Lecture 4

Question 1

What is the function of bone?

Answer 1

1. hematopoiesis
2. lipid and mineral storage
3. support
4. protection

Question 2

What are the parts of the bone ECM?

Answer 2

1. The organic portion - type I collagen and non-collagenous proteins
2. The inorganic portion - mainly calcium phosphate in the form of hydroxyapatite crystals

Question 3

What are cells of bone tissue?

Answer 3

1. osteoprogenitor cells (osteogenic cells)
2. osteoblasts
3. osteocytes
4. osteoclasts
5. bone-lining cells

Question 4

Describe osteogenic cells?

Answer 4

spindle shaped connective tissue cells in the periosteum and endosteum that differentiate into osteoblasts

Question 5

Describe osteoblast cells?

Answer 5

Derived from the osteogenic cells (basophilic)

cytoplasmic processes contact them with other osteoblasts and osteocytes

well developed rER and golgi

Question 6

Describe osteocytes?

Answer 6

mature bone cells, derived from osteoblasts

housed in their own lacunae

maintain communication and exchange nutrients and metabolites via gap junctions between their narrow
cytoplasmic processes (filopodia) extending through the canaliculi

Question 7

Describe the osteoclasts?

Answer 7

multinucleated giant cells resulting from the fusion of the fusion of hematopoietic monocytes progenitor cells

Question 8

What are Howship’s lacunae?

Answer 8

Are depressions on the bone surface that house osteoclasts

Question 9

What are the tree distinct regions of the osteoclasts?

Answer 9

1. The ruffled border- sites of active bone resorption
2. the clear zone - region of cytoplasm that surrounds the ruffled border and helps isolate osteoclastic activity
3. the basal region - houses the organelles and nuclei

Question 10

Osteoclasts and bone resorption?

Answer 10

Lysosomal enzymes (from Golgi complex) and hydrogen ions released into the confined space between bone matrix and the osteoclast’s peripheral clear zone

Decalcified bone matrix is then broken down by acid
hydrolases, collagenous and proteolytic enzymes
and the cell resorbs the organic and inorganic material

Question 11

Bone lining cells?

Answer 11

Covering the external and internal surfaces of bone

Osteoblast derived flat cells with little cytoplasm and scant organelles

Found on the outer (periosteal cells) and inner (endosteal cells) surface of non-remodeling bone

Function in maintenance and nutritional support of
underlying cells

Regulate movement of phosphate and calcium into and out of bone

Question 12

What are the two layers of the periosteum?

Answer 12

1. the outer fibrous layer - consists mostly of a dense
   irregular connective tissue with fibroblasts. Contains blood vessels and nociceptors
2. inner cellular layer - contains osteoprogenitor cells and their derivatives (periosteal cells)

Question 13

What is the endosteum?

Answer 13

lines any space or cavity in bone

contains osteoclasts

contains mesenchymal cells which can differentiate into different cell types

Question 14

Bone growth and remodeling?

Answer 14

The elongation of bones is the result of interstitial growth of cartilage at the epiphyseal growth plate

Remodeling of bone is a coordinated action between
osteoblasts and osteoclasts

Question 15

What are the classifications of bone?

Answer 15

1. immature bone

2. mature bone

Question 16

What are some characteristics of immature bone?

Answer 16

1. non-lamellar and no haversian systems
2. random collagen fiber arrangement
3. high osteocyte
4. low mineral content
5. seen in newborns

Question 17

What are some characteristics of mature bone?

Answer 17

1. lamellar and has haversian systems
2. parallel and stress oriented (organized)
3. few osteocytes
4. high mineral content
5. develops from 1-month post natal

Question 18

What are the types of secondary (mature bone)

Answer 18

1. compact bone (dense and heavy)

2. spongy bone- filled with spaces that are interconnected

Question 19

What is the functional unit of compact bone?

Answer 19

The haversian system or osteon

Have numerous canaliculi that permit communication
between lacunae and with the Haversian canals

Question 20

What are the volkmann canals?

Answer 20

Connect adjacent Haversian canals to each other and to endosteum at the marrow cavity on the inside and
periosteum on the outside

Allow for passage of neurovasculature through compact bone