bone matrix called OSTEOID before hydroxyapatite is deposited to form calcified bone matrix and osteoblasts converted to osteocytes after being engulfed by bine matrix

Question 4

Osteocytes

Answer 4

Recycles proteins and minerals, signals to the bs and cs to maintain bone homeostasis to make or break bone when needed, secretes substance to dissolve bone matrix to release ions into bloodstream when needed and then later - rebuilds the bone

Question 5

Osteoclasts

Answer 5

Made by the stem cells that produces macrophages and monocytes, has 50+ nuclei

Question 6

How to make hydroxyapatite

Answer 6

Ca3(PO4)2 + Ca(OH)2 –> Ca10(-PO4)6(OH)2
Brinttle but strong, can resist compression but shatters if twisted or under tension, incorporates CaCO3

Question 7

How does bone change appearance?

Answer 7

In response to external stimuls by building muscle attatchement sites for attatchment for larger muscles

Can form new bone cells

Question 8

How many components of extracellular matrix does bone have?

Answer 8

TWO:
Organic i.e the collagen fibres (protein)
Inorganic i.e the Calcium salts (mineral)

Has strength and some flexibility

Question 9

Organic part

Answer 9

Protein called collagen, long fibres, surrounded by proteoglycans (protein substance), runs in overlapping strands through the inorganic stuff, when given tension, it resists it to prevent breakage

Question 10

Inorganic

Answer 10

Mostly Hydroxyapatite, Ca2+ and other minerals, allows our bones to take compressive force of the body

Question 11

How many types of cells?

Answer 11

4, make up 2% of bone weight, have equilibrium where there is bone destruction and creation

Question 12

Structure of compact bone

Answer 12

A cylindrical osteon running all the way through

Dense and hard looking, the periosteum is smooth looking, has foramina for blood vessels to run through

Circumferential lamallae at the edge of the bone + osteons

Question 13

Structure of cancellous bone

Answer 13

Has a network of trabeculae, struts of lamella bone i.e tree ring structures but thinner. Dont need central canals becasue nutrients can diffuse from marrow through the trabecullar bone to cells, has canaliculi on outer surface or trabecullar for diffusion?

Question 14

What do osteons do?

Answer 14

Provide nutrients and sugnals through the central canal, has sheets of bone around the central canal to form the lamallae, In the lamallae, red lacunae are found where 1 osteoctes are found. Canaliculi form the canals for nutrients

Question 15

Interstital lamallae

Question 16

Bone remodelling

Answer 16

Appositional growth - osteoblasts add bone matrix in lamallae to periosteal bone surface adding circumferential lamallae, osteoclasts remove bone from the medullary cavity

Bone density remains the same

Question 17

What affects bone homeostatsis?

Answer 17

Calcium intake, physical stresses to build bone density for muscle attatchement

Overtime, around 30 - 40s, osteopenia occurs i.e osteoclastic activity is more than osteoblastic. Need both bone density and collagen to avoid fractures

Have less salt, caffeine and alcohol

Question 18

Osteoporosis

Answer 18

Osteoporosis is when there is a significant difference

Question 19

Why are females more at risk of osteoporosis?

Answer 19

Because cellular activity is run by estrogen, and when we hit menopause, estrogen drops so osteoblastic activity decreases.