Specialized Connective Tissue; Bone

Question 1

Which cartilage lacks a perichondrium?

Answer 1

Fibrocartilage

Question 2

What cells synthesize extracellular matrix?

Answer 2

Chondroblasts and chondrocytes

Question 3

What is the composition of the extracellular matrix of cartilage?

Answer 3

Proteoglycans
Hyaluronic acid
Glycoproteins (in small amounts)

Question 4

True or false: cartilage is vascular.

Answer 4

False; it’s avascular

Question 5

What 2 major factors maintain the firmness and flexibility of cartilage?

Answer 5

1. Electrostatic bonds between collagen fibers and glycosaminoglycan side chains of proteoglycans
2. Binding of water to glycosaminoglycans

Question 6

If cartilage is avascular, then how does it receive nutrients and oxygen if

a) it’s involved in joints
b) it’s not involved in joints

Answer 6

a) Via diffusion from adjacent capillaries and synovial fluid
b) Via diffusion; the perichondrium contains blood vessels and lymphatics

Question 7

From which embryonic germ layer is cartilage derived?

Answer 7

Mesoderm

Question 8

What are the 4 main areas of a long bone?

Answer 8

Diaphysis
Epiphysis
Metaphysis
Epiphyseal plate

Question 9

How do osteocytes communicate with each other?

Answer 9

Via processes that pass through canaliculi

Question 10

What is the microscopic difference between osteocytes and osteoblasts?

Answer 10

Osteoblasts contain more ER and greater basophilic staining than osteocytes

Question 11

What is osteomalacia?

Answer 11

Impaired mineralization

Question 12

State the difference between osteomalacia and rickets?

Answer 12

Osteomalacia is calcium deficiency in adults, while rickets is calcium deficiency in children. Hence, rickets affects how bones grow whereas osteomalacia affects already-formed bones.

Question 13

State the steps of intramembranous ossification.

Answer 13

1. group of mesenchymal cells differentiate into osteoblasts
2. osteoblasts produce bone matrix
3. bone matrix undergo calcification, forming ‘bone’ islands
4. these bone islands/primary ossification centers form cavities that fuse

NOTE; the part of the mesenchme that doesn’t get ossified gives rise to endostium and periostium

Question 14

Causes of osteomalacia/rickets include…

Answer 14

1. Vitamin D deficiency
2. calcium deficiency
3. excess production of parathyroid hormone which increases resorption activity of osteoclasts

Question 15

Explain the steps of fracture repair in bones.

Answer 15

When a bone is fractured, cells at the site die, the bone matrix is destroyed, and blood vessels form clots.

1. Macrophages engulf the mess.
2. The cleared area is now inhabited by intensely proliferating periosteum and endostium
3. Primary bone formed by intramembranous and endochondral ossification
4. Trabecula (rods or plates in spongy bone made of dense collagen that help resist bending) connect the fractured ends