Lecture 4

Question 1

What is the function of bone cells?

Answer 1

They respond to external forces, change shape, remodel, and repair themselves.

Question 2

What are the two extracellular components of bone?

Answer 2

Organic (33%) and inorganic (67%).

Question 3

What makes up the organic component of bone?

Answer 3

Collagen and ground substance (proteoglycans); it resists tension.

Question 4

What makes up the inorganic component of bone?

Answer 4

Hydroxyapatite and other calcium minerals; it makes bone hard and resistant to compression.

Question 5

What percentage of a bone’s weight is cellular, and what are the types of cells involved?

Answer 5

2%; includes Osteogenic cells, Osteoblasts, Osteocytes, and Osteoclasts.

Question 6

What is the role of Osteogenic cells?

Answer 6

They are stem cells that produce osteoblasts.

Question 7

What is the role of Osteoblasts?

Answer 7

They produce new bone matrix.

Question 8

What is the role of Osteocytes?

Answer 8

They recycle protein and minerals from the matrix.

Question 9

What is the role of Osteoclasts?

Answer 9

They remove bone matrix.

Question 10

What is the difference in structure between compact and cancellous bone?

Answer 10

Compact bone has an osteon structure; cancellous bone has a trabecular structure.

Question 11

Describe the structure of compact bone.

Answer 11

Dense outer surfaces (periosteum), visible foramina for blood supply, made up of osteons with circumferential lamellae.

Question 12

Describe the structure of cancellous bone.

Answer 12

Contains trabeculae (struts of lamella bone), marrow in cavities, and osteocytes in lacunae or on the surface.

Question 13

What is the function of trabeculae in cancellous bone?

Answer 13

Resist force from multiple directions and spread force distally.

Question 14

What is an osteon, and what is its function?

Answer 14

A lengthwise unit in compact bone; provides a pathway for nutrients to cells in the ECM.

Question 15

What are the components of an osteon?

Answer 15

Central canal (with blood vessels and nerves), lamellae (cylinders of ECM), lacunae (for osteocytes), and canaliculi (channels for osteocytes).

Question 16

How is bone homeostasis maintained?

Answer 16

Balance between Osteoblast and Osteoclast activity, allowing constant bone formation and destruction.

Question 17

What happens during bone remodelling?

Answer 17

Osteoblasts add bone matrix to the surface, and osteoclasts remove bone from the medullary cavity.

Question 18

What is required to maintain bone homeostasis?

Answer 18

Adequate dietary calcium and moderate exercise.

Question 19

What causes Osteoporosis?

Answer 19

More Osteoclast activity than Osteoblast activity, leading to a loss of cortical bone and thinning of trabeculae.

Question 20

Who is more likely to develop Osteoporosis and why?

Answer 20

Biological females, especially postmenopausal, due to a loss of oestrogen and lifestyle factors (lack of exercise, poor nutrition, alcohol, smoking).

Question 21

Describe the microscopic structure of bones.

Answer 21

Compact bone has osteons with central canals, lamellae, lacunae, and canaliculi; cancellous bone has trabeculae with marrow and osteocytes.

Question 22

How does bone maintain homeostasis?

Answer 22

By balancing Osteoblast and Osteoclast activity to regulate bone formation and destruction.

Question 23

Describe a bone pathology related to lack of homeostasis.

Answer 23

Osteoporosis, caused by more Osteoclast activity than Osteoblast activity, leading to thinning trabeculae and increased fracture risk.