Lecture 9: Bone Cont.

Question 1

Osteoblast shape

Answer 1

• Cuboidal to polygonal with basophilic cytoplasm

- Aggregate in a single layer

Question 2

Osteocytes

Answer 2

Mature bone cells enclosed in the bone matrix within lacunae

Question 3

Osteocytes maintain contact with adjacent osteocytes via

Answer 3

cytoplasmic branching processes (filopodia) that connect to each other via small tunnels or canaliculi

Question 4

How do osteocytes transfer nutritional needs to the next cell?

Answer 4

gap junction

Question 5

Are osteocytes capable of undergoing mitosis?

Answer 5

No, because they are mature cells

Question 6

How do osteocytes maintain the homeostasis of Ca?

Answer 6

Synthesize and to a lesser extent absorb matrix

Question 7

Osteoclasts

Answer 7

multinucleated cells closely related to macrophages

Question 8

Osteoclast cytoplasm (baso or acido)

Answer 8

acidophilic

Question 9

Osteoclasts - bone marrow origin (from moncytes), formed via

Answer 9

DNA replication without division of the cytoplasm

Question 10

Where are osteocytes observed?

Answer 10

In indentations (bays) called Howship’s lacunae, which are reabsorbed from bone surface

Question 11

Osteoclasts induce

Answer 11

osteolysis to maintain Ca homeostasis and to remodel in response to growth or changing mechanical stress

Question 12

When activated and in contact with a bony surface, osteoclasts

Answer 12

release acid and lysosomal enzymes to decalcify bone

Question 13

Circumferential zone of osteoclast

Answer 13

Integrins tightly bind the matrix and surround a ruffled border of the cytoplasmic projections close to the matrix

Question 14

(Osteoclast) The sealed space between the cell and the matrix is acidified by

Answer 14

A proton pump localized in the osteoclast membrane and receives hydrolytic enzymes secreted by the cell

Question 15

Two ways of bone formation in fetal life

Answer 15

• Intramembrous ossification

- Endochondrial ossification

Question 16

Intramembrous ossification

Answer 16

• Occurs within membranes of condensed primitive mesenchymal tissue
• Flat bones of the skull

Question 17

Endochondrial ossification

Answer 17

• Bone develops from cartilaginous model (hyaline cartilage) that is subsequently replaced by osseous tissue at the ossification centers
• Occurs in the majority of bones of the skeleton.

Question 18

Where does endochondrial ossification occur

Answer 18

Ossification centers of immature bones and in the growth plates (epiphyseal plates) of developing bones

Question 19

Once growth plates are closed (mature animal),

Answer 19

no further longitudinal bone growth can occur

Question 20

Two types of bone based on degree of maturity

Answer 20

Woven bone

Lamellar bone

Question 21

Woven bone

Answer 21

• Immature bone present during fetal development and in the early stages of bone repair.
• Collagen fibers in woven bone are randomly arranged adopting a crisscross (woven pattern) microscopically

Question 22

Lamellar bone

Answer 22

• Mature bone
• Collagen fibers are arranged in a parallel pattern
• Composed of successive concentric layers of bone (in laminar formation) around a central canal containing blood vessels and nerves

Question 23

Osteons

Answer 23

functional unit of mature bone

Question 24

5 factors that influence bone formation and resorption

Answer 24

• Parathyroid hormone (can increase recruitment and activity of osteoclasts)
• Vitamin D deficiency (May lead to bone disease)
• Hormones (Estrogen inhibits bone resorption)
• Mechanical constraints
• Genetic background

Question 25

Synovium

Answer 25

The joint cavity between two movable ones

Question 26

Bone surfaces of the synovium are covered by

Answer 26

articular cartilage

Question 27

Synovial joints consists of

Answer 27

A joint capsule composed of fibrous portion and a well vascularized synovial membrane

Question 28

The articular capsule inner part

Answer 28

• Called the synovial membrane
• Lines fibrous capsule of the joints
• A thin sheet of connective tissue, with abundant blood vessels and lymphatics

Question 29

The surface facing the joint cavity is lined by epithelioid cells which

Answer 29

secrete hyaluronic acid and phagocytize debris

Question 30

Synovial cells have epithelioid morphology but are

Answer 30

specialized connective tissue cells, not epithelial since they don’t sit on a basement membrane or have intercellular junctions

Question 31

Synovial fluid

Answer 31

• Hyaluronic acid and a dialysate of plasma from the blood vessels
• Viscous substance that lubricates the joints

Question 32

Synovial membranes have variable _____ and may be arranged into ____ that project into the joint cavity

Answer 32

thickness

folds

Question 33

Where can synovial fluid be found

Answer 33

Synovial joints such as stifle, elbow, hip joint, ect

Question 34

Synovial fluid is secreted into joint cavity by

Answer 34

synovial cells

Question 35

Normal synovial fluid is

Answer 35

clear, translucent, very viscous lubricant

Question 36

Three functions of synovial fluid

Answer 36

Nutrition
Lubrication
Protection of articular surfaces